Remote Method Invocation

Question 1

(3 steps)

What are the steps involved in Remote Method Invocation?

Answer 1

1. Binding
   
   • Involves the registry and server object
   • Registers methods of a remote object with the registry
2. Lookup
   
   • Involves the registry and client object
   • Checks whether there is an entry in the registry that associates a remote object with a proxy object
3. Invoke
   
   • Involves the client object, proxy object and server object
   • The client object uses the proxy object to make a remote method call

Question 2

(2 answers)

What are the advantages to Remote Method Invocation?

Answer 2

• Layers shield the developer from low-level issues, making development easier and more productive
• The use of names is more convenient and flexible than specifying the full details of a resource - the location of a resource can be changed while the name remains the same

Question 3

(4 answers)

What are the disadvantages to Remote Method Invocation?

Answer 3

• Synchronous protocol
• Higher overhead, due to object serialisation and security management
• Inadequate for event-based or stream-based, data-intensive communication
• Assumes both parties are implemented using Java (homogeneous)

Question 4

What is marshalling?

Answer 4

Marshalling is taking a collection of data items and assembling them into a form suitable for transmission in a message.

Question 5

What are security managers?

Answer 5

Security managers check that operations to be performed conform to a security policy defined by the user.

Without them a JVM can only dynamically load code that can be found in the class path.

Question 6

What is the Java Naming and Directory Interface (JNDI)?

Answer 6

An API for accessing a variet of naming and directory services.

JNDI is provided by the javax.naming package, which includes the Context interface.

The Context interface provides the bind, rebind, list and lookup operations, similar to the RMI registry.