Selecting Entity based on auto generated ID in google datastore

问题

I have created an entity with few attributes but without specifying any key in which case an auto generated ID has been created in data-store.

     Entity en=new Entity("Job");

Now when I fetch such entities and try to store it in Java object, how can I get the auto generated ID (which I required to perform UPDATE operation later)? I have tried the below ways but it does not return Identifier value.

     en.getProperty("__key__");
     en.getProperty("ID/Name");
     en.getProperty("Key");

回答1:

You are probably looking for:

en.getProperty(Entity.KEY_RESERVED_PROPERTY)

mentioned in Key Filters (not an obvious place to find it).

Another approach would be to try:

en.getKey().getId()

mentioned in Entity JavaDoc and Key JavaDoc.

来源：https://stackoverflow.com/questions/22268257/selecting-entity-based-on-auto-generated-id-in-google-datastore