基于REST的Web服务及其基于Ajax的客户端

　　清单 2. 使用 HTTP GET 调用雇员详细信息

　　　　　　　　<?xml version='1.0' encoding='UTF-8'?>
< EmpDetail xmlns:p='http://www.employee-details.com'>
　　　　　　　　<<Emp-ID>00345</Emp-ID>
　　　　<Name>David Henry</Name>
　　　　　　　 <Department>Finance</ Department >
</p:EmpDetail>

　　清单 3 显示了这个 Servlet 的代码。其中，所有操作都采用了硬编码方式，但是可以很容易地将其扩展为与数据库进行交互，以便成为一个实时的、基于 REST 的服务。

　　清单 3. Servlet 代码

public class RESTDemoServlet extends HttpServlet implements Servlet {
/* (non-Java-doc)
　* @see javax.servlet.http.HttpServlet#HttpServlet()
　*/
Map map =new HashMap();
　　
/* (non-Javadoc)
　* @see javax.servlet.GenericServlet#init()
　*/
public void init() throws ServletException {
　// TODO Auto-generated method stub
　super.init();
　　　　
　Employee emp0 =new Employee("David","Finance");
　Employee emp1 =new Employee("Smith","HealthCare");
　Employee emp2 =new Employee("Adam","Information technology");
　Employee emp3 =new Employee("Stephan","Life Sciences");
　　　　
　map.put("00345",emp0);
　map.put("00346",emp1);
　map.put("00347",emp2);
　map.put("00348",emp3);
}
　　
/* (non-Java-doc)
　* @see javax.servlet.http.HttpServlet#doGet
　　　(HttpServletRequest arg0, HttpServletResponse arg1)
　*/
protected void doGet(HttpServletRequest arg0, HttpServletResponse arg1)
　　　throws ServletException, IOException {
　// TODO Auto-generated method stub
　arg1.setContentType("text/xml");
　PrintWriter out=arg1.getWriter();
　System.out.println(map);
　if(arg0.getPathInfo()!= null){
　String EmpId=arg0.getPathInfo().substring(1,arg0.getPathInfo().length());
　System.out.println(EmpId);
　　　　
　out.write("<?xml version='1.0' encoding='UTF-8'? >"+"
");
　 out.write("<p:EmpDetail xmlns:p='http://www.employee-details.com' >"+"
");
　 out.write("<Emp-ID>"+EmpId+" </Emp-ID >"+"
");
　 out.write("<Name>"+((Employee)map.get(EmpId)).name+" </Name >"+"
");
　 out.write("<Department >"+((Employee)map.get(EmpId)).dept+" </Department >"+"
");
　 out.write("</p:EmpDetail >"+"
");
　 out.flush();
　}else{
　 out.write("<?xml version='1.0' encoding='UTF-8'? >"+"
");
　 out.write("<p:Employees xmlns:p='http://www.employee-details.com' >"+"
");
　 out.write("<Employee id='00345' href='http://localhost:9080/
　　　AJAX_REST_Demo/RESTDemoServlet/employees/00345'/ >"+"
");
　 out.write("<Employee id='00346' href='http://localhost:9080/
　　　AJAX_REST_Demo/RESTDemoServlet/employees/00346'/ >"+"
");
　 out.write("<Employee id='00347' href='http://localhost:9080/
　　　AJAX_REST_Demo/RESTDemoServlet/employees/00347'/ >"+"
");
　 out.write("<Employee id='00348' href='http://localhost:9080/
　　　AJAX_REST_Demo/RESTDemoServlet/employees/00348'/ >"+"
");
　 out.write("</p:Employees >");
　 out.flush();
　}
}
/* (non-Java-doc)
　* @see javax.servlet.http.HttpServlet#doPost
　　　(HttpServletRequest arg0, HttpServletResponse arg1)
　*/
protected void doPost(HttpServletRequest arg0, HttpServletResponse arg1)
　　　throws ServletException, IOException {
　// TODO Auto-generated method stub
}
　　
}