Filter练习一

短命女 2023-08-17 17:41 53阅读 0赞

![1642540-20190716145255965-670059807.png][]

## 1.创建两个Filter过滤器UserNameFilter/PassWordFilter ##

**2.进行Filter的注册和配置**

**3.Filter初始化参数和web应用的初始化参数**

**4.在Filter中完成信息比较**

**实现效果：**

**![1642540-20190716151842031-716005058.png][]**

![1642540-20190716151906471-1628816390.png][]

![1642540-20190716151919039-40365183.png][]

**实现代码：**

**UserNameFilter**

package com.demo.filter;
    
    import javax.servlet.*;
    import java.io.IOException;
    
    public class UserNameFilter  implements Filter {
    
        private FilterConfig filterConfig;
    
        @Override
        public void init(FilterConfig filterConfig) throws ServletException {
            this.filterConfig = filterConfig;
        }
    
        @Override
        public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
           String initUser = filterConfig.getInitParameter("username");
           String username = servletRequest.getParameter("username");
    
           if (!initUser.equals(username)){
               servletRequest.setAttribute("message","用户名不正确");
               servletRequest.getRequestDispatcher("login.jsp").forward(servletRequest,servletResponse);
               return;
           }
           filterChain.doFilter(servletRequest,servletResponse);
        }
    
        @Override
        public void destroy() {
    
        }
    }

**PassWordFilter**

package com.demo.filter;
    
    import javax.servlet.*;
    import java.io.IOException;
    
    public class PassWordFilter implements Filter {
        @Override
        public void init(FilterConfig filterConfig) throws ServletException {
            this.filterConfig = filterConfig;
        }
    
        private FilterConfig filterConfig;
        @Override
        public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
            String initPassword = filterConfig.getServletContext().getInitParameter("password");
            String password = servletRequest.getParameter("password");
            if (!initPassword.equals(password)){
                servletRequest.setAttribute("message","密码不正确");
                servletRequest.getRequestDispatcher("login.jsp").forward(servletRequest,servletResponse);
                return;
            }
            filterChain.doFilter(servletRequest,servletResponse);
        }
    
        @Override
        public void destroy() {
    
        }
    }

**web.xml**

<filter>
            <filter-name>UserNameFilter</filter-name>
            <filter-class>com.demo.filter.UserNameFilter</filter-class>
            <init-param>
                <param-name>username</param-name>
                <param-value>Tom</param-value>
            </init-param>
        </filter>
        <filter-mapping>
            <filter-name>UserNameFilter</filter-name>
            <url-pattern>/filter/hello.jsp</url-pattern>
        </filter-mapping>
    
        <filter>
            <filter-name>PassWordFilter</filter-name>
            <filter-class>com.demo.filter.PassWordFilter</filter-class>
        </filter>
        <filter-mapping>
            <filter-name>PassWordFilter</filter-name>
            <url-pattern>/filter/hello.jsp</url-pattern>
        </filter-mapping>
    
        <context-param>
            <param-name>password</param-name>
            <param-value>1234</param-value>
        </context-param>

**login.jsp**

<%--
      Created by IntelliJ IDEA.
      User: dell
      Date: 2019/7/16
      Time: 14:54
      To change this template use File | Settings | File Templates.
    --%>
    <%@ page contentType="text/html;charset=UTF-8" language="java" %>
    <html>
    <head>
        <title>Title</title>
    </head>
    <body>
    <font color="red">
        ${message}
    </font>
    <br><br>
    <form action="hello.jsp" method="post">
        username: <input type="text" name="username" value="${param.username}">
        password: <input type="password" name="password">
    
        <input type="submit" value="Submit">
    </form>
    </body>
    </html>

**hello.jsp**

<%--
      Created by IntelliJ IDEA.
      User: dell
      Date: 2019/7/16
      Time: 14:57
      To change this template use File | Settings | File Templates.
    --%>
    <%@ page contentType="text/html;charset=UTF-8" language="java" %>
    <html>
    <head>
        <title>Title</title>
    </head>
    <body>
    
    
        Hello:${param.username}
    </body>
    </html>

转载于:https://www.cnblogs.com/yangHS/p/11195149.html

[1642540-20190716145255965-670059807.png]: /images/20230808/656e756342f14f1290209b5f9381515f.png
[1642540-20190716151842031-716005058.png]: /images/20230808/a7030276e3e34120a27c2e1b18a5c3cf.png
[1642540-20190716151906471-1628816390.png]: /images/20230808/d994d80f9aef473f8a6dfaaf21f59504.png
[1642540-20190716151919039-40365183.png]: /images/20230808/403d4e94293447a194e0d4b8ebf5bd2f.png