Week 11

Question 1

What is dynamic code loading in RMI?

Answer 1

Enables downloading class definitions along with object references during remote method invocation

Allows introducing new behaviors and types to a JVM at runtime

Requires that class definitions are available in a network-accessible location

Question 2

What are class loaders in Java?

Answer 2

Responsible for loading classes into the JVM

Types of class loaders:

Bootstrap Class Loader: Loads core Java libraries

Extensions Class Loader: Loads from platform-specific extension directories

System Class Loader: Loads from the current directory or CLASSPATH

Question 3

How does the class loading process work?

Answer 3

Precedence: Bootstrap → Extensions → System

Example process:

Y y = new Y();

is internally executed as:

Y y = X.class.getClassLoader().loadClass(“Y”).newInstance();

Question 4

Can you develop custom class loaders?

Answer 4

Yes, by extending java.lang.ClassLoader

Enables adding new classes dynamically at runtime without restarting the application

Often leveraged by RMI for dynamic behavior

Question 5

What are stubs in RMI?

Answer 5

Client-side proxies that represent remote objects

Implement the same interfaces as the remote object, enabling seamless method calls

Question 6

What is the RMI architecture?

Answer 6

Application Layer: Contains client and server programs

Stub and Skeleton Layer: Handles method invocation and redirection

Remote Reference Layer: Manages remote object references

Transport Layer: Based on TCP/IP for communication

Question 7

How do distributed and non-distributed models differ?

Answer 7

Distributed model:

Clients interact with remote interfaces, not implementation classes

Non-remote arguments/results are passed by copy

Remote objects are passed by reference

Remote method invocations can fail due to network or remote errors

Question 8

How are distributed and non-distributed models similar?

Answer 8

Both can:

Pass remote object references as arguments or results

Use casting with remote interfaces

Use instanceof to check remote interface compatibility

Question 9

What are the limitations of RMI?

Answer 9

Requires all class definitions to be accessible

Additional exceptions for remote invocations

Performance overhead due to serialization and network latency

Question 10

How is RMI used in enterprise applications?

Answer 10

Enables distributed services across multiple machines

Supports dynamic runtime behavior through class loading

Common in thin-client architectures where the server handles most processing