（重點）JavaWeb（入門篇18）過濾器Filter實現Servlet亂碼問題案例

一、過濾器Filter實現Servlet亂碼問題案例

1. 實現功能，

添加一個過濾器，實現所有訪問 /filter/* 映射下的Servlet都
解決中文亂碼問題

2.核心代碼

注意一定要轉釋放不然其他Servlet拿不到請求。

servletRequest.setCharacterEncoding("utf-8");
servletResponse.setCharacterEncoding("utf-8");
servletResponse.setContentType("text/html;charset=UTF-8");
filterChain.doFilter(servletRequest,servletResponse);//轉發給其他過濾器或者Servlet(釋放)

3.框架

4.代碼

文件目錄

1.Filter.java 過濾器

package com.bmft.filter;

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

/**
 * 過濾器步驟
 * 1.導包：到一個正確Servlet下的包，實現 Filter
 * 2.實現方法都Filter
 * （1）實現過濾
 * （2）釋放
 * 3.配置過濾器web.xml
 */
public class Filter01 implements Filter {
    public void init(FilterConfig filterConfig) throws ServletException {
        System.out.println("=====過濾器初始化=====");
    }

    public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
        System.out.println("=====過濾開始=====");
        servletRequest.setCharacterEncoding("utf-8");
        servletResponse.setCharacterEncoding("utf-8");
        servletResponse.setContentType("text/html;charset=UTF-8");
        filterChain.doFilter(servletRequest,servletResponse);//轉發給其他過濾器或者Servlet
        System.out.println("=====轉發完成，過濾結束======");
    }

    public void destroy() {
        System.out.println("====過濾器銷燬=====");
    }
}

2.測試Servlet，Test01.java

package com.bmft;

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

public class Test01 extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        resp.getWriter().write("<h1>半畝方塘</h1>");
    }

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

3. web.xml 映射配置

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns="http://xmlns.jcp.org/xml/ns/javaee"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_4_0.xsd"
         version="4.0">
    <servlet>
        <servlet-name>Test01</servlet-name>
        <servlet-class>com.bmft.Test01</servlet-class>
    </servlet>
    <servlet-mapping>
        <servlet-name>Test01</servlet-name>
        <url-pattern>/Test01</url-pattern>
    </servlet-mapping>
    <!--加上過濾器的映射-->
    <servlet-mapping>
        <servlet-name>Test01</servlet-name>
        <url-pattern>/filter/Test01</url-pattern>
    </servlet-mapping>
    <!--過濾器filter映射-->
    <filter>
        <filter-name>Filter01</filter-name>
        <filter-class>com.bmft.filter.Filter01</filter-class>
    </filter>
    <filter-mapping>
        <filter-name>Filter01</filter-name>
        <!--/filter下的所有映射都將被過濾包括/filter/Test01-->
        <url-pattern>/filter/*</url-pattern>
    </filter-mapping>

</web-app>

5.頁面展示

1.沒有過濾的訪問

2.過濾後的訪問

3.控制檯的輸出