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Enterprise Applications: CMSC 838p Lecture Notes - Prof. William Pugh, Study notes of Computer Science

University of MarylandComputer Science
Prof. William Pugh

An overview of enterprise applications, their features, databases, and persistent objects. The document also covers transactions and locking mechanisms. The lecture is part of the cmsc 838p course at the university of x. Students are expected to participate actively and contribute to the course material. Projects include creating and evaluating real projects and studying standard examples.

Typology: Study notes

Pre 2010

Uploaded on 02/13/2009

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Enterprise Applications
CMSC 838p
Logistics
•Check with me if you aren’t officially
registered
–need a mailing list
•homework 1 due Wednesday
–in class; bring a print-out
Grading
•Homeworks 20%
–simply stuff to keep you on your toes
•Class participation 30%
•Projects 30%
•Exams 20%
Class organization
•Small class
•I expect activate participation and help in
developing course material
•SnipSnap page is a group effort
–I expect you to provide content
pf3
pf4
pf5

Partial preview of the text

Download Enterprise Applications: CMSC 838p Lecture Notes - Prof. William Pugh and more Study notes Computer Science in PDF only on Docsity!

Enterprise Applications

CMSC 838p

Logistics

• Check with me if you aren’t officially

registered

– need a mailing list

• homework 1 due Wednesday

– in class; bring a print-out

Grading

• Homeworks 20%

– simply stuff to keep you on your toes

• Class participation 30%

• Projects 30%

• Exams 20%

Class organization

• Small class

• I expect activate participation and help in

developing course material

• SnipSnap page is a group effort

– I expect you to provide content

Infrastructure

• mysql database on verve

  • temporary measure

• 4 dual-processor x86 linux boxes

  • 2 have arrived, 2 more expected next week
  • just for our class

• Other resources available:

  • 24-processor, 24 gigabyte Sun SMP
  • various larger clusters

• Access to prerelease builds of Java 1.

Projects

• Creating and evaluating real projects

– might bring some customers in

• Looking at standard examples and

benchmarks

– Pet Store

– Spec JAppServer

What is an enterprise

application?

Enterprise applications

• E-bay

• Amazon

• Campus course registration system

Persistent Objects

• It is a pain to have to use SQL queries

whenever you want to touch persistent state

• Better to have objects that reflect persistent

state

– and can check integrity rules and other business

logic

Persistent Object solutions

• EJB (Enterprise Java Beans)

– BMP - Beans managed persistence

– CMP - Container managed persistence

  • AppServer provides mapping between beans and database

• Java Data Objects

– Good for small stuff

Databases in one lecture

Transactions

• Atomicity - indivisible set of actions

• Consistency - respects database invariants

  • typically domain specific

• Isolation - ignorant of other, uncommitted

transactions

• Durability - persistent, even in case of system

failure

A song database

• Album:

albumID

title

category

year

• Artist:

artistID

name

• Song:

songID

albumID

title

length

• Performance:

songID

artistID

Relational databases

• Normalized form

– 1st: All attributes are single valued

– 2nd: non-key entries are functionally dependent

on primary key

– 3rd: No transitive dependencies exist

– Also 4th and 5th normal forms

Locking

• Transaction 1 reads current balance

  • sees $

• Transaction 2 reads current balance

  • sees $

• Transaction 2 adds $

  • sets current balance to $

• Transaction 1 adds $

  • sets current balance to $

How to handle

• In threads, we would just use locks

• In databases, can use pessimistic or

optimistic concurrency

– pessimistic concurrency similar to standard

locking

– optimistic: don’t lock

  • fail when committing if anyone else changed data you depended on