JavaWeb学习笔记9——使用过滤器解决乱码

目录

一、过滤器概述

二、利用过滤器解决乱码问题

三、截图

四、总结

---

一、过滤器概述

Filter意为滤镜或者过滤器，用于在Servlet之外对request或者response进行修改。Filter提出了滤镜链的概念，一个FilterChain包含多个Filter。客户端请求request在到达Servlet之前会经过所有Filter，而服务器响应response在从Servlet抵达客户端浏览器之前也会经过这些Filter。Filter就好比是客户端浏览器和服务器之间的一张网。

二、利用过滤器解决乱码问题

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 请求到服务器的编码格式
		request.setCharacterEncoding("UTF-8");
		//response 响应到页面的编码格式
		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();
		//获取参数
		User=request.getParameter("username");
		Password=request.getParameter("password");

		out.print("欢迎 : " + User+",您的密码是:"+Password);
		out.close();
	}

}

web.xml

  MessyTest
  
    index.html
    index.htm
    index.jsp
    default.html
    default.htm
    default.jsp
  
  
  
      EncodingFilter
      com.hedong.filter.EncodingFilter
  
  
      EncodingFilter
      /*
  
  

login.html

	


		账号:

		
 密码:

		
 

	

三、截图

在没有使用过滤器之前

在使用过滤器之后

四、总结

Filter是一个很有弹性的机制，功能强大，经典案例有防盗链Filter、字符编码Filter、日志记录Filter、异常捕捉Filter、权限验证Filter、内容替换Filter、GZIP压缩Filter、图像水印Filter、缓存Filter、XSLT转换Filter、文件上传Filter等。