Make getters and setters null-safety consistent

This commit ensure that null-safety is consistent between
getters and setters in order to be able to provide beans
with properties with a common type when type safety is
taken in account like with Kotlin.

It also add a few missing property level @Nullable
annotations.

Issue: SPR-15792

spring-messaging/src/main/java/org/springframework/messaging/converter/MarshallingMessageConverter.java

@@ -92,7 +92,7 @@ public class MarshallingMessageConverter extends AbstractMessageConverter {
 	/**
 	 * Set the {@link Marshaller} to be used by this message converter.
 	 */
-	public void setMarshaller(Marshaller marshaller) {
+	public void setMarshaller(@Nullable Marshaller marshaller) {
 		this.marshaller = marshaller;
 	}
 
@@ -107,7 +107,7 @@ public class MarshallingMessageConverter extends AbstractMessageConverter {
 	/**
 	 * Set the {@link Unmarshaller} to be used by this message converter.
 	 */
-	public void setUnmarshaller(Unmarshaller unmarshaller) {
+	public void setUnmarshaller(@Nullable Unmarshaller unmarshaller) {
 		this.unmarshaller = unmarshaller;
 	}
 

spring-messaging/src/main/java/org/springframework/messaging/core/AbstractDestinationResolvingMessagingTemplate.java

@@ -51,8 +51,7 @@ public abstract class AbstractDestinationResolvingMessagingTemplate<D> extends A
 	 * require resolving a destination name will raise an {@link IllegalArgumentException}.
 	 * @param destinationResolver the destination resolver to use
 	 */
-	public void setDestinationResolver(DestinationResolver<D> destinationResolver) {
-		Assert.notNull(destinationResolver, "'destinationResolver' is required");
+	public void setDestinationResolver(@Nullable DestinationResolver<D> destinationResolver) {
 		this.destinationResolver = destinationResolver;
 	}
 

spring-messaging/src/main/java/org/springframework/messaging/core/AbstractMessageSendingTemplate.java

@@ -63,7 +63,7 @@ public abstract class AbstractMessageSendingTemplate<D> implements MessageSendin
 	 * a destination argument. If a default destination is not configured, send methods
 	 * without a destination argument will raise an exception if invoked.
 	 */
-	public void setDefaultDestination(D defaultDestination) {
+	public void setDefaultDestination(@Nullable D defaultDestination) {
 		this.defaultDestination = defaultDestination;
 	}
 

spring-messaging/src/main/java/org/springframework/messaging/handler/invocation/AbstractMethodMessageHandler.java

@@ -96,6 +96,7 @@ public abstract class AbstractMethodMessageHandler<T>
 	private final HandlerMethodReturnValueHandlerComposite returnValueHandlers =
 			new HandlerMethodReturnValueHandlerComposite();
 
+	@Nullable
 	private ApplicationContext applicationContext;
 
 	private final Map<T, HandlerMethod> handlerMethods = new LinkedHashMap<>(64);
@@ -211,7 +212,7 @@ public abstract class AbstractMethodMessageHandler<T>
 	}
 
 	@Override
-	public void setApplicationContext(ApplicationContext applicationContext) {
+	public void setApplicationContext(@Nullable ApplicationContext applicationContext) {
 		this.applicationContext = applicationContext;
 	}
 

spring-messaging/src/main/java/org/springframework/messaging/simp/SimpMessageHeaderAccessor.java

@@ -121,8 +121,7 @@ public class SimpMessageHeaderAccessor extends NativeMessageHeaderAccessor {
 		return (SimpMessageType) getHeader(MESSAGE_TYPE_HEADER);
 	}
 
-	public void setDestination(String destination) {
-		Assert.notNull(destination, "Destination must not be null");
+	public void setDestination(@Nullable String destination) {
 		setHeader(DESTINATION_HEADER, destination);
 	}
 
@@ -155,7 +154,7 @@ public class SimpMessageHeaderAccessor extends NativeMessageHeaderAccessor {
 	/**
 	 * A static alternative for access to the session attributes header.
 	 */
-	public void setSessionAttributes(Map<String, Object> attributes) {
+	public void setSessionAttributes(@Nullable Map<String, Object> attributes) {
 		setHeader(SESSION_ATTRIBUTES, attributes);
 	}
 
@@ -168,7 +167,7 @@ public class SimpMessageHeaderAccessor extends NativeMessageHeaderAccessor {
 		return (Map<String, Object>) getHeader(SESSION_ATTRIBUTES);
 	}
 
-	public void setUser(Principal principal) {
+	public void setUser(@Nullable Principal principal) {
 		setHeader(USER_HEADER, principal);
 	}
 

spring-messaging/src/main/java/org/springframework/messaging/simp/SimpMessagingTemplate.java

@@ -111,7 +111,7 @@ public class SimpMessagingTemplate extends AbstractMessageSendingTemplate<String
 	 * messages created through the {@code SimpMessagingTemplate}.
 	 * <p>By default, this property is not set.
 	 */
-	public void setHeaderInitializer(MessageHeaderInitializer headerInitializer) {
+	public void setHeaderInitializer(@Nullable MessageHeaderInitializer headerInitializer) {
 		this.headerInitializer = headerInitializer;
 	}
 

spring-messaging/src/main/java/org/springframework/messaging/simp/annotation/support/SendToMethodReturnValueHandler.java

@@ -121,7 +121,7 @@ public class SendToMethodReturnValueHandler implements HandlerMethodReturnValueH
 	 * messages sent to the client outbound channel.
 	 * <p>By default this property is not set.
 	 */
-	public void setHeaderInitializer(MessageHeaderInitializer headerInitializer) {
+	public void setHeaderInitializer(@Nullable MessageHeaderInitializer headerInitializer) {
 		this.headerInitializer = headerInitializer;
 	}
 

spring-messaging/src/main/java/org/springframework/messaging/simp/annotation/support/SimpAnnotationMethodMessageHandler.java

@@ -234,7 +234,7 @@ public class SimpAnnotationMethodMessageHandler extends AbstractMethodMessageHan
 	 * @see org.springframework.validation.annotation.Validated
 	 * @see PayloadArgumentResolver
 	 */
-	public void setValidator(Validator validator) {
+	public void setValidator(@Nullable Validator validator) {
 		this.validator = validator;
 	}
 
@@ -249,7 +249,7 @@ public class SimpAnnotationMethodMessageHandler extends AbstractMethodMessageHan
 	 * that send messages from controller return values.
 	 * <p>By default, this property is not set.
 	 */
-	public void setHeaderInitializer(MessageHeaderInitializer headerInitializer) {
+	public void setHeaderInitializer(@Nullable MessageHeaderInitializer headerInitializer) {
 		this.headerInitializer = headerInitializer;
 	}
 

spring-messaging/src/main/java/org/springframework/messaging/simp/annotation/support/SubscriptionMethodReturnValueHandler.java

@@ -63,6 +63,7 @@ public class SubscriptionMethodReturnValueHandler implements HandlerMethodReturn
 
 	private final MessageSendingOperations<String> messagingTemplate;
 
+	@Nullable
 	private MessageHeaderInitializer headerInitializer;
 
 
@@ -82,7 +83,7 @@ public class SubscriptionMethodReturnValueHandler implements HandlerMethodReturn
 	 * messages sent to the client outbound channel.
 	 * <p>By default this property is not set.
 	 */
-	public void setHeaderInitializer(MessageHeaderInitializer headerInitializer) {
+	public void setHeaderInitializer(@Nullable MessageHeaderInitializer headerInitializer) {
 		this.headerInitializer = headerInitializer;
 	}
 

spring-messaging/src/main/java/org/springframework/messaging/simp/broker/AbstractBrokerMessageHandler.java

@@ -129,7 +129,7 @@ public abstract class AbstractBrokerMessageHandler
 	}
 
 	@Override
-	public void setApplicationEventPublisher(ApplicationEventPublisher publisher) {
+	public void setApplicationEventPublisher(@Nullable ApplicationEventPublisher publisher) {
 		this.eventPublisher = publisher;
 	}
 

spring-messaging/src/main/java/org/springframework/messaging/simp/broker/SimpleBrokerMessageHandler.java

@@ -157,10 +157,9 @@ public class SimpleBrokerMessageHandler extends AbstractBrokerMessageHandler {
 	 * <p>By default this is not set.
 	 * @since 4.2
 	 */
-	public void setTaskScheduler(TaskScheduler taskScheduler) {
-		Assert.notNull(taskScheduler, "TaskScheduler must not be null");
+	public void setTaskScheduler(@Nullable TaskScheduler taskScheduler) {
 		this.taskScheduler = taskScheduler;
-		if (this.heartbeatValue == null) {
+		if (taskScheduler != null && this.heartbeatValue == null) {
 			this.heartbeatValue = new long[] {10000, 10000};
 		}
 	}
@@ -183,8 +182,8 @@ public class SimpleBrokerMessageHandler extends AbstractBrokerMessageHandler {
 	 * (in milliseconds).
 	 * @since 4.2
 	 */
-	public void setHeartbeatValue(long[] heartbeat) {
-		if (heartbeat.length != 2 || heartbeat[0] < 0 || heartbeat[1] < 0) {
+	public void setHeartbeatValue(@Nullable long[] heartbeat) {
+		if (heartbeat != null && (heartbeat.length != 2 || heartbeat[0] < 0 || heartbeat[1] < 0)) {
 			throw new IllegalArgumentException("Invalid heart-beat: " + Arrays.toString(heartbeat));
 		}
 		this.heartbeatValue = heartbeat;
@@ -205,7 +204,7 @@ public class SimpleBrokerMessageHandler extends AbstractBrokerMessageHandler {
 	 * <p>By default this property is not set.
 	 * @since 4.1
 	 */
-	public void setHeaderInitializer(MessageHeaderInitializer headerInitializer) {
+	public void setHeaderInitializer(@Nullable MessageHeaderInitializer headerInitializer) {
 		this.headerInitializer = headerInitializer;
 	}
 

spring-messaging/src/main/java/org/springframework/messaging/simp/config/AbstractMessageBrokerConfiguration.java

@@ -112,7 +112,7 @@ public abstract class AbstractMessageBrokerConfiguration implements ApplicationC
 
 
 	@Override
-	public void setApplicationContext(ApplicationContext applicationContext) {
+	public void setApplicationContext(@Nullable ApplicationContext applicationContext) {
 		this.applicationContext = applicationContext;
 	}
 

spring-messaging/src/main/java/org/springframework/messaging/simp/stomp/StompBrokerRelayMessageHandler.java

@@ -325,7 +325,7 @@ public class StompBrokerRelayMessageHandler extends AbstractBrokerMessageHandler
 	 * providing the cloud-based STOMP service.
 	 * <p>By default this property is not set.
 	 */
-	public void setVirtualHost(String virtualHost) {
+	public void setVirtualHost(@Nullable String virtualHost) {
 		this.virtualHost = virtualHost;
 	}
 
@@ -341,7 +341,7 @@ public class StompBrokerRelayMessageHandler extends AbstractBrokerMessageHandler
 	 * Configure a TCP client for managing TCP connections to the STOMP broker.
 	 * <p>By default {@link ReactorNettyTcpClient} is used.
 	 */
-	public void setTcpClient(TcpOperations<byte[]> tcpClient) {
+	public void setTcpClient(@Nullable TcpOperations<byte[]> tcpClient) {
 		this.tcpClient = tcpClient;
 	}
 
@@ -361,7 +361,7 @@ public class StompBrokerRelayMessageHandler extends AbstractBrokerMessageHandler
 	 * are sent to the client outbound message channel.
 	 * <p>By default this property is not set.
 	 */
-	public void setHeaderInitializer(MessageHeaderInitializer headerInitializer) {
+	public void setHeaderInitializer(@Nullable MessageHeaderInitializer headerInitializer) {
 		this.headerInitializer = headerInitializer;
 	}
 

spring-messaging/src/main/java/org/springframework/messaging/simp/stomp/StompClientSupport.java

@@ -43,6 +43,7 @@ public abstract class StompClientSupport {
 
 	private MessageConverter messageConverter = new SimpleMessageConverter();
 
+	@Nullable
 	private TaskScheduler taskScheduler;
 
 	private long[] defaultHeartbeat = new long[] {10000, 10000};
@@ -76,7 +77,7 @@ public abstract class StompClientSupport {
 	 * Receipts however, if needed, do require a TaskScheduler to be configured.
 	 * <p>By default, this is not set.
 	 */
-	public void setTaskScheduler(TaskScheduler taskScheduler) {
+	public void setTaskScheduler(@Nullable TaskScheduler taskScheduler) {
 		this.taskScheduler = taskScheduler;
 	}
 

spring-messaging/src/main/java/org/springframework/messaging/simp/stomp/StompDecoder.java

@@ -61,7 +61,7 @@ public class StompDecoder {
 	 * Configure a {@link MessageHeaderInitializer} to apply to the headers of
 	 * {@link Message}s from decoded STOMP frames.
 	 */
-	public void setHeaderInitializer(MessageHeaderInitializer headerInitializer) {
+	public void setHeaderInitializer(@Nullable MessageHeaderInitializer headerInitializer) {
 		this.headerInitializer = headerInitializer;
 	}
 

spring-messaging/src/main/java/org/springframework/messaging/simp/stomp/StompHeaderAccessor.java

@@ -246,7 +246,7 @@ public class StompHeaderAccessor extends SimpMessageHeaderAccessor {
 		return (rawValue != null ? StringUtils.commaDelimitedListToSet(rawValue) : Collections.emptySet());
 	}
 
-	public void setHost(String host) {
+	public void setHost(@Nullable String host) {
 		setNativeHeader(STOMP_HOST_HEADER, host);
 	}
 
@@ -302,7 +302,7 @@ public class StompHeaderAccessor extends SimpMessageHeaderAccessor {
 		setNativeHeader(STOMP_HEARTBEAT_HEADER, cx + "," + cy);
 	}
 
-	public void setAck(String ack) {
+	public void setAck(@Nullable String ack) {
 		setNativeHeader(STOMP_ACK_HEADER, ack);
 	}
 
@@ -311,7 +311,7 @@ public class StompHeaderAccessor extends SimpMessageHeaderAccessor {
 		return getFirstNativeHeader(STOMP_ACK_HEADER);
 	}
 
-	public void setNack(String nack) {
+	public void setNack(@Nullable String nack) {
 		setNativeHeader(STOMP_NACK_HEADER, nack);
 	}
 
@@ -320,7 +320,7 @@ public class StompHeaderAccessor extends SimpMessageHeaderAccessor {
 		return getFirstNativeHeader(STOMP_NACK_HEADER);
 	}
 
-	public void setLogin(String login) {
+	public void setLogin(@Nullable String login) {
 		setNativeHeader(STOMP_LOGIN_HEADER, login);
 	}
 
@@ -329,7 +329,7 @@ public class StompHeaderAccessor extends SimpMessageHeaderAccessor {
 		return getFirstNativeHeader(STOMP_LOGIN_HEADER);
 	}
 
-	public void setPasscode(String passcode) {
+	public void setPasscode(@Nullable String passcode) {
 		setNativeHeader(STOMP_PASSCODE_HEADER, passcode);
 		protectPasscode();
 	}
@@ -351,7 +351,7 @@ public class StompHeaderAccessor extends SimpMessageHeaderAccessor {
 		return (credentials != null ? credentials.passcode : null);
 	}
 
-	public void setReceiptId(String receiptId) {
+	public void setReceiptId(@Nullable String receiptId) {
 		setNativeHeader(STOMP_RECEIPT_ID_HEADER, receiptId);
 	}
 
@@ -360,7 +360,7 @@ public class StompHeaderAccessor extends SimpMessageHeaderAccessor {
 		return getFirstNativeHeader(STOMP_RECEIPT_ID_HEADER);
 	}
 
-	public void setReceipt(String receiptId) {
+	public void setReceipt(@Nullable String receiptId) {
 		setNativeHeader(STOMP_RECEIPT_HEADER, receiptId);
 	}
 
@@ -374,7 +374,7 @@ public class StompHeaderAccessor extends SimpMessageHeaderAccessor {
 		return getFirstNativeHeader(STOMP_MESSAGE_HEADER);
 	}
 
-	public void setMessage(String content) {
+	public void setMessage(@Nullable String content) {
 		setNativeHeader(STOMP_MESSAGE_HEADER, content);
 	}
 
@@ -383,7 +383,7 @@ public class StompHeaderAccessor extends SimpMessageHeaderAccessor {
 		return getFirstNativeHeader(STOMP_MESSAGE_ID_HEADER);
 	}
 
-	public void setMessageId(String id) {
+	public void setMessageId(@Nullable String id) {
 		setNativeHeader(STOMP_MESSAGE_ID_HEADER, id);
 	}
 
@@ -392,7 +392,7 @@ public class StompHeaderAccessor extends SimpMessageHeaderAccessor {
 		return getFirstNativeHeader(STOMP_VERSION_HEADER);
 	}
 
-	public void setVersion(String version) {
+	public void setVersion(@Nullable String version) {
 		setNativeHeader(STOMP_VERSION_HEADER, version);
 	}
 

spring-messaging/src/main/java/org/springframework/messaging/simp/stomp/StompHeaders.java

@@ -126,10 +126,15 @@ public class StompHeaders implements MultiValueMap<String, String>, Serializable
 	 * Set the content-type header.
 	 * Applies to the SEND, MESSAGE, and ERROR frames.
 	 */
-	public void setContentType(MimeType mimeType) {
-		Assert.isTrue(!mimeType.isWildcardType(), "'Content-Type' cannot contain wildcard type '*'");
-		Assert.isTrue(!mimeType.isWildcardSubtype(), "'Content-Type' cannot contain wildcard subtype '*'");
-		set(CONTENT_TYPE, mimeType.toString());
+	public void setContentType(@Nullable MimeType mimeType) {
+		if (mimeType != null) {
+			Assert.isTrue(!mimeType.isWildcardType(), "'Content-Type' cannot contain wildcard type '*'");
+			Assert.isTrue(!mimeType.isWildcardSubtype(), "'Content-Type' cannot contain wildcard subtype '*'");
+			set(CONTENT_TYPE, mimeType.toString());
+		}
+		else {
+			set(CONTENT_TYPE, null);
+		}
 	}
 
 	/**
@@ -161,7 +166,7 @@ public class StompHeaders implements MultiValueMap<String, String>, Serializable
 	 * Set the receipt header.
 	 * Applies to any client frame other than CONNECT.
 	 */
-	public void setReceipt(String receipt) {
+	public void setReceipt(@Nullable String receipt) {
 		set(RECEIPT, receipt);
 	}
 
@@ -177,7 +182,7 @@ public class StompHeaders implements MultiValueMap<String, String>, Serializable
 	 * Set the host header.
 	 * Applies to the CONNECT frame.
 	 */
-	public void setHost(String host) {
+	public void setHost(@Nullable String host) {
 		set(HOST, host);
 	}
 
@@ -193,7 +198,7 @@ public class StompHeaders implements MultiValueMap<String, String>, Serializable
 	 * Set the login header.
 	 * Applies to the CONNECT frame.
 	 */
-	public void setLogin(String login) {
+	public void setLogin(@Nullable String login) {
 		set(LOGIN, login);
 	}
 
@@ -209,7 +214,7 @@ public class StompHeaders implements MultiValueMap<String, String>, Serializable
 	 * Set the passcode header.
 	 * Applies to the CONNECT frame.
 	 */
-	public void setPasscode(String passcode) {
+	public void setPasscode(@Nullable String passcode) {
 		set(PASSCODE, passcode);
 	}
 
@@ -263,7 +268,7 @@ public class StompHeaders implements MultiValueMap<String, String>, Serializable
 	 * Set the session header.
 	 * Applies to the CONNECTED frame.
 	 */
-	public void setSession(String session) {
+	public void setSession(@Nullable String session) {
 		set(SESSION, session);
 	}
 
@@ -279,7 +284,7 @@ public class StompHeaders implements MultiValueMap<String, String>, Serializable
 	 * Set the server header.
 	 * Applies to the CONNECTED frame.
 	 */
-	public void setServer(String server) {
+	public void setServer(@Nullable String server) {
 		set(SERVER, server);
 	}
 
@@ -295,7 +300,7 @@ public class StompHeaders implements MultiValueMap<String, String>, Serializable
 	/**
 	 * Set the destination header.
 	 */
-	public void setDestination(String destination) {
+	public void setDestination(@Nullable String destination) {
 		set(DESTINATION, destination);
 	}
 
@@ -312,7 +317,7 @@ public class StompHeaders implements MultiValueMap<String, String>, Serializable
 	 * Set the id header.
 	 * Applies to the SUBSCR0BE, UNSUBSCRIBE, and ACK or NACK frames.
 	 */
-	public void setId(String id) {
+	public void setId(@Nullable String id) {
 		set(ID, id);
 	}
 
@@ -328,7 +333,7 @@ public class StompHeaders implements MultiValueMap<String, String>, Serializable
 	 * Set the ack header to one of "auto", "client", or "client-individual".
 	 * Applies to the SUBSCRIBE and MESSAGE frames.
 	 */
-	public void setAck(String ack) {
+	public void setAck(@Nullable String ack) {
 		set(ACK, ack);
 	}
 
@@ -344,7 +349,7 @@ public class StompHeaders implements MultiValueMap<String, String>, Serializable
 	 * Set the login header.
 	 * Applies to the MESSAGE frame.
 	 */
-	public void setSubscription(String subscription) {
+	public void setSubscription(@Nullable String subscription) {
 		set(SUBSCRIPTION, subscription);
 	}
 
@@ -360,7 +365,7 @@ public class StompHeaders implements MultiValueMap<String, String>, Serializable
 	 * Set the message-id header.
 	 * Applies to the MESSAGE frame.
 	 */
-	public void setMessageId(String messageId) {
+	public void setMessageId(@Nullable String messageId) {
 		set(MESSAGE_ID, messageId);
 	}
 
@@ -376,7 +381,7 @@ public class StompHeaders implements MultiValueMap<String, String>, Serializable
 	 * Set the receipt-id header.
 	 * Applies to the RECEIPT frame.
 	 */
-	public void setReceiptId(String receiptId) {
+	public void setReceiptId(@Nullable String receiptId) {
 		set(RECEIPT_ID, receiptId);
 	}
 
@@ -433,7 +438,7 @@ public class StompHeaders implements MultiValueMap<String, String>, Serializable
 	 * @see #add(String, String)
 	 */
 	@Override
-	public void set(String headerName, String headerValue) {
+	public void set(String headerName, @Nullable String headerValue) {
 		List<String> headerValues = new LinkedList<>();
 		headerValues.add(headerValue);
 		headers.put(headerName, headerValues);

spring-messaging/src/main/java/org/springframework/messaging/simp/user/UserDestinationMessageHandler.java

@@ -108,7 +108,7 @@ public class UserDestinationMessageHandler implements MessageHandler, SmartLifec
 	 * <p>By default this is not set.
 	 * @param destination the target destination.
 	 */
-	public void setBroadcastDestination(String destination) {
+	public void setBroadcastDestination(@Nullable String destination) {
 		this.broadcastHandler = (StringUtils.hasText(destination) ?
 				new BroadcastHandler(this.messagingTemplate, destination) : null);
 	}
@@ -134,7 +134,7 @@ public class UserDestinationMessageHandler implements MessageHandler, SmartLifec
 	 * headers of resolved target messages.
 	 * <p>By default this is not set.
 	 */
-	public void setHeaderInitializer(MessageHeaderInitializer headerInitializer) {
+	public void setHeaderInitializer(@Nullable MessageHeaderInitializer headerInitializer) {
 		this.headerInitializer = headerInitializer;
 	}
 

spring-messaging/src/main/java/org/springframework/messaging/support/IdTimestampMessageHeaderInitializer.java

@@ -43,7 +43,7 @@ public class IdTimestampMessageHeaderInitializer implements MessageHeaderInitial
 	 * IdGenerator of {@link org.springframework.messaging.MessageHeaders} is used.
 	 * <p>To have no id's generated at all, see {@link #setDisableIdGeneration()}.
 	 */
-	public void setIdGenerator(IdGenerator idGenerator) {
+	public void setIdGenerator(@Nullable IdGenerator idGenerator) {
 		this.idGenerator = idGenerator;
 	}