JPA Table 生成问题

Question

我在使用 JPA 时遇到问题。当我尝试保留一个新实体时，我会收到以下错误：

java.lang.IllegalArgumentException: Object: Technology is not a known entity type.

技术是类别的标题class。（注意：我的代码之前已经成功了！）所以我决定删除数据库中的所有表 (PostgreSql)

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(以前也有过这个错误，过一段时间就消失了)
javax.persistence.PersistenceException：异常 [EclipseLink-4002]（Eclipse 持久性服务 - 2.5.2.v20140319-9ad6abd）：org.eclipse.persistence.exceptions.DatabaseException 内部异常：org.postgresql.util.PSQLException：错误：关系 "category" 不存在位置：47 错误代码：0 调用：SELECT ID、DESCRIPTION、TITLE，PARENT_ID FROM category 查询：ReadAllQuery(referenceClass=Category sql="SELECT ID, DESCRIPTION, TITLE, PARENT_ID FROM category")

实体class (Category.Java)

@Entity
public class Category implements DataObject, Serializable {

@Id
@GeneratedValue 
private Long id;
private String title;
private String description;

@ManyToOne @JsonIgnore 
private Category parent;

@Transient
private Long parentId;
//functions
}

persistence.xml

  <persistence-unit name="BloggerPU" transaction-type="JTA">
    <provider>org.eclipse.persistence.jpa.PersistenceProvider</provider>
    <jta-data-source>blogdb</jta-data-source>
    <class>domain.Blog</class>
    <class>domain.BlogUser</class>
    <class>domain.Category</class>
    <exclude-unlisted-classes>true</exclude-unlisted-classes>
    <properties>
      <property name="javax.persistence.schema-generation.database.action" value="drop-and-create"/>
    </properties>
  </persistence-unit>

编辑

我通过重新启动 glassfish 服务器解决了关系错误。现在我回到了第一个错误。

DatabaseJPA.java

public class DatabaseJPA<T extends DataObject> implements Database<T> {

private EntityManagerFactory factory;
private EntityManager manager;
private Class<T> type;

public DatabaseJPA(String name, Class<T> type)
{
      factory = Persistence.createEntityManagerFactory(name);
      manager = factory.createEntityManager();
      this.type = type;
}
@Override
public T ReadValue(long id) {

   return (T) manager.find(type, id);
}

@Override
public void InsertValue(T value) {


    manager.getTransaction().begin();

    manager.persist(value);

    manager.flush();
    manager.getTransaction().commit();

}

@Override
public void UpdateValue(long id, T value) {
    manager.getTransaction().begin();
    manager.merge(value);
    manager.flush();
    manager.getTransaction().commit();
}


@Override
public void DeleteValue(long id) {
    manager.getTransaction().begin();
    manager.remove(this.ReadValue(id));
    manager.flush();
    manager.getTransaction().commit();
}

@Override
public void close() throws IOException {
    factory.close();
    manager.close();
}
}

Answer 1

如果你又遇到关系问题：

@ManyToOne
private A parent;
@OneToMany(mappedBy="parent")
private Collection<A> children;

对于 IllegalArgumentException，您能否向我们展示您调用 persist 并引发异常的部分代码？

Answer 2

在 persistence.xml 中将 transaction-type 更改为 LOCAL_RESOURCE 解决了问题并重新启动了 glassfish 服务器。

JPA Table 生成问题

JPA Table generation problems

java

hibernate

postgresql

jpa

eclipselink