Hi, the below example works fine, hovewer I would like you to check whether this is good approach, as I haven't had such requirement before and I am curious how it should be done.
I have three tables: EMPLOYEE, MEETING, EMPLOYEE_MEETING and only TWO mappings for MANY-TO-MANY relationship betweene EMPLOYEE and MEETING. It seems I am able to insert, load and update everything. What I wanted to achieve was not to create additional mapping, DAO, and separate model for the relation.
Code:
CREATE TABLE `employee_meeting` (
`employee_id` bigint(20) NOT NULL,
`meeting_id` bigint(20) NOT NULL,
`opinion` varchar(50) DEFAULT NULL,
PRIMARY KEY (`employee_id`,`meeting_id`),
KEY `FK_MEETING` (`meeting_id`),
CONSTRAINT `FK_EMPLOYEE` FOREIGN KEY (`employee_id`) REFERENCES `employee` (`employee_id`),
CONSTRAINT `FK_MEETING` FOREIGN KEY (`meeting_id`) REFERENCES `meeting` (`meeting_id`)
) ENGINE=InnoDB DEFAULT CHARSET=latin1$$
Code:
<hibernate-mapping package="net.viralpatel.hibernate">
<class name="Employee" table="EMPLOYEE">
<id name="employeeId" column="EMPLOYEE_ID">
<generator class="native" />
</id>
<property name="firstname" />
<property name="lastname" column="lastname" />
<set name="meetings" table="EMPLOYEE_MEETING" inverse="false" lazy="false" fetch="select" cascade="all" >
<key column="EMPLOYEE_ID" />
<composite-element class="EmployeeMeeting">
<parent name="employee" />
<many-to-one name="meeting" column="MEETING_ID" not-null="true" cascade="all"
class="Meeting" />
<property name="opinion" column="OPINION" />
</composite-element>
</set>
</class>
</hibernate-mapping>
Code:
<hibernate-mapping package="net.viralpatel.hibernate">
<class name="Meeting" table="MEETING">
<id name="meetingId" type="java.lang.Long"
column="MEETING_ID">
<generator class="native" />
</id>
<property name="subject" column="SUBJECT" />
<property name="meetingDate" type="date" column="MEETING_DATE" />
</class>
</hibernate-mapping>
Code:
public static void main(String[] args) {
SessionFactory sf = HibernateUtil.getSessionFactory();
Session session = sf.openSession();
session.beginTransaction();
Meeting meeting1 = new Meeting("Quaterly Sales meeting");
Meeting meeting2 = new Meeting("Weekly Status meeting");
Employee employee1 = new Employee("Sergey", "Brin");
Employee employee2 = new Employee("Larry", "Page");
session.save(meeting1);
EmployeeMeeting em = new EmployeeMeeting(employee1, meeting1, "BAD");
employee1.getMeetings().add(em);
session.save(employee1);
session.save(employee2);
session.getTransaction().commit();
session.evict(employee1);
session.beginTransaction();
Employee e1 = (Employee) session.load(Employee.class, employee1.getEmployeeId());
EmployeeMeeting em2 = e1.getMeetings().iterator().next();
System.out.println("Test1:" + em2.getOpinion());
em2.setOpinion("BETTER");
session.save(e1);
session.getTransaction().commit();
session.evict(e1);
session.beginTransaction();
Employee e2 = (Employee) session.load(Employee.class, employee1.getEmployeeId());
System.out.println("Test2:" + e2.getMeetings().iterator().next().getOpinion());
System.out.println("Test2:" + e2.getMeetings().iterator().next().getMeeting().getMeetingId());
System.out.println("Test2:" + e2.getMeetings().iterator().next().getEmployee().getEmployeeId());
From meeting class I dont need to acess employees.. I only need to access meetings from employees level - Having employee I need to insert, update, delete meetings.
I've made some tests, it seems to be working. One strange thing is when I run this code - I am only loading data from database:
Code:
Employee e2 = (Employee) session.load(Employee.class, new Long(18));
Employee e = (Employee) session.load(Employee.class, new Long(17));
Iterator i = e.getMeetings().iterator();
while (i.hasNext()){
System.out.println(((EmployeeMeeting) i.next()).getMeeting().getMeetingId());
}
System.out.println(e2.getMeetings().iterator().next().getMeeting().getMeetingId());
session.getTransaction().commit();
session.close();
Why HIbernate DELETES and INSERTS meetings when I am only loading data from database???
Code:
Hibernate: select employee0_.EMPLOYEE_ID as EMPLOYEE1_0_0_, employee0_.firstname as firstname0_0_, employee0_.lastname as lastname0_0_ from EMPLOYEE employee0_ where employee0_.EMPLOYEE_ID=?
Hibernate: select meetings0_.EMPLOYEE_ID as EMPLOYEE1_0_, meetings0_.MEETING_ID as MEETING2_0_, meetings0_.OPINION as OPINION0_ from EMPLOYEE_MEETING meetings0_ where meetings0_.EMPLOYEE_ID=?
Hibernate: select employee0_.EMPLOYEE_ID as EMPLOYEE1_0_0_, employee0_.firstname as firstname0_0_, employee0_.lastname as lastname0_0_ from EMPLOYEE employee0_ where employee0_.EMPLOYEE_ID=?
Hibernate: select meetings0_.EMPLOYEE_ID as EMPLOYEE1_0_, meetings0_.MEETING_ID as MEETING2_0_, meetings0_.OPINION as OPINION0_ from EMPLOYEE_MEETING meetings0_ where meetings0_.EMPLOYEE_ID=?
12
11
7
13
7
Hibernate: delete from EMPLOYEE_MEETING where EMPLOYEE_ID=? and MEETING_ID=?
Hibernate: insert into EMPLOYEE_MEETING (EMPLOYEE_ID, MEETING_ID, OPINION) values (?, ?, ?)
Hibernate: delete from EMPLOYEE_MEETING where EMPLOYEE_ID=? and MEETING_ID=?
Hibernate: delete from EMPLOYEE_MEETING where EMPLOYEE_ID=? and MEETING_ID=?
Hibernate: delete from EMPLOYEE_MEETING where EMPLOYEE_ID=? and MEETING_ID=?
Hibernate: delete from EMPLOYEE_MEETING where EMPLOYEE_ID=? and MEETING_ID=?
Hibernate: insert into EMPLOYEE_MEETING (EMPLOYEE_ID, MEETING_ID, OPINION) values (?, ?, ?)
Hibernate: insert into EMPLOYEE_MEETING (EMPLOYEE_ID, MEETING_ID, OPINION) values (?, ?, ?)
Hibernate: insert into EMPLOYEE_MEETING (EMPLOYEE_ID, MEETING_ID, OPINION) values (?, ?, ?)
Hibernate: insert into EMPLOYEE_MEETING (EMPLOYEE_ID, MEETING_ID, OPINION) values (?, ?, ?)
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