[JAVA] How to check before sending a message to the server with Spring Integration

Introduction

I see quite a few articles about Spring Framework, but I can't find any articles about Spring Integration, probably because they are not major in Japan, so I would like to post them irregularly. (I'm not saying I'll post: sunglasses :)

Development environment

Where is the process of sending a message via TCP communication in the first place?

The handleRequestMessage of the TcpOutboundGateway. In this method, we are sending a message to the server using TcpConnection obtained from ClientConnectionFactory.

TcpOutboundGateway message transmitter (partially omitted)

TcpOutboundGateway.java


protected Object handleRequestMessage(Message<?> requestMessage) {
	TcpConnection connection = null;
	String connectionId = null;
	try {
			connection = this.connectionFactory.getConnection();
			AsyncReply reply = new AsyncReply(this.remoteTimeoutExpression.getValue(this.evaluationContext,
					requestMessage, Long.class));
			connectionId = connection.getConnectionId();
			this.pendingReplies.put(connectionId, reply);
			if (logger.isDebugEnabled()) {
				logger.debug("Added pending reply " + connectionId);
			}
			connection.send(requestMessage);

Reason for sending check

Normally, it is not necessary to check when sending, but depending on the case, there may be a requirement such as "monitor the status of a component and do not send a message depending on that status." That's the deal I'm working on right now: v:

How to check transmission

For the time being, there are two methods I have come up with.

Extend TcpOutbound Gateway

Well, it's a straightforward idea ... Extend TcpOutboundGateway to override handleRequestMessage. Send processing is performed only when the return value of getStatus is true.

CustomizedTcpOutboundGateway.java


public class CustomizedTcpOutboundGateway extends TcpOutboundGateway {

  @Override
  public Object handleRequestMessage(Message<?> message) {
    if (getStatus()) {
      return super.handleRequestMessage(message);
    } else {
      return new GenericMessage<String>("can not send");
    }
  }

The return value of the original handleRequestMessage is of type ʻObject, but in the case of a normal system, the received message is returned, so an appropriate Message` object is returned. This depends on your requirements.

Take advantage of Interceptor

The method of ↑ is fine, but if you don't want to extend the framework class too much, there is a way to utilize ʻInterceptor`. The procedure is as follows.

First, extend TcpConnectionInterceptor and insert a check process when sending a message.

TcpConnectionInterceptor.java


public class TcpConnectionInterceptor extends TcpConnectionInterceptorSupport {

  @Override
  public void send(Message<?> message) throws Exception {
    if (getStatus()) {
      super.send(message);
    }
  }
 //Abbreviation

Send a message with the value of getStatus (). Since TcpConnectionInterceptorSupport has multiple methods around the connection, it is possible to insert processing at timings other than before sending like this time: hugging :.

Next, create a class that implements the TcpConnectionInterceptorFactory that returns the TcpConnectionInterceptor that you just created. The implementation is appropriate.

CustomizedTcpConnectionInterceptorFactory.java


public class CustomizedTcpConnectionInterceptorFactory implements TcpConnectionInterceptorFactory {

  private final TcpConnectionInterceptorSupport interceptor;

  public CustomizedTcpConnectionInterceptorFactory(TcpConnectionInterceptorSupport interceptor) {
    this.interceptor = interceptor;
  }

  @Override
  public TcpConnectionInterceptorSupport getInterceptor() {
    return interceptor;
  }
}

After that, pass this to TcpConnectionInterceptorFactoryChain and set it to ClientConnectionFactory.

  <int-ip:tcp-connection-factory type="client" host="localhost" port="56789"
    deserializer="deserializer" serializer="serializer" interceptor-factory-chain="interceptorFactoryChain" />

  <bean id="interceptorFactoryChain"
    class="org.springframework.integration.ip.tcp.connection.TcpConnectionInterceptorFactoryChain">
    <property name="interceptors">
      <array>
        <bean
          class="com.neriudon.sample.interceptor.CustomizedTcpConnectionInterceptorFactory"
          c:interceptor-ref="tcpConnectionInterceptor" />
      </array>
    </property>
  </bean>

  <bean id="tcpConnectionInterceptor"
    class="com.neriudon.sample.interceptor.TcpConnectionInterceptor" />

The ClientConnectionFactory settings are appropriate. : frowning2:

This method is a little complicated, but is it an advantage that you don't mess with the original Gateway?

How did you come to post this article?

As a memo because this function was needed for the project I am currently involved in.

at the end

Even if you google with the class name of Spring Integration, there are many cases where Japanese sites do not hit, so please try Spring Integration as well. : kissing_heart:

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