session取值为空

Question

登录成功 ，登录数据已经存入session ，经验证取证正常。但是向数据库添加数据的过程中 session取值竟然为空。费解！！1.登录servlet  登录成功并转向，session成功写入。package ser;import impl.AccountImpl;
import it.shopping.dao.IAccount;
import it.shopping.pojo.Account;import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;public class AccountSer extends HttpServlet
{
   
 
   private IAccount accountImpl = new AccountImpl();
   
   private static final long serialVersionUID = -3708568559174453120L;
   
   public AccountSer()
   {
   super();
   }
 
public void destroy()
{
super.destroy(); // Just puts "destroy" string in log
// Put your code here
}
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException
{ this.doPost(request, response);
}
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException
{ 

String status = request.getParameter("status");
if(status.equals("login"))
{

Account account = new Account();
account.setAlogin(request.getParameter("alogin"));
account.setApass(request.getParameter("apass"));
 account =accountImpl.queryAccount(account);

if(account == null)
{
request.setAttribute("error", "登录失败");
request.getRequestDispatcher("/alogin.jsp").forward(request, response);
// response.sendRedirect("alogin.jsp");
}

{

          request.getSession().setAttribute("account", account);
         // response.sendRedirect("/t31/admin/index.jsp");
         // 重定向和请求装啊session值都不会失效！
           request.getRequestDispatcher("/admin/index.jsp").forward(request, response);
          

}
}
}

 
public void init() throws ServletException
{
// Put your code here

}}2.跳转至index.jsp成功，然后添加数据成功，跳转至servlet 即CategorySer.java成功
但是在category.setAccount((Account) req.getSession().getAttribute("account"));
session  取值竟然为空！！求解释！！package ser;import impl.CategoryImpl;
import it.shopping.dao.ICategory;
import it.shopping.pojo.Account;
import it.shopping.pojo.Category;import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;public class CategorySer extends HttpServlet
{
private ICategory categoryImpl = new CategoryImpl();

public void destroy()
{

super.destroy();

}@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp)
throws ServletException, IOException
{
this.doPost(req,resp);
}@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp)
throws ServletException, IOException
{

String status = req.getParameter("status");

 
if(status.equals("savaCategory"));
{
 
Category category = new Category();
category.setCtype(req.getParameter("ctype"));

category.setChot(Boolean.parseBoolean(req.getParameter("chot")));
category.setAccount((Account) req.getSession().getAttribute("account"));

System.out.println(category.getAccount());
categoryImpl.queryCategory(category);



resp.sendRedirect("/t31/admin/main.jsp");
}





}

public void init() throws ServletException
{


}
}———————————————————————————————————————————————————————ＰＳ：accountpackage it.shopping.pojo;public class Account
{ private int aid;
private String alogin;
private String apass;
public int getAid()
{
return aid;
}
public void setAid(int aid)
{
this.aid = aid;
}
public String getAlogin()
{
return alogin;
}
public void setAlogin(String alogin)
{
this.alogin = alogin;
}
public String getApass()
{
return apass;
}
public void setApass(String apass)
{
this.apass = apass;
}



}
Category.java
package it.shopping.pojo;public class Category
{ private int cid; 
private String ctype;
    private Boolean chot;
    private Account account;
public int getCid()
{
return cid;
}
public void setCid(int cid)
{
this.cid = cid;
}
public String getCtype()
{
return ctype;
}
public void setCtype(String ctype)
{
this.ctype = ctype;
}
public Boolean getChot()
{
return chot;
}
public void setChot(Boolean chot)
{
this.chot = chot;
}
public Account getAccount()
{
return account;
}
public void setAccount(Account account)
{
this.account = account;
}
    
}
CategoryImp.java
package impl;import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;import utils.JdbcUtils;import it.shopping.dao.ICategory;
import it.shopping.pojo.Category;public class CategoryImpl implements ICategory{  @Override
public Category queryCategory(Category category) 
{
     
 Connection conn = null;
 PreparedStatement pre = null;
 String sql =" INSERT INTO  category {?,?,?}";
 ResultSet rs =  null;
 
     try
{   
      
      System.out.println("hello3.0");
     conn = JdbcUtils.getConnection();
pre = conn.prepareStatement(sql);
System.out.println("hello4.0");
System.out.println(category.getAccount().getAid());
pre.setInt(1,category.getAccount().getAid());

pre.setString(2, category.getCtype());
pre.setBoolean(3,category.getChot());
System.out.println("hello6.0");
pre.executeQuery();



} catch (SQLException e)
{
// TODO Auto-generated catch block
e.printStackTrace();
}finally
{

JdbcUtils.free(rs, pre, conn);
}
    
 

return category;


}}

Answer 1

你的代码：
 if(account == null)
        {
            request.setAttribute("error", "登录失败");
            request.getRequestDispatcher("/alogin.jsp").forward(request, response);
        //    response.sendRedirect("alogin.jsp");
        }
        
        {
            
          request.getSession().setAttribute("account", account);
         // response.sendRedirect("/t31/admin/index.jsp");
         // 重定向和请求装啊session值都不会失效！
           request.getRequestDispatcher("/admin/index.jsp").forward(request, response);
          
            
        }
中间是漏了else么？

Answer 2

是的 !谢谢你的指点！
但是现在出现了一个问题：java.sql.SQLException: Can not issue data manipulation statements with executeQuery().

Answer 3

java.sql.SQLException: Can not issue data manipulation statements with executeQuery().
at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:1074)
at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:988)
at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:974)
at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:919)
at com.mysql.jdbc.StatementImpl.checkForDml(StatementImpl.java:497)
at com.mysql.jdbc.PreparedStatement.executeQuery(PreparedStatement.java:2223)
at impl.CategoryImpl.queryCategory(CategoryImpl.java:39)
at ser.CategorySer.doPost(CategorySer.java:58)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:641)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:722)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:305)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)
at it.shopping.filter.EnCodingFilter.doFilter(EnCodingFilter.java:29)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:243)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:225)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:169)
at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:472)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:168)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:98)
at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:927)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:118)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:407)
at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:999)
at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:565)
at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:309)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1110)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:603)
at java.lang.Thread.run(Thread.java:722)

Answer 4

StatementImpl.java:497行的sql语句有问题，发出来

Answer 5

这个错误的意思是：你企图用 executeQuery() 去执行 INSERT、DELETE、UPDATE 之类的语句而不是 SELECT所以是错误的，请改用 execute()

Answer 6

有啥无法找到的，我都提示的这么明显，就是这句话：
            pre.setString(2, category.getCtype());
            pre.setBoolean(3,category.getChot());
            System.out.println("hello6.0");
            pre.executeQuery();你执行的SQL是： String sql ="INSERT INTO category {?,?,?}"; 显然不是SELECT语句，不能用 executeQuery

Answer 7

问个问题哦，Servlet init方法中能够获取服务器IP、端口等信息？

Answer 8

String sql ="INSERT INTO category {?,?,?}"; 这条sql文没有values也能正常执行吗？如果真好用那就out了，我学习了。

Answer 9

谢谢你 这个问题 已已经解决！！是我Out了 才进来！！

Answer 10

这个有点麻烦，因为init方法中，还没有request；所以要用中间件提供的JMX来查询。

Answer 11

在你发的另一个帖子里面回复你了：
  http://topic.csdn.net/u/20120829/12/ece1799a-37fb-46a2-abf0-e98568a6102e.html