RSocketRequester support for route vars

Closes gh-23310

spring-messaging/src/main/java/org/springframework/messaging/rsocket/DefaultRSocketRequester.java

@@ -19,6 +19,8 @@ package org.springframework.messaging.rsocket;
 import java.util.Collections;
 import java.util.LinkedHashMap;
 import java.util.Map;
+import java.util.regex.Matcher;
+import java.util.regex.Pattern;
 
 import io.netty.buffer.ByteBuf;
 import io.netty.buffer.ByteBufAllocator;
@@ -44,6 +46,7 @@ import org.springframework.core.io.buffer.NettyDataBufferFactory;
 import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 import org.springframework.util.MimeType;
+import org.springframework.util.ObjectUtils;
 
 /**
  * Default, package-private {@link RSocketRequester} implementation.
@@ -58,6 +61,9 @@ final class DefaultRSocketRequester implements RSocketRequester {
 	static final MimeType ROUTING = new MimeType("message", "x.rsocket.routing.v0");
 
 
+	/** For route variable replacement. */
+	private static final Pattern VARS_PATTERN = Pattern.compile("\\{([^/]+?)\\}");
+
 	private static final Map<String, Object> EMPTY_HINTS = Collections.emptyMap();
 
 
@@ -105,11 +111,29 @@ final class DefaultRSocketRequester implements RSocketRequester {
 	}
 
 	@Override
-	public RequestSpec route(String route) {
+	public RequestSpec route(String route, Object... vars) {
 		Assert.notNull(route, "'route' is required");
+		route = expand(route, vars);
 		return new DefaultRequestSpec(route, metadataMimeType().equals(COMPOSITE_METADATA) ? ROUTING : null);
 	}
 
+	private static String expand(String route, Object... vars) {
+		if (ObjectUtils.isEmpty(vars)) {
+			return route;
+		}
+		StringBuffer sb = new StringBuffer();
+		int index = 0;
+		Matcher matcher = VARS_PATTERN.matcher(route);
+		while (matcher.find()) {
+			Assert.isTrue(index < vars.length, () -> "No value for variable '" + matcher.group(1) + "'");
+			String value = vars[index].toString();
+			value = value.contains(".") ? value.replaceAll("\\.", "%2E") : value;
+			matcher.appendReplacement(sb, value);
+			index++;
+		}
+		return sb.toString();
+	}
+
 	@Override
 	public RequestSpec metadata(Object metadata, @Nullable MimeType mimeType) {
 		return new DefaultRequestSpec(metadata, mimeType);

spring-messaging/src/main/java/org/springframework/messaging/rsocket/RSocketRequester.java

@@ -66,13 +66,19 @@ public interface RSocketRequester {
 
 	/**
 	 * Begin to specify a new request with the given route to a remote handler.
+	 * <p>The route can be a template with placeholders, e.g.
+	 * {@code "flight.{code}"} in which case the supplied route variables are
+	 * expanded into the template after being formatted via {@code toString()}.
+	 * If a formatted variable contains a "." it is replaced with the escape
+	 * sequence "%2E" to avoid treating it as separator by the responder .
 	 * <p>If the connection is set to use composite metadata, the route is
 	 * encoded as {@code "message/x.rsocket.routing.v0"}. Otherwise the route
 	 * is encoded according to the mime type for the connection.
 	 * @param route the route to a handler
+	 * @param routeVars variables to be expanded into the route template
 	 * @return a spec for further defining and executing the request
 	 */
-	RequestSpec route(String route);
+	RequestSpec route(String route, Object... routeVars);
 
 	/**
 	 * Begin to specify a new request with the given metadata.

spring-messaging/src/test/java/org/springframework/messaging/rsocket/DefaultRSocketRequesterTests.java

@@ -210,14 +210,17 @@ public class DefaultRSocketRequesterTests {
 				.hasMessageStartingWith("Connection configured for metadata mime type");
 	}
 
+	@Test
+	public void routeWithVars() {
+		RSocketRequester requester = RSocketRequester.wrap(this.rsocket, TEXT_PLAIN, TEXT_PLAIN, this.strategies);
+		requester.route("a.{b}.{c}", "BBB", "C.C.C").data("body").send().block();
+		assertThat(this.rsocket.getSavedPayload().getMetadataUtf8()).isEqualTo("a.BBB.C%2EC%2EC");
+	}
+
 	@Test
 	public void supportedMetadataMimeTypes() {
-
-		RSocketRequester.wrap(this.rsocket, TEXT_PLAIN,
-				COMPOSITE_METADATA, this.strategies);
-
-		RSocketRequester.wrap(this.rsocket, TEXT_PLAIN,
-				ROUTING, this.strategies);
+		RSocketRequester.wrap(this.rsocket, TEXT_PLAIN, COMPOSITE_METADATA, this.strategies);
+		RSocketRequester.wrap(this.rsocket, TEXT_PLAIN, ROUTING, this.strategies);
 	}
 
 	@Test