Spring Security standard table fields VS Hibernate required fields

[sergionni]

Looks like clash between standard Spring Security DB tables fields and requirements of Hibernate for fields,in particularly, id field.

From one side, have standard Spring tables(http://static.springsource.org/sprin...ix-schema.html):

create table users(
      username varchar_ignorecase(50) not null primary key,
      password varchar_ignorecase(50) not null,
      enabled boolean not null);

  create table authorities (
      username varchar_ignorecase(50) not null,
      authority varchar_ignorecase(50) not null,
      constraint fk_authorities_users foreign key(username) references users(username));
      create unique index ix_auth_username on authorities (username,authority);

these tables don't contain id fields.

From other side,have Hibernate configuration:

    <class name="model.Authorities" table="authorities">
        <id name="username" column="username"/>
        <property name="authority" column="authority"/>
        <many-to-one name="userDetails" class="model.UserDetails" not-null="false" column="username"/>
    </class>

    <class name="model.UserDetails" table="users">
        <id name="username" column="username"/>
        <property name="password" column="password"/>
        <property name="enabled" column="enabled"/>
        <set name="authorities" cascade="all" inverse="true">
        	<key column="username" not-null="true"/>
        	<one-to-many class="model.Authorities"/>
        </set>
    </class>

Exception got:

org.hibernate.id.IdentifierGenerationException: ids for this class must be manually assigned before calling save(): model.Authorities

What is the best practice?
This case(in order to fix problem) I should add to Hibernate config following:

 <id name="id">
            <generator class="assigned"/>
  </id>

Should I make changes to standard Spring tables and add id fields there?
Is it acceptable or there is other more gracefull solution?