使用 QueryRunner 查询表中一条或多条记录

https://www.bilibili.com/video/BV1eJ411c7rf?p=52

BeanHandler

    @Test
    public void testQueryBean() {
        Connection conn = null;
        String sql = "select id, name, email, birth from customers where id = ?";

        /*
        AbstractKeyedHandler, AbstractListHandler, ArrayHandler, ArrayListHandler, BaseResultSetHandler,
        BeanHandler, BeanListHandler, BeanMapHandler, ColumnListHandler,
        KeyedHandler, MapHandler, MapListHandler, ScalarHandler
         */
        BeanHandler<Customer> rsh = new BeanHandler(Customer.class);
        Customer customer = null;

        try {
            QueryRunner runner = new QueryRunner();

            conn = JDBCUtils.getConnectionFromDruid();

            customer = runner.query(conn, sql, rsh, 9);

        } catch (SQLException e) {
            e.printStackTrace();
        } finally {
            JDBCUtils.closeResource(conn, null);
        }
        System.out.println(customer);
    }

BeanListHandler

/**
     * BeanListHandler:是 ResultSetHandler 接口的实现类，用于封装表中的多条记录构成的集合
     */
    @Test
    public void testQueryBeanList() {
        Connection conn = null;
        String sql = "select id, name, email, birth from customers where id < ?";

        /*
        AbstractKeyedHandler, AbstractListHandler, ArrayHandler, ArrayListHandler, BaseResultSetHandler,
        BeanHandler, BeanListHandler, BeanMapHandler, ColumnListHandler,
        KeyedHandler, MapHandler, MapListHandler, ScalarHandler
         */
        BeanListHandler<Customer> rsh = new BeanListHandler(Customer.class);
        List<Customer> list = null;
        QueryRunner runner = new QueryRunner();

        try {


            conn = JDBCUtils.getConnectionFromDruid();

            list = runner.query(conn, sql, rsh, 9);

        } catch (SQLException e) {
            e.printStackTrace();
        } finally {
            JDBCUtils.closeResource(conn, null);
        }

        list.forEach(System.out::println);
    }

MapHandler

    /**
     * MapHandler:是 ResultSetHandler 接口的实现类，对应表中的一条记录
     * 将字段及相应字段的值作为 Map 中的 key 和 value
     */
    @Test
    public void testQueryMap() {
        Connection conn = null;
        String sql = "select id, name, email, birth from customers where id = ?";

        /*
        AbstractKeyedHandler, AbstractListHandler, ArrayHandler, ArrayListHandler, BaseResultSetHandler,
        BeanHandler, BeanListHandler, BeanMapHandler, ColumnListHandler,
        KeyedHandler, MapHandler, MapListHandler, ScalarHandler
         */
        MapHandler rsh = new MapHandler();
        Map<String, Object> map = new HashMap<>();
        QueryRunner runner = new QueryRunner();

        try {

            conn = JDBCUtils.getConnectionFromDruid();

            map = runner.query(conn, sql, rsh, 9);

        } catch (SQLException e) {
            e.printStackTrace();
        } finally {
            JDBCUtils.closeResource(conn, null);
        }

        map.forEach((k, v) -> System.out.printf("key:%s, value:%s\n", k, v));
    }

MapListHandler

    /**
     * MapListHandler:是 ResultSetHandler 接口的实现类，对应表中的一条记录
     * 将字段及相应字段的值作为 Map 中的 key 和 value
     */
    @Test
    public void testQueryMapList() {
        Connection conn = null;
        String sql = "select id, name, email, birth from customers where id < ?";

        /*
        AbstractKeyedHandler, AbstractListHandler, ArrayHandler, ArrayListHandler, BaseResultSetHandler,
        BeanHandler, BeanListHandler, BeanMapHandler, ColumnListHandler,
        KeyedHandler, MapHandler, MapListHandler, ScalarHandler
         */
        MapListHandler rsh = new MapListHandler();
        List<Map<String, Object>> list = new ArrayList<>();
        QueryRunner runner = new QueryRunner();

        try {

            conn = JDBCUtils.getConnectionFromDruid();

            list = runner.query(conn, sql, rsh, 9);

        } catch (SQLException e) {
            e.printStackTrace();
        } finally {
            JDBCUtils.closeResource(conn, null);
        }

        list.forEach(System.out::println);

    }