GAE/J Memcache : Cannot use as a key

Question

Keys and values can be of any Serializable type or class

I use MultiKey as the key but after update my app, it gives me exception:

java.lang.IllegalArgumentException: Cannot use as a key: 'MultiKey[class com.xx.xx.xx, Key<?>(Domain("xxx.com")/AppUser(2001)), -1, {}, [-lastModified, ]]'
    at com.google.appengine.api.memcache.AsyncMemcacheServiceImpl.makePbKey(AsyncMemcacheServiceImpl.java:251)
    at com.google.appengine.api.memcache.AsyncMemcacheServiceImpl.doGet(AsyncMemcacheServiceImpl.java:294)
    at com.google.appengine.api.memcache.AsyncMemcacheServiceImpl.get(AsyncMemcacheServiceImpl.java:306)
    at com.google.appengine.api.memcache.MemcacheServiceImpl.get(MemcacheServiceImpl.java:49)

MultiKey is from apache commons-collections, which did implement Serializable

public class MultiKey
extends java.lang.Object
implements java.io.Serializable

Any ideas?

Thanks.

EDIT, the code is like below:

MemcacheService ms = MemcacheServiceFactory.getMemcacheService();
MultiKey key=new MultiKey(xx, xx, xx...);
ms.put( key, value );
...

Any other details? For example: code? – Ian Marshall Dec 16 '12 at 14:44 — Ian Marshall, Dec 16 '12 at 14:44
The code is pretty straightforward, see my edit above. – Mike Dec 16 '12 at 16:47 — Mike, Dec 16 '12 at 16:47

score 0 · Answer 1 · answered Dec 17 '12 at 12:40

Maybe i got the idea, below is how gae serialize the key, it just write the object to byte array, so if one of the objects contained in the key(MultiKey in my situation) did not implement Serializable, this method will not work and throw exception, which is just my case.

     } else if (value instanceof Serializable) {
          flags = Flag.OBJECT;
          ByteArrayOutputStream baos = new ByteArrayOutputStream();
          ObjectOutputStream objOut = new ObjectOutputStream(baos);
          objOut.writeObject(value);
          objOut.close();
          bytes = baos.toByteArray();
     }

GAE/J Memcache : Cannot use as a key

1 Answers1