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javaWeb 过滤器

爱奔跑的读书者 2022-01-20 阅读 100

过滤器架构:

过滤器实现案例:

servlet类:

package com.wxl.jsp;

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

配置好以后直接运行:

 可以看到乱码

配置过滤器:

package com.wxl.filter;

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

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
    @Override
    public void init(FilterConfig filterConfig) throws ServletException {
        System.out.println("CharacterEncodingFilter初始化");
    }

    //Chain : 链
    /*
    1、过滤器的所有代码,在过滤特定请求的时候都会执行
    2、必须要让过滤器继续同行
     */
    @Override
    public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
       servletRequest.setCharacterEncoding("utf-8");
       servletResponse.setCharacterEncoding("utf-8");
       servletResponse.setContentType("text/html;charset=UTF-8");

        System.out.println("CharacterEncodingFilter执行前...");
        //让我们的请求继续走,如果不写,程序到这里就被拦截停止了!
        filterChain.doFilter(servletRequest,servletResponse);
        System.out.println("CharacterEncodingFilter执行后...");
    }

    //销毁: web服务器关闭的时候,过滤器会销毁
    @Override
    public void destroy() {
        System.out.println("CharacterEncodingFilter销毁");
    }
}

这里导包一定不要导错!

在web.xml里同样要配置:

    <filter>
        <filter-name>CharacterEncodingFilter</filter-name>
        <filter-class>com.wxl.filter.CharacterEncodingFilter</filter-class>
    </filter>

    <filter-mapping>
        <filter-name>CharacterEncodingFilter</filter-name>
        <!--只要是网站的请求都要经过该过滤器-->
        <url-pattern>/*</url-pattern>
    </filter-mapping>

配置好过滤器以后再访问:

 乱码已解决!

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