servlet中获取配置文件中的参数.

web.xml (添加init-param)

 1 <?xml version="1.0" encoding="UTF-8"?>
 2 <web-app version="2.5" 
 3     xmlns="http://java.sun.com/xml/ns/javaee" 
 4     xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
 5     xsi:schemaLocation="http://java.sun.com/xml/ns/javaee 
 6     http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd">
 7   <display-name></display-name>
 8   <servlet>
 9     <description>This is the description of my J2EE component</description>
10     <display-name>This is the display name of my J2EE component</display-name>
11     <servlet-name>GetInitParameterServlet</servlet-name>
12     <servlet-class>servlet.GetInitParameterServlet</servlet-class>
13     <init-param>
14         <param-name>username</param-name>
15         <param-value>admin</param-value>
16     </init-param>
17     <init-param>
18         <param-name>password</param-name>
19         <param-value>123456</param-value>
20     </init-param>
21   </servlet>
22 
23   <servlet-mapping>
24     <servlet-name>GetInitParameterServlet</servlet-name>
25     <url-pattern>/servlet/GetInitParameterServlet</url-pattern>
26   </servlet-mapping>    
27   <welcome-file-list>
28     <welcome-file>index.jsp</welcome-file>
29   </welcome-file-list>
30 </web-app>

index.jsp

1   <h1>获取初始化参数演示案例</h1>
2     <hr>
3     <a href="servlet/GetInitParameterServlet">获取初始化Servlet</a>

GetInitParameterServlet.java:

 1 package servlet;
 2 
 3 import java.io.IOException;
 4 import java.io.PrintWriter;
 5 
 6 import javax.servlet.ServletException;
 7 import javax.servlet.http.HttpServlet;
 8 import javax.servlet.http.HttpServletRequest;
 9 import javax.servlet.http.HttpServletResponse;
10 
11 public class GetInitParameterServlet extends HttpServlet {
12     private String username;
13     private String password;    
14         
15     public String getUsername() {
16         return username;
17     }
18 
19     public void setUsername(String username) {
20         this.username = username;
21     }
22 
23     public String getPassword() {
24         return password;
25     }
26 
27     public void setPassword(String password) {
28         this.password = password;
29     }
30 
31     /**
32      * Constructor of the object.
33      */
34     public GetInitParameterServlet() {
35         super();
36     }
37 
38     /**
39      * Destruction of the servlet. <br>
40      */
41     public void destroy() {
42         super.destroy(); // Just puts "destroy" string in log
43         // Put your code here
44     }
45 
46     /**
47      * The doGet method of the servlet. <br>
48      *
49      * This method is called when a form has its tag value method equals to get.
50      * 
51      * @param request the request send by the client to the server
52      * @param response the response send by the server to the client
53      * @throws ServletException if an error occurred
54      * @throws IOException if an error occurred
55      */
56     public void doGet(HttpServletRequest request, HttpServletResponse response)
57             throws ServletException, IOException {
58 
59         doPost(request, response);
60     }
61 
62     /**
63      * The doPost method of the servlet. <br>
64      *
65      * This method is called when a form has its tag value method equals to post.
66      * 
67      * @param request the request send by the client to the server
68      * @param response the response send by the server to the client
69      * @throws ServletException if an error occurred
70      * @throws IOException if an error occurred
71      */
72     public void doPost(HttpServletRequest request, HttpServletResponse response)
73             throws ServletException, IOException {
74 
75         response.setContentType("text/html;charset=utf-8");
76         PrintWriter out = response.getWriter();
77         out.println("<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">");
78         out.println("<HTML>");
79         out.println("  <HEAD><TITLE>A Servlet</TITLE></HEAD>");
80         out.println("  <BODY>");
81     out.println("<h2>用户名:"+this.getUsername()+"</h2>");
82     out.println("<h2>密码:"+this.getPassword()+"</h2>");
83         out.println("  </BODY>");
84         out.println("</HTML>");
85         out.flush();
86         out.close();
87     }
88 
89     /**
90      * Initialization of the servlet. <br>
91      *
92      * @throws ServletException if an error occurs
93      */
94     public void init() throws ServletException {        
95         this.setUsername(this.getInitParameter("username"));
96         this.setPassword(this.getInitParameter("password"));
97     }
98 
99 }