Hi,
I am new to Hibernate and want to use this great framework in my work.
To play around with Hibernate, I've created 3 tables in my database. The layout of the tables is as follow:
Table Student:
-idStudent (primary key)
-Vorname
-Nachname
Table Student2Vorlesung:
-idZuordnung (primary key)
-FSStudent (foreign key, references idStudent in table Student)
-FSVorlesung (foreign key, references idVorlesung in table Vorlesung)
Table Vorlesung:
-idVorlesung (primary key)
-Name
Now I want to map the Students to the Vorlesungen. Because it is a n:m relation, the table Student2Vorlesung models this relation. Now I want to add a Vorlesung to a Student as shown below in the code section, but unfortunately this action fails :(
Can someone help me and tell what I do wrong?
Hibernate version: 3.2.2 GA
Mapping documents:
Vorlesung.hbm.xml:
Code:
<?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="hibernate.Vorlesung" table="Vorlesung">
<id name="idVorlesung" column="idVorlesungD">
<generator class="native"/>
</id>
<property name="Name"/>
</class>
</hibernate-mapping>
Student.hbm.xml:
Code:
<?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="hibernate.Student" table="Student">
<id name="idStudent" column="idStudent">
<generator class="native"/>
</id>
<property name="Vorname"/>
<property name="Nachname"/>
<set name="vorlesungen" table="Student2Vorlesung">
<key column="idStudent"/>
<many-to-many column="idVorlesung" class="hibernate.Vorlesung"/>
</set>
</class>
</hibernate-mapping>
Code:
Session session = InitSessionFactory.getInstance().getCurrentSession();
session.beginTransaction();
Student aStudent = (Student) session.load(Student.class, new Long(1));
Vorlesung aVorlesung = (Vorlesung) session.load(Vorlesung.class, new Long(2));
aStudent.getVorlesungen().add(aVorlesung);
session.getTransaction().commit();
Full stack trace of any exception that occurs:Code:
Exception in thread "main" org.hibernate.exception.SQLGrammarException: could not load an entity: [hibernate.Student#1]
at org.hibernate.exception.SQLStateConverter.convert(SQLStateConverter.java:67)
at org.hibernate.exception.JDBCExceptionHelper.convert(JDBCExceptionHelper.java:43)
at org.hibernate.loader.Loader.loadEntity(Loader.java:1865)
at org.hibernate.loader.entity.AbstractEntityLoader.load(AbstractEntityLoader.java:48)
at org.hibernate.loader.entity.AbstractEntityLoader.load(AbstractEntityLoader.java:42)
at org.hibernate.persister.entity.AbstractEntityPersister.load(AbstractEntityPersister.java:3038)
at org.hibernate.event.def.DefaultLoadEventListener.loadFromDatasource(DefaultLoadEventListener.java:395)
at org.hibernate.event.def.DefaultLoadEventListener.doLoad(DefaultLoadEventListener.java:375)
at org.hibernate.event.def.DefaultLoadEventListener.load(DefaultLoadEventListener.java:139)
at org.hibernate.event.def.DefaultLoadEventListener.onLoad(DefaultLoadEventListener.java:98)
at org.hibernate.impl.SessionImpl.fireLoad(SessionImpl.java:878)
at org.hibernate.impl.SessionImpl.immediateLoad(SessionImpl.java:836)
at org.hibernate.proxy.AbstractLazyInitializer.initialize(AbstractLazyInitializer.java:66)
at org.hibernate.proxy.AbstractLazyInitializer.getImplementation(AbstractLazyInitializer.java:111)
at org.hibernate.proxy.pojo.cglib.CGLIBLazyInitializer.invoke(CGLIBLazyInitializer.java:140)
at hibernate.Student$$EnhancerByCGLIB$$e1f810d6.getVorlesungen(<generated>)
at hibernate.TestExample.main(TestExample.java:41)
Caused by: org.postgresql.util.PSQLException: ERROR: relation "student" does not exist
at org.postgresql.core.v3.QueryExecutorImpl.receiveErrorResponse(QueryExecutorImpl.java:1548)
at org.postgresql.core.v3.QueryExecutorImpl.processResults(QueryExecutorImpl.java:1316)
at org.postgresql.core.v3.QueryExecutorImpl.execute(QueryExecutorImpl.java:191)
at org.postgresql.jdbc2.AbstractJdbc2Statement.execute(AbstractJdbc2Statement.java:452)
at org.postgresql.jdbc2.AbstractJdbc2Statement.executeWithFlags(AbstractJdbc2Statement.java:351)
at org.postgresql.jdbc2.AbstractJdbc2Statement.executeQuery(AbstractJdbc2Statement.java:255)
at org.hibernate.jdbc.AbstractBatcher.getResultSet(AbstractBatcher.java:186)
at org.hibernate.loader.Loader.getResultSet(Loader.java:1778)
at org.hibernate.loader.Loader.doQuery(Loader.java:662)
at org.hibernate.loader.Loader.doQueryAndInitializeNonLazyCollections(Loader.java:224)
at org.hibernate.loader.Loader.loadEntity(Loader.java:1851)
... 14 more
Name and version of the database you are using:PostgreSQL 8.2
The generated SQL (show_sql=true):
Hibernate: select student0_.idStudent as idStudent1_0_, student0_.Vorname as Vorname1_0_, student0_.Nachname as Nachname1_0_ from Student student0_ where student0_.idStudent=?
Thanks for your help and time!
Bye,
TMK
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