Question

我的Servlet代码：

@WebServlet(description = "A simple", urlPatterns = { "/SimpleServlet" })
public class SimpleServlet extends HttpServlet {
    private static final long serialVersionUID = 1L;

   /**
     * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
     */
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

        response.setContentType("text/html");
        PrintWriter wr = response.getWriter();
        String uname = request.getParameter("unam");
        HttpSession ses = request.getSession(); 

        if (uname != "" && uname != "null") {
            ses.setAttribute("userses", ses);   
        }

        wr.println("In RequestHttp method your name is "+ uname);
        wr.println("In Sesssion method  your name is " + (String)ses.getAttribute("userses"));
    }
}

`Apache Tom Cat 7：0错误严重：servlet的Servlet.service（） [org.sathish.brains.SimpleServlet]与路径的上下文 [/ SimpleServletProject]抛出异常java.lang.ClassCastException： org.apache.catalina.session.StandardSessionFacade无法强制转换为 java.lang.String at org.sathish.brains.SimpleServlet.doGet（SimpleServlet.java:37）at at javax.servlet.http.HttpServlet.service（HttpServlet.java:621）at at javax.servlet.http.HttpServlet.service（HttpServlet.java:728）at at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter（ApplicationFilterChain.java:305）在 org.apache.catalina.core.ApplicationFilterChain.doFilter（ApplicationFilterChain.java:210）在 org.apache.tomcat.websocket.server.WsFilter.doFilter（WsFilter.java:52）在 org.apache.catalina.core.ApplicationFilterChain.internalDoFilter（ApplicationFilterChain.java:243）在 org.apache.catalina.core.ApplicationFilterChain.doFilter（ApplicationFilterChain.java:210）在 org.apache.catalina.core.StandardWrapperValve.invoke（StandardWrapperValve.java:222）在 org.apache.catalina.core.StandardContextValve.invoke（StandardContextValve.java:123）在 org.apache.catalina.authenticator.AuthenticatorBase.invoke（AuthenticatorBase.java:502）在 org.apache.catalina.core.StandardHostValve.invoke（StandardHostValve.java:171）在 org.apache.catalina.valves.ErrorReportValve.invoke（ErrorReportValve.java:100）在 org.apache.catalina.valves.AccessLogValve.invoke（AccessLogValve.java:953）在 org.apache.catalina.core.StandardEngineValve.invoke（StandardEngineValve.java:118）在 org.apache.catalina.connector.CoyoteAdapter.service（CoyoteAdapter.java:409）在 org.apache.coyote.http11.AbstractHttp11Processor.process（AbstractHttp11Processor.java:1044）在 org.apache.coyote.AbstractProtocol $ AbstractConnectionHandler.process（AbstractProtocol.java:607）在 org.apache.tomcat.util.net.JIoEndpoint $ SocketProcessor.run（JIoEndpoint.java:313）在 java.util.concurrent.ThreadPoolExecutor.runWorker（ThreadPoolExecutor.java:1145）在 java.util.concurrent.ThreadPoolExecutor中的$ Worker.run（ThreadPoolExecutor.java:615）在java.lang.Thread.run（Thread.java:744）

Answer 1

看看这一行：

    ses.setAttribute("userses", ses);

您将自己的会话作为属性传递。我认为您尝试做的事情就像是

    ses.setAttribute("userses", uname);

Answer 2

if (uname != "" && uname != "null") {
    ses.setAttribute("userses", ses);   
}

您真的想要将会话添加到会话中吗？我怀疑，您可能希望将属性设置为uname。更加注意你的代码。

将转换移除到String，这是不必要的。

在您尝试编写servlet代码之前，认真了解Java的基础知识。

将对象转换为String运行时Apache错误：

2 个答案: