EL

Overview

The Unified Expression Language (EL) was originally specified as part of the JSP 2.1 standard (JSR-245), but it is now available as a standalone language. Apache Camel integrates with JUEL (http://juel.sourceforge.net/), which is an open source implementation of the EL language.

Adding JUEL package

To use EL in your routes you need to add a dependency on camel-juel to your project as shown in Example 5, “Adding the camel-juel dependency”.

Example 5. Adding the camel-juel dependency

<!-- Maven POM File -->
<properties>
  <camel-version>2.17.0.redhat-630187</camel-version>
  ...
</properties>

<dependencies>
  ...
  <dependency>
    <groupId>org.apache.camel</groupId>
    <artifactId>camel-juel</artifactId>
    <version>${camel-version}</version>
  </dependency>
  ...
</dependencies>

Static import

To use the el() static method in your application code, include the following import statement in your Java source files:

import static org.apache.camel.language.juel.JuelExpression.el;

Variables

Table 4, “EL variables” lists the variables that are accessible when using EL.

Table 4. EL variables

Variable	Type	Value
`exchange`	`org.apache.camel.Exchange`	The current Exchange
`in`	`org.apache.camel.Message`	The IN message
`out`	`org.apache.camel.Message`	The OUT message

Example

Example 6, “Routes using EL” shows two routes that use EL.

Example 6. Routes using EL

<camelContext>
  <route>
    <from uri="seda:foo"/>
    <filter>
      <language language="el">${in.headers.foo == 'bar'}</language>
      <to uri="seda:bar"/>
    </filter>
  </route>
  <route>
    <from uri="seda:foo2"/>
    <filter>
      <language language="el">${in.headers['My Header'] == 'bar'}</language>
      <to uri="seda:bar"/>
    </filter>
  </route>
</camelContext>