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Pre-assessment Questions

Pre-assessment Questions Which of the following refers to the component-based approach of creating distributed applications? Two-tier architecture Three-tier architecture Monolithic architecture Single-tier architecture 2. Which of the following is NOT true for RMI?

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Pre-assessment Questions

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  1. Pre-assessment Questions • Which of the following refers to the component-based approach of creating distributed applications? • Two-tier architecture • Three-tier architecture • Monolithic architecture • Single-tier architecture • 2. Which of the following is NOT true for RMI? • RMI is a specification that enables one JVM to invoke methods of an object located in another JVM. • RMI is implemented on the middle-tier of the three-tier architecture framework. • RMI application run on cross-platform specification. • RMI supports cross-language specification. Network and Distributed Programming in Java

  2. Pre-assessment Questions • 3. RMI registry is a _____. • Server • Client • Middle-tier • Service • Which of the following services is provided by the transport layer in the RMI architecture? • Creating the connection between the client and server • Creating the server objects • Registering the server object • Invoking the remote method Network and Distributed Programming in Java

  3. Pre-assessment Questions • 5. Which system property controls the lease time? • java.rmi.dgc.lease.clean • javax.rmi.dgc.leaseValue • java.rmi.dgc.leaseValue • java.rmi.dgc.lease.dirty Network and Distributed Programming in Java

  4. Solutions to Pre-assessment Questions • 1. b. Three-tier Architecture • 2. d. RMI supports cross-language specification. • 3. d. Service • 4. a. Creating the connection between the client and server • 5. c.java.rmi.dgc.leaseValue Network and Distributed Programming in Java

  5. Objectives • In this lesson, you will learn about: • Transmit files using RMI • Create application using client-side callbacks Network and Distributed Programming in Java

  6. Demonstration-Transmitting Files Using RMI • Problem Statement • Create a distributed application using RMI, where an RMI client can download a file (plain text or binary) from the RMI server. Network and Distributed Programming in Java

  7. Demonstration-Transmitting Files Using RMI (Contd.) • Solution • The steps to create the distributed application using RMI are: • Create the FileRemote interface for the RMI server. • Create the FileRemoteImpl class that implements the FileRemote interface. • Create the RMIFileServer class. • Create the RMIFileClient class. • Run the application. Network and Distributed Programming in Java

  8. Client-Side Callbacks • In client-side callbacks: • The RMI server invokes the method of the RMI client. • The RMI client acts as an RMI server. • The RMI client extends the UnicastRemoteObjcet class. Network and Distributed Programming in Java

  9. Client-Side Callbacks (Contd.) • Creating an Application using Client-Side Callbacks • Create a remote interface for the client • Create a remote interface for the server • Implement the server interface • Implement the client interface • Create an RMI server • Create an RMI client • Run the client and server applications Network and Distributed Programming in Java

  10. Client-Side Callbacks (Contd.) • Creating Remote Interface for the Client • The code to create a remote interface for the RMI client is: • public interface CRemote extends Remote • { • public void displayValue(String s) throws RemoteException; • } Network and Distributed Programming in Java

  11. Client-Side Callbacks (Contd.) • Creating Remote Interface for the Server • The code to create a remote interface for the RMI server is: • public interface SRemote extends Remote • { • public void registerClient(CRemote c) throws RemoteException; • public CRemote getCallback() throws RemoteException; • } Network and Distributed Programming in Java

  12. Client-Side Callbacks (Contd.) • Implementing the Server Interface • The code snippet to implement the server interface is: • public class SRemoteImpl extends SRemote • { public void registerClient(CRemote c) throws RemoteException • { • .. .. .. • } • public CRemote getCallback() throws RemoteException • { • .. .. .. • } • } Network and Distributed Programming in Java

  13. Client-Side Callbacks (Contd.) • Implementing the Client Interface • The code snippet to implement the client interface is: • public class CRemoteImpl extends CRemote • { • public void displayvalue(String s) throws RemoteException • { • .. .. .. • } • } Network and Distributed Programming in Java

  14. Client-Side Callbacks (Contd.) • Creating an RMI Server • The code snippet to create the RMI server is: • public class CallbackServer • { • public static void main (String args []) throws Exception • { • SRemote b = new SRemoteImpl(); • UnicastRemoteObjcet.exportObjcet(b); Naming.rebind(“callback”, b); • } • } Network and Distributed Programming in Java

  15. Client-Side Callbacks (Contd.) • Creating an RMI Client • The code snippet to create the RMI client is: • public class CallbackClient • { • public static void main (String args []) throws Exception • { • CallbackS = (SRemote)Naming.lookup(“rmi://192.168.0.52/callback”); • CallbackC = callbackS.getCallback(); • UnicastRemoteObjcet.exportObjcet(callbackC); • callbackS.registerClient(callbackC); • } • } Network and Distributed Programming in Java

  16. Client-Side Callbacks (Contd.) • Running the Application • The steps to run an RMI application using client-side callbacks are: • Compile all the Java source files. • javac *.java • Generate the stub and skeleton for the RMI server. • rmic SRemoteImpl • Generate the stub and skeleton for the RMI client. • rmic CRemoteImpl • Start the RMI registry. • start rmiregistry • Run the server-side application. • java CallbackServer • Run the client-side application. • java CallbackClient Network and Distributed Programming in Java

  17. Demonstration-Implementing a Chat Application • Problem Statement • Create a chat application using RMI where an RMI server receives a message from one client and sends that message to all other clients. Network and Distributed Programming in Java

  18. Demonstration-Implementing a Chat Application (Contd.) • Solution • The steps to create the chat application using RMI are: • Create the ServerRemote interface for the chat server • Create the ClientRemote interface for the chat client. • Create the ChatServer class that implements the ServerRemote interface. • Create the ChatClient class that implements the ClientRemote interface. • Run the chat application. Network and Distributed Programming in Java

  19. Summary • In this lesson, you learned that: • You use serialization to convert a set of objects into byte streams. The byte streams can be sent from one JVM to another JVM. • When the RMI server calls back a remote method, such as progress feedback, or an alert message to the RMI client, these method calls are called client-side callbacks. • The RMI client calls the exportObject() method of java.rmi.server.UnicastRemoteObject class to allow the RMI server to perform client side callbacks. Network and Distributed Programming in Java

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