java - Spring 3.x + SimpleJdbcTemplate : Returning multiple columns

Question

我正在使用 SimpleJdbcTemplate 和 Spring 3.x。为了获取单个列，我使用下面的代码，它工作正常:

public String selectSingleColumn(int deptId){
    return jdbcTemplate.queryForObject("SELECT DEPT_NAME FROM DEPT WHERE DEPT_ID = ?", String.class, deptId);
}

问题:

我想从上面的表中获取多个列，例如DEPT_NAME和DEPT_CODE(但不是所有属于该表的列)，如何将上面的代码修改为完成它？在这种情况下，我对 queryForObject 的第二个参数感到困惑；理想情况下，我认为它应该是 Object[] 但仍然很困惑。请指导我。

Answer 1

我只需查询整个域对象，而不必为不同的列编写不同的查询。其一，它使 dao 更加可重用。

例如:

部门域对象

public class Department {
    private long id;
    private String deptName;
    private String deptCode;
    // other fields

    // getters and setters
}

部门Dao

public class DepartmentDaoImpl extends JdbcTemplate implements DepartmentDao {

    private static final String DEPT_BY_ID 
                          = "select * from DEPARTMENT where DEPT_ID = ?";

    @Override
    public Department getDepartmentById(long id) {
        return (Department) queryForObject(
             DEPT_BY_ID, 
             new Object[] { id },
             new RowMapper<Department>() {
                 @Override
                 public Department mapRow(ResultSet rs, int rowNumber) {
                     Department dept = new Department();
                     dept.setId(rs.getLong("DEPT_ID");
                     dept.setDeptName(rs.getString("DEPT_NAME");
                     dept.setDeptCode(rs.getString("DEPT_CODE");
                     // set other properties

                     return dept;
                 }
             });
    }
}

如果你真的真的只想要两列，你可以使用queryForMap

public class TestCustomerDao extends JdbcTemplate implements DepartmentDao {

    private static final String FOR_MAP 
                = "select DEPT_NAME,DEPT_CODE from DEPARTMENT where DEPT_ID = ?";

    @Override
    public Map<String, Object> getCoupleColumnsById(long id) {
        return (Map<String, Object>)queryForMap(FOR_MAP, new Object[] {id});
    }
}

map 将返回为

   key        value
DEPT_NAME  =  value
DEPT_CODE  =  value