webservices(jax-ws)

Web Services

Develop and Deploy Web Services in Tomcat 6

We shall develop web services in JDK and deploy in Tomcat first, and using IDE tools such as Eclipse and Netbeans later.

Server-Side

Step 1: Implement the Web Service

Let us begin by writing a web service, using JAX-WS (Java API for XML - Web Services) provided in JDK 1.6. JAX-WS is the technology for building web services in Java.

• Write a web service end-point implementation (SEI) class called Hello, in package helloservice. Save your source file as "helloservice\Hello.java". (You cannot use the default package for SEI.)

  package helloservice;
  import javax.jws.WebService;
  import javax.jws.WebMethod;
  /**
   * Web Service End-point implementation class
   */
     
  @WebService
  public class Hello {
     // Constructor
     public void Hello() {}
     
     @WebMethod
     public String sayHello(String name) {
        return "Hello, " + name + ".";
     }
     
     @WebMethod
     public int addNumbers(int number1, int number2) {
        return number1 + number2;
     }
     
     @WebMethod
     public double divideNumbers(int dividend, int divisor)
           throws DivideNumbersException {
        if (divisor == 0) {
           throw new DivideNumbersException("Divisor cannot be zero!");
        }
        return (double)dividend/divisor;
     }
  }
  

  We also need to write the DivideNumbersException used in the above program:

  package helloservice;
  public class DivideNumbersException extends Exception {
     public DivideNumbersException(String message) {
        super(message);
     }
  }
  

  Explanation:
  • The annotation @WebService specifies that this class is meant as a web service.
  • Three methods are annotated with @WebMethod. That is, these methods are accessible by the clients.
• Compile the source codes:

  > cd package-base-directory
  > javac helloservice\*.java
  

• Use JDK's wsgen tool to generate all the portable artifacts needed for web service deployment and invocation, as follows:

  > cd package-base-directory
  > wsgen -classpath . -keep helloservice.Hello
  

  The following classes will be generated in sub-directory jaxws (more precisely, in package helloservice.jaxws). The "-keep" option keeps the generated source files.

  SayHello.class
  SayHelloResponse.class
  AddNumbers.class
  AddNumbersResponse.class
  DivideNumbers.class
  DivideNumbersExceptionBean.class
  DivideNumbersResponse.class
  

  Observe that for each web method exposed, two classes were generated: WebMethod.class and WebMethodResponse.class. An exception bean was further created for theDivideNumbersException.

Step 2: Download and install JAX-WS Runtime for Tomcat

• Download the JAX-WS Runtime from https://jax-ws.dev.java.net. From the "Downloads" link, choose the latest version.
• Download the binary. Unpack the binary by double clicking the downloaded jar file (or run the JDK's jar tool).
• Copy all the jar files from the JAX-WS's "lib" directory to Tomcat's "lib" directory (i.e., "$CATALINA_HOME\lib").

Step 3: Deploy the Web Service in Tomcat

• First, create a context (or web application) called hellows for our web service in Tomcat, by creating a sub-directory called hellows under $CATALINA_HOME\webapps. Also create a subdirectory "WEB-INF" and sub-sub-directory "WEB-INF\classes" under the context root directory.
• Copy all the implementation and generated artifact classes (i.e., the directory helloservice) into "WEB-INF\classes". (Alternatively, you could create and deploy as a sinle WAR (Web Archive) file).
• Write the following web configuration file "web.xml" and save it in "WEB-INF".

  <?xml version="1.0" encoding="UTF-8"?>
  <web-app xmlns="http://java.sun.com/xml/ns/javaee"
     xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
     xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd"
     version="2.5">
     
    <listener>
      <listener-class>com.sun.xml.ws.transport.http.servlet.WSServletContextListener</listener-class>
    </listener>
     
    <servlet>
      <servlet-name>HelloService</servlet-name>
      <servlet-class>com.sun.xml.ws.transport.http.servlet.WSServlet</servlet-class>
      <load-on-startup>1</load-on-startup>
    </servlet>
    
    <servlet-mapping>
      <servlet-name>HelloService</servlet-name>
      <url-pattern>/hello</url-pattern>
    </servlet-mapping>
    
    <session-config>
      <session-timeout>60</session-timeout>
    </session-config>
  </web-app>
  

• Write the following configuration file for JAX-WS called "sun-jaxws.xml" and save it in "WEB-INF" to define the end-points for the web service:

  <?xml version="1.0" encoding="UTF-8"?>
  <endpoints xmlns="http://java.sun.com/xml/ns/jax-ws/ri/runtime" version="2.0">
    <endpoint
      name="HelloService"
      implementation="helloservice.Hello"
      url-pattern="/hello" />
  </endpoints>
  

• Start Tomcat. Observe these messages in Tomcat's console:

  ......
  xxxxx com.sun.xml.ws.transport.http.servlet.WSServletContextListener contextInitialized
  INFO: WSSERVLET12: JAX-WS context listener initializing
  xxxxx com.sun.xml.ws.model.RuntimeModeler getRequestWrapperClass
  INFO: Dynamically creating request wrapper Class helloservice.jaxws.Hello
  xxxxx com.sun.xml.ws.model.RuntimeModeler getResponseWrapperClass
  INFO: Dynamically creating response wrapper bean Class helloservice.jaxws.HelloResponse
  xxxxx com.sun.xml.ws.transport.http.servlet.WSServletDelegate <init>
  INFO: WSSERVLET14: JAX-WS servlet initializing
  ......

• Issue the following URL (assuming that Tomcat is running in port 8080):

  http://localhost:8080/hellows/hello
  

  
• You could click on the WSDL (Web Service Description Language), to study the descriptions about this web service.

Client-Side

Now, a web service has been published. Let us write a client program (in Java) to access this web service.

• Write the following Java standalone program called HelloClient:

  import javax.xml.ws.WebServiceRef;
  import helloservice.HelloService;
  import helloservice.Hello;
     
  public class HelloClient {
     
     @WebServiceRef(wsdlLocation="http://localhost:8080/hellows/hello?wsdl")
     static HelloService service = new HelloService();
     //static HelloService service;
     
     public static void main(String[] args) {
        try {
           System.out.println("Retrieving the port from the following service: "
              + service);
           Hello port = service.getHelloPort();
     
           System.out.println("Invoking the sayHello operation on the port.");
           String response = port.sayHello("World");
           System.out.println(response);
     
           System.out.println("Invoking the addNumbers operation on the port.");
           int sum = port.addNumbers(55, 66);
           System.out.println(sum);
     
           System.out.println("Invoking the divideNumbers operation on the port.");
           double quotient = port.divideNumbers(1, 0);
           System.out.println(quotient);
     
        } catch(Exception e) {
           e.printStackTrace();
        }
     }
  }
  

  Notice that this client program imports some classes from the web service. You cannot compile unless you get these classes.
• Use JDK's wsimport tool to generate the client artifacts (i.e., the service endpoint interface and the service interface classes) (the "-keep" option keep the generated source files):

  wsimport -keep http://localhost:8080/hellows/hello?wsdl
  

  Observe that these classes (in package helloservice) are generated, in particular, HelloService and Hello class which we used in our client program:

  AddNumbers.class
  AddNumbersResponse.class
  DivideNumbers.class
  DivideNumbersException.class
  DivideNumbersException_Exception.class
  DivideNumbersResponse.class
  Hello.class
  HelloResponse.class
  HelloService.class
  Hello_Type.class
  ObjectFactory.class
  package-info.class
  SayHello.class
  SayHelloResponse.class
  

• Compile and run the client program:

  Retrieving the port from the following service: helloservice.HelloService@xxxxxx
  Invoking the sayHello operation on the port.
  Hello, World.
  Invoking the addNumbers operation on the port.
  121
  Invoking the divideNumbers operation on the port.
  helloservice.DivideNumbersException_Exception: Divisor cannot be zero!