AndroidStudio/gradle这个找不到javax.persistence包

Question

在尝试做下面的教程：使用Android工作室

https://cloud.google.com/developers/articles/how-to-build-mobile-app-with-app-engine-backend-tutorial/

，我创建了一个Android Studio项目，并与下面的内容添加CheckIn.java类：

import java.util.Date; 
import com.google.appengine.api.datastore.Key; 
import javax.persistence.Entity; 
import javax.persistence.GeneratedValue; 
import javax.persistence.GenerationType; 
import javax.persistence.Id; 

@Entity 
public class CheckIn { 
@Id 
@GeneratedValue(strategy = GenerationType.IDENTITY) 
private java.security.Key key; 
private String placeId; 
private String userEmail; 
private Date checkinDate; 

public java.security.Key getKey() { 
    return key; 
} 

public String getPlaceId() { 
    return placeId; 
} 
public void setPlaceId(String placeId) { 
    this.placeId = placeId; 
} 

public String getUserEmail() { 
    return userEmail; 
} 
public void setUserEmail(String userEmail) { 
    this.userEmail = userEmail; 
} 

public Date getCheckinDate() { 
    return checkinDate; 
} 
public void setCheckinDate(Date date) { 
    checkinDate = date; 
} 

}

但是当我尝试建立该项目在我的Android Studion/gradle这个项目，我得到以下错误：

Error:(6, 25) error: package javax.persistence does not exist 
Error:(7, 25) error: package javax.persistence does not exist 
Error:(8, 25) error: package javax.persistence does not exist 
Error:(9, 25) error: package javax.persistence does not exist 
Error:(11, 2) error: cannot find symbol class Entity 
Error:(14, 6) error: cannot find symbol class Id 
Error:(15, 6) error: cannot find symbol class GeneratedValue 
Error:(6, 25) error: package javax.persistence does not exist 
Error:(7, 25) error: package javax.persistence does not exist 
Error:(8, 25) error: package javax.persistence does not exist 
Error:(9, 25) error: package javax.persistence does not exist 
Error:(11, 2) error: cannot find symbol class Entity 
Error:(14, 6) error: cannot find symbol class Id 
Error:(15, 6) error: cannot find symbol class GeneratedValue 

Answer 1

当我加入这让固定：

compile group: 'javax.persistence', name: 'persistence-api', version: '1.0' 

我gradle这个依赖。如所述here。