9.3. Message Composition

9.3.1. Message Composers

A MessageComposer composes or decomposes a native binding message to or from SwitchYard's canonical message. It does so in three steps:
  1. Construct a new target message instance.
  2. Copy the content of the message.
  3. Delegate the header/property mapping to a ContextMapper.
A SOAPMessageComposer and CamelMessageComposer are included with SwitchYard. These implementations are used by their associated bindings but you can override these with your own implementations.

9.3.2. Create a Custom Message Composer

Procedure 9.2. Create a Custom Message Composer

  1. Implement the org.switchyard.component.common.composer.MessageComposer interface: 
    public interface MessageComposer<T> {
    ContextMapper<T> getContextMapper();
    MessageComposer<T> setContextMapper(ContextMapper<T> contextMapper);
    Message compose(T source, Exchange exchange, boolean create) throws Exception;
    public T decompose(Exchange exchange, T target) throws Exception;
}
  2. Specify your implementation in your switchyard.xml file: 
    <binding.xyz ...>
    <messageComposer class="com.example.MyMessageComposer"/>
</binding.xyz>

9.3.3. Custom Message Composer Properties

  • The getContextMapper() and setContextMapper() methods are bean properties. If you extend BaseMessageComposer, both properties are implemented for you.
  • Your compose() method needs to take the data from the passed-in source native message and compose a SwitchYard Message based on the specified Exchange. The create parameter determines whether or not we ask the Exchange to create a new Message, or use the existing one.
  • Your decompose() method needs to take the data from the SwitchYard Message in the specified Exchange and "decompose it" into the target native message.