簡單的Filter實現

aNoobCoder發表於2017-02-04

1.在xml檔案配置過濾器

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://xmlns.jcp.org/xml/ns/javaee" xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_3_1.xsd" id="WebApp_ID" version="3.1">
  <display-name>Filter</display-name>
  <welcome-file-list>
    <welcome-file>index.html</welcome-file>
    <welcome-file>index.htm</welcome-file>
    <welcome-file>index.jsp</welcome-file>
    <welcome-file>default.html</welcome-file>
    <welcome-file>default.htm</welcome-file>
    <welcome-file>default.jsp</welcome-file>
  </welcome-file-list>

    <error-page>
        <error-code>404</error-code>
        <location>/error.jsp</location>
    </error-page>
    <error-page>
        <error-code>500</error-code>
        <location>/error.jsp</location>
    </error-page>
    <filter>
        <filter-name>CharsetFilter</filter-name>
        <filter-class>com.test.filter.CharsetFilter</filter-class>
        <init-param>
            <param-name>charset</param-name>
            <param-value>UTF-8</param-value>
        </init-param>
    </filter>
    <filter>
        <filter-name>LoginFilter</filter-name>
        <filter-class>com.test.filter.LoginFilter</filter-class>
        <init-param>
            <param-name>noLoginPath</param-name>
            <param-value>login.jsp;error.jsp;index.jsp</param-value>
        </init-param>
    </filter>
    <filter-mapping>
        <filter-name>LoginFilter</filter-name>
        <url-pattern>/*</url-pattern>
        <dispatcher>REQUEST</dispatcher>
    </filter-mapping>
    <filter>
        <filter-name>ErrorFilter</filter-name>
        <filter-class>com.test.filter.ErrorFilter</filter-class>
    </filter>
    <filter-mapping>
        <filter-name>ErrorFilter</filter-name>
        <url-pattern>/error.jsp</url-pattern>
        <dispatcher>ERROR</dispatcher>
    </filter-mapping>
    <filter-mapping>
        <filter-name>CharsetFilter</filter-name>
        <url-pattern>/*</url-pattern>
    </filter-mapping>


</web-app>

2.建立java類實現Filter介面

1.編碼轉換案例

package com.test.filter;

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 CharsetFilter implements Filter{
    private FilterConfig config;
    @Override
    public void destroy() {
        // TODO Auto-generated method stub

    }

    @Override
    public void doFilter(ServletRequest request, ServletResponse response,
            FilterChain chain) throws IOException, ServletException {
        String charset = config.getInitParameter("charset");
        if(charset == null || charset.equals("")){
            charset = "UTF-8";
        }
        request.setCharacterEncoding(charset);
        response.setCharacterEncoding(charset);
        chain.doFilter(request, response);
    }

    @Override
    public void init(FilterConfig arg0) throws ServletException {
        config = arg0;
    }

}

2.錯誤顯示案例

package com.test.filter;

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 ErrorFilter implements Filter{

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

    }

    @Override
    public void doFilter(ServletRequest arg0, ServletResponse arg1,
            FilterChain chain) throws IOException, ServletException {
            System.out.println("error!!!!");
            chain.doFilter(arg0, arg1);

    }

    @Override
    public void init(FilterConfig arg0) throws ServletException {
        // TODO Auto-generated method stub

    }


}

3.登入過濾案例

package com.test.filter;

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;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;

public class LoginFilter implements Filter{
    private FilterConfig config;
    @Override
    public void destroy() {

    }

    @Override
    public void doFilter(ServletRequest arg0, ServletResponse arg1,
            FilterChain chain) throws IOException, ServletException {
        HttpServletRequest request = (HttpServletRequest)arg0;
        HttpServletResponse response = (HttpServletResponse)arg1;
        HttpSession session = request.getSession();

        //獲取不用過濾的路徑
        String noLoginPath = config.getInitParameter("noLoginPath");
        //對於不用過濾的路徑直接放行
        if(noLoginPath != null){
            String[] strArray = noLoginPath.split(";");

            for(String str:strArray){
                if(str == null || str.equals(""))   continue;
                if(request.getRequestURI().indexOf(str) != -1){
                    chain.doFilter(arg0, arg1);
                    return;
                }
            }
        }
        //如果session中沒有使用者資訊就跳轉到登陸介面，否則放行
        if(session.getAttribute("user") == null){
            response.sendRedirect("login.jsp");
        }else{
            chain.doFilter(arg0, arg1);
        }
    }

    @Override
    public void init(FilterConfig arg0) throws ServletException {
        // TODO Auto-generated method stub
        config = arg0;
    }

}

3.建立過濾後顯示的頁面

1.編碼轉換案例

package com.test.filter;

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 CharsetFilter implements Filter{
    private FilterConfig config;
    @Override
    public void destroy() {
        // TODO Auto-generated method stub

    }

    @Override
    public void doFilter(ServletRequest request, ServletResponse response,
            FilterChain chain) throws IOException, ServletException {
        String charset = config.getInitParameter("charset");
        if(charset == null || charset.equals("")){
            charset = "UTF-8";
        }
        request.setCharacterEncoding(charset);
        response.setCharacterEncoding(charset);
        chain.doFilter(request, response);
    }

    @Override
    public void init(FilterConfig arg0) throws ServletException {
        config = arg0;
    }

}

2.錯誤顯示頁面

<%@ page language="java" import="java.util.*" pageEncoding="ISO-8859-1"%>
<%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%>

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
  <head>
    <base href="<%=basePath%>">

    <title>My JSP 'error.jsp' starting page</title>

    <meta http-equiv="pragma" content="no-cache">
    <meta http-equiv="cache-control" content="no-cache">
    <meta http-equiv="expires" content="0">    
    <meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
    <meta http-equiv="description" content="This is my page">
    <!--
    <link rel="stylesheet" type="text/css" href="styles.css">
    -->

  </head>

  <body>
    This is my error page. <br>
  </body>
</html>

3.登入過濾頁面

<%@ page language="java" import="java.util.*" pageEncoding="utf-8"%>
<%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%>

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
  <head>
    <base href="<%=basePath%>">

    <title>My JSP 'success.jsp' starting page</title>

    <meta http-equiv="pragma" content="no-cache">
    <meta http-equiv="cache-control" content="no-cache">
    <meta http-equiv="expires" content="0">    
    <meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
    <meta http-equiv="description" content="This is my page">
    <!--
    <link rel="stylesheet" type="text/css" href="styles.css">
    -->

  </head>

  <body>
    <span><%=request.getParameter("userName") %></span>
    <%System.out.println("userName is "+request.getParameter("userName")); %>
    <span><%=request.getParameter("password") %></span>
    <%System.out.println("pssword is "+request.getParameter("password")); %>
  </body>
</html>

驚呆了，Servlet Filter和Spring MVC Interceptor的實現居然這麼簡單
2020-04-20
ServletFilterSpringMVC
實現簡單的BitMap
2021-06-29
ArrayList的簡單實現
2021-02-21
AOP的簡單實現
2019-01-19
簡單的 HashMap 實現
2018-03-16
HashMap
Promise的簡單實現
2018-01-12
Promise
jQuery filter() 用法簡單介紹
2017-03-16
jQueryFilter
簡單探索Python中的filter函式
2022-07-12
PythonFilter函式
簡單的實現vue原理
2018-10-25
Vue
簡單的實現React原理
2018-10-25
React
java實現簡單的JDBC
2020-12-13
JavaJDBC
php實現簡單的SQLBuilder
2016-07-10
PHPSQLUI
kd樹的簡單實現
2014-10-23
Promise 簡單實現
2019-02-26
Promise
FastClick簡單實現
2021-04-02
AST
Express 簡單實現
2018-07-13
Express
AspectJ簡單實現
2020-10-10
getElementsByClassName簡單實現
2016-12-20
springboot專案結合filter，jdk代理實現敏感詞過濾（簡單版）
2020-09-29
Spring BootFilterJDK
java實現簡單的單點登入
2013-03-29
Java
jQuery實現的簡單投票簡單程式碼例項
2017-03-03
jQuery
互斥鎖mutex的簡單實現
2019-05-12
Mutex
React + Antd實現簡單的todolist
2019-05-01
React
Unity實現簡單的物件池
2022-05-05
Unity物件
Promise 基本方法的簡單實現
2022-02-01
Promise
java實現棧的簡單操作
2018-11-16
Java
簡單、好懂的Svelte實現原理
2021-11-12
前端MVC、MVVM的簡單實現
2018-02-21
前端MVCMVVM
Promise的使用及簡單實現
2018-05-29
Promise
Nginx反向代理的簡單實現
2016-09-04
Nginx
簡單通訊錄的實現
2017-09-25
用go 簡單實現的LRU
2017-07-27
Go
BAPI的簡單實現步驟
2007-07-07
API
精簡版 koa 簡單實現
2018-12-08
感知機簡單實現
2019-10-12
簡單版Promise實現
2019-03-30
Promise
簡單實現vuex原理
2018-10-25
Vue
React 簡單實現（一）
2018-07-27
React

簡單的Filter實現

1.在xml檔案配置過濾器

2.建立java類實現Filter介面

3.建立過濾後顯示的頁面

相關文章