Spring HTTP出站网关希望使用PollableChannel而不是DirectChannel

Question

I identified a configuration issue in my application which should try to send a request to a thirdparty service and should wait for the response. The content type of the request and response is json.

The problem what I found is within the MessagingGatewaySupport class where I found an expectation for the reply channel which should be PollableChannel, but I need to use DirectChannel instead of Pollable:

protected Object receive() {
this.initializeIfNecessary();
MessageChannel replyChannel = getReplyChannel();
Assert.state(replyChannel != null && (replyChannel instanceof PollableChannel),
        "receive is not supported, because no pollable reply channel has been configured");
return this.messagingTemplate.receiveAndConvert(replyChannel, null);
}

I really think that I have a mistake in my configuration which is the following:

<beans xmlns="http://www.springframework.org/schema/beans" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:jee="http://www.springframework.org/schema/jee" xmlns:int="http://www.springframework.org/schema/integration" xmlns:int-http="http://www.springframework.org/schema/integration/http" xsi:schemaLocation="http://www.springframework.org/schema/jee http://www.springframework.org/schema/jee/spring-jee-4.3.xsd http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-4.3.xsd http://www.springframework.org/schema/integration/http http://www.springframework.org/schema/integration/http/spring-integration-http-4.3.xsd http://www.springframework.org/schema/integration http://www.springframework.org/schema/integration/spring-integration-4.3.xsd">

<jee:jndi-lookup id="repositoryUrl" jndi-name="repositoryUrl"/>
<jee:jndi-lookup id="wsMaxTotalConnections" jndi-name="wsMaxTotalConnections" default-value="50"/>
<jee:jndi-lookup id="wsMaxPerRoute" jndi-name="wsDefaultMaxPerRoute" default-value="50"/>
<jee:jndi-lookup id="wsConnectionTimeout" jndi-name="wsDefaultConnectionTimeout" default-value="10000"/>
<jee:jndi-lookup id="wsReadTimeout" jndi-name="wsDefaultReadTimeout" default-value="5000"/>

<int:gateway id="requestGateway" service-interface="com.example.Repository" default-request-channel="requestChannel" 
    default-reply-channel="responseChannel"/>

<int:channel id="requestChannel"/>
<int:channel id="responseChannel"/>

<int-http:outbound-gateway request-channel="requestChannel" url="#{repositoryUrl}" http-method="POST" expected-response-type="java.lang.String"
    request-factory="httpComponentsClientHttpRequestFactory" message-converters="jsonMessageConverter"/>

<bean id="jsonMessageConverter" class="com.example.JsonMessageConverter">
    <constructor-arg>
        <bean class="com.example.DataType"/>
    </constructor-arg>
</bean>

<bean id="httpComponentsClientHttpRequestFactory" class="com.example.ApplicationHttpComponentsClientHttpRequestFactory">
    <property name="maxTotalConnections" ref="wsMaxTotalConnections"/>
    <property name="defaultMaxPerRoute" ref="wsMaxPerRoute"/>
    <property name="connectionTimeout" ref="wsConnectionTimeout"/>
    <property name="readTimeout" ref="wsReadTimeout"/>
</bean>

JsonMessageConverter class:

public class JsonMessageConverter implements HttpMessageConverter<Object> {
private static final Logger logger = LoggerFactory.getLogger(JsonMessageConverter.class);

private Object clazz;

private List<MediaType> supportedMediaTypes = Collections.emptyList();

public Object getClazz()
{
    return clazz;
}

public void setClazz(Object clazz)
{
    this.clazz = clazz;
}

public JsonMessageConverter(Object clazz)
{
    this.clazz = clazz;
}

@Override
public boolean canRead(Class<?> clazz, MediaType mediaType)
{
    return this.clazz.getClass().equals(clazz);
}

@Override
public boolean canWrite(Class<?> clazz, MediaType mediaType)
{
    return false;
}

@Override
public List<MediaType> getSupportedMediaTypes()
{
    return supportedMediaTypes;
}

@Override
public Object read(Class<? extends Object> clazz, HttpInputMessage inputMessage) throws IOException, HttpMessageNotReadableException
{
    Object response = new Object();

    logger.trace("Received message in :{} ", inputMessage.getBody().toString());

    try
    {
        Gson gson = new Gson();
        String inputStreamString = inputMessage.getBody().toString();

        response = gson.fromJson(inputStreamString, this.clazz.getClass());
    }
    catch (Exception e)
    {
        throw new HttpMessageConversionException("Failed to convert response to: " + clazz, e);
    }

    logger.trace("Received message out :{} ", response);

    return response;

}

@Override
public void write(Object t, MediaType contentType, HttpOutputMessage outputMessage) throws IOException, HttpMessageNotWritableException
{
    Gson gson = new Gson();

    logger.trace("Sent message in :{} ", t);

    String json = gson.toJson(t);

    outputMessage.getBody().write(json.getBytes());

    logger.trace("Sent message out :{} ", json);
}

}

The related part of the exception:

java.lang.IllegalStateException: receive is not supported, because no pollable reply channel has been configured
at org.springframework.util.Assert.state(Assert.java:392)
at org.springframework.integration.gateway.MessagingGatewaySupport.receive(MessagingGatewaySupport.java:391)
at org.springframework.integration.gateway.GatewayProxyFactoryBean.invokeGatewayMethod(GatewayProxyFactoryBean.java:468)
at org.springframework.integration.gateway.GatewayProxyFactoryBean.doInvoke(GatewayProxyFactoryBean.java:429)
at org.springframework.integration.gateway.GatewayProxyFactoryBean.invoke(GatewayProxyFactoryBean.java:420)
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:179)
at org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:213)
at com.sun.proxy.$Proxy28.getSoccerSeasons(Unknown Source)
at com.example.ServiceImpl.getData(ServiceImpl.java:26)

The version of Spring Integration is 4.3.6. Can somebody help me? I tried many example, but I have not find any which has worked fine.

Thanks in advance for your help.

Answer 1

You need to show your com.example.Repository interface.

It looks like the method you are calling has no parameters. You need to send something in order to receive a reply.

See the documentation about gateway methods with no parameters .

When invoking methods on a Gateway interface that do not have any arguments, the default behavior is to receive a Message from a PollableChannel.

At times however, you may want to trigger no-argument methods so that you can in fact interact with other components downstream that do not require user-provided parameters, eg triggering no-argument SQL calls or Stored Procedures.

In order to achieve send-and-receive semantics, you must provide a payload. In order to generate a payload, ...