GH-871: Add missing @Nullable

Resolves #871

* Add missing `@Nullable`

Relates #871

* Fixup order of imports

spring-amqp/src/main/java/org/springframework/amqp/core/AmqpAdmin.java

@@ -18,6 +18,8 @@
 
 import java.util.Properties;
 
+import org.springframework.lang.Nullable;
+
 
 /**
  * Specifies a basic set of portable AMQP administrative operations for AMQP > 0.9.
@@ -50,13 +52,15 @@ public interface AmqpAdmin {
 	 *
 	 * @return The queue.
 	 */
+	@Nullable
 	Queue declareQueue();
 
 	/**
 	 * Declare the given queue.
 	 * @param queue the queue to declare.
 	 * @return the name of the queue.
 	 */
+	@Nullable
 	String declareQueue(Queue queue);
 
 	/**
@@ -111,6 +115,7 @@ public interface AmqpAdmin {
 	 * @param queueName the name of the queue.
 	 * @return the properties or null if the queue doesn't exist.
 	 */
+	@Nullable
 	Properties getQueueProperties(String queueName);
 
 	/**

spring-amqp/src/main/java/org/springframework/amqp/core/AmqpTemplate.java

@@ -19,6 +19,7 @@
 import org.springframework.amqp.AmqpException;
 import org.springframework.amqp.support.converter.MessageConverter;
 import org.springframework.core.ParameterizedTypeReference;
+import org.springframework.lang.Nullable;
 
 /**
  * Specifies a basic set of AMQP operations.
@@ -141,6 +142,7 @@ void convertAndSend(String exchange, String routingKey, Object message, MessageP
 	 * @return a message or null if there is none waiting
 	 * @throws AmqpException if there is a problem
 	 */
+	@Nullable
 	Message receive() throws AmqpException;
 
 	/**
@@ -151,6 +153,7 @@ void convertAndSend(String exchange, String routingKey, Object message, MessageP
 	 * @return a message or null if there is none waiting
 	 * @throws AmqpException if there is a problem
 	 */
+	@Nullable
 	Message receive(String queueName) throws AmqpException;
 
 	/**
@@ -164,6 +167,7 @@ void convertAndSend(String exchange, String routingKey, Object message, MessageP
 	 * @throws AmqpException if there is a problem
 	 * @since 1.6
 	 */
+	@Nullable
 	Message receive(long timeoutMillis) throws AmqpException;
 
 	/**
@@ -178,6 +182,7 @@ void convertAndSend(String exchange, String routingKey, Object message, MessageP
 	 * @throws AmqpException if there is a problem
 	 * @since 1.6
 	 */
+	@Nullable
 	Message receive(String queueName, long timeoutMillis) throws AmqpException;
 
 	// receive methods with conversion
@@ -189,6 +194,7 @@ void convertAndSend(String exchange, String routingKey, Object message, MessageP
 	 * @return a message or null if there is none waiting
 	 * @throws AmqpException if there is a problem
 	 */
+	@Nullable
 	Object receiveAndConvert() throws AmqpException;
 
 	/**
@@ -199,6 +205,7 @@ void convertAndSend(String exchange, String routingKey, Object message, MessageP
 	 * @return a message or null if there is none waiting
 	 * @throws AmqpException if there is a problem
 	 */
+	@Nullable
 	Object receiveAndConvert(String queueName) throws AmqpException;
 
 	/**
@@ -213,6 +220,7 @@ void convertAndSend(String exchange, String routingKey, Object message, MessageP
 	 * @throws AmqpException if there is a problem
 	 * @since 1.6
 	 */
+	@Nullable
 	Object receiveAndConvert(long timeoutMillis) throws AmqpException;
 
 	/**
@@ -228,6 +236,7 @@ void convertAndSend(String exchange, String routingKey, Object message, MessageP
 	 * @throws AmqpException if there is a problem
 	 * @since 1.6
 	 */
+	@Nullable
 	Object receiveAndConvert(String queueName, long timeoutMillis) throws AmqpException;
 
 	/**
@@ -241,6 +250,7 @@ void convertAndSend(String exchange, String routingKey, Object message, MessageP
 	 * @throws AmqpException if there is a problem.
 	 * @since 2.0
 	 */
+	@Nullable
 	<T> T receiveAndConvert(ParameterizedTypeReference<T> type) throws AmqpException;
 
 	/**
@@ -255,6 +265,7 @@ void convertAndSend(String exchange, String routingKey, Object message, MessageP
 	 * @throws AmqpException if there is a problem
 	 * @since 2.0
 	 */
+	@Nullable
 	<T> T receiveAndConvert(String queueName, ParameterizedTypeReference<T> type) throws AmqpException;
 
 	/**
@@ -272,6 +283,7 @@ void convertAndSend(String exchange, String routingKey, Object message, MessageP
 	 * @throws AmqpException if there is a problem
 	 * @since 2.0
 	 */
+	@Nullable
 	<T> T receiveAndConvert(long timeoutMillis, ParameterizedTypeReference<T> type) throws AmqpException;
 
 	/**
@@ -290,6 +302,7 @@ void convertAndSend(String exchange, String routingKey, Object message, MessageP
 	 * @throws AmqpException if there is a problem
 	 * @since 2.0
 	 */
+	@Nullable
 	<T> T receiveAndConvert(String queueName, long timeoutMillis, ParameterizedTypeReference<T> type)
 			throws AmqpException;
 
@@ -410,6 +423,7 @@ <R, S> boolean receiveAndReply(String queueName, ReceiveAndReplyCallback<R, S> c
 	 * @return the response if there is one
 	 * @throws AmqpException if there is a problem
 	 */
+	@Nullable
 	Message sendAndReceive(Message message) throws AmqpException;
 
 	/**
@@ -422,6 +436,7 @@ <R, S> boolean receiveAndReply(String queueName, ReceiveAndReplyCallback<R, S> c
 	 * @return the response if there is one
 	 * @throws AmqpException if there is a problem
 	 */
+	@Nullable
 	Message sendAndReceive(String routingKey, Message message) throws AmqpException;
 
 	/**
@@ -436,6 +451,7 @@ <R, S> boolean receiveAndReply(String queueName, ReceiveAndReplyCallback<R, S> c
 	 * @return the response if there is one
 	 * @throws AmqpException if there is a problem
 	 */
+	@Nullable
 	Message sendAndReceive(String exchange, String routingKey, Message message) throws AmqpException;
 
 	// send and receive methods with conversion
@@ -450,6 +466,7 @@ <R, S> boolean receiveAndReply(String queueName, ReceiveAndReplyCallback<R, S> c
 	 * @return the response if there is one
 	 * @throws AmqpException if there is a problem
 	 */
+	@Nullable
 	Object convertSendAndReceive(Object message) throws AmqpException;
 
 	/**
@@ -463,6 +480,7 @@ <R, S> boolean receiveAndReply(String queueName, ReceiveAndReplyCallback<R, S> c
 	 * @return the response if there is one
 	 * @throws AmqpException if there is a problem
 	 */
+	@Nullable
 	Object convertSendAndReceive(String routingKey, Object message) throws AmqpException;
 
 	/**
@@ -477,6 +495,7 @@ <R, S> boolean receiveAndReply(String queueName, ReceiveAndReplyCallback<R, S> c
 	 * @return the response if there is one
 	 * @throws AmqpException if there is a problem
 	 */
+	@Nullable
 	Object convertSendAndReceive(String exchange, String routingKey, Object message) throws AmqpException;
 
 	/**
@@ -490,6 +509,7 @@ <R, S> boolean receiveAndReply(String queueName, ReceiveAndReplyCallback<R, S> c
 	 * @return the response if there is one
 	 * @throws AmqpException if there is a problem
 	 */
+	@Nullable
 	Object convertSendAndReceive(Object message, MessagePostProcessor messagePostProcessor) throws AmqpException;
 
 	/**
@@ -504,6 +524,7 @@ <R, S> boolean receiveAndReply(String queueName, ReceiveAndReplyCallback<R, S> c
 	 * @return the response if there is one
 	 * @throws AmqpException if there is a problem
 	 */
+	@Nullable
 	Object convertSendAndReceive(String routingKey, Object message, MessagePostProcessor messagePostProcessor)
 			throws AmqpException;
 
@@ -520,6 +541,7 @@ Object convertSendAndReceive(String routingKey, Object message, MessagePostProce
 	 * @return the response if there is one
 	 * @throws AmqpException if there is a problem
 	 */
+	@Nullable
 	Object convertSendAndReceive(String exchange, String routingKey, Object message,
 			MessagePostProcessor messagePostProcessor) throws AmqpException;
 
@@ -537,6 +559,7 @@ Object convertSendAndReceive(String exchange, String routingKey, Object message,
 	 * @throws AmqpException if there is a problem.
 	 * @since 2.0
 	 */
+	@Nullable
 	<T> T convertSendAndReceiveAsType(Object message, ParameterizedTypeReference<T> responseType)
 			throws AmqpException;
 
@@ -554,6 +577,7 @@ <T> T convertSendAndReceiveAsType(Object message, ParameterizedTypeReference<T>
 	 * @throws AmqpException if there is a problem
 	 * @since 2.0
 	 */
+	@Nullable
 	<T> T convertSendAndReceiveAsType(String routingKey, Object message,
 			ParameterizedTypeReference<T> responseType) throws AmqpException;
 
@@ -572,6 +596,7 @@ <T> T convertSendAndReceiveAsType(String routingKey, Object message,
 	 * @throws AmqpException if there is a problem
 	 * @since 2.0
 	 */
+	@Nullable
 	<T> T convertSendAndReceiveAsType(String exchange, String routingKey, Object message,
 			ParameterizedTypeReference<T> responseType) throws AmqpException;
 
@@ -589,6 +614,7 @@ <T> T convertSendAndReceiveAsType(String exchange, String routingKey, Object mes
 	 * @throws AmqpException if there is a problem
 	 * @since 2.0
 	 */
+	@Nullable
 	<T> T convertSendAndReceiveAsType(Object message, MessagePostProcessor messagePostProcessor,
 			ParameterizedTypeReference<T> responseType) throws AmqpException;
 
@@ -607,6 +633,7 @@ <T> T convertSendAndReceiveAsType(Object message, MessagePostProcessor messagePo
 	 * @throws AmqpException if there is a problem
 	 * @since 2.0
 	 */
+	@Nullable
 	<T> T convertSendAndReceiveAsType(String routingKey, Object message,
 			MessagePostProcessor messagePostProcessor, ParameterizedTypeReference<T> responseType)
 			throws AmqpException;
@@ -627,6 +654,7 @@ <T> T convertSendAndReceiveAsType(String routingKey, Object message,
 	 * @throws AmqpException if there is a problem
 	 * @since 2.0
 	 */
+	@Nullable
 	<T> T convertSendAndReceiveAsType(String exchange, String routingKey, Object message,
 			MessagePostProcessor messagePostProcessor, ParameterizedTypeReference<T> responseType)
 			throws AmqpException;

spring-rabbit/src/main/java/org/springframework/amqp/rabbit/core/ChannelCallback.java

@@ -16,6 +16,8 @@
 
 package org.springframework.amqp.rabbit.core;
 
+import org.springframework.lang.Nullable;
+
 import com.rabbitmq.client.Channel;
 
 /**
@@ -36,6 +38,7 @@ public interface ChannelCallback<T> {
 	 * @return The result.
 	 * @throws Exception Not sure what else Rabbit Throws
 	 */
+	@Nullable
 	T doInRabbit(Channel channel) throws Exception; // NOSONAR user code might throw anything; cannot change
 
 }

spring-rabbit/src/main/java/org/springframework/amqp/rabbit/core/RabbitAdmin.java

@@ -263,6 +263,7 @@ public boolean deleteExchange(final String exchangeName) {
 	@Override
 	@ManagedOperation(description =
 			"Declare a queue on the broker (this operation is not available remotely)")
+	@Nullable
 	public String declareQueue(final Queue queue) {
 		try {
 			return this.rabbitTemplate.execute(channel -> {
@@ -388,6 +389,7 @@ public void removeBinding(final Binding binding) {
 	 */
 	@Override
 	@ManagedOperation(description = "Get queue name, message count and consumer count")
+	@Nullable
 	public Properties getQueueProperties(final String queueName) {
 		Assert.hasText(queueName, "'queueName' cannot be null or empty");
 		return this.rabbitTemplate.execute(channel -> {
@@ -434,7 +436,7 @@ public Properties getQueueProperties(final String queueName) {
 	 * @param retryTemplate the retry template.
 	 * @since 1.7.8
 	 */
-	public void setRetryTemplate(RetryTemplate retryTemplate) {
+	public void setRetryTemplate(@Nullable RetryTemplate retryTemplate) {
 		this.retryTemplate = retryTemplate;
 		if (retryTemplate == null) {
 			this.retryDisabled = true;

spring-rabbit/src/main/java/org/springframework/amqp/rabbit/core/RabbitTemplate.java

@@ -1013,11 +1013,13 @@ public void convertAndSend(String exchange, String routingKey, final Object mess
 	}
 
 	@Override
+	@Nullable
 	public Message receive() throws AmqpException {
 		return this.receive(getRequiredQueue());
 	}
 
 	@Override
+	@Nullable
 	public Message receive(String queueName) {
 		if (this.receiveTimeout == 0) {
 			return doReceiveNoWait(queueName);
@@ -1033,6 +1035,7 @@ public Message receive(String queueName) {
 	 * @return The message, or null if none immediately available.
 	 * @since 1.5
 	 */
+	@Nullable
 	protected Message doReceiveNoWait(final String queueName) {
 		Message message = execute(channel -> {
 			GetResponse response = channel.basicGet(queueName, !isChannelTransacted());
@@ -1934,11 +1937,13 @@ public Boolean isMandatoryFor(final Message message) {
 	}
 
 	@Override
+	@Nullable
 	public <T> T execute(ChannelCallback<T> action) {
 		return execute(action, getConnectionFactory());
 	}
 
 	@SuppressWarnings(UNCHECKED)
+	@Nullable
 	private <T> T execute(final ChannelCallback<T> action, final ConnectionFactory connectionFactory) {
 		if (this.retryTemplate != null) {
 			try {
@@ -1958,7 +1963,7 @@ private <T> T execute(final ChannelCallback<T> action, final ConnectionFactory c
 		}
 	}
 
-
+	@Nullable
 	private <T> T doExecute(ChannelCallback<T> action, ConnectionFactory connectionFactory) { // NOSONAR complexity
 		Assert.notNull(action, "Callback object must not be null");
 		Channel channel = null;