Question

我错误的HQL尝试从另一个表访问列。遗憾。 这个问题已经解决了。 我有Object类型的ArrayList。从会话中获取。它存在。我查一下但我t print it it from jsp or java. even I create methods. // with type List I can甚至可以从会话中获取信息。将其更改为ArrayList。

我的目标是打印结果。我选择了一些sql列，我只想输出它们。当然这是对象。我没有错误，那就是问题。只有我类型的现有arraylist对象。

ArrayList <prod> goodlist = (ArrayList <prod>) session.getAttribute("goodlist_s");


for (prod glst : goodlist) {
                 %>
                 <tr>
                     <td><%//=out.println(u.getname())%></td>
                     <td><%=glst.getcatid()%></td>}

我尝试将其转换为String ArrayList。

ArrayList<String> jlistTitles = new ArrayList<String>((ArrayList<String>) session.getAttribute("goodlist_s")); //converted fine

         for(int i = 0; i < goodlist.size(); i++) {
             System.out.println(goodlist.get(i).getprice());
             //print object type
             }
      **Shows nothing**

这是我的功能

@SuppressWarnings("unchecked")
public  static ArrayList<prod> getListOfProds(String catname,String name,Integer pricel, Integer priceh){
    ArrayList<prod> list = new ArrayList<prod>();
    Session session = HibernateUtil.openSession();
    Transaction tx = null;        
    try {
        tx = session.getTransaction();
        tx.begin();
        Query query = session.createQuery("from prod where catname=?");
        query.setString(0, catname);
        //query.setInteger(1, pricel);
        //query.setInteger(2, priceh);
        list = (ArrayList<prod>) query.list(); 

        tx.commit();
    } catch (Exception e) {
        if (tx != null) {
            tx.rollback();
        }
        e.printStackTrace();
    } finally {
        session.close();
    }
    return list;
}

BTW我会发送所有代码的的index.jsp

<%@page import="java.util.List"%>
<%@page import="service.IndexService"%>
<%@page import="java.util.Date"%>

<%@page import="goods.prod"%>
<%@page import="goods.cat"%>
<%@page import ="java.util.ArrayList"%>
<%@page import ="java.util.List"%>

<%@page contentType="text/html" pageEncoding="UTF-8"%>


<!DOCTYPE html>
<html>
<head>
     <meta http-equiv="Content-Type" content="text/html; charprods=UTF-8">
     <link rel="stylesheet" type="text/css" href="css/style.css"/>
     <title>Result Page</title> 
</head>

</head>
<body>
<form action="IndexServlet" method="POST">


<table align="center" cellpadding = "10">
<tr>
<td>Category</td>
<td><input type="text" name="catname" maxlength="30"/>
(max 30 characters a-z and A-Z)
</td>
</tr>
<tr>
<td>Category id</td>
<td><input type="number" name="catid" maxlength="30"/>
(max 30 characters a-z and A-Z)
</td>
</tr>
<tr>
<td>Naimenovanie</td>
<td><input type="text" name="name" maxlength="30"/>
(max 30 characters a-z and A-Z)
</td>
</tr>

<tr>
<td>Price low</td>
<td><input type="number" name="pricel" maxlength="30"/>
(max 30 characters a-z and A-Z)
</td>
</tr>

<tr>
<td>Price high</td>
<td><input type="number" name="priceh" maxlength="100" /></td>
</tr>

<tr>
<td colspan="2" align="center">
<input type="submit" value="Submit">
<input type="reset" value="Reset">
</td>
</tr>
</table>


prodsAttribute
 <%
     prod prod = (prod) session.getAttribute("prod");
 %>     
  <%
     ArrayList <prod> goodlist = (ArrayList <prod>) session.getAttribute("goodlist_s");


 %> 

 <b>You have<% if (null == prod) out.println("No text entered.");%></b>     
   <b>You have<% if (null == goodlist) out.println("goodlist does NOT exists.");%></b>  
  <b>You have<% if (null != goodlist) {
         ArrayList<String> jlistTitles = new ArrayList<String>((ArrayList<String>) session.getAttribute("goodlist_s"));
         if (null == jlistTitles) out.println("convertedStringlist does NOT exists.");  
         if (null != jlistTitles) out.println("convertedStringlist exists. How can I use it?");
         for(int i = 0; i < goodlist.size(); i++) {
             System.out.println(goodlist.get(i).getprice());
             //print object type
             }

      out.println("goodlist exists. How can I use it?");}%></b> 

<br>
  <b><%if (null!=prod) out.println(prod.getid()+ " "+prod.getname()+ " "+prod.getprice());%></b>    
 <br/>   
                 <%
                 if (null!=goodlist)  {
                     for (prod glst : goodlist) {
                 %>
                 <tr>
                     <td><%//=out.println(u.getname())%></td>
                     <td><%=glst.getcatid()%></td>
                     <td><%=glst.getprice()%></td>                   
                     <td><%="hh"%></td>
                 </tr>
                 <%}}%>



</form>
</body>
</html>

Indexservlet.java

package servlet;

import java.io.IOException;
import java.util.ArrayList;
import java.util.List;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import goods.prod;
import service.IndexService;

public class IndexServlet extends HttpServlet {

    private static final long serialVersionUID = -8670416133536111566L;

    public void doPost(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
     response.setContentType("text/html;charprods=UTF-8");
    //Long id = Long.parseLong(request.getParameter("id"));
     String name = request.getParameter("name");
     String catname = request.getParameter("catname");
     Integer pricel = Integer.parseInt(request.getParameter("pricel"));
     Integer priceh = Integer.parseInt(request.getParameter("priceh"));


     prod dot = IndexService.getprodbyparam(catname,name,pricel,priceh);
     List<prod> goodlist = IndexService.getListOfProds(catname,name,pricel,priceh);

     request.getSession().setAttribute("goodlist_s", goodlist);
     request.getSession().setAttribute("prod", dot);        
     response.sendRedirect("index.jsp");

}

}

有功能的索引服务

package service;

import java.sql.DriverManager;
import java.util.ArrayList;
import java.util.List;

import org.hibernate.Criteria;
import org.hibernate.Query;
import org.hibernate.Session;
import org.hibernate.Transaction;



import HibernateUtil.HibernateUtil;
import goods.prod;

public class IndexService {

      public  static prod getprodbyparam(String catname,String name,Integer pricel, Integer priceh) {
            Session session = HibernateUtil.openSession();
            Transaction tx = null;
            prod prod = null;
            try {
                tx = session.getTransaction();
                tx.begin();
                //Query query = session.createQuery("select prod.id from prod as prod inner join cat.id as id where name=?");
                Query query = session.createQuery("from prod where name=? and price between ? and ?");
                query.setString(0, name);
                query.setInteger(1, pricel);
                query.setInteger(2, priceh);
                //query.prodsInteger(3, catid);
                prod = (prod)query.uniqueResult();
                tx.commit();
            } catch (Exception e) {
                if (tx != null) {
                    tx.rollback();
                }
                e.printStackTrace();
            } finally {
                session.close();
            }
            return prod;
        }




    @SuppressWarnings("unchecked")
    public  static ArrayList<prod> getListOfProds(String catname,String name,Integer pricel, Integer priceh){
        ArrayList<prod> list = new ArrayList<prod>();
        Session session = HibernateUtil.openSession();
        Transaction tx = null;        
        try {
            tx = session.getTransaction();
            tx.begin();
            Query query = session.createQuery("from prod where catname=?");
            query.setString(0, catname);
            //query.setInteger(1, pricel);
            //query.setInteger(2, priceh);
            list = (ArrayList<prod>) query.list(); 

            tx.commit();
        } catch (Exception e) {
            if (tx != null) {
                tx.rollback();
            }
            e.printStackTrace();
        } finally {
            session.close();
        }
        return list;
    }


    }

用吸气剂刺激

package goods;

import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.FetchType;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.JoinColumn;
import javax.persistence.JoinColumns;
import javax.persistence.ManyToOne;
import javax.persistence.OneToMany;
import javax.persistence.OneToOne;
import javax.persistence.Table;

import java.io.Serializable;


@Entity
@Table(name = "prod")

public class prod implements Serializable {

    @Id @GeneratedValue 
    @Column(name = "id")
    private Long id;

    private Integer catid;

    private String name;
    private Integer price;


    public prod() {
    }

    public prod(Long id, Integer catid, String name, Integer price) {
        this.id = id;
        this.catid = catid;
        this.name = name ;
        this.price = price;
    }

    public Long getid() {
        return id;
    }

     public void setid(Long id) {
        this.id = id;
    }

    public Integer getcatid() {
        return catid;
    }
    public void setcatid(Integer catid) {
        this.catid = catid;
    }

    public String getname() {
        return name;
    }    
    public void setname(String name) {
        this.name = name;
    }

    public Integer getprice() {
        return price;
    }   
    public void setprice(Integer price) {
        this.price = price;
    }

    }

的web.xml

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/javaee" xmlns:web="http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" id="WebApp_ID" version="2.5">
    <display-name>Improve</display-name>
    <servlet>
        <servlet-name>IndexServlet</servlet-name>
        <servlet-class>servlet.IndexServlet</servlet-class>
    </servlet>
    <servlet-mapping>
        <servlet-name>IndexServlet</servlet-name>
        <url-pattern>/IndexServlet</url-pattern>
    </servlet-mapping>

    <welcome-file-list>
        <welcome-file>index.jsp</welcome-file>
    </welcome-file-list>
</web-app>

Answer 1

您可以尝试下面的代码，看看它是否有效

ArrayList<String> goodlist_s= (ArrayList<String>)session.getAttribute("goodlist_s");


<% 
for(int i = 0; i < goodlist_s.size(); i++) 
{ 
String myString = (String) goodlist_s.get(i); 
} 
%>

hibernate打印来自会话对象arraylist的数据

1 个答案: