对孩子进行Hibernate 1到M限制

Question

I have 1 to M association with Country and Person. Meaning a Country can have multiple persons. The country.hbm.xml fils is shown below:

<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC
    "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
    "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<hibernate-mapping package="com.test.hibernate">
  <class name="Country">
  <id name="countryId" column="CountryID" > </id>
  <property name="countryName" column="CountryName" length="50"></property>
  <set name="persons" table="Person" fetch="select" inverse="true">
  <key>
    <column name="CountryId" not-null="true"></column>
  </key> 
   <one-to-many class="com.test.hibernate.Person"/>     
  </set>
  </class>
</hibernate-mapping>

The Person.hbm.xml is shown below

<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC
    "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
    "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<hibernate-mapping package="com.test.hibernate">
  <class name="Person">
    <id name="personID" column="PersonID" > </id>
    <property name="name" column="Name" length="50"></property>
    <property name="age" column="Age"></property>
    <property name="gender" column="Gender" length="1"></property>
    <property name="email" column="Email" length="50"></property>
    <property name="countryID" column="CountryID" insert="false" update="false"></property>

    <many-to-one name="Country" class="com.test.hibernate.Country" fetch="select">
        <column name="CountryID" not-null="true"></column>
    </many-to-one> 
  </class>
</hibernate-mapping>

Now, I am trying to query all the persons who are males belonging to India Country

Criteria countryCriteria = session.createCriteria(Country.class);
Criterion country = Restrictions.eq("countryName", "India");
Criterion male = Restrictions.eq("persons.gender", "M");
countryCriteria.add(country);
countryCriteria.add(male);
List<Country> countryList = countryCriteria.list();

I am getting a Exception in thread "main" org.hibernate.QueryException: could not resolve property: persons.gender of: com.test.hibernate.Country at org.hibernate.persister.entity.AbstractPropertyMapping.propertyException(AbstractPropertyMapping.java:83) at org.hibernate.persister.entity.AbstractPropertyMapping.toColumns(AbstractPropertyMapping.java:98) at org.hibernate.persister.entity.BasicEntityPropertyMapping.toColumns(BasicEntityPropertyMapping.java:61) at org.hibernate.persister.entity.AbstractEntityPersister.toColumns(AbstractEntityPersister.java:1960) at org.hibernate.loader.criteria.CriteriaQueryTranslator.getColumns(CriteriaQueryTranslator.java:523) at org.hibernate.loader.criteria.CriteriaQueryTranslator.findColumns(CriteriaQueryTranslator.java:538) at org.hibernate.criterion.SimpleExpression.toSqlString(SimpleExpression.java:66) at org.hibernate.loader.criteria.CriteriaQueryTranslator.getWhereCondition(CriteriaQueryTranslator.java:419) at org.hibernate.loader.criteria.Crite riaJoinWalker.(CriteriaJoinWalker.java:123) at org.hibernate.loader.criteria.CriteriaJoinWalker.(CriteriaJoinWalker.java:92) at org.hibernate.loader.criteria.CriteriaLoader.(CriteriaLoader.java:95) at org.hibernate.internal.SessionImpl.list(SessionImpl.java:1643) at org.hibernate.internal.CriteriaImpl.list(CriteriaImpl.java:374) at com.test.hibernate.Main.main(Main.java:54)

Please help. I am new to Hibernate.

Thanks in advance.

Answer 1

Country.persons is of type Collection<Person> . A Collection doesn't have any property named "gender".

If you used HQL instead of Criteria (and you should, for such a simple static query), you would have to do a join:

select c from Country c 
join country.persons person
where c.countryName = 'India' 
and person.gender = 'M'

You thus have to do the same with the Criteria query:

Criteria countryCriteria = session.createCriteria(Country.class, "c");
countryCriteria.createALias("c.persons", "person");
countryCriteria.add(Restrictions.eq("c.countryName", "India"));
countryCriteria.add(Restrictions.eq("person.gender", "M"));
List<Country> countryList = countryCriteria.list();

Answer 2

I used M to 1 and used Criteria on Person object as opposed to Country Object.

Criteria personCriteria = session.createCriteria(Person.class,"p");
personCriteria.createAlias("p.Country", "c");    
Criterion gender = Restrictions.eq("gender", "M");
Criterion country = Restrictions.eq("c.countryName", "India");
personCriteria.add(gender);
personCriteria.add(country);
List<Person> personList = personCriteria.list();

This way the personList had all the Persons who were males and belonged to India.