Netbeans + MySQL + Tomcat (problem with: not a known entity type)

Question

I try to create WebApplication with Stripes in netbeans, but I have problem with connect to DB.
I have this code:
EntityManagerFactory emf = Persistence.createEntityManagerFactory("jpaPU");
EntityManager em = emf.createEntityManager();
em.getTransaction().begin();
Person p = new Person();
p.setFirstName("name1");
p.setLastName("name2");
try
em.persist(p);
} catch(Exception e)
System.out.println(e.toString());
em.getTransaction().commit();
em.close();
emf.close();But in try{..} is em.persist(p); ant it prints into console this error: "java.lang.IllegalArgumentException: Object: db_entity.Person@13c7c35 is not a known entity type."
I do not know where is problem. Could you help me, please?
This is my persistence.xml:
<?xml version="1.0" encoding="UTF-8"?>
<persistence version="1.0" xmlns="http://java.sun.com/xml/ns/persistence" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/persistence http://java.sun.com/xml/ns/persistence/persistence_1_0.xsd">
  <persistence-unit name="jpaPU" transaction-type="RESOURCE_LOCAL">
    <provider>oracle.toplink.essentials.PersistenceProvider</provider>
    <properties>
      <property name="toplink.jdbc.user" value="root"/>
      <property name="toplink.jdbc.password" value="adminadmin"/>
      <property name="toplink.jdbc.url" value="jdbc:mysql://localhost:3306/test"/>
      <property name="toplink.jdbc.driver" value="com.mysql.jdbc.Driver"/>
      <property name="toplink.ddl-generation" value="create-tables"/>
    </properties>
  </persistence-unit>
</persistence>When I run my application I can see in console:
[TopLink Info]: 2008.11.15 09:01:13.265--ServerSession(4794542)--TopLink, version: Oracle TopLink Essentials - 2.0.1 (Build b09d-fcs (12/06/2007))
[TopLink Info]: 2008.11.15 09:01:13.578--ServerSession(4794542)--file:/D:/Workspace/NetBeansProjects/jpa/build/web/WEB-INF/classes/-jpaPU login successful..so, I hope persistence.xml is good
This is my class Person.java:
@Entity
public class Person implements Serializable {
    @Id
    @GeneratedValue
    private Long id;
    private String firstName;
    private String lastName;
    public void setId(Long id) { this.id = id; }
    public Long getId() { return id; }
    public String getFirstName() {  return firstName; }
    public void setFirstName(String firstName) { this.firstName = firstName;  }
    public String getLastName() { return lastName; }
    public void setLastName(String lastName) { this.lastName = lastName;  }Please, help me.

Answer 1

I had the same "is not a known entity type" error when running under a development environment Eclipse/Tomcat using Toplink. But the almost same code and configuration worked when running under Eclipse as a stand-alone Java app.
Eventually I figured out (actually trial and error), that I had checked the toplink-essentials.jar libraries to be exported under: Eclipse Project/Java Build Path/Order and Export. I was messing around with libraries. Unchecking the export option there fixed the problem.
While its unlikely that this could have been your exact problem, I would check the library order and export configurations. Looking at other message boards about this problem, many seemed to have been caused or fixed by playing with their libraries.