jdbcTemplate.queryForObject 方法注意
发布时间:2022-11-17 22:05:43 318 相关标签: # sql# 数据
正确方法:
String sql = "select ID from Structures(nolock) where id=?";
Integer ret = jdbcTemplate.queryForObject(sql, Integer.class, new Object[]{id});
错误方法:
String sql = "select ID from Structures(nolock) where id=?";
int ret = jdbcTemplate.queryForObject(sql, int.class, new Object[]{id});
String sql = "select * from Structures(nolock) where id=?";
Structure ret = jdbcTemplate.queryForObject(sql, Structure.class, new Object[]{id});
源代码:
public T queryForObject(String sql, Class requiredType, Object... args) throws DataAccessException {
return queryForObject(sql, args, getSingleColumnRowMapper(requiredType));
}
错误分析:queryForObject此重装第2个参数Class requiredType只能是基本数据类型的封装类,如Integer、String
正确方法:
String sql = "select * from Structures(nolock) where id=?";
jdbcTemplate.queryForObject(sql,new Object[]{id},new BeanPropertyRowMapper(Structure.class));
源代码:
public T queryForObject(String sql, Object[] args, RowMapper rowMapper) throws DataAccessException {
List results = query(sql, args, new RowMapperResultSetExtractor(rowMapper, 1));
return DataAccessUtils.requiredSingleResult(results);
}
或者继承queryForObject此实现第3个参数接口RowMapper rowMapper的类,例如:
public class UserInfo implements RowMapper, Serializable {
private Integer id;
private String name;
@Override
public UserInfo mapRow(ResultSet rs, int rowNum) throws SQLException {
UserInfo userInfo = new UserInfo();
userInfo.setId(rs.getInt(id));
userInfo.setUname(rs.getString(uname));
userInfo.setUnumber(rs.getInt(unumber));
userInfo.setuRegisterTime(rs.getDate(uregister_time));
return userInfo;
}
}
简单方法不在类上实现接口:
String sql = "select GoodComments,BadComments,UseCount from Structures(nolock) where id=?";
return jdbcTemplate.queryForObject(sql, new RowMapper(){
@Override
public Structure mapRow(ResultSet rs, int rowNum) throws SQLException{
Structure structure = new Structure();
structure.setGoodComments(rs.getInt("GoodComments"));
structure.setBadComments(rs.getInt("BadComments"));
structure.setUseCount(rs.getInt("UseCount"));
return structure;
}
}, id);
文章来源: https://blog.51cto.com/u_688107/5851367
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