Stefan Kendall Stefan Kendall - 2 months ago 13
Java Question

org.hibernate.MappingException: Unknown entity

I'm trying to work through Beginning Hibernate 2nd edition, and I'm stuck trying to put together the simple working example with HSQLDB.

When I run

ant populateMessages
, I get

[java] org.hibernate.MappingException: Unknown entity: sample.entity.Message
[java] at org.apache.tools.ant.taskdefs.ExecuteJava.execute(ExecuteJava.java:194)
[java] at org.apache.tools.ant.taskdefs.Java.run(Java.java:747)
...


Here's what I've got:

Message.java

package sample.entity;

import org.hibernate.annotations.Entity;

import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.Table;

@Entity
public class Message
{
private String messageText;
private Integer id;

public Message( String messageText )
{
this.messageText = messageText;
}

public Message()
{
}

public String getMessageText()
{
return messageText;
}

public void setMessageText(String messageText)
{
this.messageText = messageText;
}

@Id
@GeneratedValue
public Integer getId()
{
return id;
}

public void setId(Integer id)
{
this.id = id;
}
}


PopulateMessages.java

package sample;

import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.cfg.AnnotationConfiguration;
import org.hibernate.cfg.Configuration;
import sample.entity.Message;

import java.util.Date;

public class PopulateMessages
{
public static void main(String[] args)
{
SessionFactory factory = new AnnotationConfiguration().configure().buildSessionFactory();
Session session = factory.openSession();
session.beginTransaction();

Message m1 = new Message("Hibernated a messages on " + new Date());
session.save(m1);
session.getTransaction().commit();
session.close();
}
}


build.properties

# Path to the hibernate install directory
hibernate.home=C:/hibernate/hibernate-3.5.6
# Path to the hibernate-tools install directory
hibernate.tools.home=C:/hibernate/hibernate-tools
# Path to hibernate-tools.jar relative to hibernate.tools.home
hibernate.tools.path=/plugins/org.hibernate.eclipse_3.3.1.v201006011046R-H111-GA/lib/tools
# Path to hibernate-tools hibernate libraries relative to hibernate.tools.home
hibernate.tools.lib.path=/plugins/org.hibernate.eclipse_3.3.1.v201006011046R-H111-GA/lib/hibernate
# Path to the SLF4J implementation JAR for the logging framework to use
slf4j.implementation.jar=lib/slf4j-simple-1.6.1.jar
# Path to the HSQL DB install directory
hsql.home=C:/hsqldb


hibernate.cfg.xml

<!DOCTYPE hibernate-configuration PUBLIC
"-//Hibernate/Hibernate Configuration DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-configuration-3.0.dtd">
<hibernate-configuration>
<session-factory>
<property name="hibernate.connection.url">
jdbc:hsqldb:file:testdb;shutdown=true
</property>
<property name="hibernate.connection.driver_class">
org.hsqldb.jdbcDriver
</property>
<property name="hibernate.connection.username">sa</property>
<property name="hibernate.connection.password"></property>
<property name="hibernate.connection.pool_size">0</property>
<property name="hibernate.dialect">
org.hibernate.dialect.HSQLDialect
</property>
<property name="hibernate.show_sql">false</property>
<!-- "Import" the mapping resources here -->
<mapping class="sample.entity.Message"/>
</session-factory>
</hibernate-configuration>


build.xml

<project name="sample">
<property file="build.properties"/>
<property name="src" location="src"/>
<property name="bin" location="bin"/>
<property name="sql" location="sql"/>
<property name="hibernate.tools"
value="${hibernate.tools.home}${hibernate.tools.path}"/>
<path id="classpath.base">
<pathelement location="${src}"/>
<pathelement location="${bin}"/>
<pathelement location="${hibernate.home}/hibernate3.jar"/>
<pathelement location="${slf4j.implementation.jar}"/>
<fileset dir="${hibernate.home}/lib" includes="**/*.jar"/>
<pathelement location="${hsql.home}/lib/hsqldb.jar"/>
<fileset dir="./lib" includes="**/*.jar"/>
</path>
<path id="classpath.tools">
<path refid="classpath.base"/>
<pathelement
location="${hibernate.tools.home}/${hibernate.tools.lib.path}/commons-logging-1.0.4.jar"/>
<pathelement
location="${hibernate.tools}/freemarker.jar"/>
<pathelement
location="${hibernate.tools}/hibernate-tools.jar"/>
</path>
<taskdef name="htools"
classname="org.hibernate.tool.ant.HibernateToolTask"
classpathref="classpath.tools"/>
<target name="exportDDL" depends="compile">
<mkdir dir="${sql}"/>
<htools destdir="${sql}">
<classpath refid="classpath.tools"/>
<annotationconfiguration
configurationfile="${src}/hibernate.cfg.xml"/>
<hbm2ddl drop="true" outputfilename="sample.sql"/>
</htools>
</target>
<target name="compile">
<javac srcdir="${src}" destdir="${bin}" classpathref="classpath.base"/>
</target>
<target name="populateMessages" depends="compile">
<java classname="sample.PopulateMessages" classpathref="classpath.base"/>
</target>
<target name="listMessages" depends="compile">
<java classname="sample.ListMessages" classpathref="classpath.base"/>
</target>



Answer

You entity is not correctly annotated, you must use the @javax.persistence.Entity annotation. You can use the Hibernate extension @org.hibernate.annotations.Entity to go beyond what JPA has to offer but the Hibernate annotation is not a replacement, it's a complement.

So change your code into:

import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.Table;

@Entity
public class Message { 
    ...  
}

References