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1.实现页面的跳转:对于LoginServlet.java 采用直接实现的Servlet接口的方式
web.xml
1 <?xml version="1.0" encoding="UTF-8"?> 2 <web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 3 xmlns="http://java.sun.com/xml/ns/javaee" 4 xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd" 5 id="WebApp_ID" version="3.0"> 6 7 <!-- 配置web应用的初始化参数 --> 8 <context-param> 9 <param-name>user</param-name> 10 <param-value>jason</param-value> 11 </context-param> 12 13 <context-param> 14 <param-name>password</param-name> 15 <param-value>zhangzhen</param-value> 16 </context-param> 17 18 <!-- 配置和映射servlet --> 19 <servlet> 20 <servlet-name>LoginServlet</servlet-name> 21 <servlet-class>com.jason.testweb.LoginServlet</servlet-class> 22 </servlet> 23 24 <servlet-mapping> 25 <servlet-name>LoginServlet</servlet-name> 26 <url-pattern>/login</url-pattern> <!-- 和提表单提交的 action 一致 --> 27 </servlet-mapping> 28 29 </web-app>
login.html
1 <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> 2 <html> 3 <head> 4 <meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> 5 <title>this is a test </title> 6 </head> 7 <body> 8 <form action="login" method="post"> 9 10 user:<input type="text" name="username"/> 11 password:<input type="text" name="password"/> 12 13 <input type="submit" value="submit"/> 14 15 </form> 16 </body> 17 </html>
LoginServlet.java
1 package com.jason.testweb;
2
3 import java.io.IOException;
4 import java.io.PrintWriter;
5
6 import javax.servlet.Servlet;
7 import javax.servlet.ServletConfig;
8 import javax.servlet.ServletContext;
9 import javax.servlet.ServletException;
10 import javax.servlet.ServletRequest;
11 import javax.servlet.ServletResponse;
12
13 public class LoginServlet implements Servlet {
14
15 @Override
16 public void destroy() {
17 // TODO Auto-generated method stub
18 }
19
20 @Override
21 public ServletConfig getServletConfig() {
22 // TODO Auto-generated method stub
23 return null;
24 }
25
26 @Override
27 public String getServletInfo() {
28 // TODO Auto-generated method stub
29 return null;
30 }
31
32 private ServletConfig servletConfig; //自定义一个成员变量
33
34 @Override
35 public void init(ServletConfig servletConfig) throws ServletException {
36
37 this.servletConfig = servletConfig;
38
39 }
40
41 @Override
42 public void service(ServletRequest request, ServletResponse response)
43 throws ServletException, IOException {
44 // 1.获取请求参数
45 String userName = request.getParameter("username");
46 String passWord = request.getParameter("password");
47
48 // 2.获取当前web 应用的初始化参数，user，password
49 ServletContext servletContext = servletConfig.getServletContext();
50 String initUser = servletContext.getInitParameter("user");
51 String initPassword = servletContext.getInitParameter("password");
52
53 PrintWriter out = response.getWriter();
54
55 // 3.比对
56 // 4.打印响应字符串
57 if (initUser.equals(userName) && initPassword.equals(passWord)) {
58 out.print("hello :" + userName);
59 } else {
60 out.print("sorry :" + userName);
61 }
62
63 }
64
65 }
2.实现页面的跳转：创建一个MyGenericServlet的类，实现Servlet接口，对于 LoginServlet.java则继承MyGenericServlet类
MyGenericServlet.java
1 package com.jason.testweb;
2
3 import java.io.IOException;
4 import java.util.Enumeration;
5
6 import javax.servlet.GenericServlet;
7 import javax.servlet.Servlet;
8 import javax.servlet.ServletConfig;
9 import javax.servlet.ServletContext;
10 import javax.servlet.ServletException;
11 import javax.servlet.ServletRequest;
12 import javax.servlet.ServletResponse;
13
14 /**
15 *
16 * @author:jason
17 * @time:2016年5月18日
18 * @description:自定义的Servlet 接口的实现类，，简化开发
19 *
20 */
21
22 public abstract class MyGenericServlet implements Servlet {
23
24 @Override
25 public void destroy() {
26 }
27
28 @Override
29 public ServletConfig getServletConfig() {
30 return servletConfig;
31 }
32
33 private ServletConfig servletConfig; // 声明一个成员变量
34
35 @Override
36 public String getServletInfo() {
37 return null;
38 }
39
40 @Override
41 public void init(ServletConfig arg0) throws ServletException {
42 this.servletConfig = arg0;
43 }
44
45 @Override
46 // 声明为抽象方法，由每个继承的类的实现业务
47 public abstract void service(ServletRequest arg0, ServletResponse arg1)
48 throws ServletException, IOException;
49
50 }
LoginServlet.java
1 package com.jason.testweb;
2
3 import java.io.IOException;
4 import java.io.PrintWriter;
5
6 import javax.servlet.Servlet;
7 import javax.servlet.ServletConfig;
8 import javax.servlet.ServletContext;
9 import javax.servlet.ServletException;
10 import javax.servlet.ServletRequest;
11 import javax.servlet.ServletResponse;
12
13 public class LoginServlet extends MyGenericServlet {
14
15 @Override //重写抽象方法
16 public void service(ServletRequest request, ServletResponse response)
17 throws ServletException, IOException {
18 // 1.获取请求参数
19 String userName = request.getParameter("username");
20 String passWord = request.getParameter("password");
21
22 // 2.获取当前web 应用的初始化参数，user，password
23 ServletContext servletContext = getServletConfig().getServletContext();
24 String initUser = servletContext.getInitParameter("user");
25 String initPassword = servletContext.getInitParameter("password");
26
27 PrintWriter out = response.getWriter();
28
29 // 3.比对
30 // 4.打印响应字符串
31 if (initUser.equals(userName) && initPassword.equals(passWord)) {
32 out.print("hello :" + userName);
33 } else {
34 out.print("sorry :" + userName);
35 }
36
37 }
38
39 }
2.关于GenericServlet
public abstract class GenericServlet extends java.lang.Object implements Servlet, ServletConfig, java.io.Serializable
1）是一个Servlet。 是Servlet 接口和ServletConfig 接口的实现类。但是是一个抽象类。其中service 方法为抽象方法
2）如果新建的Servlet 程序直接继承GenericServlet 更加简洁
3）具体实现
①在GenericServlet 中声明了一个ServletConfig 类型的成员变量，在init(ServletConfig) 方法中对其初始化。
②不建议直接覆盖init(ServletConfig) ，因为如果调用super(ServletConfig)，而还有ServletConfig接口的方法，则抛出空指针异常。int(){}方法不是sevlet的声明周期方法。而init(ServletConfig)是servlet的周期方法
1 @Override
2 public void init(ServletConfig config) throws ServletException {
3 this.config = config;
4 this.init();
5 }
6
7 /**
8 * A convenience method which can be overridden so that there‘s no need to
9 * call <code>super.init(config)</code>.
10 * <p>
11 * Instead of overriding {@link #init(ServletConfig)}, simply override this
12 * method and it will be called by
13 * <code>GenericServlet.init(ServletConfig config)</code>. The
14 * <code>ServletConfig</code> object can still be retrieved via
15 * {@link #getServletConfig}.
16 *
17 * @exception ServletException
18 * if an exception occurs that interrupts the servlet‘s
19 * normal operation
20 */
21 public void init() throws ServletException {
22 // NOOP by default
23 }
②利用了servletConfig 成员变量的方法实现了ServletConfig 接口的方法（以下是GenericServlet 的方法源码）
1 @Override
2 public String getInitParameter(String name) {
3 return getServletConfig().getInitParameter(name);
4 }
5
6 @Override
7 public Enumeration<String> getInitParameterNames() {
8 return getServletConfig().getInitParameterNames();
9 }
10
11 @Override
12 public ServletConfig getServletConfig() {
13 return config;
14 }
15
16 @Override
17 public ServletContext getServletContext() {
18 return getServletConfig().getServletContext();
19 }
20
21 @Override
22 public String getServletName() {
23 return config.getServletName();
24 }
3.总结
1）深刻理解servletConfig对象
2）java的封装，继承特性
时间： 2024-12-10 05:08:43