[Okta Webinar] Learn how to a build a cloud-first strategyRegister Now

x
?
Solved

understanding  hibernate mapping tutorial

Posted on 2009-05-17
3
Medium Priority
?
458 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
  • 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 500 total points
ID: 24409167
up to you, not necessary to make it work.
0

Featured Post

Free Tool: Path Explorer

An intuitive utility to help find the CSS path to UI elements on a webpage. These paths are used frequently in a variety of front-end development and QA automation tasks.

One of a set of tools we're offering as a way of saying thank you for being a part of the community.

Question has a verified solution.

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

For beginner Java programmers or at least those new to the Eclipse IDE, the following tutorial will show some (four) ways in which you can import your Java projects to your Eclipse workbench. Introduction While learning Java can be done with…
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…
Viewers learn how to read error messages and identify possible mistakes that could cause hours of frustration. Coding is as much about debugging your code as it is about writing it. Define Error Message: Line Numbers: Type of Error: Break Down…
Viewers will learn about if statements in Java and their use The if statement: The condition required to create an if statement: Variations of if statements: An example using if statements:
Suggested Courses
Course of the Month20 days, 6 hours left to enroll

872 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