# Annotating the Code

JAX-WS relies on the annotation feature of Java 5. The JAX-WS annotations are used to specify the metadata used to map the SEI to a fully specified service definition. Among the information provided in the annotations are the following:

* The target namespace for the service.

* The name of the class used to hold the request message.

* The name of the class used to hold the response message.

* If an operation is a one way operation.

* The binding style the service uses.

* The name of the class used for any custom exceptions.

* The namespaces under which the types used by the service are defined.

  Information noteNote: Most of the annotations have sensible defaults and do not need to be specified. However, the more information you provide in the annotations, the better defined your service definition. A solid service definition increases the likely hood that all parts of a distributed application will work together.

### In this section

* [Required Annotations](https://help.qlik.com/talend/en-US/esb-service-developer-guide/7.3/required-annotations)
* [Optional Annotations](https://help.qlik.com/talend/en-US/esb-service-developer-guide/7.3/optional-annotations)