Java代码实现 增删查 + 分页——实习第四天

今天项目内容已经开始了，并且已经完成好多基本操作，今天就开始总结今天学习到的内容，和我遇到的问题，以及分析这其中的原因。

内容模块：

1：Java代码实现对数据库的增删查；

2：分页且获取页面信息；

---

这里针对于项目里面的Genre实体，以及对于它的操作进行举例

 package com.music.entity;

 public class Genre {
     private int id;
     private String name;
     private String description;

     public int getId() {
         return id;
     }
     public void setId(int id) {
         this.id = id;
     }
     public String getName() {
         return name;
     }
     public void setName(String name) {
         this.name = name;
     }
     public String getDescription() {
         return description;
     }
     public void setDescription(String description) {
         this.description = description;
     }

 }

Genre.java

逻辑层代码展示：

GenreDao:

 package com.music.Dao;

 import java.util.List;

 import com.music.entity.Genre;

 public interface GenreDao {
     //查询
     public List<Genre> getAll();
     //删除
     public boolean deleteGenre(int id);
     //插入
     public boolean addGenre(Genre g);
     //更新
     public boolean updateGenre(Genre g);
 }

在这个接口里方法的具体实现GenreDaoImpl:

 package com.music.Dao.Impl;

 import java.sql.ResultSet;
 import java.sql.SQLException;
 import java.util.ArrayList;
 import java.util.List;

 import com.music.Dao.GenreDao;
 import com.music.entity.Genre;

 public class GenreDaoImpl extends BaseDao implements GenreDao{

     //保存获取结果
     ArrayList<Genre> genres = new ArrayList<Genre>();
     @Override
     public List<Genre> getAll() {
         try {
             //创建连接
             openConnection();
             String sql = "select * from genre";
             //执行查询，获取结果
             ResultSet resultSet = executeQuery(sql, null);
             //将查询结果转换成对象
             while (resultSet.next()) {
                 Genre g = new Genre();
                 g.setId(resultSet.getInt("id"));
                 g.setName(resultSet.getString("name"));
                 g.setDescription(resultSet.getString("description"));
                 genres.add(g);
             }
         } catch (ClassNotFoundException e) {

             e.printStackTrace();
         } catch (SQLException e) {

             e.printStackTrace();
         }finally{
             closeResourse();
         }
         return genres;
     }

     @Override
     public boolean deleteGenre(int id) {
         boolean result = false;
         try {
             openConnection();
             String sql ="delete from genre where id = ?";
             result = excute(sql, new Object[]{id});
         } catch (ClassNotFoundException e) {

             e.printStackTrace();
         } catch (SQLException e) {

             e.printStackTrace();
         }finally{
             closeResourse();
         }
         return result;
     }

     @Override
     public boolean addGenre(Genre g) {
         boolean result = false;
         try {
             openConnection();
             String sql ="insert into genre value(?,?,?)";
             result =excute(sql, new Object[]{
                     g.getId(),
                     g.getDescription(),
                     g.getName()
             });
         } catch (ClassNotFoundException e) {
             e.printStackTrace();
         } catch (SQLException e) {
             e.printStackTrace();
         }finally{
             closeResourse();
         }
         return result;
     }

     @Override
     public boolean updateGenre(Genre g) {
         boolean result = false;
         try {
             openConnection();
             String sql = "update genre set name = ?, description =? where id=?";
             result = excute(sql, new Object[]{
                     g.getId()
             });
         } catch (ClassNotFoundException e) {

             e.printStackTrace();
         } catch (SQLException e) {

             e.printStackTrace();
         }finally{
             closeResourse();
         }
         return result;

     }

     public static void main(String[] args) {
         GenreDaoImpl genreDaoImpl = new GenreDaoImpl();
         genreDaoImpl.getAll();
         System.out.println(genreDaoImpl);

     }

 }

这里还必须要提出BaseDao:

 package com.music.Dao.Impl;

 import java.sql.Connection;
 import java.sql.DriverManager;
 import java.sql.PreparedStatement;
 import java.sql.ResultSet;
 import java.sql.SQLException;

 public class BaseDao {
     //连接数据库
     private String className = "com.mysql.jdbc.Driver";
     private String dburl = "jdbc:mysql://localhost/ZJJ";
     private String user = "root";
     private String password = "root";
     private Connection connection;
     private PreparedStatement statement;
     private ResultSet resultSet;

     public void openConnection() throws ClassNotFoundException, SQLException{
         //加载驱动
         Class.forName(className);
         //创建连接
         connection = DriverManager.getConnection(dburl,user,password);
     }

     //查询方法
     public ResultSet executeQuery(String sql,Object[] params) throws SQLException{
         statement =connection.prepareStatement(sql);
         //追加参数
         if(params !=null){
             int i=1;
             for (Object object : params) {
                 statement.setObject(i, object);
                 i++;
             }
         }
         resultSet =statement.executeQuery();
         return resultSet;
     }

     //更新
     public boolean excute(String sql,Object[] params) throws SQLException {
         statement =connection.prepareStatement(sql);
         if(params !=null){
             int i=1;
             for (Object object : params) {
                 statement.setObject(i, object);
             }
         }
         return statement.execute();
     }
     //释放资源
     public void closeResourse(){
         try {
             if(resultSet != null){
                 resultSet.close();
             }
             if(statement != null){
                 statement.close();
             }
             if(connection != null){
                 connection.close();
             }

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

 }

这个里面的方法都会获得调用。

今天报了一个错误：

错误的原因是：

这个setObject(i,object)有一个好处就是将所有的对象类型都写成object，这样就可以不用分开写各个类型的方法，比较简便。

---

分页：

接口部分：

 //分页
     public List<Album> getAlbumWithPage(int genreid,int pageNum,int pageSize);

1 public List<Album> getAlbumWithPage(int genreid, int pageNum, int pageSize)

实现部分：

 public List<Album> getAlbumWithPage(int genreid, int pageNum, int pageSize) {
         ArrayList<Album> albums = new ArrayList<Album>();
         //pageNum当前页数
         try {
             openConnection();
             String sql= "select * from album where genreid =? limit ?,?";
             ResultSet resultSet = executeQuery(sql, new Object[]{
                     genreid,
                     (pageNum-1)*pageSize,
                     pageSize
             });
             while (resultSet.next()) {
                 Album al= new Album();
                 al.setId(resultSet.getInt("id"));
                 al.setGenreid(resultSet.getInt("genreid"));
                 al.setArtist(resultSet.getString("artist"));
                 al.setTitle(resultSet.getString("title"));
                 al.setPrice(resultSet.getBigDecimal("price"));
                 al.setStock(resultSet.getInt("stock"));
                 al.setDateReleased(resultSet.getString("dateReleased"));
                 al.setDescription(resultSet.getString("description"));
                 albums.add(al);
             }
         } catch (ClassNotFoundException e) {

             e.printStackTrace();
         } catch (SQLException e) {

             e.printStackTrace();
         }
         return albums;

       

1 public List<Album> getAlbumWithPage(int genreid, int pageNum, int pageSize) {

    return daoImpl.getAlbumWithPage(genreid, pageNum, pageSize);
     }

     @Override
     public int getRowCountWithGenreid(int id) {

         return daoImpl.getAlbumWithGenreid(id).size();
     }

JSP代码部分

 <%@page import="com.music.entity.Album"%>
 <%@page import="com.music.biz.Impl.AlbumBizImpl"%>
 <%@page import="com.music.biz.AlbumBiz"%>
 <%@page import="com.music.Dao.Impl.AlbumDaoImpl"%>
 <%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
 <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
 <%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c" %>

 <html>
   <head>
     <title>欢迎光临 Music Store</title>
     <link type="text/css" rel="Stylesheet" href="style/front.css"/>
     <script type="text/javascript" src="script/jquery-1.4.1.js"></script>
   </head>
   <%
     AlbumBiz albumItem = new AlbumBizImpl();
     String id = request.getParameter("genreId");

     int pageSize =3;
     int pageNum =1;

     if(request.getParameter("page")!=null){
           pageNum =Integer.valueOf(request.getParameter("page"));
       }

     List<Album> albums = albumItem.getAlbumWithPage(Integer.valueOf(id), pageNum, pageSize);

     request.setAttribute("albums", albums);
     request.setAttribute("pageNum", pageNum);

     int rows = albumItem.getRowCountWithGenreid(Integer.valueOf(id));
     int pageCount = (int)Math.ceil((double)rows/pageSize);
    // int pageCount =albumItem.getRowCountWithGenreid(Integer.valueOf(id));
     request.setAttribute("pageCount", pageCount);

     request.setAttribute("genreId", id);

    %>

   <body>
     <div id="wrapper">
             <%@ include file="shared/front_header.jsp" %>
         <div id="content">
             <%@ include file="shared/front_sidebar.jsp" %>
             <div id="main">
                 <h3 id="main-title">唱片列表</h3>
                 <c:forEach var="album" items="${albums}">
                    <table class="albumItem">
                        <tr>
                            <td rowspan="3" class="albumItem-image"><img src="CoverImages/${album.id}.jpg" alt="" /></td>
                            <td colspan="2" class="albumItem-title">
                                <a href="album.jsp?albumId=${album.id}">${album.title}</a>
                            </td>
                        </tr>
                        <tr>
                            <td class="albumItem-artist"><strong>歌手：${album.artist }</strong></td>
                            <td class=".albumItem-price"><strong>定价：${album.price }</strong>￥</td>
                        </tr>
                        <tr>
                            <td colspan="2">
                             ${album.description}
                            </td>
                        </tr>
                    </table>
                 </c:forEach>
                 <hr/>

                    <a href="album_list.jsp?page=1&genreId=${genreId}&title=${title}">第一页</a>
                    <c:if test="${pageNum>1 }">
                     <a href="album_list.jsp?page=${pageNum-1}&genreId=${genreId}&title=${title}">上一页</a>

                   </c:if>
                   <c:if test="${pageNum<pageCount}">
                     <a href="album_list.jsp?page=${pageNum+1}&genreId=${genreId}&title=${title}">下一页</a>
                 </c:if>
                    <a href="album_list.jsp?page=${pageCount}&genreId=${genreId}&title=${title}">最后一页</a>
                     &nbsp;共${pageCount}页，第${pageNum}页。

             </div>
             <div class="clearBoth"></div>
         </div>
         <%@ include file="shared/front_footer.jsp" %>
     </div>
   </body>
 </html>

对于分页，前面的博客有讲述，就不赘述了~

说实话，今天我好累了~就写那么多吧~现在距离下课还有5分钟，我要记会儿单词~