org.hibernate.PropertyAccessException: Null value was assigned to a property of primitive type setter of com.chen.vo.Dept.parentId

异常描述：执行以下的addAsHaveParentId2方法出现此异常：

/*-----------------------类Dept、Dept.hbm.xml有parentId属性(数据库中有此列)----------------------*/
    @Test//添加一级部门--success（parentId为Null）
    public void addAsHaveParentId1(){
        Dept d = new Dept("市场部", "湖北襄阳");
        deptService.saveOrUpdate(d);
    }
    @Test//添加二级部门--fail:原因： deptService.findById(88)的parentId为Null
    public void addAsHaveParentId2(){
        Dept d = deptService.findById(89);
        
        Dept d1 = new Dept("市场部一组", "湖北襄阳");
        d1.setParent(d);
        d.getChilds().add(d1);
        Dept d2 = new Dept("市场部二组", "湖北襄阳");
        d2.setParent(d);
        d.getChilds().add(d2);
        
        deptService.saveOrUpdate(d1);//分别添加子部门
        deptService.saveOrUpdate(d2);
        
//        deptService.saveOrUpdate(d);//也可以只添加上级部门
    }

具体异常信息：

org.hibernate.PropertyAccessException: Null value was assigned to a property of primitive type setter of com.chen.vo.Dept.parentId
    at org.hibernate.property.BasicPropertyAccessor$BasicSetter.set(BasicPropertyAccessor.java:109)
    at org.hibernate.tuple.entity.AbstractEntityTuplizer.setPropertyValues(AbstractEntityTuplizer.java:352)
    at org.hibernate.tuple.entity.PojoEntityTuplizer.setPropertyValues(PojoEntityTuplizer.java:232)
    at org.hibernate.persister.entity.AbstractEntityPersister.setPropertyValues(AbstractEntityPersister.java:3580)
    at org.hibernate.engine.TwoPhaseLoad.initializeEntity(TwoPhaseLoad.java:152)
    at org.hibernate.loader.Loader.initializeEntitiesAndCollections(Loader.java:877)
    at org.hibernate.loader.Loader.doQuery(Loader.java:752)
    at org.hibernate.loader.Loader.doQueryAndInitializeNonLazyCollections(Loader.java:259)
    at org.hibernate.loader.Loader.doList(Loader.java:2232)
    at org.hibernate.loader.Loader.listIgnoreQueryCache(Loader.java:2129)
    at org.hibernate.loader.Loader.list(Loader.java:2124)
    at org.hibernate.loader.hql.QueryLoader.list(QueryLoader.java:401)
    at org.hibernate.hql.ast.QueryTranslatorImpl.list(QueryTranslatorImpl.java:363)
    at org.hibernate.engine.query.HQLQueryPlan.performList(HQLQueryPlan.java:196)
    at org.hibernate.impl.SessionImpl.list(SessionImpl.java:1149)
    at org.hibernate.impl.QueryImpl.list(QueryImpl.java:102)
    at com.chen.dao.BaseDaoImp.getObject(BaseDaoImp.java:64)
    at com.chen.dao.DeptDaoImpl.findById(DeptDaoImpl.java:31)
    at com.chen.service.DeptService.findById(DeptService.java:29)
    at com.chen.service.DeptService$$FastClassByCGLIB$$760bf484.invoke(<generated>)
    at org.springframework.cglib.proxy.MethodProxy.invoke(MethodProxy.java:204)
    at org.springframework.aop.framework.CglibAopProxy$CglibMethodInvocation.invokeJoinpoint(CglibAopProxy.java:713)
    at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:157)
    at org.springframework.transaction.interceptor.TransactionInterceptor$1.proceedWithInvocation(TransactionInterceptor.java:98)
    at org.springframework.transaction.interceptor.TransactionAspectSupport.invokeWithinTransaction(TransactionAspectSupport.java:262)
    at org.springframework.transaction.interceptor.TransactionInterceptor.invoke(TransactionInterceptor.java:95)
    at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:179)
    at org.springframework.aop.interceptor.ExposeInvocationInterceptor.invoke(ExposeInvocationInterceptor.java:92)
    at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:179)
    at org.springframework.aop.framework.CglibAopProxy$DynamicAdvisedInterceptor.intercept(CglibAopProxy.java:646)
    at com.chen.service.DeptService$$EnhancerByCGLIB$$4025fc92.findById(<generated>)
    at com.chen.test.DeptTest.addAsHaveParentId2(DeptTest.java:65)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:606)
    at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:47)
    at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
    at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:44)
    at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)
    at org.springframework.test.context.junit4.statements.RunBeforeTestMethodCallbacks.evaluate(RunBeforeTestMethodCallbacks.java:74)
    at org.springframework.test.context.junit4.statements.RunAfterTestMethodCallbacks.evaluate(RunAfterTestMethodCallbacks.java:83)
    at org.springframework.test.context.junit4.statements.SpringRepeat.evaluate(SpringRepeat.java:72)
    at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.runChild(SpringJUnit4ClassRunner.java:232)
    at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.runChild(SpringJUnit4ClassRunner.java:89)
    at org.junit.runners.ParentRunner$3.run(ParentRunner.java:238)
    at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:63)
    at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:236)
    at org.junit.runners.ParentRunner.access$000(ParentRunner.java:53)
    at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:229)
    at org.springframework.test.context.junit4.statements.RunBeforeTestClassCallbacks.evaluate(RunBeforeTestClassCallbacks.java:61)
    at org.springframework.test.context.junit4.statements.RunAfterTestClassCallbacks.evaluate(RunAfterTestClassCallbacks.java:71)
    at org.junit.runners.ParentRunner.run(ParentRunner.java:309)
    at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.run(SpringJUnit4ClassRunner.java:175)
    at org.eclipse.jdt.internal.junit4.runner.JUnit4TestReference.run(JUnit4TestReference.java:50)
    at org.eclipse.jdt.internal.junit.runner.TestExecution.run(TestExecution.java:38)
    at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:459)
    at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:675)
    at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.run(RemoteTestRunner.java:382)
    at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java:192)
Caused by: java.lang.IllegalArgumentException
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:606)
    at org.hibernate.property.BasicPropertyAccessor$BasicSetter.set(BasicPropertyAccessor.java:66)
    ... 59 more

分析：在类Dept及其配置文件Dept.hbm.xml均有parentId属性，如下所示：

类Dept:

public class Dept {
    private int did;
    private String dname;
    private String loc;
    private int parentId;
  //..
}

Dept.hbm.xml:

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<hibernate-mapping>
<class name="com.chen.vo.Dept" table="t_dept">
<id name="did">
<generator class="sequence">
<param name="sequence">SEQ_DEPT</param>
</generator>
</id>
<property name="dname"/>
<property name="loc"/>
 <property name="parentId" insert="false" update="false"/> 
<!- - 省略.. -->
</class>
</hibernate-mapping>

在执行addAsHaveParentId1方法后，添加了一个一级部门，did为89，其parentId在数据库中为Null（因为在Dept.hbm.xml中设置了insert="false" update="false"，所有不能对此字段执行插入/更新操作）。在执行addAsHaveParentId2方法时，因为类Dept有parentId，所有Hibernate的Sesssion中有维护此字段，但对于did为89的部门来说它是Null的，所以抛出异常。注意：parentId在数据库中为Null没有关系，关键是它在Session中管理中也是Null的，Hibernate因此不能在添加部门时级联添加上级部门（准确的解释目前尚不好说）。

解决方法：删去类Dept中的parentId及相应的配置文件中的parentId

测试：正常！

/*-----------------------类Dept、Dept.hbm.xml中无parentId属性(但数据库中有此列)----------------------*/
    @Test//添加一级部门--success（parentId为Null）
    public void addAsNoParentId1(){
        Dept d = new Dept("市场部", "湖北襄阳");
        deptService.saveOrUpdate(d);
    }
    @Test//添加二级部门--success
    public void addAsNoParentId2(){
        Dept d = deptService.findById(103);
        
        Dept d1 = new Dept("市场部一组", "湖北襄阳");
        d1.setParent(d);
        d.getChilds().add(d1);
        Dept d2 = new Dept("市场部二组", "湖北襄阳");
        d2.setParent(d);
        d.getChilds().add(d2);
        
//        deptService.saveOrUpdate(d1);//分别添加子部门
//        deptService.saveOrUpdate(d2);
        
        deptService.saveOrUpdate(d);//也可以只添加上级部门
    }

小结：对于Hibernate自连接的一对多，多对一的情况——如部门的上级部门与下级部门，最好在掉持久类中的不设置parentId字段，否则在添加部门时级联添加已存在的上级部门会出现此异常。