Creating the SEI

The service endpoint interface (SEI) is the piece of Java code that is shared between a service and the consumers that make requests on it. It 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 up to a developer to create the SEI.

There are two basic patterns for creating an SEI:

Green field development

You are developing a new service from the ground up. When starting fresh, it is best to start by creating the SEI first. You can then distribute the SEI to any developers that are responsible for implementing the services and consumers that use the SEI.

	Note
	The recommended way to do green field service development is to start by creating a WSDL contract that defines the service and its interfaces. See Part II, “Starting from WSDL”.

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 will need to 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.

	Note
	You can add the JAX-WS annotations to a Java class, but that is not recommended.

Writing the interface

The SEI is a standard Java interface. It defines a set of methods that a class will implement. 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.

	Tip
	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 such methods out of the SEI.

Example 1.1, “Simple SEI” shows a simple SEI for a stock updating service.

Example 1.1. Simple SEI

package com.iona.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 just a standard Java class. If you started with a Java class you will need to modify it to implement the interface. If you are starting fresh, the implementation class will need to implement the SEI.

Example 1.2, “Simple Implementation Class” shows a class for implementing the interface in Example 1.1, “Simple SEI”.

Example 1.2. Simple Implementation Class

package com.iona.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);
  }
}

^[1]Board is an assumed class whose implementation is left to the reader.