在hibernate中,當自己用到自定義SQL查詢時,結果集和pojo類的欄位一模一樣,又想方便快捷的不用手動的對映到pojo上,相信大家都遇到過.

看如下程式碼POJO

// 年份
	private String month;
	// 月份
	private String year;
	// 狀態
	private Long status;
	// 建立人
	private String createEmpCode;
	// 建立時間
	private Date createDate;
	// 修改人
	private String updateEmpCode;
	// 修改時間
	private Date updateDate;   get() set()省略....
 

查詢的SQL:

SELECT
        nvl(t.e_year,
        '無') AS year,
        l.m AS month,
        nvl(t.status,0) as status,
        t.create_emp_code as createEmpCode,
        t.create_date as createDate,
        t.update_emp_code as updateEmpCode,
        t.update_date as updateDate 
    FROM
        (SELECT
            LEVEL m 
        FROM
            dual CONNECT 
        BY
            LEVEL <= 12) l 
    LEFT OUTER JOIN
        table t 
            ON l.m = t.e_month 
            AND t.e_year = 1 
            AND t.e_page = 4
    ORDER BY
        l.m 
 

SSH整合查詢程式碼,純Hibernate寫法,主要涉及到一個類(關鍵吶!) 

@SuppressWarnings("unchecked")
	public Collection<Table> findBy(final QueryObj queryObj) {
		final String sql = "SELECT nvl(t.e_year, '無') AS year,l.m AS month,nvl(t.status, 0) as status,"
			+ " t.create_emp_code as createEmpCode,t.create_date as createDate," 
			+ " t.update_emp_code as updateEmpCode,t.update_date as updateDate"
			+ " FROM (SELECT LEVEL m FROM dual CONNECT BY LEVEL <= 12) l"
			+ " LEFT OUTER JOIN table t ON l.m = t.e_month AND t.e_year = ? AND t.e_page = ?"
			+ " ORDER BY l.m ";
		final String year = "year";
		final Long page = 1;
		return (Collection<Table>) super.getHibernateTemplate().execute(
				new HibernateCallback() {
					public Object doInHibernate(Session session)
							throws HibernateException, SQLException {
						SQLQuery query = session
								.createSQLQuery(sql);
						query.setString(0, year);
						query.setLong(1, page);
						//這裡用addScalar指定查詢結果集欄位轉換,尤其是用到sql函式時第一個引數是as 別名,第二個是返回值的型別
						query.addScalar("year", Hibernate.STRING);
						query.addScalar("month", Hibernate.STRING);
						query.addScalar("status", Hibernate.LONG);
						query.addScalar("createEmpCode", Hibernate.STRING);
						query.addScalar("updateEmpCode", Hibernate.STRING);
						query.addScalar("createDate", Hibernate.DATE);
						query.addScalar("updateDate", Hibernate.DATE);
						//關鍵轉換方法query.setResultTransformer,引數AliasToBeanResultTransformer(對映到的POJO類).
						query.setResultTransformer(new AliasToBeanResultTransformer(Table.class));
						//OK hibernate會自動對映過去,如果不用這個方法它返回的時候是Collection<Object>,所以不能起到轉換的作用,在JBoss中執行查詢時會報錯的.
						return query.list();
					}
				});
	}