Servlet過濾器處理中文亂碼問題

目錄

一 Filter開發步驟

二 實戰

三 測試結果

---

一 Filter開發步驟

1 導包

2 編寫過濾器

二 實戰

1 編寫Servlet，用於測試

package com.cakin.servlet;


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


/**
* @ClassName: ShowSevlet
* @Description: 測試亂碼Servlet
* @Date: 2020/6/14
* @Author: cakin
*/
public class ShowServlet extends HttpServlet {
    /**
     * 功能描述：構造亂碼
     *
     * @author cakin
     * @date 2020/6/14
     * @param req 請求
     * @param resp 響應
     * @throws IOException 異常
     */
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws IOException {
        resp.getWriter().write("解決過濾器亂碼問題");
    }


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

2 編寫過濾器，防止產生中文亂碼

package com.cakin.filter;


import javax.servlet.Filter;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.FilterChain;
import java.io.IOException;


/**
* @ClassName: CharacterEncodingFilter
* @Description: 解決中文亂碼問題
* @Date: 2020/6/14
* @Author: cakin
*/
public class CharacterEncodingFilter implements Filter {
    /**
     * 功能描述：初始化
     *
     * @author cakin
     * @date 2020/6/14
     * @param filterConfig 過濾器配置
     * @throws ServletException ServletException
     * @description: web啓動就會初始化，同Tomcat一起啓動
     */
    public void init(FilterConfig filterConfig) throws ServletException {
        System.out.println("CharacterEncodingFilter 初始化");
    }


    /**
     * 功能描述：過濾器核心方法
     *
     * @param request  請求
     * @param response 響應
     * @param chain    過濾器鏈
     * @throws IOException      IOException
     * @throws ServletException IOException
     * @author cakin
     * @date 2020/6/14
     * @description: 關鍵點
     * 1 針對特定的請求，過濾器會執行，這個特定的請求是在web.xml中配置過濾器
     * 2 爲了讓程序繼續往下走，必須執行 chain.doFilter(request, response);
     */
    public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {
        // 處理亂碼問題
        request.setCharacterEncoding("utf-8");
        response.setCharacterEncoding("utf-8");
        response.setContentType("text/html;charset=UTF-8");
        System.out.println("執行前");
        // 讓我們的程序繼續往下走，否則程序就在這裏停止了
        chain.doFilter(request, response);
        System.out.println("執行後");
    }
    /**
     * 功能描述：過濾器銷燬
     *
     * @author cakin
     * @date 2020/6/14
     * @description: web服務器停止時，會執行這個函數
     */
    public void destroy() {
        System.out.println("CharacterEncodingFilter 銷燬");
    }
}

3 編寫web.xml，配置Servlet和Filter

<?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>ShowServlet</servlet-name>
        <servlet-class>com.cakin.servlet.ShowServlet</servlet-class>
    </servlet>
    <servlet-mapping>
        <servlet-name>ShowServlet</servlet-name>
        <!--這個路徑會走到下面配置的過濾器-->
        <url-pattern>/servlet/show</url-pattern>
    </servlet-mapping>
    <servlet-mapping>
        <servlet-name>ShowServlet</servlet-name>
        <url-pattern>/show</url-pattern>
        <!--這個路徑不會走到下面配置的不會走過濾器-->
    </servlet-mapping>
    
    <filter>
        <filter-name>EncodingFilter</filter-name>
        <filter-class>com.cakin.filter.CharacterEncodingFilter</filter-class>
    </filter>


    <filter-mapping>
        <filter-name>EncodingFilter</filter-name>
        <!-- /servlet請求都會走這個過濾器-->
        <url-pattern>/servlet/*</url-pattern>
    </filter-mapping>
</web-app>

三 測試結果

1 當訪問 http://localhost:8080/servlet/show

2 當訪問 http://localhost:8080/show