Hello. I have attached the relevant parts of my mapping document below.
I have a one-to-many relationship between a Course object and an Event object, since a course may be presented numerous times.
I'm using hbm2java to create my java objects. The Course object is created as I would expect with a Set of event objects, but the Event object is not. I would expect the Event object to contain a reference to a single Course object, but instead the generated code uses java.util.Map. When I tried to use the code as generated, I received an "object is not an instance of declaring class". When I change my generated pojo to reference a single Course object, it works great.
My questions are this:
Do I have my many-to-one relationship specified correctly in the Event object? I followed examples in the documentation.
Why does hbm2java create the course object gets/sets as Map objects instead of references to a single Course class?
What is the advantage of this?
If this is the default code generation is correct, how do I use a HashMap to store a reference to a single object correctly?
Thank you for your time,
Perry Tew
Generated Code by hbm2java for Event.java:
Code:
/** nullable persistent field */
private java.util.Map course;
public java.util.Map getCourse() {
return this.course;
}
public void setCourse(java.util.Map course) {
this.course = course;
}
The altered Event.java that works:Code:
/** nullable persistent field */
private Course course;
public Course getCourse() {
return this.course;
}
public void setCourse(Course course) {
this.course = course;
}
My attempt to use the generated code, which failed (the Course object does exist in the db with the proper id):Code:
Session hSession = HibernateUtil.currentSession();
Long courseId = new Long(1);
Course course = (Course) hSession.load(Course.class, courseId);
Event event = new Event();
event.setDateOfMeeting(new Date());
event.setCity("Atlanta");
event.setState("GA");
event.setStartTime("now");
event.setEndTime("then");
event.setNumberOfAttendees(new Integer(5));
event.setContactName("joe");
event.setContactPhone("123");
event.setContactEmail("joe@aol.com");
//============================
HashMap courses = new HashMap();
courses.put(course, course); // not sure where to put the course? key, value? I tried both.
event.setCourse(courses);
//============================
Transaction tx = hSession.beginTransaction();
hSession.saveOrUpdate(event);
tx.commit();
Here is my code using the Event class as I modified it to contain a single reference to a Course object. It works well. (the Course object does exist in the db with the proper id):Code:
Session hSession = HibernateUtil.currentSession();
Long courseId = new Long(1);
Course course = (Course) hSession.load(Course.class, courseId);
Event event = new Event();
event.setDateOfMeeting(new Date());
event.setCity("Atlanta");
event.setState("GA");
event.setStartTime("now");
event.setEndTime("then");
event.setNumberOfAttendees(new Integer(5));
event.setContactName("joe");
event.setContactPhone("123");
event.setContactEmail("joe@aol.com");
//============================
event.setCourse(course);
//============================
Transaction tx = hSession.beginTransaction();
hSession.saveOrUpdate(event);
tx.commit();
Hibernate version: 3.0
Name and version of the database you are using: Oracle 9.2.0
The generated SQL (show_sql=true): N/A
Debug level Hibernate log excerpt: N/A
Mapping documents:Code:
<hibernate-mapping default-lazy="true">
<class name="cv.speakerbureau.Course" table="spk_course" select-before-update="true" rowid="rowid">
<id name="id" column="course_id" type="long" unsaved-value="null">
<generator class="sequence">
<param name="sequence">spk_id_seq</param>
</generator>
</id>
<property name="id" column="course_id" type="long" insert="false" update="false" not-null="true"/>
<property name="title" column="title" type="string" length="200" not-null="true"/>
<property name="courseNo" column="course_num" type="string" length="20" not-null="true"/>
<set name="events" lazy="true">
<key column="course_id"/>
<one-to-many class="cv.speakerbureau.Event"/>
</set>
</class>
<class name="cv.speakerbureau.Event" table="spk_event" select-before-update="true" rowid="rowid">
<id name="id" column="event_id" type="long" unsaved-value="null">
<generator class="sequence">
<param name="sequence">spk_id_seq</param>
</generator>
</id>
<property name="id" column="event_id" type="long" insert="false" update="false" not-null="true"/>
<property name="dateOfMeeting" column="date_of_meeting" type="date" not-null="true"/>
<property name="city" column="city" type="string" length="50" not-null="true"/>
<property name="state" column="state" type="string" length="2" not-null="true"/>
<many-to-one name="course" column="course_id" class="cv.speakerbureau.Course" not-null="false" fetch="join" />
</class>
</hibernate-mapping>
Here is the log output from hbm2java.:
DEBUG 2005-03-09 08:29:06,736 [main] (ClassMapping.java:68) - Processing mapping for class: cv.speakerbureau.Event
INFO 2005-03-09 08:29:06,737 [main] (FieldProperty.java:52) - fieldname = id
INFO 2005-03-09 08:29:06,741 [main] (FieldProperty.java:52) - fieldname = dateOfMeeting
INFO 2005-03-09 08:29:06,742 [main] (FieldProperty.java:52) - fieldname = city
INFO 2005-03-09 08:29:06,743 [main] (FieldProperty.java:52) - fieldname = state
INFO 2005-03-09 08:29:06,754 [main] (FieldProperty.java:52) - fieldname = course
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