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A.6. Message Filter

Overview

A message filter, shown in Figure A.3, “Message Filter Pattern”, is a processor that eliminates undesired messages based on specific criteria. Filtering is controlled by specifying a predicate in the filter: when the predicate is true, the incoming message is allowed to pass; otherwise, it is blocked. This pattern maps to the corresponding message filter pattern in Apache Camel.

Figure A.3. Message Filter Pattern

Message filter pattern

Example ServiceMix EIP route

Example A.7, “ServiceMix EIP Message Filter” shows how to define a message filter using the ServiceMix EIP component. Incoming messages are passed through a filter mechanism that blocks messages that lack a test:world element.

Example A.7. ServiceMix EIP Message Filter

<eip:message-filter service="test:messageFilter" endpoint="endpoint">
  <eip:target>
    <eip:exchange-target service="test:trace3" />
  </eip:target>
  <eip:filter>
    <eip:xpath-predicate xpath="count(/test:world) = 1" namespaceContext="#nsContext"/>
  </eip:filter>
</eip:message-filter>

Equivalent Apache Camel XML route

Example A.8, “Apache Camel Message Filter Using XML” shows how to define an equivalent route using Apache Camel XML configuration.

Example A.8. Apache Camel Message Filter Using XML

<route>
  <from uri="jbi:endpoint:http://progress.com/demos/test/messageFilter/endpoint">
  <filter>
   <xpath>count(/test:world) = 1</xpath>
   <to uri="jbi:service:http://progress.com/demos/test/trace3"/>
  </filter>
</route>

Equivalent Apache Camel Java DSL route

Example A.9, “Apache Camel Message Filter Using Java DSL” shows how to define an equivalent route using the Apache Camel Java DSL.

Example A.9. Apache Camel Message Filter Using Java DSL

from("jbi:endpoint:http://progress.com/demos/test/messageFilter/endpoint").
  filter(xpath("count(/test:world) = 1")).
  to("jbi:service:http://progress.com/demos/test/trace3");