G53ACC Advanced Computer Communications

1
G53ACC Advanced Computer Communications

• Remote Method Invocation
• Dynamic Class Loading
• From the book Beginning Java Networking by
  Darby et al.

2
School Grading System

• Remote interface
• import java.rmi.
• public interface SchoolGrades extends Remote
• public int getAverage ()
• throws RemoteException

3
School Grading SystemServer Implementation

• Implement defined interface
• import java.rmi.
• public class SchoolGradesServer extends
  UnicastRemoteObject implements SchoolGrades
• static int subjectGrades
• .... initialises subject grades from database
  ....
• public SchoolGradesServer() throws
  RemoteException
• super()
• public int getAverage ()
• throws RemoteException
• method for calculating average
• return (sumOfAllSubjects / numOfSubjects)

4
School Grading SystemServer Implementation (Cont)

• public static void main(String args)
• try
• SchoolGradesServer server new
  SchoolGradesServer()
• Naming.rebind(/GradingService, server)
• ... ...

5
School Grading SystemClient Implementation

• import java.rmi.
• public class SchoolGradesClient
• Static SchoolGrades g null
• public static void main(String args)
• try
• g (SchoolGrades) Naming.lookup
  (//host/GradingService)
• System.out.println(Avarage grade is
  g.getAverage() out of 100)
• ... ...

6
Flexible School Grading System

• Remote interface
• import java.rmi.
• public interface FlexSchoolGrades extends Remote
  
• public int getAverage (GradingScheme scheme)
• throws RemoteException

7
Flexible School Grading System

• GradingScheme interface
• import java.rmi.
• public interface GradingScheme
• public int computeAverage (int subjectScores)

8
Flexible School Grading System

• Define first computation method
• public class AverageScheme implements
  GradingScheme, java.io.Serializable
• public int computeAverage (int subjectScores)
  
• ... algorithm 1 ...
• return (sumOfAllSubjects / numOfSubjects)

9
Flexible School Grading System

• Define second computation method
• public class WeightedScheme implements
  GradingScheme, java.io.Serializable
• public int computeAverage (int subjectScores)
  
• ... algorithm 2 ...
• return (WeightedSumOfAllSubjects / sumOfWeights)

10
Flexible School Grading System

• Implement defined interface for server
• import java.rmi.
• public class FlexSchoolGradesServer extends
  UnicastRemoteObject implements FlexSchoolGrades
• static int subjectGrades
• .... initialises subject grades from database
  ....
• public FlexSchoolGradesServer() throws
  RemoteException
• super()
• public int getAverage (GradingScheme scheme)
• throws RemoteException
• return (scheme.computeAverage (subjectGrades))

11
Flexible School Grading System

• public static void main(String args)
• if (System.getSecurityManager() null)
• System.SetSecurityManage(new RMISecurityManage())
  
• try
• FlexSchoolGradesServer server new
  FlexSchoolGradesServer()
• Naming.rebind(/FlexGradingService, server)
• ... ...

12
Flexible School Grading SystemClient
Implemetation

• import java.rmi.
• public class FlexSchoolGradesClient
• static FlexSchoolGrades g null
• public static void main(String args)
• GradingScheme scheme null
• try
• g (FlexSchoolGrades) Naming.lookup
  (//host/FlexGradingService)
• if ((args.length gt 0) (args0.equals(-w)))
  
• scheme new WeightedScheme()
• else
• scheme new AverageScheme()
• System.out.println(Avarage grade is
  g.getAverage(scheme) out of 100)
• ... ...