java.lang.ClassCastException：[Ljava.lang.Object;以及如何转换类

问题描述 投票：2回答：1

我的DAO是

public class bookRequestStatusDAO {

    public static  List<Book> getbookRequest()
    {

           Session session=null;
           try
           {
                 List booklist=new ArrayList();

            session = HibernateUtil.getSession();
            System.out.println(" Session :: "+session);
            Query query=session.createSQLQuery("{call SP_bookRequestTable()}");
            booklist=query.list();
            System.out.println("in dao getrequest----"+booklist.size());
            if(booklist!=null)
            return booklist;
            else
                return new ArrayList();
           }
           catch(Exception e)
           {
               System.out.println("Exception in BookREqueststatus::"+e);
               return  null;
           }
           finally
           {
               session.close();

           }

    }

我的Struts Action Class是

public ActionForward execute(ActionMapping mapping, ActionForm  form,
            HttpServletRequest request, HttpServletResponse response)
            throws Exception {
          System.out.println(" exce -----");
        BookrequeststatusForm bookrequeststatusForm=(BookrequeststatusForm)form;
        List<Book> convertlist=new ArrayList<Book>();
           convertlist=bookRequestStatusDAO.getbookRequest();


         System.out.println("list in Action::" +convertlist.size() );
          request.setAttribute("bookDeatils",convertlist );
        System.out.print("request in Action::"+request.getAttribute("bookDeatils"));
        return mapping.findForward(Constants.ACTION_FORWARD_SUCCESS);

    }
}

在我的jsp中

<link rel="stylesheet" href="/REC_BookBank/css/bookRequestStatus.css">
<% 
   List<Book>list=new ArrayList<Book>();
    if(request.getAttribute("bookDeatils")!=null)
    {

        list = (ArrayList)request.getAttribute("bookDeatils");
            System.out.println("inside loop List --- "+list.size());
            for(Book book : list)
                {
                out.println("<tr><td>"+book.getId()+"</td></tr>");
            }
               }
    System.out.println(" List --- "+list.size());
%>

我的Book.java

import java.io.Serializable;

/**
 *
 * @author Administrator
 */
public class Book implements Serializable {
 private String id;
 private String subject;
 private String title;
 private String author;
 private String publication;
 private String edition;
 private String status;
 private String mode;

    public String getAuthor() {
        return author;
    }

    public void setAuthor(String author) {
        this.author = author;
    }

    public String getEdition() {
        return edition;
    }

    public void setEdition(String edition) {
        this.edition = edition;
    }

    public String getId() {
        return id;
    }

    public void setId(String id) {
        this.id = id;
    }

    public String getMode() {
        return mode;
    }

    public void setMode(String mode) {
        this.mode = mode;
    }

    public String getPublication() {
        return publication;
    }

    public void setPublication(String publication) {
        this.publication = publication;
    }

    public String getStatus() {
        return status;
    }

    public void setStatus(String status) {
        this.status = status;
    }

    public String getSubject() {
        return subject;
    }

    public void setSubject(String subject) {
        this.subject = subject;
    }

    public String getTitle() {
        return title;
    }

    public void setTitle(String title) {
        this.title = title;
    }

}

在tomcat领事

 exce -----
 Session :: SessionImpl(PersistenceContext[entityKeys=[],collectionKeys=[]];ActionQueue[insertions=[] updates=[] deletions=[] collectionCreations=[] collectionRemovals=[] collectionUpdates=[]])
Hibernate: {call SP_bookRequestTable()}
in dao getrequest----1
list in Action::1
request in Action::[[Ljava.lang.Object;@14ef239]inside loop List --- 1

例外HTTP状态500 -

类型异常报告

信息

description服务器遇到内部错误（），导致无法完成此请求。

例外

org.apache.jasper.JasperException: java.lang.ClassCastException: [Ljava.lang.Object; cannot be cast to com.rec.bookbank.persitencejavafile.Book
    org.apache.jasper.servlet.JspServletWrapper.handleJspException(JspServletWrapper.java:541)
    org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:435)
    org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:320)
    org.apache.jasper.servlet.JspServlet.service(JspServlet.java:266)
    javax.servlet.http.HttpServlet.service(HttpServlet.java:803)
    org.netbeans.modules.web.monitor.server.MonitorFilter.doFilter(MonitorFilter.java:390)
    org.apache.struts.action.RequestProcessor.doForward(RequestProcessor.java:1085)
    org.apache.struts.tiles.TilesRequestProcessor.doForward(TilesRequestProcessor.java:263)
    org.apache.struts.action.RequestProcessor.processForwardConfig(RequestProcessor.java:398)
    org.apache.struts.tiles.TilesRequestProcessor.processForwardConfig(TilesRequestProcessor.java:318)
    org.apache.struts.action.RequestProcessor.process(RequestProcessor.java:241)
    org.apache.struts.action.ActionServlet.process(ActionServlet.java:1196)
    org.apache.struts.action.ActionServlet.doGet(ActionServlet.java:414)
    javax.servlet.http.HttpServlet.service(HttpServlet.java:690)
    javax.servlet.http.HttpServlet.service(HttpServlet.java:803)
    org.netbeans.modules.web.monitor.server.MonitorFilter.doFilter(MonitorFilter.java:390)


root cause 

java.lang.ClassCastException: [Ljava.lang.Object; cannot be cast to com.rec.bookbank.persitencejavafile.Book
    org.apache.jsp.jsp.bookRequestStatus_jsp._jspService(bookRequestStatus_jsp.java:82)
    org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70)
    javax.servlet.http.HttpServlet.service(HttpServlet.java:803)
    org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:393)
    org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:320)
    org.apache.jasper.servlet.JspServlet.service(JspServlet.java:266)
    javax.servlet.http.HttpServlet.service(HttpServlet.java:803)
    org.netbeans.modules.web.monitor.server.MonitorFilter.doFilter(MonitorFilter.java:390)
    org.apache.struts.action.RequestProcessor.doForward(RequestProcessor.java:1085)
    org.apache.struts.tiles.TilesRequestProcessor.doForward(TilesRequestProcessor.java:263)
    org.apache.struts.action.RequestProcessor.processForwardConfig(RequestProcessor.java:398)
    org.apache.struts.tiles.TilesRequestProcessor.processForwardConfig(TilesRequestProcessor.java:318)
    org.apache.struts.action.RequestProcessor.process(RequestProcessor.java:241)
    org.apache.struts.action.ActionServlet.process(ActionServlet.java:1196)
    org.apache.struts.action.ActionServlet.doGet(ActionServlet.java:414)
    javax.servlet.http.HttpServlet.service(HttpServlet.java:690)
    javax.servlet.http.HttpServlet.service(HttpServlet.java:803)
    org.netbeans.modules.web.monitor.server.MonitorFilter.doFilter(MonitorFilter.java:390)


note The full stack trace of the root cause is available in the Apache Tomcat/6.0.14 logs.

我需要在这里打印值，但它显示了异常ClassCastException。

java jsp struts
1个回答
0
投票

你得到异常的原因是因为对存储过程的调用返回了一个值不能直接转换为类的值数组。你可以做两件事之一来得到一本书而不是列表宾语[]。

  • 您可以在.hbm.xml文件中映射该过程并调用它。 （qazxsw poi）
  • 您可以使用RowMapper类实例来映射行。 （这是example提供的东西）。

我个人更喜欢映射程序，它更优雅。

迭代的例子：

spring
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