MIDDLE WARE TECHNOLOGIES

B.TECH III YR II SEMESTER

UNIT 5 PPT SLIDESTEXT BOOKS:

1.Client/Server programming with Java and CORBA Robert Orfali and Dan Harkey, John Wiley & Sons,SPD 2nd Edition2. Java programming with CORBA 3rd Edition, G.Brose, A Vogel and K.Duddy, Wiley-dreamtech, India John wiley and sons

INDEX UNIT 5 PPT SLIDES

S.NO. TOPIC LECTURE NO. PPTSLIDES

1. Two types of Client/Server invocations L32 L1.1 TO L1.5 L33 L2.1 TOL

2.52.The static CORBA L34 L3. 1 TO L2.5 3. CORBA program L35 L4. 1 TO L3.54. ORB lets with Applets . L36 L5. 1 TO L4.55. Dynamic CORBA L3 L6. 1 TO L5.56. The portable count L38 L7. 1 TO L6.57. dynamic count L39 L8. 1 TO L7.58. multi count L40 L9.1 TO L9.4

Lecture 1 slide 1

UNIT5 SYLLABUS

• Core CORBA / Java: Two types of Client/Server invocations-static, dynamic. The static CORBA, first CORBA program, ORB lets with Applets, Dynamic CORBA—The portable count, the dynamic count multi count.

Lecture 1 slide 1

What is CORBA

• 1.CORBA is a specification for the distributed object bus architecture defined by OMG

• 2.It is a product of a consortium called the OMG

• 3.OMG includes 800 compinies representing the entire spectrum of computer industry.

Lecture 1 slide 2

CORBA services

• Lifecycle services• Persistence service• Naming services• Event services• Concurrency services• Transactional services• Relationship services• Externalization

Lecture 1 slide 3

CORBA services

• Query services

• Licensing service

• Properties services

• Time service

• Security service

• Trader service

• Collection service

Lecture 1 slide 4

Web services

• 1.SOAP(simple object access protocol)

• 2.WSDL(web service description language)

• 3.UDDI(universal description ,discovery integration)

Lecture 1 slide 5

What is SOAP

• SOAP is a communication protocol• SOAP is based on XML• SOAP is a simple and extensible• SOAP will be developed as a W3C standard• SOAP allowed you to get around firewalls• SOAP is a format for sending messages• The basic web services platform is XML plus

HTTP

Lecture 2 slide 1

What is WSDL

• WSDL is written in XML

• WSDL is an XML document

• WSDL is used to describe web services

• WSDL is also used to locate Web services

• WSDL is not yet a W3C standard

Lecture 2 slide 2

Benefits of SOA

• Better reuse

• Well defined interfaces

• Easier to maintain

• Better flexibility

Lecture 2 slide 3

DCOM

• DCOM is an extension to COM

• DCOM uses a protocol called the object remote procedure call (ORPC)

• CORBA uses internet-inter ORB protocol

• DCOM using MIDL

Lecture 2 slide 4

middleware's

• RMI

• RPC

• CORBA

• SOA

• WEB SERVICES

Lecture 2 slide 5

Four main elements of CORBA

• Object request broker

• CORBA services

• CORBA facilities

• Application objects

Lecture 3 slide 1

CORBA facilities

• Are collections of IDL-defined frameworks

That provide services of direct use to application

Categories

-Horizontal

-Vertical

Lecture 3 slide 2

Core CORBA/java

• Advantages (of static Vs dynamic)• It is easier to program – remote method name, parameters.• It provides more robust type checking – complete time

checks.• It performs well – a single API.• It is self documenting

• Dynamic: m.i.is more flexible; allows to add new classes at runtime, useful for tools.

• Steps of CORBA static m.i:• Create your IDL defs.• build the interface defs. to the interface

repository.

Lecture 3 slide 3

Core CORBA/java

• pre compile – generates– client states– server skeleton– language specific example class, (CORBA 3.0

calls it a servant class)

• Add the servant impl.code.• Compile the code. (ref. language compiler)• Register the run-time objects with the Impl.

Repository.

Lecture 3 slide 4

Core CORBA/java• Module counter• {• Interface count• {attribute long sum;• Long increment ( );• };• };• Mapping CORBA IDL to Java• Prompt > idl2java count.idl – no – comments – no-tie –no-tie-specifies not to

generate extra delegation class. Still, it generates a Java package counter, which consist of 5 java classes & 1 Java interface.

• Counter.-Count Impl base – server side skeleton• Counter.-st-count : client side stub• Counter.Count Helper – provides useful helper for count clients.• Counter.Count Holder: public instance member of type• Package Counter;

Lecture 3 slide 5

Core CORBA/java• Counter.Count • Public interface count extends org.orng.CORBA.object.• {• Public int sum ( );• Public void sum (int – vol);• Public int increment ( );• }• Counter.-Example-Count-Example class for count obj.impl.VisiBroken’s

Output:• Package counter;• Public class-example-count extends counter-count ImplBase• {• Public – example – count (java.lang.string name)• {• Super (name;)• }

Lecture 4 slide 1

Core CORBA/java• Public-example-count ( )• {• Super ( );• }• Public int increment ( )• {• //implement operation . . . . . • }• public void sum (int sum)• {• //implement attribute writer . . . • }• Public int sum ( )• {

Lecture 4 slide 2

Core CORBA/java• // implement attribute reader . . . .• }• }• Server side of Count:• // count Impl.Java : The count Implementation Class Count

Impl Base extends Counter-Count Impl Base• {• Private int sum;• Count Impl (string name)• {• Super (name);• S.O.P. (“count object created”);• Sum = 0;• }

Lecture 4 slide 3

Core CORBA/java• Public int sum ( )• {• Return sum;• }• Public void sum (int val)• {• Sum = val;• }• Public int increment ( )• {• Sum ++• Return sum• }• }

Lecture 4 sllide 4

Core CORBA/java• Main server program:• Class count server• {• Static public void main (string [ ] ays)• { try• { org.umg.CORBA.ORB orb = org.umg.CORBA.ORB. init (ays,null);• org.umg.CORBA.BOA boa = cob.BOA – init ( );• count Impl count = new count Impl (“my count”);• roa.obj-is-ready (count);• boa.impl-is-ready ( );• {• Catch (org.umg.CORBA.Systm Exception e)• {• System.error.print ln(e);• }• }• }

Lecture 4 slide 5

Core CORBA/java• Client side of Count:• Class Count Client• {• Public static void main (string [ ] ays)• {• Try• {• S.O.P (“initializing the ORB”);• org.umg.CORBA.ORB orb = org.umg.CORBA.ORB init (ays, null);• S.o.p (“building to count object”);• Counter.count counter = counter.count helper.build (orb,”my count”);• S.o.p. (“setting sum to o”);• Counter.sum ((int)o);• //calc.st.time.• Long start Time = sytem.current Time millis ( );• //Increment 1000 times• s.o.p (“incremtning”);

Lecture 5 slide 1

Core CORBA/java• for (int i=0, i<1000; i++)• {• Counter.increment ( );• }• //calc.strp.time; print statistics• Long step Time = system.current Time millis ( );• s.o.p. (“Avg ping = “+((stop Time-start Time)/1000t)+msecs”);• s.o.p (“sum=”+counter.sum ());• }• Catch (org.umg.CORBA.system Exception e)• {• System.err.printh (“system Exception”);• System.err.printh(e);• }• }

Lecture 5 slide 2

Core CORBA/java

• }• O/p• 1. Local static Remote static (10mbit/s

Ethernet)• 3.9 msecs 3.6 msecs• 2. Symantic visual caf JIT sum JDK• Local 3.9 msec 6.7 msec• Remote 3.6 msec 5.6 msec•

Lecture 5 slide 3

Core CORBA/java

• Orblets with Applets • Applets let you create component – sized apps

that serves can ship to clients via ordinary HTML pages.

• Applets become an instant front-end to the remote services, you provide; so applets are “just-in-time” shippable clients.

• Applet life cycle: init, start, paint, action, handler Event, stop, destroy

• The HTML Applet Tag: CODE, WIDTH, HEIGHT, CODEBASE,ALGIN,PARAM

Lecture 5 slide 4

Core CORBA/java

• CORBA-enabled Applet:– To create applet version of the COUNT client,

enabled it inside an HTML page, download using web browser, invoke methods on the count server.

– The count IDL – Use count server, as is – so IDL remains unchanged. Our applet can use both the

• Counter.-st-count and Counter.counter Helper,as – Server capture of the Java Count Applet

• Count client Applet

Lecture 5 slide 5

Core CORBA/java• The client applet code:• //count client Applet.java Applet client, visiBroker for Java.• Import Java.awt.*;• Public class Count client Applet extends java.applet.Applet.• {• Private Text Fields, count field, ping Time Field;• Private button run Count;• Private Counter.Count.counter;• Public.void init ( );• {• //create a 2 by 2 grid of widgets• Set Layout (new Grid Layout (2,2,10,10));• //Add the from widgets, initialize where • add (new Label (“count”));• add (count Field = new Text Field ( ));

Lecture 6 slide 1

Core CORBA/java• count field.set Text (“1000”);• add (run count = new Button (“run”));• add (ping time field = new Text Field ( ));• ping Time field.set Editable (false);• try• {• //Init.the ORB.• Show Status (“Initializing the ORB”);• Org.omg.CORBA.ORB orb = org.umg.CORBA.ORB.init (this,null);• //Build to the count object• Show Status (“Binding to count object”);• Counter = Counter.CountHelper.build(orb,”mycount”);• }• Catch (org.umg.CORBA.System.Exception)• {• Show status (“applet Exception “+e);}

Lecture 6 slide 2

Core CORBA/java• }• Public broken action (Event ev, object avg)• {• If (ev.target = = run count)• {• Try• {• // set sum to initial value of 0• Show status (setting sum to 0”);• Counter.sum((int)o);• //get data from ad set value of applet fields.• Show status (“Incrementing”);• Int stop count = Integer.parse Int (count field.get Text( ));• Ping Time Field .set Text (“ “);• //calculate start time.• Long start Time = system.current Time millis( );

Lecture 6 slide 3

Core CORBA/java• //increment stop count time• For (int i = 0; i< stop Count; i ++)• Counter.increment ( );• //calculate stop time; show statistics• Long stop time = System.current Time millis( );• Ping Time Field.set Text (“avg ping = “+float.to String (float) (stop time-start time)/stop

-count)+”msecs);• Show status (“sum=”+counter.CORBA sum() );• }• catch (org.umg.CORBA.System Exception e)• {• show status (“system exception “+e);• }• return time;• }• return false;• }• }

Lecture 6 slide 4

Core CORBA/java

• Completion • Prompt . Java c– d\. . . . count client applet.Java• Create a web page• Count .html• <h1> count client Applet </h1>• <hr>• <center>• <applet code = count client applet.class width =

300 height = 60 CODE BASE = classes>

Lecture 6 slide 5

Core CORBA/java• <paramname = org.umg.CORBA.ORB Class• Value = com.visigenic.vbroken.orb.DRB>• </applet• </count>• <hr>• Results:• Local Vs Remote : Java applet/CORBA count server.• Local static count Remote static count• JIT compiled 17.6msecs 16.1 msecs• Interpreted 30.2 msecs 23.3 msecs• Applets Vs Apps• Java applet Java app• JIT compiled 16.1 msec 3.6 msec• Interpreter 23.3 msec 5.6 msec

Lecture 7 slide 1

Dynamic CORBA

• The Portable Count • Make count portable by replacing the visigenic –

specific bind with the CORBA naing semic.• Rylau BOA-specific code in count with PoA semantics.• CORBA Naming Semic:• Generic structures to compose compound names – so

it can work with global naming conventions such as URLs, domain names, DCE, JNDI, LDAP, NDS, Unix files, NTfiles etc.

• CORBA N.S.in the Tel.white.pages for objects, it lets you find objects by name.

• Name binding – name to obj.ref.• Name context – newspace

Lecture 7 slide 2

Dynamic CORBA

• ex:• Each named component is a structure with two

attributes –– identifier – object name string– kind – string to put a descriptive attribute – ex.file

type.• IDL Def. try a CORBA name:• //IDL• Type of sequence ,Name component>name;• Struct name component• {Istring id; Istring kind;};

Lecture 7 slide 3

Dynamic CORBA• The object naming service interfaces:• Naming context – resolve, list, destroy, new-context, unbind, bind, rebind,

bind-context, rebind-context, bind-new-context.• Binding Instructor: next-one, next-n, destroy• C/S Naming Scenarious:• A Server invokes link to associate a logical name with an obj.ref.• The N.S.adds this obj.ref from binding to its namespace database.• client app. Invokes resolve to obtain an obj.ref. to this name.• The client uses the obj.ref. to invoke methods on the target object.• Scenarios 1: Creating the NS.• resolve – initial – references (ORB)• bind-new-context (Root context) – Results context• bind-new-context (Results context) – client made context• bind (client med context) – cascum.• bind (client med context) – PlayeBonce

Lecture 7 slide 4

Dynamic CORBA• org.umg.CORBA.object obj ref = orb.resolve – initial – refernces

(“name service”);• org.umg.Cosnaming,naming context root context =

org.umg.cosnaming.naming context helper.maxrow (obj ref);• Scenario 2: Finding objects:• resolve-initial –reference (ORB)• create the name• resolve (Root context)• root.value – obj ref• Invoke methods• Portable count:• Count portable client class• The current IDL• The current portable Impl class• The current portable server class

Lecture 7 slide 5

Dynamic CORBA• The Dynamic Count • In static m.i., a pre compiled stub is required for each interface the client

used.• It is true even in the case of applets, through the stub’s byte codes are

downloaded at run-time.• Dynamic Invocation Interface (DII) is a stub-less binding approach.• The client can invoke any operation on any object without repairing

precompiled stubs i.e., the client discovers interfaces – related infn. at invocation time, it requires no compile – time knowledge.

• To discover remote objects, the mechanisms available are– ‘string field’ object reference is provided to the client; which is converted into a

live object reference an the connection is made.– Clients can look up objects by using the CORBA naming service.– Clients can discover objects by using the CORBA’s yellow pages – The Trader

service.

Lecture 8 slide 1

Dynamic CORBA

• The CORBA dyn. invocation process:• Obtain the Interface name• get – interface ( )• returns a ref. to interface ref. object• Obtain method Description• Look up – name ( )• Describe ( )• To obtain the method’s full IDL def.• Create Argument list:• Create – list ( )• Add-item ( ) . . . add item ( ). . add-item ( )• Create the request

Lecture 8 slide 2

Dynamic CORBA

• Create-request (object reference, method, arguments list)

• Invoke the Remote method• Using RPC Invoke ( )• send/receive send-deformed ( )• deferred get-response ( )• Data of ram one way send-one way ( )• Dyn. Invocation Interfaces – four Interfaces:• CORBA : : object – pseudo object interface that

defines opens that every CORBA object must support.

Lecture 8 slide 3

Dynamic CORBA• Methods: get-intefaces; create-request; - request.• CORBA::Report ;- pseudo object interface that defines the operation on a

remote object.• Method ; add-ary, invoke, send-oneway, send-defered, get response,

pill.response, delete, add-item, add-value, get-count, remove, free, free-memory.

• CORBA::ORB: Gen. purpose ORB methods – create-list, create - operation- list, send – multiple-request-one-way, send-multiple-requests-defered, pill-next-response, get -next-response

• CORBA ::NVList: To help constant parameters – NV List object – maintains a list of self describing data items called Namedvalues.

• IDL- Street-Namedvalue• {• Identifier name; // my name any argument;//argument long len;//length/count

of my value flys-modes//in,int, or inout• Dynamic Invocation Scenarios:• So it Yourself :

Lecture 8 slide 4

Dynamic CORBA

• Client Object Interfaces def.Operationdef. ORB

– get.interface ( )– look up name– describe– create – list– add – item– create – request– Invoke– delete– free– a variation of first method

Lecture 8 slide 5

Dynamic CORBA

• The ORB-Can-Help scenario:• Client Object Interfaces def.

Operationdef. ORB• In place of steps 3,4, and 5 above issue• 1 & 2 same as above • 3. create – operation list• 4. add-value• 5. Create-request• 6. invoke• 7. delete• 8. free• Dyn. Invocation – the yet – another-way scenario:

Lecture 9 slide 1

Dynamic CORBA– in stead of adding your arguments to an NVList, you add them to the

request object.• The Dynamic Count:

• Count server class, as is; so the IDL remains unchanged.• No stubs for a dynamic client, however a mixed client is created that does

both static and dynamic invocations. Count cliendDii.Java• Test Results:• Local Dyn. Count ping Remote Dyn.Count ping• Invokenly 3.9msec

3.6msec• Prepared invoke 61.4 msec

57.8 msec• Note: Choices of method invocation:

– Static precompiled stubs– Dynamic invocations using DII.– Downloadabale stubs – Java – download both client & stubs, (applet).

Lecture 9 slide 2

Dynamic CORBA

• When to use what • Usage Pattern

Recommendation• 1. Client – Server frequent; use static precompiled

stubs• Server obj.doesn’t chage• 2. Client – server ingrequent use DII• 3. client – server object runtime use DII• 4. Client runs with in browser; use downloadable

applet and static • if discovers new object stubs. Applet becomes

the client for this object.

Lecture 9 slide 3

Dynamic CORBA

Multi – Count • Multi client – multiple clients, call backs,;

reversely C&S roles.• VisiBroken for Java CORBA ORB is both a

C&S• Multi Threaded client – client using Java’s

threads• Coordinator – a new server – uses callbacks to

remotetly control clients.• Applet as a front-end to the coordinator –

called multi console.

Lecture 9 slide 4

Dynamic CORBA

• The Multi count CORBA interfaces:– Client control interface – client call back

• Methods – start, stop– Coordinator interface - server

• Methods – start, stop, register– count interface - server

• method – increment

• A Multi count callback Scenario