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Chapter 54. JavaSpace

JavaSpace Component

The javaspace component is a transport for working with any JavaSpace compliant implementation and this component has been tested with both the Blitz implementation and the GigaSpace implementation. This component can be used for sending and receiving any object inheriting from the Jini net.jini.core.entry.Entry class. It is also possible to pass the bean ID of a template that can be used for reading/taking the entries from the space. This component can be used for sending/receiving any serializable object acting as a sort of generic transport. The JavaSpace component contains a special optimization for dealing with the BeanExchange. It can be used to invoke a POJO remotely, using a JavaSpace as a transport. This latter feature can provide a simple implementation of the master/worker pattern, where a POJO provides the business logic for the worker. Look at the test cases for examples of various use cases for this component.

URI format

javaspace:jini://host[?options]
You can append query options to the URI in the following format, ?option=value&option=value&...

Options

Name Default Value Description
spaceName null Specifies the JavaSpace name.
verb take Specifies the verb for getting JavaSpace entries. The values can be: take or read.
transactional false If true, sending and receiving entries is performed within a transaction.
transactionalTimeout Long.MAX_VALUE Specifies the transaction timeout.
concurrentConsumers 1 Specifies the number of concurrent consumers getting entries from the JavaSpace.
templateId null If present, this option specifies the Spring bean ID of the template to use for reading/taking entries.

Sending and Receiving Entries

//Sending route
from("direct:input").to("javaspace:jini://localhost?spaceName=mySpace");

//Receiving Route
from("javaspace:jini://localhost?spaceName=mySpace&templateId=template&verb=take&concurrentConsumers=1")
In this case the payload can be any object that inherits from the Jini Entry type.

Sending and receiving serializable objects

Using the preceding routes, it is also possible to send and receive any serializable object. The JavaSpace component detects that the payload is not a Jini Entry and then it automatically wraps the payload with a Camel Jini Entry. In this way, a JavaSpace can be used as a generic transport mechanism.

Using JavaSpace as a remote invocation transport

The JavaSpace component has been tailored to work in combination with the Camel bean component. It is therefore possible to call a remote POJO using JavaSpace as the transport: 
from("direct:input").to("javaspace:jini://localhost?spaceName=mySpace"); //Client side

from("javaspace:jini://localhost?concurrentConsumers=10&spaceName=mySpace").to("pojo:pojo"); //Server side
In the code there are two test cases showing how to use a POJO to realize the master/worker pattern. The idea is to use the POJO to provide the business logic and rely on Apache Camel for sending/receiving requests/replies with the proper correlation.