JavaWeb-过滤器-Filter

一、过滤器-Filter

• Filter：过滤器，用来过滤网站的数据；
  • 处理中文乱码
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• Filter开发步骤：
  1. 导包
  2. 编写过滤器
     • 导包：import javax.servlet.*;

过滤器类

package com.kuang.filter;

import javax.servlet.*;
import java.io.IOException;

// 实现 Filter接口，重写对应的方法即可
public class CharacterEncodingFilter implements Filter{

	// 初始化：Web服务器启动，就已经初始化了，随时等待过滤对象出现！
	public void init(FilterConfig filterConfig) throws ServletException {
		System.out.println("CharacterEncodingFilter初始化");
	}
	
	// Chain：链
	public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {
		request.setCharacterEncoding("utf-16");
		response.setCharacterEncoding("utf-16");
		
		System.out.println("CharacterEncodingFilter执行前....");
		chain.doFilter(request, response); // 让我们的请求继续走，如果不写，程序到这里就被拦截停止！
		System.out.println("CharacterEncodingFilter执行后....");
	}
	
	// 销毁：Web服务器关闭的时候，过滤会销毁
	public void destroy() {
		System.out.println("CharacterEncodingFilter销毁");
	}
}

实现类

package com.kuang.servlet;

import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class ShowServlet extends HttpServlet{
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
    //		resp.setCharacterEncoding("utf-16");
        resp.getWriter().write("你好呀,世界！");
    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        doGet(req, resp);
    }
}

web.xml文件

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
	xmlns="http://java.sun.com/xml/ns/javaee"
	xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd"
	version="2.5">
	<display-name>javaweb-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>
	
    <!-- 映射实现类 -->
	<servlet>
		<servlet-name>ShowServlet</servlet-name>
		<servlet-class>com.kuang.servlet.ShowServlet</servlet-class>
	</servlet>
	<servlet-mapping>
		<servlet-name>ShowServlet</servlet-name>
		<url-pattern>/servlet/show</url-pattern>
	</servlet-mapping>
	<servlet-mapping>
		<servlet-name>ShowServlet</servlet-name>
		<url-pattern>/show</url-pattern>
	</servlet-mapping>
	
    <!-- 映射过滤类 -->
	<filter>
		<filter-name>CharacterEncodingFilter</filter-name>
		<filter-class>com.kuang.filter.CharacterEncodingFilter</filter-class>
	</filter>
	<filter-mapping>
		<filter-name>CharacterEncodingFilter</filter-name>
		<url-pattern>/servlet/*</url-pattern>
	</filter-mapping>
</web-app>