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大数据必学Java基础（一百一十一）：过滤器注解应用和开发案例

JAVA案例应用基础数据开发 注解 过滤器
2023-06-13 09:16:09 时间

​过滤器注解应用和开发案例

一、过滤器注解应用

@WebFilter属性

package com.lanson.filter;
import javax.servlet.*;
import javax.servlet.annotation.WebFilter;
import javax.servlet.annotation.WebInitParam;
import java.io.IOException;
/**
 * @Author: Lansonli
 * @Description: MircoMessage:Mark_7001
 */
@WebFilter(urlPatterns = "/myServlet1.do")
public class Filter0_MyFilter implements Filter {
    @Override
    public void init(FilterConfig filterConfig) throws ServletException {
    }
    @Override
    public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
        System.out.println("MyFilter0   在过滤请求 ");
        filterChain.doFilter(servletRequest,servletResponse);
        System.out.println("MyFilter0   在过滤响应");
    }
    @Override
    public void destroy() {
    }
}

package com.lanson.filter;
import javax.servlet.*;
import javax.servlet.annotation.WebFilter;
import javax.servlet.annotation.WebInitParam;
import java.io.IOException;
import java.util.Enumeration;
/**
 * @Author: Lansonli
 * @Description: MircoMessage:Mark_7001
 */
@WebFilter(urlPatterns = "/myServlet1.do",initParams = {@WebInitParam(name="realname",value ="zhangsan"),@WebInitParam(name="charset",value ="utf-8")})
public class Filter1_MyFilter implements Filter {
    @Override
    public void init(FilterConfig filterConfig) throws ServletException {
        // 获取初始化的一些参数
        String realname = filterConfig.getInitParameter("realname");
        System.out.println("realname:"+realname);
        Enumeration<String> pNames = filterConfig.getInitParameterNames();
        while(pNames.hasMoreElements()){
            String pName = pNames.nextElement();
            System.out.println(pName+":"+filterConfig.getInitParameter(pName));
        }
    }
    @Override
    public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
        System.out.println("MyFilter1   在过滤请求 ");
        filterChain.doFilter(servletRequest,servletResponse);
        System.out.println("MyFilter1   在过滤响应");
    }
    @Override
    public void destroy() {
    }
}

二、开发案例

1、准备页面login.jsp

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
  <head>
    <title>$Title%sSourceCode%lt;/title>
  </head>
  <body>
  please login ... ... <br/>
  <form action="loginController.do" method="post">
    用户名:<input type="text" name="user"> <br/>
    密码:<input type="password" name="pwd"><br/>
    <input type="submit" value="提交">
  </form>
  </body>
</html>

2、准备servlet，LoginController

package com.lanson.controller;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
/**
 * @Author: Lansonli
 * @Description: MircoMessage:Mark_7001
 */
@WebServlet(urlPatterns = "/loginController.do")
public class LoginController extends HttpServlet {
    @Override
    protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        // 获取用户名和密码
        String user = req.getParameter("user");
        String pwd = req.getParameter("pwd");
        System.out.println(user);
        System.out.println(pwd);
    }
}

3、准备过滤器

package com.lanson.filter;
import javax.servlet.*;
import javax.servlet.annotation.WebFilter;
import java.io.IOException;
/**
 * @Author: Lansonli
 * @Description: MircoMessage:Mark_7001
 */
public class Filter0_EncodingFilter implements Filter {
    private String charset;
    @Override
    public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
        servletRequest.setCharacterEncoding(charset);
        // 放行
        filterChain.doFilter(servletRequest, servletResponse);
    }
    @Override
    public void init(FilterConfig filterConfig) throws ServletException {
        charset = filterConfig.getInitParameter("charset");
    }
    @Override
    public void destroy() {
    }
}

4、配置过滤器

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns="http://xmlns.jcp.org/xml/ns/javaee"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_4_0.xsd"
         version="4.0">
    <filter>
        <filter-name>encodingFilter</filter-name>
        <filter-class>com.lanson.filter.Filter0_EncodingFilter</filter-class>
        <init-param>
            <param-name>charset</param-name>
            <param-value>UTF-8</param-value>
        </init-param>
    </filter>
    <filter-mapping>
        <filter-name>encodingFilter</filter-name>
        <url-pattern>*.do</url-pattern>
    </filter-mapping>
</web-app>

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