9.2. Content Filter

Overview

The content filter pattern describes a scenario where you need to filter out extraneous content from a message before delivering it to its intended recipient. For example, you might employ a content filter to strip out confidential information from a message.

Figure 9.2. Content Filter Pattern

Content filter pattern
A common way to filter messages is to use an expression in the DSL, written in one of the supported scripting languages (for example, XSLT, XQuery or JoSQL).

Implementing a content filter

A content filter is essentially an application of a message processing technique for a particular purpose. To implement a content filter, you can employ any of the following message processing techniques:

XML configuration example

The following example shows how to configure the same route in XML: 
<camelContext xmlns="http://camel.apache.org/schema/spring">
  <route>
    <from uri="activemq:My.Queue"/>
    <to uri="xslt:classpath:com/acme/content_filter.xsl"/>
    <to uri="activemq:Another.Queue"/>
  </route>
</camelContext>

Using an XPath filter

You can also use XPath to filter out part of the message you are interested in: 
<route>
  <from uri="activemq:Input"/>
  <setBody><xpath resultType="org.w3c.dom.Document">//foo:bar</xpath></setBody>
  <to uri="activemq:Output"/>
</route>