R2DBC javadoc and code style revision

See gh-25065

spring-r2dbc/src/main/java/org/springframework/r2dbc/connection/ConnectionFactoryUtils.java

@@ -29,8 +29,6 @@ import io.r2dbc.spi.R2dbcTimeoutException;
 import io.r2dbc.spi.R2dbcTransientException;
 import io.r2dbc.spi.R2dbcTransientResourceException;
 import io.r2dbc.spi.Wrapped;
-import org.apache.commons.logging.Log;
-import org.apache.commons.logging.LogFactory;
 import reactor.core.publisher.Mono;
 
 import org.springframework.core.Ordered;
@@ -69,11 +67,6 @@ public abstract class ConnectionFactoryUtils {
 	 */
 	public static final int CONNECTION_SYNCHRONIZATION_ORDER = 1000;
 
-	private static final Log logger = LogFactory.getLog(ConnectionFactoryUtils.class);
-
-
-	private ConnectionFactoryUtils() {}
-
 
 	/**
 	 * Obtain a {@link Connection} from the given {@link ConnectionFactory}.
@@ -112,48 +105,34 @@ public abstract class ConnectionFactoryUtils {
 			if (conHolder != null && (conHolder.hasConnection() || conHolder.isSynchronizedWithTransaction())) {
 				conHolder.requested();
 				if (!conHolder.hasConnection()) {
-
-					if (logger.isDebugEnabled()) {
-						logger.debug("Fetching resumed R2DBC Connection from ConnectionFactory");
-					}
 					return fetchConnection(connectionFactory).doOnNext(conHolder::setConnection);
 				}
 				return Mono.just(conHolder.getConnection());
 			}
 			// Else we either got no holder or an empty thread-bound holder here.
 
-			if (logger.isDebugEnabled()) {
-				logger.debug("Fetching R2DBC Connection from ConnectionFactory");
-			}
-
 			Mono<Connection> con = fetchConnection(connectionFactory);
-
 			if (synchronizationManager.isSynchronizationActive()) {
-
+				return con.flatMap(connection -> Mono.just(connection).doOnNext(conn -> {
-				return con.flatMap(connection -> {
+					// Use same Connection for further R2DBC actions within the transaction.
-					return Mono.just(connection).doOnNext(conn -> {
+					// Thread-bound object will get removed by synchronization at transaction completion.
-
+					ConnectionHolder holderToUse = conHolder;
-						// Use same Connection for further R2DBC actions within the transaction.
+					if (holderToUse == null) {
-						// Thread-bound object will get removed by synchronization at transaction completion.
+						holderToUse = new ConnectionHolder(conn);
-						ConnectionHolder holderToUse = conHolder;
+					}
-						if (holderToUse == null) {
+					else {
-							holderToUse = new ConnectionHolder(conn);
+						holderToUse.setConnection(conn);
-						}
+					}
-						else {
+					holderToUse.requested();
-							holderToUse.setConnection(conn);
+					synchronizationManager
-						}
+							.registerSynchronization(new ConnectionSynchronization(holderToUse, connectionFactory));
-						holderToUse.requested();
+					holderToUse.setSynchronizedWithTransaction(true);
-						synchronizationManager
+					if (holderToUse != conHolder) {
-								.registerSynchronization(new ConnectionSynchronization(holderToUse, connectionFactory));
+						synchronizationManager.bindResource(connectionFactory, holderToUse);
-						holderToUse.setSynchronizedWithTransaction(true);
+					}
-						if (holderToUse != conHolder) {
+				})      // Unexpected exception from external delegation call -> close Connection and rethrow.
-							synchronizationManager.bindResource(connectionFactory, holderToUse);
+				.onErrorResume(e -> releaseConnection(connection, connectionFactory).then(Mono.error(e))));
-						}
-					})      // Unexpected exception from external delegation call -> close Connection and rethrow.
-					.onErrorResume(e -> releaseConnection(connection, connectionFactory).then(Mono.error(e)));
-				});
 			}
-
 			return con;
 		}).onErrorResume(NoTransactionException.class, e -> Mono.from(connectionFactory.create()));
 	}
@@ -356,9 +335,7 @@ public abstract class ConnectionFactoryUtils {
 		@Override
 		public Mono<Void> suspend() {
 			if (this.holderActive) {
-				return TransactionSynchronizationManager.forCurrentTransaction()
+				return TransactionSynchronizationManager.forCurrentTransaction().flatMap(synchronizationManager -> {
-						.flatMap(synchronizationManager -> {
-
 					synchronizationManager.unbindResource(this.connectionFactory);
 					if (this.connectionHolder.hasConnection() && !this.connectionHolder.isOpen()) {
 						// Release Connection on suspend if the application doesn't keep
@@ -371,7 +348,6 @@ public abstract class ConnectionFactoryUtils {
 					return Mono.empty();
 				});
 			}
-
 			return Mono.empty();
 		}
 
@@ -388,11 +364,10 @@ public abstract class ConnectionFactoryUtils {
 
 		@Override
 		public Mono<Void> beforeCompletion() {
-			// Release Connection early if the holder is not open anymore
+			// Release Connection early if the holder is not open anymore (that is,
-			// (that is, not used by another resource
+			// not used by another resource that has its own cleanup via transaction
-			// that has its own cleanup via transaction synchronization),
+			// synchronization), to avoid issues with strict transaction implementations
-			// to avoid issues with strict transaction implementations that expect
+			// that expect the close call before transaction completion.
-			// the close call before transaction completion.
 			if (!this.connectionHolder.isOpen()) {
 				return TransactionSynchronizationManager.forCurrentTransaction().flatMap(synchronizationManager -> {
 					synchronizationManager.unbindResource(this.connectionFactory);
@@ -414,8 +389,7 @@ public abstract class ConnectionFactoryUtils {
 			if (this.holderActive) {
 				// The bound ConnectionHolder might not be available anymore,
 				// since afterCompletion might get called from a different thread.
-				return TransactionSynchronizationManager.forCurrentTransaction()
+				return TransactionSynchronizationManager.forCurrentTransaction().flatMap(synchronizationManager -> {
-						.flatMap(synchronizationManager -> {
 					synchronizationManager.unbindResourceIfPossible(this.connectionFactory);
 					this.holderActive = false;
 					if (this.connectionHolder.hasConnection()) {
@@ -426,7 +400,6 @@ public abstract class ConnectionFactoryUtils {
 					return Mono.empty();
 				});
 			}
-
 			this.connectionHolder.reset();
 			return Mono.empty();
 		}

spring-r2dbc/src/main/java/org/springframework/r2dbc/connection/init/ScriptUtils.java

@@ -107,8 +107,6 @@ public abstract class ScriptUtils {
 
 	private static final Log logger = LogFactory.getLog(ScriptUtils.class);
 
-	// utility constructor
-	private ScriptUtils() {}
 
 	/**
 	 * Split an SQL script into separate statements delimited by the provided
@@ -335,14 +333,11 @@ public abstract class ScriptUtils {
 
 		return DataBufferUtils.join(DataBufferUtils.read(resource.getResource(), dataBufferFactory, 8192))
 				.handle((it, sink) -> {
-
 					try (InputStream is = it.asInputStream()) {
-
+						InputStreamReader in = (resource.getCharset() != null ?
-						InputStreamReader in = resource.getCharset() != null ? new InputStreamReader(is, resource.getCharset())
+								new InputStreamReader(is, resource.getCharset()) : new InputStreamReader(is));
-								: new InputStreamReader(is);
 						LineNumberReader lnr = new LineNumberReader(in);
 						String script = readScript(lnr, commentPrefixes, separator, blockCommentEndDelimiter);
-
 						sink.next(script);
 						sink.complete();
 					}
@@ -548,9 +543,9 @@ public abstract class ScriptUtils {
 	 * @see org.springframework.r2dbc.connection.ConnectionFactoryUtils#releaseConnection
 	 */
 	public static Mono<Void> executeSqlScript(Connection connection, EncodedResource resource,
-			DataBufferFactory dataBufferFactory, boolean continueOnError, boolean ignoreFailedDrops, String commentPrefix,
+			DataBufferFactory dataBufferFactory, boolean continueOnError, boolean ignoreFailedDrops,
-			@Nullable String separator, String blockCommentStartDelimiter, String blockCommentEndDelimiter)
+			String commentPrefix, @Nullable String separator, String blockCommentStartDelimiter,
-			throws ScriptException {
+			String blockCommentEndDelimiter) throws ScriptException {
 
 		return executeSqlScript(connection, resource, dataBufferFactory, continueOnError,
 				ignoreFailedDrops, new String[] { commentPrefix }, separator,
@@ -587,10 +582,10 @@ public abstract class ScriptUtils {
 	 * @see org.springframework.r2dbc.connection.ConnectionFactoryUtils#getConnection
 	 * @see org.springframework.r2dbc.connection.ConnectionFactoryUtils#releaseConnection
 	 */
-	public static Mono<Void> executeSqlScript(Connection connection, EncodedResource resource, DataBufferFactory dataBufferFactory,
+	public static Mono<Void> executeSqlScript(Connection connection, EncodedResource resource,
-			boolean continueOnError,
+			DataBufferFactory dataBufferFactory, boolean continueOnError, boolean ignoreFailedDrops,
-			boolean ignoreFailedDrops, String[] commentPrefixes, @Nullable String separator,
+			String[] commentPrefixes, @Nullable String separator, String blockCommentStartDelimiter,
-			String blockCommentStartDelimiter, String blockCommentEndDelimiter) throws ScriptException {
+			String blockCommentEndDelimiter) throws ScriptException {
 
 		if (logger.isDebugEnabled()) {
 			logger.debug("Executing SQL script from " + resource);
@@ -622,17 +617,15 @@ public abstract class ScriptUtils {
 		});
 
 		if (logger.isDebugEnabled()) {
-
 			executeScript = executeScript.doOnComplete(() -> {
-
 				long elapsedTime = System.currentTimeMillis() - startTime;
 				logger.debug("Executed SQL script from " + resource + " in " + elapsedTime + " ms.");
 			});
 		}
 
 		return executeScript.onErrorMap(ex -> !(ex instanceof ScriptException),
-				ex -> new UncategorizedScriptException("Failed to execute database script from resource [" + resource + "]",
+				ex -> new UncategorizedScriptException(
-						ex))
+						"Failed to execute database script from resource [" + resource + "]", ex))
 				.then();
 	}
 
@@ -644,22 +637,21 @@ public abstract class ScriptUtils {
 				.collect(Collectors.summingLong(count -> count));
 
 		if (logger.isDebugEnabled()) {
-			execution = execution.doOnNext(rowsAffected -> logger.debug(rowsAffected + " returned as update count for SQL: " + statement));
+			execution = execution.doOnNext(rowsAffected ->
+					logger.debug(rowsAffected + " returned as update count for SQL: " + statement));
 		}
 
 		return execution.onErrorResume(ex -> {
-
 			boolean dropStatement = StringUtils.startsWithIgnoreCase(statement.trim(), "drop");
 			if (continueOnError || (dropStatement && ignoreFailedDrops)) {
 				if (logger.isDebugEnabled()) {
-					logger.debug(ScriptStatementFailedException.buildErrorMessage(statement, statementNumber.get(), resource),
+					logger.debug(ScriptStatementFailedException.buildErrorMessage(
-							ex);
+							statement, statementNumber.get(), resource), ex);
 				}
 			}
 			else {
 				return Mono.error(new ScriptStatementFailedException(statement, statementNumber.get(), resource, ex));
 			}
-
 			return Mono.empty();
 		}).then();
 	}

spring-r2dbc/src/main/java/org/springframework/r2dbc/connection/lookup/AbstractRoutingConnectionFactory.java

@@ -167,6 +167,7 @@ public abstract class AbstractRoutingConnectionFactory implements ConnectionFact
 	 */
 	protected ConnectionFactory resolveSpecifiedConnectionFactory(Object connectionFactory)
 			throws IllegalArgumentException {
+
 		if (connectionFactory instanceof ConnectionFactory) {
 			return (ConnectionFactory) connectionFactory;
 		}
@@ -174,17 +175,14 @@ public abstract class AbstractRoutingConnectionFactory implements ConnectionFact
 			return this.connectionFactoryLookup.getConnectionFactory((String) connectionFactory);
 		}
 		else {
-			throw new IllegalArgumentException(
+			throw new IllegalArgumentException("Illegal connection factory value - " +
-					"Illegal connection factory value - only 'io.r2dbc.spi.ConnectionFactory' and 'String' supported: "
+					"only 'io.r2dbc.spi.ConnectionFactory' and 'String' supported: " + connectionFactory);
-							+ connectionFactory);
 		}
 	}
 
 	@Override
 	public Mono<Connection> create() {
-		return determineTargetConnectionFactory() //
+		return determineTargetConnectionFactory().map(ConnectionFactory::create).flatMap(Mono::from);
-				.map(ConnectionFactory::create) //
-				.flatMap(Mono::from);
 	}
 
 	@Override

spring-r2dbc/src/main/java/org/springframework/r2dbc/connection/lookup/MapConnectionFactoryLookup.java

@@ -56,7 +56,6 @@ public class MapConnectionFactoryLookup implements ConnectionFactoryLookup {
 
 	/**
 	 * Create a new instance of the {@link MapConnectionFactoryLookup} class.
-	 *
 	 * @param connectionFactoryName the name under which the supplied {@link ConnectionFactory} is to be added
 	 * @param connectionFactory the {@link ConnectionFactory} to be added
 	 */

spring-r2dbc/src/main/java/org/springframework/r2dbc/core/BindParameterSource.java

@@ -46,7 +46,7 @@ interface BindParameterSource {
 	/**
 	 * Return the parameter value for the requested named parameter.
 	 * @param paramName the name of the parameter
-	 * @return the value of the specified parameter, can be {@code null}
+	 * @return the value of the specified parameter (can be {@code null})
 	 * @throws IllegalArgumentException if there is no value
 	 * for the requested parameter
 	 */
@@ -64,8 +64,8 @@ interface BindParameterSource {
 	}
 
 	/**
-	 * Return parameter names of the underlying parameter source.
+	 * Return the parameter names of the underlying parameter source.
-	 * @return parameter names of the underlying parameter source.
+	 * @return an iterator over the parameter names
 	 */
 	Iterable<String> getParameterNames();
 

spring-r2dbc/src/main/java/org/springframework/r2dbc/core/ColumnMapRowMapper.java

@@ -48,7 +48,7 @@ import org.springframework.util.LinkedCaseInsensitiveMap;
  */
 public class ColumnMapRowMapper implements BiFunction<Row, RowMetadata, Map<String, Object>> {
 
-	/** Default instance. */
+	/** A default {@code ColumnMapRowMapper} instance. */
 	public final static ColumnMapRowMapper INSTANCE = new ColumnMapRowMapper();
 
 

spring-r2dbc/src/main/java/org/springframework/r2dbc/core/DatabaseClient.java

@@ -66,7 +66,7 @@ public interface DatabaseClient extends ConnectionAccessor {
 	 * SQL call along with options leading to the execution. The SQL string can
 	 * contain either native parameter bind markers or named parameters (e.g.
 	 * {@literal :foo, :bar}) when {@link NamedParameterExpander} is enabled.
-	 * @param sql must not be {@code null} or empty
+	 * @param sql the SQL statement
 	 * @return a new {@link GenericExecuteSpec}
 	 * @see NamedParameterExpander
 	 * @see DatabaseClient.Builder#namedParameters(boolean)
@@ -80,7 +80,7 @@ public interface DatabaseClient extends ConnectionAccessor {
 	 * bind markers or named parameters (e.g. {@literal :foo, :bar}) when
 	 * {@link NamedParameterExpander} is enabled.
 	 * <p>Accepts {@link PreparedOperation} as SQL and binding {@link Supplier}
-	 * @param sqlSupplier must not be {@code null}
+	 * @param sqlSupplier a supplier for the SQL statement
 	 * @return a new {@link GenericExecuteSpec}
 	 * @see NamedParameterExpander
 	 * @see DatabaseClient.Builder#namedParameters(boolean)
@@ -115,34 +115,31 @@ public interface DatabaseClient extends ConnectionAccessor {
 
 		/**
 		 * Configure the {@link BindMarkersFactory BindMarkers} to be used.
-		 * @param bindMarkers must not be {@code null}
 		 */
 		Builder bindMarkers(BindMarkersFactory bindMarkers);
 
 		/**
 		 * Configure the {@link ConnectionFactory R2DBC connector}.
-		 * @param factory must not be {@code null}
 		 */
 		Builder connectionFactory(ConnectionFactory factory);
 
 		/**
 		 * Configure a {@link ExecuteFunction} to execute {@link Statement} objects.
-		 * @param executeFunction must not be {@code null}
 		 * @see Statement#execute()
 		 */
 		Builder executeFunction(ExecuteFunction executeFunction);
 
 		/**
-		 * Configure whether to use named parameter expansion. Defaults to {@code true}.
+		 * Configure whether to use named parameter expansion.
-		 * @param enabled {@code true} to use named parameter expansion.
+		 * Defaults to {@code true}.
-		 * {@code false} to disable named parameter expansion.
+		 * @param enabled {@code true} to use named parameter expansion;
+		 * {@code false} to disable named parameter expansion
 		 * @see NamedParameterExpander
 		 */
 		Builder namedParameters(boolean enabled);
 
 		/**
 		 * Configures a {@link Consumer} to configure this builder.
-		 * @param builderConsumer must not be {@code null}.
 		 */
 		Builder apply(Consumer<Builder> builderConsumer);
 
@@ -162,28 +159,28 @@ public interface DatabaseClient extends ConnectionAccessor {
 		 * Bind a non-{@code null} value to a parameter identified by its
 		 * {@code index}. {@code value} can be either a scalar value or {@link Parameter}.
 		 * @param index zero based index to bind the parameter to
-		 * @param value must not be {@code null}. Can be either a scalar value or {@link Parameter}
+		 * @param value either a scalar value or {@link Parameter}
 		 */
 		GenericExecuteSpec bind(int index, Object value);
 
 		/**
 		 * Bind a {@code null} value to a parameter identified by its {@code index}.
 		 * @param index zero based index to bind the parameter to
-		 * @param type must not be {@code null}
+		 * @param type the parameter type
 		 */
 		GenericExecuteSpec bindNull(int index, Class<?> type);
 
 		/**
 		 * Bind a non-{@code null} value to a parameter identified by its {@code name}.
-		 * @param name must not be {@code null} or empty
+		 * @param name the name of the parameter
-		 * @param value must not be {@code null}
+		 * @param value the value to bind
 		 */
 		GenericExecuteSpec bind(String name, Object value);
 
 		/**
 		 * Bind a {@code null} value to a parameter identified by its {@code name}.
-		 * @param name must not be {@code null} or empty
+		 * @param name the name of the parameter
-		 * @param type must not be {@code null}
+		 * @param type the parameter type
 		 */
 		GenericExecuteSpec bindNull(String name, Class<?> type);
 
@@ -195,11 +192,11 @@ public interface DatabaseClient extends ConnectionAccessor {
 		 * DatabaseClient client = …;
 		 * client.sql("SELECT book_id FROM book").filter(statement -> statement.fetchSize(100))
 		 * </pre>
-		 * @param filter the filter to be added to the chain
+		 * @param filterFunction the filter to be added to the chain
 		 */
-		default GenericExecuteSpec filter(Function<? super Statement, ? extends Statement> filter) {
+		default GenericExecuteSpec filter(Function<? super Statement, ? extends Statement> filterFunction) {
-			Assert.notNull(filter, "Statement FilterFunction must not be null");
+			Assert.notNull(filterFunction, "Filter function must not be null");
-			return filter((statement, next) -> next.execute(filter.apply(statement)));
+			return filter((statement, next) -> next.execute(filterFunction.apply(statement)));
 		}
 
 		/**
@@ -216,9 +213,9 @@ public interface DatabaseClient extends ConnectionAccessor {
 
 		/**
 		 * Configure a result mapping {@link Function function} and enter the execution stage.
-		 * @param mappingFunction must not be {@code null}
+		 * @param mappingFunction a function that maps from {@link Row} to the result type
-		 * @param <R> result type.
+		 * @param <R> the result type
-		 * @return a {@link FetchSpec} for configuration what to fetch. Guaranteed to be not {@code null}.
+		 * @return a {@link FetchSpec} for configuration what to fetch
 		 */
 		default <R> RowsFetchSpec<R> map(Function<Row, R> mappingFunction) {
 			Assert.notNull(mappingFunction, "Mapping function must not be null");
@@ -226,10 +223,11 @@ public interface DatabaseClient extends ConnectionAccessor {
 		}
 
 		/**
-		 * Configure a result mapping {@link BiFunction function}  and enter the execution stage.
+		 * Configure a result mapping {@link BiFunction function} and enter the execution stage.
-		 * @param mappingFunction must not be {@code null}
+		 * @param mappingFunction a function that maps from {@link Row} and {@link RowMetadata}
-		 * @param <R> result type.
+		 * to the result type
-		 * @return a {@link FetchSpec} for configuration what to fetch. Guaranteed to be not {@code null}.
+		 * @param <R> the result type
+		 * @return a {@link FetchSpec} for configuration what to fetch
 		 */
 		<R> RowsFetchSpec<R> map(BiFunction<Row, RowMetadata, R> mappingFunction);
 
@@ -239,8 +237,9 @@ public interface DatabaseClient extends ConnectionAccessor {
 		FetchSpec<Map<String, Object>> fetch();
 
 		/**
-		 * Perform the SQL call and return a {@link Mono} that completes without result on statement completion.
+		 * Perform the SQL call and return a {@link Mono} that completes without result
-		 * @return a {@link Mono} ignoring its payload (actively dropping).
+		 * on statement completion.
+		 * @return a {@link Mono} ignoring its payload (actively dropping)
 		 */
 		Mono<Void> then();
 	}

spring-r2dbc/src/main/java/org/springframework/r2dbc/core/DefaultDatabaseClient.java

@@ -104,17 +104,14 @@ class DefaultDatabaseClient implements DatabaseClient {
 	}
 
 	@Override
-	public <T> Mono<T> inConnection(Function<Connection, Mono<T>> action)
+	public <T> Mono<T> inConnection(Function<Connection, Mono<T>> action) throws DataAccessException {
-			throws DataAccessException {
 		Assert.notNull(action, "Callback object must not be null");
 		Mono<ConnectionCloseHolder> connectionMono = getConnection().map(
 				connection -> new ConnectionCloseHolder(connection, this::closeConnection));
 
 		return Mono.usingWhen(connectionMono, connectionCloseHolder -> {
-
 			// Create close-suppressing Connection proxy
 			Connection connectionToUse = createConnectionProxy(connectionCloseHolder.connection);
-
 					try {
 						return action.apply(connectionToUse);
 					}
@@ -129,18 +126,14 @@ class DefaultDatabaseClient implements DatabaseClient {
 	}
 
 	@Override
-	public <T> Flux<T> inConnectionMany(Function<Connection, Flux<T>> action)
+	public <T> Flux<T> inConnectionMany(Function<Connection, Flux<T>> action) throws DataAccessException {
-			throws DataAccessException {
 		Assert.notNull(action, "Callback object must not be null");
 		Mono<ConnectionCloseHolder> connectionMono = getConnection().map(
 				connection -> new ConnectionCloseHolder(connection, this::closeConnection));
 
 		return Flux.usingWhen(connectionMono, connectionCloseHolder -> {
-
+			// Create close-suppressing Connection proxy, also preparing returned Statements.
-			// Create close-suppressing Connection proxy, also preparing returned
-			// Statements.
 			Connection connectionToUse = createConnectionProxy(connectionCloseHolder.connection);
-
 					try {
 						return action.apply(connectionToUse);
 					}
@@ -237,7 +230,7 @@ class DefaultDatabaseClient implements DatabaseClient {
 			this.byIndex = Collections.emptyMap();
 			this.byName = Collections.emptyMap();
 			this.sqlSupplier = sqlSupplier;
-			this.filterFunction = StatementFilterFunctions.empty();
+			this.filterFunction = StatementFilterFunction.EMPTY_FILTER;
 		}
 
 		DefaultGenericExecuteSpec(Map<Integer, Parameter> byIndex, Map<String, Parameter> byName,
@@ -309,7 +302,8 @@ class DefaultDatabaseClient implements DatabaseClient {
 		@Override
 		public DefaultGenericExecuteSpec filter(StatementFilterFunction filter) {
 			Assert.notNull(filter, "Statement FilterFunction must not be null");
-			return new DefaultGenericExecuteSpec(this.byIndex, this.byName, this.sqlSupplier, this.filterFunction.andThen(filter));
+			return new DefaultGenericExecuteSpec(
+					this.byIndex, this.byName, this.sqlSupplier, this.filterFunction.andThen(filter));
 		}
 
 		@Override
@@ -458,7 +452,6 @@ class DefaultDatabaseClient implements DatabaseClient {
 			Assert.state(StringUtils.hasText(sql), "SQL returned by SQL supplier must not be empty!");
 			return sql;
 		}
-
 	}
 
 

spring-r2dbc/src/main/java/org/springframework/r2dbc/core/DefaultDatabaseClientBuilder.java

@@ -81,7 +81,6 @@ class DefaultDatabaseClientBuilder implements DatabaseClient.Builder {
 		Assert.notNull(this.connectionFactory, "ConnectionFactory must not be null");
 
 		BindMarkersFactory bindMarkers = this.bindMarkers;
-
 		if (bindMarkers == null) {
 			if (this.namedParameters) {
 				bindMarkers = BindMarkersFactoryResolver.resolve(this.connectionFactory);
@@ -91,13 +90,12 @@ class DefaultDatabaseClientBuilder implements DatabaseClient.Builder {
 			}
 		}
 
-		return new DefaultDatabaseClient(bindMarkers, this.connectionFactory,
+		return new DefaultDatabaseClient(
-				this.executeFunction, this.namedParameters);
+				bindMarkers, this.connectionFactory, this.executeFunction, this.namedParameters);
 	}
 
 	@Override
-	public DatabaseClient.Builder apply(
+	public DatabaseClient.Builder apply(Consumer<DatabaseClient.Builder> builderConsumer) {
-			Consumer<DatabaseClient.Builder> builderConsumer) {
 		Assert.notNull(builderConsumer, "BuilderConsumer must not be null");
 		builderConsumer.accept(this);
 		return this;

spring-r2dbc/src/main/java/org/springframework/r2dbc/core/DefaultFetchSpec.java

@@ -52,6 +52,7 @@ class DefaultFetchSpec<T> implements FetchSpec<T> {
 			Function<Connection, Flux<Result>> resultFunction,
 			Function<Connection, Mono<Integer>> updatedRowsFunction,
 			BiFunction<Row, RowMetadata, T> mappingFunction) {
+
 		this.sql = sql;
 		this.connectionAccessor = connectionAccessor;
 		this.resultFunction = resultFunction;
@@ -64,18 +65,14 @@ class DefaultFetchSpec<T> implements FetchSpec<T> {
 	public Mono<T> one() {
 		return all().buffer(2)
 				.flatMap(list -> {
-
 					if (list.isEmpty()) {
 						return Mono.empty();
 					}
-
 					if (list.size() > 1) {
 						return Mono.error(new IncorrectResultSizeDataAccessException(
-								String.format("Query [%s] returned non unique result.",
+								String.format("Query [%s] returned non unique result.", this.sql),
-										this.sql),
 								1));
 					}
-
 					return Mono.just(list.get(0));
 				}).next();
 	}

spring-r2dbc/src/main/java/org/springframework/r2dbc/core/ExecuteFunction.java

@@ -48,7 +48,7 @@ import org.reactivestreams.Publisher;
 public interface ExecuteFunction {
 
 	/**
-	 * Execute the given {@link Statement} for a stream of {@link Result}s.
+	 * Execute the given {@link Statement} for a stream of {@link Result} objects.
 	 * @param statement the request to execute
 	 * @return the delayed result stream
 	 */

spring-r2dbc/src/main/java/org/springframework/r2dbc/core/FetchSpec.java

@@ -25,4 +25,6 @@ package org.springframework.r2dbc.core;
  * @see RowsFetchSpec
  * @see UpdatedRowsFetchSpec
  */
-public interface FetchSpec<T> extends RowsFetchSpec<T>, UpdatedRowsFetchSpec {}
+public interface FetchSpec<T> extends RowsFetchSpec<T>, UpdatedRowsFetchSpec {
+
+}

spring-r2dbc/src/main/java/org/springframework/r2dbc/core/MapBindParameterSource.java

@@ -40,30 +40,23 @@ class MapBindParameterSource implements BindParameterSource {
 	 * Create a new empty {@link MapBindParameterSource}.
 	 */
 	MapBindParameterSource() {
-		this(new LinkedHashMap<>());
+		this.values = new LinkedHashMap<>();
 	}
 
 	/**
-	 * Creates a new {@link MapBindParameterSource} given {@link Map} of
+	 * Creates a new {@link MapBindParameterSource} given {@link Map} of {@link Parameter}.
-	 * {@link Parameter}.
+	 * @param values the parameter mapping
-	 *
-	 * @param values the parameter mapping.
 	 */
 	MapBindParameterSource(Map<String, Parameter> values) {
-
 		Assert.notNull(values, "Values must not be null");
-
 		this.values = values;
 	}
 
 
 	/**
-	 * Add a key-value pair to the {@link MapBindParameterSource}. The value must not be
+	 * Add a key-value pair to the {@link MapBindParameterSource}.
-	 * {@code null}.
+	 * @param paramName the name of the parameter
-	 *
+	 * @param value the parameter value to add (must not be {@code null})
-	 * @param paramName must not be {@code null}.
-	 * @param value must not be {@code null}.
-	 * @return {@code this} {@link MapBindParameterSource}
 	 */
 	MapBindParameterSource addValue(String paramName, Object value) {
 		Assert.notNull(paramName, "Parameter name must not be null");
@@ -91,8 +84,7 @@ class MapBindParameterSource implements BindParameterSource {
 	@Override
 	public Object getValue(String paramName) throws IllegalArgumentException {
 		if (!hasValue(paramName)) {
-			throw new IllegalArgumentException(
+			throw new IllegalArgumentException("No value registered for key '" + paramName + "'");
-					"No value registered for key '" + paramName + "'");
 		}
 		return this.values.get(paramName).getValue();
 	}

spring-r2dbc/src/main/java/org/springframework/r2dbc/core/NamedParameterUtils.java

@@ -87,10 +87,9 @@ abstract class NamedParameterUtils {
 
 	/**
 	 * Parse the SQL statement and locate any placeholders or named parameters.
-	 * Namedparameters are substituted for a R2DBC placeholder.
+	 * Named parameters are substituted for a R2DBC placeholder.
-	 *
 	 * @param sql the SQL statement
-	 * @return the parsed statement, represented as {@link ParsedSql} instance.
+	 * @return the parsed statement, represented as {@link ParsedSql} instance
 	 */
 	public static ParsedSql parseSqlStatement(String sql) {
 		Assert.notNull(sql, "SQL must not be null");
@@ -134,20 +133,22 @@ abstract class NamedParameterUtils {
 					while (statement[j] != '}') {
 						j++;
 						if (j >= statement.length) {
-							throw new InvalidDataAccessApiUsageException("Non-terminated named parameter declaration " +
+							throw new InvalidDataAccessApiUsageException(
-									"at position " + i + " in statement: " + sql);
+									"Non-terminated named parameter declaration at position " + i +
+									" in statement: " + sql);
 						}
 						if (statement[j] == ':' || statement[j] == '{') {
-							throw new InvalidDataAccessApiUsageException("Parameter name contains invalid character '" +
+							throw new InvalidDataAccessApiUsageException(
-									statement[j] + "' at position " + i + " in statement: " + sql);
+									"Parameter name contains invalid character '" + statement[j] +
+									"' at position " + i + " in statement: " + sql);
 						}
 					}
 					if (j - i > 2) {
 						parameter = sql.substring(i + 2, j);
-						namedParameterCount = addNewNamedParameter(namedParameters,
+						namedParameterCount = addNewNamedParameter(
-								namedParameterCount, parameter);
+								namedParameters, namedParameterCount, parameter);
-						totalParameterCount = addNamedParameter(parameterList,
+						totalParameterCount = addNamedParameter(
-								totalParameterCount, escapes, i, j + 1, parameter);
+								parameterList, totalParameterCount, escapes, i, j + 1, parameter);
 					}
 					j++;
 				}
@@ -157,10 +158,10 @@ abstract class NamedParameterUtils {
 					}
 					if (j - i > 1) {
 						parameter = sql.substring(i + 1, j);
-						namedParameterCount = addNewNamedParameter(namedParameters,
+						namedParameterCount = addNewNamedParameter(
-								namedParameterCount, parameter);
+								namedParameters, namedParameterCount, parameter);
-						totalParameterCount = addNamedParameter(parameterList,
+						totalParameterCount = addNamedParameter(
-								totalParameterCount, escapes, i, j, parameter);
+								parameterList, totalParameterCount, escapes, i, j, parameter);
 					}
 				}
 				i = j - 1;
@@ -190,8 +191,8 @@ abstract class NamedParameterUtils {
 		return parsedSql;
 	}
 
-	private static int addNamedParameter(
+	private static int addNamedParameter(List<ParameterHolder> parameterList,
-			List<ParameterHolder> parameterList, int totalParameterCount, int escapes, int i, int j, String parameter) {
+			int totalParameterCount, int escapes, int i, int j, String parameter) {
 
 		parameterList.add(new ParameterHolder(parameter, i - escapes, j - escapes));
 		totalParameterCount++;
@@ -256,10 +257,9 @@ abstract class NamedParameterUtils {
 	/**
 	 * Parse the SQL statement and locate any placeholders or named parameters. Named
 	 * parameters are substituted for a R2DBC placeholder, and any select list is expanded
-	 * to the required number of placeholders. Select lists may contain an array of
+	 * to the required number of placeholders. Select lists may contain an array of objects,
-	 * objects, and in that case the placeholders will be grouped and enclosed with
+	 * and in that case the placeholders will be grouped and enclosed with parentheses.
-	 * parentheses. This allows for the use of "expression lists" in the SQL statement
+	 * This allows for the use of "expression lists" in the SQL statement like:
-	 * like: <br /><br />
 	 * {@code select id, name, state from table where (name, age) in (('John', 35), ('Ann', 50))}
 	 * <p>The parameter values passed in are used to determine the number of placeholders to
 	 * be used for a select list. Select lists should be limited to 100 or fewer elements.
@@ -269,17 +269,19 @@ abstract class NamedParameterUtils {
 	 * @param bindMarkersFactory the bind marker factory.
 	 * @param paramSource the source for named parameters
 	 * @return the expanded query that accepts bind parameters and allows for execution
-	 *         without further translation
+	 * without further translation
 	 * @see #parseSqlStatement
 	 */
 	public static PreparedOperation<String> substituteNamedParameters(ParsedSql parsedSql,
 			BindMarkersFactory bindMarkersFactory, BindParameterSource paramSource) {
+
 		NamedParameters markerHolder = new NamedParameters(bindMarkersFactory);
 		String originalSql = parsedSql.getOriginalSql();
 		List<String> paramNames = parsedSql.getParameterNames();
 		if (paramNames.isEmpty()) {
 			return new ExpandedQuery(originalSql, markerHolder, paramSource);
 		}
+
 		StringBuilder actualSql = new StringBuilder(originalSql.length());
 		int lastIndex = 0;
 		for (int i = 0; i < paramNames.size(); i++) {
@@ -318,7 +320,6 @@ abstract class NamedParameterUtils {
 							actualSql.append(marker.getPlaceholder(counter));
 							counter++;
 						}
-
 					}
 				}
 				else {
@@ -343,6 +344,7 @@ abstract class NamedParameterUtils {
 		return (c < 128 && separatorIndex[c]) || Character.isWhitespace(c);
 	}
 
+
 	// -------------------------------------------------------------------------
 	// Convenience methods operating on a plain SQL String
 	// -------------------------------------------------------------------------
@@ -359,6 +361,7 @@ abstract class NamedParameterUtils {
 	 */
 	public static PreparedOperation<String> substituteNamedParameters(String sql,
 			BindMarkersFactory bindMarkersFactory, BindParameterSource paramSource) {
+
 		ParsedSql parsedSql = parseSqlStatement(sql);
 		return substituteNamedParameters(parsedSql, bindMarkersFactory, paramSource);
 	}
@@ -407,9 +410,9 @@ abstract class NamedParameterUtils {
 		public int hashCode() {
 			return Objects.hash(this.parameterName, this.startIndex, this.endIndex);
 		}
-
 	}
 
+
 	/**
 	 * Holder for bind markers progress.
 	 */
@@ -426,7 +429,6 @@ abstract class NamedParameterUtils {
 			this.identifiable = factory.identifiablePlaceholders();
 		}
 
-
 		/**
 		 * Get the {@link NamedParameter} identified by {@code namedParameter}.
 		 * Parameter objects get created if they do not yet exist.
@@ -434,20 +436,16 @@ abstract class NamedParameterUtils {
 		 * @return the named parameter
 		 */
 		NamedParameter getOrCreate(String namedParameter) {
-
 			List<NamedParameter> reference = this.references.computeIfAbsent(
-					namedParameter, ignore -> new ArrayList<>());
+					namedParameter, key -> new ArrayList<>());
-
 			if (reference.isEmpty()) {
 				NamedParameter param = new NamedParameter(namedParameter);
 				reference.add(param);
 				return param;
 			}
-
 			if (this.identifiable) {
 				return reference.get(0);
 			}
-
 			NamedParameter param = new NamedParameter(namedParameter);
 			reference.add(param);
 			return param;
@@ -458,13 +456,13 @@ abstract class NamedParameterUtils {
 			return this.references.get(name);
 		}
 
+
 		class NamedParameter {
 
 			private final String namedParameter;
 
 			private final List<BindMarker> placeholders = new ArrayList<>();
 
-
 			NamedParameter(String namedParameter) {
 				this.namedParameter = namedParameter;
 			}
@@ -475,9 +473,7 @@ abstract class NamedParameterUtils {
 			 * @return the placeholder to be used in the SQL statement
 			 */
 			String addPlaceholder() {
-
+				BindMarker bindMarker = NamedParameters.this.bindMarkers.next(this.namedParameter);
-				BindMarker bindMarker = NamedParameters.this.bindMarkers.next(
-						this.namedParameter);
 				this.placeholders.add(bindMarker);
 				return bindMarker.getPlaceholder();
 			}
@@ -487,17 +483,15 @@ abstract class NamedParameterUtils {
 			}
 
 			String getPlaceholder(int counter) {
-
 				while (counter + 1 > this.placeholders.size()) {
 					addPlaceholder();
 				}
-
 				return this.placeholders.get(counter).getPlaceholder();
 			}
 		}
-
 	}
 
+
 	/**
 	 * Expanded query that allows binding of parameters using parameter names that were
 	 * used to expand the query. Binding unrolls {@link Collection}s and nested arrays.
@@ -510,35 +504,25 @@ abstract class NamedParameterUtils {
 
 		private final BindParameterSource parameterSource;
 
-
+		ExpandedQuery(String expandedSql, NamedParameters parameters, BindParameterSource parameterSource) {
-		ExpandedQuery(String expandedSql, NamedParameters parameters,
-				BindParameterSource parameterSource) {
 			this.expandedSql = expandedSql;
 			this.parameters = parameters;
 			this.parameterSource = parameterSource;
 		}
 
-
 		@SuppressWarnings("unchecked")
 		public void bind(BindTarget target, String identifier, Object value) {
-
 			List<BindMarker> bindMarkers = getBindMarkers(identifier);
-
 			if (bindMarkers == null) {
 				target.bind(identifier, value);
 				return;
 			}
-
 			if (value instanceof Collection) {
 				Collection<Object> collection = (Collection<Object>) value;
-
 				Iterator<Object> iterator = collection.iterator();
 				Iterator<BindMarker> markers = bindMarkers.iterator();
-
 				while (iterator.hasNext()) {
-
 					Object valueToBind = iterator.next();
-
 					if (valueToBind instanceof Object[]) {
 						Object[] objects = (Object[]) valueToBind;
 						for (Object object : objects) {
@@ -557,24 +541,19 @@ abstract class NamedParameterUtils {
 			}
 		}
 
-		private void bind(BindTarget target, Iterator<BindMarker> markers,
+		private void bind(BindTarget target, Iterator<BindMarker> markers, Object valueToBind) {
-				Object valueToBind) {
-
 			Assert.isTrue(markers.hasNext(), () -> String.format(
 					"No bind marker for value [%s] in SQL [%s]. Check that the query was expanded using the same arguments.",
 					valueToBind, toQuery()));
-
 			markers.next().bind(target, valueToBind);
 		}
 
 		public void bindNull(BindTarget target, String identifier, Class<?> valueType) {
 			List<BindMarker> bindMarkers = getBindMarkers(identifier);
-
 			if (bindMarkers == null) {
 				target.bindNull(identifier, valueType);
 				return;
 			}
-
 			for (BindMarker bindMarker : bindMarkers) {
 				bindMarker.bindNull(target, valueType);
 			}
@@ -582,19 +561,14 @@ abstract class NamedParameterUtils {
 
 		@Nullable
 		List<BindMarker> getBindMarkers(String identifier) {
-			List<NamedParameters.NamedParameter> parameters = this.parameters.getMarker(
+			List<NamedParameters.NamedParameter> parameters = this.parameters.getMarker(identifier);
-					identifier);
-
 			if (parameters == null) {
 				return null;
 			}
-
 			List<BindMarker> markers = new ArrayList<>();
-
 			for (NamedParameters.NamedParameter parameter : parameters) {
 				markers.addAll(parameter.placeholders);
 			}
-
 			return markers;
 		}
 
@@ -605,14 +579,10 @@ abstract class NamedParameterUtils {
 
 		@Override
 		public void bindTo(BindTarget target) {
-
 			for (String namedParameter : this.parameterSource.getParameterNames()) {
-
 				Object value = this.parameterSource.getValue(namedParameter);
-
 				if (value == null) {
-					bindNull(target, namedParameter,
+					bindNull(target, namedParameter, this.parameterSource.getType(namedParameter));
-							this.parameterSource.getType(namedParameter));
 				}
 				else {
 					bind(target, namedParameter, value);
@@ -624,7 +594,6 @@ abstract class NamedParameterUtils {
 		public String toQuery() {
 			return this.expandedSql;
 		}
-
 	}
 
 }

spring-r2dbc/src/main/java/org/springframework/r2dbc/core/Parameter.java

@@ -27,6 +27,7 @@ import org.springframework.util.ObjectUtils;
  * A database value that can be set in a statement.
  *
  * @author Mark Paluch
+ * @author Juergen Hoeller
  * @since 5.3
  */
 public final class Parameter {
@@ -36,6 +37,7 @@ public final class Parameter {
 
 	private final Class<?> type;
 
+
 	private Parameter(@Nullable Object value, Class<?> type) {
 		Assert.notNull(type, "Type must not be null");
 		this.value = value;
@@ -45,7 +47,7 @@ public final class Parameter {
 
 	/**
 	 * Create a new {@link Parameter} from {@code value}.
-	 * @param value must not be {@code null}
+	 * @param value the parameter value
 	 * @return the {@link Parameter} value for {@code value}
 	 */
 	public static Parameter from(Object value) {
@@ -55,12 +57,12 @@ public final class Parameter {
 
 	/**
 	 * Create a new {@link Parameter} from {@code value} and {@code type}.
-	 * @param value can be {@code null}
+	 * @param value the parameter value (can be {@code null})
-	 * @param type must not be {@code null}
+	 * @param type the parameter type
 	 * @return the {@link Parameter} value for {@code value}
 	 */
 	public static Parameter fromOrEmpty(@Nullable Object value, Class<?> type) {
-		return value == null ? empty(type) : new Parameter(value, ClassUtils.getUserClass(value));
+		return (value == null ? empty(type) : new Parameter(value, ClassUtils.getUserClass(value)));
 	}
 
 	/**
@@ -74,7 +76,7 @@ public final class Parameter {
 
 
 	/**
-	 * Return the column value. Can be {@code null}.
+	 * Return the column value (can be {@code null}).
 	 * @see #hasValue()
 	 */
 	@Nullable
@@ -83,14 +85,14 @@ public final class Parameter {
 	}
 
 	/**
-	 * Returns the column value type. Must be also present if the {@code value} is {@code null}.
+	 * Return the column value type. Must be also present if the {@code value} is {@code null}.
 	 */
 	public Class<?> getType() {
 		return this.type;
 	}
 
 	/**
-	 * Returns whether this {@link Parameter} has a value.
+	 * Return whether this {@link Parameter} has a value.
 	 * @return {@code false} if {@link #getValue()} is {@code null}
 	 */
 	public boolean hasValue() {
@@ -98,7 +100,7 @@ public final class Parameter {
 	}
 
 	/**
-	 * Returns whether this {@link Parameter} has a empty.
+	 * Return whether this {@link Parameter} has a empty.
 	 * @return {@code true} if {@link #getValue()} is {@code null}
 	 */
 	public boolean isEmpty() {
@@ -115,7 +117,8 @@ public final class Parameter {
 			return false;
 		}
 		Parameter other = (Parameter) obj;
-		return ObjectUtils.nullSafeEquals(this.value, other.value) && ObjectUtils.nullSafeEquals(this.type, other.type);
+		return (ObjectUtils.nullSafeEquals(this.value, other.value) &&
+				ObjectUtils.nullSafeEquals(this.type, other.type));
 	}
 
 	@Override
@@ -125,7 +128,7 @@ public final class Parameter {
 
 	@Override
 	public String toString() {
-		return "Parameter[value=" + this.value + ", type=" + this.type + ']';
+		return "Parameter[value=" + this.value + ",type=" + this.type.getName() + "]";
 	}
 
 }

spring-r2dbc/src/main/java/org/springframework/r2dbc/core/ParsedSql.java

@@ -28,11 +28,11 @@ import java.util.List;
  */
 class ParsedSql {
 
-	private String originalSql;
+	private final String originalSql;
 
-	private List<String> parameterNames = new ArrayList<>();
+	private final List<String> parameterNames = new ArrayList<>();
 
-	private List<int[]> parameterIndexes = new ArrayList<>();
+	private final List<int[]> parameterIndexes = new ArrayList<>();
 
 	private int namedParameterCount;
 

spring-r2dbc/src/main/java/org/springframework/r2dbc/core/PreparedOperation.java

@@ -24,6 +24,7 @@ import org.springframework.r2dbc.core.binding.BindTarget;
  * Extension to {@link QueryOperation} for a prepared SQL query
  * {@link Supplier} with bound parameters. Contains parameter
  * bindings that can be {@link #bindTo bound} bound to a {@link BindTarget}.
+ *
  * <p>Can be executed with {@link org.springframework.r2dbc.core.DatabaseClient}.
  *
  * @author Mark Paluch
@@ -35,13 +36,13 @@ public interface PreparedOperation<T> extends QueryOperation {
 
 	/**
 	 * Return the underlying query source.
-	 * @return the query source, such as a statement/criteria object.
+	 * @return the query source, such as a statement/criteria object
 	 */
 	T getSource();
 
 	/**
 	 * Apply bindings to {@link BindTarget}.
-	 * @param target the target to apply bindings to.
+	 * @param target the target to apply bindings to
 	 */
 	void bindTo(BindTarget target);
 

spring-r2dbc/src/main/java/org/springframework/r2dbc/core/QueryOperation.java

@@ -32,7 +32,7 @@ import java.util.function.Supplier;
 public interface QueryOperation extends Supplier<String> {
 
 	/**
-	 * Returns the string-representation of this operation to
+	 * Return the string-representation of this operation to
 	 * be used with {@link io.r2dbc.spi.Statement} creation.
 	 * @return the operation as SQL string
 	 * @see io.r2dbc.spi.Connection#createStatement(String)

spring-r2dbc/src/main/java/org/springframework/r2dbc/core/RowsFetchSpec.java

@@ -30,21 +30,20 @@ public interface RowsFetchSpec<T> {
 
 	/**
 	 * Get exactly zero or one result.
-	 *
+	 * @return a Mono emitting one element, or {@link Mono#empty()} if no match found.
-	 * @return a mono emitting one element. {@link Mono#empty()} if no match found.
 	 * Completes with {@code IncorrectResultSizeDataAccessException} if more than one match found
 	 */
 	Mono<T> one();
 
 	/**
 	 * Get the first or no result.
-	 * @return a mono emitting the first element. {@link Mono#empty()} if no match found
+	 * @return a Mono emitting the first element, or {@link Mono#empty()} if no match found
 	 */
 	Mono<T> first();
 
 	/**
 	 * Get all matching elements.
-	 * @return a flux emitting all results
+	 * @return a Flux emitting all results
 	 */
 	Flux<T> all();
 

spring-r2dbc/src/main/java/org/springframework/r2dbc/core/SqlProvider.java

@@ -33,7 +33,7 @@ public interface SqlProvider {
 	/**
 	 * Return the SQL string for this object, i.e.
 	 * typically the SQL used for creating statements.
-	 * @return the SQL string, or {@code null}
+	 * @return the SQL string, or {@code null} if not available
 	 */
 	@Nullable
 	String getSql();

spring-r2dbc/src/main/java/org/springframework/r2dbc/core/StatementFilterFunction.java

@@ -24,18 +24,27 @@ import org.springframework.util.Assert;
 
 /**
  * Represents a function that filters an {@link ExecuteFunction execute function}.
+ *
  * <p>The filter is executed when a {@link org.reactivestreams.Subscriber} subscribes
  * to the {@link Publisher} returned by the {@link DatabaseClient}.
+ *
  * <p>StatementFilterFunctions are typically used to specify additional details on
  * the Statement objects such as {@code fetchSize} or key generation.
  *
  * @author Mark Paluch
+ * @author Juergen Hoeller
  * @since 5.3
  * @see ExecuteFunction
  */
 @FunctionalInterface
 public interface StatementFilterFunction {
 
+	/**
+	 * An empty {@link StatementFilterFunction} that delegates to {@link ExecuteFunction}.
+	 */
+	StatementFilterFunction EMPTY_FILTER = (statement, next) -> next.execute(statement);
+
+
 	/**
 	 * Apply this filter to the given {@link Statement} and {@link ExecuteFunction}.
 	 * <p>The given {@link ExecuteFunction} represents the next entity in the chain,

spring-r2dbc/src/main/java/org/springframework/r2dbc/core/StatementFilterFunctions.java

@@ -1,47 +0,0 @@
-/*
- * Copyright 2002-2020 the original author or authors.
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- *      https://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-
-package org.springframework.r2dbc.core;
-
-import io.r2dbc.spi.Result;
-import io.r2dbc.spi.Statement;
-import org.reactivestreams.Publisher;
-
-/**
- * Collection of default {@link StatementFilterFunction}s.
- *
- * @author Mark Paluch
- * @since 5.3
- */
-enum StatementFilterFunctions implements StatementFilterFunction {
-
-	EMPTY_FILTER;
-
-
-	@Override
-	public Publisher<? extends Result> filter(Statement statement, ExecuteFunction next) {
-		return next.execute(statement);
-	}
-
-	/**
-	 * Return an empty {@link StatementFilterFunction} that delegates to {@link ExecuteFunction}.
-	 * @return an empty {@link StatementFilterFunction} that delegates to {@link ExecuteFunction}.
-	 */
-	public static StatementFilterFunction empty() {
-		return EMPTY_FILTER;
-	}
-
-}

spring-r2dbc/src/main/java/org/springframework/r2dbc/core/UpdatedRowsFetchSpec.java

@@ -28,7 +28,7 @@ public interface UpdatedRowsFetchSpec {
 
 	/**
 	 * Get the number of updated rows.
-	 * @return a mono emitting the number of updated rows
+	 * @return a Mono emitting the number of updated rows
 	 */
 	Mono<Integer> rowsUpdated();
 

spring-r2dbc/src/main/java/org/springframework/r2dbc/core/binding/AnonymousBindMarkers.java

@@ -34,8 +34,8 @@ import java.util.concurrent.atomic.AtomicIntegerFieldUpdater;
  */
 class AnonymousBindMarkers implements BindMarkers {
 
-	private static final AtomicIntegerFieldUpdater<AnonymousBindMarkers> COUNTER_INCREMENTER = AtomicIntegerFieldUpdater
+	private static final AtomicIntegerFieldUpdater<AnonymousBindMarkers> COUNTER_INCREMENTER =
-			.newUpdater(AnonymousBindMarkers.class, "counter");
+			AtomicIntegerFieldUpdater.newUpdater(AnonymousBindMarkers.class, "counter");
 
 
 	private final String placeholder;

spring-r2dbc/src/main/java/org/springframework/r2dbc/core/binding/BindMarker.java

@@ -39,8 +39,8 @@ public interface BindMarker {
 	/**
 	 * Bind the given {@code value} to the {@link Statement} using the underlying binding strategy.
 	 * @param bindTarget the target to bind the value to
-	 * @param value the actual value. Must not be {@code null}
+	 * @param value the actual value (must not be {@code null};
-	 * Use {@link #bindNull(BindTarget, Class)} for {@code null} values
+	 * use {@link #bindNull(BindTarget, Class)} for {@code null} values)
 	 * @see Statement#bind
 	 */
 	void bind(BindTarget bindTarget, Object value);
@@ -48,7 +48,7 @@ public interface BindMarker {
 	/**
 	 * Bind a {@code null} value to the {@link Statement} using the underlying binding strategy.
 	 * @param bindTarget the target to bind the value to
-	 * @param valueType value type, must not be {@code null}
+	 * @param valueType the value type (must not be {@code null})
 	 * @see Statement#bindNull
 	 */
 	void bindNull(BindTarget bindTarget, Class<?> valueType);

spring-r2dbc/src/main/java/org/springframework/r2dbc/core/binding/BindMarkers.java

@@ -36,7 +36,6 @@ public interface BindMarkers {
 
 	/**
 	 * Create a new {@link BindMarker}.
-	 * @return a new {@link BindMarker}
 	 */
 	BindMarker next();
 

spring-r2dbc/src/main/java/org/springframework/r2dbc/core/binding/BindMarkersFactory.java

@@ -40,24 +40,20 @@ public interface BindMarkersFactory {
 
 	/**
 	 * Create a new {@link BindMarkers} instance.
-	 * @return a new {@link BindMarkers} instance
 	 */
 	BindMarkers create();
 
 	/**
-	 * Return whether the {@link BindMarkersFactory} uses identifiable
+	 * Return whether the {@link BindMarkersFactory} uses identifiable placeholders:
-	 * placeholders.
+	 * {@code false} if multiple placeholders cannot be distinguished by just the
-	 * @return whether the {@link BindMarkersFactory} uses identifiable
+	 * {@link BindMarker#getPlaceholder() placeholder} identifier.
-	 * placeholders. {@code false} if multiple placeholders cannot be
-	 * distinguished by just the {@link BindMarker#getPlaceholder() placeholder}
-	 * identifier.
 	 */
 	default boolean identifiablePlaceholders() {
 		return true;
 	}
 
 
-	// Static, factory methods
+	// Static factory methods
 
 	/**
 	 * Create index-based {@link BindMarkers} using indexes to bind parameters.
@@ -88,12 +84,10 @@ public interface BindMarkersFactory {
 	static BindMarkersFactory anonymous(String placeholder) {
 		Assert.hasText(placeholder, "Placeholder must not be empty!");
 		return new BindMarkersFactory() {
-
 			@Override
 			public BindMarkers create() {
 				return new AnonymousBindMarkers(placeholder);
 			}
-
 			@Override
 			public boolean identifiablePlaceholders() {
 				return false;
@@ -140,6 +134,7 @@ public interface BindMarkersFactory {
 	 */
 	static BindMarkersFactory named(String prefix, String namePrefix, int maxLength,
 			Function<String, String> hintFilterFunction) {
+
 		Assert.notNull(prefix, "Prefix must not be null");
 		Assert.notNull(namePrefix, "Index prefix must not be null");
 		Assert.notNull(hintFilterFunction, "Hint filter function must not be null");

spring-r2dbc/src/main/java/org/springframework/r2dbc/core/binding/BindMarkersFactoryResolver.java

@@ -45,31 +45,25 @@ public final class BindMarkersFactoryResolver {
 
 
 	/**
-	 * Retrieve a {@link BindMarkersFactory} by inspecting {@link ConnectionFactory} and
+	 * Retrieve a {@link BindMarkersFactory} by inspecting {@link ConnectionFactory}
-	 * its metadata.
+	 * and its metadata.
-	 *
 	 * @param connectionFactory the connection factory to inspect
 	 * @return the resolved {@link BindMarkersFactory}
-	 * @throws NoBindMarkersFactoryException if no {@link BindMarkersFactory} can be
+	 * @throws NoBindMarkersFactoryException if no {@link BindMarkersFactory} can be resolved
-	 *         resolved
 	 */
 	public static BindMarkersFactory resolve(ConnectionFactory connectionFactory) {
-
 		for (BindMarkerFactoryProvider detector : DETECTORS) {
-			BindMarkersFactory bindMarkersFactory = detector.getBindMarkers(
+			BindMarkersFactory bindMarkersFactory = detector.getBindMarkers(connectionFactory);
-					connectionFactory);
 			if (bindMarkersFactory != null) {
 				return bindMarkersFactory;
 			}
 		}
-
+		throw new NoBindMarkersFactoryException(String.format(
-		throw new NoBindMarkersFactoryException(
+				"Cannot determine a BindMarkersFactory for %s using %s",
-				String.format("Cannot determine a BindMarkersFactory for %s using %s",
+				connectionFactory.getMetadata().getName(), connectionFactory));
-						connectionFactory.getMetadata().getName(), connectionFactory));
 	}
 
 
-	// utility constructor.
 	private BindMarkersFactoryResolver() {
 	}
 
@@ -84,16 +78,13 @@ public final class BindMarkersFactoryResolver {
 	public interface BindMarkerFactoryProvider {
 
 		/**
-		 * Returns a {@link BindMarkersFactory} for a {@link ConnectionFactory}.
+		 * Return a {@link BindMarkersFactory} for a {@link ConnectionFactory}.
-		 *
+		 * @param connectionFactory the connection factory to be used with the {@link BindMarkersFactory}
-		 * @param connectionFactory the connection factory to be used with the
-		 *        {@link BindMarkersFactory}.
 		 * @return the {@link BindMarkersFactory} if the {@link BindMarkerFactoryProvider}
-		 *         can provide a bind marker factory object, otherwise {@code null}
+		 * can provide a bind marker factory object, otherwise {@code null}
 		 */
 		@Nullable
 		BindMarkersFactory getBindMarkers(ConnectionFactory connectionFactory);
-
 	}
 
 
@@ -102,18 +93,15 @@ public final class BindMarkersFactoryResolver {
 	 * {@link BindMarkersFactory}.
 	 */
 	@SuppressWarnings("serial")
-	public static class NoBindMarkersFactoryException
+	public static class NoBindMarkersFactoryException extends NonTransientDataAccessException {
-			extends NonTransientDataAccessException {
 
 		/**
 		 * Constructor for NoBindMarkersFactoryException.
-		 *
 		 * @param msg the detail message
 		 */
 		public NoBindMarkersFactoryException(String msg) {
 			super(msg);
 		}
-
 	}
 
 
@@ -125,13 +113,13 @@ public final class BindMarkersFactoryResolver {
 	 */
 	static class BuiltInBindMarkersFactoryProvider implements BindMarkerFactoryProvider {
 
-		private static final Map<String, BindMarkersFactory> BUILTIN = new LinkedCaseInsensitiveMap<>(
+		private static final Map<String, BindMarkersFactory> BUILTIN =
-				Locale.ENGLISH);
+				new LinkedCaseInsensitiveMap<>(Locale.ENGLISH);
 
 		static {
 			BUILTIN.put("H2", BindMarkersFactory.indexed("$", 1));
 			BUILTIN.put("Microsoft SQL Server", BindMarkersFactory.named("@", "P", 32,
-			BuiltInBindMarkersFactoryProvider::filterBindMarker));
+					BuiltInBindMarkersFactoryProvider::filterBindMarker));
 			BUILTIN.put("MySQL", BindMarkersFactory.anonymous("?"));
 			BUILTIN.put("MariaDB", BindMarkersFactory.anonymous("?"));
 			BUILTIN.put("PostgreSQL", BindMarkersFactory.indexed("$", 1));
@@ -142,40 +130,31 @@ public final class BindMarkersFactoryResolver {
 		public BindMarkersFactory getBindMarkers(ConnectionFactory connectionFactory) {
 			ConnectionFactoryMetadata metadata = connectionFactory.getMetadata();
 			BindMarkersFactory r2dbcDialect = BUILTIN.get(metadata.getName());
-
 			if (r2dbcDialect != null) {
 				return r2dbcDialect;
 			}
-
-
 			for (String it : BUILTIN.keySet()) {
 				if (metadata.getName().contains(it)) {
 					return BUILTIN.get(it);
 				}
 			}
-
 			return null;
 		}
 
 		private static String filterBindMarker(CharSequence input) {
-			StringBuilder builder = new StringBuilder();
+			StringBuilder builder = new StringBuilder(input.length());
-
 			for (int i = 0; i < input.length(); i++) {
-
 				char ch = input.charAt(i);
 				// ascii letter or digit
 				if (Character.isLetterOrDigit(ch) && ch < 127) {
 					builder.append(ch);
 				}
 			}
-
 			if (builder.length() == 0) {
 				return "";
 			}
-
 			return "_" + builder.toString();
 		}
-
 	}
 
 }

spring-r2dbc/src/main/java/org/springframework/r2dbc/core/binding/Bindings.java

@@ -55,11 +55,11 @@ public class Bindings implements Iterable<Bindings.Binding> {
 	}
 
 	/**
-	 * Create {@link Bindings} from a {@link Map}.
+	 * Create {@link Bindings} from the given collection.
-	 * @param bindings must not be {@code null}
+	 * @param bindings a collection of {@link Binding} objects
 	 */
 	public Bindings(Collection<Binding> bindings) {
-		Assert.notNull(bindings, "Bindings must not be null");
+		Assert.notNull(bindings, "Collection must not be null");
 		Map<BindMarker, Binding> mapping = CollectionUtils.newLinkedHashMap(bindings.size());
 		bindings.forEach(binding -> mapping.put(binding.getBindMarker(), binding));
 		this.bindings = mapping;
@@ -75,10 +75,10 @@ public class Bindings implements Iterable<Bindings.Binding> {
 	}
 
 	/**
-	 * Merge this bindings with an other {@link Bindings} object and create a new merged
+	 * Merge this bindings with an other {@link Bindings} object and
-	 * {@link Bindings} object.
+	 * create a new merged {@link Bindings} object.
 	 * @param other the object to merge with
-	 * @return a new, merged {@link Bindings} object
+	 * @return a newly merged {@link Bindings} object
 	 */
 	public Bindings and(Bindings other) {
 		return merge(this, other);
@@ -116,25 +116,23 @@ public class Bindings implements Iterable<Bindings.Binding> {
 
 
 	/**
-	 * Create a new, empty {@link Bindings} object.
+	 * Return an empty {@link Bindings} object.
-	 * @return a new, empty {@link Bindings} object.
 	 */
 	public static Bindings empty() {
 		return EMPTY;
 	}
 
 	/**
-	 * Merge this bindings with an other {@link Bindings} object and create a new merged
+	 * Merge this bindings with an other {@link Bindings} object and
-	 * {@link Bindings} object.
+	 * create a new merged {@link Bindings} object.
 	 * @param left the left object to merge with
 	 * @param right the right object to merge with
-	 * @return a new, merged {@link Bindings} object
+	 * @return a newly merged {@link Bindings} object
 	 */
 	public static Bindings merge(Bindings left, Bindings right) {
 		Assert.notNull(left, "Left side Bindings must not be null");
 		Assert.notNull(right, "Right side Bindings must not be null");
-		List<Binding> result = new ArrayList<>(
+		List<Binding> result = new ArrayList<>(left.getBindings().size() + right.getBindings().size());
-				left.getBindings().size() + right.getBindings().size());
 		result.addAll(left.getBindings().values());
 		result.addAll(right.getBindings().values());
 		return new Bindings(result);
@@ -154,7 +152,6 @@ public class Bindings implements Iterable<Bindings.Binding> {
 
 		/**
 		 * Return the associated {@link BindMarker}.
-		 * @return the associated {@link BindMarker}.
 		 */
 		public BindMarker getBindMarker() {
 			return this.marker;
@@ -162,8 +159,8 @@ public class Bindings implements Iterable<Bindings.Binding> {
 
 		/**
 		 * Return whether the binding has a value associated with it.
-		 * @return {@code true} if there is a value present, otherwise {@code false}
+		 * @return {@code true} if there is a value present,
-		 * for a {@code NULL} binding.
+		 * otherwise {@code false} for a {@code NULL} binding
 		 */
 		public abstract boolean hasValue();
 
@@ -177,8 +174,8 @@ public class Bindings implements Iterable<Bindings.Binding> {
 
 		/**
 		 * Return the binding value.
-		 * @return value of this binding. Can be {@code null}
+		 * @return the value of this binding
-		 * if this is a {@code NULL} binding.
+		 * (can be {@code null} if this is a {@code NULL} binding)
 		 */
 		@Nullable
 		public abstract Object getValue();

spring-r2dbc/src/main/java/org/springframework/r2dbc/core/binding/IndexedBindMarkers.java

@@ -22,14 +22,15 @@ import java.util.concurrent.atomic.AtomicIntegerFieldUpdater;
  * Index-based bind marker. This implementation creates indexed bind
  * markers using a numeric index and an optional prefix for bind markers
  * to be represented within the query string.
+ *
  * @author Mark Paluch
  * @author Jens Schauder
  * @since 5.3
  */
 class IndexedBindMarkers implements BindMarkers {
 
-	private static final AtomicIntegerFieldUpdater<IndexedBindMarkers> COUNTER_INCREMENTER = AtomicIntegerFieldUpdater
+	private static final AtomicIntegerFieldUpdater<IndexedBindMarkers> COUNTER_INCREMENTER =
-			.newUpdater(IndexedBindMarkers.class, "counter");
+			AtomicIntegerFieldUpdater.newUpdater(IndexedBindMarkers.class, "counter");
 
 
 	private final int offset;
@@ -59,6 +60,7 @@ class IndexedBindMarkers implements BindMarkers {
 		return new IndexedBindMarker(this.prefix + "" + (index + this.offset), index);
 	}
 
+
 	/**
 	 * A single indexed bind marker.
 	 * @author Mark Paluch
@@ -69,13 +71,11 @@ class IndexedBindMarkers implements BindMarkers {
 
 		private final int index;
 
-
 		IndexedBindMarker(String placeholder, int index) {
 			this.placeholder = placeholder;
 			this.index = index;
 		}
 
-
 		@Override
 		public String getPlaceholder() {
 			return this.placeholder;
@@ -94,7 +94,6 @@ class IndexedBindMarkers implements BindMarkers {
 		public int getIndex() {
 			return this.index;
 		}
-
 	}
 
 }

spring-r2dbc/src/main/java/org/springframework/r2dbc/core/binding/MutableBindings.java

@@ -36,7 +36,7 @@ public class MutableBindings extends Bindings {
 
 	/**
 	 * Create new {@link MutableBindings}.
-	 * @param markers must not be {@code null}.
+	 * @param markers the {@link BindMarkers} to wrap
 	 */
 	public MutableBindings(BindMarkers markers) {
 		super(new LinkedHashMap<>());
@@ -66,8 +66,8 @@ public class MutableBindings extends Bindings {
 
 	/**
 	 * Bind a value to {@link BindMarker}.
-	 * @param marker must not be {@code null}
+	 * @param marker the {@link BindMarker} to bind to
-	 * @param value must not be {@code null}
+	 * @param value the value to bind
 	 */
 	public MutableBindings bind(BindMarker marker, Object value) {
 		Assert.notNull(marker, "BindMarker must not be null");
@@ -79,7 +79,7 @@ public class MutableBindings extends Bindings {
 	/**
 	 * Bind a value and return the related {@link BindMarker}.
 	 * Increments {@link BindMarkers} state.
-	 * @param value must not be {@code null}
+	 * @param value the value to bind
 	 */
 	public BindMarker bind(Object value) {
 		Assert.notNull(value, "Value must not be null");
@@ -90,8 +90,8 @@ public class MutableBindings extends Bindings {
 
 	/**
 	 * Bind a {@code NULL} value to {@link BindMarker}.
-	 * @param marker must not be {@code null}
+	 * @param marker the {@link BindMarker} to bind to
-	 * @param valueType must not be {@code null}
+	 * @param valueType the value type
 	 */
 	public MutableBindings bindNull(BindMarker marker, Class<?> valueType) {
 		Assert.notNull(marker, "BindMarker must not be null");
@@ -103,7 +103,7 @@ public class MutableBindings extends Bindings {
 	/**
 	 * Bind a {@code NULL} value and return the related {@link BindMarker}.
 	 * Increments {@link BindMarkers} state.
-	 * @param valueType must not be {@code null}
+	 * @param valueType the value type
 	 */
 	public BindMarker bindNull(Class<?> valueType) {
 		Assert.notNull(valueType, "Value type must not be null");

spring-r2dbc/src/main/java/org/springframework/r2dbc/core/binding/NamedBindMarkers.java

@@ -29,8 +29,8 @@ import org.springframework.util.Assert;
  */
 class NamedBindMarkers implements BindMarkers {
 
-	private static final AtomicIntegerFieldUpdater<NamedBindMarkers> COUNTER_INCREMENTER = AtomicIntegerFieldUpdater
+	private static final AtomicIntegerFieldUpdater<NamedBindMarkers> COUNTER_INCREMENTER =
-			.newUpdater(NamedBindMarkers.class, "counter");
+			AtomicIntegerFieldUpdater.newUpdater(NamedBindMarkers.class, "counter");
 
 
 	private final String prefix;
@@ -88,7 +88,6 @@ class NamedBindMarkers implements BindMarkers {
 		private final String identifier;
 
 		NamedBindMarker(String placeholder, String identifier) {
-
 			this.placeholder = placeholder;
 			this.identifier = identifier;
 		}
@@ -107,7 +106,6 @@ class NamedBindMarkers implements BindMarkers {
 		public void bindNull(BindTarget target, Class<?> valueType) {
 			target.bindNull(this.identifier, valueType);
 		}
-
 	}
 
 }