[[Binding-Binding]]
=== Binding

In Camel terms a _binding_ is a way of wrapping an
link:endpoint.html[Endpoint] in a contract; such as a
link:data-format.html[Data Format], a link:content-enricher.html[Content
Enricher] or validation step. Bindings are completely optional and you
can choose to use them on any link:components.html[camel endpoint].

Bindings are inspired by the work of
http://www.jboss.org/switchyard[SwitchYard project] adding service
contracts to various technologies like Camel and many others. But rather
than the SwitchYard approach of wrapping Camel in SCA, _Camel Bindings_
provide a way of wrapping Camel endpoints with contracts inside the
Camel framework itself; so you can use them easily inside any Camel
route.

[[Binding-UsingBindings]]
==== Using Bindings

A Binding is currently a bean which defines the contract (though we'll
hopefully add bindings to the Camel DSL).

There are a few approaches to defining a bound endpoint (i.e. an
endpoint bound with a Binding).

[[Binding-UsingthebindingURI]]
==== Using the binding URI

You can prefix any endpoint URI with *binding:nameOfBinding:* where
_nameOfBinding_ is the name of the Binding bean in your registry.

[source,java]
------------------------------------------------------------------------------
from("binding:jaxb:activemq:myQueue").to("binding:jaxb:activemq:anotherQueue")
------------------------------------------------------------------------------

Here we are using the "jaxb" binding which may, for example, use the
JAXB link:data-format.html[Data Format] to marshal and unmarshal
messages.

[[Binding-UsingaBindingComponent]]
==== Using a BindingComponent

There is a link:component.html[Component] called BindingComponent which
can be configured in your link:registry.html[Registry] by dependency
injection which allows the creation of endpoints which are already bound
to some binding.

For example if you registered a new component called "jsonmq" in your
registry using code like this

[source,java]
-----------------------------------------------------------------------------------------------------
        JacksonDataFormat format = new JacksonDataFormat(MyBean.class);
        context.bind("jsonmq", new BindingComponent(new DataFormatBinding(format), "activemq:foo."));
-----------------------------------------------------------------------------------------------------

Then you could use the endpoint as if it were any other endpoint.

[source,java]
------------------------------------------------
from("jsonmq:myQueue").to("jsonmq:anotherQueue")
------------------------------------------------

This would use the queues "foo.myQueue" and "foo.anotherQueue" and would
use the given Jackson link:data-format.html[Data Format] to marshal on
and off the queue.

[[Binding-WhentouseBindings]]
==== When to use Bindings

If you only use an endpoint once in a single route; a binding may
actually be more complex and more work than just using the 'raw'
endpoint directly and using explicit marshalling and validation in the
camel route as normal.

However bindings can help when you are composing many routes together;
or using a single route as a 'template' that is configured input and
output endpoints; bindings then provide a nice way to wrap up a contract
and endpoint together.

Another good use case for bindings is when you are using many endpoints
which use the same binding; rather than always having to mention a
specific data format or validation rule, you can just use the
BindingComponent to wrap the endpoints in the binding of your choice.

So bindings are a composition tool really; only use them when they make
sense - the extra complexity may not be worth it unless you have lots of
routes or endpoints.
