/**

 * Created by Clear on 2018/8/11.

 * here provide the kind of connections from mysql database,and close the resources of the mysql

 * there are

 *      load driver

 *      use properties file

 *      use xml file

 *      use tomcat

 *      and... so on

 *

 *

 *

 */

public class MysqlUtil {

    /**

     * 链接数据库

     */

    /**

     * 方法一：

     * 加载驱动的方法不止一种，但这种最常用

      */

    public static Connection getConnectionOne(String database,String username,String password){

        try {

            Class.forName("com.mysql.jdbc.Driver");

            Connection connection = DriverManager.getConnection("jdbc:mysql://localhost:3306/"+database,username,

                    password);

            return connection;

        }catch(Exception e){

            e.printStackTrace();

        }

        return null;

    }

    /**

     * 方法二：

     * 利用properties文件

     * ：：：：： 在Web 编程时 文件难以定位

      */

    public static Connection getConnectionTwo() {

        /**

         * 建立文件

         */

        Properties pro = new Properties();

        InputStream in = MysqlUtil.class.getClassLoader().getResourceAsStream("mysqllog.properties");

        try {

            pro.load(in);

            Class.forName(pro.getProperty("driver"));

            String username = pro.getProperty("user");

            String password = pro.getProperty("password");

            String database = pro.getProperty("database");

            String url = pro.getProperty("url");

            Connection connection = DriverManager.getConnection(url+database,username,password);

            return connection;

        } catch (Exception e) {

            e.printStackTrace();

        }

        return null;

    }

    // Connection ,Statement, ResultSet 这几个资源的关闭是有顺序的

    public static void close (Object...objects) throws MysqlCloseException {

        Map<String,Object> map = new HashMap();

        for(Object o : objects){

            if(o instanceof ResultSet){

                map.put("ResultSet",o);

            }else if(o instanceof Connection){

                map.put("Connection",o);

            }else if(o instanceof Statement){

                map.put("Statement",o);

            }else if(o instanceof PreparedStatement){

                map.put("PreparedStatement",o);

            }else{

                throw new MysqlCloseException("关闭异常，不能处理");

            }

        }

        Object obj = map.get("ResultSet");

        if(obj!=null){

            ResultSet r = (ResultSet)obj;

            try {

                r.close();

                map.remove("ResultSet");

            } catch (SQLException e) {

                e.printStackTrace();

            }

        }

        obj = map.get("PreparedStatement");

        if(obj!=null){

            PreparedStatement p = (PreparedStatement)obj;

            try {

                p.close();

                map.remove("PreparedStatement");

            } catch (SQLException e) {

                e.printStackTrace();

            }

        }

        obj = map.get("Statement");

        if(obj!=null){

            Statement s = (Statement)obj;

            try {

                s.close();

                map.remove("Statement");

            } catch (SQLException e) {

                e.printStackTrace();

            }

        }

        obj = map.get("Connection");

        if(obj!=null){

            Connection c = (Connection)obj;

            try{

                c.close();

                map.remove("Connection");

            }catch(SQLException e){

                e.printStackTrace();

            }

        }

    }

}