Migrating from BOA to POA

• Client side
  • Very little has changed, and some have not needed any changes.
  • You'll have to insure that the Makefile includes .o's for both the server and client; this is necessary to support collocation.

• Server side
  • POA_init() is replaced with resolve_initial_references("RootPOA") followed by a _narrow operation.
  • The implementation no longer inherits from the client-side stub; they inherit from PortableServer::ServantBase. The implications of this are (a) if you want a object reference for that, you must use the _this() method.
  • Object ID's are assigned by the POA unless you activate the servant with a specific ID; IDL_Cubit has examples on how to do this.
  • Unlike the BOA, the POA explicitly addresses the temporal nature of servants and declares that a POA can service either transient or persistent servants (not both). The root POA's (mandated, unchangeable) policy is "transient". The implications of this are that in order for a client to be able to manufacture an object reference on its own and use that to access an object, the servant for that object must be registered with a POA whose policy is "persistent". Thus, you must create a child POA with that policy and register the servant with that POA. NOTE: when the POA declares something as "persistent", it is only stating that the key is valid between different runs of the server; it makes no claims that state or anything else is persistent.
  • Servants are not automatically activated, hence you must register them by calling some of the activate_object* methods on a POA or calling _this() 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).
  • Servant constructors use to take a parameter to set 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.

  This list is not intended to be exhaustive, but should give you a good starting point. If you find things along the way which have to change and I didn't note them, please send them to me. Perhaps we can work together on the ultimate migration document.

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