【发布时间】：2013-10-10 12:57:15
【问题描述】：
我有一个非常简单的 eclipse 链接案例，我在下面复制了它。如果我可以让下面的示例正常工作，那么我可以轻松地将它应用到有问题的实际案例中。问题是，我不能！
有两个类 - Parent 和 Child。两者都有String id，Parent 包含Child 字段children 中的对象列表。孩子的List 具有@OneToMany 属性，并且两个类都具有@Entity 属性。我通过 Eclipse 作为 Maven 项目运行所有内容，persistence.xml 存储在src\main\resources\META_INF\persistence.xml 中。没有引用其他 jars。
当我调用Persistence.createEntityManagerFactory 时，我得到以下异常。好像认为Child不是实体！
Exception in thread "main" Local Exception Stack:
Exception [EclipseLink-30005] (Eclipse Persistence Services - 2.5.0.v20130507-3faac2b): org.eclipse.persistence.exceptions.PersistenceUnitLoadingException
Exception Description: An exception was thrown while searching for persistence archives with ClassLoader: sun.misc.Launcher$AppClassLoader@1a8e3115
Internal Exception: javax.persistence.PersistenceException: Exception [EclipseLink-28018] (Eclipse Persistence Services - 2.5.0.v20130507-3faac2b): org.eclipse.persistence.exceptions.EntityManagerSetupException
Exception Description: Predeployment of PersistenceUnit [Parent] failed.
Internal Exception: Exception [EclipseLink-7250] (Eclipse Persistence Services - 2.5.0.v20130507-3faac2b): org.eclipse.persistence.exceptions.ValidationException
Exception Description: [class com.test.Parent] uses a non-entity [class com.test.Child] as target entity in the relationship attribute [field children].
at org.eclipse.persistence.exceptions.PersistenceUnitLoadingException.exceptionSearchingForPersistenceResources(PersistenceUnitLoadingException.java:127)
at org.eclipse.persistence.jpa.PersistenceProvider.createEntityManagerFactoryImpl(PersistenceProvider.java:107)
at org.eclipse.persistence.jpa.PersistenceProvider.createEntityManagerFactory(PersistenceProvider.java:177)
at javax.persistence.Persistence.createEntityManagerFactory(Persistence.java:79)
at com.test.Main.main(Main.java:22)
Caused by: javax.persistence.PersistenceException: Exception [EclipseLink-28018] (Eclipse Persistence Services - 2.5.0.v20130507-3faac2b): org.eclipse.persistence.exceptions.EntityManagerSetupException
Exception Description: Predeployment of PersistenceUnit [Parent] failed.
Internal Exception: Exception [EclipseLink-7250] (Eclipse Persistence Services - 2.5.0.v20130507-3faac2b): org.eclipse.persistence.exceptions.ValidationException
Exception Description: [class com.test.Parent] uses a non-entity [class com.test.Child] as target entity in the relationship attribute [field children].
at org.eclipse.persistence.internal.jpa.EntityManagerSetupImpl.createPredeployFailedPersistenceException(EntityManagerSetupImpl.java:1950)
at org.eclipse.persistence.internal.jpa.EntityManagerSetupImpl.predeploy(EntityManagerSetupImpl.java:1941)
at org.eclipse.persistence.internal.jpa.deployment.JPAInitializer.callPredeploy(JPAInitializer.java:98)
at org.eclipse.persistence.jpa.PersistenceProvider.createEntityManagerFactoryImpl(PersistenceProvider.java:96)
... 3 more
Caused by: Exception [EclipseLink-28018] (Eclipse Persistence Services - 2.5.0.v20130507-3faac2b): org.eclipse.persistence.exceptions.EntityManagerSetupException
Exception Description: Predeployment of PersistenceUnit [Parent] failed.
Internal Exception: Exception [EclipseLink-7250] (Eclipse Persistence Services - 2.5.0.v20130507-3faac2b): org.eclipse.persistence.exceptions.ValidationException
Exception Description: [class com.test.Parent] uses a non-entity [class com.test.Child] as target entity in the relationship attribute [field children].
at org.eclipse.persistence.exceptions.EntityManagerSetupException.predeployFailed(EntityManagerSetupException.java:230)
... 7 more
Caused by: Exception [EclipseLink-7250] (Eclipse Persistence Services - 2.5.0.v20130507-3faac2b): org.eclipse.persistence.exceptions.ValidationException
Exception Description: [class com.test.Parent] uses a non-entity [class com.test.Child] as target entity in the relationship attribute [field children].
at org.eclipse.persistence.exceptions.ValidationException.nonEntityTargetInRelationship(ValidationException.java:1378)
at org.eclipse.persistence.internal.jpa.metadata.accessors.mappings.RelationshipAccessor.getReferenceDescriptor(RelationshipAccessor.java:568)
at org.eclipse.persistence.internal.jpa.metadata.accessors.mappings.RelationshipAccessor.processJoinTable(RelationshipAccessor.java:725)
at org.eclipse.persistence.internal.jpa.metadata.accessors.mappings.OneToManyAccessor.processManyToManyMapping(OneToManyAccessor.java:198)
at org.eclipse.persistence.internal.jpa.metadata.accessors.mappings.OneToManyAccessor.process(OneToManyAccessor.java:147)
at org.eclipse.persistence.internal.jpa.metadata.MetadataProject.processOwningRelationshipAccessors(MetadataProject.java:1578)
at org.eclipse.persistence.internal.jpa.metadata.MetadataProject.processStage3(MetadataProject.java:1831)
at org.eclipse.persistence.internal.jpa.metadata.MetadataProcessor.processORMMetadata(MetadataProcessor.java:580)
at org.eclipse.persistence.internal.jpa.deployment.PersistenceUnitProcessor.processORMetadata(PersistenceUnitProcessor.java:585)
at org.eclipse.persistence.internal.jpa.EntityManagerSetupImpl.predeploy(EntityManagerSetupImpl.java:1865)
... 5 more
我在这方面尝试了很多东西，但我真的不知道接下来要尝试什么。我认为我做错了可怕的事情，但谷歌终于 exauhsted 自己。非常感谢任何帮助:)
所有要复制的相关文件如下：
家长：
package com.test;
import java.util.List;
import javax.persistence.Entity;
import javax.persistence.Id;
import javax.persistence.OneToMany;
@Entity
public class Parent {
@Id
private String id;
@OneToMany
private List<Child> children;
public String getId() {
return id;
}
public void setId(String id) {
this.id = id;
}
public List<Child> getChildren() {
return children;
}
public void setChildren(List<Child> children) {
this.children = children;
}
}
孩子：
package com.test;
import javax.persistence.Entity;
import javax.persistence.Id;
@Entity
public class Child {
@Id
private String id;
public String getId() {
return id;
}
public void setId(String id) {
this.id = id;
}
}
persistence.xml：
<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.
<persistence-unit name="Parent">
<class>com.test.Parent</class>
<properties>
<property name="javax.persistence.jdbc.driver" value="com.mysql.jdbc.Driver"/>
<property name="eclipselink.jdbc.read-connections.min" value="1" />
<property name="eclipselink.jdbc.write-connections.min" value="1" />
<property name="eclipselink.jdbc.batch-writing" value="JDBC" />
<property name="eclipselink.ddl-generation" value="create-or-extend-tables"/>
<property name="eclipselink.ddl-generation.output-mode" value="database"/>
<!-- Logging -->
<property name="eclipselink.logging.level" value="INFO" />
<property name="eclipselink.logging.timestamp" value="true" />
<property name="eclipselink.logging.session" value="true" />
<property name="eclipselink.logging.thread" value="false" />
</properties>
</persistence-unit>
<persistence-unit name="Child">
<class>com.test.Child</class>
<properties>
<property name="javax.persistence.jdbc.driver" value="com.mysql.jdbc.Driver"/>
<property name="eclipselink.jdbc.read-connections.min" value="1" />
<property name="eclipselink.jdbc.write-connections.min" value="1" />
<property name="eclipselink.jdbc.batch-writing" value="JDBC" />
<property name="eclipselink.ddl-generation" value="create-or-extend-tables"/>
<property name="eclipselink.ddl-generation.output-mode" value="database"/>
<!-- Logging -->
<property name="eclipselink.logging.level" value="INFO" />
<property name="eclipselink.logging.timestamp" value="true" />
<property name="eclipselink.logging.session" value="true" />
<property name="eclipselink.logging.thread" value="false" />
</properties>
</persistence-unit>
</persistence>
主类（用于测试）：
package com.test;
import java.util.HashMap;
import java.util.Map;
import javax.persistence.Persistence;
public class Main {
private static final String KEY_PERSISTENCE_URL = "javax.persistence.jdbc.url";
private static final String KEY_PERSISTENCE_USER = "javax.persistence.jdbc.user";
private static final String KEY_PERSISTENCE_PASS = "javax.persistence.jdbc.password";
public static void main(String[] args) {
Map<String, String> properties = new HashMap<>();
properties.put(KEY_PERSISTENCE_URL, "jdbc:mysql://localhost:3306/reporting");
properties.put(KEY_PERSISTENCE_USER, "root");
properties.put(KEY_PERSISTENCE_PASS, "p4ssw0rd");
Persistence.createEntityManagerFactory(Parent.class.getSimpleName(), properties);
}
}
【问题讨论】：
标签： java jpa persistence eclipselink