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h2. ServletListener Component
*Available as of Camel 2.11*

This component is used for bootstrapping Camel applications in web applications. For example beforehand people would have to find their own way of bootstrapping Camel, or rely on 3rd party frameworks such as Spring to do it.

{note:title=Sidebar}
This component supports Servlet 2.x onwards, which mean it works also in older web containers; which is the goal of this component.
Though Servlet 2.x requires to use a web.xml file as configuration.

For Servlet 3.x containers you can use annotation driven configuration to boostrap Camel using the @WebListener, and implement your own class, where you boostrap Camel. Doing this still puts the challenge how to let end users easily configure Camel, which you get for free with the old school web.xml file.
{note}

Maven users will need to add the following dependency to their {{pom.xml}} for this component:
{code:xml}
<dependency>
    <groupId>org.apache.camel</groupId>
    <artifactId>camel-servletlistener</artifactId>
    <version>x.x.x</version>
    <!-- use the same version as your Camel core version -->
</dependency>
{code}

h3. Using

You would need to chose one of the following implementations of the abstract class {{org.apache.camel.component.servletlistener.CamelServletContextListener}}.
- {{JndiCamelServletContextListener}} which uses the {{JndiRegistry}} to leverage JNDI for its registry.
- {{SimpleCamelServletContextListener}} which uses the {{SimpleRegistry}} to leverage a {{java.util.Map}} as its registry.

To use this you need to configure the {{org.apache.camel.component.servletlistener.CamelServletContextListener}} in the {{WEB-INF/web.xml}} file as shown below:
{snippet:id=web|lang=xml|url=camel/trunk/components/camel-servletlistener/src/test/resources/myweb.xml}

h3. Options

The {{org.apache.camel.component.servletlistener.CamelServletContextListener}} supports the following options which can be configured as context-param in the web.xml file.

{div:class=confluenceTableSmall}
|| Option || Type || Description ||
| propertyPlaceholder.XXX | | To configure [property placeholders|Using PropertyPlaceholder] in Camel. You should prefix the option with "propertyPlaceholder.", for example to configure the location, use propertyPlaceholder.location as name. You can configure all the options from the [Properties] component. |
| jmx.XXX | | To configure [JMX|Camel JMX]. You should prefix the option with "jmx.", for example to disable JMX, use jmx.disabled as name. You can configure all the options from {{org.apache.camel.spi.ManagementAgent}}. As well the options mentioned on the [JMX|Camel JMX] page. |
| name | {{String}} | To configure the name of the [CamelContext]. |
| streamCache | {{Boolean}} | Whether to enable [Stream Caching]. |
| trace | {{Boolean}} | Whether to enable [Tracer]. |
| delayer | {{Long}} | To set a delay value for [Delay Interceptor]. |
| handleFault | {{Boolean}} | Whether to enable handle fault. |
| errorHandlerRef | {{String}} | Refers to a context scoped [Error Handler] to be used. |
| autoStartup | {{Boolean}} | Whether to start all routes when starting Camel. |
| useMDCLogging | {{Boolean}} | Whether to use [MDC Logging]. |
| useBreadcrumb | {{Boolean}} | Whether to use [breadcrumb|MDC Logging]. |
| managementNamePattern | {{String}} | To set a custom naming pattern for JMX MBeans. |
| threadNamePattern | {{String}} | To set a custom naming pattern for threads. |
| properties.XXX | | To set custom properties on {{CamelContext.getProperties}}. This is seldom in use. |
| routebuilder.XXX | | To configure routes to be used. See below for more details. |
| CamelContextLifecycle | | Refers to a FQN classname of an implementation of {{org.apache.camel.component.servletlistener.CamelContextLifecycle}}. Which allows to execute custom code before and after [CamelContext] has been started or stopped. See below for further details. |
| XXX | | To set any option on [CamelContext]. |
{div}

h3. Examples

See [Servlet Tomcat No Spring Example]. 

h3. Configuring routes

You need to configure which routes to use in the web.xml file. You can do this in a number of ways, though all the parameters must be prefixed with "routeBuilder".

h4. Using a RouteBuilder class

By default Camel will assume the param-value is a FQN classname for a Camel [RouteBuilder] class, as shown below:

{code:xml}
  <context-param>
    <param-name>routeBuilder-MyRoute</param-name>
    <param-value>org.apache.camel.component.servletlistener.MyRoute</param-value>
  </context-param>
{code}

You can specify multiple classes in the same param-value as shown below:
{code:xml}
  <context-param>
    <param-name>routeBuilder-routes</param-name>
    <!-- we can define multiple values separated by comma -->
    <param-value>
      org.apache.camel.component.servletlistener.MyRoute,
      org.apache.camel.component.servletlistener.routes.BarRouteBuilder
    </param-value>
  </context-param>
{code}

The name of the parameter does not have a meaning at runtime. It just need to be unique and start with "routeBuilder". In the example above we have "routeBuilder-routes". But you could just as well have named it "routeBuilder.foo".

h4. Using package scanning

You can also tell Camel to use package scanning, which mean it will look in the given package for all classes of [RouteBuilder] types and automatic adding them as Camel routes. To do that you need to prefix the value with "packagescan:" as shown below:
{code:xml}
  <context-param>
    <param-name>routeBuilder-MyRoute</param-name>
    <!-- define the routes using package scanning by prefixing with packagescan: -->
    <param-value>packagescan:org.apache.camel.component.servletlistener.routes</param-value>
  </context-param>
{code}

h4. Using a XML file

You can also define Camel routes using XML DSL, though as we are not using Spring or Blueprint the XML file can only contain Camel route(s). 
In the web.xml you refer to the XML file which can be from "classpath", "file" or a "http" url, as shown below:
{code:xml}
  <context-param>
    <param-name>routeBuilder-MyRoute</param-name>
    <param-value>classpath:routes/myRoutes.xml</param-value>
  </context-param>
{code}

And the XML file is:
{code:xml:title=routes/myRoutes.xml}
<?xml version="1.0" encoding="UTF-8"?>
<!-- the xmlns="http://camel.apache.org/schema/spring" is needed -->
<routes xmlns="http://camel.apache.org/schema/spring">

  <route id="foo">
    <from uri="direct:foo"/>
    <to uri="mock:foo"/>
  </route>

  <route id="bar">
    <from uri="direct:bar"/>
    <to uri="mock:bar"/>
  </route>

</routes>
{code}

Notice that in the XML file the root tag is <routes> which must use the namespace "http://camel.apache.org/schema/spring". This namespace is having the spring in the name, but that is because of historical reasons, as Spring was the first and only XML DSL back in the time. At runtime no Spring JARs is needed. Maybe in Camel 3.0 the namespace can be renamed to a generic name.


h4. Configuring propert placeholders

Here is a snippet of a web.xml configuration for setting up property placeholders to load {{myproperties.properties}} from the classpath
{code:xml}
  <!-- setup property placeholder to load properties from classpath -->
  <!-- we do this by setting the param-name with propertyPlaceholder. as prefix and then any options such as location, cache etc -->
  <context-param>
    <param-name>propertyPlaceholder.location</param-name>
    <param-value>classpath:myproperties.properties</param-value>
  </context-param>
  <!-- for example to disable cache on properties component, you do -->
  <context-param>
    <param-name>propertyPlaceholder.cache</param-name>
    <param-value>false</param-value>
  </context-param>
{code}

h4. Configuring JMX

Here is a snippet of a web.xml configuration for configuring JMX, such as disabling JMX.

{code:xml}
  <!-- configure JMX by using names that is prefixed with jmx. -->
  <!-- in this example we disable JMX -->
  <context-param>
    <param-name>jmx.disabled</param-name>
    <param-value>true</param-value>
  </context-param>
{code}


h3. JNDI or Simple as Camel [Registry]

This component uses either JNDI or Simple as the [Registry].
This allows you to lookup [Bean]s and other services in JNDI, and as well to bind and unbind your own [Bean]s.

This is done from Java code by implementing the {{org.apache.camel.component.servletlistener.CamelContextLifecycle}}.

h4. Using custom CamelContextLifecycle

In the code below we use the callbacks {{beforeStart}} and {{afterStop}} to enlist our custom bean in the Simple [Registry], and as well to cleanup when we stop.
{snippet:id=e1|lang=java|url=camel/trunk/components/camel-servletlistener/src/test/java/org/apache/camel/component/servletlistener/MyLifecycle.java}

Then we need to register this class in the web.xml file as shown below, using the parameter name "CamelContextLifecycle". The value must be a FQN which refers to the class implementing the {{org.apache.camel.component.servletlistener.CamelContextLifecycle}} interface.
{code:xml}
  <context-param>
    <param-name>CamelContextLifecycle</param-name>
    <param-value>org.apache.camel.component.servletlistener.MyLifecycle</param-value>
  </context-param>
{code}

As we enlisted our HelloBean [Bean] using the name "myBean" we can refer to this [Bean] in the Camel routes as shown below:
{code}
public class MyBeanRoute extends RouteBuilder {
    @Override
    public void configure() throws Exception {
        from("seda:foo").routeId("foo")
            .to("bean:myBean")
            .to("mock:foo");
    }
}
{code}

*Important:* If you use {{org.apache.camel.component.servletlistener.JndiCamelServletContextListener}} then the {{CamelContextLifecycle}} must use the {{JndiRegistry}} as well. And likewise if the servlet is {{org.apache.camel.component.servletlistener.SimpleCamelServletContextListener}} then the {{CamelContextLifecycle}} must use the {{SimpleRegistry}} 

h3. See Also
- [Servlet]
- [Servlet Tomcat Example]
- [Servlet Tomcat No Spring Example]