ObjectDB：持久性異常類型未找到錯誤301

Question

而下面這個教程：

http://www.objectdb.com/tutorial/jpa/eclipse

我收到以下錯誤：

Exception in thread "main" [ObjectDB 2.5.4_05] javax.persistence.PersistenceException 
Type tutorial.model.Point is not found (error 301) 
at com.objectdb.jpa.EMImpl.persist(EMImpl.java:437) 
at objectdb.tutorial.main.Main.main(Main.java:25) 
Caused by: com.objectdb.o.TEX: Type tutorial.model.Point is not found 
at com.objectdb.o.MSG.e(MSG.java:107) 
at com.objectdb.o.TYM.ay(TYM.java:1017) 
at com.objectdb.o.TYM.ap(TYM.java:807) 
at com.objectdb.o.TYM.ao(TYM.java:757) 
at com.objectdb.o.TYM.at(TYM.java:873) 
at com.objectdb.o.TYM.aw(TYM.java:945) 
at com.objectdb.o.OBM.bB(OBM.java:371) 
at com.objectdb.o.OBM.bB(OBM.java:257) 
at com.objectdb.jpa.EMImpl.persist(EMImpl.java:434) 
... 1 more 
Caused by: java.lang.ClassNotFoundException: tutorial.model.Point 
at com.objectdb.o.TYM.findClass(TYM.java:1033) 
at com.objectdb.o.ACL.loadClass(ACL.java:131) 
at java.lang.ClassLoader.loadClass(ClassLoader.java:247) 
at com.objectdb.o.TYM.ay(TYM.java:1013) 
... 8 more` 

我看了這個帖子（Problems searching empty user database with ObjectDB），但由於某種原因，我的EntityManager實例沒有成員函數getMetamodel（）。所以，我試圖創建我自己的持久性單元，我在下面用我的代碼。我仍然收到第一個for循環中em.persist（p）出現的運行時錯誤。

package objectdb.tutorial.main; 

import javax.persistence.*; 

import objectdb.tutorial.model.Point; 

import java.util.*; 

public class Main { 
    public static void main(String[] args) { 
     // Open a database connection 
     // (create a new database if it doesn't exist yet): 
     EntityManagerFactory emf = 
      Persistence.createEntityManagerFactory("my-pu"); 
     EntityManager em = emf.createEntityManager(); 


     // Store 1000 Point objects in the database: 
     em.getTransaction().begin(); 
     for (int i = 0; i < 1000; i++) { 
      Point p = new Point(i, i); 
      em.persist(p); 
     } 
     em.getTransaction().commit(); 

     // Find the number of Point objects in the database: 
     Query q1 = em.createQuery("SELECT COUNT(p) FROM Point p"); 
     System.out.println("Total Points: " + q1.getSingleResult()); 

     // Find the average X value: 
     Query q2 = em.createQuery("SELECT AVG(p.x) FROM Point p"); 
     System.out.println("Average X: " + q2.getSingleResult()); 

     // Retrieve all the Point objects from the database: 
     Query query = 
      em.createQuery("SELECT p FROM Point p"); 
     List<Point> results = query.getResultList(); 
     for (Point p : results) { 
      System.out.println(p); 
     } 

     // Close the database connection: 
     em.close(); 
     emf.close(); 
    } 
} 

實體：

package objectdb.tutorial.model; 

import java.io.Serializable; 
import javax.persistence.*; 

@Entity 
public class Point implements Serializable { 
    private static final long serialVersionUID = 1L; 

    @Id @GeneratedValue 
    private long id; 

    private int x; 
    private int y; 

    public Point() { 
    } 

    public Point(int x, int y) { 
     this.x = x; 
     this.y = y; 
    } 

    public Long getId() { 
     return id; 
    } 

    public int getX() { 
     return x; 
    } 

    public int getY() { 
     return y; 
    } 

    @Override 
    public String toString() { 
     return String.format("(%d, %d)", this.x, this.y); 
    } 
} 

的persistence.xml：

<?xml version="1.0" encoding="UTF-8" ?> 
<persistence 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" version="1.0"> 

    <persistence-unit name="my-pu"> 
    <description>My Persistence Unit</description> 
    <provider>com.objectdb.jpa.Provider</provider> 
    <!-- <mapping-file>META-INF/mappingFile.xml</mapping-file> Not sure what this is--> 
    <class>objectdb.tutorial.model.Point</class> 
    <properties> 
     <property name="javax.persistence.jdbc.url" 
       value="objectdb://localhost/tutorial.odb"/> 
     <property name="javax.persistence.jdbc.user" value="admin"/> 
     <property name="javax.persistence.jdbc.password" value="admin"/> 

    </properties> 
    </persistence-unit> 

</persistence> 

我明白任何建議。謝謝。

Answer 1

錯誤消息：「找不到類型tutorial.model.Point」指定包tutorial.model中的Point類。你的包名是objectdb.tutorial.model。可能以前你有過這個包名，但是你把你的包移到了新的位置和名字。

嘗試刪除數據庫文件，因爲它仍然包含以前名稱中的類（或者如果您需要數據，請按照關於schema change的ObjectDB網站上的說明進行操作）。

如果您沒有getMetamodel方法，那麼在ObjectDB（其中包含JPA 2.1 jar）之前，您的類路徑中可能會有一箇舊的JPA 1.0 jar包。您必須修復您的類路徑以避免其他問題。