Distributed Applications in the Enterprise Final Exam Topics and Promises Fall 2002

Midterm Topics (that will reappear)

1. Distributed Applications
• Channels (send/receive)
• Distributed objects (RPC/RMI)
• Middleware agent (space/message queue)
2. Bean Pattern
3. Java Event Model
• Listeners
• Single event thread in Java and implications
• Synchronization by adding task to event queue
4. Component Assembly
• Java Beans
• Serialization
• Introspection
5. Security
• Fundamental properties
• privacy
• integrity
• authentication
• non-repudiation
• Symmetric/secret key
• Asymmetric/public key
• Key agreement protocols
• Key management
• Hash functions to create digest
• Digital Signatures
• Timestamping to limit repudiation
6. Databases
• JDBC:
• The process
• PreparedStatement
• CallableStatement
• Transactions
• transaction makes a series of SQL statements appear to be atomic
• ACID
• Atomicity - The entire sequence of actions must be either completed or aborted. The transaction cannot be partially successful.
• Consistency - The transaction takes the resources from one consistent state to another.
• Isolation - A transaction's effect is not visible to other transactions until the transaction is committed.
• Durability - Changes made by the committed transaction are permanent and must survive system failure
• commit or rollback before close

New Topics

1. Remote Method Invocation
• Serializing (marshaling) objects / persistency
• Distributed Objects:
• Creating a service (IDL, skeleton, stub)
• Server action:

   Register service with Object Manager
• Client action:

   Request service from Object Manager
• Object manager action:

   Negotiate with service providers for an object
     Note: This sometimes involves Reflection
   Deliver remote object to client
• Client/Server Interaction:

   Client uses remote object to get services
   Server receives remote messages, provides results
   Arguments and results can be
     by-value (local copy) or
     by reference (remote handle)
   This exchange involves serializing/unserializing objects
• Roles are reversed when server sends messages to remote objects from client
• The above is standard whether Java RMI or CORBA or whatever
2. Web Applications: Servlets
• Container
• load balancing
• serializing unused beans
• LRU strategy
• Access is through container (no retention or passing of handle to object)
• Conatiner managed area for servlets
• Servlets versus CGI
• JSP: When JSP; when servlet?
3. Enterprise Java Beans (EJBs)
• Naming service to register and find bean by name
• Session Beans
• Stateful vs stateless
• Entity Beans
• Relation to database row
• Bean managed versus container managed persistence
• Home interface must include a findByPrimaryKey, as well as create
• Work is offloaded from software development to bean and servlet deployment
4. Message Queues
• Point-to-point
• Publish/subscrbe
• topic
• Messages can have properties set by sender and used by receiver to filter
5. Tuple Spaces
• Transient vs persistent space
• Operations
• notify
• read, readIfExists
• take, takeIfExists
• write
• Pure space has eval and no predicate operations
• Examples
• Provides communication and coordination
• Semaphores
• Arrays
• Embarrassingly parallel problems
• image manipulation
• LOD computation
• Lightweight communicating agents
• Efficient management of space
6. Leases
• Used extensively in Javaspaces, Jini, distributed garbage collection
• Prevents deserted tuples from cluttering space
• Can renew
7. Jini
• Discovery
• Multi- vs Unicast
• Join
• Avoiding a packet storm
• Lookup
• Group and/or attributes
• Remote or local proxy
• Distributed garbage collection (also issue in RMI)
8. CORBA
• IDL (agreements on types and services)
9. Peer-to-peer computing
• General Concepts
• Distributed search
• Pure versus hybrid P2P systems
• JXTA
• Peer groups
• Advertisements (XML right now)
• Peer discovery (peer is subject, not object)
• LAN-based (limited horizon)
• Cascaded (peers in my horizon use peers in theirs)
• Rendezvous (pseudo server for peers)
10. SOAP
11. Intrusion Detection

Promises

1. Something on Java's event handling model
2. Something on serialization (maybe even depth-first search)
3. A question on introspection
4. A question related to encryption/decryption
5. Remember ACID as regards transactions
6. One or more RMI questions
7. One or more Web App questions (servlets/JSP/EJB)
8. A tuple space question (e.g., analyzing an example usage)
9. A P2P question (conceptual)