Solved

understanding  hibernate mapping tutorial

Posted on 2009-05-17
3
450 Views
Last Modified: 2013-12-29
Here i have attached a  hibernate  Event.hbm.xml file.

I have a query here .

note , we have an entry
<id name="id" column="uid" type="long" unsaved-value="null">  

and also we have entry...

<set name="speakers" cascade="all">
            <key column="event_id"/>
            <one-to-many class="Speaker"/>
        </set>


does that mean hibernate will automatically understand  "id" column  in Event table is a foreign key  "event_id"  column in Speaker table ?

How hibernate will understand that ?i don't see any foreign key tag in the mapping file ....so i am bit confused at this part.

I am not sure , how hibernate will relate these two column .  because i think whenever a value say "1" is saved in "id" field , there will also "1" be saved in event_id column because of this mapping file....right ?



<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC
    "-//Hibernate/Hibernate Mapping DTD 2.0//EN"
    "http://hibernate.sourceforge.net/hibernate-mapping-2.0.dtd">
 
<hibernate-mapping>
    <class name="Event" table="events">
        <id name="id" column="uid" type="long" unsaved-value="null">
            <generator class="increment"/>
        </id>
        <property name="name" type="string" length="100"/>
        <property name="startDate" column="start_date"
                  type="date"/>
        <property name="duration" type="integer"/>
        <many-to-one name="location" column="location_id" class="Location"/>
        <set name="speakers" cascade="all">
            <key column="event_id"/>
            <one-to-many class="Speaker"/>
        </set>
        <set name="attendees" cascade="all">
            <key column="event_id"/>
            <one-to-many class="Attendee"/>
        </set>
    </class>
</hibernate-mapping>

Open in new window

0
Comment
Question by:cofactor
[X]
Welcome to Experts Exchange

Add your voice to the tech community where 5M+ people just like you are talking about what matters.

  • Help others & share knowledge
  • Earn cash & points
  • Learn & ask questions
  • 2
3 Comments
 
LVL 92

Expert Comment

by:objects
ID: 24409058
>            

that specifies which column is the foreign key for a Speaker
And as it is specified in the Event mapping then it relates to the Event class

0
 

Author Comment

by:cofactor
ID: 24409163
the DDL has been given as below in the tutorial

create table events (uid int ,
name varchar,
start_date date,
duration integer,
location_id int)


create table speakers (uid int,
firstName varchar,
lastName varchar,
event_id int)


but  there is no FK constraint put in this  DDL  .....shall  we need to put constraints here ?
0
 
LVL 92

Accepted Solution

by:
objects earned 125 total points
ID: 24409167
up to you, not necessary to make it work.
0

Featured Post

Online Training Solution

Drastically shorten your training time with WalkMe's advanced online training solution that Guides your trainees to action. Forget about retraining and skyrocket knowledge retention rates.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Suggested Solutions

Title # Comments Views Activity
spring maven example issues 3 97
DTD and JAVA versions 1 55
activeMQ Queue Messages Enqueued and Messages Dequeued 1 101
Firefox and firebub 5 24
By the end of 1980s, object oriented programming using languages like C++, Simula69 and ObjectPascal gained momentum. It looked like programmers finally found the perfect language. C++ successfully combined the object oriented principles of Simula w…
Basic understanding on "OO- Object Orientation" is needed for designing a logical solution to solve a problem. Basic OOAD is a prerequisite for a coder to ensure that they follow the basic design of OO. This would help developers to understand the b…
This theoretical tutorial explains exceptions, reasons for exceptions, different categories of exception and exception hierarchy.
This tutorial will introduce the viewer to VisualVM for the Java platform application. This video explains an example program and covers the Overview, Monitor, and Heap Dump tabs.
Suggested Courses

737 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question