不能将StandardWrapperFacade转换为S_Config.ServletConfig

Question

嘿，我创建了一个简单的ServletConfig示例，其中有3个文件-- index.htm、ServletConfig.java和web.xml。但在运行该项目时，我得到了以下错误：

HTTP Status 500 - org.apache.catalina.core.StandardWrapperFacade cannot be cast to S_Config.ServletConfig

type Exception report

message org.apache.catalina.core.StandardWrapperFacade cannot be cast to S_Config.ServletConfig

description The server encountered an internal error that prevented it from fulfilling this request.

exception

java.lang.ClassCastException: org.apache.catalina.core.StandardWrapperFacade cannot be cast to S_Config.ServletConfig
    S_Config.ServletConfig.doPost(ServletConfig.java:25)
    javax.servlet.http.HttpServlet.service(HttpServlet.java:648)
    javax.servlet.http.HttpServlet.service(HttpServlet.java:729)
    org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)

note The full stack trace of the root cause is available in the Apache Tomcat/8.0.28 logs.

可以帮我一个忙。我的ServletCongif.java文件就像这个

package S_Config; 
import javax.servlet.http.*;

import java.io.IOException;
import java.io.PrintWriter;
import javax.servlet.ServletException;

/**
 *
 * @author user
 */
public class ServletConfig extends HttpServlet {

    @Override
    protected void doPost(HttpServletRequest req,HttpServletResponse res) throws ServletException, IOException {

        res.setContentType("text/html");
        PrintWriter pw = res.getWriter();

        ServletConfig conf = (ServletConfig) getServletConfig();

        String s1 = conf.getInitParameter("n1");
        String s2= conf.getInitParameter("n2"); 

        pw.println("The value of n1 is"+s1+" "+"The value of n2 is "+s2);

        pw.close();

    }


}

Answer 1

在书写时更改类名:-

ServletConfig conf = (ServletConfig) getServletConfig();

你应该使用的是ServletConfig类，而不是你的