ConsumerTemplate

The ConsumerTemplate interface allows you to receive message exchanges from endpoints in a variety of different ways to make it easy to work with Camel Endpoint instances from Java code.

It can be configured with a default endpoint if you just want to receive lots of messages to the same endpoint; or you can specify an Endpoint or uri as the first parameter.

The receiveBody() method allows you to receive any object to an endpoint easily as shown:

ConsumerTemplate template = exchange.getContext().createConsumerTemplate();

// recieve from default endpoint
Object body = template.receiveBody();

// receive from a specific queue
body = template.receiveBody("activemq:MyQueue");

Receive modes

The consumer template operates in three modes:

  • receive - Consumes from the endpoint, waiting until there is a message (can potentially wait for a long time!).

  • receiveNoWait - Consumes from endpoint, not waiting for a message if none exists.

  • receiveTimeout - Consumes from the endpoint, waiting until there is a response, or the timeout occurs.

In the previous examples then it was the first mode we used (receiveBody). For example if there are no messages on the activemq:MyQueue then Camel would wait until a message is sent to this queue.

Often you dont want to wait forever so its often a good idea to use a timeout value, such as 5 seconds:

ConsumerTemplate template = exchange.getContext().createConsumerTemplate();

// receive from a specific queue
body = template.receiveBody("activemq:MyQueue", 5000);

Here we wait at most 5 seconds for a message to be consumed, if there was no message, then null is returned as response.

Configuring default cache size

You can configure globally the default cache size for both ProducerTemplate and ConsumerTemplate which will be created or dependency inject by CamelContext.

This can be done on the CamelContext as a global option as shown in the following Java code:

getCamelContext().getGlobalOptions().put(Exchange.MAXIMUM_CACHE_POOL_SIZE, "50");

Or in application.properties:

camel.main.consumerTemplateCacheSize = 50

The default maximum cache size is 1000.

See Also

See ProducerTemplate

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