学习记录--spring中的RowMapper

Sping中的RowMapper可以将数据中的每一行数据封装成用户定义的类.

我们在数据库查询中，如果返回的类型是用户自定义的类型(其实我们在数据库查询中大部分返回的都是自定义的类)则需要包装，如果是Java自定义的类型，如：String则不需要。如果sping与hibernate 相结合了,基本上是用不到,大多数都是在spring单独使用时用到。可以通过建立内部类实现RowMapper接口,RowMapper中有一个mapRow方法,所以实现RowMapper接口一定要实现mapRow方法,而对自定义类的包装就在mapRow方法中实现。

public class ItemDAOImpl {
    private JdbcTemplate jdbcTemplate;

    public void setJdbcTemplate(JdbcTemplate jdbcTemplate) {
        this.jdbcTemplate = jdbcTemplate;
    }

    public Item insert(Item item) {
        String sql = "INSERT INTO items(user_id,name,phone,email) VALUES(?,?,?,?)";
        Object[] params = new Object[] { item.getUserId(), item.getName(),
                item.getPhone(), item.getEmail() };
        int[] types = new int[] { Types.INTEGER, Types.VARCHAR, Types.CHAR,
                Types.VARCHAR };
        jdbcTemplate.update(sql, params, types);
        return item;
    }

    public Item update(Item item) {
        String sql = "UPDATE items SET name = ?, phone = ?, email = ? WHERE id = ?";
        Object[] params = new Object[] { item.getName(), item.getPhone(),
                item.getEmail(), item.getId() };
        int[] types = new int[] { Types.VARCHAR, Types.CHAR, Types.VARCHAR,
                Types.VARCHAR, Types.INTEGER };
        jdbcTemplate.update(sql, params, types);

        return item;
    }

    public void delete(Item item) {
        String sql = "DELETE FROM items WHERE id = ?";
        Object[] params = new Object[] { item.getId() };
        int[] types = new int[] { Types.INTEGER };
        jdbcTemplate.update(sql, params, types);
    }

    public Item findById(int id) {
        String sql = "SELECT * FROM items WHERE id = ?";
        Object[] params = new Object[] { id };
        int[] types = new int[] { Types.INTEGER };
        List items = jdbcTemplate.query(sql, params, types, new ItemMapper());
        if (items.isEmpty()) {
            return null;
        }
        return (Item) items.get(0);
    }

    public List<Item> findAll() {
        String sql = "SELECT * FROM items";
        return jdbcTemplate.query(sql, new ItemMapper());
    }

    public List<Item> findAllByUser(int user_id) {
        String sql = "SELECT * FROM items WHERE user_id = ?";
        Object[] params = new Object[] { user_id };
        int[] types = new int[] { Types.INTEGER };
        List items = jdbcTemplate.query(sql, params, types, new ItemMapper());
        return items;
    }

    protected class ItemMapper implements RowMapper {

        public Object mapRow(ResultSet rs, int rowNum) throws SQLException {
            Item item = new Item();
            item.setId(rs.getInt("id"));
            item.setUserId(rs.getInt("user_id"));
            item.setName(rs.getString("name"));
            item.setPhone(rs.getString("phone"));
            item.setEmail(rs.getString("email"));

            return item;
        }

    }

}