java mysql 简单操作

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package javatest;
import java.sql.*;
public class DBconn
{
    // 驱动程序名
  final  String driver = "com.mysql.jdbc.Driver";
 
    // URL指向要访问的数据库名test
  final  String url = "jdbc:mysql://127.0.0.1:3306/udp";
 
    // MySQL配置时的用户名
  final  String user = "root";
 
    // MySQL配置时的密码
  final    String password = "root";
    public    Connection conn =null;
    public   Statement statement=null;
    public  DBconn()
    {
        try {
         // 加载驱动程序
         Class.forName(driver);    
         // 连续数据库
         conn = DriverManager.getConnection(url, user, password);
         statement = conn.createStatement();      
        // if(!conn.isClosed())
         // System.out.println("Succeeded connecting to the Database!");
        } catch(Exception e) {
        }
         
       
    }
 
     
    public void DBcolse()
    {
        try
        {
             
            this.conn.close();
 
        } catch(Exception e)
        
             e.printStackTrace(); 
             System.out.println("数据库关闭失败!");
        }
 
    }
 
 
}
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DBconn db1=new DBconn();
            ResultSet rs =null;
            try{  
                System.out.println("用户请求注册");      
               out.println("please input name");  
            user_name =in.readLine().trim();
            out.println("please input password"); 
            user_password =in.readLine().trim();
            }catch (Exception e)
            {
                System.out.println(e);
            }         
            try
            {
                String sql= "select * from user where name=‘"+user_name+"‘";
                
                rs = db1.statement.executeQuery(sql);
                 
               if(rs.next())
               {
                   System.out.println(user_name+"已经注册");  
                   out.println(user_name+"已经注册");
                    
               }
               else
               {
               String sql_insert= "insert into user(name,password) values( ‘"+ user_name+"‘ , ‘"+user_password+"‘ )";
               System.out.println( db1.statement.executeUpdate(sql_insert));
               System.out.println("注册成功,成功添加了"+user_name+user_password);
               out.println("注册成功,成功添加了"+user_name+user_password);
               }
                     
           }
            catch (Exception e)
            {
                System.out.println(e);
            

更新数据 

 String sql= "update unit set "+field_id+" =‘"+value+"‘ where device_id="+device_id+" and index_in_device="+unit_id+"";
      out.println(sql);
     
      DBconn db1=new DBconn();
      int rs;
    
     rs = db1.statement.executeUpdate(sql);   
     System.out.println("updata number="+rs);

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