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Using Data Formats with Dozer

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<endpoint uri="dozer:xml2json?marshalId=myjson&amp;unmarshalId=myjaxb&amp;targetModel=org.example.Order"/>

Configuring Dozer

All Dozer endpoints require a Dozer mapping configuration file which defines mappings between source and target objects.  The component will default to a location of META-INF/dozerBeanMapping.xml if the mappingFile or mappingConfiguration options are not specified on an endpoint.  If you need to supply multiple mapping configuration files for a single endpoint or specify additional configuration options (e.g. event listeners, custom converters, etc.), then you can use an instance of org.apache.camel.converter.dozer.DozerBeanMapperConfiguration.

<bean id="mapper" class="org.apache.camel.converter.dozer.DozerBeanMapperConfiguration">  
  <property name="mappingFiles">
    <list>
      <value>mapping1.xml</value>
      <value>mapping2.xml</value>
    </list>
  </property>
</bean>

Mapping Extensions

The Dozer component implements a number of extensions to the Dozer mapping framework as custom converters.  These converters implement mapping functions that are not supported directly by Dozer itself.

Variable Mappings

Variable mappings allow you to map the value of a variable definition within a Dozer configuration into a target field instead of using the value of a source field.  This is equivalent to constant mapping in other mapping frameworks, where can you assign a literal value to a target field.  To use a variable mapping, simply define a variable within your mapping configuration and then map from the VariableMapper class into your target field of choice:

<mappings xmlns="http://dozer.sourceforge.net" 
  xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  xsi:schemaLocation="http://dozer.sourceforge.net http://dozer.sourceforge.net/schema/beanmapping.xsd">
  <configuration>
    <variables>
      <variable name="CUST_ID">ACME-SALES</variable>
    </variables>
  </configuration>
  <mapping>
    <class-a>org.apache.camel.component.dozer.VariableMapper</class-a>
    <class-b>org.example.Order</class-b>
    <field custom-converter-id="_variableMapping" custom-converter-param="${CUST_ID}">
      <a>literal</a>
      <b>custId</b>
    </field>
  </mapping>
</mappings>

Custom Mappings

Custom mappings allow you to define your own logic for how a source field is mapped to a target field.  They are similar in function to Dozer customer converters, with two notable differences:

• You can have multiple converter methods in a single class with custom mappings.
• There is no requirement to implement a Dozer-specific interface with custom mappings.

A custom mapping is declared by using the built-in '_customMapping' converter in your mapping configuration.  The parameter to this converter has the following syntax:

[class-name][,method-name]

Method name is optional - the Dozer component will search for a method that matches the input and output types required for a mapping.  An example custom mapping and configuration are provided below.

public class CustomMapper {
    // All customer ids must be wrapped in "[ ]"
    public Object mapCustomer(String customerId) {
        return "[" + customerId + "]";
    }
} 

<mappings xmlns="http://dozer.sourceforge.net" 
  xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  xsi:schemaLocation="http://dozer.sourceforge.net http://dozer.sourceforge.net/schema/beanmapping.xsd">
  <mapping>
    <class-a>org.example.A</class-a>
    <class-b>org.example.B</class-b>
    <field custom-converter-id="_customMapping" 
	    custom-converter-param="org.example.CustomMapper,mapCustomer">
      <a>header.customerNum</a>
      <b>custId</b>
    </field>
  </mapping>
</mappings>

Expression Mappings

Expression mappings allow you to use the powerful language capabilities of Camel to evaluate an expression and assign the result to a target field in a mapping.  Any language that Camel supports can be used in an expression mapping.  Basic examples of expressions include the ability to map a Camel message header or exchange property to a target field or to concatenate multiple source fields into a target field.  The syntax of a mapping expression is:

[language]:[expression]

An example of mapping a message header into a target field:

<mappings xmlns="http://dozer.sourceforge.net" 
  xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  xsi:schemaLocation="http://dozer.sourceforge.net http://dozer.sourceforge.net/schema/beanmapping.xsd">
  <mapping>
    <class-a>org.apache.camel.component.dozer.ExpressionMapper</class-a>
    <class-b>org.example.B</class-b>
    <field custom-converter-id="_expressionMapping" custom-converter-param="simple:\${header.customerNumber}">
      <a>expression</a>
      <b>custId</b>
    </field>
  </mapping>
</mappings>

Note that any properties within your expression must be escaped with "\" to prevent an error when Dozer attempts to resolve variable values defined using the EL.