java - JPA，实体什么时候必须实现可序列化

Question

我目前正在学习 JPA。在文档中，它指出只有当实体被其他 JVM 远程分离时，它才需要是可序列化的。

但是，出于测试目的，我将实体创建为持久性类 (CDI) 的内部私有(private)类。当我尝试使用 EntityManager 保留实体时。我得到如下异常:

Caused by: Exception [EclipseLink-7155] (Eclipse Persistence Services - 2.5.0.v20130507-3faac2b): org.eclipse.persistence.exceptions.ValidationException
Exception Description: The type [class minh.ea.common.Ultilities.DatabaseLogger] for the attribute [this$0] on the entity class [class minh.ea.common.Ultilities.DatabaseLogger$LogRecord] is not a valid type for a serialized mapping. The attribute type must implement the Serializable interface.

据我了解，这个异常意味着我的实体属性需要像类一样是可序列化的。那么到底是什么原因，传递到哪里去了呢？

所有这些都在 GlassFish 4.0 容器下运行。使用 EclipseLink 2.1 的 JPA

我对持久化和内部实体的实现如下:

package minh.ea.common.Ultilities;

import java.util.Date;
import javax.enterprise.context.ApplicationScoped;
import javax.persistence.Entity;
import javax.persistence.EntityManager;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.PersistenceContext;
import javax.persistence.Temporal;
import javax.persistence.TemporalType;
import javax.transaction.Transactional;

/**
 *
 * @author Minh
 */

@ApplicationScoped
@minh.ea.common.Ultilities.qualifiers.Database
public class DatabaseLogger implements Logger {

    @PersistenceContext
    private EntityManager em;

    private final long MAX_SIZE=2097152;

    public DatabaseLogger(){

    }

    @Override
    @Transactional
    public void info(Object obj) {
        em.persist(new RecordEntry("INFO", new Date(), obj.toString()));
    }

    @Override
    @Transactional
    public void warn(Object obj) {
        em.persist(new RecordEntry("WARN", new Date(), obj.toString()));
    }

    @Override
    @Transactional
    public void error(Object obj) {
        em.persist(new RecordEntry("ERROR", new Date(), obj.toString()));
    }

    @Override
    @Transactional
    public void fatal(Object obj) {
        em.persist(new RecordEntry("FATAL", new Date(), obj.toString()));
    }

    @Entity
    public class LogRecord{

        @Id @GeneratedValue(strategy = GenerationType.IDENTITY)
        private int id;
        private String type;
        @Temporal(TemporalType.TIMESTAMP)
        private Date time;
        private String message;

        public String getType() {
            return type;
        }

        public void setType(String type) {
            this.type = type;
        }

        public Date getTime() {
            return time;
        }

        public void setTime(Date time) {
            this.time = time;
        }

        public String getMessage() {
            return message;
        }

        public void setMessage(String message) {
            this.message = message;
        }

        public LogRecord() {
        }

        public LogRecord(String type, Date time, String message) {
            this.type = type;
            this.time = time;
            this.message = message;
        }
    }

}

最好的问候，

Answer 1

根据 this reference ，有效的 Entity 类必须是顶级类，这意味着您的内部类将不起作用。

尝试将它拉出到它自己的 Entity 类中，就像在适当的系统中一样，然后再次持久化。