DBUtils和链接池

DBUtils：简化数据库操做（不用本身设置预处理对象和查询结果集的处理）

核心类：queryrunner类

update（）方法：增、删、改

public static void insert() throws SQLException{
        QueryRunner qr = new QueryRunner();
        String sql = "insert into sort values(?,?,?)";
        Object[] obj = {9,"茶香小排","特别好吃"};
        Connection conn = JDBCUtils.getConnection();
        int row = qr.update(conn,sql,obj);
        conn.close();
        System.out.println(row);
    }
    public static void update() throws SQLException{
        QueryRunner qr = new QueryRunner();
        String sql = "update sort set sname = ?,sdesc =? where sid = ?";
        Object[] obj = {"红烧排骨","通常吧",9};
        Connection conn = JDBCUtils.getConnection();
        int row = qr.update(conn, sql,obj);
        conn.close();
        System.out.println(row);
    }
    public static void delete() throws SQLException{
        QueryRunner qr = new QueryRunner();
        String sql = "delete from sort where sid =?";
        Connection conn = JDBCUtils.getConnection();
        int row = qr.update(conn, sql, 9);
        conn.close();
        System.out.println(row);
    }

query（）方法：查询

resultrshandler类：结果集处理类

arrayhandler：把第一条查询结果放入到object[]数组中

arraylisthandler：把每一条查询结果放入到object[]数组中，再把数组放入到list集合中

beanhandler：把第一条查询结果封装到实体类中

beanlisthandler：把每一条查询结果封装到实体类中， 再把实体类放入到list集合中

columnlisthandler：把某一列结果放入到list集合中

scalarhandler：单一查询结果时使用此类

maphandler：把第一条查询结果放入到map集合中，列名和数据

maplisthandler：把每一条查询结果放入到map集合中，把map放入到list集合中

public static void select1() throws SQLException{
        QueryRunner qr = new QueryRunner();
        String sql = "select * from sort";
        Connection conn = JDBCUtils.getConnection();
        Object[] obj = qr.query(conn, sql, new ArrayHandler());
        conn.close();
        for(Object o:obj){
            System.out.println(o);
        }
    }
    public static void select2() throws SQLException{
        QueryRunner qr = new QueryRunner();
        String sql = "select * from sort";
        Connection conn = JDBCUtils.getConnection();
        List<Object[]> list = qr.query(conn, sql,new ArrayListHandler());
        conn.close();
        for(Object[] obj:list){
            for(Object o:obj){
                System.out.println(o);
            }
            System.out.println();
        }
    }
    public static void select3() throws SQLException{
        QueryRunner qr = new QueryRunner();
        String sql = "select * from sort";
        Connection conn = JDBCUtils.getConnection();
        Sort sort = qr.query(conn, sql,new BeanHandler<Sort>(Sort.class));
        conn.close();
        System.out.println(sort);
    }
    public static void select4() throws SQLException{
        QueryRunner qr = new QueryRunner();
        String sql = "select * from sort";
        Connection conn = JDBCUtils.getConnection();
        List<Sort> list = qr.query(conn, sql,new BeanListHandler<Sort>(Sort.class));
        conn.close();
        for(Sort s:list){
            
            System.out.println(s);
        }
    }
    public static void select5() throws SQLException{
        QueryRunner qr = new QueryRunner();
        String sql = "select * from sort";
        Connection conn = JDBCUtils.getConnection();
        List<String> list = qr.query(conn, sql,new ColumnListHandler<String>("sname"));
        conn.close();
        for(String s:list){
            System.out.println(s);
        }
    }
    public static void select6() throws SQLException{
        QueryRunner qr = new QueryRunner();
        String sql = "select count(*) from sort";
        Connection conn = JDBCUtils.getConnection();
        long count = qr.query(conn, sql,new ScalarHandler<Long>());
        conn.close();
        System.out.println(count);
    }
    public static void select7() throws SQLException{
        QueryRunner qr = new QueryRunner();
        String sql = "select * from sort";
        Connection conn = JDBCUtils.getConnection();
        Map<String, Object> map = qr.query(conn, sql,new MapHandler());
        conn.close();
        for(String key:map.keySet()){
            System.out.println(key+"..."+map.get(key));
        }
    }
    public static void select8() throws SQLException{
        QueryRunner qr = new QueryRunner();
        String sql = "select * from sort";
        Connection conn = JDBCUtils.getConnection();
        List<Map<String,Object>> list = qr.query(conn, sql,new MapListHandler());
        conn.close();
        for(Map<String,Object> map:list){
            for(String s:map.keySet()){
                System.out.println(s+"..."+map.get(s));
            }
            System.out.println();
        }
    }

链接池：使用之前的JDBCUtils工具类，每次数据库交互都会从新开启和关闭一个链接，这样很耗费资源，链接池的出现能够避免资源的浪费

DBCP链接池：实现java提供的链接池接口---DataSource---实现类BasicDataSource

用这个DBCP中的实现类来从新写一个链接池工具类DBUtils

public static void insert() throws SQLException{
            QueryRunner qr = new QueryRunner(DBUtils.getDataSource());
            String sql = "insert into sort values(?,?,?)";
            Object[] obj = {9,"茶香小排","特别好吃"};
            int row = qr.update(sql,obj);
            System.out.println(row);
        }