MappingException: Unknown entity class: java.lang.String

karanmg · **Posted:** Sun Dec 26, 2004 1:33 pm

Hi everyone.
I'm a beginner, and am trying out a very simple program to understand the concepts. There's Users class, which has "username" and "pswd" columns. A UserRights table has a username column which references username in Users and a userrights column which is an integer holding a numeric value. The UserRights table also has a surrogate primary key column. I am able to retreive records from the UserRights table, but I am not able to insert any records into the UserRights table.

I keep getting a
net.sf.hibernate.MappingException: Unknown entity class: java.lang.String
error.

Any help is greatly appreciated.

Hibernate version: 2.1.7

Mapping documents:
Users.hbm.xml:

Code:

<hibernate-mapping>
    <class name="okay.hbvo.Users" table="users">
   <id name="username" type="java.lang.String">
           <generator class="assigned"/>
        </id>
        <property name="pswd" type="java.lang.String"/>
    </class>
</hibernate-mapping>

UserRight.hbm.xml:

Code:

<hibernate-mapping>
    <class name="okay.hbvo.UserRight" table="userright">
        <id name="surrpk" type="java.lang.Integer" unsaved-value="0">
           <generator class="increment"/>
        </id>
        <many-to-one name="username" class="okay.hbvo.Users" column="username" unique="true"/>
        <property name="userRights" type="java.lang.Long"/>
    </class>
</hibernate-mapping>

Code between sessionFactory.openSession() and session.close():
getting the DAO:
UserRightDAO urdao = DAOFactory.getUserRightDAO();
Long uright = new Long((long)12345);
String urname = new String("karan"); // this user exists in Users table
UserRight uro = new UserRight(urname, uright);
urdao.insertUR(uro);
MainUserRightDAO's insertUR function (takes a UserRight object as parameter):
HibernateUtil.beginTransaction();
Session session = HibernateUtil.getSession();
session.save(URo);
HibernateUtil.commitTransaction();
HibernateUtil.closeSession();

Full stack trace of any exception that occurs:
2004-12-26 10:57:33,548 [main] DEBUG okay.dao.HibernateUtil - ****************** SESSIONFACTORY MADE ******************
2004-12-26 10:57:33,549 [main] DEBUG okay.dao.HibernateUtil - Starting new database transaction in this thread.
2004-12-26 10:57:33,550 [main] DEBUG okay.dao.HibernateUtil - Opening new Session for this thread.
2004-12-26 10:57:33,934 [main] DEBUG net.sf.hibernate.impl.SessionImpl - opened session
2004-12-26 10:57:33,940 [main] DEBUG net.sf.hibernate.transaction.JDBCTransaction - begin
2004-12-26 10:57:33,942 [main] DEBUG net.sf.hibernate.connection.DriverManagerConnectionProvider - total checked-out connections: 0
2004-12-26 10:57:33,944 [main] DEBUG net.sf.hibernate.connection.DriverManagerConnectionProvider - using pooled JDBC connection, pool size: 0
2004-12-26 10:57:33,945 [main] DEBUG net.sf.hibernate.transaction.JDBCTransaction - current autocommit status:false
2004-12-26 10:57:33,950 [main] DEBUG net.sf.hibernate.id.IncrementGenerator - fetching initial value: select max(surrpk) from userright
2004-12-26 10:57:33,960 [main] DEBUG net.sf.hibernate.id.IncrementGenerator - first free id: 1
2004-12-26 10:57:33,962 [main] DEBUG net.sf.hibernate.impl.SessionImpl - generated identifier: 1
2004-12-26 10:57:33,967 [main] DEBUG net.sf.hibernate.impl.SessionImpl - saving [okay.hbvo.UserRight#1]
######### Exception in insertUR ############
2004-12-26 10:57:34,143 [main] DEBUG okay.dao.HibernateUtil - Tyring to rollback database transaction of this thread.
2004-12-26 10:57:34,145 [main] DEBUG net.sf.hibernate.transaction.JDBCTransaction - rollback
2004-12-26 10:57:34,147 [main] DEBUG net.sf.hibernate.impl.SessionImpl - transaction completion
2004-12-26 10:57:34,148 [main] DEBUG okay.dao.HibernateUtil - Closing Session of this thread.
2004-12-26 10:57:34,149 [main] DEBUG net.sf.hibernate.impl.SessionImpl - closing session
2004-12-26 10:57:34,150 [main] DEBUG net.sf.hibernate.impl.SessionImpl - disconnecting session
2004-12-26 10:57:34,155 [main] DEBUG net.sf.hibernate.connection.DriverManagerConnectionProvider - returning connection to pool, pool size: 1
2004-12-26 10:57:34,157 [main] DEBUG net.sf.hibernate.impl.SessionImpl - transaction completion
net.sf.hibernate.MappingException: Unknown entity class: java.lang.String
net.sf.hibernate.MappingException: Unknown entity class: java.lang.String
at net.sf.hibernate.impl.SessionFactoryImpl.getPersister(SessionFactoryImpl.java:346)
at net.sf.hibernate.impl.SessionImpl.getClassPersister(SessionImpl.java:2694)
at net.sf.hibernate.impl.SessionImpl.getPersister(SessionImpl.java:2701)
at net.sf.hibernate.impl.SessionImpl.isUnsaved(SessionImpl.java:1092)
at net.sf.hibernate.impl.SessionImpl.nullifyTransientReferences(SessionImpl.java:1038)
at net.sf.hibernate.impl.SessionImpl.nullifyTransientReferences(SessionImpl.java:1024)
at net.sf.hibernate.impl.SessionImpl.doSave(SessionImpl.java:928)
at net.sf.hibernate.impl.SessionImpl.doSave(SessionImpl.java:858)
at net.sf.hibernate.impl.SessionImpl.saveWithGeneratedIdentifier(SessionImpl.java:780)
at net.sf.hibernate.impl.SessionImpl.save(SessionImpl.java:739)
at okay.dao.MainUserRightDAO.insertUR(MainUserRightDAO.java:16)
at okay.hibMain.main(hibMain.java:23)
######### Exception in hibMAIN ############
okay.dao.InfrastructureException: net.sf.hibernate.MappingException: Unknown entity class: java.lang.String
okay.dao.InfrastructureException: net.sf.hibernate.MappingException: Unknown entity class: java.lang.String
at okay.dao.MainUserRightDAO.insertUR(MainUserRightDAO.java:27)
at okay.hibMain.main(hibMain.java:23)
Caused by: net.sf.hibernate.MappingException: Unknown entity class: java.lang.String
at net.sf.hibernate.impl.SessionFactoryImpl.getPersister(SessionFactoryImpl.java:346)
at net.sf.hibernate.impl.SessionImpl.getClassPersister(SessionImpl.java:2694)
at net.sf.hibernate.impl.SessionImpl.getPersister(SessionImpl.java:2701)
at net.sf.hibernate.impl.SessionImpl.isUnsaved(SessionImpl.java:1092)
at net.sf.hibernate.impl.SessionImpl.nullifyTransientReferences(SessionImpl.java:1038)
at net.sf.hibernate.impl.SessionImpl.nullifyTransientReferences(SessionImpl.java:1024)
at net.sf.hibernate.impl.SessionImpl.doSave(SessionImpl.java:928)
at net.sf.hibernate.impl.SessionImpl.doSave(SessionImpl.java:858)
at net.sf.hibernate.impl.SessionImpl.saveWithGeneratedIdentifier(SessionImpl.java:780)
at net.sf.hibernate.impl.SessionImpl.save(SessionImpl.java:739)
at okay.dao.MainUserRightDAO.insertUR(MainUserRightDAO.java:16)
... 1 more

Name and version of the database you are using:
PostgreSQL 7.4.2

The generated SQL (show_sql=true):
2004-12-26 10:57:33,950 [main] DEBUG net.sf.hibernate.id.IncrementGenerator - fetching initial value: select max(surrpk) from userright
This is all I see.

Debug level Hibernate log excerpt:
its up there.

max · **Posted:** Sun Dec 26, 2004 4:06 pm

first guess: your username property is mapped to a User but is actually a string on your java class...

karanmg · **Posted:** Mon Jan 03, 2005 12:57 pm

how do i make that change??
i tried a one-to-one mapping, but got the same errors.

karanmg · **Posted:** Mon Jan 03, 2005 1:16 pm

here's some more msgs when hibernate is making the mapping:

10:43:33,339 INFO Environment:528 - using java.io streams to persist binary types
10:43:33,341 INFO Environment:529 - using CGLIB reflection optimizer
10:43:33,493 INFO Configuration:331 - Mapping resource: okay/hbvo/Users.hbm.xml
10:43:34,874 DEBUG DTDEntityResolver:20 - trying to locate http://hibernate.sourceforge.net/hibern ... ng-2.0.dtd in classpath under net/sf/hibernate/
10:43:34,879 DEBUG DTDEntityResolver:29 - found http://hibernate.sourceforge.net/hibern ... ng-2.0.dtd in classpath
10:43:35,530 INFO Binder:229 - Mapping class: okay.hbvo.Users -> users
10:43:35,897 DEBUG Binder:486 - Mapped property: username -> username, type: string
10:43:36,062 DEBUG Binder:486 - Mapped property: pswd -> pswd, type: string
10:43:36,067 INFO Configuration:331 - Mapping resource: okay/hbvo/UserRight.hbm.xml
10:43:36,226 DEBUG DTDEntityResolver:20 - trying to locate http://hibernate.sourceforge.net/hibern ... ng-2.0.dtd in classpath under net/sf/hibernate/
10:43:36,240 DEBUG DTDEntityResolver:29 - found http://hibernate.sourceforge.net/hibern ... ng-2.0.dtd in classpath
10:43:36,525 INFO Binder:229 - Mapping class: okay.hbvo.UserRight -> userright
10:43:36,528 DEBUG Binder:486 - Mapped property: surrpk -> surrpk, type: integer
10:43:36,717 DEBUG Binder:486 - Mapped property: username, type: okay.hbvo.Users
10:43:36,719 DEBUG Binder:486 - Mapped property: userRights -> userRights, type: long

So, "username" is of type string in the Users class, but username is also a FK in the UserRight class, so it must be of type okay.hbvo.Users. That is the difference between the two, whereas both of them must be of the same type. How do I map this correctly?

max · **Posted:** Mon Jan 03, 2005 1:17 pm

please read the basic hibernate tutorials - it's covered there.

karanmg · **Posted:** Mon Jan 03, 2005 4:45 pm

I'm sorry, I've not been able to get a solution to this problem.
I've read the FAQs, the tutorial at systemmobile, the online reference and the book.
Maybe I'm not reading it right.

I don't want an inverse relationship between the tables. I am just looking for a simple FK refernce in my mapping from the UserRight class to the Users class. I can update, insert, whatever on the Users class right now, and I can retreive data from the UserRights table. However, I cannot insert into the UserRights table -- I keep getting the same error. AFAIK, I have to give this statement to show a FK reference in my mapping:
<code><many-to-one name="username" class="okay.hbvo.Users" column="username"/></code>
in UserRight.hbm.xml.

This should tell hibernate that the "username" column in Users class is being referenced here. I have tried changing this statement but I keep getting the same error. What am I doing wrong?

Thanks for any help.

max · **Posted:** Mon Jan 03, 2005 5:12 pm

and how does your corresponding property field/methods look like ?

karanmg · **Posted:** Mon Jan 03, 2005 6:10 pm

Code:

      UserRightDAO urdao = DAOFactory.getUserRightDAO();
      UserRight uro = new UserRight("kmg", new Long("567"));
      urdao.insertUR(uro);

Code in the DAO:

Code:

      HibernateUtil.beginTransaction();
      Session session = HibernateUtil.getSession();
      session.save(URo);
      HibernateUtil.commitTransaction();
      HibernateUtil.closeSession();

Persistent Class for UserRight:

Code:

package okay.hbvo;
import java.io.Serializable;

public class UserRight implements Serializable
{
    private Integer surrpk = null;
    private String  username;
    private Long    userRights;
    
    public UserRight()
    {}

    public UserRight(String username, Long userRights)
    {
   this.username = username;
   this.userRights = userRights;
    }

    public Integer getSurrpk()
    {   return surrpk;    }

    public void setSurrpk(Integer surrpk)
    {   this.surrpk = surrpk;    }

    public String getUsername()
    {   return username;    }

    public void setUsername(String username)
    {   this.username = username;    }

    public Long getUserRights()
    {   return userRights;    }

    public void setUserRights(Long userRights)
    {   this.userRights = userRights;    }
}

The Database Schema:

Code:

CREATE TABLE Users
   (
      username   varchar(20)   PRIMARY KEY, 
      pswd      varchar(20)
   );

CREATE TABLE UserRight
   (
                surrpk          integer         PRIMARY KEY,
      username   varchar(20)   UNIQUE REFERENCES Users(username),
      userRights   integer
   );

Thank you.

max · **Posted:** Tue Jan 04, 2005 3:37 am

ok - as I thought - you are mapping a String property to a User property, that is not the right way to go. You should have a User property mapped to a User property!

The String is just in the database and probably a key in your User object - UserRight should point to a User, not a String....

...and this is EVERYWHERE in all examples that concerns simple associations....

karanmg · **Posted:** Tue Jan 04, 2005 1:15 pm

Thanks for your replies max.

In the database:
Users has a username and a pswd column.
UserRight has surrpk, username, and userright columns.
And UserRight(username) references Users(username).

So username IS a string in both Users and UserRights. The current code is what I've picked up and written from whatever I have read. I don't need the entire Users object in UserRights, so the current implementation is probably not the right way to go. I could make a persistent Users object in my UserRights class and work that way, but that is not what I require.

I've been looking at the mapping example on pg 221 of the book. In section "Using a Foreign Key Association", it shows that to map a billingAddress to a User, we have to use a FK column. In my case there is only one column, the username, whcih is common to both the tables. So I dont want to put in an extra FK_ID column.

Am I even thinking this right? The database will make sure that consistency is maintained, so I want to know if I even need to do a many-to-one in my code. Because what I am looking for right now is a real simple FK mapping, which will translate to the following: if I delete a user in Users, it must delete the corresponding row in UserRights. I know I can use inverse mapping with cascading for this, but I am still confused about using the User object UserRights. This is a conceptual problem, for which I would really appreciate your guidance.

max · **Posted:** Tue Jan 04, 2005 1:35 pm

They are a string in the database TABLE.

In the UserRight java CLASS they should be a concrete User if you want to map with Hibernate.

The String user in UserRight class is not needed for Hibernate.