Building Web Services with Jakarta XML Web Services

This chapter describes Jakarta XML Web Services, a technology for building web services and clients that communicate using XML. XML Web Services allows developers to write message-oriented as well as Remote Procedure Call–oriented (RPC-oriented) web services.

Overview of Jakarta XML Web Services

In Jakarta XML Web Services, a web service operation invocation is represented by an XML-based protocol, such as SOAP. The SOAP specification defines the envelope structure, encoding rules, and conventions for representing web service invocations and responses. These calls and responses are transmitted as SOAP messages (XML files) over HTTP.

Although SOAP messages are complex, the XML Web Services API hides this complexity from the application developer. On the server side, the developer specifies the web service operations by defining methods in an interface written in the Java programming language. The developer also codes one or more classes that implement those methods. Client programs are also easy to code. A client creates a proxy (a local object representing the service) and then simply invokes methods on the proxy. With XML Web Services, the developer does not generate or parse SOAP messages. It is the XML Web Services runtime system that converts the API calls and responses to and from SOAP messages.

With XML Web Services, clients and web services have a big advantage: the platform independence of the Java programming language. In addition, XML Web Services is not restrictive: A XML Web Services client can access a web service that is not running on the Java platform and vice versa. This flexibility is possible because XML Web Services uses technologies defined by the W3C: HTTP, SOAP, and WSDL. WSDL specifies an XML format for describing a service as a set of endpoints operating on messages.

Several files in the XML Web Services examples depend on the port that you specified when you installed GlassFish Server. These tutorial examples assume that the server runs on the default port, 8080. They do not run with a nondefault port setting.

Creating a Simple Web Service and Clients with XML Web Services

This section shows how to build and deploy a simple web service and two clients: an application client and a web client. The source code for the service is in the jakartaee-examples/tutorial/jaxws/helloservice-war/ directory, and the clients are in the jakartaee-examples/tutorial/jaxws/hello-appclient/ and jakartaee-examples/tutorial/jaxws/hello-webclient/ directories.

Figure 1, “Communication between a XML Web Service and a Client” illustrates how XML Web Services technology manages communication between a web service and a client.

Diagram showing a client and web service communicating through a SOAP message.

Figure 1. Communication between a XML Web Service and a Client

The starting point for developing a XML Web Services web service is a Java class annotated with the jakarta.jws.WebService annotation. The @WebService annotation defines the class as a web service endpoint.

A service endpoint interface or service endpoint implementation (SEI) is a Java interface or class, respectively, that declares the methods that a client can invoke on the service. An interface is not required when building a XML Web Services endpoint. The web service implementation class implicitly defines an SEI.

You may specify an explicit interface by adding the endpointInterface element to the @WebService annotation in the implementation class. You must then provide an interface that defines the public methods made available in the endpoint implementation class.

Basic Steps for Creating a Web Service and Client

The basic steps for creating a web service and client are as follows.

Code the implementation class.
Compile the implementation class.
Package the files into a WAR file.
Deploy the WAR file. The web service artifacts, which are used to communicate with clients, are generated by GlassFish Server during deployment.
Code the client class.
Use the wsimport Maven goal to generate and compile the web service artifacts needed to connect to the service.
Compile the client class.
Run the client.

If you use NetBeans IDE to create a service and client, the IDE performs the wsimport task for you.

The sections that follow cover these steps in greater detail.

Requirements of a XML Web Services Endpoint

XML Web Services endpoints must follow these requirements.

The implementing class must be annotated with either the jakarta.jws.WebService or the jakarta.jws.WebServiceProvider annotation.
The implementing class may explicitly reference an SEI through the endpointInterface element of the @WebService annotation but is not required to do so. If no endpointInterface is specified in @WebService, an SEI is implicitly defined for the implementing class.
The business methods of the implementing class must be public and must not be declared static or final.
Business methods that are exposed to web service clients must be annotated with jakarta.jws.WebMethod.
Business methods that are exposed to web service clients must have Jakarta XML Binding-compatible parameters and return types. See the list of Jakarta XML Binding default data type bindings in Types Supported by XML Web Services.
The implementing class must not be declared final and must not be abstract.
The implementing class must have a default public constructor.
The implementing class must not define the finalize method.
The implementing class may use the jakarta.annotation.PostConstruct or the jakarta.annotation.PreDestroy annotations on its methods for lifecycle event callbacks.

The @PostConstruct method is called by the container before the implementing class begins responding to web service clients.

The @PreDestroy method is called by the container before the endpoint is removed from operation.

Coding the Service Endpoint Implementation Class

In this example, the implementation class, Hello, is annotated as a web service endpoint using the @WebService annotation. Hello declares a single method named sayHello, annotated with the @WebMethod annotation, which exposes the annotated method to web service clients. The sayHello method returns a greeting to the client, using the name passed to it to compose the greeting. The implementation class also must define a default, public, no-argument constructor.

package ee.jakarta.tutorial.helloservice;

import jakarta.jws.WebService;
import jakarta.jws.WebMethod;

@WebService
public class Hello {
    private final String message = "Hello, ";

    public Hello() {
    }

    @WebMethod
    public String sayHello(String name) {
        return message + name + ".";
    }
}

Building, Packaging, and Deploying the Service

You can use either NetBeans IDE or Maven to build, package, and deploy the helloservice-war application.

To Build, Package, and Deploy the Service Using NetBeans IDE

Make sure that GlassFish Server has been started (see Starting and Stopping GlassFish Server).
From the File menu, choose Open Project.
In the Open Project dialog box, navigate to:
```
jakartaee-examples/tutorial/jaxws
```
Select the helloservice-war folder.
Click Open Project.
In the Projects tab, right-click the helloservice-war project and select Run.

This command builds and packages the application into a WAR file, helloservice-war.war, located in jakartaee-examples/tutorial/jaxws/helloservice-war/target/, and deploys this WAR file to your GlassFish Server instance. It also opens the web service test interface at the URL shown in To Test the Service without a Client.

You can view the WSDL file of the deployed service by requesting the URL http://localhost:8080/helloservice-war/HelloService?wsdl in a web browser. Now you are ready to create a client that accesses this service.

To Build, Package, and Deploy the Service Using Maven

Make sure that GlassFish Server has been started (see Starting and Stopping GlassFish Server).

In a terminal window, go to:

jakartaee-examples/tutorial/jaxws/helloservice-war/

Enter the following command:
```
mvn install
```
This command builds and packages the application into a WAR file, helloservice-war.war, located in the target directory, and then deploys the WAR to GlassFish Server.

Testing the Methods of a Web Service Endpoint

GlassFish Server allows you to test the methods of a web service endpoint.

To Test the Service without a Client

To test the sayHello method of HelloService, follow these steps.

Open the web service test interface by entering the following URL in a web browser:
```
http://localhost:8080/helloservice-war/HelloService?Tester
```
Under Methods, enter a name as the parameter to the sayHello method.
Click sayHello.

This takes you to the sayHello Method invocation page.

Under Method returned, you’ll see the response from the endpoint.

A Simple XML Web Services Application Client

The HelloAppClient class is a stand-alone application client that accesses the sayHello method of HelloService. This call is made through a port, a local object that acts as a proxy for the remote service. The port is created at development time by the wsimport Maven goal, which generates XML Web Services portable artifacts based on a WSDL file.

Coding the Application Client

When invoking the remote methods on the port, the client performs these steps.

It uses the generated helloservice.endpoint.HelloService class, which represents the service at the URI of the deployed service’s WSDL file:

import ee.jakarta.tutorial.helloservice.endpoint.HelloService;
import jakarta.xml.ws.WebServiceRef;

public class HelloAppClient {
    @WebServiceRef(wsdlLocation =
      "http://localhost:8080/helloservice-war/HelloService?WSDL")
    private static HelloService service;
    ...
}

It retrieves a proxy to the service, also known as a port, by invoking getHelloPort on the service:
```
ee.jakarta.tutorial.helloservice.endpoint.Hello port = service.getHelloPort();
```
The port implements the SEI defined by the service.
It invokes the port’s sayHello method, passing a string to the service:
```
return port.sayHello(arg0);
```

Here is the full source of HelloAppClient.java, which is located in the jakartaee-examples/tutorial/jaxws/hello-appclient/src/main/java/ee/jakarta/tutorial/hello/appclient/ directory:

package ee.jakarta.tutorial.hello.appclient;

import ee.jakarta.tutorial.helloservice.endpoint.HelloService;
import jakarta.xml.ws.WebServiceRef;

public class HelloAppClient {
    @WebServiceRef(wsdlLocation =
      "http://localhost:8080/helloservice-war/HelloService?WSDL")
    private static HelloService service;

    /**
     * @param args the command line arguments
     */
    public static void main(String[] args) {
       System.out.println(sayHello("world"));
    }

    private static String sayHello(java.lang.String arg0) {
        ee.jakarta.tutorial.helloservice.endpoint.Hello port =
                service.getHelloPort();
        return port.sayHello(arg0);
    }
}

Running the Application Client

You can use either NetBeans IDE or Maven to build, package, deploy, and run the hello-appclient application. To build the client, you must first have deployed helloservice-war, as described in Building, Packaging, and Deploying the Service.

To Run the Application Client Using NetBeans IDE

From the File menu, choose Open Project.
In the Open Project dialog box, navigate to:
```
jakartaee-examples/tutorial/jaxws
```
Select the hello-appclient folder.
Click Open Project.
In the Projects tab, right-click the hello-appclient project and select Build.

This command runs the wsimport goal, then builds, packages, and runs the client. You will see the output of the application client in the hello-appclient output tab:
```
--- exec-maven-plugin:1.2.1:exec (run-appclient) @ hello-appclient ---
Hello, world.
```

To Run the Application Client Using Maven

In a terminal window, go to:

jakartaee-examples/tutorial/jaxws/hello-appclient/

Enter the following command:
```
mvn install
```
This command runs the wsimport goal, then builds, packages, and runs the client. The application client output looks like this:
```
--- exec-maven-plugin:1.2.1:exec (run-appclient) @ hello-appclient ---
Hello, world.
```

A Simple XML Web Services Web Client

HelloServlet is a servlet that, like the Java client, calls the sayHello method of the web service. Like the application client, it makes this call through a port.

Coding the Servlet

To invoke the method on the port, the client performs these steps.

It imports the HelloService endpoint and the WebServiceRef annotation:

import ee.jakarta.tutorial.helloservice.endpoint.HelloService;
...
import jakarta.xml.ws.WebServiceRef;

It defines a reference to the web service by specifying the WSDL location:

@WebServiceRef(wsdlLocation =
  "http://localhost:8080/helloservice-war/HelloService?WSDL")

It declares the web service, then defines a private method that calls the sayHello method on the port:

private HelloService service;
...
private String sayHello(java.lang.String arg0) {
    ee.jakarta.tutorial.helloservice.endpoint.Hello port =
            service.getHelloPort();
    return port.sayHello(arg0);
}

In the servlet, it calls this private method:

out.println("<p>" + sayHello("world") + "</p>");

The significant parts of the HelloServlet code follow. The code is located in the jakartaee-examples/tutorial/jaxws/hello-webclient/src/java/ee/jakarta/tutorial/hello/ webclient/ directory.

package ee.jakarta.tutorial.hello.webclient;

import ee.jakarta.tutorial.helloservice.endpoint.HelloService;
import java.io.IOException;
import java.io.PrintWriter;
import jakarta.servlet.ServletException;
import jakarta.servlet.annotation.WebServlet;
import jakarta.servlet.http.HttpServlet;
import jakarta.servlet.http.HttpServletRequest;
import jakarta.servlet.http.HttpServletResponse;
import jakarta.xml.ws.WebServiceRef;

@WebServlet(name="HelloServlet", urlPatterns={"/HelloServlet"})
public class HelloServlet extends HttpServlet {
    @WebServiceRef(wsdlLocation =
      "http://localhost:8080/helloservice-war/HelloService?WSDL")
    private HelloService service;

    /**
     * Processes requests for both HTTP <code>GET</code>
     *   and <code>POST</code> methods.
     * @param request servlet request
     * @param response servlet response
     * @throws ServletException if a servlet-specific error occurs
     * @throws IOException if an I/O error occurs
     */
    protected void processRequest(HttpServletRequest request,
            HttpServletResponse response)
    throws ServletException, IOException {
        response.setContentType("text/html;charset=UTF-8");
        try (PrintWriter out = response.getWriter()) {

            out.println("<html lang=\"en\">");
            out.println("<head>");
            out.println("<title>Servlet HelloServlet</title>");
            out.println("</head>");
            out.println("<body>");
            out.println("<h1>Servlet HelloServlet at " +
                request.getContextPath () + "</h1>");
            out.println("<p>" + sayHello("world") + "</p>");
            out.println("</body>");
            out.println("</html>");
        }
    }

    // doGet and doPost methods, which call processRequest, and
    //   getServletInfo method

    private String sayHello(java.lang.String arg0) {
        ee.jakarta.tutorial.helloservice.endpoint.Hello port =
                service.getHelloPort();
        return port.sayHello(arg0);
    }
}

Running the Web Client

You can use either NetBeans IDE or Maven to build, package, deploy, and run the hello-webclient application. To build the client, you must first have deployed helloservice-war, as described in Building, Packaging, and Deploying the Service.

To Run the Web Client Using NetBeans IDE

From the File menu, choose Open Project.
In the Open Project dialog box, navigate to:
```
jakartaee-examples/tutorial/jaxws
```
Select the hello-webclient folder.
Click Open Project.
In the Projects tab, right-click the hello-webclient project and select Build.

This task runs the wsimport goal, builds and packages the application into a WAR file, hello-webclient.war, located in the target directory, and deploys it to GlassFish Server.
In a web browser, enter the following URL:
```
http://localhost:8080/hello-webclient/HelloServlet
```
The output of the sayHello method appears in the window.

To Run the Web Client Using Maven

In a terminal window, go to:

jakartaee-examples/tutorial/jaxws/hello-webclient/

Enter the following command:
```
mvn install
```
This command runs the wsimport goal, then build and packages the application into a WAR file, hello-webclient.war, located in the target directory. The WAR file is then deployed to GlassFish Server.
In a web browser, enter the following URL:
```
http://localhost:8080/hello-webclient/HelloServlet
```
The output of the sayHello method appears in the window.

Types Supported by XML Web Services

XML Web Services delegates the mapping of Java programming language types to and from XML definitions to Jakarta XML Binding. Application developers don’t need to know the details of these mappings but should be aware that not every class in the Java language can be used as a method parameter or return type in XML Web Services.

The following sections explain the default schema-to-Java and Java-to-schema data type bindings:

Schema-to-Java Mapping
Java-to-Schema Mapping

Schema-to-Java Mapping

The Java language provides a richer set of data types than XML schema. Mapping of XML Data Types to Java Data Types lists the mapping of XML data types to Java data types.

Mapping of XML Data Types to Java Data Types
XML Schema Type	Java Data Type
`xsd:string`	`java.lang.String`
`xsd:integer`	`java.math.BigInteger`
`xsd:int`	`int`
`xsd.long`	`long`
`xsd:short`	`short`
`xsd:decimal`	`java.math.BigDecimal`
`xsd:float`	`float`
`xsd:double`	`double`
`xsd:boolean`	`boolean`
`xsd:byte`	`byte`
`xsd:QName`	`javax.xml.namespace.QName`
`xsd:dateTime`	`javax.xml.datatype.XMLGregorianCalendar`
`xsd:base64Binary`	`byte[]`
`xsd:hexBinary`	`byte[]`
`xsd:unsignedInt`	`long`
`xsd:unsignedShort`	`int`
`xsd:unsignedByte`	`short`
`xsd:time`	`javax.xml.datatype.XMLGregorianCalendar`
`xsd:date`	`javax.xml.datatype.XMLGregorianCalendar`
`xsd:g`	`javax.xml.datatype.XMLGregorianCalendar`
`xsd:anySimpleType`	`java.lang.Object`
`xsd:anySimpleType`	`java.lang.String`
`xsd:duration`	`javax.xml.datatype.Duration`
`xsd:NOTATION`	`javax.xml.namespace.QName`

Java-to-Schema Mapping

Mapping of Java Classes to XML Data Types shows the default mapping of Java classes to XML data types.

Mapping of Java Classes to XML Data Types
Java Class	XML Data Type
`java.lang.String`	`xs:string`
`java.math.BigInteger`	`xs:integer`
`java.math.BigDecimal`	`xs:decimal`
`java.util.Calendar`	`xs:dateTime`
`java.util.Date`	`xs:dateTime`
`javax.xml.namespace.QName`	`xs:QName`
`java.net.URI`	`xs:string`
`javax.xml.datatype.XMLGregorianCalendar`	`xs:anySimpleType`
`javax.xml.datatype.Duration`	`xs:duration`
`java.lang.Object`	`xs:anyType`
`java.awt.Image`	`xs:base64Binary`
`jakarta.activation.DataHandler`	`xs:base64Binary`
`javax.xml.transform.Source`	`xs:base64Binary`
`java.util.UUID`	`xs:string`

Web Services Interoperability and Jakarta XML Web Services

Jakarta XML Web Services supports the Web Services Interoperability (WS-I) Basic Profile Version 1.1. The WS-I Basic Profile is a document that clarifies the SOAP 1.1 and WSDL 1.1 specifications to promote SOAP interoperability. For links related to WS-I, see Further Information about Jakarta XML Web Services.

To support WS-I Basic Profile Version 1.1, the JAX-WS runtime supports doc/literal and rpc/literal encodings for services, static ports, dynamic proxies, and the Dynamic Invocation Interface (DII).

Further Information about Jakarta XML Web Services

For more information about Jakarta XML Web Services and related technologies, see

Jakarta XML Web Services 3.0 specification:
https://jakarta.ee/specifications/xml-web-services/3.0/
Jakarta XML Web Services home:
https://eclipse-ee4j.github.io/metro-jax-ws/
Simple Object Access Protocol (SOAP) 1.2 W3C Note:
https://www.w3.org/TR/soap/
Web Services Description Language (WSDL) 1.1 W3C Note:
https://www.w3.org/TR/wsdl
WS-I Basic Profile 1.2 and 2.0:
http://www.ws-i.org