This example uses a very simple stack server. The specification
contains two interfaces: the first is the Stack itself and the
other is the StackFactory which is used to create new stacks.
The specification is in the file stack.idl
.
#ifndef _STACK_IDL #define _STACK_IDL module StackModule { exception EmptyStack {}; interface Stack { long pop() raises(StackModule::EmptyStack); void push(in long value); void empty(); }; interface StackFactory { StackModule::Stack create_stack(); void destroy_stack(in StackModule::Stack s); }; }; #endif
Run the IDL compiler on this file by calling the ic:gen/1
function
1> ic:gen("stack").
This will produce the client stub and server skeleton. Among other files a stack API module named StackModule_Stack.erl
will be produced.
This will produce among other files a stack API module called
StackModule_Stack.erl
which contains the client stub and
the server skeleton.
After generating the API stubs and the server skeletons it is time to
implement the servers and if no special options are sent
to the IDL compiler the file name should be
<global interface name>_impl.erl
, in our case
StackModule_Stack_impl.erl
.
%% StackModule_Stack_impl example file. -module('StackModule_Stack_impl'). -include_lib("orber/include/corba.hrl"). -include("StackModule.hrl"). -export([pop/1, push/2, empty/1, init/1, terminate/2]). init(_Env) -> {ok, []}. terminate(_From, _Reason) -> ok. push(Stack, Val) -> {reply, ok, [Val | Stack]}. pop([Val | Stack]) -> {reply, Val, Stack}; pop([]) -> corba:raise(#'StackModule_EmptyStack'{}). empty(_) -> {reply, ok, []}.
We also have the factory interface which is used to create new stacks
and that implementation is in the file
StackModule_StackFactory_impl.erl
.
%% StackModule_StackFactory_impl example file. -module('StackModule_StackFactory_impl'). -include_lib("orber/include/corba.hrl"). -export([create_stack/1, destroy_stack/2, init/1, terminate/2]). init(_Env) -> {ok, []}. terminate(_From, _Reason) -> ok. create_stack(State) -> %% Just a create we don't want a link. {reply, 'StackModule_Stack':oe_create(), State}. destroy_stack(State, Stack) -> {reply, corba:dispose(Stack), State}.
To start the factory server one executes the function
StackModule_StackFactory:oe_create/0
which in this
example is done in the module stack_factory.erl
where
the started service is also registered in the name service.
%% stack_factory example file. -module('stack_factory'). -include_lib("orber/include/corba.hrl"). -include_lib("orber/COSS/CosNaming/CosNaming.hrl"). -include_lib("orber/COSS/CosNaming/lname.hrl"). -export([start/0]). start() -> SFok = 'StackModule_StackFactory':oe_create(), NS = corba:resolve_initial_references("NameService"), NC = lname_component:set_id(lname_component:create(), "StackFactory"), N = lname:insert_component(lname:create(), 1, NC), 'CosNaming_NamingContext':bind(NS, N, SFok).
At last we will write a client to access our service.
%% stack_client example file. -module('stack_client'). -export([run/0]). run() -> case catch corba:string_to_object("corbaname:rir:/NameService#StackFactory") of {'EXCEPTION', _E} -> io:format("The stack factory server is not registered~n",[]); SF -> %% Create the stack SS = 'StackModule_StackFactory':create_stack(SF), 'StackModule_Stack':push(SS, 4), 'StackModule_Stack':push(SS, 7), 'StackModule_Stack':push(SS, 1), 'StackModule_Stack':push(SS, 1), Res = 'StackModule_Stack':pop(SS), io:format("~w~n", [Res]), Res1 = 'StackModule_Stack':pop(SS), io:format("~w~n", [Res1]), Res2 = 'StackModule_Stack':pop(SS), io:format("~w~n", [Res2]), Res3 = 'StackModule_Stack':pop(SS), io:format("~w~n", [Res3]), %% Remove the stack 'StackModule_StackFactory':destroy_stack(SF, SS) end.
To write a Java client for Orber you must have another
ORB that uses IIOP for client-server communication and supports a
Java language mapping. It must also have support for
IDL:CosNaming/NamingContext
or IDL:CosNaming/NamingContextExt
.
If the client ORB support Interoperable Naming Service the Java Client
can look like:
/* * Stack example. */ package StackModule; import org.omg.CORBA.*; import org.omg.CORBA.SystemException; import org.omg.CORBA.ORB.*; public class StackClient { public static void main(String args[]) { org.omg.CORBA.Object objRef; StackFactory sfRef = null; Stack sRef = null; // The argument can look like // "corbaname::host:4001/#StackFactory" String corbaName = new String(args[0]); try{ ORB orb = ORB.init(args, null); objRef = orb.string_to_object(corbaName); sfRef = StackFactoryHelper.narrow(objRef); sRef = sfRef.create_stack(); sRef.push(4); sRef.push(7); sRef.push(1); sRef.push(1); try{ System.out.println(sRef.pop()); System.out.println(sRef.pop()); System.out.println(sRef.pop()); System.out.println(sRef.pop()); // The following operation shall // return an EmptyStack exception System.out.println(sRef.pop()); } catch(EmptyStack es) { System.out.println("Empty stack"); }; sfRef.destroy_stack(sRef); } catch(SystemException se) { System.out.println("Unexpected exception: " + se.toString()); return; } } }
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If an ORB does not support CosNaming at all the |
To build the example for access from a Java client you need a Java enabled ORB (e.g. JavaIDL). The example below is based on JDK-1.4.
fingolfin 127> erl Erlang (BEAM) emulator version 5.5.4.3 [async-threads:0] [hipe] [kernel-poll:false] Eshell V5.5.4.3 (abort with ^G) 1> ic:gen(stack). Erlang IDL compiler version 4.2.12 ok 2> make:all(). Recompile: StackModule_EmptyStack Recompile: StackModule_Stack Recompile: StackModule_StackFactory Recompile: StackModule_StackFactory_impl Recompile: StackModule_Stack_impl Recompile: oe_stack Recompile: stack_client Recompile: stack_factory up_to_date 3> BREAK: (a)bort (c)ontinue (p)roc info (i)nfo (l)oaded (v)ersion (k)ill (D)b-tables (d)istribution a fingolfin 128> idlj stack.idl fingolfin 129> javac StackModule/*.java fingolfin 130> javac *.java fingolfin 131> cp StackClient.class StackModule/
Below is a short transcript on how to run Orber.
fingolfin 143> erl Erlang (BEAM) emulator version 5.5.4.3 [async-threads:0] [hipe] [kernel-poll:false] Eshell V5.5.4.3 (abort with ^G) 1> orber:jump_start([{interceptors, {native, [orber_iiop_tracer_silent]}}]). ok 2> oe_stack:oe_register(). ok 3> stack_factory:start(). ok 4> stack_client:run(). 1 1 7 4 ok 5>
Before testing the Java part of this example generate and compile Java classes for
orber/examples/stack.idl
as seen in the build example.
To run the Java client use the following command:
fingolfin 38> java StackModule.StackClient "corbaname::localhost:4001#StackFactory" 1 1 7 4 Empty stack fingolfin 39>
When starting Erlang the configuration parameter lightweight
must be used.
The value is set to a list of remote modifiers, equal to the
orber:resolve_initial_references_remote/2
argument, i.e., "iiop://host:port".
On these given nodes, all necessary oe_X:oe_register()
calls must be done
before running a Orber lightweight.
Lightweight Orber do not allow us to:
With lightweight Orber we do not:
orber:install/1
To be able to start objects we must supply a factory on a non-lightweight node(s) which can start necessary objects. One way to accomplish this is:
smaug 125> erl -orber domain "ORBER_MAIN" Erlang (BEAM) emulator version 4.9 Eshell V4.9 (abort with ^G) 1> mnesia:create_schema([]). 2> orber:install([]). 3> orber:start(). 4> oe_MyFactory:oe_register(). 5> oe_MyObjects:oe_register(). %% Do this for all objects necessary. 6> Factory=MyFactory_Creater:oe_create(). 7> NS=orber:resolve_initial_references("NameService"). 8> NC=lname_component:set_id(lname_component:create(), "myFactory"). 9> N =lname:insert_component(lname:create(), 1, NC). 10> 'CosNaming_NamingContext':bind(NS, N, Factory)).
Now we have a factory we can access from, hence, we can now start a lightweight Orber:
fingolfin 14> erl -orber lightweight [\"iiop://host1:port\", \"iiop://host2:port\"] -orber domain \"ORBER_LIGHT\" Erlang (BEAM) emulator version 4.9 Eshell V4.9 (abort with ^G) 1> orber:start_lightweight(). 2> Fac=corba:string_to_object("corbaname::Host:Port/NameService#myFactory"), 3> Obj=MyFactory_Creater:MyObject(Fac, Args). 4> MyObject:myFunction(Obj,Args2).
It is not necessary to start both Orber types using the configuration
parameter domain
, but at least one of them.