Java DataBase Connectivity

Kainjan M. Sanghavi

Importance of Database

The data in a Java program vanishes when the program terminates

Data

But Most Data must be stored and maintained for years

Relational databases are used for this

SetUp from Java to maintain database

Simplest approach:

• Use JDBC = Java Database Connectivity

Why Use JDBC

Before JDBC what was

used ODBC

Written in ‘C’

Thus , Sun Microsystem

Uses JDBC

Not Platform Indepen

dent And Also Unsecur

ed

Java DataBase Connectivity

JDBC Is a Java API that is used to connect and query to the database

JDBC API

Java Application

JDBC Driver Database

JDBC API uses uses JDBC driver to connect to the database

API

Application Program Interface

Document that contains description of all features of a product or software

It represents classes and interfaces that program can follow to communicate with each other

API can be created for applications, operating system etc

JDBC Drivers

Software Component that enables Java Application to interact with database

• JDBC- ODBC Bridge Driver

• Native API- Driver ( Partially Java Driver)

• Network Protocol Driver

• Thin Driver

Types of Drivers

JDBC – ODBC Bridge

JDBC API

Java Application

JDBC – ODBC Bridge Driver

Vendor Database

Library

ODBC Driver

Client Machine

Database

Native API

JDBC API

Java Application

Native API Driver

Vendor Database

Library

Client Machine

Database

Network Protocol

JDBC API

Java Application

Network Protocol

Driver

Client Machine

Database Middle Ware

Server Side

Thin Driver

JDBC API

Java Application

Thin Driver

Client Machine

Database

Creating a DSN for MS Access

• Click: Start • Control Panel • Administrative Tools • Data Sources (ODBC) • User DSN • Add • MS Access Database • Name : Browse the path of your database file (mdb) -> For eg : C:\Program Files\Microsoft Office\OFFICE11\SAMPLES\Northwind.mdb

Overview of Connecting Java Application with Database

Query

Close

Connect

Process results

Stage 1 : Connect

Query

Close

Connect

Process results

Register the driver

Connect to the database

Stage 1 : a. Register Driver

The forName( ) of class ‘ Class’ is used to register the driver class . This method dynamically load the driver class

import java.sql.*;

// Load the vendor specific driver Class.forName("oracle.jdbc.driver.OracleDriver");

OR sun.jdbc.odbc.JdbcOdbcDriver ( if Jdbc-odbc Driver) …….and many more drivers are possible

Stage 1 : b. Connect to database

The getConnection ( ) of class ‘ DriverManager’ is used to establish connection with database

Connection con = DriverManager.getConnection ( "jdbc:oracle:thin:@oracle-prod:1521:OPROD", username, passwd);

Connection conn = DriverManager.getConnection (URL, userid, password);

OR (jdbc:odbc:dsn , username,passwd ) ( if Jdbc-odbc Driver) …….and many more drivers are possible

Stage 2 : Query Database

Query

Close

Connect

Process results

Create a statement

Query the database

Stage 2 : a. Create a statement

A Statement object sends your SQL statement to the database.

You need an active connection to create a JDBC statement.

Statement has three methods to execute a SQL statement:

• executeQuery() for SELECT statements

• executeUpdate() for INSERT, UPDATE, DELETE, or DDL statements

• execute() for either type of statement

Stage 2 : a. Create a statement

Create an empty statement object. ;

Stage 2 : b. Query the database

ResultSet rset = stmt.executeQuery(statement);

int count = stmt.executeUpdate(statement);

boolean isquery = stmt.execute(statement);

Querying Database Examples

String createLehigh = "Create table Lehigh " + "(SSN Integer not null, Name VARCHAR(32), " + "Marks Integer)"; stmt.executeUpdate(createLehigh);

Execute a create statement.

Execute a select statement.

Statement stmt = conn.createStatement();

ResultSet rset = stmt.executeQuery

("select RENTAL_ID, STATUS from ACME_RENTALS");

Querying Database Examples

Statement stmt = conn.createStatement();

int rowcount = stmt.executeUpdate

("delete from ACME_RENTAL_ITEMS

where rental_id = 1011");

Execute a delete statement.

Execute a insert statement.

String insertLehigh = "Insert into Lehigh values“ + "(123456789,abc,100)"; stmt.executeUpdate(insertLehigh);

Stage 3 : Process Results

Query

Close

Connect

Process results

Step through Results

Assign results to Java variables

Stage 3 : Process Results

while (rset.next()) { … }

1. Step Through the results

Stage 3 : Assign values to Java variables

Use getXXX() to get each column value

Stage 3 : Process Results

String queryLehigh = "select * from Lehigh"; ResultSet rs = Stmt.executeQuery(queryLehigh); //What does this statement do? while (rs.next()) { int ssn = rs.getInt("SSN"); String name = rs.getString("NAME"); int marks = rs.getInt("MARKS"); }

Stage 4 : Close

Query

Close

Connect

Process results

Close the resultset

Close the statement

Close the connection

Stage 4 : Close

rset.close();

1. Close resultset

2. Close Statement

stmt.close();

3. Close Connection

conn.close();

Sample Program

import java.sql.*; class Test { public static void main(String[] args) { try { Class.forName("sun.jdbc.odbc.JdbcOdbcDriver"); //dynamic loading of driver Connection con = DriverManager.getConnection( “jdbc:odbc:KMS” ,"",""); Statement s = con.createStatement(); s.execute("create table TEST12345 ( firstcolumn integer )"); s.execute("insert into TEST12345 values(1)"); s.execute("select firstcolumn from TEST12345");

Sample Program

ResultSet rs = s.getResultSet(); if (rs != null) // if rs == null, then there is no ResultSet to view while ( rs.next() ) // this will step through our data row-by-row { /* the next line will get the first column in our current row's ResultSet s a String ( getString( columnNumber) ) and output it to the screen */ System.out.println("Data from column_name: " + rs.getString(1) ); } s.close(); // close Statement con.close(); //close connection } catch (Exception err) { System.out.println("ERROR: " + err); } } }