24.2. Creating the SEI
Overview
The service endpoint interface (SEI) is the piece of Java code that is shared between a service implementation and the consumers that make requests on that service. The SEI defines the methods implemented by the service and provides details about how the service will be exposed as an endpoint. When starting with a WSDL contract, the SEI is generated by the code generators. However, when starting from Java, it is the developer's responsibility to create the SEI.
There are two basic patterns for creating an SEI:
- Green field development — In this pattern, you are developing a new service without any existing Java code or WSDL. It is best to start by creating the SEI. You can then distribute the SEI to any developers that are responsible for implementing the service providers and consumers that use the SEI.NoteThe recommended way to do green field service development is to start by creating a WSDL contract that defines the service and its interfaces. See Chapter 26, A Starting Point WSDL Contract.
- Service enablement — In this pattern, you typically have an existing set of functionality that is implemented as a Java class, and you want to service enable it. This means that you must do two things:
- Create an SEI that contains only the operations that are going to be exposed as part of the service.
- Modify the existing Java class so that it implements the SEI.
NoteAlthough you can add the JAX-WS annotations to a Java class, it is not recommended.
Writing the interface
The SEI is a standard Java interface. It defines a set of methods that a class implements. It can also define a number of member fields and constants to which the implementing class has access.
In the case of an SEI the methods defined are intended to be mapped to operations exposed by a service. The SEI corresponds to a
wsdl:portType element. The methods defined by the SEI correspond to wsdl:operation elements in the wsdl:portType element.
Note
JAX-WS defines an annotation that allows you to specify methods that are not exposed as part of a service. However, the best practice is to leave those methods out of the SEI.
Example 24.1, “Simple SEI” shows a simple SEI for a stock updating service.
Example 24.1. Simple SEI
package com.fusesource.demo;
public interface quoteReporter
{
public Quote getQuote(String ticker);
}Implementing the interface
Because the SEI is a standard Java interface, the class that implements it is a standard Java class. If you start with a Java class you must modify it to implement the interface. If you start with the SEI, the implementation class implements the SEI.
Example 24.2, “Simple Implementation Class” shows a class for implementing the interface in Example 24.1, “Simple SEI”.
Example 24.2. Simple Implementation Class
package com.fusesource.demo;
import java.util.*;
public class stockQuoteReporter implements quoteReporter
{
...
public Quote getQuote(String ticker)
{
Quote retVal = new Quote();
retVal.setID(ticker);
retVal.setVal(Board.check(ticker));[1]
Date retDate = new Date();
retVal.setTime(retDate.toString());
return(retVal);
}
}