docs/user-manual/en/guice-jms-example.adoc

[[GuiceJMSExample-GuiceJMSExample]]
=== Guice JMS Example

*Available as of Camel 1.5 onwards*

The Guice JMS example is functionally similar to both the
link:walk-through-an-example.adoc[first example] and the
link:spring-example.adoc[Spring Example] but using
link:guice.adoc[Guice] as the Dependency Injection framework.

In this example we just write RouteBuilder implementations, then we
write a Guice module
https://github.com/apache/camel/blob/master/examples/camel-example-guice-jms/src/main/java/org/apache/camel/example/guice/jms/MyModule.java[MyModule]
to create the CamelContext, bind any RouteBuilder instances and
configure any components and endpoints, then we create a
https://github.com/apache/camel/blob/master/examples/camel-example-guice-jms/src/main/resources/guicejndi.properties[guicejndi.properties]
file to bootstrap Guice and Camel.

To run the example we currently use the maven exec plugin. For example
from the source or binary distribution the following should work

[source,java]
----
cd examples/camel-example-guice-jms
mvn compile exec:java
----

What this does is boot up the Guice based JNDI provider from
https://github.com/apache/camel/blob/master/examples/camel-example-guice-jms/src/main/resources/guicejndi.properties[guicejndi.properties]
file on the classpath. This then bootstraps the Guice injector and loads
whatever Guice modules are defined in the guicejndi.properties file --
then injects the remaining properties in the file.


[[GuiceJMSExample-ConfiguringComponents]]
==== Configuring Components

If you see the `jms()` method of the Guice
https://github.com/apache/camel/blob/master/examples/camel-example-guice-jms/src/main/java/org/apache/camel/example/guice/jms/MyModule.java[MyModule]
you will see it is annotated with `@Provides` to indicate to Guice that
it is a provider and it is annotated with `@JndiBind("jms")` to bind it
to the JNDI name `jms` when it is created.

This method then configures the component. The provider method is
parameterized by the `@Named("activemq.brokerURL")` property which is
injected from the
https://github.com/apache/camel/blob/master/examples/camel-example-guice-jms/src/main/resources/guicejndi.properties[guicejndi.properties]
file. This lets you define the properties which should be environment
specific (such as URLs, machine names, usernames/passwords and so forth)
while leaving all of the other configuration which does not change in
different environments in Java code.

So you can use link:guice.adoc[Guice] to dependency inject whatever
objects you need to create, be it an link:endpoint.adoc[Endpoint],
link:component.adoc[Component], link:route-builder.adoc[RouteBuilder] or
arbitrary link:bean-integration.adoc[bean used within a route]. Then you
can inject any properties from the jndi.properties file easily -- so that
most of your configuration is all in Java code which is typesafe and
easily refactorable - then leaving some properties to be environment
specific (the guicejndi.properties file) which you can then change based
on development, testing, production, etc.