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

public class DBManager {
	
	public static final String DRIVER = "com.mysql.jdbc.Driver";
	public static final String URL = 
		"jdbc:mysql://localhost:3306/Library_System?useUnicode=true&characterEncoding=UTF-8";
	public static final String USER = "root";
	public static final String PASSWORD = "java";
	
	/**
	 * 得到连接
	 * @param url
	 * @param user
	 * @param password
	 * @return
	 * @throws Exception
	 */
	public static Connection getConn() throws Exception{
		
		Class.forName(DRIVER);
		
		return DriverManager.getConnection(URL, USER,PASSWORD);
		
	}
	
	/**
	 * 关闭连接
	 * @param con
	 * @param pStatement
	 * @param rSet
	 */
	
	public static void close(Connection con,PreparedStatement pStatement,ResultSet rSet){
		
		if(null != con){try {con.close();} catch (SQLException e) {}finally{con = null;}}
		
		if(null != pStatement){try {pStatement.close();} catch (SQLException e) {}finally{pStatement = null;}}
		
		if(null != rSet){try {rSet.close();} catch (SQLException e) {}finally{rSet = null;}}
		
	}
	
	
	/**
	 * 封装insert(),update(),delete()方法对数据库的操作
	 * @param sql
	 * @param params
	 * @return result 返回影响的行数
	 * @throws Exception
	 */
	public static int MySqlExecuteUpdate(String sql,Object...params)throws Exception{
		
		Connection conn = TransAnctionFilter.Transcon.get();//从本地线程里取出conn
		//Connection conn = getConn();
		
		PreparedStatement pStatement = conn.prepareStatement(sql);
		
		for(int i = 0;i < params.length;i++){
			
			pStatement.setObject(i + 1, params[i]);
			
		}
		
		int result = pStatement.executeUpdate();
		
		close(null, pStatement, null);
		
		return result;
		
	}
	
	/**
	 * 封装select()方法对数据库的操作
	 * @param sql
	 * @param params
	 * @return 返回查询的结果集
	 * @throws Exception
	 */
	public static ResultSet MySqlExecuteSelect(String sql,Object...params)throws Exception{
		
		Connection conn = TransAnctionFilter.Transcon.get();//从本地线程里取出conn
		
		//Connection conn = getConn();
		
		PreparedStatement pStatement = conn.prepareStatement(sql);
		
		for(int i = 0;i < params.length;i++){
			
			pStatement.setObject(i + 1, params[i]);
			
		}
		
		ResultSet rSet = pStatement.executeQuery();
		
		return rSet;
		
	}

}