调用hibernate自动生成查询方法报错！

[十年一剑般的男人]

if(sjzdflmcs[i].equals("")){
				List<Sjzdxx> list = sjzdxxService.getAllSjzdxxBySjzdfl(sjzdflService.getSjzdflId(sjzdflIds[i]));
				for (Sjzdxx sjzdxx : list) {
					sjzdxx.setSjzdxxName("");
					sjzdxx.setQiyong("no");
					sjzdxxService.UpdateSjzdxx(sjzdxx);
				}
			}

在这里我用sjzdflService.getSjzdflId(sjzdflIds[i]));这一断调用service层的下面这个方法！

public Sjzdfl getSjzdflId(Integer sjzdflId) {
			return (Sjzdfl)sjzdflDAO.findByProperty("sjzdflId", sjzdflId).get(0);
		}

下面是hibernate自动生成的findByProperty方法

public Sjzdfl findById(java.lang.Integer id) {
		log.debug("getting Sjzdfl instance with id: " + id);
		try {
			Sjzdfl instance = (Sjzdfl) getSession()
					.get("com.yyc.po.Sjzdfl", id);
			System.out.println(instance.getSjzdflName());
			return instance;
		} catch (RuntimeException re) {
			log.error("get failed", re);
			throw re;
		}
	}

结果在页面点击提交后，后台没有报错，而是页面上报下面这个错！
Struts Problem Report
Struts has detected an unhandled exception:

Messages:
File: com/yyc/action/UpdateSjzdflAction.java
Line number: 27


--------------------------------------------------------------------------------

Stacktraces
java.lang.NullPointerException
com.yyc.action.UpdateSjzdflAction.execute(UpdateSjzdflAction.java:27)
sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
java.lang.reflect.Method.invoke(Method.java:597)

[安特矮油]

java.lang.NullPointerException
com.yyc.action.UpdateSjzdflAction.execute(UpdateSjzdflAction.java:27)
这里空指针了，看看27行什么对象为null