MELJUN CORTES Advanced prog. java ou module 8

MODULE 8 JAVA DATABASE CONNECTIVITY

LESSON 8 JAVA DATABASE CONNECTIVITY

Leaning Objectives:

Keywords and Phrases

LEARNER

Advanced Programming

JDBC ResultSetConnection String Data SourceExecuteQuery

When you finish this lesson, you will be able to do the following:

Connect to a database using JDBC and perform a simple query.

Update relational data using JDBC to execute updates, inserts, and deletes.

Use callable statements to access database procedures.

Use commit, rollback, and savepoint to build transactional systems.

Submit the proposal for Final Project involving Transactional Processing Application.

INTRODUCTION

JDBC is Java application programming interface that allows the Java

programmers to access database management system from Java code. It was

developed by JavaSoft, a subsidiary of Sun Microsystems.

DATABASE CONNECTIVITY

Java Database Connectivity in short called as JDBC. It is a java API which enables

the java programs to execute SQL statements. It is an application programming

interface that defines how a java programmer can access the database in tabular

format from Java code using a set of standard interfaces and classes written in the Java

programming language.

JDBC has been developed under the Java Community Process that allows multiple

implementations to exist and be used by the same application. JDBC provides methods

for querying and updating the data in Relational Database Management system such as

SQL, Oracle etc.

The Java application programming interface provides a mechanism for dynamically

loading the correct Java packages and drivers and registering them with the JDBC

Driver Manager that is used as a connection factory for creating JDBC connections

which supports creating and executing statements such as SQL INSERT, UPDATE and

DELETE. Driver Manager is the backbone of the jdbc architecture.

Generally all Relational Database Management System supports SQL and we all know

that Java is platform independent, so JDBC makes it possible to write a single database

application that can run on different platforms and interact with different Database

Management Systems.

Java Database Connectivity is similar to Open Database Connectivity (ODBC) which is

used for accessing and managing database, but the difference is that JDBC is designed

specifically for Java programs, whereas ODBC is not depended upon any language.


In short JDBC helps the programmers to write java applications that manage these

three programming activities:

1. It helps us to connect to a data source, like a database.

2. It helps us in sending queries and updating statements to the database and

3. Retrieving and processing the results received from the database in terms of

answering to your query.

JDBC is an API specification developed by Sun Microsystems that defines a uniform

interface for accessing various relational databases. JDBC is a core part of the Java

platform and is included in the standard JDK distribution.

The primary function of the JDBC API is to provide a means for the developer to issue

SQL statements and process the results in a consistent, database-independent manner.

JDBC provides rich, object-oriented access to databases by defining classes and

interfaces that represent objects such as:

1. Database connections

2. SQL statements

3. Result Set

4. Database metadata

5. Prepared statements

6. Binary Large Objects (BLOBs)

7. Character Large Objects (CLOBs)

8. Callable statements

9. Database drivers

10.Driver manager

The JDBC API uses a Driver Manager and database-specific drivers to provide

transparent connectivity to heterogeneous databases. The JDBC driver manager

ensures that the correct driver is used to access each data source. The Driver Manager


is capable of supporting multiple concurrent drivers connected to multiple

heterogeneous databases.

Understanding Connection Object

A Connection object represents a connection with a database. When we connect to a

database by using connection method, we create a Connection Object, which

represents the connection to the database. An application may have one or more than

one connections with a single database or many connections with the different

databases also.

We can use the Connection object for the following things:

1). It creates the Statement, PreparedStatement and CallableStatement objects for

executing the SQL statements.

2). It helps us to Commit or roll back a jdbc transactionn.

3). If you want to know about the database or data source to which you are connected

then the Connection object gathers information about the database or data source by

the use of DatabaseMetaData.

4). It helps us to close the data source. The Connection.isClosed() method returns true

only if the Connection.close() has been called. This method is used to close all the

connection.

Firstly we need to to establish the connection with the database. This is done by using

the method DriverManager.getConnection(). This method takes a string containing a

URL. The DriverManager class, attempts to locate a driver that can connect to the

database represented by the string URL. Whenever the getConnection() method is

called the DriverManager class checks the list of all registered Driver classes that can

connect to the database specified in the URL.


Syntax:

String url = "jdbc: odbc: makeConnection";

Connection con = DriverManager.getConnection(url, "userID", "password");

Basic steps in writing a JDBC Application

This section gives you brief description of JDBC Steps for making connection with the

database, executing the query and showing the data to the user. In this application we

have connected to the MySQL database and retrieved the employee names from the

database. Here are the JDBC Steps to be followed while writing JDBC program:

Loading Driver

Establishing Connection

Executing Statements

Getting Results

Closing Database Connection

Let us now examine the basic steps required in all Java programs to handle JDBC.

Step 1: Loading Drivers

First, you have to load the appropriate driver. You can use one driver from the available

four. However, the JDBC-ODBC driver is the most preferred among developers. In

order to load the driver, you have to give the following syntax:

Class.ForName("sun.jdbc.odbc.JdbcOdbcDriver");

Step 2: Making a Connection

The getConnection() method of the Driver Manager class is called to obtain the

Connection object. The syntax looks like this:

Connection conn = DriverManager.getConnection("jdbc:odbc:<DSN NAME>");


Here, note that getConnection() is a static method, meaning it should be accessed

along with the class associated with the method. You have to give the Data Source

Name as a parameter to this method. (See section below for setting up the Data Source

Name in your computer.)

Step 3: Creating JDBC Statements

A Statement object is what sends your SQL Query to the Database Management

System. You simply create a statement object and then execute it. It takes an instance

of active connection to create a statement object. We have to use our Connection object

"conn" here to create the Statement object "stmt". The code looks like this:

Statement stmt = conn.createStatement();

Step 4: Executing the Statement

In order to execute the query, you have to obtain the Result Set object (similar to

Record Set in Visual Basic) and a call to the executeQuery() method of the Statement

interface. You have to pass a SQL query like select * from students as a parameter to

the executeQuery() method. If your table name is different, you have to substitute that

name in place of students. Actually, the RecordSet object contains both the data

returned by the query and the methods for data retrieval.

The code for the above step looks like this:

ResultSet rs = stmt.executeQuery("select * from students");

If you want to select only the name field, you have to issue a SQL command like Select Name from Student. The executeUpdate() method is called whenever there is a

delete or an update operation.


Step 5: Looping Through the ResultSet

The ResultSet object contains rows of data that is parsed using the next() method, such

as rs.next(). We use the getXXX() method of the appropriate type to retrieve the value

in each field. For example, if your first field name is ID, which accepts Number values,

then the getInt() method should be used. In the same way, if the second field Name

accepts integer String values, then the getString() method should be used, like the

code given below:

System.out.println(rs.getInt("ID"));

Step 6: Closing the Connection and Statement Objects

After performing all the above steps, you have to close the Connection and RecordSet

objects appropriately by calling the close() method. For example, in our code above, we

will close the object as conn.close()and statement object as stmt.close().

The code for the sample program is shown below for your reference:

import java.sql.*;

import java.awt.*;

import java.awt.event.*;

import javax.swing.*;

public class SampleDBConnection extends JFrame implements ActionListener {

JTextField idNo;

JTextField studentName;

JButton next;

JButton addnew;

JPanel p;

static ResultSet res;

static Connection conn;

static Statement stat;


public SampleDBConnection() {

super("My Students");

Container c = getContentPane();

c.setLayout(new GridLayout(5,1));

id = new JTextField(20);

name = new JTextField(20);

next = new JButton("Next");

p = new JPanel();

c.add(new JLabel("Student ID",JLabel.CENTER));

c.add(id);

c.add(new JLabel("Student Name",JLabel.CENTER));

c.add(name);

c.add(p);

p.add(next);

next.addActionListener(this);

pack();

setVisible(true);

addWindowListener(new WIN());

}

public static void main(String args[]) {

SampleDBConnection d = new SampleDBConnection();

try {

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

conn = DriverManager.getConnection("jdbc:odbc:cust");

stat = conn.createStatement();

res = stat.executeQuery("Select * from Students"); // Students is

// the table name

res.next();

}


catch(Exception e) {

System.out.println("Error" +e);

}

d.showRecord(res);

}

public void actionPerformed(ActionEvent e) {

if(e.getSource() == next) {

try {

res.next();

}

catch(Exception ee) {}

showRecord(res);

}

}

public void showRecord(ResultSet res) {

try {

id.setText(res.getString(1));

name.setText(res.getString(2));

}

catch(Exception e) {}

}//end of the main

//Inner class WIN implemented

class WIN extends WindowAdapter {

public void windowClosing(WindowEvent w) {

JOptionPane jop = new JOptionPane();

jop.showMessageDialog(null,"Database","Thanks",

JOptionPane.QUESTION_MESSAGE);

}

} //end of the class


How to Create a Data Source Name

Follow these steps to create a Data Source Name in Windows

Open ODBC 32-bit Icon from the control panel. (Start | Settings)

Click on the Add button and select Microsoft Access Driver.

Select the appropriate driver if you are using other databases.

Enter a name as Data Source Name and browse for your database by clicking

the Select button.

You can also write a short description, but this is optional.

Finally, click on the Finish button.

private static final String accessDBURLSuffix = ";DriverID=22;READONLY=false}";

// Initialize the JdbcOdbc Bridge Driver

static {

try {

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

} catch(ClassNotFoundException e) {

System.err.println("JdbcOdbc Bridge Driver not found!");

}

}

/** Creates a Connection to a Access Database */

public static Connection getAccessDBConnection(String filename) throws

SQLException {

filename = filename.replace('', '/').trim();

String databaseURL = accessDBURLPrefix + filename + accessDBURLSuffix;

return DriverManager.getConnection(databaseURL, "", "");

}


The next example manipulates a simple AddressDir database that contains one table

Addresses with 11 columns: ID, FirstName, LastName, City, StateOrProvince,

PostalCode, Country, EmailAddress, HomePhone, and FaxNumber. The fields other

than ID are all strings. The program provides facilities for inserting new records,

updating existing records and searching for records in the database.

// Inserting into, updating and searching through a database

import java.sql.*;

import java.awt.*;



public class Addresses extends JFrame( )

{

private ControlPanel controls;

private ScrollingPanel scrollArea;

private JTextArea output;

private String url;

private Connection connect;

private JScrollPane textpane;

public Addresses( )\

{

Super(“Address book database application”);

Container c = getContentPane( );

//screen layout

scrollArea = new ScrollingPanel( );

output = new JTextArea(6, 30);

c.setLayout( new BorderLayout( ));

c.add(new JScrollPane(scrollArea), BorderLayout.CENTER);

textpane = new JScrollPane(output);

c.add(textpane, BorderLayout.SOUTH);


//set up database connection

try {

url = “jdbc:odbc:AddressDir”;

Class.forName(“sun.jdbc,odbc,JdbcOdbcDriver”);

Connect = DriverManager.getConnection(url);

Output.append(“Connection successful \n”);

}

catch (ClassNotFoundException cnfex)

{

cnfex.printStackTrace( );

output.append(“Connection Unsuccessful\n” + cnfex.toString( ));

}

controls = new ControlPanel(connect, scrollArea, output);

c.add(controls, BorderLayout.NORTH);

setSize(500,500);

show( );

}

public static void main(String args[ ])

{ Addresses app = new Addresses( );

app.addWindowListener(

new WindowAdapter( ) {

public void windowClosing(WindowEvent e)

{ System.exit(0); }

}

);

} }


// adding record into the table

import java.sql.*;

import java.awt.*;



public class AddAddresses implements ActionListener

{

private ScrollingPanel fields;

private JTextArea output;

private Connection connect;

public AddAddresses(Connection c, ScrollingPanel f, JTextArea o)

{

connection = c;

fields = f;

output = o;

}

public void actionPerformed(ActionEvent e)

{

try{

Statement statement = connection.createStatement( );

if ( !fields.last.getText( ).equals( “”) &&

!fields.first.getText( ).equals(“”) )

{

String query = “INSERT INTO Addresses (“ +

“firstname, lastname, address, city, “ +

“stateorprovince”, postalcode, country, “ +

“emailaddress, homephone, faxnumber” +


“ ) VALUES ( ‘ “+

fields.first.getText( ) + “ ‘ , ‘ “ +

fields.last.getText( ) + “ ‘ , ‘ “ +

fields.address.getText( ) + “ ‘ , ‘ “ +

fields.city.getText( ) + “ ‘ , ‘ “ +

fields.state.getText( ) + “ ‘ , ‘ “ +

fields.zip.getText( ) + “ ‘ , ‘ “ +

fields.country.getText( ) + “ ‘ , ‘ “ +

fields.email.getText( ) + “ ‘ , ‘ “ +

fields.home.getText( ) + “ ‘ , ‘ “ +

fields.fax.getText( ) + “ ‘)” ;

output.append(“\nSending query : “+

connection.nativeSQL(query) + “\n”);

int result = statement.executeUpdate(query);

if ( result == 1)

output.append(“\n Insertion Successful\n”);

else {

output.append(“\n Insertion failed\n”);

fields.first.setText(“”);

fields.last.setText(“”);

fields.address.setText(“”);

fields.city.setText(“”);

fields.state.setText(“”);

fields.zip.setText(“”);

fields.country.setText(“”);

fields.email.setText(“”);

fields.home.setText(“”);

fields.fax.setText(“”);

}

}


else {

output.append(“\nEnter at least first and last name then” +

“press Add\n”);

statement.close( );

}

catch(SQLException sqlex) {

sqlex.printStackTrace( );

output.append(sqlex.toString( ) );

}

}

}


Reading Assignment:

E-books

o http://java.sun.com/docs/books/tutorial/

o http://www.java-samples.com/showtutorial.php?tutorialid=293

o http://roseindia.net/jsp/simple-jsp-example/nesting-try.shtml

Exercises/Written Assignments

1. Define Java Database Connectivity

2. Differentiate the following terms:

a) Driver Manager

b) Connection

3. What are the steps in Creating Database Server Name. Be able to

explain each briefly.

4. Determine what SQL command is used in the following Java statements.

a) Create a table in the database named “myTable”.

stmt.executeUpdate(

"______________ myTable(test_id int," + "test_val char(15) not null)");

b) Insert some values into the table.

_________________( "INSERT INTO myTable(test_id, " +

"test_val) VALUES(1,'One')");

c) stmt.executeUpdate( "__________________ myTable(test_id, " +

"test_val) VALUES(2,'Two')");

d) Display URL and connection information

__________________("URL: " + url);

System.out.println("Connection: " + con);


http://roseindia.net/jsp/simple-jsp-example/nesting-try.shtml

http://www.java-samples.com/showtutorial.php?tutorialid=293

http://java.sun.com/docs/books/tutorial/

e) Get a Statement object

stmt = con._________________();

Case Problem

1. Design and develop a system in your company applying the database

concepts you learned in this module. Your system will have the

functionality of file maintenance and transaction processing.

References/Bibliography




http://www.developer.com/java/data/article.php/3417381/Using-JDBC-with-

MySQL-Getting-Started.htm


http://www.developer.com/java/data/article.php/3417381/Using-JDBC-with-MySQL-Getting-Started.htm

http://www.developer.com/java/data/article.php/3417381/Using-JDBC-with-MySQL-Getting-Started.htm




MELJUN CORTES Advanced prog. java ou module 8

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