GH-1560: Caching CF toString() Improvements

Resolves https://github.com/spring-projects/spring-amqp/issues/1560

Use address resolution hierarchy to determine destination host(s).

spring-rabbit/src/main/java/org/springframework/amqp/rabbit/connection/AbstractConnectionFactory.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2022 the original author or authors.
+ * Copyright 2002-2023 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.
@@ -303,6 +303,7 @@ public abstract class AbstractConnectionFactory implements ConnectionFactory, Di
 	}
 
 	@Override
+	@Nullable
 	public String getHost() {
 		return this.rabbitConnectionFactory.getHost();
 	}
@@ -354,6 +355,11 @@ public abstract class AbstractConnectionFactory implements ConnectionFactory, Di
 		this.addresses = null;
 	}
 
+	@Nullable
+	protected List<Address> getAddresses() throws IOException {
+		return this.addressResolver != null ? this.addressResolver.getAddresses() : this.addresses;
+	}
+
 	/**
 	 * A composite connection listener to be used by subclasses when creating and closing connections.
 	 *

spring-rabbit/src/main/java/org/springframework/amqp/rabbit/connection/CachingConnectionFactory.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2022 the original author or authors.
+ * Copyright 2002-2023 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.
@@ -58,6 +58,7 @@ import org.springframework.util.Assert;
 import org.springframework.util.ObjectUtils;
 import org.springframework.util.StringUtils;
 
+import com.rabbitmq.client.Address;
 import com.rabbitmq.client.AlreadyClosedException;
 import com.rabbitmq.client.BlockedListener;
 import com.rabbitmq.client.Channel;
@@ -1003,8 +1004,21 @@ public class CachingConnectionFactory extends AbstractConnectionFactory
 
 	@Override
 	public String toString() {
-		return "CachingConnectionFactory [channelCacheSize=" + this.channelCacheSize + ", host=" + getHost()
-				+ ", port=" + getPort() + ", active=" + this.active
+		String host = getHost();
+		int port = getPort();
+		List<Address> addresses = null;
+		try {
+			addresses = getAddresses();
+		}
+		catch (IOException ex) {
+			host = "AddressResolver threw exception: " + ex.getMessage();
+		}
+		return "CachingConnectionFactory [channelCacheSize=" + this.channelCacheSize
+				+ (addresses != null
+					? ", addresses=" + addresses
+					: (host != null ? ", host=" + host : "")
+						+ (port > 0 ? ", port=" + port : ""))
+				+ ", active=" + this.active
 				+ " " + super.toString() + "]";
 	}
 

spring-rabbit/src/main/java/org/springframework/amqp/rabbit/connection/ConnectionFactory.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2022 the original author or authors.
+ * Copyright 2002-2023 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 @@ public interface ConnectionFactory {
 
 	Connection createConnection() throws AmqpException;
 
+	@Nullable
 	String getHost();
 
 	int getPort();

spring-rabbit/src/test/java/org/springframework/amqp/rabbit/connection/CachingConnectionFactoryTests.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2022 the original author or authors.
+ * Copyright 2002-2023 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.
@@ -104,6 +104,28 @@ public class CachingConnectionFactoryTests extends AbstractConnectionFactoryTest
 		return ccf;
 	}
 
+	@Test
+	void stringRepresentation() {
+		CachingConnectionFactory ccf = new CachingConnectionFactory("someHost", 1234);
+		assertThat(ccf.toString()).contains(", host=someHost, port=1234")
+				.doesNotContain("addresses");
+		ccf.setAddresses("h1:1234,h2:1235");
+		assertThat(ccf.toString()).contains(", addresses=[h1:1234, h2:1235]")
+				.doesNotContain("host")
+				.doesNotContain("port");
+		ccf.setAddressResolver(() -> List.of(new Address("h3", 1236), new Address("h4", 1237)));
+		assertThat(ccf.toString()).contains(", addresses=[h3:1236, h4:1237]")
+				.doesNotContain("host")
+				.doesNotContain("port");
+		ccf.setAddressResolver(() ->  {
+			throw new IOException("test");
+		});
+		ccf.setPort(0);
+		assertThat(ccf.toString()).contains(", host=AddressResolver threw exception: test")
+				.doesNotContain("addresses")
+				.doesNotContain("port");
+	}
+
 	@Test
 	public void testWithConnectionFactoryDefaults() throws Exception {
 		com.rabbitmq.client.ConnectionFactory mockConnectionFactory = mock(com.rabbitmq.client.ConnectionFactory.class);