At 02:01 PM 2/23/2001 -0500, you wrote:
>No server that has sucessfully passed CTS 1.2 -- official certification
>based on that suite of 6,000+ tests, not certification based on subjective
>interpretation of adherence to the specs -- can make use of passing objects
>by reference. This optimization is strictly disallowed, not a permissable
>value-add. That's not to say it isn't valuable, and non-compliant servers do
>have an advantage there. It's just to say that if you're using a certified
>app server, don't expect this local optimization.
>
>A future version of the spec will address this.
>
>
>psn
>
>
>-----Original Message-----
>From: A mailing list for Enterprise JavaBeans development
>[mailto:[EMAIL PROTECTED]]On Behalf Of Dan Christopherson
>Sent: Friday, February 23, 2001 1:10 PM
>To: [EMAIL PROTECTED]
>Subject: Re: If the EJBs are on the local machine will it avoid making
>rem ote calls?
>
>
>On Fri, 23 Feb 2001, Thibault Cuvillier wrote:
>
>> Dan,
>>
>> >Specifically, the EJB Container is not allowed to pass
>> >non-remote objects
>> >by reference on inter-EJB invocations when the calling and called
>> >enterprise beans are collocated in the same JVM. Doing so
>> >could result in
>> >the multiple beans sharing the state of a Java object, which
>> >would break
>> >the enterprise beans semantics.
>>
>> Thank for the spec outline Dan.
>>
>> But, most of the AS do not duplicate the objects passed by reference by
>> the middleware during a local call, which break the EJB semantic.
>Then they're not spec-compliant.
>
>>
>> That's mean that when you develop an EJB, you must be aware about
>> problem, and keep in mind that pass-by-value objects may be in fact passed
>> by references in the case of a local call.
>I'd say "should be aware" - most AS will allow you to turn on this
>optimization, some may default to having it on, but if you can't coax the
>container to do pass by value, it isn't an EJB 1.1 (or 2.0,
>when there is such a thing) container.
>
>>
>> So the following code is dangerous:
>> public void doSomeStuff(List list) {
>> list.add("hello");
>> // do some stuff with "list"
>> }
>> This code should be fixed as:
>> public void doSomeStuff(List list) {
>> List local = new ArrayList();
>> Collections.copy(list, local);
>> local.add("hello");
>> // do some stuff with "local" }
>>
>> This example applied as well to by-values returned objects:
>> private List accounts;
>>
>> public List getAccounts() {
>> return accounts;
>> }
>> This client may change the account list if the case of a local
>call
>> (passed by reference), which break the encapsulation.
>>
>> This method should be fixed as:
>> private List accounts;
>>
>> public List getAccounts() {
>> List copy = new ArrayList();
>> Collections.copy(accounts, copy);
>> return copy;
>> }
>> Or (better solution)
>> private List accounts;
>>
>> public List getAccounts() {
>> return Collection.unmodifiableList(accounts);
>> }
>>
>> Tibo.
>>
>>
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>>
>
>--
>Dan Christopherson (danch)
>nVisia Technical Architect (www.nvisia.com)
>
>Opinions expressed are mine and do not neccessarily reflect any
>position or opinion of nVISIA.
>
>---------------------------------------------------------------------------
>If you're a capitalist and you have the best goods and they're
>free, you don't have to proselytize, you just have to wait.
>-Eben Moglen
>
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