坚持对象列表 [英] Persist List of objects
问题描述
我得到这个
javax.jdo.JDOFatalUserException:元数据中的错误don.Comment.id:不能有一个java.lang.String主键并且是一个子对象(拥有字段是don.Post.comments)。
NestedThrowables:
运行我的grails + app-engine webapp时
我该如何解决这个问题?
class Comment.groovy
import javax.jdo.annotations。*;
@PersistenceCapable(identityType = IdentityType.APPLICATION,detachable =true)
class注释实现Serializable {
@PrimaryKey
@Persistent(valueStrategy = IdGeneratorStrategy.IDENTITY)
字符串标识
@Persistent(mappedBy =comments)
发帖
@Persistent
字符串名
@Persistent
字符串电子邮件
@持续
字符串url
静态约束= {
id(可见:false)
}
}
类Post.groovy
@PersistenceCapable(identityType = IdentityType.APPLICATION,detachable =true)
class Post实现Serializable {
@PrimaryKey
@Persistent(valueStrategy = IdGeneratorStrategy.IDENTITY)
Long id
@Persistent
String title
@Persistent
字符串内容
// static hasMany = [comments:Comment]
@Persistent(defaultFetchGroup =true)
评论评论
静态约束= {
id(visible:false)
}
}
对于子类,主键必须是com.google.appengine.api.datastore.Key值(或者编码为字符串),请参阅 http://code.google.com/appengine/docs/java/datastore/creatinggettinganddeletingdata.html#Keys
I got this "javax.jdo.JDOFatalUserException: Error in meta-data for don.Comment.id: Cannot have a java.lang.String primary key and be a child object (owning field is don.Post.comments). NestedThrowables:"
when running my grails + app-engine webapp
How can I fix this?
class Comment.groovy
import javax.jdo.annotations.*;
@PersistenceCapable(identityType = IdentityType.APPLICATION, detachable="true")
class Comment implements Serializable {
@PrimaryKey
@Persistent(valueStrategy = IdGeneratorStrategy.IDENTITY)
String id
@Persistent(mappedBy="comments")
Post post
@Persistent
String name
@Persistent
String email
@Persistent
String url
static constraints = {
id( visible:false)
}
}
class Post.groovy
@PersistenceCapable(identityType = IdentityType.APPLICATION, detachable="true")
class Post implements Serializable {
@PrimaryKey
@Persistent(valueStrategy = IdGeneratorStrategy.IDENTITY)
Long id
@Persistent
String title
@Persistent
String content
//static hasMany = [comments:Comment]
@Persistent(defaultFetchGroup = "true")
Comment comments
static constraints = {
id( visible:false)
}
}
For child classes the primary key has to be a com.google.appengine.api.datastore.Key value (or encoded as a string) see http://code.google.com/appengine/docs/java/datastore/creatinggettinganddeletingdata.html#Keys
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