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;
    }
    
}

 

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~