Sleep mode: display 3 tables

Question

I am trying to map some existing tables to Hibernate.

It's pretty simple: we have categories with names in several languages.

DDL is as follows:

create table language (
   id                integer not null auto_increment,
   code              varchar(2) not null,

   unique (code),

   primary key(id)
);

create table category (
   id               integer not null auto_increment,
   parent_id        integer default null,
   ordr             integer not null default 99,

   primary key (id)
);

create table category_description (
   category_id      integer not null,
   language_id      integer not null,

   title            varchar(255) not null,

   constraint foreign key (category_id) references category(id),
   constraint foreign key (country_language_id) references country_language(id),

   primary key (category_id, country_language_id)
);

Now I would like to have a map with the language as its key and description (table category_description) as a value, for example:

private Map<Language, CategoryDescription> descriptions = new HashMap<Language, CategoryDescription>();

Can someone provide me some pointers to this? I tried the example on page 311/312 from "Java Persistence with Hibernate", which looks like my problem, but I just don't get it :(

Answer 1

( DDL , "", "country_language" - )

Hibernate :

<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN" "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<hibernate-mapping default-lazy="false">

    <class name="Language" table="country_language">
        <id name="id" type="int">
            <column name="ID" />
            <generator class="native" />
        </id>
        <property name="code" type="string" length="2" unique="true" />
    </class>

    <class name="Category" table="category">
        <id name="id" type="int">
            <column name="ID" />
            <generator class="native" />
        </id>
        <map name="descriptions" table="category_description">
            <key column="category_id" />
            <map-key-many-to-many column="language_id" class="Language" />
            <composite-element class="CategoryDescription">
                <property name="title" type="string" length="255" />
            </composite-element>
        </map>
    </class>

</hibernate-mapping>

CategoryDescription ( String):

private Map<Language, String> descriptions;

<map name="descriptions" table="category_description">
    <key column="category_id" />
    <map-key-many-to-many column="language_id" class="Language" />
    <element type="string" length="255" column="title" />
</map>

.

, Language hashCode() equals(), :

/* eclipse generated */
@Override
public int hashCode() {
    final int prime = 31;
    int result = 1;
    result = prime * result + ((id == null) ? 0 : id.hashCode());
    return result;
}

/* eclipse generated */
@Override
public boolean equals(Object obj) {
    if (this == obj)
        return true;
    if (obj == null)
        return false;
    if (getClass() != obj.getClass())
        return false;
    Language other = (Language) obj;
    if (id == null) {
        if (other.id != null)
            return false;
    } else if (!id.equals(other.id))
        return false;
    return true;
}