Only 1 item in One-to-Many Set returned

parkerjo · **Joined:** Thu Nov 06, 2003 12:38 pm **Posts:** 3

I'm trying to learn hibernate with this simple example. I have User, UserRole and Role tables. A User can have many Roles and many Roles can be assigned to a User.

This piece of code returns the populated UserBean. The problem is it only returns 1 Role in the Set. How do I make it populate all Roles for the User? Am I over simplfying it? What am I missing?

-John

Code:

   public UserBean getUser(String name) throws HibernateException
   {
      UserBean user = (UserBean) _hibernateSession.load(UserBean.class, name);
      
      _hibernateSession.close();
      _factory.close();
      return user;
   }

Code:

public class UserBean
{
   private String _name;
   private String _password;
   private Set _roles;

   /**
    * Constructor for UserBean.
    */
   public UserBean()
   {
      super();
   }
   public void setName(String name)
   {
      _name = name;
   }
   public void setPassword(String password)
   {
      _password = password;
   }
   
   public String getName()
   {
      return _name;
   }
   
   public String getPassword()
   {
      return _password;
   }
   
   public void setRoles(Set roles)
   {
      _roles = roles;
   }
   
   public Set getRoles()
   {
      return _roles;
   }
   
   public Iterator getIterator()
   {
      return _roles.iterator();
   }

}

Code:

# Host: localhost
# Database: authority
# Table: 'roles'
# 
CREATE TABLE `roles` (
  `rolename` varchar(20) NOT NULL default '',
  PRIMARY KEY  (`rolename`)
) TYPE=MyISAM; 

# Host: localhost
# Database: authority
# Table: 'user_roles'
# 
CREATE TABLE `user_roles` (
  `username` varchar(20) NOT NULL default '',
  `rolename` varchar(20) NOT NULL default '',
  PRIMARY KEY  (`username`,`rolename`)
) TYPE=MyISAM; 

# Host: localhost
# Database: authority
# Table: 'users'
# 
CREATE TABLE `users` (
  `username` varchar(20) NOT NULL default '',
  `password` varchar(20) NOT NULL default '',
  PRIMARY KEY  (`username`)
) TYPE=MyISAM; 

Code:

<hibernate-mapping>

   <class name="UserBean" table="users">
      <id name="name" type="string" unsaved-value="null" >
         <column name="username" sql-type="varchar(20)" not-null="true"/>
         <generator class="assigned"/>
      </id>
      <property name="password">
         <column name="password" sql-type="varchar(20)" not-null="true"/>
      </property>
      <set name="roles" lazy="false" table="user_roles" cascade="all">
         <key column="username"/>
         <one-to-many column_id="username" class="com.tyson.struts.beans.UserRoleBean"/>
      </set>
   </class>

   <class name="RoleBean" table="roles">
      <id name="name" type="string" unsaved-value="null" >
         <column name="rolename" sql-type="varchar(20)" not-null="true"/>
         <generator class="assigned"/>
      </id>
   </class>

   <class name="UserRoleBean" table="user_roles">
      <id name="user" type="string" unsaved-value="null">
         <column name="username" sql-type="varchar(20)" not-null="true"/>
         <generator class="assigned"/>
      </id>
      <property name="role">
         <column name="rolename" sql-type="varchar(20)" not-null="true"/>
      </property>
   </class>
</hibernate-mapping>

cutie · **Posted:** Thu Nov 06, 2003 1:59 pm

you need a many-to-many relationship if you use a join table

parkerjo · **Joined:** Thu Nov 06, 2003 12:38 pm **Posts:** 3

Hmm. Sorry, but the many-to-many doesn't work. I just get a bunch of errors that I really didn't want to track down and it isn't the correct relational mapping anyway.

I finally got it to work (sort of) by adding multiple <id> tags in the UserRoleBean class. However, when I listed <id name="userName"...> first it doesn't get set by reflection. Conversely, if I switch the two and put <id name="roleName"...> first, then the roleName doesn't get set in the object. :(

Code:

   <class name="UserRoleBean" table="user_roles">
      <id name="userName" type="string" unsaved-value="null">
         <column name="username" sql-type="varchar(20)" not-null="true"/>
         <generator class="assigned"/>
         <many-to-one name="username" class="com.tyson.struts.beans.UserBean"/>
      </id>
      <id name="roleName" type="string" unsaved-value="null">
         <column name="rolename" sql-type="varchar(20)" not-null="true"/>
         <generator class="assigned"/>
         <many-to-one name="rolename" class="com.tyson.struts.beans.RoleBean"/>
      </id>
   </class>

Being adventurous I added the entry below for the UserRoleBean and now the userName gets set! :S

Code:

      <property name="userName">
         <column name="username" sql-type="varchar(20)" not-null="true" update="false" insert="false"/>
      </property>

It couldn't be that easy though. With this configuraton I can see users and the roles assigned to them. But, I can't see the users assigned to roles. For instance, I have 4 roles (owner, manager, waitress, cook) and some users (joe, bob, jane). The database is set up as... Joe is the owner and a cook. All users are cooks.

If I ask for all users assigned to the role 'cook' the result is:

Code:

User   Role
joe   cook
joe   cook
joe   cook

But if I ask for roles for user 'joe' the result is:

Code:

User   Role
joe   cook
joe   owner

Does Hibernate support multiple <id> tags in a <class> definition? I couldn't get a clear understanding from the documentation. If it does, am I doing it correctly? -John

emmanuel · **Posted:** Thu Nov 06, 2003 8:15 pm

Lot's of problems here:
* Not multiple id allowed
* no need to <set table="blah"> in a one-to-many since Hibernate can gess it from the one-to-many class attribute.
* no many-to-one inside id tag
* ...

Listen to cutie, Many-to-many IS what you want

Try someting like that

Code:

<class name="UserBean" table="users">
  ...
  <set name="roles" lazy="false" table="user_roles" cascade="all">
         <key column="username"/>
         <many-to-many column="rolename" class="com.tyson.struts.beans.RoleBean"/>
   </set>
   

And read section 5.3 of the reference guide

parkerjo · **Joined:** Thu Nov 06, 2003 12:38 pm **Posts:** 3

I read the entire online documentation. Is there more? I ask because section 5.3 of the online reference doesn't say much in *newbie* talk. For experts it might say a lot but all I see are examples with "one-liners". Its not much help.
I'll add the many-to-many relationship and post the errors it generates. Is there an online help for errors Hibernate generates?

-john

emmanuel · **Posted:** Fri Nov 07, 2003 5:47 am

I can undersand that Hibernate doc may be very obscure for newbies because it assumes you're aware of O/R concepts, but /almost/ everything is in (I know nothing on O/R concepts but the one I learned from it - I read and read it again ;-)).

You can have a look at
http://www.hibernate.org/Documentation/ExternalDocumentation, it points to some good tutorials and samples (I like Scott Ambler's article).