Java RMI: Stubs and Skeletons Explained

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Questions and Answers

What command is used to compile all Java files in the current directory?

The command is javac *.java.

Which command do you use to start the RMI registry on a specific port?

The command is rmiregistry 5000.

What is the main purpose of the `getCustomers()` method in the `BankImpl` class?

The getCustomers() method retrieves a list of all customers from the database.

What is the significance of implementing `java.io.Serializable` in the `Customer` class?

Implementing <code>java.io.Serializable</code> allows instances of <code>Customer</code> to be sent over the network. Signup and view all the answers

What exception does the `getCustomers()` method throw, and why is it important?

The method throws <code>RemoteException</code> due to potential issues with remote communication. Signup and view all the answers

What role does the stub play in RMI communication?

The stub acts as a gateway on the client side, initiating a connection to the remote JVM, marshaling parameters, and returning the result back to the caller. Signup and view all the answers

Explain the function of the skeleton in RMI before Java 2 SDK introduced the stub protocol.

The skeleton received incoming requests, read the parameters, invoked the method on the remote object, and marshaled the result back to the client. Signup and view all the answers

List the three key requirements for any application to be considered a distributed application using RMI.

The application must locate the remote method, provide communication with remote objects, and load class definitions for the objects. Signup and view all the answers

What is the purpose of the `rmic` tool in the context of RMI?

The <code>rmic</code> tool generates stub and skeleton classes for the remote object implementation, enabling communication in the RMI framework. Signup and view all the answers

Describe the initial steps required to create an RMI application.

First, create a remote interface and provide its implementation, followed by compiling the implementation and generating the stub using the <code>rmic</code> tool. Signup and view all the answers

What is the purpose of the `Naming.rebind` method in the `MyServer` class, and how is it used?

The <code>Naming.rebind</code> method is used to bind a remote object to a name in the RMI registry, enabling clients to look it up. In this case, it's binding the <code>BankImpl</code> instance to the name 'rmi://localhost:6666/javatpoint'. Signup and view all the answers

Explain the role of the `Serializable` interface in the serialization process in Java.

The <code>Serializable</code> interface is a marker interface that indicates that a class's objects can be serialized and deserialized. By implementing it, you enable the conversion of an object's state to a byte stream, making it persistable and transferable. Signup and view all the answers

What is the significance of the `writeObject()` and `readObject()` methods in Java serialization?

The <code>writeObject()</code> method is used to serialize an object, converting it into a byte stream, while the <code>readObject()</code> method is used for deserialization, converting the byte stream back into an object. These methods are essential for object persistence. Signup and view all the answers

How does the `MyClient` class retrieve the list of customers and what is printed in the output?

The <code>MyClient</code> class retrieves the list of customers by invoking <code>b.getCustomers()</code> on a remote <code>Bank</code> object. It prints each customer's account number, first name, last name, email, and amount in the output. Signup and view all the answers

Why is serialization considered platform-independent in Java?

Serialization is platform-independent because the byte stream can be generated on one platform and later deserialized on another, not requiring compatibility of the platforms. This enables seamless data transfer across different systems. Signup and view all the answers

What is the purpose of extending the Remote interface when creating a remote interface in an RMI application?

Extending the Remote interface allows the remote object to be accessible from a different JVM, establishing a communication bridge for remote method invocation. Signup and view all the answers

What must be included in the constructor of the class that implements the remote interface?

The constructor must declare RemoteException and can either extend the UnicastRemoteObject class or use its exportObject() method. Signup and view all the answers

What command is used to create stub and skeleton objects in an RMI application, and why are they necessary?

The command <code>rmic AdderRemote</code> is used to create stub and skeleton objects, which are necessary for facilitating communication between the client and server. Signup and view all the answers

When starting the registry service for an RMI application, why is specifying a port number important?

Specifying a port number is important to ensure that the RMI registry listens on the desired port, allowing clients to connect to the correct service. Signup and view all the answers

What role does the Naming class play in the context of an RMI server application?

The Naming class provides methods to bind and retrieve remote objects, effectively enabling clients to locate and invoke methods on those objects. Signup and view all the answers

Flashcards

Remote Interface

A remote interface defines methods that can be invoked by client applications running on different JVMs. It extends the java.rmi.Remote interface and declares java.rmi.RemoteException for all methods.

What is RMI (Remote Method Invocation) in Java?

A Java API used to develop distributed applications. It allows objects in different JVMs to communicate and invoke methods on each other, facilitating distributed communication.

UnicastRemoteObject

The UnicastRemoteObject class provides methods for creating and exporting remote objects. You typically extend this class to implement your remote interface.

What is a Stub in RMI?

A gateway object on the client side. It acts as an intermediary between the client and the remote object. It handles communication, parameter transmission, and result retrieval.