9.3. Normalizer

Overview

The normalizer pattern is used to process messages that are semantically equivalent, but arrive in different formats. The normalizer transforms the incoming messages into a common format.
In Apache Camel, you can implement the normalizer pattern by combining a content-based router, which detects the incoming message's format, with a collection of different message translators, which transform the different incoming formats into a common format.

Figure 9.3. Normalizer Pattern

Normalizer pattern

Java DSL example

This example shows a Message Normalizer that converts two types of XML messages into a common format. Messages in this common format are then filtered.
Using the Fluent Builders
// we need to normalize two types of incoming messages
from("direct:start")
    .choice()
        .when().xpath("/employee").to("bean:normalizer?method=employeeToPerson")
        .when().xpath("/customer").to("bean:normalizer?method=customerToPerson")
    .end()
    .to("mock:result");
In this case we're using a Java bean as the normalizer. The class looks like this
// Java
public class MyNormalizer {
    public void employeeToPerson(Exchange exchange, @XPath("/employee/name/text()") String name) {
        exchange.getOut().setBody(createPerson(name));            
    }

    public void customerToPerson(Exchange exchange, @XPath("/customer/@name") String name) {
        exchange.getOut().setBody(createPerson(name));
    }        
    
    private String createPerson(String name) {
        return "<person name=\" + name + \"/>";
    }
}

XML configuration example

The same example in the XML DSL
<camelContext xmlns="http://camel.apache.org/schema/spring">
  <route>
    <from uri="direct:start"/>
    <choice>
      <when>
        <xpath>/employee</xpath>
        <to uri="bean:normalizer?method=employeeToPerson"/>
      </when>
      <when>
        <xpath>/customer</xpath>
        <to uri="bean:normalizer?method=customerToPerson"/>
      </when>
    </choice>
    <to uri="mock:result"/>
  </route> 
</camelContext>

<bean id="normalizer" class="org.apache.camel.processor.MyNormalizer"/>