Nullpointer in AggregatingMessageHandler

[ttruong]

I have the following use case:

1. Splitter bean: incoming String is splitted and returned
2. Pass bean: that just returns the incoming payload
3. Aggregator bean: a logger that expects to get ALL strings to log them

The SplitAggregate.xml looks like this:

	<message-bus />

	<channel id="inputChannel"/>
	<channel id="passChannel"/>
	<channel id="logChannel"/>

	<splitter id="splitterEndpoint" input-channel="inputChannel" output-channel="passChannel"
		ref="splitter" method="split" />
	<beans:bean id="splitter"
		class="test.Split">
	</beans:bean>
	
	<service-activator id="passEndpoint" input-channel="passChannel" output-channel="logChannel"
		ref="pass" method="pass"/>
	<beans:bean id="pass"
		class="test.Pass">
	</beans:bean>

	<aggregator id="aggregator" input-channel="logChannel"
		ref="logAll" method="log" />
	<beans:bean id="logAll"
		class="test.LogAll">
	</beans:bean>

The Split class:

package test;

public class Split {

    public String[] split(String payload) {
        return payload.split(",");
    }
}

The Pass class:

package test;

public class Pass {

    public String pass(String payload) {
        return payload;
    }
}

The LogAll class:

package test;

import java.util.List;

public class LogAll {

    public void log(List<String> payloads) {
        System.out.println(">>>" + payloads);
    }
}

To start the Demo:

package test;

import org.springframework.context.support.ClassPathXmlApplicationContext;
import org.springframework.integration.channel.ChannelRegistry;
import org.springframework.integration.channel.MessageChannel;
import org.springframework.integration.config.MessageBusParser;
import org.springframework.integration.message.GenericMessage;

public class Demo {

    /**
     * @param args
     */
    public static void main(String[] args) {
        ClassPathXmlApplicationContext context = new ClassPathXmlApplicationContext("SplitAggregate.xml", Pass.class);
        context.start();
        ChannelRegistry channelRegistry = (ChannelRegistry) context.getBean(MessageBusParser.MESSAGE_BUS_BEAN_NAME);
        MessageChannel channel = channelRegistry.lookupChannel("inputChannel");
        channel.send(new GenericMessage<String>("1,2,3,4"));
    }

}

The error message I get is:

Caused by: java.lang.NullPointerException
at org.springframework.integration.aggregator.Aggrega tingMessageHandler.processReleasedMessages(Aggrega tingMessageHandler.java:91)

Here the return message is null that causes this exception.

I have attached also the source code in a zip file. Should I create a Jira entry for this?

[Mark Fisher]

Please do report a JIRA issue for this.

[ttruong]

I have created an issue under INT-369. There I have also put a comment about the problem and solution I found.

There is something confusing when reading the Reference Manual for the Splitter and Aggregator in:
http://static.springframework.org/sp...onent-splitter

To be more precise:

1. Splitter
A component acting as a Splitter returns a List of output messages (as a return value of the method). In this case each output message is send one by one (instead of the whole list) to the output channel.
=> Ergo: a Splitter requires only an output channel. The component's method can be called directly or by an optional input-channel.

2. Aggregator
A component acting as an Aggregator expects a List of input messages (as an input argument of the method). The messages send to the input channel one-by-one are totally collected in a List before passing it to the Aggregator.
=>Ergo: an Aggregator requires only an input channel.

[ttruong]

In case somebody can't wait. Attached you'll find a patch for workaround