Map ArrayList with Hibernate

Question

I just coded my first Hibernate examples.

The database connection works and I understand how I can map a String from a POJO to a database field:

private String firstName;

And in the mapping file:

<property name="firstName" type="java.lang.String">
    <column name="FIRSTNAME" />
</property>

But how can I map an ArrayList to the database? A simpl example from the mapping xml file would be appreciated.

Cheers

UPDATE

I switched to List instead of ArrayList found an example. Now I map as follows:

    <list name="test" inverse="false" table="CONTACT" lazy="true">
        <key>
            <column name="ID" />
        </key>
        <list-index></list-index>
        <element type="java.lang.String">
            <column name="TEST" />
        </element>
    </list>

Unfortunately, I get an exception that I do not understand:

Exception in thread "main" org.hibernate.MappingException: Foreign key (FK6382B0003257FF7F:CONTACT [ID])) must have same number of columns as the referenced primary key (CONTACT [ID,idx])

Any ideas?

Cheers

Vincent Ramdhanie · Accepted Answer · 2010-12-01 13:43:48Z

6

I notice that you are using XML to map your POJOs. You will find some information about that here.

for example:

   <list name="myArrayListProperty" cascade="all">
        <key column="parent_id"/>
        <index column="idx"/>
        <one-to-many class="WhatIsInTheList"/>
    </list>

However, using annotations have some advantages. This link will explain how to map any collection using annotations.

answered Dec 1, 2010 at 13:43

Vincent Ramdhanie

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1 Comment

Martin Preusse Over a year ago

Thanks, I didn't know about annotations but it seems to be easier.

Bozho · Accepted Answer · 2010-12-01 13:37:03Z

1

See the collection mapping section of the docs. There are multiple ways to map a list (one-to-many, many-to-many, a collection of elements). You can map it as a list or as a bag, so read the whole section.

answered Dec 1, 2010 at 13:37

Bozho

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Martin Preusse Over a year ago

Thanks for your help, but this kind of answer is not very helpful for somebody who is new to a certain technology. Everything is in the docs, but usually you don't understand it. I don't know how you star tlearning something new, but I put together small 'Hello World' examples. An actual code fragment would have been much more useful.

Alberto Vazquez · Accepted Answer · 2012-03-04 00:13:07Z

You have a little error in the XML configuration:

When you have a list the solution to map this list using a database is to link with a additional table, so instead of doing:

<list name="test" inverse="false" table="CONTACT" lazy="true">
        <key>
            <column name="ID" />
        </key>
        <list-index></list-index>
        <element type="java.lang.String">
            <column name="TEST" />
        </element>
</list>

You should have to do map to a new data table that holds the list values:

<list name="test" inverse="false" table="CONTACT_test" lazy="true">
        <key>
            <column name="ID" />
        </key>
        <list-index></list-index>
        <element type="java.lang.String">
            <column name="TEST" />
        </element>
</list>

Hibernate automatically creates the new table for you.

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