学习记录--spring中的RowMapper

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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;        }    }}

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