java - 在使用 hibernate 和 struts 检索数据时，控制台中只会打印对象的地址

Question

持久类:

package com.sheeba.joshua;
import javax.persistence.*;

@Entity
@Table(name="DB_LEAVE")
public class DB_LEAVE {

     public String bank_id;
        public String emp_name;
        public String leaves;
        
        @Id
        @Column(name="BANK_ID")
        public String getBank_id() {
            return bank_id;
        }
        public void setBank_id(String bank_id) {
            this.bank_id = bank_id;
        }
         @Column(name="EMP_NAME")
        public String getEmp_name() {
            return emp_name;
        }
        public void setEmp_name(String emp_name) {
            this.emp_name = emp_name;
        }
         @Column(name="LEAVES_APPLIED")
        public String getLeaves() {
            return leaves;
        }
        public void setLeaves(String leaves) {
            this.leaves = leaves;
        }
        
        @Override
        public String toString() {
            return "DB_LEAVE [bank_id=" + bank_id + ", emp_name=" + emp_name + ", leaves=" + leaves + "]";
        }
        
}

这是我的 DAO 类:

    package com.sheeba.joshua;
import com.sheeba.joshua.*;

import java.io.Serializable;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Iterator;
import java.util.List;

import org.hibernate.Session;
import org.hibernate.Transaction;

import com.googlecode.s2hibernate.struts2.plugin.annotations.SessionTarget;
import com.googlecode.s2hibernate.struts2.plugin.annotations.TransactionTarget;

public class leaveDAO {
    DB_LEAVE modobj = new DB_LEAVE();
    leaveAction act=new leaveAction();
   List<DB_LEAVE> mylist;

    @SessionTarget
    Session session;

    @TransactionTarget
    Transaction t;

    public void saveDetails(DB_LEAVE modobj){
        System.out.println("inside DAO , before query");
        mylist = new ArrayList<DB_LEAVE>();
     
        System.out.println("name" + modobj.getBank_id());
        try {
        session.save(modobj);
        System.out.println("before retrieving" +session.createQuery("from DB_LEAVE").list());
       List mylist = session.createQuery("from DB_LEAVE").list();
       for (Iterator iterator = 
               mylist.iterator(); iterator.hasNext();){
           modobj = (DB_LEAVE) iterator.next(); }
       System.out.println("before setting to action class list" +mylist);
      
        }
        
   catch(Exception e)
   {e.printStackTrace();}

        System.out.println("inside DAO , after query");
       
    }

这是我的服务类:

    package com.sheeba.joshua;

import java.util.ArrayList;
import java.util.List;

import org.apache.struts2.convention.annotation.InterceptorRef;
import org.apache.struts2.convention.annotation.ParentPackage;

import com.opensymphony.xwork2.ActionSupport;
import com.opensymphony.xwork2.ModelDriven;


@ParentPackage("hibernate-default")
@InterceptorRef("basicStackHibernate")
public class leaveService extends ActionSupport implements ModelDriven<DB_LEAVE> {
    private static final long serialVersionUID = -6659925652584240539L;
    leaveDAO daoobj = new leaveDAO();

    DB_LEAVE moddriven = new DB_LEAVE();
    public List<DB_LEAVE> myList = new ArrayList<DB_LEAVE>();

    public List<DB_LEAVE> getMyList() {
        return myList;
    }

    public void setMyList(List<DB_LEAVE> myList) {
        this.myList = myList;
    }
    

    public String test(){
        return"success";
    }

    public String saveDetService() {
        System.out.println("service entry point");
       daoobj.saveDetails(moddriven); 
        return SUCCESS;
    }

    @Override
    public DB_LEAVE getModel() {
        return moddriven;
    }
    
    public DB_LEAVE getDb_LEAVE(){
        return moddriven;
    }
    
    public void setDB_LEAVE(DB_LEAVE moddriven) {
    
        this.moddriven = moddriven;
   }

   /* public String retrieveData() {
        System.out.println("entry point retrieve data");
        daoobj.retrieveFromDAO();
        System.out.println( daoobj.retrieveFromDAO().toString());
        System.out.println("after retrieving ");
        return"SUCCESS";
    }*/
}

JSP

<%@ page language="java" contentType="text/html; charset=ISO-8859-1"
    pageEncoding="ISO-8859-1"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<%@ taglib prefix="s" uri="/struts-tags"%>

<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
<title>LEAVE MANAGEMENT</title>
<h1>DATA SAVED SUCCESSFULLY!! CHECK THE DATABASE...........</h1>
</head>
<body>

<table border="1">
<tr>
    <th>BANK ID</th>
    <th>EMPNAMEE</th>
    <th>LEAVES</th>

</tr>
<s:iterator value="mylist">
    <tr>
        <td><s:property value="bank_id"/></td>
        <td><s:property value="emp_name"/></td>
        <td><s:property value="leaves"/></td>

    </tr>   
</s:iterator>
</table>

它不在 JSP 中打印。早些时候我得到了对象的引用值。但是现在我按照 sanjeev 的建议在控制台中得到了值。它运作良好。然而，在 JSP 中，数据库中的所有值都没有迭代。请帮忙

Answer 1

您在控制台中得到的不是地址，而是引用。当您调用 System.out.println 并将对象传递给它时，Java 不知道如何表示该对象。因此，默认情况下，它会调用对象的 toString() 方法。如果你没有指定你自己的实现，默认的，从 Object 类继承，打印对象的引用。

因此，如果您想要对象的自定义表示，只需覆盖该方法即可。

示例:

 public class DB_LEAVE{

   //your fields and methods
   ...

   /**
   * Returns a String that is a representation of the current object.
   **/
   @Override
   public String toString(){
     return "DB_LEAVE #" + this.id;
   }

}