Database andJava Database Connectivity

Gary 2013/06/13

Outline

• Database

• Distributed database

• Relational Database

• JDBC

• JDBC Implementation

• Future Work

Database

• What is database?

– A database is an organized collection of data. The data is typically organized to model relevant aspects of reality (for example, the availability of rooms in hotels), in a way that supports processes requiring this information (for example, finding a hotel with vacancies).

Database

• Database system consists of

– User

– Data

– Hardware

• Where data resides

– Software

• Database management system(DBMS)

• Controls storage and retrieval

Database

• The advantage of database

– Reduce redundancy

– Avoid inconsistency

– Share data

– Enforce standards

– Security restrictions

– Data integrity

– Balance conflicting requirement

Database

• Non-database systems

– Each application has its own files

• Redundant

• Lack centralized control

Database

• Data independence

– Applications not dependent on how data stored or accessed

– Applications can have different views of data

– Change storage/retrieval strategy without changing applications

• Data dependency

– Change in storage or retrieval technique forces program change

Database

• Database language

– Host languages

• Used to access database

• Can use high-level languages– Java, C, C++, Visual Basic, COBOL, PL/I, Pascal

– Database sublanguage(DSL)

• Specifics of database objects and operations

• Combination of – Data definition language(DDL)

– Data manipulation language(DML)

Database

• Embedding SQL statements in a host language

Distributed database

• A distributed database is a database in which storage devices are not all attached to a common processing unit such as the CPU, controlled by a distributed database management system. It may be stored in multiple computers, located in the same physical location; or may be dispersed over a network of interconnected computers.

Distributed database

• Pros– Local autonomy or site autonomy

• a department can control the data about them (as they are the ones familiar with it)

– Protection of valuable data• if there were ever a catastrophic event such as a fire, all of the

data would not be in one place, but distributed in multiple locations

– Modularity• systems can be modified, added and removed from the distributed

database without affecting other modules

– Continuous operation• even if some nodes go offline (depending on design, like backup)

Distributed database

• Cons

– Complexity

– Economics

– Security

– Difficult to maintain integrity

Relational Database

• A relational database is a database that has a collection of tables of data items, all of which is formally described and organized according to the relational model.

Relational Database

• Composed of tables

– Rows called records(tuples)

– Columns are fields(attributes)

• First field usually primary key

– Unique for each record

– Primary key can be more than one field

– Cannot allow null values

Relational Database

• Example

Relational Database

• Operations

– Projection

• Taking a subset of a table

– Join

• Combining tables to form a larger on (by foreign key)

Relational Database

• Example of projection

Relational Database

• Advantages of relational database

– Tables easy to use, understand, and implement

– Projection and join operations easy to implement

– Easy to modify

– Great clarity and visibility

JDBC

• JDBC is an API for the Java programming language that defines how a client may access a database. It provides methods for querying and updating data in a database. JDBC is oriented towards relational databases. A JDBC-to-ODBC bridge enables connections to any ODBC-accessible data source in the JVM host environment.

JDBC

• Architecture

JDBC

• There are four type of JDBC

– JDBC bridge

– Native-API bridge

– JDBC-Net

– Native-Protocol

JDBC

• JDBC bridge

• Ex: Microsoft Access Database

Java APP

JDBC API

JDBC-ODBCBridge

ODBC API

ODBC Layer

DB

JDBC

• Native-API bridge

Java APP

JDBC API

Native-APIBridge

Native API

DB

JDBC

• JDBC-Net

Java APP

JDBC API

JDBC-NetMiddleware

or Server

DB

JDBC

• Native-Protocol

• Ex: MySQL

Java APP

JDBC API

Native-Protocol

DB

JDBC Implementation

• Establish database

JDBC Implementation

– Has classes and Interfaces for using relational databases

– Implements interface Connection

– Manages connection between database and program

4 import java.sql.*;

11 private Connection connection;

JDBC Implementation

– Database URL(location)username to log in password

– URL

• Protocol for communcation(jdbc)

• Subprotocol(odbc)

• Database name(Books)

19 String url = "jdbc:odbc:Books";

20 String username = "anonymous";

21 String password = "guest";

JDBC Implementation

– Static method forName ()

– Static method getconnection

• Attempt connection to database

• Name and password required

25 Class.forName( "sun.jdbc.odbc.JdbcOdbcDriver" );

27 connection = DriverManager.getConnection(

28 url, username, password );

JDBC Implementation

• Other JDBC driver usage

– MySQL

– Oracle

– Sybase

– Postgresql

JDBC Implementation

– The statement object• Submits query to database

– Returns resultset object containing results

– Statement.executeUpdate• Change data in database

– Statement.executeQuery• Only query

49 Statement statement;

55 statement = connection.createStatement();

53 String query = "SELECT * FROM Authors";

50 ResultSet resultSet;

56 resultSet = statement.executeQuery( query );

JDBC Implementation

– Statement closed when done

– Unlock database

58 statement.close();

Conclusion

Future Wrok

• Servelets

– A servlet is a Java programming language class used to extend the capabilities of a server. Although servlets can respond to any types of requests, they are commonly used to extend the applications hosted by web servers, so they can be thought of as Java Applets that run on servers instead of in web browsers.