ArrayList的+数据库+的servlet + DAO [英] Arraylist + database + servlet + DAO

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本文介绍了ArrayList的+数据库+的servlet + DAO的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！

问题描述

您好我是新来HAVA，我有在JSP页面中一个ArrayList查看我的记录有问题，
每当我加载网页我得到：
[content.animalBean@1e8614a，content.animalBean@14b52aa，content.animalBean@2026f3，content.animalBean@dd20b6，content.animalBean@18eb00c] 1，它不是数据库记录
这里是我的code：
selectAnimalServlet：

Hello i'm new to hava and i'm having a problem viewing my records from an arraylist in JSP page, whenever i load the page i get: [content.animalBean@1e8614a, content.animalBean@14b52aa, content.animalBean@2026f3, content.animalBean@dd20b6, content.animalBean@18eb00c] 1 which is not the database records here is my code: selectAnimalServlet:

package content;

import java.util.Iterator;
import java.util.List;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class selectAnimalServlet extends HttpServlet {

    public void doGet(HttpServletRequest request, HttpServletResponse response) 
                       throws ServletException, java.io.IOException {

try
{       

    List<animalBean> beans = DAO.selectListAnimal(); 
    request.setAttribute("beans", beans); 
    request.getRequestDispatcher("checkAnimal.jsp").forward(request, response); 


}

catch (Throwable theException)      
{
     System.out.println(theException); 
}
       }
    }

AnimalBean：

AnimalBean:

package content;

public class animalBean {

    private String animalName;
    private String animalDob;
    private String animalGender;
    private String animalSource;
    private String animalBreed;
    private String animalRemark;

    public String getAnimalName() {return animalName;}
    public String getAnimalDob() {return animalDob;}
    public String getAnimalGender() {return animalGender;}
    public String getAnimalSource() {return animalSource;}
    public String getAnimalBreed() {return animalBreed;}
    public String getAnimalRemark() {return animalRemark;}

    public void setAnimalName(String animalName) {this.animalName = animalName;}
    public void setAnimalDob(String animalDob) {this.animalDob = animalDob;}
    public void setAnimalGender(String animalGender) {this.animalGender = animalGender;}
    public void setAnimalSource(String animalSource) {this.animalSource = animalSource;}
    public void setAnimalBreed(String animalBreed) {this.animalBreed = animalBreed;}
    public void setAnimalRemark(String animalRemark) {this.animalRemark = animalRemark;}


}

DAO类：

package content;


import java.sql.*;
import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;


public class DAO    
{
   static Connection currentCon = null;
   static ResultSet rs = null;  



   public static loginAuth login(loginAuth bean) {

      //preparing some objects for connection 
      Statement stmt = null;    

      String username = bean.getUsername();    
      String password = bean.getPassword();   

      String searchQuery =
            "select * from user where username='"
                     + username
                     + "' AND password='"
                     + password
                     + "'";

   // "System.out.println" prints in the console; Normally used to trace the process
   System.out.println("Your user name is " + username);          
   System.out.println("Your password is " + password);
   System.out.println("Query: "+searchQuery);

   try 
   {
      //connect to DB 
      currentCon = dbConnection.getConnection();
      stmt=currentCon.createStatement();
      rs = stmt.executeQuery(searchQuery);          
      boolean more = rs.next();

      // if user does not exist set the isValid variable to false
      if (!more) 
      {
         System.out.println("Sorry, you are not a registered user! Please sign up first");
         bean.setValid(false);
      } 

      //if user exists set the isValid variable to true
      else if (more) 
      {
         String firstName = rs.getString("FirstName");
         String lastName = rs.getString("LastName");

         System.out.println("Welcome " + firstName);
         bean.setfname(firstName);
         bean.setlname(lastName);
         bean.setValid(true);
      }
   } 

   catch (Exception ex) 
   {
      System.out.println("Log In failed: An Exception has occurred! " + ex);
   } 

   //some exception handling
   finally 
   {
      if (rs != null)   {
         try {
            rs.close();
         } catch (Exception e) {}
            rs = null;
         }

      if (stmt != null) {
         try {
            stmt.close();
         } catch (Exception e) {}
            stmt = null;
         }

      if (currentCon != null) {
         try {
            currentCon.close();
         } catch (Exception e) {
         }

         currentCon = null;
      }
   }

return bean;

   }    




   public static List<animalBean> selectListAnimal() throws SQLException {

       Statement stmt = null;
       List<animalBean> beans = new ArrayList<animalBean>(); 
       try { 
           currentCon = dbConnection.getConnection();
           String animalSearchQuery = "select a.aname ,a.dob,  a.gender , a.source, s.sname, a.remark from animal as a , specie as s where a.specie_id = s.specie_id and a.available ='y'";        
           stmt=currentCon.createStatement(); 
           rs = stmt.executeQuery(animalSearchQuery);       

           while (rs.next()) { 
               animalBean bean = new animalBean();
               bean.setAnimalName(rs.getString("aname"));
               bean.setAnimalDob(rs.getString("dob"));
               bean.setAnimalGender(rs.getString("gender"));
               bean.setAnimalSource(rs.getString("source"));
               bean.setAnimalBreed(rs.getString("sname"));
               bean.setAnimalRemark(rs.getString("remark"));
               beans.add(bean);
                 }


       } finally { 
           if (rs != null) try { rs.close(); } catch (SQLException logOrIgnore) {} 
           if (stmt != null) try { stmt.close(); } catch (SQLException logOrIgnore) {} 
           if (currentCon != null) try { currentCon.close(); } catch (SQLException logOrIgnore) {} 
       } 
       return beans; 


       }



   }

和最后一个JSP页面animalCheck.jsp：

and last the JSP page animalCheck.jsp:

<%@ page language="java" 
         contentType="text/html; charset=windows-1256"
         pageEncoding="windows-1256"
         import="content.animalBean"
         import="content.DAO"




   %>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"
"http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=windows-1256">
<title>Animal list</title>
<link rel="stylesheet"
      href="./css/styles.css"
      type="text/css"/>
</head>
<body>
<table class="title">
  <tr><th>Zoo keeper</th></tr>
</table>


<h1>Animal list</h1>
 <center>
 <table width="100 % " id='table1'  border="1" cellspacing="2" cellpadding="2"> 
    <tr class="tab-highlighted-2"> 
        <td class="tab-highlighted-2" width="15"> 
          <div align="left">Name</div> 
        </td> 
        <td class="tab-highlighted-2" width="20"> 
          <div align="left">Age</div> 
        </td>
         <td class="tab-highlighted-2" width="15"> 
          <div align="left">Gender</div> 
        </td>
        <td class="tab-highlighted-2" width="15"> 
          <div align="left">Status</div> 
        </td>    
        <td class="tab-highlighted-2" width="15"> 
          <div align="left">Breed</div> 
        </td>  
        <td class="tab-highlighted-2" width="15"> 
          <div align="left">Remarks</div> 
        </td> 

    </tr> 

    <c:forEach items="${beans}" var="view"> 
        <tr> 
            <td>${view.animalName} </td> 
            <td>${view.animalDob}</td>
            <td>${view.animalGender}</td>
            <td>${view.animalSource}</td>
            <td>${view.animalBreed}</td>
            <td>${view.animalRemark}</td>

        </tr> 
    </c:forEach> 
</table> 

         </center>

</body></html>

我已经struggeling这个，因为2天，我检查很多网站和跟随导游很多，但仍然没有为我工作:(
我AP preciate任何形式的帮助。

I've been struggeling on this since 2 days and i checked many websites and followed many guides but still nothing worked for me :( I appreciate any kind of help

推荐答案

您忘了申报JSTL核心标签库。以下内容添加到你的JSP的顶部：

You forgot to declare the JSTL core taglib. Add the following to top of your JSP:

<%@taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>

参见：


  • 我们JSTL维基页面 - 包含有关如何安装和使用JSTL信息

  • 使用MVC和JDBC
    • JSP
  • How避免Java的code在JSP的文件？

    • See also:

    • Our JSTL wiki page - contains information about how to install and use JSTL
    • JSP using MVC and JDBC
    • How to avoid Java Code in JSP-Files?

      • 无关以具体的问题，也有你的code等几个问题：

      Unrelated to the concrete problem, there are several other problems in your code:


      • 您永远不应该声明DB资源静态。这不是线程并且容易发生资源泄漏。声明他们非常相同的方法块内为你执行的SQL查询。

      • 您在 SQL注入孔登录（）方法。 使用 preparedStatement 。

      • 您不需要使用 @Page进口在你的JSP，如果你不使用任何的小脚本的

      • 类名是应该下手大写

      • You should never declare DB resources as static. This is not threadsafe and is prone to resource leaking. Declare them inside the very same method block as you're executing the SQL query.
      • You have a SQL injection hole in login() method. Use PreparedStatement.
      • You don't need to use @page import in your JSP if you aren't using any scriptlets.
      • Classnames are supposed to start with uppercase.

      这篇关于ArrayList的+数据库+的servlet + DAO的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！

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