关于mysql，sqlserverl，与oracle数据库连接总结

首先准备工具类，其中需要修改的地方分别做标注

代码一sqlserver为例，不同数据库只需修改我所标记的第一处和第二处

mysql     第一处应为：com.mysql.jdbc.Driver   第二处url 为：jdbc:mysql://127.0.0.1:3306/javaweb    //3306位端口，javaweb为数据库名

Oracle   第一处应为：oracle.jdbc.OracleDriver  第二处url 为：jdbc:oracle:thin:@localhost:1522:orcl   //1522为端口，orcl为数据库名

sql语句因数据库不同略有差异，但都大同小异。

package Util;

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

public class DBUtil {
    public  static  Connection getConnection(){
        try {
            Class.forName("com.microsoft.sqlserver.jdbc.SQLServerDriver").newInstance();   //1.此处根据数据库修改
        } catch (InstantiationException | IllegalAccessException | ClassNotFoundException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        String user = "sa";  　　　　　　 //用户名
        String password = "123456";   //密码
        String url = "jdbc:sqlserver://127.0.0.1:1433;DatabaseName=keji";  //2.数据库名
        Connection connection = null;
        try {
            //2 �������Ӷ���connection
             connection = DriverManager.getConnection(url,user,password);
        } catch (SQLException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        return connection;
        
    }
    public static void close(Connection connection ) {
        try {
            if (connection != null) {
                connection.close();
            }
            
        } catch (SQLException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }
    public static void close(PreparedStatement preparedStatement ) {
        try {
            if (preparedStatement != null) {
                preparedStatement.close();
            }
            
        } catch (SQLException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }
    public static void close(ResultSet resultSet ) {
        try {
            if (resultSet != null) {
                resultSet.close();
            }
            
        } catch (SQLException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }
    

}

对数据库操作代码

简单的插入

public void add (User user){
        Connection connection=DBUtil.getConnection();
        String sql = "select count(*) from t_user where username = ?";
        PreparedStatement preparedStatement = null;
        ResultSet resultSet = null;
        try {
            preparedStatement = connection.prepareStatement(sql);
            preparedStatement.setString(1, user.getUsername());
            resultSet = preparedStatement.executeQuery();
            while(resultSet.next()) {
                if (resultSet.getInt(1) > 0) {
                    throw new UserException("用户名存在") ;
                }
            }
            
            sql = "insert into t_user(username,password) values (?,?)";
            preparedStatement = connection.prepareStatement(sql);
            preparedStatement.setString(1, user.getUsername());
            preparedStatement.setString(2, user.getPassword());
            preparedStatement.executeUpdate();    
        } catch (SQLException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        finally{
            DBUtil.close(resultSet);
            DBUtil.close(preparedStatement);
            DBUtil.close(connection);
        }
    }

删除

    public void delete(String username) {
        // TODO Auto-generated method stub
        Connection connection = DBUtil.getConnection();
        String sql = "delete from t_user where username = ?";
        PreparedStatement preparedStatement = null;
        
        try {
            preparedStatement = connection.prepareStatement(sql);
            preparedStatement.setString(1, username);
            preparedStatement.executeUpdate();
        } catch (SQLException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }finally {
            DBUtil.close(preparedStatement);
            DBUtil.close(connection);
        }
        
    }

修改

    public void update(User user) {
        // TODO Auto-generated method stub
        Connection connection = DBUtil.getConnection();
        //׼��sql���
        String sql = "update t_user set password = ? where username = ?";
        //������䴫�����
        PreparedStatement preparedStatement = null;
        try {
            preparedStatement = connection.prepareStatement(sql);
            preparedStatement.setString(1, user.getPassword());
            preparedStatement.setString(2, user.getUsername());
            preparedStatement.executeUpdate();
        } catch (SQLException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }finally {
            DBUtil.close(preparedStatement);
            DBUtil.close(connection);
        }
        
        
    }

查询

    public User load(String username) {
        // TODO Auto-generated method stub
        Connection connection = DBUtil.getConnection();
        //׼��sql���
        String sql = "select * from t_user  where username = ?";
        //������䴫�����
        PreparedStatement preparedStatement = null;
        ResultSet resultSet = null;
        User user = null;
        try {
            preparedStatement = connection.prepareStatement(sql);
            preparedStatement.setString(1, username);
            resultSet = preparedStatement.executeQuery();
            while(resultSet.next()) {
                user = new User();
                user.setId(resultSet.getInt("id"));
                user.setUsername(username);
                user.setBalance(resultSet.getFloat("balance"));
                user.setPassword(resultSet.getString("password"));
                user.setType(resultSet.getInt("type"));
                user.setCredit(resultSet.getFloat("credit"));
            }
        } catch (SQLException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }finally {
            DBUtil.close(resultSet);
            DBUtil.close(preparedStatement);
            DBUtil.close(connection);
        }
        return user;
    }

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