Hazelcast Serializable Map ClassNotFound Exception

Question

I am trying to implement Hazelcast in a simple web application.

I am trying to store a custom object into my Hazelcast Map and have implemented Serializable in my Bid Object Class with the necessary imports.

import java.io.Serializable;

Here is a snippet of the class object.

public class Bid implements Serializable{

private String bidId;      
private String stock;
private int price;
private String userId;
private Date date;

Here are the syntax as with the tutorial to store the Bid Object into the Map where newBid is a Bid Object.

Config cfg = new Config();
    HazelcastInstance instance = Hazelcast.newHazelcastInstance(cfg);    

Map<String, Bid> mapBids = instance.getMap("bids");
        mapBids.put(newBid.getUserId(), newBid);

My Hazelcast nodes are up and running but when I query the bids map, I get the following error.

com.hazelcast.nio.serialization.HazelcastSerializationException: java.lang.Class
NotFoundException: aa.Bid
        at com.hazelcast.nio.serialization.DefaultSerializers$ObjectSerializer.r
ead(DefaultSerializers.java:190)
        at com.hazelcast.nio.serialization.StreamSerializerAdapter.read(StreamSe
rializerAdapter.java:59)
        at com.hazelcast.nio.serialization.SerializationServiceImpl.toObject(Ser
ializationServiceImpl.java:221)
        at com.hazelcast.spi.impl.NodeEngineImpl.toObject(NodeEngineImpl.java:15
6)
        at com.hazelcast.map.MapService.toObject(MapService.java:773)
        at com.hazelcast.map.proxy.MapProxyImpl.entrySet(MapProxyImpl.java:502)
        at com.hazelcast.examples.TestApp.handleMapEntries(TestApp.java:882)
        at com.hazelcast.examples.TestApp.handleCommand(TestApp.java:371)
        at com.hazelcast.examples.TestApp.start(TestApp.java:187)
        at com.hazelcast.examples.TestApp.main(TestApp.java:1641)

Caused by: java.lang.ClassNotFoundException: aa.Bid
        at java.net.URLClassLoader$1.run(Unknown Source)
        at java.net.URLClassLoader$1.run(Unknown Source)
        at java.security.AccessController.doPrivileged(Native Method)
        at java.net.URLClassLoader.findClass(Unknown Source)
        at java.lang.ClassLoader.loadClass(Unknown Source)
        at sun.misc.Launcher$AppClassLoader.loadClass(Unknown Source)
        at java.lang.ClassLoader.loadClass(Unknown Source)
        at com.hazelcast.nio.ClassLoaderUtil.loadClass(ClassLoaderUtil.java:109)
        at com.hazelcast.nio.IOUtil$1.resolveClass(IOUtil.java:89)
        at java.io.ObjectInputStream.readNonProxyDesc(Unknown Source)
        at java.io.ObjectInputStream.readClassDesc(Unknown Source)
        at java.io.ObjectInputStream.readOrdinaryObject(Unknown Source)
        at java.io.ObjectInputStream.readObject0(Unknown Source)
        at java.io.ObjectInputStream.readObject(Unknown Source)
        at com.hazelcast.nio.serialization.DefaultSerializers$ObjectSerializer.r
ead(DefaultSerializers.java:185)
        ... 9 more

The object class is located in the same folder as my web app with the necessary import syntax but it is not reading it. I have added the CLASSPATH to my Hazelcast jar file as well.

Are there any variable that I have to make Transient in my Bid class object in order for Serializable to work? Or am I missing something?

Answer 1

I was experiencing this same issue using a remote two-node cluster when trying to put an instance of 'MyClass' into the relevant iMap. I was tearing my hair out thinking that I'd need to distribute the jar containing 'MyClass' but realised that the problem was that the definition within hazelcast.xml file was specifying an in-memory-format of OBJECT...

<in-memory-format>OBJECT</in-memory-format>

I changed this value to BINARY and everything started working.

<in-memory-format>BINARY</in-memory-format>

nb. I now have a number of different maps within the cluster, some of which are defined as OBJECT and some as BINARY.

I hope this helps someone out there!