Hibernate mapping maps of heterogeneous inherited objects

Question

I have the next database schema:

CREATE TABLE A (id INTEGER);
CREATE TABLE Single_Values (fk_a INTEGER, fk_b INTEGER, value VARCHAR(255));
CREATE TABLE List_Values (fk_a INTEGER, fk_b INTEGER, value VARCHAR(255));
CREATE TABLE B (id INTEGER, name VARCHAR(255));

And i have next object model (schematic):

class B{
    Integer id;
    String name;
}

class SingleValue extends B{
    String value;
}

class ListValues extends B{
    List<String> values;
}

class A{
    Integer id;
    Map<Integer, SingleValue> singleMap;
    Map<Integer, ListValues> listMap;
}

I made next a mapping to the single value's map:

<class name="B">
   <id name="id"/>
   <property name="name"/>
   <joined-subclass name="SingleValue">
       <key column="fk_b"/>
       <property name="value"/>
   </joined-subclass>
</class>
<class name="A">
    <id name="id"/>
    <map name="singleMap" table="Single_Values">
        <key column="fk_a"/>
        <map-key column="fk_b"/>
        <one-to-many class="B"/>
    </map>
</class>

And I stucked with the mapping of listMap. Any help with mapping this will be appreciated.

ThomasRS · Accepted Answer · 2011-05-02 01:40:54Z

1

Do not use Maps, use Lists. If you want to look up Map-style either use a query or build a temporary map after getting the list from the database. Also, @annotations would make your life more easy?

answered May 2, 2011 at 1:40

ThomasRS

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2 Comments

ilalex Over a year ago

Why does Lists better, then Maps? What is temporary map in terms of hibernate? Or it is just good practice for that? PS. I cant using @annotation, because code style. :(

ThomasRS Over a year ago

It is more that Lists are supported, but Maps are not! The primary key should be part of the object database table, not somehow present in a Map within another object. There is no special hibernate function. You could revise your code style, everyone are using annotations these days.

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