From 8c9de582541622d899682e395ec3ab2c48b36ea4 Mon Sep 17 00:00:00 2001 From: Mark Fisher Date: Tue, 19 Aug 2008 23:30:12 +0000 Subject: [PATCH] Updated MessageSource and MessageChannel sections. --- spring-integration-reference/src/core-api.xml | 73 +++++++++++++------ 1 file changed, 52 insertions(+), 21 deletions(-) diff --git a/spring-integration-reference/src/core-api.xml b/spring-integration-reference/src/core-api.xml index 6d795a8f38..1633b68a37 100644 --- a/spring-integration-reference/src/core-api.xml +++ b/spring-integration-reference/src/core-api.xml @@ -102,7 +102,7 @@ new GenericMessage<T>(T payload, Map<String, Object> headers)and payload of that Message will be copied to the new Message: - Message<String> message1 = MessageBuilder.fromPayload("test") + Message<String> message1 = MessageBuilder.fromPayload("test") .setHeader("foo", "bar") .build(); @@ -114,7 +114,7 @@ assertEquals("bar", message2.getHeaders().get("foo")); If you need to create a Message with a new payload but still want to copy the headers from an existing Message, you can use one of the 'copy' methods. - Message<String> message3 = MessageBuilder.fromPayload("test3") + Message<String> message3 = MessageBuilder.fromPayload("test3") .copyHeaders(message1.getHeaders()) .build(); @@ -129,7 +129,7 @@ assertEquals(123, message4.getHeaders().get("foo")); second example above, you can see how to set any user-defined header with setHeader. Finally, there are set methods available for the predefined headers as well as a non-destructive method for setting any header (MessageHeaders also defines constants for the pre-defined header names). - Message<Integer> importantMessage = MessageBuilder.fromPayload(99) + Message<Integer> importantMessage = MessageBuilder.fromPayload(99) .setPriority(MessagePriority.HIGHEST) .build(); @@ -166,11 +166,21 @@ assertEquals(MessagePriority.HIGHEST, anotherMessage.getHeaders().getPriority())
MessageSource - The MessageSource interface defines a single method for receiving - Message objects. - public interface MessageSource<T> { + As alluded to in the overview, the MessageSource interface is itself a marker + interface for any "source" of Messages. The two sub-interfaces - PollableSource + and SubscribableSource - accommodate two types of source: those that must be + polled and those that send Messages on their own. An example of the first type would be a source that represents + a directory in the File-system, and an example of the second type would be an inbound RMI invocation. + + + The PollableSource interface defines a single method for receiving Message objects. + public interface PollableSource<T> extends MessageSource<T> { Message<T> receive(); } + The BlockingSource interface extends PollableSource + and adds a single method with a timeout: Message<T> receive(long timeout); + + Spring Integration also provides a MethodInvokingSource implementation that serves as an adapter for invoking any arbitrary method on a plain Object (i.e. there is no need to implement an interface). To use the MethodInvokingSource, provide the Object reference and the method name. @@ -178,8 +188,8 @@ assertEquals(MessagePriority.HIGHEST, anotherMessage.getHeaders().getPriority()) source.setObject(new SourceObject()); source.setMethodName("sourceMethod"); Message<?> result = source.receive(); - It is generally more common to configure a MethodInvokingSource in XML by providing a - bean reference in the "source" attribute of a <channel-adapter> element. + It is also possible to configure a MethodInvokingSource in XML by providing a + bean reference in the "source" attribute of a <channel-adapter> element along with a "method" attribute. ]]>
@@ -210,24 +220,45 @@ target.send(new StringMessage("test")); While the Message plays the crucial role of encapsulating data, it is the MessageChannel that decouples message producers from message consumers. - Spring Integration's MessageChannel interface is defined as follows. - MessageChannel interface is defined as follows. + > clear(); - List> purge(MessageSelector selector); }]]> + Because it extends BlockingTarget, it inherits the following methods: + boolean send(Message message); + +boolean send(Message message, long timeout); When sending a message, the return value will be true if the message is sent successfully. - If the send call times out or is interrupted, then it will return false. Likewise when - receiving a message, the return value will be null in the case of a timeout or interrupt. + If the send call times out or is interrupted, then it will return false. - Spring Integration provides several different implementations of the - MessageChannel interface. Each is briefly described in the sections below. + Since Message Channels are also Message Sources, there are two sub-interfaces corresponding to the two source + types. Here is the definition of PollableChannel. + public interface PollableChannel extends MessageChannel, BlockingSource { + + List<Message<?>> clear(); + + List<Message<?>> purge(MessageSelector selector); + +} + Since the PollableChannel interface extends BlockingSource, it also inherits the following methods: + Message<T> receive(); + +Message<T> receive(long timeout); + Similar to the send methods, when receiving a message, the return value will be null in the + case of a timeout or interrupt. + + + The subscribable channels implement the SubscribableSource interface. Instead + of providing receive methods for polling, these channels will send messages directly to their subscribers. + The SubscribableSource interface defines the following two methods: + boolean subscribe(MessageTarget target); + +boolean unsubscribe(MessageTarget target); + + + Spring Integration provides several different Message Channel implementations. Each is briefly described in the + sections below.
PublishSubscribeChannel