3.Java Database Connectivity2

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Java Database Connectivity


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Object ives contd ..

Write Java applications to update a database in

a local or/and remote database

Write a Java program to execute stored

procedures in a database Use Java for front-end development

Understand about JDBC TYPE IV Thin Driver

using Oracle DB connectivity


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Introduction

Databases are the tools used to collect and store

large volumes of data.

Data is collected and stored in the form of tables

consisting of rows and columns.

A DataBase Management System is the softwarewhich enables you to create a database and perform

operations on the data.

All database management systems use a structured

language to perform different kinds of operations ona database.

Every RDBMS provides some kind of programming

facility to develop DBMS applications.


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Java Database Connectivity

JDBC is the software abstraction that interfaces yourJava application with different kinds of databases.

It sits between your application and the database you

want to access.

JDBC provides a set of APIs which is uniform across

all databases, windowing systems, operating

systems and hardware environments.


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JDBC Architecture

A specific RDBMS requires a specific driver. The APIs provided by the JDBC interface layer is

implemented in the driver.

The application programmer does not implement any

of the API.

JDBC architecture


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Objectives

After completing this chapter, the student will be able to:

Explain JDBC

Explain JDBC architecture

Explain JDBC drivers

Explain Javas support for JDBC

Write Java programs to make simple queries

with local or remote databases

Write Java applications to pass parameters toquery statements from program or/and from the

user


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JDBC ODBC Bridge

Along with JDBC, Sun Microsystems delivers onepiece of software called JDBCODBC bridge.

JDBC and ODBC are similar in design.

The JDBC-ODBC bridge enables to access

databases using ODBC drivers from JDBC. JDBCODBC bridge effectively translate the JDBC

API calls into the corresponding ODBC calls.

ODBC drivers are available for almost all types of

databases.

With JDBCODBC bridge, JDBC can access almostall databases.


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Types of JDBC Drivers

JavaSoft has divided JDBC drivers into fourcategories, based on their construction and the type

of database they are intended to support.

These four categories are explained below.

JDBC-ODBC Bridge Drive Direct Network Connection

Native API Driver Direct Network Connection

Network Protocol Driver Indirect Network Connection

Native Protocol Driver Direct Network Connection


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Types of JDBC Drivers

Type 1- This Driver is a JDBC-ODBC bridge that allows Java Program towork with a database using widely available ODBC Driver. The major drawbacks

of this driver is that it is very slow than other driver and it has to be installed and

configured on each users machine.

Type 2- This driver consists of Java classes that work in conjunction with

the non-java native drivers, provided by the vendors, that has to be installed onthe clients machine. This driver is faster than the Type 1 but it also requires

installation and configuration.

Type 3- This driver is a pure Java Network driver (JDBC-Net Driver) that isprovided by some application server and consists of two parts. The first part is

the Clients part which performs a DBMS independent SQL call and the second

part is the SQL call itself which is then translated to specific protocol according

to the middleware vendor.

Type 4- This driver is a pure Java driver which comes as a .zip or .jar filecontaining Java classes that perform direct calls to the Database Server. It does

not need any configuration on the clients machine and can be dynamically

downloaded to the Client.


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Javas Support for JDBC

Javas support for JDBC comes from a set ofinterfaces and classes defined in the java.sql

package.

These interfaces are listed below.

Interface CallableStatement Interface Connection

Interface DatabaseMetaData

Interface Driver

Interface PreparedStatement

Interface ResultSet Interface ResultSetMetaData

Interface Statement

Class DriverManager


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Javas Support for JDBC contd..

The connection interface is used to establish aconnection to the database you want to access.

The connection interface defines the following

methods:

public void close( ) throws SQLException

public Statement createStatement() throws

SQLException ;

public PreparedStatement prepareStatement()

throws SQLException;

The Connection Interface


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The Statement interface is used to send SQL queries

to the database and retrieve a set of data.

SQLstatements can be queries, updates, insertions,

deletions etc.

The Statement interface provides a number of

methods.

public void close( ) throws SQLException;

public boolean execute( String sql ) throws

SQLException;public ResultSet executeQuery(String sql) throws

SQLException

public int executeUpdate ( String sql )

throws SQLException

The Statement Interface


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PreparedStatement interface is used to pass parameters into anSQL Statement.

Since it is extending the Statement interface, all the methods

available in Statement interface are available to

PreparedStatement interface.

In addition, several other methods are available in

PreparedStatement interface.

Parameterised Query:-

String psswd;

PreparedStatement pstmt=con.prepareStatement("SELECT * FROM

AdminTable WHERE pwd=?");

pstmt.setString(1,psswd);

ResultSet rs=pstmt.executeQuery();

The PreparedStatement Interface


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As a result of execution of an SQL statement, one ormore tables of data may be generated.

The methods in the ResultSet interface can be used

to retrieve these data.

public boolean next( ) throws SQLException;

public String getString(int index) throws

SQLException;

public String getString(String column) throws

SQLException;public Integer getInt(String column) throws

SQLException;

The ResultSet Interface


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Java.sql.ResultSetMetaData class can dynamicallyfind out the structure of the underlying database

table.

ResultSet rs = stmt.executeQuery(sqlQuery);

ResultSetMetaData rsMeta = rs.getMetaData();

int colCount = rsMeta.getColumnCount();

for(int i=0; i


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Another option to create a ResultSet is with Scrollable feature., so that thecursor can be moved forward as well as backward.

A two version of the createStatement() method exists which gives us this facility.

The first argument is the type of Scrolling(TYPE_FORWARD_ONLY,TYPE_SCROLL_INSENSITIVE, TYPE_SCROLL_SENSITIVE)

The second argument is used to make the ResultSet read-only or

Updateable

(CONCUR_READ_ONLY or CONCUR_UPDATABLE)

TYPE_FORWARD: moves the cursor forward only

TYPE_SCROLL_INSENSITIVE: Scrolling will not reflect the changes that might have

been done to the result-set.

TYPE_SCROLL_SENSITIVE: Scrolling should reflect the changes that might have

been done to the result-set.

CONCUR_READ_ONLY: open result-set in read-only mode.CONCUR_UPDATABLE: open result-set in updateable mode on cursors current

position

ScrollableResultSet

J S t f JDBC td


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Ex1.Statement smt =

con.createStatement(ResultSet.TYPE_SCROLL_INSENSITIVE,

ResultSet.CONCUR_READ_ONLY);

ResultSet rs = smt.executeQuery(select * from emp);

Ex2.

rs.afterLast();

while(rs.previous()){

int id = rs.getInt();

}

rs.absolute(25) // moves the cursor to the 25th row;

rs.first();

rs.last();

rs.updateString(name,Tango Charlie);

rs.updateRow();

// CONCUR_UPDATABLE option makes the Result Set updateable and This

line will update the name of the user on the cursors current position.

Scrollable Result Set contd

J S t f JDBC td


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CallableStatement interface extendsPreparedStatement interface.

CallableStatement interface can be used to execute

stored SQL procedures in a database.

These procedures may be taking some input

parameters and giving some output values.

The CallableStatement Interface

J S t f JDBC td


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Driver interface provides methods for establishingconnections with specific databases.

Such methods use a URL type string as parameter to

locate and access databases.

This URL string should have the following

characteristics:

It should specify the type of database being

accessed

It should contain database access information like

host name, database name, port number,username, password etc.

The Driver Interface

J S t f JDBC td


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The DriverManager class controls the loading ofdriver specific classes.

Drivers are implemented as a set of .class files.

Drivers are registered with the DriverManager class.

Connection con = DriverManager.getConnection("jdbc:odbc:practice");

The DriverManager Class


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import java.sql.*;

class JDBCSample

{

public static void main(String [] ar)

{

try{

Class.forName("sun.jdbc.odbc.JdbcOdbcDriver"); // It load JDBC Driver into memory

}catch(ClassNotFoundException e)

{

System.out.println("The Exception Massage is:"+e);

}try

{

Connection con = DriverManager.getConnection("jdbc:odbc:practice"); // Establishment of Connection

Statement stmt = con.createStatement(); // Helps to get Statement type of objectResultSet rs = stmt.executeQuery("select * from login"); // Executing Query

while(rs.next())

{

System.out.println(rs.getString("uid"));

System.out.println(rs.getString("pwd"));

}

rs.close();

stmt.close();

con.close();} catch(SQLException e)

{

System.out.println("The SQL Exception is:"+e);

}

}

}

An Example

JDBC E l td


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2nd Example of executeQuery()import java.sql.*;

class JDBC2

{


{

try{


}catch(ClassNotFoundException e)

{

System.out.println("The Exception Massage is:"+e);

}try

{

Connection con = DriverManager.getConnection("jdbc:odbc:testing"); // Establishment ofConnection

Statement stmt = con.createStatement(); // Helps to get Statement type of object

boolean b = stmt.execute("select * from login"); // Executing Query

if(b)

{

System.out.println("uname");

System.out.println("pwd");

}

stmt.close();

con.close();

} catch(SQLException e)

{


}

}

}

JDBC Examples con td..

JDBC E l td


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3rd Example of executeUpdate()JDBC Examples con td..

import java.sql.*;

class JDBC3

{


{

try{


}catch(ClassNotFoundException e){}

try

{

String uname1="tango";

String pwd1="charlie";

Connection con = DriverManager.getConnection("jdbc:odbc:testing"); // Establishment of ConnectionStatement stmt = con.createStatement(); // Helps to get Statement type of object

String query="INSERT INTO login"+"(uname,pwd)"+"VALUES ('"+uname1+"','"+pwd1+"')";

int rowEffected = stmt.executeUpdate(query); // Executing Query

if(rowEffected>0)

{

System.out.println(Success!!!);

}

stmt.close();

con.close();

} catch(SQLException e){}

}

}

JDBC E l td


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4th Example of PreparedStatementJDBC Examples con td..

import java.sql.*;

class JDBC4

{

//Same as previous example

String pwd1="charlie";

Connection con = DriverManager.getConnection("jdbc:odbc:testing"); // Establishment of Connection

PreparedStatement pstmt=con.prepareStatement("SELECT * FROM login WHERE pwd=?");

pstmt.setString(1,pwd1);

ResultSet rs=pstmt.executeQuery();

if(rs.next())

{

System.out.println(rs.getString("uid"));

System.out.println(rs.getString("pwd"));

}

pstmt.close();

con.close();


{


}

}

}

JDBC E amples con td


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5th Example of PreparedStatementJDBC Examples con td..

import java.sql.*;

class JDBC5

{


{ //same as above

try

{

String pwd1="pentium";

String uid="Karnataka";

Connection con = DriverManager.getConnection("jdbc:odbc:testing"); // Establishment of Connection

PreparedStatement pstmt=con.prepareStatement("UPDATE login SET uname=? where pwd=?");

pstmt.setString(1,uid);

pstmt.setString(2,pwd1);int i=pstmt.executeUpdate();

if(i>0)

System.out.println(i+" no of row(s)effected");

pstmt.close();

con.close();


{


}

}

}


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JDBC and Applets

Before, Java security restrictions allowed only alimited JDBC access from applets.

These limitations were:

Applets run, using applet viewer utility, could

access only local databases.

Applets downloaded from an HTTP server could

not use native code.

Another security restriction was that an applet can

establish a network connection only with the

HTTP server from where the applet wasdownloaded.

The applet security restrictions did not allow the

downloading of JDBC classes.

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3.Java Database Connectivity2