GH-1382: Republish Recoverer Improvements

Resolves #1382

Add expressions; make private method protected.

**cherry-pick to 2.4.x**

spring-rabbit/src/main/java/org/springframework/amqp/rabbit/retry/RepublishMessageRecoverer.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2014-2021 the original author or authors.
+ * Copyright 2014-2022 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.
@@ -29,6 +29,10 @@
 import org.springframework.amqp.core.MessageProperties;
 import org.springframework.amqp.rabbit.connection.RabbitUtils;
 import org.springframework.amqp.rabbit.core.RabbitTemplate;
+import org.springframework.expression.EvaluationContext;
+import org.springframework.expression.Expression;
+import org.springframework.expression.common.LiteralExpression;
+import org.springframework.expression.spel.support.StandardEvaluationContext;
 import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 
@@ -68,9 +72,11 @@ public class RepublishMessageRecoverer implements MessageRecoverer {
 
 	protected final AmqpTemplate errorTemplate; // NOSONAR
 
-	protected final String errorRoutingKey; // NOSONAR
+	protected final Expression errorRoutingKeyExpression; // NOSONAR
 
-	protected final String errorExchangeName; // NOSONAR
+	protected final Expression errorExchangeNameExpression; // NOSONAR
+
+	protected final EvaluationContext evaluationContext = new StandardEvaluationContext();
 
 	private String errorRoutingKeyPrefix = "error.";
 
@@ -80,19 +86,48 @@ public class RepublishMessageRecoverer implements MessageRecoverer {
 
 	private MessageDeliveryMode deliveryMode = MessageDeliveryMode.PERSISTENT;
 
+	/**
+	 * Create an instance with the provided template.
+	 * @param errorTemplate the template.
+	 */
 	public RepublishMessageRecoverer(AmqpTemplate errorTemplate) {
-		this(errorTemplate, null, null);
+		this(errorTemplate, (String) null, (String) null);
 	}
 
+	/**
+	 * Create an instance with the provided properties.
+	 * @param errorTemplate the template.
+	 * @param errorExchange the exchange.
+	 */
 	public RepublishMessageRecoverer(AmqpTemplate errorTemplate, String errorExchange) {
 		this(errorTemplate, errorExchange, null);
 	}
 
+	/**
+	 * Create an instance with the provided properties. If the exchange or routing key is null,
+	 * the template's default will be used.
+	 * @param errorTemplate the template.
+	 * @param errorExchange the exchange.
+	 * @param errorRoutingKey the routing key.
+	 */
 	public RepublishMessageRecoverer(AmqpTemplate errorTemplate, String errorExchange, String errorRoutingKey) {
+		this(errorTemplate, new LiteralExpression(errorExchange), new LiteralExpression(errorRoutingKey));
+	}
+
+	/**
+	 * Create an instance with the provided properties. If the exchange or routing key
+	 * evaluate to null, the template's default will be used.
+	 * @param errorTemplate the template.
+	 * @param errorExchange the exchange expression, evaluated against the message.
+	 * @param errorRoutingKey the routing key, evaluated against the message.
+	 */
+	public RepublishMessageRecoverer(AmqpTemplate errorTemplate, @Nullable Expression errorExchange,
+			@Nullable Expression errorRoutingKey) {
+
 		Assert.notNull(errorTemplate, "'errorTemplate' cannot be null");
 		this.errorTemplate = errorTemplate;
-		this.errorExchangeName = errorExchange;
-		this.errorRoutingKey = errorRoutingKey;
+		this.errorExchangeNameExpression = errorExchange != null ? errorExchange : new LiteralExpression(null);
+		this.errorRoutingKeyExpression = errorRoutingKey != null ? errorRoutingKey : new LiteralExpression(null);
 		if (!(this.errorTemplate instanceof RabbitTemplate)) {
 			this.maxStackTraceLength = Integer.MAX_VALUE;
 		}
@@ -175,17 +210,17 @@ public void recover(Message message, Throwable cause) {
 			messageProperties.setDeliveryMode(this.deliveryMode);
 		}
 
-		if (null != this.errorExchangeName) {
-			String routingKey = this.errorRoutingKey != null ? this.errorRoutingKey
-					: this.prefixedOriginalRoutingKey(message);
-			doSend(this.errorExchangeName, routingKey, message);
+		String exchangeName = this.errorExchangeNameExpression.getValue(this.evaluationContext, message, String.class);
+		String rk = this.errorRoutingKeyExpression.getValue(this.evaluationContext, message, String.class);
+		String routingKey = rk != null ? rk : this.prefixedOriginalRoutingKey(message);
+		if (null != exchangeName) {
+			doSend(exchangeName, routingKey, message);
 			if (this.logger.isWarnEnabled()) {
-				this.logger.warn("Republishing failed message to exchange '" + this.errorExchangeName
+				this.logger.warn("Republishing failed message to exchange '" + exchangeName
 						+ "' with routing key " + routingKey);
 			}
 		}
 		else {
-			final String routingKey = this.prefixedOriginalRoutingKey(message);
 			doSend(null, routingKey, message);
 			if (this.logger.isWarnEnabled()) {
 				this.logger.warn("Republishing failed message to the template's default exchange with routing key "
@@ -271,11 +306,24 @@ else if (stackTraceAsString.length() + exceptionMessage.length() > this.maxStack
 		return null;
 	}
 
-	private String prefixedOriginalRoutingKey(Message message) {
+	/**
+	 * The default behavior of this method is to append the received routing key to the
+	 * {@link #setErrorRoutingKeyPrefix(String) routingKeyPrefix}. This is only invoked
+	 * if the routing key is null.
+	 * @param message the message.
+	 * @return the routing key.
+	 */
+	protected String prefixedOriginalRoutingKey(Message message) {
 		return this.errorRoutingKeyPrefix + message.getMessageProperties().getReceivedRoutingKey();
 	}
 
-	private String getStackTraceAsString(Throwable cause) {
+	/**
+	 * Create a String representation of the stack trace.
+	 * @param cause the throwable.
+	 * @return the String.
+	 * @since  2.4.8
+	 */
+	protected String getStackTraceAsString(Throwable cause) {
 		StringWriter stringWriter = new StringWriter();
 		PrintWriter printWriter = new PrintWriter(stringWriter, true);
 		cause.printStackTrace(printWriter);

spring-rabbit/src/test/java/org/springframework/amqp/rabbit/retry/RepublishMessageRecovererTest.java → spring-rabbit/src/test/java/org/springframework/amqp/rabbit/retry/RepublishMessageRecovererTests.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2014-2019 the original author or authors.
+ * Copyright 2014-2022 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.
@@ -33,6 +33,7 @@
 import org.springframework.amqp.core.Message;
 import org.springframework.amqp.core.MessageDeliveryMode;
 import org.springframework.amqp.core.MessageProperties;
+import org.springframework.expression.spel.standard.SpelExpressionParser;
 
 /**
  * @author James Carr
@@ -42,7 +43,7 @@
  * @since 1.3
  */
 @ExtendWith(MockitoExtension.class)
-public class RepublishMessageRecovererTest {
+public class RepublishMessageRecovererTests {
 
 	private final Message message = new Message("".getBytes(), new MessageProperties());
 
@@ -151,4 +152,29 @@ void setDeliveryModeIfNull() {
 		assertThat(this.message.getMessageProperties().getDeliveryMode()).isEqualTo(MessageDeliveryMode.NON_PERSISTENT);
 	}
 
+	@Test
+	void dynamicExRk() {
+		this.recoverer = new RepublishMessageRecoverer(this.amqpTemplate,
+				new SpelExpressionParser().parseExpression("messageProperties.headers.get('errorExchange')"),
+				new SpelExpressionParser().parseExpression("messageProperties.headers.get('errorRK')"));
+		this.message.getMessageProperties().setHeader("errorExchange", "ex");
+		this.message.getMessageProperties().setHeader("errorRK", "rk");
+
+		this.recoverer.recover(this.message, this.cause);
+
+		verify(this.amqpTemplate).send("ex", "rk", this.message);
+	}
+
+	@Test
+	void dynamicRk() {
+		this.recoverer = new RepublishMessageRecoverer(this.amqpTemplate, null,
+				new SpelExpressionParser().parseExpression("messageProperties.headers.get('errorRK')"));
+		this.message.getMessageProperties().setHeader("errorExchange", "ex");
+		this.message.getMessageProperties().setHeader("errorRK", "rk");
+
+		this.recoverer.recover(this.message, this.cause);
+
+		verify(this.amqpTemplate).send("rk", this.message);
+	}
+
 }

src/reference/asciidoc/amqp.adoc

@@ -6783,7 +6783,7 @@ The default `MessageRecoverer` consumes the errant message and emits a `WARN` me
 
 Starting with version 1.3, a new `RepublishMessageRecoverer` is provided, to allow publishing of failed messages after retries are exhausted.
 
-When a recoverer consumes the final exception, the message is ack'd and is not sent to the dead letter exchange, if any.
+When a recoverer consumes the final exception, the message is ack'd and is not sent to the dead letter exchange by the broker, if configured.
 
 NOTE: When `RepublishMessageRecoverer` is used on the consumer side, the received message has `deliveryMode` in the `receivedDeliveryMode` message property.
 In this case the `deliveryMode` is `null`.
@@ -6834,6 +6834,9 @@ Starting with versions 2.1.13, 2.2.3, the exception message is included in this
 * if the stack trace is small, the message will be truncated (plus `...`) to fit in the available bytes (but the message within the stack trace itself is truncated to 97 bytes plus `...`).
 
 Whenever a truncation of any kind occurs, the original exception will be logged to retain the complete information.
+The evaluation is performed after the headers are enhanced so information such as the exception type can be used in the expressions.
+
+Starting with version 2.4.8, the error exchange and routing key can be provided as SpEL expressions, with the `Message` being the root object for the evaluation.
 
 Starting with version 2.3.3, a new subclass `RepublishMessageRecovererWithConfirms` is provided; this supports both styles of publisher confirms and will wait for the confirmation before returning (or throw an exception if not confirmed or the message is returned).