Hibernate mapping problem one-to-one/many-to-one

I'm facing a problem using Hibernate. I have 3 tables: tb_user, tb_book, tb_lending. In the tb_lending, I have the following fields:

• id_lending - int(11) - primary key
• id_user - int(11) - foreign key
• id_book - int(11) - foreign key

I have also the Beans representing the tables (tb_user and tb_book are working perfectly).

My tbLending.hbm.xml mapping this field:

    <id name="id" type="java.lang.Integer">
        <column name="id_lending" />
        <generator class="identity" />
    </id>
    <many-to-one name="userId" class="com.wa2011.beans.UserBean"
        not-null="true" cascade="all" unique="true" column="id_user" />
    <many-to-one name="bookId" class="com.wa2011.beans.BookBean"
        not-null="true" cascade="all" unique="true" column="id_book" />

From the business logic the association should be one-to-one, since for each id_lending I can have 1 user and 1 book. But I read on some forums to that in this way, using many-to-one and then declaring unique="true".

But then, when I execute a query.save I get the following error:

GRAVE: IllegalArgumentException in class: com.wa2011.beans.UserBean, getter method of property: id

I really don't know what the problem is since tb_book and tb_user as I said before work like a charm.

The save method in the LendingBean.java is:

public void saveLend(LendingBean lendingBean) {
    Session session = iniHibernate();

    try {
        session.beginTransaction();
        session.save(lendingBean);
        session.getTransaction().commit();

    } catch (Exception e) {
        System.out.println("Error on registering lend:");
        System.out.println(e);
    }
}

This method is called by the servlet LendingActions inside the processRequest method, the same pattern I'm following with the other beans/servlets.

<class n开发者_StackOverflowame="com.wa2011.beans.LendingBean" table="tb_lending" catalog="wa2011">
    <id name="id" type="java.lang.Integer">
        <column name="id_lending" />
        <generator class="identity" />
    </id>
...
</class> 

In the LeandingBean.java I have:

@Stateless
public class LendingBean {

   private Integer id;
   private Integer bookId;
   private Integer userId;

...
}

Could you help me, please?

Thanks in advance.

---

Check LendingBean bean's id element to mapping. Is it same as in mapping?

I think your LendingBean should be like this:

@Stateless
public class LendingBean {

   private Integer id;
   private BookBean bookId;
   private UserBean userId;

...
}