javaee中Filter的写法

最新推荐文章于 2024-12-09 21:26:26 发布

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#filter #java ee #html #web.xml

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本文详细介绍了Java Web应用中过滤器的基本概念与实现方法，包括如何创建过滤器类、配置过滤器规则及常见应用场景，如设置编码、验证登录等。

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过滤器
访问某些路径的时候，需要对这些路径进行一个相同的操作，设置一个过滤器
创建过滤器
1.创建一个类，实现过滤器接口javax.servlet.Filter
2.在web.xml中配置过滤器
过滤器链
设置编码过滤
验证登录过滤
验证权限过滤
FilterConfig

常用的过滤器规则
1./*：过滤任何路径
2.过滤指定的文件类型。Html文件
*.html
3.过滤指定目录/mypage/*
4.过滤指定的servlet TestServlet
5.拦截指定的文件/mypage/My.html

MyFilter.java

package filterdome;

import java.io.IOException;

import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;

public class MyFilter implements Filter{

    public void destroy() {
        // TODO Auto-generated method stub
    }

    public void doFilter(ServletRequest request, ServletResponse response,
            FilterChain chain) throws IOException, ServletException {
        // TODO Auto-generated method stub
        System.out.println("进入doFilter()........");
        chain.doFilter(request, response);
    }

    public void init(FilterConfig arg0) throws ServletException {
        System.out.println("执行init()......");

    }

}

配置文件
web.xml

<?xml version="1.0" encoding="UTF-8"?>
<web-app version="2.5" 
    xmlns="http://java.sun.com/xml/ns/javaee" 
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
    xsi:schemaLocation="http://java.sun.com/xml/ns/javaee 
    http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd">
  <display-name></display-name> 
  <servlet>
      <servlet-name>SessionDome</servlet-name>
      <servlet-class>filterdome.SessionDome</servlet-class>
  </servlet>
  <servlet-mapping>
      <servlet-name>SessionDome</servlet-name>
      <url-pattern>/SessionDome</url-pattern>
  </servlet-mapping>
  <filter>
      <filter-name>MyFilter</filter-name>
      <filter-class>filterdome.MyFilter</filter-class>
  </filter>
  <filter-mapping>
      <filter-name>MyFilter</filter-name>
      <url-pattern>/*</url-pattern>
  </filter-mapping>
  <welcome-file-list>
    <welcome-file>index.jsp</welcome-file>
  </welcome-file-list>
</web-app>

servlet文件
SessionDome.java

package filterdome;

import java.io.IOException;
import java.io.PrintWriter;

import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;

public class SessionDome extends HttpServlet {


    public void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        HttpSession session = request.getSession();
        ServletContext application = session.getServletContext();
        session.setAttribute("username", "王");
        application.setAttribute("password", "灿");
        response.setContentType("text/html;charset=utf-8");
        PrintWriter out = response.getWriter();
        out.println("<!DOCTYPE HTML PUBLIC \"-//W3C//DTD HTML 4.01 Transitional//EN\">");
        out.println("<HTML>");
        out.println("  <HEAD><TITLE>A Servlet</TITLE></HEAD>");
        out.println("  <BODY>");
        out.println("session:"+session.getAttribute("username"));
        out.println("application:"+application.getAttribute("password"));
        out.println("  </BODY>");
        out.println("</HTML>");
        out.flush();
        out.close();
    }


    public void doPost(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {

        this.doGet(request, response);
    }

}