org.springframework.messaging.simp.annotation.support

Class SubscriptionMethodReturnValueHandler

java.lang.Object

org.springframework.messaging.simp.annotation.support.SubscriptionMethodReturnValueHandler

All Implemented Interfaces:

HandlerMethodReturnValueHandler

public class SubscriptionMethodReturnValueHandler
extends Object
implements HandlerMethodReturnValueHandler

HandlerMethodReturnValueHandler for replying directly to a subscription. It is supported on methods annotated with SubscribeMapping such that the return value is treated as a response to be sent directly back on the session. This allows a client to implement a request-response pattern and use it for example to obtain some data upon initialization.

The value returned from the method is converted and turned into a Message that is then enriched with the sessionId, subscriptionId, and destination of the input message.

Note: this default behavior for interpreting the return value from an @SubscribeMapping method can be overridden through use of the SendTo or SendToUser annotations in which case a message is prepared and sent to the broker instead.

Since:

4.0

Author:

Rossen Stoyanchev, Sebastien Deleuze

Constructor Summary

Constructors

Constructor and Description
SubscriptionMethodReturnValueHandler(MessageSendingOperations<String> template) Construct a new SubscriptionMethodReturnValueHandler.

Method Summary

Modifier and Type	Method and Description
MessageHeaderInitializer	getHeaderInitializer() Return the configured header initializer.
void	handleReturnValue(Object returnValue, MethodParameter returnType, Message<?> message) Handle the given return value.
void	setHeaderInitializer(MessageHeaderInitializer headerInitializer) Configure a MessageHeaderInitializer to apply to the headers of all messages sent to the client outbound channel.
boolean	supportsReturnType(MethodParameter returnType) Whether the given method return type is supported by this handler.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

SubscriptionMethodReturnValueHandler

public SubscriptionMethodReturnValueHandler(MessageSendingOperations<String> template)

Construct a new SubscriptionMethodReturnValueHandler.

Parameters:

template - a messaging template to send messages to, most likely the "clientOutboundChannel" (must not be null)

Method Detail

setHeaderInitializer

public void setHeaderInitializer(@Nullable
                                 MessageHeaderInitializer headerInitializer)

Configure a MessageHeaderInitializer to apply to the headers of all messages sent to the client outbound channel.

By default this property is not set.

getHeaderInitializer

@Nullable
public MessageHeaderInitializer getHeaderInitializer()

Return the configured header initializer.

supportsReturnType

public boolean supportsReturnType(MethodParameter returnType)

Description copied from interface: HandlerMethodReturnValueHandler

Whether the given method return type is supported by this handler.

Specified by:

supportsReturnType in interface HandlerMethodReturnValueHandler

Parameters:

returnType - the method return type to check

Returns:

true if this handler supports the supplied return type; false otherwise

handleReturnValue

public void handleReturnValue(@Nullable
                              Object returnValue,
                              MethodParameter returnType,
                              Message<?> message)
                       throws Exception

Description copied from interface: HandlerMethodReturnValueHandler

Handle the given return value.

Specified by:

handleReturnValue in interface HandlerMethodReturnValueHandler

Parameters:

returnValue - the value returned from the handler method

returnType - the type of the return value. This type must have previously been passed to HandlerMethodReturnValueHandler.supportsReturnType(org.springframework.core.MethodParameter) and it must have returned true.

message - the message that caused this method to be called

Throws:

Exception - if the return value handling results in an error