Spring JdbcDaoSupport 执行SQL
return int: getJdbcTemplate().queryForInt(sql) select count(*)...return List:getJdbcTemplate().query(sql, rowMapper) select ... from ...return null:getJdbcTemplate().update(sql) insert into ... values or delete from ... return null:getJdbcTemplate().update(sql, objects, types) insert into ... values return List:getJdbcTemplate().query(sql, new Object[] { assetId }, new int[] { Types.INTEGER }, rowMapper) select * from ... where id=Object[] objects = new Object[]{user.getId(),user.getName(),user.getPassword()...};int[] types = new int[]{Type.VARCHAR,Type.VARCHAR,Type.VARCHAR,...}
RowMapper对象RowMapper的 mapRow() 方法是留给我们去组装实体类用的,返回是这种类的集合List
Public List<User> getUsers() {String sql = "select * from User";return getJdbcTemplate().query(sql,new ItemRowMapper());}
protected class ItemRowMapper implements RowMapper { //这个类也可以定义在方法里如 RowMapper rowMapper = new 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.setEmail(rs.getString("email")); return item; } }
想象 getJdbcTemplate().query()方法 和 RowMapper类
public List query(String sql, RowMapper rowMapper){int num = 0;List<Object> list = null;Connection conn = null;PreparedStatement pstmt = null;ResultSet rs = null;try{ conn = getConn(); pstmt = conn.prepareStatement(sql); rs = pstmt.executeQuery(); num = 0; while(rs.next()){num++}; list = rowMapper.execute(rs, num);}catch(Exception e){ }finall{ rs.close(); pstmt.close(); conn.close();}return list;}abstract Class RowMapper(){List<Object> list = null;public List execute(ResultSet rs, int rowNum){ //rowNum没用到 while(rs.next){ list.add(mapRow(rs, rowNum)); } return list;}public Object mapRow(ResultSet rs, int RowNum);}
