Filter过滤器处理JSP中文乱码

1.实现过滤器代码；
2.在项目web.xml文件添加过滤器标记<filter>和<filter-mapping>；
注意：前台页面设置contentType的charset值与web.xml里设置的值一致。

详细配置步骤

1.实现过滤器代码

package com.sp.Tools;

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.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class EncodingFilter implements Filter {
    // 定义默认字符雿
    private String encoding = "utf-8";

    public void init(FilterConfig filterConfig) throws ServletException {
        // 从web.xml文件中读取字符集;
        encoding = filterConfig.getInitParameter("encoding");
    }

    public void doFilter(ServletRequest request, ServletResponse response,
            FilterChain chain) throws IOException, ServletException {
        HttpServletRequest httpRequest = (HttpServletRequest) request;
        HttpServletResponse httpResponse = (HttpServletResponse) response;
        // 设置请求的字符集
        httpRequest.setCharacterEncoding(encoding);
        // 设置响应的字符集
        httpResponse.setCharacterEncoding(encoding);
        chain.doFilter(httpRequest, httpResponse);
    }

    public void destroy() {

    }

}

2.在项目web.xml文件添加过滤器标记<filter>和<filter-mapping>；

          <filter>
      <!--过滤器名称，自己起 -->
      <filter-name>EncodingFilter</filter-name>
      <!--过滤器类名称，包括包名一致、写全 -->
      <filter-class>com.sp.Tools.EncodingFilter</filter-class> 
      <init-param><!--初始化参数,要指定的字符集编码 -->
      
      <param-name>encoding</param-name><!--参数名称 -->
      <param-value>utf-8</param-value> <!--参数值 --> 
      </init-param>
      </filter>
      <filter-mapping>
      <filter-name>EncodingFilter</filter-name>
      <url-pattern>/*</url-pattern> <!--“/*”表示项目下所有资源 -->
      </filter-mapping>    

注意：如果实现上述仍有乱码，可能是一下原因：

url="jdbc:mysql://localhost:3306/spdb1?characterEncoding=utf-8"

（红色字体如果没有，加上尝试一下）

ct = DriverManager.getConnection(url,"root","root");