来自Jpa代码的Jar文件不起作用

Question

我开发了一个简单的代码，通过在实体类“employee”和“Department”上使用JPA的CRUD操作（find）来显示员工姓名。在运行代码时，它工作正常，但真正的问题来了，当我从应用程序创建一个jar文件时，jar文件出现了一个异常，我将该异常写在一个txt文件中

下面是Employee类

    package com.tutorialspoint.eclipselink.entity;

    import java.util.*;
    import javax.persistence.*;

    @Entity
    public class Employee {
    @Id
    @GeneratedValue(strategy= GenerationType.AUTO)  
    private int eid;

    @Temporal(TemporalType.TIMESTAMP)
    private java.util.Date dop;

    private String ename;
    private double salary;
    private String deg;

    @OneToOne(targetEntity = Department.class)
    private Department dept;

    @OneToMany (targetEntity = Staff.class)
    private ArrayList<Staff> staffs;

    public Employee(int eid, String ename, double salary, String deg) {
       super( );
       this.eid = eid;
       this.ename = ename;
       this.salary = salary;
       this.deg = deg;
    }

    public Employee( ) {
         super();
    }

    public Date getDop() {
         return dop;
    }

    public void setDop(Date dop) {
         this.dop = dop;
    }

    public int getEid( ) {
        return eid;
    }

    public void setEid(int eid) {
        this.eid = eid;
    }

    public Department getDept() {
        return dept;
    }

    public void setDept(Department dept) {
        this.dept = dept;
    } 

    public String getEname( ) {
        return ename;
    }

    public void setEname(String ename) {
       this.ename = ename;
    }

    public double getSalary( ) {
       return salary;
    }

    public void setSalary(double salary) {
       this.salary = salary;
    }

    public String getDeg( ) {
         return deg;
    }

    public void setDeg(String deg) {
        this.deg = deg;
    }

    public ArrayList<Staff> getStaffs() {
        return staffs;
    }

    public void setStaffs(ArrayList<Staff> staffs) {
        this.staffs = staffs;
    }
    }

下面是显示员工姓名和学位的类

    public void findEmployee(){
    try{
        EntityManagerFactory emfactory = Persistence.createEntityManagerFactory( "Eclipselink_JPA" );
        EntityManager entitymanager = emfactory.createEntityManager();
        Employee employee = entitymanager.find( Employee.class, 204 ); 
        JOptionPane.showMessageDialog(null, employee.getEname()+ 
        "=>"+employee.getDeg());

        }catch(Exception ex){
              JOptionPane.showMessageDialog(null,ex.getMessage());
              displayMsg(ex.getMessage());
         }
        }
    public void displayMsg(String msg){
    // i made this method to display the exception in a txt file
        File f = new File("E:\\bug2.txt");
        FileWriter fw = new FileWriter(f);
        PrintWriter pw = new PrintWriter(fw);
        pw.println(msg);
        pw.flush();pw.close();

    }

下面是异常“exception[EclipseLink-28019]（Eclipse Persistence Services-2.5.2.v20140319-9AD6ABD):org.Eclipse.Persistence.exceptions.EntityManagerSetupException异常描述：PersistenceUnit[Eclipselink_JPA]的部署失败。关闭此PersistenceUnit的所有工厂。内部异常：exception[EclipseLink-0]（Eclipse Persistence Services

Exception[EclipseLink-1]（Eclipse Persistence Services-2.5.2.v20140319-9AD6ABD):org.Eclipse.Persistence.exceptions.DescriptoreXception

异常说明：属性[teacherSet]未声明为ValueHolderInterface类型，但其映射使用间接方式。

映射：org.eclipse.persistence.mappings.manyTomanyMapping[teacherSet]描述符：RelationalDescriptor（com.tutorialspoint.eclipselink.entity.CLAS-->[databaseTable(CLAS)])

Exception[EclipseLink-1]（Eclipse Persistence Services-2.5.2.v20140319-9AD6ABD):org.Eclipse.Persistence.exceptions.DescriptoreXception

异常说明：属性[staffs]未声明为ValueHolderInterface类型，但它的映射使用间接方式。映射:org.eclipse.persistence.mappings.manytomanymapping[staffs]

描述符:RelationalDescriptor(com.tutorialspoint.eclipselink.entity.employee-->[databasetable(EMPLOYEE)])

Answer 1

涉及像ValueHolders和间接这样的接口的异常很可能是由于实体编织造成的问题。

实体编织是一个修改已编译实体的字节码的过程，以便它们实现更多的接口，并添加新的方法，以便它们能够处理间接和延迟加载等特性。

您的IDE是Oracle JDeveloper吗？默认情况下，它是具有自动执行此操作的运行配置的IDE之一，以便您的实体能够正确工作。这可以在其他IDE中以类似的方式进行配置--通过添加-javaagent: 作为程序参数（或在某些IDE中的Java选项）。查看这篇博客文章以获得一些快速信息。

在您的部署中，可能会出现Eclipselink的动态（运行时）编织失败（或由于某种原因不完整）的情况。也许您应该在将实体打包到部署工件之前考虑静态编织。

有关此操作的更多信息：https://wiki.eclipse.org/eclipselink/userguide/jpa/advanced_jpa_development/performance/weaving/static_wiving