JavaWeb學習筆記9——使用過濾器解決亂碼

目錄

一、過濾器概述

二、利用過濾器解決亂碼問題

三、截圖

四、總結

---

一、過濾器概述

Filter意爲濾鏡或者過濾器，用於在Servlet之外對request或者response進行修改。Filter提出了濾鏡鏈的概念，一個FilterChain包含多個Filter。客戶端請求request在到達Servlet之前會經過所有Filter，而服務器響應response在從Servlet抵達客戶端瀏覽器之前也會經過這些Filter。Filter就好比是客戶端瀏覽器和服務器之間的一張網。

二、利用過濾器解決亂碼問題

EncodingFilter.java

package com.hedong.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.annotation.WebFilter;

/**
 * Servlet Filter implementation class EncodingFilter
 */
@WebFilter("/EncodingFilter")
public class EncodingFilter implements Filter {

    /**
     * Default constructor. 
     */
    public EncodingFilter() {
        // TODO Auto-generated constructor stub
    }

	/**
	 * @see Filter#destroy()
	 */
	public void destroy() {
		// TODO Auto-generated method stub
	}

	/**
	 * @see Filter#doFilter(ServletRequest, ServletResponse, FilterChain)
	 */
	public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {
		// TODO Auto-generated method stub
		// place your code here
		// pass the request along the filter chain

		//request 請求到服務器的編碼格式
		request.setCharacterEncoding("UTF-8");
		//response 響應到頁面的編碼格式
		response.setContentType("text/html;charset=UTF-8");
		chain.doFilter(request, response);
	}

	/**
	 * @see Filter#init(FilterConfig)
	 */
	public void init(FilterConfig fConfig) throws ServletException {
		// TODO Auto-generated method stub
	}

}

LoginServlet.java

package com.hedong.login;

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

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

/**
 * Servlet implementation class LoginServlet
 */
@WebServlet("/LoginServlet")
public class LoginServlet extends HttpServlet {
	private static final long serialVersionUID = 1L;
	private String User;
	private String Password;
       
    /**
     * @see HttpServlet#HttpServlet()
     */
    public LoginServlet() {
        super();
        // TODO Auto-generated constructor stub
    }

	/**
	 * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
	 */
	protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		// TODO Auto-generated method stub
		response.getWriter().append("Served at: ").append(request.getContextPath());
	}

	/**
	 * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
	 */
	protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		// TODO Auto-generated method stub

		PrintWriter out=response.getWriter();
		//獲取參數
		User=request.getParameter("username");
		Password=request.getParameter("password");

		out.print("歡迎 : " + User+",您的密碼是:"+Password);
		out.close();
	}

}

web.xml

<?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>MessyTest</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>
  
  <filter>
      <filter-name>EncodingFilter</filter-name>
      <filter-class>com.hedong.filter.EncodingFilter</filter-class>
  </filter>
  <filter-mapping>
      <filter-name>EncodingFilter</filter-name>
      <url-pattern>/*</url-pattern>
  </filter-mapping>
  
</web-app>

login.html

<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>Insert title here</title>
</head>
<body>
	<form method="post" action="LoginServlet">

		賬號:<input name="username" type="text"><br />
		<br /> 密碼:<input name="password" type="password"><br />
		<br /> <input type="submit" value="登錄">

	</form>
</body>
</html>

三、截圖

在沒有使用過濾器之前

在使用過濾器之後

四、總結

Filter是一個很有彈性的機制，功能強大，經典案例有防盜鏈Filter、字符編碼Filter、日誌記錄Filter、異常捕捉Filter、權限驗證Filter、內容替換Filter、GZIP壓縮Filter、圖像水印Filter、緩存Filter、XSLT轉換Filter、文件上傳Filter等。