当前位置：首页 > news >正文

hibernate的Criteria的一个bug

news 来源：原创 2024/5/3 19:27:05

这个bug是在使用hibernate annotation过程中发现的，开始以为是hibenrate annotation的bug，后来又使用xml文件来配置，还是存在同样的问题。
问题场景：我需要使用省份与城市，他们的关系是：一个省有个多城市，很简单的OneToMany关系，在改变province中的cities的lazy特性时，遇到问题
由于我采用把所有的资源都是放在一个表中的策略，所有这里有一个基类Resource

基类

@Entity

@Inheritance(strategy = InheritanceType.SINGLE_TABLE)

@DiscriminatorColumn(name = " CATEGORY_ID " ,discriminatorType = DiscriminatorType.STRING)

@Table(name = " T_RESOURCE " )

public class Resource implements Serializable ... {

privateStringid;

privateStringname;

privateResourceCategoryresourceCategory;

@Id

@GenericGenerator(name="generator",strategy="uuid")

@GeneratedValue(generator="generator")

@Column(name="ID")

publicStringgetId()...{

returnid;

}

@Column(name="NAME")

publicStringgetName()...{

returnname;

}

@ManyToOne(fetch=FetchType.LAZY)

@JoinColumn(name="CATEGORY_ID",updatable=false,insertable=false)

publicResourceCategorygetResourceCategory()...{

returnresourceCategory;

}

@Override

publicbooleanequals(finalObjectother)...{

if(!(otherinstanceofResource))

returnfalse;

ResourcecastOther=(Resource)other;

returnnewEqualsBuilder().append(id,castOther.id).isEquals();

}

@Override

publicinthashCode()...{

returnnewHashCodeBuilder().append(id).toHashCode();

}

Province子类

@Entity

@DiscriminatorValue( " province " )

public class Province extends Resource ... {

privateSet<City>cities=newHashSet<City>();

@OneToMany(cascade=CascadeType.ALL,fetch=FetchType.EAGER,mappedBy="province")

publicSet<City>getCities()...{

returncities;

}

子类City

@Entity

@DiscriminatorValue( " city " )

public class City extends Resource ... {

privateProvinceprovince;

publicCity(Stringname,ResourceCategoryresourceCategory)...{

super(name,resourceCategory);

}

@ManyToOne

@JoinColumn(name="PARENT_ID")

publicProvincegetProvince()...{

returnprovince;

}

hibernate.cfg.xml

<!--

<mappingresource="ResourceCategory.hbm.xml"/>

<mappingresource="Resource.hbm.xml"/>

-->

< mapping class ="ResourceCategory" />

< mapping class ="Resource" />

hibernate助手类

public class HibernateUtil ... {

privatestaticSessionFactorysessionFactory;

static...{

//Configurationconfiguration=newConfiguration();

AnnotationConfigurationconfiguration=newAnnotationConfiguration();

configuration.configure();

sessionFactory=configuration.buildSessionFactory();

}

publicstaticSessionFactorygetSessionFactory()...{

returnsessionFactory;

}

publicSessiongetSession()...{

returngetSessionFactory().openSession();

}

单元测试类

public class HibnerateTest extends TestCase ... {

publicvoidtestListProvinceByHQL()...{

SessionFactorysessionFactory=HibernateUtil.getSessionFactory();

Sessionsession=sessionFactory.openSession();

Transactionctx=session.beginTransaction();

Queryquery=session.createQuery("fromProvince");

List<Province>provinces=query.list();

for(Provinceprovince:provinces)...{

System.out.println(province.getName());

}

ctx.commit();

}

publicvoidtestListProvinceByCriteria()...{

SessionFactorysessionFactory=HibernateUtil.getSessionFactory();

Sessionsession=sessionFactory.openSession();

Transactionctx=session.beginTransaction();

Criteriacriteria=session.createCriteria(Province.class);

List<Province>provinces=criteria.list();

for(Provinceprovince:provinces)...{

System.out.println(province.getName());

}

ctx.commit();

}

分别执行单元测试方法，他们输出的sql语句是一样的，但是输出的结果是不一样的。
select this_.ID as ID1_1_, this_.NAME as NAME1_1_, this_.COMMENTS as COMMENTS1_1_, this_.CATEGORY_ID as CATEGORY2_1_1_, cities2_.PARENT_ID as PARENT5_3_, cities2_.ID as ID3_, cities2_.ID as ID1_0_, cities2_.NAME as NAME1_0_, cities2_.COMMENTS as COMMENTS1_0_, cities2_.CATEGORY_ID as CATEGORY2_1_0_, cities2_.PARENT_ID as PARENT5_1_0_ from T_RESOURCE this_ left outer join T_RESOURCE cities2_ on this_.ID=cities2_.PARENT_ID where this_.CATEGORY_ID='province'
testListProvinceByHQL方式输出的是
上海
上海
上海
上海
江苏
江苏
江苏
江苏

testListProvinceByCriteria方式输出的是
上海
江苏

若把public Set<City> getCities()的映射改为
@OneToMany(cascade = CascadeType.ALL, fetch = FetchType.EAGER, mappedBy = "province")
@Fetch(FetchMode.SELECT)
或者
@OneToMany(cascade = CascadeType.ALL, mappedBy = "province")
@LazyCollection(LazyCollectionOption.FALSE)

则两个方法输出sql语句是一样的，且结果也一样
SQL:
select this_.ID as ID1_0_, this_.COMMENTS as COMMENTS1_0_, this_.NAME as NAME1_0_, this_.CATEGORY_ID as CATEGORY1_1_0_ from T_RESOURCE this_ where this_.CATEGORY_ID='province'
select cities0_.PARENT_ID as PARENT5_1_, cities0_.ID as ID1_, cities0_.ID as ID1_0_, cities0_.COMMENTS as COMMENTS1_0_, cities0_.NAME as NAME1_0_, cities0_.CATEGORY_ID as CATEGORY1_1_0_, cities0_.PARENT_ID as PARENT5_1_0_ from T_RESOURCE cities0_ where cities0_.PARENT_ID=?
select cities0_.PARENT_ID as PARENT5_1_, cities0_.ID as ID1_, cities0_.ID as ID1_0_, cities0_.COMMENTS as COMMENTS1_0_, cities0_.NAME as NAME1_0_, cities0_.CATEGORY_ID as CATEGORY1_1_0_, cities0_.PARENT_ID as PARENT5_1_0_ from T_RESOURCE cities0_ where cities0_.PARENT_ID=?
输出：
上海
江苏

从上面的现象可是看出，不论配置文件怎么变化，通过hql语句获得结果一直不变，而Criteria会变化，这就证明了Criteria是有bug的。
据此我得出结论:hibernate的Criteria在把关联的lazy属性设置为"false"，且把fetch设置为join时，查找数据就存在bug

后来我使用xml配置文件的方式，也存在同样的问题，也证明了我的这个结论，

Resource.hbm.xml

<? xmlversion="1.0" ?>

<! DOCTYPEhibernate-mappingPUBLIC"-//Hibernate/HibernateMappingDTD3.0//EN"

"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd" >

< hibernate-mapping >

< class name ="Resource"

table ="T_RESOURCE" >

< id name ="id" type ="string" >

< column name ="ID" />

</ id >