对象：不是已知的实体类型。 Eclipse链接

Question

我是 eclipselink 或 jpa 的新手。我正在关注 here 中的 eclipselink 教程。当我运行 Test.java class 时出现以下异常。我正在通过网络使用 oracle 数据库。请帮助我。

[EL Info]: connection: 2016-09-14 15:13:33.562--ServerSession(271944754)--/file:/D:/Developer/EclipseLink/bin/_TestPersistence login successful
[EL Warning]: metamodel: 2016-09-14 15:13:33.577--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: Employee [name=Mukesh, email=m@gmail.com , department=Finance] is not a known Entity type.
    at org.eclipse.persistence.internal.sessions.UnitOfWorkImpl.registerNewObjectForPersist(UnitOfWorkImpl.java:4226)
    at org.eclipse.persistence.internal.jpa.EntityManagerImpl.persist(EntityManagerImpl.java:507)
    at com.assignment.Test.main(Test.java:28)

persistence.xml

<?xml version="1.0" encoding="UTF-8" ?>
<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_2_0.xsd"
version="2.0" xmlns="http://java.sun.com/xml/ns/persistence">
<persistence-unit name="TestPersistence"
transaction-type="RESOURCE_LOCAL">
<class>com.assignment.Employee</class>
<properties>
<property name="javax.persistence.jdbc.driver" value="oracle.jdbc.driver.OracleDriver" />
<property name="javax.persistence.jdbc.url"
value="jdbc:oracle:thin:@ipaddress:port/servicename" />
<property name="javax.persistence.jdbc.user" value="username" />
<property name="javax.persistence.jdbc.password"
value="password" />
<!-- EclipseLink should create the database schema automatically -->
<property name="eclipselink.ddl-generation" value="create-tables" />
<property name="eclipselink.ddl-generation.output-mode"
value="database" />
</properties>
</persistence-unit>
</persistence>

Employee.java

package com.assignment;
public class Employee {
        private Long id;
        private String name;
        private String email;
        private String department;

        public Long getId() {
            return id;
        }
        public void setId(Long id) {
            this.id = id;
        }
        public String getName() {
            return name;
        }
        public void setName(String name) {
            this.name = name;
        }
        public String getEmail() {
            return email;
        }
        public void setEmail(String email) {
            this.email = email;
        }
        public String getDepartment() {
            return department;
        }
        public void setDepartment(String department) {
            this.department = department;
        }
        public String toString() {
            return "Employee [name=" + name + ", email=" + email + " , department="
                    + department + "]";
        }
}

Test.java

package com.assignment;

import java.util.List;
import javax.persistence.EntityManager;
import javax.persistence.EntityManagerFactory;
import javax.persistence.Persistence;
import javax.persistence.Query;

public class Test {
    private static final String PERSISTENCE_UNIT_NAME = "TestPersistence";
      private static EntityManagerFactory factory;
      public static void main(String[] args) {
        factory = Persistence.createEntityManagerFactory(PERSISTENCE_UNIT_NAME);
        EntityManager em = factory.createEntityManager();
        em.getTransaction().begin();
        Employee emp = new Employee();
        emp.setName("Mukesh");
        emp.setEmail("m@gmail.com");
        emp.setDepartment("Finance");
        em.persist(emp);
        em.getTransaction().commit();
        em.close();
      }
    }

包结构

Answer 1

尝试对 Employee class 使用 javax.persistence.Entity 注释。

EclipseLink 用法的更多信息和示例： https://wiki.eclipse.org/EclipseLink/Examples/JPA

Answer 2

为您的 class 添加 @Entity 注释。您可能还需要一个主键 ID，将 @Id 指定给其中一个属性。

package com.assignment;

import javax.persistence.Entity;
import javax.persistence.Id;

@Entity
public class Employee {
        @Id
        private Long id;
        private String name;
        private String email;
        private String department;

        public Long getId() {
            return id;
        }
        public void setId(Long id) {
            this.id = id;
        }
        public String getName() {
            return name;
        }
        public void setName(String name) {
            this.name = name;
        }
        public String getEmail() {
            return email;
        }
        public void setEmail(String email) {
            this.email = email;
        }
        public String getDepartment() {
            return department;
        }
        public void setDepartment(String department) {
            this.department = department;
        }
        public String toString() {
            return "Employee [name=" + name + ", email=" + email + " , department="
                    + department + "]";
        }
}

对象：不是已知的实体类型。 Eclipse链接

Object: is not a known Entity type. Eclipselink

java

jpa

eclipselink