该类不定义公共默认构造函数，或者该构造函数引发异常。内部异常：java.lang.InstantiationException

Question

大家好，我的JPA项目有问题。java实现了一个接口“filesystemelement.java”这些是我的类application.java

package com.bfi.webtop.model;



import java.io.Serializable;
import java.util.*;

import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.IdClass;
import javax.persistence.Table;

/** @pdOid d477195f-149e-4336-8586-19d6a09ee2d4 */
@Entity
@Table(name="application_")
public abstract class Application implements FileSystemElement, Serializable {
//  public Application() {
//      super();
//  }



  public Application(int id_app, String url) {
super();
this.id_app = id_app;
this.url = url;
  }



      public Application() {
  super();
  // TODO Auto-generated constructor stub
   }



  private int id_app;

  private java.lang.String url;

  /**
  * @return the url
  */
  public java.lang.String getUrl() {
return url;
   }

         /**
  * @param url the url to set
     */
      public void setUrl(java.lang.String url) {
          this.url = url;
    }

    /**
      * @return the id_app
   */
 @Id
 @GeneratedValue(strategy=GenerationType.AUTO)
public int getId_app() {
return id_app;
}

/**
 * @param id_app the id_app to set
 */
public void setId_app(int id_app) {
this.id_app = id_app;
}

}

package com.bfi.webtop.model;

/***********************************************************************
 * Module:  Fichier.java
 * Author:  Marwa
 * Purpose: Defines the Class Fichier
 ***********************************************************************/

import java.util.*;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;


@Entity
public abstract class Fichier implements FileSystemElement {
 private int id_fichier;

   private java.lang.String extension;
   private java.lang.Boolean supprim;
/**
 * @return the extension
 */
public java.lang.String getExtension() {
return extension;
}
/**
 * @param extension the extension to set
 */
 public void setExtension(java.lang.String extension) {
this.extension = extension;
}
/**
 * @return the supprim
 */
public java.lang.Boolean getSupprim() {
return supprim;
}
/**
 * @param supprim the supprim to set
 */
public void setSupprim(java.lang.Boolean supprim) {
this.supprim = supprim;
}
/**
* @return the id_fichier
*/
@Id
@GeneratedValue(strategy=GenerationType.AUTO)
public int getId_fichier() {
return id_fichier;
}
/**
 * @param id_fichier the id_fichier to set
*/
 public void setId_fichier(int id_fichier) {
this.id_fichier = id_fichier;
}

public Fichier() {
super();
}

}

package com.bfi.webtop.model;

import javax.annotation.Generated;
import javax.persistence.metamodel.StaticMetamodel;

@Generated(value="Dali", date="2013-01-28T10:33:26.416+0100")
@StaticMetamodel(FileSystemElement.class)
public class FileSystemElement_ {
}

at org.eclipse.persistence.internal.jpa.EntityManagerSetupImpl.createDeployFailedPersistenceException(EntityManagerSetupImpl.java:616)
at org.eclipse.persistence.internal.jpa.EntityManagerSetupImpl.deploy(EntityManagerSetupImpl.java:596)
at org.eclipse.persistence.internal.jpa.EntityManagerFactoryDelegate.getDatabaseSession(EntityManagerFactoryDelegate.java:186)
at org.eclipse.persistence.internal.jpa.EntityManagerFactoryDelegate.createEntityManagerImpl(EntityManagerFactoryDelegate.java:278)
at org.eclipse.persistence.internal.jpa.EntityManagerFactoryImpl.createEntityManagerImpl(EntityManagerFactoryImpl.java:304)
at org.eclipse.persistence.internal.jpa.EntityManagerFactoryImpl.createEntityManager(EntityManagerFactoryImpl.java:282)
at org.eclipse.jpt.jpa.eclipselink.core.ddlgen.Main.perform(Main.java:85)
at org.eclipse.jpt.jpa.eclipselink.core.ddlgen.Main.execute(Main.java:76)
at org.eclipse.jpt.jpa.eclipselink.core.ddlgen.Main.main(Main.java:63)
Caused by: Exception [EclipseLink-28019] (Eclipse Persistence Services -       2.4.0.v20120608-r11652): org.eclipse.persistence.exceptions.EntityManagerSetupException

我正在使用Eclipse Juno有什么帮助吗？

}

Answer 1

您已经将类Fichier定义为抽象：

public abstract class Fichier

删除抽象，它就可以工作了。本例中的错误消息有些令人困惑。