EclipseLink：未加载实体

Question

我有一个 JPA 项目，我正在尝试将其更新到 JPA 2.2.0 和 EclipseLink 5.7.1，因为我运行进入 bug 429992 of EclipseLink。使用新版本后，我无法再执行我的应用程序 – EclipseLink 抛出类似于以下内容的异常（我下面示例的简短变体）：

[EL Warning]: metamodel: 2018-06-20 22:38:14.1--Thread(Thread[main,5,main])--The collection of metamodel types is empty. Model classes may not have been found during entity search for Java SE and some Java EE container managed persistence units.  Please verify that your entity classes are referenced in persistence.xml using either <class> elements or a global <exclude-unlisted-classes>false</exclude-unlisted-classes> element
[...]

Exception in thread "main" java.lang.IllegalArgumentException: Object: Artifact@17d919b6 is not a known Entity type.
    at org.eclipse.persistence.internal.sessions.UnitOfWorkImpl.registerNewObjectForPersist(UnitOfWorkImpl.java:4324)
    at org.eclipse.persistence.internal.jpa.EntityManagerImpl.persist(EntityManagerImpl.java:593)
    at Main.main(Main.java:12)

在更新之前，一切正常（除了上述错误），而且如果我检查较早的提交，也没有问题。

我使用下面附带的最小设置重现了此行为。

该项目是使用Java SE 10编译的，因为IDE我使用的是Eclipse，但是在我的项目属性中，我只能选择select "Generic 2.1" 作为 JPA 平台。这可能是个问题吗？

你能重现这个错误吗？

据我所知，Entity-class 列在 persistence.xml 中并且还用 @Entity 注释，但 EclipseLink 未加载。清理项目甚至创建新项目都不能解决问题。

你知道我的错误可能是什么吗？我是否遗漏了有关 JPA 2.2/EclipseLink 2.7.1 用法的任何基本要点？

感谢您的任何提示或意见！

main 方法在主 class:

EntityManagerFactory entityManagerFactory = Persistence.createEntityManagerFactory("Example");
EntityManager entityManager = entityManagerFactory.createEntityManager();

entityManager.getTransaction().begin();
Artifact artifact = new Artifact();
entityManager.persist(artifact);
entityManager.getTransaction().commit();

entityManager.close();
entityManagerFactory.close();

实体Artifact：

import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.NamedQuery;

@Entity
@NamedQuery(name = "Artifact.findAll", query = "SELECT a FROM Artifact a")
public class Artifact {
    private int id;

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    public int getId() {
        return this.id;
    }

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

persistence.xml:

<?xml version="1.0" encoding="UTF-8"?>
<persistence version="2.1" xmlns="http://xmlns.jcp.org/xml/ns/persistence" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/persistence http://xmlns.jcp.org/xml/ns/persistence/persistence_2_1.xsd">
    <persistence-unit name="Example">
        <provider>org.eclipse.persistence.jpa.PersistenceProvider</provider>
        <class>Artifact</class>

        <properties>
            <property name="javax.persistence.jdbc.driver" value="org.h2.Driver"/>
            <property name="javax.persistence.jdbc.url" value="jdbc:h2:./inventory;create=true"/>
            <property name="javax.persistence.jdbc.user" value="APP"/>
            <property name="javax.persistence.jdbc.password" value="APP"/>
            <property name="eclipselink.logging.level" value="FINEST"/>            
            <property name="eclipselink.ddl-generation" value="create-or-extend-tables"/>
            <property name="eclipselink.ddl-generation.output-mode" value="database"/>
        </properties>
    </persistence-unit>
</persistence>

pom.xml 对于 Maven 依赖项：

<project xmlns="http://maven.apache.org/POM/4.0.0"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <groupId>JPATest</groupId>
    <artifactId>JPATest</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <build>
        <sourceDirectory>src</sourceDirectory>
        <plugins>
            <plugin>
                <artifactId>maven-compiler-plugin</artifactId>
                <version>3.7.0</version>
                <configuration>
                    <release>10</release>
                </configuration>
            </plugin>
        </plugins>
    </build>
    <dependencies>
        <!-- https://mvnrepository.com/artifact/org.eclipse.persistence/javax.persistence -->
        <dependency>
            <groupId>org.eclipse.persistence</groupId>
            <artifactId>javax.persistence</artifactId>
            <version>2.2.0</version>
        </dependency>

        <!-- https://mvnrepository.com/artifact/org.eclipse.persistence/eclipselink -->
        <dependency>
            <groupId>org.eclipse.persistence</groupId>
            <artifactId>eclipselink</artifactId>
            <version>2.7.1</version>
        </dependency>

        <!-- https://mvnrepository.com/artifact/com.h2database/h2 -->
        <dependency>
            <groupId>com.h2database</groupId>
            <artifactId>h2</artifactId>
            <version>1.4.197</version>
        </dependency>
    </dependencies>
</project>

Answer 1

我有几乎相同的环境并遇到相同的问题。我几乎不敢说，但在 eclipse 中 "project/maven/update project ..." 有所帮助（到目前为止）。

Answer 2

我也遇到了同样的问题。最后，通过 pom.xml.

中的更新解决了这个问题

Eclipselink 2.7.1 版本有一些错误已在较新版本中修复。

     <dependency>
        <groupId>org.eclipse.persistence</groupId>
        <artifactId>eclipselink</artifactId>
        <version>2.7.1</version>
    </dependency>

到

 <version>2.7.5</version>

更新前，实体未加载且 em.getMetamodel() 为空。更新后，我的所有实体都已成功加载

可以从 this link.

访问问题和已修复的错误

EclipseLink：未加载实体

EclipseLink: Entities not loaded

java

jpa

eclipselink

jpa-2.2