[chain] ContextBase throws NotSerializable exception for PropertyDescriptor

• Key: CHAIN-12
• Type: Bug
• Status: Open
• Priority: Major
• Assignee: Unassigned
• Reporter: Jeff Ramsdale
• Affects Version/s: 1.0

Environment

Operating System: other
Platform: Other

Description

It seems ContextBase is intended to be serializable (
http://jakarta.apache.org/commons/chain/apidocs/serialized-form.html &
http://marc.10east.com/?l=jakarta-commons-user&m=111323289317819&w=2 ), but an
attempt to serialize a simple subclass throws the following:

java.io.NotSerializableException: java.beans.PropertyDescriptor
at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1054)
at java.io.ObjectOutputStream.writeObject(ObjectOutputStream.java:278)
at java.util.HashMap.writeObject(HashMap.java:978)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
at
sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:324)
at java.io.ObjectStreamClass.invokeWriteObject(ObjectStreamClass.java:809)
at java.io.ObjectOutputStream.writeSerialData(ObjectOutputStream.java:1296)
at java.io.ObjectOutputStream.writeOrdinaryObject(ObjectOutputStream.java:1247)
at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1052)
at java.io.ObjectOutputStream.defaultWriteFields(ObjectOutputStream.java:1332)
at java.io.ObjectOutputStream.writeSerialData(ObjectOutputStream.java:1304)
at java.io.ObjectOutputStream.writeOrdinaryObject(ObjectOutputStream.java:1247)
at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1052)
at java.io.ObjectOutputStream.defaultWriteFields(ObjectOutputStream.java:1332)
at java.io.ObjectOutputStream.writeSerialData(ObjectOutputStream.java:1304)
at java.io.ObjectOutputStream.writeOrdinaryObject(ObjectOutputStream.java:1247)
at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1052)
at java.io.ObjectOutputStream.writeObject(ObjectOutputStream.java:278)
at
net.sourceforge.cruisecontrol.ProjectTest.testDeserialization(ProjectTest.java:371)

<snip />

Comments

Fixed in nightly build 20050417, and added a unit test to prove that ContextBase
can be serialized and deserialized successfully.

However, there is an issue with the WebContext implementations – they subclass
ContextBase and inherit the "implements Serializable" contract, but they cannot
in fact be serialized because they wrap container objects (request, response,
context) that are not serializable. Therefore, I'm leaving this bug report open
as we explore potential solutions to that issue.

[Joe Germuska]

Why not just mark those container objects as transient?

[Niall Pemberton]

Marking them as transient would get rid of the serialization exception, but unless theres some smart way of getting hold of the wrapped container objects (request, context etc.) when a WebContext implementation is de-serialized then it just moves the problem along.

[Joe Germuska]

I agree that it just moves the problem along, but it seems to me that moving it along is the appropriate response. You can't remove "Serializable" (especially not as long as ContextBase extends HashMap) so you need to leave the responsibility for the wrinkles to users of the library.

What else could be done?

[Rahul Akolkar]

Reminds me of this thread:

http://marc.theaimsgroup.com/?t=113339368800002&r=1&w=2

I do agree with Niall that moving the problem along is probably not the right solution (i.e. a NotSerializableException might still be better than, say, an NPE after subsequent deserialization – from the "if its fatal, die quickly" camp). Perhaps note as a known issue for 1.1?

[Niall Pemberton]

Dennis Lundberg found that TestContextTestCase failed the serialization test with JDK 1.4.2_11 when checking out Chain 1.1 release candidate 1. This test passed with JDK 1.4.2_10 but fails with the later JDK and also JDK 1.3.1_04.

Changing the static "placeholder" object for properties to be Seralizable appears to have fixed this:

http://svn.apache.org/viewvc?view=rev&revision=412150