Java 如何在google App Engine\u ah/api/explorer中创建com.google.appengine.api.datastore.Key对象？

我有一个GAE JDO注释对象：

@PersistenceCapable
public class HelloGreeting {

  @PrimaryKey
  @Persistent(valueStrategy = IdGeneratorStrategy.IDENTITY)
  private Key id;

  @Persistent
  private String message;

  ... constructors, getters, setters
}

还有我自己的终点：

public HelloGreeting update(HelloGreeting helloGreeting)
        throws NotFoundException {
    PersistenceManager pm = PMF.get().getPersistenceManager();
    try {
        pm.getObjectById(HelloGreeting.class, helloGreeting.getId());
        ... some logic
    } finally {
        pm.close();
    }
    return helloGreeting;
}

public HelloGreeting update(HelloGreeting helloGreeting)
        throws NotFoundException {
    PersistenceManager pm = PMF.get().getPersistenceManager();
    try {
        if(!containsGreeting(helloGreeting)) {
            throw new NotFoundException("not exists");
        }
        // persisting the helloGreeting with the new Key
        pm.makePersistent(helloGreeting);
    } finally {
        pm.close();
    }
    return helloGreeting;
}

private boolean containsGreeting(HelloGreeting helloGreeting) {
    PersistenceManager pm = PMF.get().getPersistenceManager();
    boolean contains = true;
    try {
        // here I'm creating a new Key from the helloGreeting
        Key key = KeyFactory.createKey(HelloGreeting.class.getSimpleName(), helloGreeting.getId().getId());
        // using the Key for a query
        pm.getObjectById(HelloGreeting.class, key);
        // and rewriting the old incorrect unmarshalled Key by the new one 
        helloGreeting.setId(key);
    } catch (javax.jdo.JDOObjectNotFoundException ex) {
        contains = false;
    } finally {
        pm.close();
    }
    return contains;
}

我想从前端或谷歌应用程序引擎发送helloGreeting对象

当我使用pm.makePersistenthelloGreeting；创建一个时；，然后api资源管理器向我显示如下内容：

{
 "id": {
   "kind": "HelloGreeting",
   "appId": "project-id",
   "id": "5629499534213120",
   "complete": true
  },
"message": "some text"
}

然后，我使用此JSON结构通过api资源管理器调用updateHelloGreeting helloGreeting方法，得到以下错误：

java.lang.NullPointerException at com.google.appengine.api.datastore.Key.getAppId(Key.java:279)
...
...

。。。这是因为行pm.getObjectByIdHelloGreeting.class，helloGreeting.getId；在我的updateHelloGreeting helloGreeting方法中

私钥id字段似乎未正确解组。 我还用pm.getObjectByIdHelloGreeting.class、helloGreeting.getId.getId尝试了它；但是没有成功

谁能告诉我这是否可能

---

PS：我不能将id字段的类型从Key改为Long，因为这样我就不会使用带有@PersistenceCapable注释的内部子对象。

我对您的情况不是100%确定，但我认为您可能需要编写一个自定义项来确保正确地重构密钥。

我用一个有点讨厌的解决方案解决了这个问题。这是我的更新端点：

public HelloGreeting update(HelloGreeting helloGreeting)
        throws NotFoundException {
    PersistenceManager pm = PMF.get().getPersistenceManager();
    try {
        pm.getObjectById(HelloGreeting.class, helloGreeting.getId());
        ... some logic
    } finally {
        pm.close();
    }
    return helloGreeting;
}

public HelloGreeting update(HelloGreeting helloGreeting)
        throws NotFoundException {
    PersistenceManager pm = PMF.get().getPersistenceManager();
    try {
        if(!containsGreeting(helloGreeting)) {
            throw new NotFoundException("not exists");
        }
        // persisting the helloGreeting with the new Key
        pm.makePersistent(helloGreeting);
    } finally {
        pm.close();
    }
    return helloGreeting;
}

private boolean containsGreeting(HelloGreeting helloGreeting) {
    PersistenceManager pm = PMF.get().getPersistenceManager();
    boolean contains = true;
    try {
        // here I'm creating a new Key from the helloGreeting
        Key key = KeyFactory.createKey(HelloGreeting.class.getSimpleName(), helloGreeting.getId().getId());
        // using the Key for a query
        pm.getObjectById(HelloGreeting.class, key);
        // and rewriting the old incorrect unmarshalled Key by the new one 
        helloGreeting.setId(key);
    } catch (javax.jdo.JDOObjectNotFoundException ex) {
        contains = false;
    } finally {
        pm.close();
    }
    return contains;
}

---

如果有人知道更好的解决方案，我将不胜感激。

我害怕这个答案：D