Spring Integration 系统集成

Spring Integration 系统集成Spring Ingegration 提供了基于Spring的EIP(Enterprise Integration Patterns,企业集成模式)的实现。

Spring Integration 主要解决的问题是不同系统之间交互的问题，通过异步消息驱动来达到系统交互时系统之间的松耦合。

Spring Integration 主要有Message、Channel、Message EndPoint组成。

MessageMessage是用来在不同部分之间传递的数据。

Message有两部分组成:消息体(payload)与消息头(header)。

消息体可以是任何数据类型；消息头表示的元数据就是解释消息体的内容。

/*** A generic message representation with headers and body.** @author Mark Fisher* @author Arjen Poutsma* @since 4.0* @seeorg.springframework.messaging.support.MessageBuilder */public interface Message {/*** Return the message payload.*/T getPayload();/*** Return message headers for the message (never {@code null} but may be empty).*/MessageHeaders getHeaders();}123456789101112131415161718192021Channel在消息系统中，消息发送者发送消息到通道(Channel)，消息接受者从通道(Channel)接收消息。

1、顶级接口(1) MessageChannelMessageChannel 是Spring Integration消息通道的顶级接口：public interface MessageChannel {/*** Constant for sending a message without a prescribed timeout.*/long INDEFINITE_TIMEOUT = -1;/*** Send a {@link Message} to this channel. If the message is sent successfully,* the method returns {@code true}. If the message cannot be sent due to a* non-fatal reason, the method returns {@code false}. The method may also* throw a RuntimeException in case ofnon-recoverable errors.* This method may block indefinitely, depending on the implementation.* To provide a maximum wait time, use {@link#send(Message, long)}.* @param message the message to send* @return whether or not the message was sent*/boolean send(Message message);/*** Send a message, blocking until either the message is accepted or the* specified timeout period elapses.* @param message the message to send* @param timeout the timeout in milliseconds or {@link #INDEFINITE_TIMEOUT}* @return {@code true} if the message is sent,{@code false} if not* including a timeout of an interrupt of the send*/boolean send(Message message, long timeout);}1234567891011121314151617181920212223242526272 8293031MessageChannel 有两大子接口，分别是PollableChannel(可轮询)和SubscribableChannel(可订阅)。

我们所有的消息通道类都是现实这两个接口。

(2) PollableChannelPollableChannel 具备轮询获得消息的能力。

public interface PollableChannel extends MessageChannel {/*** Receive a message from this channel, blocking indefinitely if necessary.* @return the next available {@link Message} or {@code null} if interrupted*/Message receive();/*** Receive a message from this channel, blocking until either a message is available* or the specified timeout period elapses.* @param timeout the timeout in milliseconds or {@link MessageChannel#INDEFINITE_TIMEOUT}.* @return the next available {@link Message} or{@code null} if the specified timeout* period elapses or the message reception is interrupted*/Message receive(long timeout);}123456789101112131415161718(3) SubscribableChannelSubscribableChannel 发送消息给订阅了MessageHanlder 的订阅者public interface SubscribableChannel extends MessageChannel {/*** Register a message handler.* @return {@code true} if the handler was subscribed or {@code false} if it* was already subscribed.*/boolean subscribe(MessageHandler handler);/*** Un-register a message handler.* @return {@code true} if the handler wasun-registered, or {@code false}* if was not registered.*/boolean unsubscribe(MessageHandler handler);}12345678910111213141516172、常用消息通道(1)、PublishSubscribeChannel PublishSubscribeChannel允许广播消息给所有订阅者，配置方式如下：/*** 允许广播消息给所有订阅者，当前消息通道的id为publishSubscribeChannel* @return*/@Beanpublic PublishSubscribeChannel publishSubscribeChannel(){PublishSubscribeChannel channel = new PublishSubscribeChannel();return channel;}123456789其中，当前消息通道的id为publishSubscribeChannel。

(2)、QueueChannelQueueChannel允许消息接收者轮询获得消息，用一个队列(queue)接收消息，队列的容量大小可配置，配置方式如下：@Beanpublic QueueChannel queueChannel(){QueueChannel channel = newQueueChannel(10);return channel;}12345其中，QueueChannel构造参数10即为队列的容量。

(3)、PriorityChannelPriorityChannel可按照优先级将数据存储到队列，它依据于消息的消息头priority属性，配置方式如下：@Beanpublic PriorityChannel priorityChannel(){PriorityChannel channel = newPriorityChannel(10);return channel;}12345(4)、RendezvousChannelRendezvousChannel确保每一个接收者都接收到消息后再发送消息，配置方式如下：@Beanpublic RendezvousChannel rendezvousChannel(){ RendezvousChannel channel = new RendezvousChannel();return channel;}12345(5) DirectChannelDirectChannel是Spring Integration默认的消息通道，它允许将消息发送给为一个订阅者，然后阻碍发送直到消息被接收，配置方式如下：@Beanpublic DirectChannel directChannel(){DirectChannel channel = new DirectChannel();return channel;}12345(6)、ExecutorChannelExecutorChannel可绑定一个多线程的task executor，配置方式如下：@Beanpublic ExecutorChannel executorChannel(){ExecutorChannel channel = new ExecutorChannel(executor());return channel;}@Beanpublic Executor executor(){ThreadPoolTaskExecutor taskExecutor = new ThreadPoolTaskExecutor();taskExecutor.setCorePoolSize(5);taskExecutor.setMaxPoolSize(10);taskExecutor.setQueueCapacity(25);taskExecutor.initialize();return taskExecutor;}1234567891011121314153、通道拦截器Spring Integration给消息通道提供了通道拦截器(ChannelInterceptor)，用来拦截发送和接收消息的操作. ChannelInterceptor接口定义如下，我们只需要实现这个接口即可：public interface ChannelInterceptor {Message preSend(Message message, MessageChannel channel);void postSend(Message message, MessageChannel channel, boolean sent);void afterSendCompletion(Message message, MessageChannel channel, boolean sent, Exception ex);boolean preReceive(MessageChannel channel);Message postReceive(Message message, MessageChannel channel);void afterReceiveCompletion(Message message, MessageChannel channel, Exception ex);}123456789101112131415通过如下代码给所有的channel增加拦截器channel.addInterceptor(someInterceptor);Message EndPoint消息端点(Message EndPoint)是真正处理消息的(Message)组件，它还可以控制通道的路由。