我一直在尝试运行我的GAE代码。 我遇到了使用encodedKey检索用户的问题:
我有这个用户数据管理类,使用singleton PMF管理我所有的CRUD事务。
我的用户使用编码字符串作为密钥:
public class Users implements Serializable {
@PrimaryKey
@Persistent(valueStrategy = IdGeneratorStrategy.IDENTITY)
@Extension(vendorName = "datanucleus", key = "gae.encoded-pk", value = "true")
private String encodedKey;
@Persistent
@Extension(vendorName = "datanucleus", key = "gae.pk-id", value = "true")
private Long keyId;
--- code continues ----
我在 DM 类中有这个 createUser 方法。
public static void createUser(Users user) {
PersistenceManager pm = PMF.get().getPersistenceManager();
try {
Key key = KeyFactory.createKey(Users.class.getSimpleName(),
user.getEmail());
user.setEncodedKey(KeyFactory.keyToString(key));
pm.makePersistent(user);
} catch (Exception e) {
logger.log(Level.SEVERE, e.toString());
} finally {
pm.close();
}
}
问题出在这段检索代码:
public static Users retrieveUser(String encodedKey) {
PersistenceManager pm = PMF.get().getPersistenceManager();
Users user = null;
try {
// Key key = KeyFactory.createKey(Users.class.getSimpleName(),
// user.getEmail());
// I tried recreating the key with user's email, but it does not work either
pm.getObjectById(KeyFactory.stringToKey(encodedKey));
} catch (Exception e) {
logger.severe(e.toString());
} finally {
pm.close();
}
return user;
}
它给我以下错误提示:
SEVERE: javax.jdo.JDOObjectNotFoundException: No such object
FailedObject:Users("t")
NestedThrowables:org.datanucleus.exceptions.NucleusObjectNotFoundException: No such object
"t"是虚拟用户的电子邮件,无论如何。
我如何使用encodedKey通过PMF获取实体? 目前,我只能通过电子邮件和查询进行身份识别,但通过键获取对象应该可以解决问题。
编辑:
我对我的模型对象进行了以下更改:
@PrimaryKey
@Persistent(valueStrategy = IdGeneratorStrategy.IDENTITY)
@Extension(vendorName = "datanucleus", key = "gae.encoded-pk", value = "true")
private String encodedKey;
@Persistent
@Extension(vendorName="datanucleus", key="gae.pk-name", value="true")
private String keyName;
基于此和谷歌的文档:
应用程序可以使用名称为key的键在保存之前填充此值,也可以将其保留为空。如果编码密钥字段为null,则在保存对象时,该字段将使用系统生成的密钥进行填充。
我认为只需持久化此项即可解决问题:
public static void createUser(Users user) {
PersistenceManager pm = PMF.get().getPersistenceManager();
try {
user.setKeyName(user.getEmail());
pm.makePersistent(user);
} catch (Exception e) {
logger.log(Level.SEVERE, e.toString());
} finally {
pm.close();
}
}
但是,没有这样的运气,无论我是否先设置键名,它都会抛出这个错误:
SEVERE: javax.jdo.JDOFatalUserException: Invalid primary key for entity.Users. Cannot have a null primary key field if the field is unencoded and of type String. Please provide a value or, if you want the datastore to generate an id on your behalf, change the type of the field to Long.
NestedThrowables:
org.datanucleus.exceptions.NucleusFatalUserException: Invalid primary key for entity.Users. Cannot have a null primary key field if the field is unencoded and of type String. Please provide a value or, if you want the datastore to generate an id on your behalf, change the type of the field to Long.
我不明白,为什么它没有为我的新实体生成一个新的键?由于所有这些问题,我正在考虑回到Key。我认为使用encodedKey会更具可移植性,因为我正在使用GAE服务器向我的Android客户端提供数据。