On 20/10/2011, at 5:19 PM, Mark Struberg wrote:
They must have at least 1 non-private ct (this includes the default
ct). And if it does have a parameter, then it must be annotated with @Inject.
This is perfectly enough to create a proxy. Of course this @Inject constructor must not
get called while creating the proxy itself (because this might contain certain checks and
logic). In this very case a default-ct must get added to the proxy-subclass via byte code
That does not really work, according to the JVM spec:
4.8.2 Structural Constraints - "Each instance initialization method (§3.9), except
for the instance initialization method derived from the constructor of class Object, must
call either another instance initialization method of this or an instance initialization
method of its direct superclass super before its instance members are accessed. However,
instance fields of this that are declared in the current class may be assigned before
calling any instance initialization method."
So even if you add a default constructor to the sub class, this default constructor still
has to call the non default constructor of the superclass. It is possible to pass
'default' arguments (i.e. null for objects and 0 for primitives), but this is
kinda dodgy, and can result in NPE's if the constructor is expecting a non-null value.
All JVM's also provide a non-portable way to instantiate a class without calling the
constructor (such as com.sun.misc.Unsafe), however as this is not really an official part
of java platform it is not really something a spec should rely on.
So even though it is not impossible to do, it is not very well specified and kinda
fragile, or just plain non-portable.
Also please note that not the CDI specification defines any interceptor behaviour but the
Interceptors-1.1 specification (or any update which gets defined by the EJB-3.2 Expert
Group). So any assumption we made in CDI must be synced with their work.
The interceptors specification does not really have much to say on this. It seems to
assume that the proxiability requirements will be taken care of by the specification that
defines the component type that is being intercepted.
And actually, all beans of passivating scopes must provide a default-ct because of
Serialization reasons anyway, isn't?
A default constructor is not a requirement for serialisation. The JVM can create instances
during serialisation directly, without calling the constructor. (Even though the javadoc
for Serializable talks about need a no-arg constructor, this is only a requirement for a
non-serialization superclass with a serializable sub-class).
----- Original Message -----
> From: Stuart Douglas <stuart.w.douglas(a)gmail.com>
> To: Mark Struberg <struberg(a)yahoo.de>
> Cc: Jozef Hartinger <jharting(a)redhat.com>; cdi-dev
> Sent: Thursday, October 20, 2011 6:54 AM
> Subject: Re: [cdi-dev] Question for clarification and my understanding
> I thought that interceptors had to be done via subclassing as well, as the spec
> does not specify that intercepted beans have to have a default constructor?
> On 20/10/2011, at 3:44 PM, Mark Struberg wrote:
>> The spec says that only Decorators need to be done via subclassing.
>> ----- Original Message -----
>>> From: Jozef Hartinger <jharting(a)redhat.com>
>>> To: Rick Hightower <richardhightower(a)gmail.com>
>>> Cc: cdi-dev <cdi-dev(a)lists.jboss.org>
>>> Sent: Wednesday, October 19, 2011 7:33 PM
>>> Subject: Re: [cdi-dev] Question for clarification and my understanding
>>> Only normal scoped beans require client proxies. Decoration and
>>> interception should be implemented by subclassing (see CDI-74, CDI-44).
>>> On 10/19/2011 07:24 PM, Rick Hightower wrote:
>>>> Section 5.4
>>>> "Client proxies are never required for a bean whose scope is a
>>>> pseudo-scope such as @Dependent."
>>>> I understand the concept of client proxies to allow for scopes and
>>>> Is this a true statement...
>>>> Client proxies may not be needed for @Dependent (pseudo scope). CDI
>>>> may provide a client proxy for @Dependent.
>>>> A proxy is needed for @Dependent objects that are decorated or
>>>> intercepted with Decorators or Interceptors.
>>>> Are all injected objects proxied or only objects that are normal
>>>> scoped or decorated?
>>>> *Rick Hightower*
>>>> (415) 968-9037
>>>> Profile <http://www.google.com/profiles/RichardHightower>
>>>> cdi-dev mailing list
>>> cdi-dev mailing list
>> cdi-dev mailing list