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Because DMI connects different languages and middle ware
technologies, and these languages and middle wares has
different language like features a mapping of these features
has to be defined.
A package is file containing executable code and
resources. In common this are executables (.exe on windows)
and shared library (.dll on windows or .so on linux).
A unit is a logical group of classes and resources.
Constants and enums (group of constants)
maps a symbolic name to an integer.
Not directly supported by DMI.
Some languages does not have classes, but only
methods. For DMI clients (like Tcl and Lisp) this is
not unnecessarily a problem, because managing classes can
easily mapped into method calls.
For DMI server implementation it is a little bit more
An DMI Client or Server implementation may not support
free functions. Standard ACDK DMI also does not support
free function. Free function may be mapped to static
All DMI server must support a type of name service for
A DMI Client can derives from a interface provided by DMI Server.
The DMI Client has to implement an
Not all DMI Clients/Server supports Constructor with in the sense
- Constructors stand for allocation and initialization.
- more than one Constructors per class can be defined. The constructors
has different arguments. To support this in the language, overloading
of function with same name but different arguments must be supported.
COM, for example, also does not provides constructors.
A solution for this is to establish factory classes, which acts as constructors.
Because memory management differs to the DMI implementations
the semantic of destructors. The DMI client should call releaseRef()
to the DMI Server object when freeing the proxy object instance.
This can be done in finalizer or equal mechanism.
If no automatic mechanism is provided in the DMI Client implementation
the user code has to call dispose() (which calls releaseRef()) manually.
COM doesn't support static member methods.
Solution on client side is to provide a static Object instance (singleton), which
maps to the static member method.
ACDK Object uses overloading in most classes.
Overloaded methods has the same name, but different arguments
(count and/or type of arguments).
void foo(int i);
void foo(RString str);
void foo(int i, jlong l);
Some ACDK DMI Server implementation doesn't support overloading
(for example CORBA).
A mapping of names can be done following ways:
ACDK provides for each method and alternative name. By default
the first method is only registered by its normal name ("foo"),
for all other methods with the same name a number is added to
its name ("foo1", "foo2" and so on).
- Overloaded DMI Server methods are displayed in a 'named mangled' version
for the DMI Client.
The arguments types are encoded in the method names.
- The DMI Server methods should be called with flexible call interface,
like Anys, VARIANT, ScriptVar. The DMI server itself can map the
parameters to the correct method.
With the Attribute "acdk.tools.mc.MethodAltNameAttribute" the alternative
name of a method can be set at compile time (see Attributes).
Also known as arguments.
Parameter values may be typed or not typed.
Tcl for example only provide the type string. All other
types has to be encoded into a string.
Some method invocation protocols encode the type information into
the parameter passing (like in COM IDispatch) and
other does not deliver type information (like standard IIOP in CORBA).
ACDK DMI Server maps this to multiple methods:
void foo(int i, RString n = "hallo", int j = 0);
DMI Clients has only to support overloading, or
they can calling the method with the alternative name.
void foo(int i);
void foo(int i, RString n);
void foo(int i, RString n, int j);
Parameter can have names and be addressed by name.
Before the first named argument the argument are passed
RObject foo(int count, IN(RString) user, IN(RString) pass);
DMI Client VB:
' 42 is positional argument
' pass and user are named arguments
set x = obj.foo(42, pass:="bla", user:="ich")
For ACDK Object named argument are supported by default.
Standard parameter passing is to transfer a value
from caller to caller.
Basic Types are passed by value.
Object types are passed by reference.
Most DMI clients and server only supports the standard
IN parameter passing
For DMI the default parameter passing and parameters
which are marked as IN parameters are equally.
In the ACDK DMI Server implementation IN parameters
are for performance reasons a little bit different implemented:
IN parameters are passed by reference (also Object references)
but cannot modified by the callee.
void foo(IN(RString) str, IN(int) val);
void foo(const RString& str, const int& val);
Some DMI Client and server (ACDK, COM, CORBA)
supports also to transfer a value from callee to
the caller - in the sense of additionally return
Please refer also to: Method Types
Object types normally transfered by reference. This
means by the default parameter passing the DMI server
gets only a DMI Object proxy handle from the DMI server.
With the BYVAL attributes the Object type will be serialized.
Please refer also to: Method Types
ACDK support to declare a list of exceptions which may
be thrown by a method. The exceptions must be derived
from acdk::lang::Throwable and always reference
to exceptions will be handled.
If a method declares exceptions, the exceptions can
be handled with the correct types in remote and script calls.
If an thrown exception is not declared in the method signature
the exceptions thrown by the server will be thrown (after de-marshaled)
In CORBA methods can has the attribute oneway. These
methods may return immediately and executed in another thread.
oneway methods must not has return value other that void
and no IN or OUT parameters.