jdbc学习总结3------javab

 1.测试类的内容：

在包：com.hanchao.test中

package com.hanchao.test; 
 
import com.hanchao.dao.UserDao; 
import com.hanchao.entity.User; 
 
 
public class Test { 
 
     
 
    public static void main(String[] args) { 
         
         
 
     
         
 
         
         
//      UserDao userDao = new UserDao(); 
//      userDao.delete(21); 
         
         
        UserDao userDao = new UserDao(); 
        userDao.retrieve(22); 
         
    } 
     
} 

2.实体类的写法：com.hanchao.entity

package com.hanchao.entity; 
 
public class User { 
 
     
     
    private int id; 
    private String username; 
    private String address; 
     
    //下面是setter...getter.. 
    public int getId() { 
        return id; 
    } 
    public void setId(int id) { 
        this.id = id; 
    } 
    public String getUsername() { 
        return username; 
    } 
    public void setUsername(String username) { 
        this.username = username; 
    } 
    public String getAddress() { 
        return address; 
    } 
    public void setAddress(String address) { 
        this.address = address; 
    } 
     
     
} 

3.dao的写法：com.hanchao.dao

package com.hanchao.dao; 
 
import java.sql.Connection; 
import java.sql.DriverManager; 
import java.sql.PreparedStatement; 
import java.sql.ResultSet; 
import java.sql.SQLException; 
 
import com.hanchao.entity.User; 
 
 
public class UserDao { 
 
     
     
     
    public int insert(User user) { 
        Connection con = null; 
        PreparedStatement sta = null; 
        int rows = 0; 
         
        try { 
             
            Class.forName("com.mysql.jdbc.Driver"); 
            con = DriverManager.getConnection("jdbc:mysql://127.0.0.1:3306/mydb","root","root"); 
             
            String sql = "insert into t_user(username,address) value(?,?)"; 
            sta = con.prepareStatement(sql); 
            sta.setString(1, user.getUsername()); 
            sta.setString(2, user.getAddress()); 
             
            rows = sta.executeUpdate(); 
            if(rows > 0) { 
                System.out.println("operate successfully!!"); 
            } 
             
        } catch (ClassNotFoundException e) { 
            e.printStackTrace(); 
        } catch (SQLException e) { 
            e.printStackTrace(); 
        } finally { 
            if(sta != null) { 
                try { 
                    sta.close(); 
                } catch (SQLException e) { 
                    e.printStackTrace(); 
                } finally { 
                    if(con != null) { 
                        try { 
                            con.close(); 
                        } catch (SQLException e) { 
                            e.printStackTrace(); 
                        } 
                    } 
                } 
            } 
        } 
        return rows; 
    } 
     
     
    public int update(User user) { 
        Connection con = null; 
        PreparedStatement sta = null; 
        int rows = 0; 
         
        try { 
            Class.forName("com.mysql.jdbc.Driver"); 
            con = DriverManager.getConnection("jdbc:mysql://127.0.0.1:3306/mydb","root","root"); 
             
            String sql = "update t_user set address=?,username=? where id=?"; 
            sta = con.prepareStatement(sql); 
            sta.setString(1, user.getAddress()); 
            sta.setString(2, user.getUsername()); 
            sta.setInt(3, user.getId()); 
             
            rows = sta.executeUpdate(); 
            if(rows > 0) { 
                System.out.println("ok"); 
            } 
        } catch (ClassNotFoundException e) { 
            e.printStackTrace(); 
        } catch (SQLException e) { 
            e.printStackTrace(); 
        } finally { 
            if(sta != null) { 
                try { 
                    sta.close(); 
                } catch (SQLException e) { 
                    e.printStackTrace(); 
                } finally { 
                    if(con != null) { 
                        try { 
                            con.close(); 
                        } catch (SQLException e) { 
                            e.printStackTrace(); 
                        } 
                    } 
                } 
            } 
        } 
        return rows; 
    } 
     
     
    public int delete(int id) { 
        Connection con = null; 
        PreparedStatement sta = null; 
        int rows = 0; 
         
        try { 
            Class.forName("com.mysql.jdbc.Driver"); 
            con = DriverManager.getConnection("jdbc:mysql://127.0.0.1:3306/mydb","root","root"); 
             
            String sql = "delete from t_user where id=?"; 
            sta = con.prepareStatement(sql); 
            sta.setInt(1, id); 
             
            rows = sta.executeUpdate(); 
            if(rows > 0) { 
                System.out.println("ok,ok,ok"); 
            } 
             
        } catch (ClassNotFoundException e) { 
            e.printStackTrace(); 
        } catch (SQLException e) { 
            e.printStackTrace(); 
        } finally { 
            if(sta != null) { 
                try { 
                    sta.close(); 
                } catch (SQLException e) { 
                    e.printStackTrace(); 
                } finally { 
                    if(con != null) { 
                        try { 
                            con.close(); 
                        } catch (SQLException e) { 
                            e.printStackTrace(); 
                        } 
                    } 
                } 
            } 
        } 
        return rows; 
    } 
     
     
     
    public void retrieve(int id) { 
        Connection con = null; 
        PreparedStatement sta = null; 
        ResultSet rs = null; 
         
        try { 
            Class.forName("com.mysql.jdbc.Driver"); 
            con = DriverManager.getConnection("jdbc:mysql://127.0.0.1:3306/mydb","root","root"); 
             
            String sql = "select id,username,address from t_user where id=?"; 
            sta = con.prepareStatement(sql); 
            sta.setInt(1, id); 
             
            rs = sta.executeQuery(); 
            if(rs.next()) { 
                int idd = rs.getInt("id"); 
                String username = rs.getString("username"); 
                String adrress = rs.getString("address"); 
                System.out.println(idd+"\t"+username+"\t"+adrress); 
            } 
             
        } catch (ClassNotFoundException e) { 
            e.printStackTrace(); 
        } catch (SQLException e) { 
            e.printStackTrace(); 
        } finally { 
            if(rs != null) { 
                try { 
                    rs.close(); 
                } catch (SQLException e) { 
                    e.printStackTrace(); 
                } finally { 
                    if(sta != null) { 
                        try { 
                            sta.close(); 
                        } catch (SQLException e) { 
                            e.printStackTrace(); 
                        } finally { 
                            if(con != null) { 
                                try { 
                                    con.close(); 
                                } catch (SQLException e) { 
                                    e.printStackTrace(); 
                                } 
                            } 
                        } 
                    } 
                } 
            } 
        } 
    } 
     
} 

 看dao中的内容，我们发现几个方法中的代码有很多重复的！！所以在下一篇文章中，我们要对代码进行优化！

我把前三篇文章的例子，包括数据库，放在一个压缩包里！名称为：jdbc学习例子.rar。

需要的同学可以去下载！！