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Diffstat (limited to 'TAO/docs/poa_migration.html')
| -rw-r--r-- | TAO/docs/poa_migration.html | 139 |
1 files changed, 9 insertions, 130 deletions
diff --git a/TAO/docs/poa_migration.html b/TAO/docs/poa_migration.html index 9c925e511f2..69056ba4a1b 100644 --- a/TAO/docs/poa_migration.html +++ b/TAO/docs/poa_migration.html @@ -24,14 +24,7 @@ Interconnection</A> columns written by <A HREF="http://www.cs.wustl.edu/~schmidt/">Doug Schmidt</A> and <A HREF="http://www.iona.com/hyplan/vinoski/">Steve Vinoski</a>. -<h3>Contents</h3> -<ul> - <li><a href="#Client-side Changes">Client-side Changes</a> - <li><a href="#Server-side Changes">Server-side Changes</a> - <li><a href="#Reference counting Servants">Reference counting Servants</a> -</ul> - -<H4><a name="Client-side Changes">Client-side Changes</a></h4> +<H4>Client-side Changes</h4> <ul> <li>Very little has changed. Thus, many applications require to changes.</li><P> @@ -39,7 +32,7 @@ HREF="http://www.iona.com/hyplan/vinoski/">Steve Vinoski</a>. and client, which is necessary in TAO to support collocation.</li> <P> </ul> -<h4><a name="Server-side Changes">Server-side Changes</a></h4> +<h4>Server-side Changes</h4> <UL> <li><CODE>POA_init</CODE> is replaced with <CODE>resolve_initial_references("RootPOA")</CODE> followed @@ -69,15 +62,15 @@ between different runs of the server; it makes no claims that state or anything else is persistent.</li><P> <ul> - <li> Servants are not automatically activated, hence you must register - them by calling some of the <CODE>activate_object*</CODE> methods on a POA or - calling <CODE>_this</CODE> on the servant; with the latest you have no control on - the ObjectId (which sometimes is good), and the POA must support the + <li> Servants are not automatically activated, hence you must register + them by calling some of the <CODE>activate_object*</CODE> methods on a POA or + calling <CODE>_this</CODE> on the servant; with the latest you have no control on + the ObjectId (which sometimes is good), and the POA must support the right policies (the RootPOA does).</li><P> - + <li>Servant constructors use to take a <CODE>const char*</CODE> parameter to set - they object id, this is not needed now, in fact in many cases they use + they object id, this is not needed now, in fact in many cases they use to pass this argument to the skeleton class: this will fail now.</li><P> </ul> This list is not intended to be exhaustive, but should give you a good starting point. If you find things along the @@ -85,120 +78,6 @@ way that change your applications and I didn't note them, please send them to me. Perhaps we can work together on the ultimate migration document. <P> </UL> -<h4><a name="Reference counting Servants">Reference counting Servants</h4> - -The new POA/servant <a -href="ftp://ftp.omg.org/pub/docs/orbos/98-07-12.pdf">reference -counting rules</a> of the CORBA 2.3 spec are somewhat tricky. Here are -two main reasons why: <p> - -<ul> - -<li> If a servant is deleted without deactivating from the POA, the -application will crash because the POA will try to access the still -registered (but now non-existent) servant when the POA is destroyed. <p> - -The solution to this is to make sure that the servant is deleted after -the POA is deleted or make sure that the servant is deactivated from -the POA before the servant is deleted. </li> <p> - -<li> You cannot delete a servant which is the target of the current -upcall/request. A good example of this is the typical destroy() -method, usually written like this: - -<PRE> - -class TAO_Export TAO_Thread_Policy : public POA_PortableServer::ThreadPolicy -{ - void destroy (CORBA_Environment &ACE_TRY_ENV); -}; - -void -TAO_Thread_Policy::destroy (CORBA::Environment &ACE_TRY_ENV) -{ - PortableServer::POA_var poa = this->_default_POA (ACE_TRY_ENV); - ACE_CHECK; - - PortableServer::ObjectId_var id = poa->servant_to_id (this, - ACE_TRY_ENV); - ACE_CHECK; - - poa->deactivate_object (id.in (), - ACE_TRY_ENV); - ACE_CHECK; - - // Commit suicide: must have been dynamically allocated. - delete this; -} - -</PRE> - -The correct implementation is: - -<PRE> - -class TAO_Export TAO_Thread_Policy : public virtual PortableServer::RefCountServantBase, - public virtual POA_PortableServer::ThreadPolicy -{ - void destroy (CORBA_Environment &ACE_TRY_ENV); -}; - -void -TAO_Thread_Policy::destroy (CORBA::Environment &ACE_TRY_ENV) -{ - // - // Remove self from POA. Because of reference counting, the POA - // will automatically delete the servant when all pending requests - // on this servant are complete. - // - - PortableServer::POA_var poa = this->_default_POA (ACE_TRY_ENV); - ACE_CHECK; - - PortableServer::ObjectId_var id = poa->servant_to_id (this, - ACE_TRY_ENV); - ACE_CHECK; - - poa->deactivate_object (id.in (), - ACE_TRY_ENV); - ACE_CHECK; -} - -</PRE> - -One additional step required is to make the POA responsible for the -servant after it has been registered with the POA: - -<PRE> - - // Register with the POA. - PortableServer::ThreadPolicy_var result = new_thread_policy->_this (ACE_TRY_ENV); - - // Give ownership of this servant to the POA. - new_thread_policy->_remove_ref (ACE_TRY_ENV); - -</PRE> - -If you use the above approach of multiple inheritance, you must add -the following to your header file: - -<PRE> - -// This is to remove "inherits via dominance" warnings from MSVC. -// MSVC is being a little too paranoid. -#if defined (_MSC_VER) -# pragma warning (disable : 4250) -#endif /* _MSC_VER */ - -</PRE> - -To see the above example in detail, checkout <A -HREF="../examples/POA/Reference_Counted_Servant">TAO/examples/POA/Reference_Counted_Servant</A> -and/or <A HREF="../tao/POA.cpp">POA.cpp</A> and <A -HREF="../tao/POA.h">POA.h</A>. </li> <p> - -</ul> - <hr><P> Back to the <A @@ -206,5 +85,5 @@ HREF="http://www.cs.wustl.edu/~schmidt/ACE_wrappers/TAO/docs/index.html">TAO documentation</A> page. <!--#include virtual="/~schmidt/cgi-sig.html" --> -</BODY> +</BODY> </html> |