java.lang.ClassCastException：[Ljava.lang.Object; 不能转换为com.sakhnin.classes.MonthlySummary

Question

我正在尝试打印此MonthlyReport中的所有日期并获得此异常。

严重：servlet showMettingReports的Servlet.service（）引发了异常java.lang.ClassCastException：[Ljava.lang.Object; 无法转发到org.apache.jsp.jspFiles.showMettingReports_jsp._jspService(howMettingReports_jsp.java:150）的com.sakhnin.classes.MonthlySummary org.apache.jasper.runtime.HttpJspBase.service（HttpJspBase.java:70）at位于org.apache.jasper.servlet.JspServletWrapper.service（JspServletWrapper.java:432）的javax.servlet.http.HttpServlet.service（HttpServlet.java:725）org.apache.jasper.servlet.JspServlet.serviceJspFile（JspServlet。 java：396）org.apache.jasper.servlet.JspServlet.service（JspServlet.java:340）at org.apache.catalina.core.ApplicationFilterChain的javax.servlet.http.HttpServlet.service（HttpServlet.java:725） .internalDoFilter（ApplicationFilterChain.java:291）org.apache.catalina.core.ApplicationFilterChain.doFilter（ApplicationFilterChain.java:206）atg.apache.tomcat.websocket.server.WsFilter.doFilter（WsFilter.java:52）at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter（ApplicationFilterChain.java:239）org.apache.catalina.core.ApplicationFilterChain.doFilt 呃（ApplicationFilterChain.java:206）org.apache.catalina.core.ApplicationDispatcher.invoke(ApplicationDispatcher.java:721）org.apache.catalina.core.ApplicationDispatcher.processRequest（ApplicationDispatcher.java:466）atg.apache .catalina.core.ApplicationDispatcher.doForward（ApplicationDispatcher.java:391）atg.apache.catalina.core.ApplicationDispatcher.forward（ApplicationDispatcher.java:318）at com.sakhnin.implementations.Controller.doGet（Controller.java:140） ）在javax.servlet.http.HttpServlet.service（HttpServlet.java:618）的javax.servlet.http.HttpServlet.service（HttpServlet.java:725）org.apache.catalina.core.ApplicationFilterChain.internalDoFilter（ApplicationFilterChain。 java：291）org.apache.catalina.core.ApplicationFilterChain.doFilter（ApplicationFilterChain.java:206）atg.apache.tomcat.websocket.server.WsFilter.doFilter（WsFilter.java:52）org.apache.catalina .core.ApplicationFilterChain.internalDoFilter（ApplicationFilterChain.java:239）org.apache.catalina.core.Ap plicationFilterChain.doFilter（ApplicationFilterChain.java:206）org.apache.catalina.core.StandardWrapperValve.invoke（StandardWrapperValve.java:219）atg.apache.catalina.core.StandardContextValve.invoke（StandardContextValve.java:106）at org .apache.catalina.authenticator.AuthenticatorBase.invoke（AuthenticatorBase.java:506）org.apache.catalina.core.StandardHostValve.invoke（StandardHostValve.java:142）org.apache.catalina.valves.ErrorReportValve.invoke（ErrorReportValve） .java：79）org.apache.catalina.valves.AbstractAccessLogValve.invoke（AbstractAccessLogValve.java:610）org.apache.catalina.core.StandardEngineValve.invoke（StandardEngineValve.java:88）org.apache.catalina。 conne.CoyoteAdapter.service（CoyoteAdapter.java:537）org.apache.coyote.http11.AbstractHttp11Processor.process（AbstractHttp11Processor.java:1081）at org.apache.coyote.AbstractProtocol $ AbstractConnectionHandler.process（AbstractProtocol.java:658）在org.apache.coyote.http11.Http11NioProtocol $ Http11Connection Handler.process（Http11NioProtocol.java:222）org.apache.tomcat.util.net.NioEndpoint $ SocketProcessor.doRun（NioEndpoint.java:1566）org.apache.tomcat.util.net.NioEndpoint $ SocketProcessor.run（ NioEndpoint.java:1523）java.util.concurrent.ThreadPoolExecutor.runWorker（Unknown Source）at java.util.concurrent.ThreadPoolExecutor $ Worker.run（Unknown Source）at org.apache.tomcat.util.threads.TaskThread $ WrappingRunnable .run（TaskThread.java:61）at java.lang.Thread.run（Unknown Source）

java.lang.ClassCastException：[Ljava.lang.Object; 不能转换为com.sakhnin.classes.MonthlySummary

MonthlySummary.java

public class MonthlySummary {
    @Id
    private String Date;
    private int Cost;
    private String Place;
    private String Start;
    private String End;
    private String Description;
    private int MentorID;

    public MonthlySummary() {
    // TODO Auto-generated constructor stub
    }


    public MonthlySummary(String place, String date, String start, String end,
        String description, int cost, int mentorID) {
    super();
    Place = place;
    Date = date;
    Start = start;
    End = end;
    Description = description;
    Cost = cost;
    MentorID = mentorID;
}

MonthlySummaryIMP.java

 public List<MonthlySummary> getMentorReportsById(int id) {
    List<MonthlySummary> reports=null;
    try{
    session = factory.openSession();
    session.beginTransaction();
    // Fetch all active coupons whose businesses' parent's category is as got in the argument
    SQLQuery query =  session.createSQLQuery("SELECT * FROM MonthlySummary WHERE MentorID="+id );
    reports = query.list();
    closeSession();
    }
    catch(HibernateException e){
        System.err.println(e.getMessage());
    }
    catch(Exception e){
        System.err.println(e.getMessage());
    }
    return reports;

}

jsp文件

<tbody>
  <%
    List<MonthlySummary> m = (List<MonthlySummary>)request.getSession().getAttribute("meetingsReports");

    for(MonthlySummary report : m) {
  %>

  <td>Date<%=report.getDate() %></td>
  <td>Date<%=report.getPlace()%></td>
  <td>Date<%=report.getStart()%></td>
  <td>Date<%=report.getEnd()%></td>
  <td>Date<%=report.getDescription() %></td>
  <td>Date<%=report.getCost()%></td>

  <%
    }
  %>
</tbody>

Answer 1

要避免此类ClassCastException ，您需要将Entity添加到查询对象中。 试试以下 -

SQLQuery query =  session.createSQLQuery("SELECT * FROM MonthlySummary WHERE MentorID="+id );

query.addEntity(MonthlySummary.class);

reports = query.list();
--rest of code

Answer 2

由于您的堆栈跟踪表明它试图转换List of MonthlySummary但实际上它无法理解左手对象来完成此过程。

这种奇怪的，因为如果你没有在第一手设置HTTPSession属性，它应该给你Null Pointer Exception。

你确定你没有使用该键设置任何属性，我的假设是你在该键中设置了一些其他对象。

请使用Sighr提到的技巧 ，这应该为你做出魔力。