Protect against null return value from DataSource.getConnection()

Issue: SPR-15641

spring-jdbc/src/main/java/org/springframework/jdbc/CannotGetJdbcConnectionException.java

@@ -25,10 +25,20 @@ import org.springframework.lang.Nullable;
  * Fatal exception thrown when we can't connect to an RDBMS using JDBC.
  *
  * @author Rod Johnson
+ * @author Juergen Hoeller
  */
 @SuppressWarnings("serial")
 public class CannotGetJdbcConnectionException extends DataAccessResourceFailureException {
 
+	/**
+	 * Constructor for CannotGetJdbcConnectionException.
+	 * @param msg the detail message
+	 * @since 5.0
+	 */
+	public CannotGetJdbcConnectionException(String msg) {
+		super(msg);
+	}
+
 	/**
 	 * Constructor for CannotGetJdbcConnectionException.
 	 * @param msg the detail message

spring-jdbc/src/main/java/org/springframework/jdbc/datasource/DataSourceUtils.java

@@ -78,7 +78,10 @@ public abstract class DataSourceUtils {
 			return doGetConnection(dataSource);
 		}
 		catch (SQLException ex) {
-			throw new CannotGetJdbcConnectionException("Could not get JDBC Connection", ex);
+			throw new CannotGetJdbcConnectionException("Failed to obtain JDBC Connection", ex);
+		}
+		catch (IllegalStateException ex) {
+			throw new CannotGetJdbcConnectionException("Failed to obtain JDBC Connection: " + ex.getMessage());
 		}
 	}
 
@@ -102,14 +105,14 @@ public abstract class DataSourceUtils {
 			conHolder.requested();
 			if (!conHolder.hasConnection()) {
 				logger.debug("Fetching resumed JDBC Connection from DataSource");
-				conHolder.setConnection(dataSource.getConnection());
+				conHolder.setConnection(fetchConnection(dataSource));
 			}
 			return conHolder.getConnection();
 		}
 		// Else we either got no holder or an empty thread-bound holder here.
 
 		logger.debug("Fetching JDBC Connection from DataSource");
-		Connection con = dataSource.getConnection();
+		Connection con = fetchConnection(dataSource);
 
 		if (TransactionSynchronizationManager.isSynchronizationActive()) {
 			logger.debug("Registering transaction synchronization for JDBC Connection");
@@ -134,6 +137,24 @@ public abstract class DataSourceUtils {
 		return con;
 	}
 
+	/**
+	 * Actually fetch a {@link Connection} from the given {@link DataSource},
+	 * defensively turning an unexpected {@code null} return value from
+	 * {@link DataSource#getConnection()} into an {@link IllegalStateException}.
+	 * @param dataSource the DataSource to obtain Connections from
+	 * @return a JDBC Connection from the given DataSource (never {@code null})
+	 * @throws SQLException if thrown by JDBC methods
+	 * @throws IllegalStateException if the DataSource returned a null value
+	 * @see DataSource#getConnection()
+	 */
+	private static Connection fetchConnection(DataSource dataSource) throws SQLException {
+		Connection con = dataSource.getConnection();
+		if (con == null) {
+			throw new IllegalStateException("DataSource returned null from getConnection(): " + dataSource);
+		}
+		return con;
+	}
+
 	/**
 	 * Prepare the given Connection with the given transaction semantics.
 	 * @param con the Connection to prepare

spring-jdbc/src/main/java/org/springframework/jdbc/datasource/embedded/AbstractEmbeddedDatabaseConfigurer.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2015 the original author or authors.
+ * Copyright 2002-2017 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.
@@ -40,8 +40,10 @@ abstract class AbstractEmbeddedDatabaseConfigurer implements EmbeddedDatabaseCon
 		Connection con = null;
 		try {
 			con = dataSource.getConnection();
+			if (con != null) {
 				con.createStatement().execute("SHUTDOWN");
 			}
+		}
 		catch (SQLException ex) {
 			logger.warn("Could not shut down embedded database", ex);
 		}

spring-jdbc/src/main/java/org/springframework/jdbc/support/DatabaseStartupValidator.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2012 the original author or authors.
+ * Copyright 2002-2017 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.
@@ -112,6 +112,10 @@ public class DatabaseStartupValidator implements InitializingBean {
 				Statement stmt = null;
 				try {
 					con = this.dataSource.getConnection();
+					if (con == null) {
+						throw new CannotGetJdbcConnectionException("Failed to execute validation query: " +
+								"DataSource returned null from getConnection(): " + this.dataSource);
+					}
 					stmt = con.createStatement();
 					stmt.execute(this.validationQuery);
 					validated = true;