Java中连接数据库

第一种方式：

public class DBHelper {

         public static final String url = "jdbc:mysql://127.0.0.1/estoresystem";  
        public static final String name = "com.mysql.jdbc.Driver";  
        public static final String user = "root";  
        public static final String password = "admin";  
      
        public Connection conn = null;  
        public PreparedStatement pst = null;  
      
        public DBHelper(String sql) {  
            try {  
                Class.forName(name);//指定连接类型  
                conn = DriverManager.getConnection(url, user, password);//获取连接  
                pst = conn.prepareStatement(sql);//准备执行语句  
            } catch (Exception e) {  
                e.printStackTrace();  
            }  
        }  
      
        public void close() {  
            try {  
                this.conn.close();  
                this.pst.close();  
            } catch (SQLException e) {  
                e.printStackTrace();  
            }  
        }  
    
}

第二种方式：

import javax.sql.DataSource;
import com.mchange.v2.c3p0.ComboPooledDataSource;
import java.sql.Connection;
import java.sql.SQLException;

public class DataSourceUtils {
/***
 * 连接数据库
 */
    
    private static DataSource dataSource = new ComboPooledDataSource();
    
    private static ThreadLocal<Connection> tl = new ThreadLocal<>();
    
    public static DataSource getDataSource(){
        return dataSource;
    }
    
    /***
     * 当DBUtuls需要手动控制事务的时，调用该方法获得一个连接
     * @return
     * @throws SQLException
     */
    public static Connection getConnection() throws SQLException {
        Connection con = tl.get();
        if(con == null){
            con = dataSource.getConnection();
        }
        return con;
    }
    
    //设置事务为手动事务，相当于开启事务
    public static void startTransaction() {
        try {
            
            getConnection().setAutoCommit(false);
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }
    
    //设置事务回滚
    public static void rollback(){
        try {
            getConnection().rollback();
        } catch (SQLException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }
    
    //事务提交
    public static void commitAndReleased(){
        try {
            getConnection().commit();
            getConnection().close();
        } catch (SQLException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        tl.remove();
    }

}