What is JDBC?

JDBC is an acronym for Java Database Connectivity. It’s an advancement for ODBC ( Open Database
Connectivity ). JDBC is a standard API specification developed in order to move data from the front end
to the back end. This API consists of classes and interfaces written in Java. It basically acts as an interface
(not the one we use in Java) or channel between your Java program and databases i.e it establishes a
link between the two so that a programmer can send data from Java code and store it in the database
for future use.

Illustration: Working of JDBC co-relating with real-time

Why JDBC Come into Existence?

As previously told JDBC is an advancement for ODBC, ODBC being platform-dependent had a lot of
drawbacks. ODBC API was written in C, C++, Python, and Core Java and as we know above languages
(except Java and some part of Python )are platform-dependent. Therefore to remove dependence, JDBC
was developed by a database vendor which consisted of classes and interfaces written in Java.

Steps to Connect Java Application with Database

Below are the steps that explains how to connect to Database in Java:

Step 1 – Import the Packages

Let us discuss these steps in brief before implementing by writing suitable code to illustrate connectivity
steps for JDBC.

Step 1: Import the Packages

Step 2: Loading the drivers

In order to begin with, you first need to load the driver or register it before using it in the program.
Registration is to be done once in your program. You can register a driver in one of two ways mentioned
below as follows:

2-A Class.forName()

Here we load the driver’s class file into memory at the runtime. No need of using new or create objects.
The following example uses Class.forName() to load the Oracle driver as shown below as follows:

Class.forName(“oracle.jdbc.driver.OracleDriver”);

2-B DriverManager.registerDriver()
DriverManager is a Java inbuilt class with a static member register. Here we call the constructor of the
driver class at compile time. The following example uses DriverManager.registerDriver()to register the
Oracle driver as shown below:

DriverManager.registerDriver(new oracle.jdbc.driver.OracleDriver())

Step 3: Establish a connection using the Connection class object

After loading the driver, establish connections as shown below as follows:

Connection con = DriverManager.getConnection(url,user,password)

 user: Username from which your SQL command prompt can be accessed.

 password: password from which the SQL command prompt can be accessed.

 con: It is a reference to the Connection interface.

 Url: Uniform Resource Locator which is created as shown below:

String url = “ jdbc:oracle:thin:@localhost:1521:xe”

Where oracle is the database used, thin is the driver used, @localhost is the IP Address where a
database is stored, 1521 is the port number and xe is the service provider. All 3 parameters above are of
String type and are to be declared by the programmer before calling the function. Use of this can be
referred to form the final code.

Step 4: Create a statement

Once a connection is established you can interact with the database. The JDBCStatement,
CallableStatement, and PreparedStatement interfaces define the methods that enable you to send SQL
commands and receive data from your database.
Use of JDBC Statement is as follows:

Statement st = con.createStatement();

Note: Here, con is a reference to Connection interface used in previous step .

Step 5: Execute the query

Now comes the most important part i.e executing the query. The query here is an SQL Query. Now we
know we can have multiple types of queries. Some of them are as follows:

 The query for updating/inserting a table in a database.

The executeQuery() method of the Statement interface is used to execute queries of retrieving values
from the database. This method returns the object of ResultSet that can be used to get all the records of
a table.
The executeUpdate(sql query) method of the Statement interface is used to execute queries of
updating/inserting.

Pseudo Code:

int m = st.executeUpdate(sql);
if (m==1)
System.out.println("inserted successfully : "+sql);
else
System.out.println("insertion failed");

Here sql is SQL query of the type String:

 Java

// This code is for establishing connection with MySQL

// database and retrieving data

// from db Java Database connectivity

/*

*1. import --->java.sql

*2. load and register the driver ---> com.jdbc.

*3. create connection

*4. create a statement

*5. execute the query

*6. process the results

*7. close

*/
import java.io.*;

import java.sql.*;

class GFG {

public static void main(String[] args) throws Exception

String url

= "jdbc:mysql://localhost:3306/table_name"; // table details

String username = "rootgfg"; // MySQL credentials

String password = "gfg123";

String query

= "select *from students"; // query to be run

Class.forName(

"com.mysql.cj.jdbc.Driver"); // Driver name

Connection con = DriverManager.getConnection(

url, username, password);

System.out.println(

"Connection Established successfully");

Statement st = con.createStatement();

ResultSet rs

= st.executeQuery(query); // Execute query

rs.next();

String name
 = rs.getString("name"); // Retrieve name from db

System.out.println(name); // Print result on console

st.close(); // close statement

con.close(); // close connection

System.out.println("Connection Closed....");

Output:

Step 6: Closing the connections

So finally we have sent the data to the specified location and now we are on the verge of completing our
task. By closing the connection, objects of Statement and ResultSet will be closed automatically. The
close() method of the Connection interface is used to close the connection. It is shown below as follows:

con.close();

Example:

 Java

// Java Program to Establish Connection in JDBC

import java.sql.*;

// Importing required classes

import java.util.*;

// Main class

class Main {

// Main driver method

public static void main(String a[])

// Creating the connection using Oracle DB

// Note: url syntax is standard, so do grasp

String url = "jdbc:oracle:thin:@localhost:1521:xe";

// Username and password to access DB

// Custom initialization

String user = "system";

String pass = "12345";

// Entering the data

Scanner k = new Scanner(System.in);

String name = k.next();

System.out.println("enter roll no");

int roll = k.nextInt();

System.out.println("enter class");

String cls = k.next();

// Inserting data using SQL query

String sql = "insert into student1 values('" + name

+ "'," + roll + ",'" + cls + "')";

// Connection class object

Connection con = null;

// Try block to check for exceptions

try {

// Registering drivers

DriverManager.registerDriver(

new oracle.jdbc.OracleDriver());

// Reference to connection interface

pass);

// Creating a statement

Statement st = con.createStatement();

// Executing query

int m = st.executeUpdate(sql);

if (m == 1)

System.out.println(

"inserted successfully : " + sql);

else

System.out.println("insertion failed");

// Closing the connections

con.close();

// Catch block to handle exceptions

catch (Exception ex) {

// Display message when exceptions occurs

System.err.println(ex);

}
 }

Output after importing data in the database: