Question

I have 2 classes like this :

Message(id, title, content)

MessageEmployee(id, messageId, employeeId, readFlag)

and 2 tables like this :

MESSAGE(mess_id, mess_title, mess_content)

MESSAGE_EMPLOYEE(mess_empl_id, mess_id, empl_id, read_fg)

Mapping files :

    <hibernate-mapping package="core">
        <class name="Message" table="MESSAGE">
            <!-- class id -->
            <id name="id" type="int" column="MESS_ID" length="11">
                <generator class="native"/>
            </id>

            <property name="content" type="string" column="MESS_CONTENT" />
            <property name="title" type="string" column="MESS_TITLE" /> 
        </class>
    </hibernate-mapping>


    <hibernate-mapping package="core">
        <class name="MessageEmployee" table="MESSAGE_EMPLOYEE">
            <!-- class id -->
            <id name="id" type="int" column="MESS_EMPL_ID" length="11">
                <generator class="native"/>
            </id>

            <!-- employee -->
            <many-to-one name="employee" class="core.Employee"
                column="EMPL_ID" cascade="save-update,merge" lazy="false" />

            <!-- message -->
            <many-to-one name="message" class="core.Message"
                column="MESS_ID" cascade="save-update,merge" lazy="false" />

            <property name="readFlag" type="character" column="READ_FG" />      
        </class>
    </hibernate-mapping>

Here is my problem :
let’s say I already have a message in database, and I want to create a messageEmployee and save it.

Code snippet :

    Message sent = new Message(content, title);
    Employee e = employeeDao.loadEmployeeWithId(Integer.valueOf(to));

    messageDao.merge(sent)

    MessageEmployee m = new MessageEmployee(sent, e, null);
    m.setReadFlag('N');
    messageEmployeeDao.mergeMessageEmploye(m);

When I merge(messageEmployee), it creates a new message and a new messageEmployee in database, but I don’t want it to create a new message.

I’m quite sure my mapping is wrong since I am no expert, so what could I change to get the behaviour I want ?

Answer 1

It will create a new Message object because you are not providing id in your message object sent. When you execute messageDao.merge(sent), the sent object doesn’t have and id to merge with. It is pure transient object. Try loading it from database like Employee.