THIS IS A TEST INSTANCE. ALL YOUR CHANGES WILL BE LOST!!!!
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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.
Maven users will need to add the following dependency to their pom.xml for this component:
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Using
You would need to chose one of the following implementations of the abstract class org.apache.camel.component.servletlistener.CamelServletContextListener.
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To use this you need to configure the org.apache.camel.component.servletlistener.CamelServletContextListener in the WEB-INF/web.xml file as shown below:
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Options
The org.apache.camel.component.servletlistener.CamelServletContextListener supports the following options which can be configured as context-param in the web.xml file.
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Option | Type | Description |
|---|---|---|
propertyPlaceholder.XXX |
| To configure property placeholders 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. You should prefix the option with "jmx.", for example to disable JMX, use jmx.disabled as name. You can configure all the options from |
name |
| To configure the name of the CamelContext. |
messageHistory |
| Camel 2.12.2: Whether to enable or disable Message History (enabled by default). |
streamCache |
| Whether to enable Stream caching. |
trace |
| Whether to enable Tracer. |
delayer |
| To set a delay value for Delay Interceptor. |
handleFault |
| Whether to enable handle fault. |
errorHandlerRef |
| Refers to a context scoped Error Handler to be used. |
autoStartup |
| Whether to start all routes when starting Camel. |
useMDCLogging |
| Whether to use MDC logging. |
useBreadcrumb |
| Whether to use breadcrumb. |
managementNamePattern |
| To set a custom naming pattern for JMX MBeans. |
threadNamePattern |
| To set a custom naming pattern for threads. |
properties.XXX |
| To set custom properties on |
routebuilder.XXX |
| To configure routes to be used. See below for more details. |
CamelContextLifecycle |
| Refers to a FQN classname of an implementation of |
XXX |
| To set any option on CamelContext. |
Examples
See Servlet Tomcat No Spring Example.
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The created CamelContext is stored on the ServletContext as an attribute with the key "CamelContext". You can get hold of the CamelContext if you can get hold of the ServletContext as shown below:
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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".
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By default Camel will assume the param-value is a FQN classname for a Camel RouteBuilder class, as shown below:
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You can specify multiple classes in the same param-value as shown below:
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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".
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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:
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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:
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And the XML file is:
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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.
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Here is a snippet of a web.xml configuration for setting up property placeholders to load myproperties.properties from the classpath
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Configuring JMX
Here is a snippet of a web.xml configuration for configuring JMX, such as disabling JMX.
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JNDI or Simple as Camel Registry
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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.
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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.
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As we enlisted our HelloBean Bean using the name "myBean" we can refer to this Bean in the Camel routes as shown below:
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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
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