CD Database Server (CDDB)

Zachary Carter

Alan Savage

Diana Abbas

Kyle Dorman

What Does a CDDB Server Do?

• Provides Internet-based access to CD database

• Database Provides music CD information– Artist– Track Titles– Release Date

• Because most music CDs do not have this information

Why Another CDDB Server?

• Gracenote denies non-certified music players, and only supports CDDB2

• Gracenote is not free

• Provide a platform independent server

• Provide an alternative when other free databases are down

Implementation

• CDDB level 1 protocol– A text-based protocol

• TCP/IP connection

• MySQL and Enterprise JavaBeans (EJB) manage database

• OpenEJB Container

Data Flow

CD Player

Protocol Server

MySQL ServerEJB

Music Player

• Must Support CDDBP level 1

• Client Configuration– Connect via TCP/IP to CDDB server

Server

• CD Player connects to multithreaded server

• Server instantiates a client thread

• Client thread sends and receives data to the CD player

• Client thread uses ServerProtocol to process CD player requests

• Client thread dies when transactions finish

ServerProtocol

• Implements CDDBP level 1 protocol

• Parses and interprets client requests

• Provides appropriately formatted responses

• Requests CD database information from EJBClient

What is an EJB?

• Enterprise Java Bean

• Server-side objects

• Aids in transactions between client and database

• Consists of methods that encapsulate business logic

EJB Architecture

• Three tiers:– The client (makes calls to remote EJBs)– The EJB server (where the container resides)– The database (EJB business methods directly

accesses database)

EJB Container

• Provides support for:– Transactions– Persistence– Management of multiple instances of a given bean– Concurrent execution of many beans– Keeping track of their state

• Does not allow the bean to be accessed directly from the client

• Protects the bean from the client

EJB Analogy

EJB Bean

EJB Container

EJB Server

Operating System

Applications Programs

Operating System

BIOS

Hardware

Layering in EJBsLayering in typical operating system

A High-Level View of an EJB Conversation

• Finding the bean

• Getting access to a bean

• Calling the bean’s methods

EJB Conversation

• Finding a bean: Java Naming and Directory Interface (JNDI)

• Access to a bean: Home Interface

• Calling the bean’s methods: Remote Interface

• Analogous to JNDI: DNS translation from symbolic names

Entity Beans

• Track beans and CDAlbum beans

• Life cycle includes:– Nonexistence– Pooled (Beans exist in the container with no

identity)– Ready (Business methods can be invoked)

MySQL

• An opensource database

• Data elements are organized using primary keys generated by MySQL database

• SQL statements inserts data into the database using a script

Advantages of EJB’s

• Transaction processing

• Persistent storage of objects

• Platform independence

• Multitiered architecture

• “Write once, run anywhere”

Visions

• Implement higher level CDDB protocols• Implement a façade pattern• Index database by discid• Implement search features

– Artist, disc title, track name, genre

• Add file logging– Usage Statistics

• Create a server side GUI

The End!Questions?