Lambdas and serialization

[Nathan Bryant]

Hi Rémi,

If lambdas are to be SAM converted then users will find it a surprising limitation that the resulting SAM instance does not have the same capabilities as a regular SAM; it leads to an irregularity in the language. Any implementation choice that precludes serialization should be considered an implementation bug.

-----Original Message-----
From: lambda-dev-bounces at openjdk.java.net [mailto:lambda-dev-bounces at openjdk.java.net] On Behalf Of Rémi Forax
Sent: Tuesday, October 19, 2010 11:44 AM
To: lambda-dev at openjdk.java.net
Subject: Re: Lambdas and serialization

Le 19/10/2010 16:10, Maurizio Cimadamore a écrit :
> On 19/10/10 14:41, Alessio Stalla wrote:
>    
>> On Tue, Oct 19, 2010 at 3:30 PM, Paul Benedict<pbenedict at apache.org>   wrote:
>>
>>      
>>> Will the wrapper be serializable if the SAM interface is? That's a
>>> good question, but I imagine it has to be because it is implementing
>>> the interface.
>>>
>>> public interface MySamType extends Serializable {
>>>    void doSomething(int x);
>>> }
>>>
>>>        
>> Sorry, I was unclear with the expression "be serializable": what I
>> really meant is not if it will merely implement java.io.Serializable,
>> rather if it will actually be serialized by an ObjectOutputStream
>> without any exception in all cases where a "regular" instance of the
>> SAM would have been serialized without exceptions, and deserialized in
>> the same conditions as well. That's imho a desirable feature to have,
>> but it places a possibly non-trivial burden on the implementation.
>>
>>
>>      
> Good point. The short answer to this question is: it depends on how
> lambda expressions are translated by the compiler. If the compiler uses
> anonymous inner classes to translate away lambda expression, then the
> answer is yes. If lambda expressions are to be translated away by using
> method handles, then I *guess* the answer is no, as it seems like
> MethodHandle are not serializable (Remi or John might know more about
> this though).
>
> Maurizio
>    

Lambda are not serializable, like java.lang.reflect.Method
because it will create tons of security holes.

BTW, inner classes have some trouble with serialUID.

Rémi