Maven 和“不是已知的实体类型”错误答案

【问题标题】：Maven and the " is not a known entity type" errorMaven 和“不是已知的实体类型”错误
【发布时间】：2011-04-01 01:35:32
【问题描述】：

我使用快速入门原型生成了一个 Maven 项目。于是我得到了如下的项目结构：

|-- src
| |-- main
| | |-- java      
| | |-- resources 
| |-- test
| | |-- java      
| | |-- resources 
|-- pom.xml

我修改了“pom.xml”文件：

<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>com.apress.javaee6</groupId>
  <artifactId>chapter02</artifactId>
  <version>1.0</version>
  <packaging>jar</packaging>

  <name>chapter02</name>
  <url>http://maven.apache.org</url>

  <properties>
    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
  </properties>

  <build>
    <plugins>
        <plugin>
            <groupId>org.apache.maven.plugins</groupId>
            <artifactId>maven-compiler-plugin</artifactId>
            <version>2.3.1</version>
        </plugin>
    </plugins>
  </build>
  <dependencies>
    <dependency>
      <groupId>junit</groupId>
      <artifactId>junit</artifactId>
      <version>3.8.1</version>
      <scope>test</scope>
    </dependency>
    <dependency>
        <groupId>javax.persistence</groupId>
        <artifactId>persistence-api</artifactId>
        <version>1.0</version>
    </dependency>
    <dependency>
        <groupId>org.eclipse.persistence</groupId>
        <artifactId>eclipselink</artifactId>
        <version>2.0.0</version>
    </dependency>
    <dependency>
        <groupId>org.apache.derby</groupId>
        <artifactId>derbyclient</artifactId>
        <version>10.6.1.0</version>
    </dependency>
    <dependency>
        <groupId>org.apache.derby</groupId>
        <artifactId>derby</artifactId>
        <version>10.6.1.0</version>
        <scope>test</scope>
    </dependency>
  </dependencies>
</project>

正如您所注意到的，我与德比一起工作。 “src/main/resources/META-INF/persistence.xml”是：

<?xml version="1.0" encoding="UTF-8"?>
<persistence xmlns="http://java.sun.com/xml/ns/persistence" version="1.0">

    <persistence-unit name="chapter02PU" transaction-type="RESOURCE_LOCAL">
        <provider>org.eclipse.persistence.jpa.PersistenceProvider</provider>
        <class>com.apress.javaee6.chapter02.Book</class>
        <properties>
            <property name="eclipselink.target-database" value="DERBY"/>
            <property name="eclipselink.ddl-generation" value="drop-and-create-tables"/>
            <property name="eclipselink.logging.level" value="INFO"/>
            <property name="javax.persistence.jdbc.driver" value="org.apache.derby.jdbc.ClientDriver"/>
            <property name="javax.persistence.jdbc.url" value="jdbc:derby://localhost:1527/chapter02DB;create=true"/>
            <property name="javax.persistence.jdbc.user" value="APP"/>
            <property name="javax.persistence.jdbc.password" value="APP"/>
        </properties>
    </persistence-unit>
</persistence>

然后，我创建了一个“书”类：

package com.apress.javaee6;
import javax.persistence.*;

@Entity
@NamedQuery(name = "findAllBooks", query = "SELECT b FROM Book b")
public class Book {

    // ======================================
    // =             Attributes             =
    // ======================================
    @Id
    @GeneratedValue
    private Long id;
    @Column(nullable = false)
    private String title;
    private Float price;
    @Column(length = 2000)
    private String description;
    private String isbn;
    private Integer nbOfPage;
    private Boolean illustrations;

    // ======================================
    // =            Constructors            =
    // ======================================

    public Book() {
    }

    public Book(String title, Float price, String description, String isbn, Integer nbOfPage, Boolean illustrations) {
        this.title = title;
        this.price = price;
        this.description = description;
        this.isbn = isbn;
        this.nbOfPage = nbOfPage;
        this.illustrations = illustrations;
    }

    // ======================================
    // =          Getters & Setters         =
    // ======================================
    public Long getId() {
        return id;
    }




    public String getTitle() {
        return title;
    }

    public void setTitle(String title) {
        this.title = title;
    }

    public Float getPrice() {
        return price;
    }

    public void setPrice(Float price) {
        this.price = price;
    }

    public String getDescription() {
        return description;
    }

    public void setDescription(String description) {
        this.description = description;
    }

    public String getIsbn() {
        return isbn;
    }

    public void setIsbn(String isbn) {
        this.isbn = isbn;
    }

    public Integer getNbOfPage() {
        return nbOfPage;
    }

    public void setNbOfPage(Integer nbOfPage) {
        this.nbOfPage = nbOfPage;
    }

    public Boolean getIllustrations() {
        return illustrations;
    }

    public void setIllustrations(Boolean illustrations) {
        this.illustrations = illustrations;
    }

    // ======================================
    // =         hash, equals, toString     =
    // ======================================

    @Override
    public String toString() {
        final StringBuilder sb = new StringBuilder();
        sb.append("Book");
        sb.append("{id=").append(id);
        sb.append(", title='").append(title).append('\'');
        sb.append(", price=").append(price);
        sb.append(", description='").append(description).append('\'');
        sb.append(", isbn='").append(isbn).append('\'');
        sb.append(", nbOfPage=").append(nbOfPage);
        sb.append(", illustrations=").append(illustrations);
        sb.append('}');
        return sb.toString();
    }
}

当然还有“主类”：

package com.apress.javaee6;

import javax.persistence.EntityManager;
import javax.persistence.EntityManagerFactory;
import javax.persistence.EntityTransaction;
import javax.persistence.Persistence;


public class Main {

    public static void main(String[] args) {

        // Creates an instance of book
        Book book = new Book();
        book.setId(1231L);
        book.setTitle("The Hitchhiker's Guide to the Galaxy");
        book.setPrice(12.5F);
        book.setDescription("Science fiction comedy series created by Douglas Adams.");
        book.setIsbn("1-84023-742-2");
        book.setNbOfPage(354);
        book.setIllustrations(false);

        // Gets an entity manager and a transaction
        EntityManagerFactory emf = Persistence.createEntityManagerFactory("chapter02PU");
        EntityManager em = emf.createEntityManager();
        EntityTransaction tx = em.getTransaction();

        // Persists the book to the database
        tx.begin();
        em.persist(book);
        tx.commit();

        em.close();
        emf.close();
    }
}

我启动 Derby 服务器：

./derby/bin/startNetworkServer

问题是当我运行主类时：

mvn exec:java -Dexec.mainClass="com.apress.javaee6.Main"

我收到以下错误：

[INFO] ------------------------------------------------------------------------
[ERROR] BUILD ERROR
[INFO] ------------------------------------------------------------------------
[INFO] An exception occured while executing the Java class. null

Object: Book{id=null, title='The Hitchhiker's Guide to the Galaxy', price=12.5, description='Science fiction comedy series created by Douglas Adams.', isbn='1-84023-742-2', nbOfPage=354, illustrations=false} is not a known entity type.

我认为问题在于“id=null”。但是，当我手动设置 Id（例如设置为 123）时，我会收到相同的错误消息。我还尝试在 Book 类中使用以下注释：

@GeneratedValue(strategy=GenerationType.AUTO)

或

@GeneratedValue(strategy=GenerationType.IDENTITY)

有人有解决这个错误的方法吗？

PS：这里是打开错误堆栈跟踪的 exec 命令结果：

+ Error stacktraces are turned on.
[INFO] Scanning for projects...
[INFO] Searching repository for plugin with prefix: 'exec'.
[INFO] ------------------------------------------------------------------------
[INFO] Building chapter02
[INFO]    task-segment: [exec:java]
[INFO] ------------------------------------------------------------------------
[INFO] Preparing exec:java
[INFO] No goals needed for project - skipping
[INFO] [exec:java {execution: default-cli}]
[EL Finest]: 2010-08-19 13:38:37.215--ServerSession(6419763)--Thread(Thread[com.apress.javaee6.Main.main(),5,com.apress.javaee6.Main])--Begin predeploying Persistence Unit chapter02PU; session file:/home/zakaria/Dev/chapter02/target/classes/_chapter02PU; state Initial; factoryCount 0
[EL Finest]: 2010-08-19 13:38:37.243--ServerSession(6419763)--Thread(Thread[com.apress.javaee6.Main.main(),5,com.apress.javaee6.Main])--property=eclipselink.orm.throw.exceptions; default value=true
[EL Finer]: 2010-08-19 13:38:37.272--ServerSession(6419763)--Thread(Thread[com.apress.javaee6.Main.main(),5,com.apress.javaee6.Main])--Searching for default mapping file in file:/home/zakaria/Dev/chapter02/target/classes/
[EL Finer]: 2010-08-19 13:38:37.276--ServerSession(6419763)--Thread(Thread[com.apress.javaee6.Main.main(),5,com.apress.javaee6.Main])--Searching for default mapping file in file:/home/zakaria/Dev/chapter02/target/classes/
[EL Finest]: 2010-08-19 13:38:37.3--ServerSession(6419763)--Thread(Thread[com.apress.javaee6.Main.main(),5,com.apress.javaee6.Main])--End predeploying Persistence Unit chapter02PU; session file:/home/zakaria/Dev/chapter02/target/classes/_chapter02PU; state Predeployed; factoryCount 0
[EL Finer]: 2010-08-19 13:38:37.3--Thread(Thread[com.apress.javaee6.Main.main(),5,com.apress.javaee6.Main])--JavaSECMPInitializer - transformer is null.
[EL Finest]: 2010-08-19 13:38:37.3--ServerSession(6419763)--Thread(Thread[com.apress.javaee6.Main.main(),5,com.apress.javaee6.Main])--Begin predeploying Persistence Unit chapter02PU; session file:/home/zakaria/Dev/chapter02/target/classes/_chapter02PU; state Predeployed; factoryCount 0
[EL Finest]: 2010-08-19 13:38:37.301--ServerSession(6419763)--Thread(Thread[com.apress.javaee6.Main.main(),5,com.apress.javaee6.Main])--End predeploying Persistence Unit chapter02PU; session file:/home/zakaria/Dev/chapter02/target/classes/_chapter02PU; state Predeployed; factoryCount 1
[EL Finest]: 2010-08-19 13:38:37.309--ServerSession(6419763)--Thread(Thread[com.apress.javaee6.Main.main(),5,com.apress.javaee6.Main])--Begin deploying Persistence Unit chapter02PU; session file:/home/zakaria/Dev/chapter02/target/classes/_chapter02PU; state Predeployed; factoryCount 1
[EL Finer]: 2010-08-19 13:38:37.315--ServerSession(6419763)--Thread(Thread[com.apress.javaee6.Main.main(),5,com.apress.javaee6.Main])--Could not initialize Validation Factory. Encountered following exception: java.lang.NoClassDefFoundError: javax/validation/Validation
[EL Finest]: 2010-08-19 13:38:37.323--ServerSession(6419763)--Thread(Thread[com.apress.javaee6.Main.main(),5,com.apress.javaee6.Main])--property=eclipselink.logging.level; value=FINEST; translated value=FINEST
[EL Finest]: 2010-08-19 13:38:37.323--ServerSession(6419763)--Thread(Thread[com.apress.javaee6.Main.main(),5,com.apress.javaee6.Main])--property=eclipselink.logging.level; value=FINEST; translated value=FINEST
[EL Finest]: 2010-08-19 13:38:37.324--ServerSession(6419763)--Thread(Thread[com.apress.javaee6.Main.main(),5,com.apress.javaee6.Main])--property=javax.persistence.jdbc.user; value=APP
[EL Finest]: 2010-08-19 13:38:37.324--ServerSession(6419763)--Thread(Thread[com.apress.javaee6.Main.main(),5,com.apress.javaee6.Main])--property=javax.persistence.jdbc.password; value=xxxxxx
[EL Finest]: 2010-08-19 13:38:37.429--ServerSession(6419763)--Thread(Thread[com.apress.javaee6.Main.main(),5,com.apress.javaee6.Main])--property=eclipselink.target-database; value=DERBY; translated value=org.eclipse.persistence.platform.database.DerbyPlatform
[EL Finest]: 2010-08-19 13:38:37.437--ServerSession(6419763)--Thread(Thread[com.apress.javaee6.Main.main(),5,com.apress.javaee6.Main])--property=javax.persistence.jdbc.driver; value=org.apache.derby.jdbc.ClientDriver
[EL Finest]: 2010-08-19 13:38:37.438--ServerSession(6419763)--Thread(Thread[com.apress.javaee6.Main.main(),5,com.apress.javaee6.Main])--property=javax.persistence.jdbc.url; value=jdbc:derby://localhost:1527/chapter02DB
[EL Info]: 2010-08-19 13:38:37.439--ServerSession(6419763)--Thread(Thread[com.apress.javaee6.Main.main(),5,com.apress.javaee6.Main])--EclipseLink, version: Eclipse Persistence Services - 2.0.0.v20091127-r5931
[EL Config]: 2010-08-19 13:38:37.46--ServerSession(6419763)--Connection(22664464)--Thread(Thread[com.apress.javaee6.Main.main(),5,com.apress.javaee6.Main])--connecting(DatabaseLogin(
    platform=>DerbyPlatform
    user name=> "APP"
    datasource URL=> "jdbc:derby://localhost:1527/chapter02DB"
))
[EL Config]: 2010-08-19 13:38:37.857--ServerSession(6419763)--Connection(25782860)--Thread(Thread[com.apress.javaee6.Main.main(),5,com.apress.javaee6.Main])--Connected: jdbc:derby://localhost:1527/chapter02DB
    User: APP
    Database: Apache Derby  Version: 10.6.1.0 - (938214)
    Driver: Apache Derby Network Client JDBC Driver  Version: 10.6.1.0 - (938214)
[EL Config]: 2010-08-19 13:38:37.857--ServerSession(6419763)--Connection(10594949)--Thread(Thread[com.apress.javaee6.Main.main(),5,com.apress.javaee6.Main])--connecting(DatabaseLogin(
    platform=>DerbyPlatform
    user name=> "APP"
    datasource URL=> "jdbc:derby://localhost:1527/chapter02DB"
))
[EL Config]: 2010-08-19 13:38:37.863--ServerSession(6419763)--Connection(29499086)--Thread(Thread[com.apress.javaee6.Main.main(),5,com.apress.javaee6.Main])--Connected: jdbc:derby://localhost:1527/chapter02DB
    User: APP
    Database: Apache Derby  Version: 10.6.1.0 - (938214)
    Driver: Apache Derby Network Client JDBC Driver  Version: 10.6.1.0 - (938214)
[EL Info]: 2010-08-19 13:38:37.885--ServerSession(6419763)--Thread(Thread[com.apress.javaee6.Main.main(),5,com.apress.javaee6.Main])--file:/home/zakaria/Dev/chapter02/target/classes/_chapter02PU login successful
[EL Finest]: 2010-08-19 13:38:37.933--ServerSession(6419763)--Thread(Thread[com.apress.javaee6.Main.main(),5,com.apress.javaee6.Main])--End deploying Persistence Unit chapter02PU; session file:/home/zakaria/Dev/chapter02/target/classes/_chapter02PU; state Deployed; factoryCount 1
[EL Finer]: 2010-08-19 13:38:38.004--ServerSession(6419763)--Thread(Thread[com.apress.javaee6.Main.main(),5,com.apress.javaee6.Main])--client acquired
[INFO] ------------------------------------------------------------------------
[ERROR] BUILD ERROR
[INFO] ------------------------------------------------------------------------
[INFO] An exception occured while executing the Java class. null

Object: Book{id=1231, title='The Hitchhiker's Guide to the Galaxy', price=12.5, description='Science fiction comedy series created by Douglas Adams.', isbn='1-84023-742-2', nbOfPage=354, illustrations=false} is not a known entity type.
[INFO] ------------------------------------------------------------------------
[INFO] Trace
org.apache.maven.lifecycle.LifecycleExecutionException: An exception occured while executing the Java class. null
    at org.apache.maven.lifecycle.DefaultLifecycleExecutor.executeGoals(DefaultLifecycleExecutor.java:719)
    at org.apache.maven.lifecycle.DefaultLifecycleExecutor.executeStandaloneGoal(DefaultLifecycleExecutor.java:569)
    at org.apache.maven.lifecycle.DefaultLifecycleExecutor.executeGoal(DefaultLifecycleExecutor.java:539)
    at org.apache.maven.lifecycle.DefaultLifecycleExecutor.executeGoalAndHandleFailures(DefaultLifecycleExecutor.java:387)
    at org.apache.maven.lifecycle.DefaultLifecycleExecutor.executeTaskSegments(DefaultLifecycleExecutor.java:348)
    at org.apache.maven.lifecycle.DefaultLifecycleExecutor.execute(DefaultLifecycleExecutor.java:180)
    at org.apache.maven.DefaultMaven.doExecute(DefaultMaven.java:328)
    at org.apache.maven.DefaultMaven.execute(DefaultMaven.java:138)
    at org.apache.maven.cli.MavenCli.main(MavenCli.java:362)
    at org.apache.maven.cli.compat.CompatibleMain.main(CompatibleMain.java:60)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:616)
    at org.codehaus.classworlds.Launcher.launchEnhanced(Launcher.java:315)
    at org.codehaus.classworlds.Launcher.launch(Launcher.java:255)
    at org.codehaus.classworlds.Launcher.mainWithExitCode(Launcher.java:430)
    at org.codehaus.classworlds.Launcher.main(Launcher.java:375)
Caused by: org.apache.maven.plugin.MojoExecutionException: An exception occured while executing the Java class. null
    at org.codehaus.mojo.exec.ExecJavaMojo.execute(ExecJavaMojo.java:346)
    at org.apache.maven.plugin.DefaultPluginManager.executeMojo(DefaultPluginManager.java:490)
    at org.apache.maven.lifecycle.DefaultLifecycleExecutor.executeGoals(DefaultLifecycleExecutor.java:694)
    ... 17 more
Caused by: java.lang.reflect.InvocationTargetException
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:616)
    at org.codehaus.mojo.exec.ExecJavaMojo$1.run(ExecJavaMojo.java:291)
    at java.lang.Thread.run(Thread.java:636)
Caused by: java.lang.IllegalArgumentException: Object: Book{id=1231, title='The Hitchhiker's Guide to the Galaxy', price=12.5, description='Science fiction comedy series created by Douglas Adams.', isbn='1-84023-742-2', nbOfPage=354, illustrations=false} is not a known entity type.
    at org.eclipse.persistence.internal.sessions.UnitOfWorkImpl.registerNewObjectForPersist(UnitOfWorkImpl.java:4147)
    at org.eclipse.persistence.internal.jpa.EntityManagerImpl.persist(EntityManagerImpl.java:368)
    at com.apress.javaee6.Main.main(Main.java:30)
    ... 6 more
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 4 seconds
[INFO] Finished at: Thu Aug 19 13:38:38 CEST 2010
[INFO] Final Memory: 8M/68M
[INFO] ------------------------------------------------------------------------
[EL Finer]: 2010-08-19 13:38:38.213--UnitOfWork(24128584)--Thread(Thread[Finalizer,8,system])--release unit of work
[EL Finer]: 2010-08-19 13:38:38.214--ClientSession(23817301)--Thread(Thread[Finalizer,8,system])--client released

非常感谢，问候。

【问题讨论】：

请运行带有 -e 标志的 mvn 命令并发布堆栈跟踪
@seanize：我添加了错误堆栈跟踪。

标签： java jpa eclipselink derby

【解决方案1】：

我认为问题在于“id=null”。但是，当我手动设置 Id（例如设置为 123）时，我会收到相同的错误消息。

不，您不应该在使用 GeneratedValue 时设置 Id。

有人有解决这个错误的方法吗？

问题的根本原因是没有生成BOOK 表（因此EclipseLink 无法正确映射Book 实体，然后无法将其识别为实体）。

发生这种情况是因为persistence.xml 中列出的类的完全限定名称与实际的 FQN 不匹配（com.apress.javaee6.chapter02.Book 与 com.apress.javaee6.Book）。

所以要么更改类的包或修复persistence.xml：

<?xml version="1.0" encoding="UTF-8"?>
<persistence xmlns="http://java.sun.com/xml/ns/persistence" version="1.0">

    <persistence-unit name="chapter02PU" transaction-type="RESOURCE_LOCAL">
        <provider>org.eclipse.persistence.jpa.PersistenceProvider</provider>
        <class>com.apress.javaee6.Book</class>
        <properties>
            <property name="eclipselink.target-database" value="DERBY"/>
            <property name="eclipselink.ddl-generation" value="drop-and-create-tables"/>
            <property name="eclipselink.logging.level" value="INFO"/>
            <property name="javax.persistence.jdbc.driver" value="org.apache.derby.jdbc.ClientDriver"/>
            <property name="javax.persistence.jdbc.url" value="jdbc:derby://localhost:1527/chapter02DB;create=true"/>
            <property name="javax.persistence.jdbc.user" value="APP"/>
            <property name="javax.persistence.jdbc.password" value="APP"/>
        </properties>
    </persistence-unit>
</persistence>

运行mvn exec:java -Dexec.mainClass="com.apress.javaee6.Main" 会成功：

mvn exec:java -Dexec.mainClass="com.apress.javaee6.Main" -e +错误堆栈跟踪已打开。 [INFO] 正在扫描项目... [INFO] 在存储库中搜索前缀为“exec”的插件。 [信息] --------------------------------------------- ------------------------- [INFO] 构建 Q3521044 - Maven 和“不是已知的实体类型”错误 [INFO] 任务段：[exec:java] [信息] --------------------------------------------- ------------------------- [信息] 准备执行：java [INFO] 项目不需要目标 - 跳过 [信息] [执行：java {执行：默认-cli}] [EL 信息]：2010-08-19 16:39:54.442--ServerSession(2698418)--EclipseLink，版本：Eclipse Persistence Services - 2.0.0.v20091127-r5931 [EL Info]: 2010-08-19 16:39:55.875--ServerSession(2698418)--file:/home/pascal/Projects/stackoverflow/Q3521044/target/classes/_chapter02PU登录成功 [EL 警告]：2010-08-19 16:39:56.219--ServerSession(2698418)--异常 [EclipseLink-4002] (Eclipse Persistence Services - 2.0.0.v20091127-r5931): org.eclipse.persistence.exceptions .DatabaseException 内部异常：java.sql.SQLException：表/视图“SEQUENCE”已存在于模式“APP”中。错误代码：-1 调用：CREATE TABLE SEQUENCE (SEQ_NAME VARCHAR(50) NOT NULL, SEQ_COUNT DECIMAL(15), PRIMARY KEY (SEQ_NAME)) 查询：DataModifyQuery(sql="CREATE TABLE SEQUENCE (SEQ_NAME VARCHAR(50) NOT NULL, SEQ_COUNT DECIMAL(15), PRIMARY KEY (SEQ_NAME))") [EL信息]：2010-08-19 16:39:56.574--ServerSession(2698418)--file:/home/pascal/Projects/stackoverflow/Q3521044/target/classes/_chapter02PU注销成功 [信息] --------------------------------------------- ------------------------- [信息] 构建成功 [信息] --------------------------------------------- ------------------------- [信息] --------------------------------------------- ------------------------- [INFO] 总时间：11 秒 [INFO] 完成时间：2010 年 8 月 19 日星期四 16:39:56 CEST [INFO] 最终内存：17M/88M [信息] --------------------------------------------- -------------------------

但是在我看来，报错很差，EclipseLink应该会报表丢失。

参考文献

JPA 1.0 规范
- 6.2.1.6 映射文件、jar 文件、类、排除未列出的类

【讨论】：

我无言以对（或“无字”哈哈）。有效！非常感谢！
@Zakaria：我发现了真正的问题（书的真正完全限定名称与persistence.xml 中的名称不匹配）并相应地更新了我的答案。
天才。谢谢您的帮助。有同样的问题。

【解决方案2】：

Eclipselink 经常出现这种错误。我找到的唯一答案是这个，一个开放的错误：

bug link at eclipse.org

简而言之，这个错误来自 EclipseLink + (osGI) 联合使用，在重建你的 jar 时，会保留指向“旧”实体的指针而不是使用新实体，因此会出现实体未知的错误。我的解决方案是重新启动 IDE，清理，构建，重新启动我的服务器，安装 jar/war，运行..

不知道是不是你的问题，但可能是……

【讨论】：

我不认为这是“IDE”的问题。我使用“IDE”来编辑代码。但是，对于编译和运行操作，我使用“mvn”命令。

【解决方案3】：

我自己没有使用过 EclipseLink，所以我只能猜测，但令我惊讶的是，您的类没有 id 属性的设置器。

我不知道根据 JPA 规范这是否合法，但我以前从未遇到过这种情况。在我知道的所有 JPA 应用程序中，所有非瞬态属性都有公共 getter 和 setter。（当然其中一些永远不应该手动使用，比如 id 属性，但是 Persistence Provider 需要它们）。所以尝试添加一个 setId() 方法，我们将从那里获取它...

【讨论】：

我已经尝试过这样做。然后，我在主类中手动设置了 id（我在这篇文章中谈到了它）。但它没有工作:(