RMI-IIOP CORBA Sample---------------------Brief Description :This sample demonstrates on how to use CORBA within Java Web Start. It shows how a simple Java  program using CORBA can be packaged, downloaded and executed as a JNLP application by Java Web Start. RMI-IIOP utilizes the Java CORBA Object Request Broker (ORB) and IIOP, so you can write all of your code in Java, and use the rmic compiler to generate the code necessary for connecting your applications via the Internet InterORB Protocol (IIOP) to others written in any CORBA-compliant language. Please note that this sample does n't use any of the JNLP APIs. It uses RMI Compiler (rmic) with -iiop option to generate IIOP stubs and tie classes. This sample consists of a remote interface (HelloInterface), a remote object implementation (HelloImpl), an RMI server that creates an instance of remote object implementation (HelloServer) and a client application (HelloClient) that invokes the remote method - sayHello().  A remote object is an instance of a class that implements a Remote interface.Your remote interface will declare each of the methods that you would like to call from other machines. Implementation of the remote method - sayHello()in this example just returns the string "Hello from Java Web Start" to thecaller. HelloServer is the class which has a main method that creates an instance of the remote object implementation, and binds that instance to aname ("HelloService") in the Naming Service using JNDI API. Once a remote object is registered on the server, callers (HelloClient) can look up the object by name (using a naming service that is part of the ORB Daemon), obtain a remote object reference, and then remotely invoke methods on the object. ORBD and HelloServer should be started successfully before launching the client. Java Web Start will execute the HelloWorld Client application as specified in the .jnlp file. Client and Server will be passed the host and port number information of the orbd at the runtime. For the client, host and the port number information are specified in the .jnlp file.Java Web Start is launched automatically by browser when the user clicks ona link which is associated with a JNLP file.It then downloads and caches theclient application on the local client machine where browser is running.This cached application when invoked next time is already downloaded andruns as fast as a traditionally installed application.By default applicationsare run in a protective environment (sandbox) with restricted access tolocal disk and network resources. Java Web Start only transfers JAR filesfrom the Web server to the location determined by it on the client machine. To provide a simple and convenient packaging format of Applications, JavaWeb Start includes a servlet in the developer's pack. The name of the servletis JnlpDownloadServlet and is packaged into the jnlp-servlet.jar file. Thisservlet eases deployment of application on any J2EE-complaint applicationserver by packing a JNLP files and its associated resources in a Web Archive(.war) file. For more details on Java Web Start product and JNLP API, Please check outonline docs athttp://java.sun.com/products/javawebstart/developers.htmlFor the latest documentation on RMI-IIOP, Please refer tohttp://java.sun.com/j2se/1.4/docs/guide/rmi-iiop/index.htmlFiles :src       - This directory has all the required source files :            core directory has the code required for HelloClient            and HelloServer java programs. stubs consists of remote            interface, remote object implementation and the stuff            generated by rmic compiler.lib       - This directory contains the jar files generated after the build process.class     - This directory contains all the  .class files generated            by the build process. war       - This directory contains all the files required            for deploying a web based application. Application            related .jnlp files and .jar files are inside app.             helloworld.jnlp and HelloWorld.jar are the main             application resources. myKeystore is a keystore used             mainly for the purpose of signing jar files.Building & Deployment of Application :1) Build .class and .jar files by running     gnumake   in the directory where GNUmakefile file resides.   The following environment variable must be set:   # environment variable SDK_HOME should point to SDK directory   # environment variable FILE_SEPARATOR variable for file separator (; on win32 and : on unix)   If you are running on windows platform, it also assume you have MKS Toolkit installed and it is in your path environment variable.  (We need commands like cp, echo, mkdir, rm)     The generated classes will go to the classes directory, and the resulting jar files will be in the lib directory by default.  You can adjust the output directory to anything you want by changing the GNUmakefile.2) Applications by default run in a restricted environment where they    have limited access to local computing resources, such as storage    devices and the local network. Please note that you don't need to   sign the jar file for this sample.However it may fail with a security   error (access denied java.io.FilePermission orb.properties read )   when the client application is deployed by JWS. This is a known   CORBA implementation issue which is fixed in 1.4 release.   To workaround this error in earlier releases 1.3.x of SDK, Sign the    jar file using keytool and jarsigner utility. To do this run :   keytool -genkey -keystore myKeystore -alias myself     jarsigner -keystore myKeystore war/app/HelloWorld.jar jws   Read more details about Signing JAR Files process in    Java Web Start Developer's Guide.     3) ORB dameon and the Hello Server needs to be started first before   executing the client application. If they are already running on a   different machine, then you need not start them on the local machine.   All you need to do is specify the correct hostname and the port number   of the orbd in the helloworld.jnlp file:     <property name="java.naming.provider.url" value="iiop://ord_host:port_number"/>   These values will be used by HelloClient upon started by Java Web Start.       ORB daemon can be started by running the following command :      $JAVA_HOME/bin/orbd -ORBInitialPort <Port Number> &   You can also start using 'gnumake runorbd' command in the current   directory. Please note that you need to modify ORB_INITIAL_   HOST and ORB_INITIAL_PORT values accordingly in the Makefile.      NOTE: orbd tool is shipped only starting with J2SE 1.4 release. Use   Transient Naming Service, tnameserv tool in releases prior to 1.4.   ORBD includes both a Transient Naming Service and a Persistent Naming    Service. If you are using SDK 1.3.x, then it will be   $JAVA_HOME/bin/tnameserv -ORBInitialPort <Port Number> &4) HelloServer should be started next either at the command line      $JAVA_HOME/bin/java -Djava.naming.factory.initial=com.sun.jndi.   cosnaming.CNCtxFactory -Djava.naming.provider.url=iiop://${ORB_INITIAL_   HOST}:${ORB_INITIAL_PORT}  -classpath <value> HelloServer &    or using Makefile command 'gnumake runserver'.5) For HelloClient, the war/app/helloworld.jnlp file consists of two   property elements. Please modify them accordingly especially the   naming provider url.   You can also run 'gnumake runclient' to make sure   everything is working fine in standalone java mode first.    Note: Please make sure that the initial host names and  port numbers used   for starting the orbd should match with the values specified in   java.naming.provider.url property specified during the Client and Server   startup. 6) To ease the deployment of application to on any J2EE-complaint   server all the resources required including .jnlp and jar files   are packed into a Web Archive (.war) file.	   Please put the following files into the war directory:   war/WEB-INF/lib/jnlp-servlet.jar (from building the JNLPDownloadServlet)   war/WEB-INF/lib/<jar files for XML parser> (not needed if servlet container is running J2SE 1.4+; or if the servlet container already comes with a XML parser in it)   war/app/HelloWorld.jar (generated in the lib directory)   To build .war file, run below command inside the war directory   jar -cvf ../rmi-iiop.war .7) Copy rmi-iiop.war file to the your web server directory.   For Tomcat server, copy rmi-iiop.war file to    $TOMCAT_HOME/webapps directory and restart the web server.   HelloClient will be started automatically by Java Web Start when   the link containing .jnlp file is clicked by the User.