JDO getObjectById return null, why?

Question

I just started using JDO and Google datastore

I have File class that contains code below for primary key.

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

When I call this method, using ID/Name value in datastore, it gave me error - javax.jdo.JDOObjectNotFoundException: Could not retrieve entity of kind File with key File("6298002603900928").
But when I use Key value which in datastore, it returns the expected File object

ID/Name value is 6298002603900928
Key value is agxvcmdhbml6ZS1mcHZyEQsSBEZpbGUYgICAgICAmAsM

File file = null;
// get data from Google datastore
PersistenceManager pm = PMF.get().getPersistenceManager();
try {
    file = pm.getObjectById(File.class, fileId);
} catch (JDOObjectNotFoundException e) {
    e.printStackTrace();
}

How do I solve this problem?

I tried to convert ID/Name to Key by using this code

Key key = KeyFactory.stringToKey(fileId);

But it also gave me error java.lang.IllegalArgumentException: Invalid Key PB: no elements.

Answer 1

I found out why is there error.

fileId that I used is String. It is suppose to be Long.