Establishing JDBC Connection in Java
Before Establishing a JDBC Connection in Java (the front end i.e. your Java Program and the back end i.e. the database) we should learn what precisely a JDBC is and why it came into existence. Now let us discuss what exactly JDBC stands for and will ease out with the help of real-life illustration to get it working.
What is JDBC?
JDBC stands for Java Database Connectivity. JDBC is a Standard API that enables Java applications to interact with databases like (MYSQL, PostgreSQL, etc). This API consists of classes and interfaces written in Java, In other words, we can also say that JDBC acts as a bridge between your Java application(frontend) and the database(backend), allowing you to send and retrieve data between the two systems.
The diagram below demonstrates the workings of JDBC by co-relating its steps to real-world examples.
Steps to Connect Java Applications with Database
Below are the steps that explains how to connect to Database in Java:
- Step 1: Import the Packages
- Step 2: Load the drivers using the forName() method
- Step 3: Register the drivers using DriverManager
- Step 4: Establish a connection using the Connection class object
- Step 5: Create a statement
- Step 6: Execute the query
- Step 7: Close the connections
Java Database Connectivity
Let us discuss these steps in brief before implementing by writing suitable code to illustrate connectivity steps for JDBC.
Step 1: Import the Packages
First, we need to 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:
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”);
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 query for retrieving data.
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”);
on
Example: The below Java program demonstrates how to connect to a MYSQL database, execute a Query, retrieve data and display it.
Note: Here sql is SQL query of the type String.
// 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.sql.*;
class Geeks {
public static void main(String[] args) throws Exception {
String url = "jdbc:mysql://localhost:3306/database_name"; // Database details
String username = "rootgfg"; // MySQL credentials
String password = "gfg123";
String query = "select * from students"; // Query to be run
// Load and register the driver
Class.forName("com.mysql.cj.jdbc.Driver");
// Establish connection
Connection con = DriverManager.getConnection(url, username, password);
System.out.println("Connection Established successfully");
// Create a statement
Statement st = con.createStatement();
// Execute the query
ResultSet rs = st.executeQuery(query);
// Process the results
while (rs.next()) {
String name = rs.getString("name"); // Retrieve name from db
System.out.println(name); // Print result on console
}
// Close the statement and connection
st.close();
con.close();
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: The below Java program demonstrates how to establish a JBDC Connection with an Oracle database.
// Java Program to Establish Connection
// in JDBC with Oracle Database
// Importing database
import java.sql.*;
// Importing required classes
import java.util.*;
// Main class
class Main {
public static void main(String a[]) {
String url = "jdbc:oracle:thin:@localhost:1521:xe"; // Database details
// Username and password to access DB
String user = "system";
String pass = "12345";
// Entering the data
Scanner k = new Scanner(System.in);
System.out.println("Enter name:");
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 {
// Registering drivers
DriverManager.registerDriver(new oracle.jdbc.OracleDriver());
// Establish connection
con = DriverManager.getConnection(url, user, pass);
// Create a statement
Statement st = con.createStatement();
// Execute the query
int m = st.executeUpdate(sql);
if (m == 1)
System.out.println("Inserted successfully: " + sql);
else
System.out.println("Insertion failed");
// Close the connection
con.close();
} catch (Exception ex) {
// Handle exceptions
System.err.println(ex);
}
}
}
}
Output:
