GWT strange serialization exception

Question

I have application that calculates 9 statistictics that are stored in complex data structures as HashMap<String, TreeMap<String, Integer>> or even more complex. Every statistic implements interface IStatistic. Results are stored in List<IStatistic> and its size (for largest example) is 3.5MB (I have serialized it manually and put it to the file). When I send results to client sometimes (usually when data size goes over 1.5MB, i.e. when is less than some limit exception does not occur) strange exception occurs and it is never in same place..

I have read and tried every similar solution to the problem that I found here and at GWT official page like:

" https://developers.google.com/web-toolkit/doc/latest/tutorial/RPC http://stackoverflow.com/questions/2122798/gwt-occasional-com-google-gwt-user-client-rpc-serializationexception did you check http://code.google.com/webtoolkit/doc/latest/tutorial/RPC.html#serialize the article says: It has a default (zero argument) constructor with any access modifier (e.g. private Foo(){} will work) I'm allways forgetting zeroargument const. when I am making a serializable object :D "

but nothing really helped. Also tried to debug it but it breaks down somewhere in GWT source and I can't see the source. It is interesting that for smaller data samples everything goes smooth.

I am using GWT 2.4.0. without appengine.

Does anyone had similar problem or has some advice to deal with this?

Here are some example exceptions:
    FIRST EXAMPLE:
    com.google.gwt.user.client.rpc.IncompatibleRemoteServiceException: The response could not be deserialized
        at com.google.gwt.user.client.rpc.impl.RequestCallbackAdapter.onResponseReceived(RequestCallbackAdapter.java:221)
        at com.google.gwt.http.client.Request.fireOnResponseReceived(Request.java:287)
        at com.google.gwt.http.client.RequestBuilder$1.onReadyStateChange(RequestBuilder.java:395)
        at sun.reflect.GeneratedMethodAccessor52.invoke(Unknown Source)
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
        at java.lang.reflect.Method.invoke(Unknown Source)
        at com.google.gwt.dev.shell.MethodAdaptor.invoke(MethodAdaptor.java:103)
        at com.google.gwt.dev.shell.MethodDispatch.invoke(MethodDispatch.java:71)
        at com.google.gwt.dev.shell.OophmSessionHandler.invoke(OophmSessionHandler.java:172)
        at com.google.gwt.dev.shell.BrowserChannelServer.reactToMessagesWhileWaitingForReturn(BrowserChannelServer.java:337)
        at com.google.gwt.dev.shell.BrowserChannelServer.invokeJavascript(BrowserChannelServer.java:218)
        at com.google.gwt.dev.shell.ModuleSpaceOOPHM.doInvoke(ModuleSpaceOOPHM.java:136)
        at com.google.gwt.dev.shell.ModuleSpace.invokeNative(ModuleSpace.java:561)
        at com.google.gwt.dev.shell.ModuleSpace.invokeNativeObject(ModuleSpace.java:269)
        at com.google.gwt.dev.shell.JavaScriptHost.invokeNativeObject(JavaScriptHost.java:91)
        at com.google.gwt.core.client.impl.Impl.apply(Impl.java)
        at com.google.gwt.core.client.impl.Impl.entry0(Impl.java:213)
        at sun.reflect.GeneratedMethodAccessor32.invoke(Unknown Source)
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
        at java.lang.reflect.Method.invoke(Unknown Source)
        at com.google.gwt.dev.shell.MethodAdaptor.invoke(MethodAdaptor.java:103)
        at com.google.gwt.dev.shell.MethodDispatch.invoke(MethodDispatch.java:71)
        at com.google.gwt.dev.shell.OophmSessionHandler.invoke(OophmSessionHandler.java:172)
        at com.google.gwt.dev.shell.BrowserChannelServer.reactToMessages(BrowserChannelServer.java:292)
        at com.google.gwt.dev.shell.BrowserChannelServer.processConnection(BrowserChannelServer.java:546)
        at com.google.gwt.dev.shell.BrowserChannelServer.run(BrowserChannelServer.java:363)
        at java.lang.Thread.run(Unknown Source)
    Caused by: com.google.gwt.user.client.rpc.SerializationException: 2AS (6) 
        at com.google.gwt.user.client.rpc.impl.SerializerBase.getTypeHandler(SerializerBase.java:153)
        at com.google.gwt.user.client.rpc.impl.SerializerBase.instantiate(SerializerBase.java:114)
        at com.google.gwt.user.client.rpc.impl.ClientSerializationStreamReader.deserialize(ClientSerializationStreamReader.java:111)
        at com.google.gwt.user.client.rpc.impl.AbstractSerializationStreamReader.readObject(AbstractSerializationStreamReader.java:119)
        at com.google.gwt.user.client.rpc.core.java.util.Map_CustomFieldSerializerBase.deserialize(Map_CustomFieldSerializerBase.java:38)
        at com.google.gwt.user.client.rpc.core.java.util.TreeMap_CustomFieldSerializer.deserialize(TreeMap_CustomFieldSerializer.java:36)
        at com.google.gwt.user.client.rpc.core.java.util.TreeMap_FieldSerializer.deserial(TreeMap_FieldSerializer.java:15)
        at com.google.gwt.user.client.rpc.impl.SerializerBase.deserialize(SerializerBase.java:95)
        at com.google.gwt.user.client.rpc.impl.ClientSerializationStreamReader.deserialize(ClientSerializationStreamReader.java:113)
        at com.google.gwt.user.client.rpc.impl.AbstractSerializationStreamReader.readObject(AbstractSerializationStreamReader.java:119)
        at com.google.gwt.user.client.rpc.core.java.util.Map_CustomFieldSerializerBase.deserialize(Map_CustomFieldSerializerBase.java:39)
        at com.google.gwt.user.client.rpc.core.java.util.HashMap_CustomFieldSerializer.deserialize(HashMap_CustomFieldSerializer.java:34)
        at com.google.gwt.user.client.rpc.core.java.util.HashMap_FieldSerializer.deserial(HashMap_FieldSerializer.java:19)
        at com.google.gwt.user.client.rpc.impl.SerializerBase.deserialize(SerializerBase.java:95)
        at com.google.gwt.user.client.rpc.impl.ClientSerializationStreamReader.deserialize(ClientSerializationStreamReader.java:113)
        at com.google.gwt.user.client.rpc.impl.AbstractSerializationStreamReader.readObject(AbstractSerializationStreamReader.java:119)
        at hr.fer.zesoi.metals.shared.statistic.result.StatisticM1Result_FieldSerializer.deserialize(StatisticM1Result_FieldSerializer.java:29)
        at hr.fer.zesoi.metals.shared.statistic.result.StatisticM1Result_FieldSerializer.deserial(StatisticM1Result_FieldSerializer.java:51)
        at com.google.gwt.user.client.rpc.impl.SerializerBase.deserialize(SerializerBase.java:95)
        at com.google.gwt.user.client.rpc.impl.ClientSerializationStreamReader.deserialize(ClientSerializationStreamReader.java:113)
        at com.google.gwt.user.client.rpc.impl.AbstractSerializationStreamReader.readObject(AbstractSerializationStreamReader.java:119)
        at com.google.gwt.user.client.rpc.core.java.util.Collection_CustomFieldSerializerBase.deserialize(Collection_CustomFieldSerializerBase.java:34)
        at com.google.gwt.user.client.rpc.core.java.util.ArrayList_CustomFieldSerializer.deserialize(ArrayList_CustomFieldSerializer.java:34)
        at com.google.gwt.user.client.rpc.core.java.util.ArrayList_FieldSerializer.deserial(ArrayList_FieldSerializer.java:19)
        at com.google.gwt.user.client.rpc.impl.SerializerBase.deserialize(SerializerBase.java:95)
        at com.google.gwt.user.client.rpc.impl.ClientSerializationStreamReader.deserialize(ClientSerializationStreamReader.java:113)
        at com.google.gwt.user.client.rpc.impl.AbstractSerializationStreamReader.readObject(AbstractSerializationStreamReader.java:119)
        at com.google.gwt.user.client.rpc.impl.RequestCallbackAdapter$ResponseReader$8.read(RequestCallbackAdapter.java:106)
        at com.google.gwt.user.client.rpc.impl.RequestCallbackAdapter.onResponseReceived(RequestCallbackAdapter.java:214)
        ... 26 more



SECOND EXAMPLE:
com.google.gwt.dev.shell.HostedModeException: Something other than an int was returned from JSNI method '@com.google.gwt.user.client.rpc.impl.ClientSerializationStreamReader::readInt()': JS value of type string, expected int
    at com.google.gwt.dev.shell.JsValueGlue.getIntRange(JsValueGlue.java:266)
    at com.google.gwt.dev.shell.JsValueGlue.get(JsValueGlue.java:144)
    at com.google.gwt.dev.shell.ModuleSpace.invokeNativeInt(ModuleSpace.java:247)
    at com.google.gwt.dev.shell.JavaScriptHost.invokeNativeInt(JavaScriptHost.java:75)
    at com.google.gwt.user.client.rpc.impl.ClientSerializationStreamReader.readInt(ClientSerializationStreamReader.java)
    at com.google.gwt.user.client.rpc.impl.ClientSerializationStreamReader.readString(ClientSerializationStreamReader.java:104)
    at com.google.gwt.user.client.rpc.core.java.lang.String_CustomFieldSerializer.instantiate(String_CustomFieldSerializer.java:37)
    at com.google.gwt.user.client.rpc.core.java.lang.String_FieldSerializer.create(String_FieldSerializer.java:11)
    at com.google.gwt.user.client.rpc.impl.SerializerBase.instantiate(SerializerBase.java:115)
    at com.google.gwt.user.client.rpc.impl.ClientSerializationStreamReader.deserialize(ClientSerializationStreamReader.java:111)
    at com.google.gwt.user.client.rpc.impl.AbstractSerializationStreamReader.readObject(AbstractSerializationStreamReader.java:119)
    at com.google.gwt.user.client.rpc.core.java.util.Collection_CustomFieldSerializerBase.deserialize(Collection_CustomFieldSerializerBase.java:34)
    at com.google.gwt.user.client.rpc.core.java.util.TreeSet_CustomFieldSerializer.deserialize(TreeSet_CustomFieldSerializer.java:36)
    at com.google.gwt.user.client.rpc.core.java.util.TreeSet_FieldSerializer.deserial(TreeSet_FieldSerializer.java:15)
    at com.google.gwt.user.client.rpc.impl.SerializerBase.deserialize(SerializerBase.java:95)
    at com.google.gwt.user.client.rpc.impl.ClientSerializationStreamReader.deserialize(ClientSerializationStreamReader.java:113)
    at com.google.gwt.user.client.rpc.impl.AbstractSerializationStreamReader.readObject(AbstractSerializationStreamReader.java:119)
    at com.google.gwt.user.client.rpc.core.java.util.Map_CustomFieldSerializerBase.deserialize(Map_CustomFieldSerializerBase.java:39)
    at com.google.gwt.user.client.rpc.core.java.util.HashMap_CustomFieldSerializer.deserialize(HashMap_CustomFieldSerializer.java:34)
    at com.google.gwt.user.client.rpc.core.java.util.HashMap_FieldSerializer.deserial(HashMap_FieldSerializer.java:19)
    at com.google.gwt.user.client.rpc.impl.SerializerBase.deserialize(SerializerBase.java:95)
    at com.google.gwt.user.client.rpc.impl.ClientSerializationStreamReader.deserialize(ClientSerializationStreamReader.java:113)
    at com.google.gwt.user.client.rpc.impl.AbstractSerializationStreamReader.readObject(AbstractSerializationStreamReader.java:119)
    at hr.fer.zesoi.metals.shared.statistic.IStatisticResult_FieldSerializer.deserialize(IStatisticResult_FieldSerializer.java:13)
    at hr.fer.zesoi.metals.shared.statistic.result.StatisticM2Result_FieldSerializer.deserialize(StatisticM2Result_FieldSerializer.java:22)
    at hr.fer.zesoi.metals.shared.statistic.result.StatisticM2Result_FieldSerializer.deserial(StatisticM2Result_FieldSerializer.java:40)
    at com.google.gwt.user.client.rpc.impl.SerializerBase.deserialize(SerializerBase.java:95)
    at com.google.gwt.user.client.rpc.impl.ClientSerializationStreamReader.deserialize(ClientSerializationStreamReader.java:113)
    at com.google.gwt.user.client.rpc.impl.AbstractSerializationStreamReader.readObject(AbstractSerializationStreamReader.java:119)
    at com.google.gwt.user.client.rpc.core.java.util.Collection_CustomFieldSerializerBase.deserialize(Collection_CustomFieldSerializerBase.java:34)
    at com.google.gwt.user.client.rpc.core.java.util.ArrayList_CustomFieldSerializer.deserialize(ArrayList_CustomFieldSerializer.java:34)
    at com.google.gwt.user.client.rpc.core.java.util.ArrayList_FieldSerializer.deserial(ArrayList_FieldSerializer.java:19)
    at com.google.gwt.user.client.rpc.impl.SerializerBase.deserialize(SerializerBase.java:95)
    at com.google.gwt.user.client.rpc.impl.ClientSerializationStreamReader.deserialize(ClientSerializationStreamReader.java:113)
    at com.google.gwt.user.client.rpc.impl.AbstractSerializationStreamReader.readObject(AbstractSerializationStreamReader.java:119)
    at com.google.gwt.user.client.rpc.impl.RequestCallbackAdapter$ResponseReader$8.read(RequestCallbackAdapter.java:106)
    at com.google.gwt.user.client.rpc.impl.RequestCallbackAdapter.onResponseReceived(RequestCallbackAdapter.java:214)
    at com.google.gwt.http.client.Request.fireOnResponseReceived(Request.java:287)
    at com.google.gwt.http.client.RequestBuilder$1.onReadyStateChange(RequestBuilder.java:395)
    at sun.reflect.GeneratedMethodAccessor37.invoke(Unknown Source)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
    at java.lang.reflect.Method.invoke(Unknown Source)
    at com.google.gwt.dev.shell.MethodAdaptor.invoke(MethodAdaptor.java:103)
    at com.google.gwt.dev.shell.MethodDispatch.invoke(MethodDispatch.java:71)
    at com.google.gwt.dev.shell.OophmSessionHandler.invoke(OophmSessionHandler.java:172)
    at com.google.gwt.dev.shell.BrowserChannelServer.reactToMessagesWhileWaitingForReturn(BrowserChannelServer.java:337)
    at com.google.gwt.dev.shell.BrowserChannelServer.invokeJavascript(BrowserChannelServer.java:218)
    at com.google.gwt.dev.shell.ModuleSpaceOOPHM.doInvoke(ModuleSpaceOOPHM.java:136)
    at com.google.gwt.dev.shell.ModuleSpace.invokeNative(ModuleSpace.java:561)
    at com.google.gwt.dev.shell.ModuleSpace.invokeNativeObject(ModuleSpace.java:269)
    at com.google.gwt.dev.shell.JavaScriptHost.invokeNativeObject(JavaScriptHost.java:91)
    at com.google.gwt.core.client.impl.Impl.apply(Impl.java)
    at com.google.gwt.core.client.impl.Impl.entry0(Impl.java:213)
    at sun.reflect.GeneratedMethodAccessor32.invoke(Unknown Source)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
    at java.lang.reflect.Method.invoke(Unknown Source)
    at com.google.gwt.dev.shell.MethodAdaptor.invoke(MethodAdaptor.java:103)
    at com.google.gwt.dev.shell.MethodDispatch.invoke(MethodDispatch.java:71)
    at com.google.gwt.dev.shell.OophmSessionHandler.invoke(OophmSessionHandler.java:172)
    at com.google.gwt.dev.shell.BrowserChannelServer.reactToMessages(BrowserChannelServer.java:292)
    at com.google.gwt.dev.shell.BrowserChannelServer.processConnection(BrowserChannelServer.java:546)
    at com.google.gwt.dev.shell.BrowserChannelServer.run(BrowserChannelServer.java:363)
    at java.lang.Thread.run(Unknown Source)


THIRD EXAMPLE:

    java.lang.NullPointerException
    at java.util.TreeMap.put(Unknown Source)
    at java.util.TreeSet.add(Unknown Source)
    at com.google.gwt.user.client.rpc.core.java.util.Collection_CustomFieldSerializerBase.deserialize(Collection_CustomFieldSerializerBase.java:35)
    at com.google.gwt.user.client.rpc.core.java.util.TreeSet_CustomFieldSerializer.deserialize(TreeSet_CustomFieldSerializer.java:36)
    at com.google.gwt.user.client.rpc.core.java.util.TreeSet_FieldSerializer.deserial(TreeSet_FieldSerializer.java:15)
    at com.google.gwt.user.client.rpc.impl.SerializerBase.deserialize(SerializerBase.java:95)
    at com.google.gwt.user.client.rpc.impl.ClientSerializationStreamReader.deserialize(ClientSerializationStreamReader.java:113)
    at com.google.gwt.user.client.rpc.impl.AbstractSerializationStreamReader.readObject(AbstractSerializationStreamReader.java:119)
    at com.google.gwt.user.client.rpc.core.java.util.Map_CustomFieldSerializerBase.deserialize(Map_CustomFieldSerializerBase.java:39)
    at com.google.gwt.user.client.rpc.core.java.util.HashMap_CustomFieldSerializer.deserialize(HashMap_CustomFieldSerializer.java:34)
    at com.google.gwt.user.client.rpc.core.java.util.HashMap_FieldSerializer.deserial(HashMap_FieldSerializer.java:19)
    at com.google.gwt.user.client.rpc.impl.SerializerBase.deserialize(SerializerBase.java:95)
    at com.google.gwt.user.client.rpc.impl.ClientSerializationStreamReader.deserialize(ClientSerializationStreamReader.java:113)
    at com.google.gwt.user.client.rpc.impl.AbstractSerializationStreamReader.readObject(AbstractSerializationStreamReader.java:119)
    at hr.fer.zesoi.metals.shared.statistic.IStatisticResult_FieldSerializer.deserialize(IStatisticResult_FieldSerializer.java:13)
    at hr.fer.zesoi.metals.shared.statistic.result.StatisticM4Result_FieldSerializer.deserialize(StatisticM4Result_FieldSerializer.java:44)
    at hr.fer.zesoi.metals.shared.statistic.result.StatisticM4Result_FieldSerializer.deserial(StatisticM4Result_FieldSerializer.java:66)
    at com.google.gwt.user.client.rpc.impl.SerializerBase.deserialize(SerializerBase.java:95)
    at com.google.gwt.user.client.rpc.impl.ClientSerializationStreamReader.deserialize(ClientSerializationStreamReader.java:113)
    at com.google.gwt.user.client.rpc.impl.AbstractSerializationStreamReader.readObject(AbstractSerializationStreamReader.java:119)
    at com.google.gwt.user.client.rpc.core.java.util.Collection_CustomFieldSerializerBase.deserialize(Collection_CustomFieldSerializerBase.java:34)
    at com.google.gwt.user.client.rpc.core.java.util.ArrayList_CustomFieldSerializer.deserialize(ArrayList_CustomFieldSerializer.java:34)
    at com.google.gwt.user.client.rpc.core.java.util.ArrayList_FieldSerializer.deserial(ArrayList_FieldSerializer.java:19)
    at com.google.gwt.user.client.rpc.impl.SerializerBase.deserialize(SerializerBase.java:95)
    at com.google.gwt.user.client.rpc.impl.ClientSerializationStreamReader.deserialize(ClientSerializationStreamReader.java:113)
    at com.google.gwt.user.client.rpc.impl.AbstractSerializationStreamReader.readObject(AbstractSerializationStreamReader.java:119)
    at com.google.gwt.user.client.rpc.impl.RequestCallbackAdapter$ResponseReader$8.read(RequestCallbackAdapter.java:106)
    at com.google.gwt.user.client.rpc.impl.RequestCallbackAdapter.onResponseReceived(RequestCallbackAdapter.java:214)
    at com.google.gwt.http.client.Request.fireOnResponseReceived(Request.java:287)
    at com.google.gwt.http.client.RequestBuilder$1.onReadyStateChange(RequestBuilder.java:395)
    at sun.reflect.GeneratedMethodAccessor47.invoke(Unknown Source)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
    at java.lang.reflect.Method.invoke(Unknown Source)
    at com.google.gwt.dev.shell.MethodAdaptor.invoke(MethodAdaptor.java:103)
    at com.google.gwt.dev.shell.MethodDispatch.invoke(MethodDispatch.java:71)
    at com.google.gwt.dev.shell.OophmSessionHandler.invoke(OophmSessionHandler.java:172)
    at com.google.gwt.dev.shell.BrowserChannelServer.reactToMessagesWhileWaitingForReturn(BrowserChannelServer.java:337)
    at com.google.gwt.dev.shell.BrowserChannelServer.invokeJavascript(BrowserChannelServer.java:218)
    at com.google.gwt.dev.shell.ModuleSpaceOOPHM.doInvoke(ModuleSpaceOOPHM.java:136)
    at com.google.gwt.dev.shell.ModuleSpace.invokeNative(ModuleSpace.java:561)
    at com.google.gwt.dev.shell.ModuleSpace.invokeNativeObject(ModuleSpace.java:269)
    at com.google.gwt.dev.shell.JavaScriptHost.invokeNativeObject(JavaScriptHost.java:91)
    at com.google.gwt.core.client.impl.Impl.apply(Impl.java)
    at com.google.gwt.core.client.impl.Impl.entry0(Impl.java:213)
    at sun.reflect.GeneratedMethodAccessor42.invoke(Unknown Source)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
    at java.lang.reflect.Method.invoke(Unknown Source)
    at com.google.gwt.dev.shell.MethodAdaptor.invoke(MethodAdaptor.java:103)
    at com.google.gwt.dev.shell.MethodDispatch.invoke(MethodDispatch.java:71)
    at com.google.gwt.dev.shell.OophmSessionHandler.invoke(OophmSessionHandler.java:172)
    at com.google.gwt.dev.shell.BrowserChannelServer.reactToMessages(BrowserChannelServer.java:292)
    at com.google.gwt.dev.shell.BrowserChannelServer.processConnection(BrowserChannelServer.java:546)
    at com.google.gwt.dev.shell.BrowserChannelServer.run(BrowserChannelServer.java:363)
    at java.lang.Thread.run(Unknown Source)

score 2 · Accepted Answer · answered Apr 28 '12 at 20:50

For the first error, this almost certainly indicates that your server and client fell out of sync, and have a different view of what can be serialized and deserialized. Clearing the browser cache, or making sure that the server is running the same code as the client ( by redeploying to the server if running from google's appengine server, or restarting if running locally). From the string "2AS" it looks like you might be obfuscating type names - consider disabling that feature until you get this worked out for sure.

Second error:

com.google.gwt.dev.shell.HostedModeException: Something other than an int was returned from JSNI method '@com.google.gwt.user.client.rpc.impl.ClientSerializationStreamReader::readInt()': JS value of type string, expected int
at com.google.gwt.dev.shell.JsValueGlue.getIntRange(JsValueGlue.java:266)
at com.google.gwt.dev.shell.JsValueGlue.get(JsValueGlue.java:144)
at com.google.gwt.dev.shell.ModuleSpace.invokeNativeInt(ModuleSpace.java:247)
at com.google.gwt.dev.shell.JavaScriptHost.invokeNativeInt(JavaScriptHost.java:75)

Fortunatly, this is a known issue in Chrome+Dev mode. It will not occur in other browsers, and it will not occur in Chrome in web mode. Using a different browser is the easiest way to avoid this - any code which runs a lot of JSNI code (any RPC code for example) will eventually run into this.

java.lang.NullPointerException
at java.util.TreeMap.put(Unknown Source)
at java.util.TreeSet.add(Unknown Source)
at com.google.gwt.user.client.rpc.core.java.util.Collection_CustomFieldSerializerBase.deserialize(Collection_CustomFieldSerializerBase.java:35)
at com.google.gwt.user.client.rpc.core.java.util.TreeSet_CustomFieldSerializer.deserialize(TreeSet_CustomFieldSerializer.java:36)
at com.google.gwt.user.client.rpc.core.java.util.TreeSet_FieldSerializer.deserial(TreeSet_FieldSerializer.java:15)

This is occurring in this code:

@SuppressWarnings("unchecked")
public final class Collection_CustomFieldSerializerBase {

  public static void deserialize(SerializationStreamReader streamReader,
      Collection instance) throws SerializationException {
    int size = streamReader.readInt();
    for (int i = 0; i < size; ++i) {
      Object obj = streamReader.readObject();
      instance.add(obj); //line 35
    }
  }

This suggests that obj is null at that line, and that you are maybe adding some null object to the TreeSet (within the TreeMap I'd imagine). Might be worth setting a breakpoint in that class, conditional on obj being null to establish if that is why, and if so, how to nail it down.

thank you very much on detailed explanations of exceptions! I have managed to fix my application..thank you! :)) — user1362565, Apr 29 '12 at 09:10

GWT strange serialization exception

1 Answers1