Hi,

I have an EmailMessage class which has its own unique key.
Each EmailMessage can be associated with TWO EmailAddress: emailAddressFrom and emailAddressTo

Each EmailAddress is associated with the owner's name.

Example table contents:

EmailMessage Table
---------------
id | email_address_from | email_address_to | message
1 | [email protected] | [email protected] | Hi Sid, See you at lunch, Bob
2 | [email protected] | [email protected] | Bob, See you at 12, Cheers Sid
3 | [email protected] | [email protected] | I'm emailing myself!

Each entry in email_address_from and email_address_to must exist in EmailAddress Table.

EmailAddress Table
---------------
email_address | name
[email protected] | Bob
[email protected] | Sid

Each entry in email_address column must be unique.

(I do not need to be able to get back from email_address in EmailAddress Table to EmailMessage).

I cannot work out the required mappings to get this to work... I've tried one-to-one and property-ref, many-to-one with unique="true" e.t.c., but I've not got anything working (so I've not posted my mapping file which is a mess!).

If anyone could help me write this mapping file for these two classes that'd be much appreciated.

In the EmailAddress class, the mapping to Email Message should be one-to-many, which results in a Set[] (Eclipse generated default) of email Message like this :

private Set emailMessages = new HashSet(0);

and the mapping is something like :

<set name="emailMessages " inverse="true">
<key>
<column name="email_address" not-null="true" />
</key>
<one-to-many class="com.bbah.blah.model.EmailMessage" />
</set>

for the EmailMessage class :

the mapping to EmailAddress class is many-to-one relation, the object class seems to be alright, the mapping is :

<many-to-one name="emailAddressFrom" class="com.bbah.blah.model.EmailAddress" fetch="select">
<column name="email_address_from" not-null="true" />
</many-to-one>

<many-to-one name="emailAddressTo" class="com.bbah.blah.model.EmailAddress" fetch="select">
<column name="email_address_to" not-null="true" />
</many-to-one>

Thanks. I've added tp EmailAddress




and my mapping.hbm.xml file now reads:



What should I use as a pimary key for EmailAddress? I want the email_address itself to be the primary key. As there is no key when I run it I get the error:





Thanks for your help.

You may want to modify it to :


<class name="EmailAddress" table="email_address">
<id name="emailAddress" type="java.lang.String">
<column name="email_address" />
<generator class="assigned" />
</id>

<set name="emailMessages " inverse="true">
<key>
<column name="email_address" not-null="true" />
</key>
<one-to-many class="EmailMessage" />
</set>
<property name="name" type="java.lang.String">
<column name="name" />
</property>
</class>

Thanks. I now get:



from the test code:



Also it has created an email_address column in email_message in addition to email_address_from and email_address_to columns. Is this expected?

Update the mapping "not-null" field if the emailAddressFrom is not a mandatory field.

And if it is a not-null field, you must set the value before creating a new instance.

Try also to "flush" the session if you are creating both a new Email Address and a EmailMessage in the same transaction, so that the newly created Email Address could be referenced by the new EmailMessage object.

Its not null - I've set it using the test code above.

Where should the flush appear?

Thanks

After the creation of EmailAddress.

Is my test code above correct? Inserting session.flush() doesn't seem to make a difference.

<class name="EmailMessage" table="email_message">

<id name="id">
<generator class="native" />
</id>
<property name="emailAddressFromStr" type="java.lang.String">
<column name="email_address_from" not-null="true" />
</property>
<property name="emailAddressToStr" type="java.lang.String">
<column name="email_address_to" not-null="true" />
</property>
<many-to-one name="emailAddressFrom" class="EmailAddress" fetch="select" insert="false" update="false">
<column name="email_address_from" not-null="true" />
</many-to-one>

<many-to-one name="emailAddressTo" class="EmailAddress" fetch="select" insert="false" update="false">
<column name="email_address_to" not-null="true" />
</many-to-one>

<property name="message" />

</class>


Normally I do it this way (Actually I am not sure if it is appropriate), and add property in the object class

private String emailAddressFromStr;
private String emailAddressToStr;

and create the EmailMessage by these two properties.


EmailMessage could then be created by :

EmailMessage emailMessage = new EmailMessage();
emailMessage.setMessage("Hello Sid, Bob here.");

emailMessage.setEmailAddressFrom("[email protected]");
emailMessage.setEmailAddressTo("[email protected]");

Session session = HibernateUtil.getSession();
Transaction tx = session.beginTransaction();
session.save(emailMessage);
tx.commit();
HibernateUtil.closeSession();

Thanks.

That seems I need to add the EmailAddress to email_address table manually?

Is there anyway it could be done automatically when saving EmailMessage?

I misunderstood your problem. I saw from your original post that you already had that records in the DB. If you are creating new records altogether, you may do this :

Session session = HibernateUtil.getSession();
Transaction tx = session.beginTransaction();
EmailMessage emailMessage = new EmailMessage();
emailMessage.setMessage("Hello Sid, Bob here.");

EmailAddress emailAddressFrom = new EmailAddress();
emailAddressFrom.setEmailAddress("[email protected]");
emailAddressFrom.setName("Bob");
session.save(emailAddressFrom );

EmailAddress emailAddressTo = new EmailAddress();
emailAddressTo.setEmailAddress("[email protected]");
emailAddressTo.setName("Sid");
session.save(emailAddressTo );
session.flush();

//suppose you use original mapping
emailMessage.setEmailAddressFrom(emailAddressFrom);
emailMessage.setEmailAddressTo(emailAddressTo);

session.save(emailMessage);

tx.commit();
HibernateUtil.closeSession();

Yes that works.

I was hoping to have the tables "linked" automatically e.g. Just setting up and saving EmailMessage would insert the data into email_address table.

And when you delete a record from email_message if the matching email_address entries no longer match any other email_message they get deleted to.

Is all this possible with Hibernate?

It is not possible for Hibernate to handle such "business logic" for you. You must do that by your own coding.