int类型转换成User对象类型报错问题 User u=(User) req.getSession().getAttribute("servlet");

Question

private void UserUpdate(HttpServletRequest req, HttpServletResponse resp) throws IOException {

            String pwd=req.getParameter("pwd");
            //下面的User的转换报错
            User u=(User) req.getSession().getAttribute("servlet");
            int uid=u.getUid();

            int index=us.Update(pwd,uid);
            System.out.println("index="+index);
            if(index>0){

                HttpSession hs=req.getSession();
                hs.setAttribute("pwd","true");

                resp.sendRedirect("/Login.jsp");
            }

Servlet.service() for servlet [servlet] in context with path [/New] threw exception
java.lang.ClassCastException: java.lang.Integer cannot be cast to com.cwj.pojo.User
    at com.cwj.servlet.UserServlet.UserUpdate(UserServlet.java:88)
    at com.cwj.servlet.UserServlet.service(UserServlet.java:41)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:731)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:303)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
    at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
    at org.apache.logging.log4j.core.web.Log4jServletFilter.doFilter(Log4jServletFilter.java:66)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:219)
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:110)
    at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:494)
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:169)
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:104)
    at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:1025)
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:116)
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:445)
    at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1137)
    at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:637)
    at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:319)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
    at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
    at java.lang.Thread.run(Thread.java:748)

Answer 1

User u=(User) req.getSession().getAttribute("servlet");
这里必须保证 req.getSession().setAttribute("servlet",xxx) ，xxx 处放入一个 User 类型的对象。
这样才能相互转换，找到你set 的地方修改一下换成User 类型。