Apache Camel — Hazelcast Topic Publish/Subscribe — how to serialize String message in Subscriber

Question

I was trying to follow the sample code at http://camel.apache.org/hazelcast-component.html#HazelcastComponent-topic to test with publish/subscribe through Hazelcast.

Below listed the publisher and subscriber routes definitions

<route>
    <from uri="direct:inbound" />
    <setHeader headerName="CamelHazelcastOperationType">
        <simple>${type:org.apache.camel.component.hazelcast.HazelcastConstants.PUBLISH_OPERATION}</simple>
    </setHeader>
    <to uri="hazelcast:topic:foo" />
</route>    

<route>
    <from uri="hazelcast:topic:foo" />
    <log message="from hazelcast topic:= ${body}" />
    <bean ref="inboundProcessor" method="processHazelcastMsg" />
</route>

During my test, I sent a String like "{\\"result\\": \\"InboundProcessor.processRequest success\\"}" to publisher route through direct:inbound endpoint. The subscriber route was able to receive the message from topic and pass to processor bean. However, I was failed to get back the string properly...

Here is how I implement the bean method

public void processHazelcastMsg(Exchange inEx) throws Exception{

    Map<String, Object> headers = inEx.getIn().getHeaders();

    System.out.println("Exchange > In msg > Body = " + inEx.getIn().getBody());
    System.out.println("Exchange > In msg > Body class = " + ObjectHelper.className(inEx.getIn().getBody()));
    DataAwareMessage msg = inEx.getIn().getBody(DataAwareMessage.class);

    byte[] b = serializeObject(msg.getMessageObject());
    String msgStr = new String(b, Charset.forName("utf-8"));

    System.out.println("Received msg string = " + msgStr);
}

private static byte[] serializeObject(Object object) throws IOException
{
    try (ByteArrayOutputStream bos = new ByteArrayOutputStream();
             ObjectOutput out = new ObjectOutputStream(bos)) {
            out.writeObject(object);
            return bos.toByteArray();
        } 
}   

and here is the log output:

[  hz._hzInstance_1_dev.event-5] route4                         INFO  from hazelcast topic:= com.hazelcast.topic.impl.DataAwareMessage[source=foo]
Exchange > In msg > Body = com.hazelcast.topic.impl.DataAwareMessage[source=foo]
Exchange > In msg > Body class = com.hazelcast.topic.impl.DataAwareMessage
Received msg string = ��

I did try to covert string using different encoding (like UTF-8/UTF-16... etc) but still failed. Wondering if there should be another way to get back the correct String in subscriber

Answer 1

With the hazelcast topic producer, the message body is of type Message . You can get the original object by calling Message.getMessageObject() :

public void processHazelcastMsg(Exchange inEx) throws Exception {
  String msgStr = inEx.getIn().getBody(Message.class).getMessageObject().toString();
}