Today I'm going to explain a really basic example about using JDBC in our java code.
First of all, we have to create the data we need to extract from our DB.
Create the table Employee as follows:
mysql> use EMP; mysql> create table Employees -> ( -> id int not null, -> age int not null, -> first varchar (255), -> last varchar (255) -> ); Query OK, 0 rows affected (0.08 sec) mysql>
Create Data Records
Finally you create few records in Employee table as follows:
mysql> INSERT INTO Employees VALUES (100, 18, 'Zara', 'Ali'); Query OK, 1 row affected (0.05 sec) mysql> INSERT INTO Employees VALUES (101, 25, 'Mahnaz', 'Fatma'); Query OK, 1 row affected (0.00 sec) mysql> INSERT INTO Employees VALUES (102, 30, 'Zaid', 'Khan'); Query OK, 1 row affected (0.00 sec) mysql> INSERT INTO Employees VALUES (103, 28, 'Sumit', 'Mittal'); Query OK, 1 row affected (0.00 sec) mysql>
There are following six steps involved in building a JDBC application −
- Import the packages: Requires that you include the packages containing the JDBC classes needed for database programming. Most often, using import java.sql.* will suffice.
- Register the JDBC driver: Requires that you initialize a driver so you can open a communication channel with the database.
- Open a connection: Requires using the DriverManager.getConnection() method to create a Connection object, which represents a physical connection with the database.
- Execute a query: Requires using an object of type Statement for building and submitting an SQL statement to the database.
- Extract data from result set: Requires that you use the appropriate ResultSet.getXXX() method to retrieve the data from the result set.
- Clean up the environment: Requires explicitly closing all database resources versus relying on the JVM's garbage collection.
Sample Code
This sample example can serve as a template when you need to create your own JDBC application in the future.Copy and paste the following example in FirstExample.java, compile and run as follows:
//STEP 1. Import required packages import java.sql.*; public class FirstExample { // JDBC driver name and database URL static final String JDBC_DRIVER = "com.mysql.jdbc.Driver"; static final String DB_URL = "jdbc:mysql://localhost/EMP"; // Database credentials static final String USER = "username"; static final String PASS = "password"; public static void main(String[] args) { Connection conn = null; Statement stmt = null; try{ //STEP 2: Register JDBC driver Class.forName("com.mysql.jdbc.Driver"); //STEP 3: Open a connection System.out.println("Connecting to database..."); conn = DriverManager.getConnection(DB_URL,USER,PASS); //STEP 4: Execute a query System.out.println("Creating statement..."); stmt = conn.createStatement(); String sql; sql = "SELECT id, first, last, age FROM Employees"; ResultSet rs = stmt.executeQuery(sql); //STEP 5: Extract data from result set while(rs.next()){ //Retrieve by column name int id = rs.getInt("id"); int age = rs.getInt("age"); String first = rs.getString("first"); String last = rs.getString("last"); //Display values System.out.print("ID: " + id); System.out.print(", Age: " + age); System.out.print(", First: " + first); System.out.println(", Last: " + last); } //STEP 6: Clean-up environment rs.close(); stmt.close(); conn.close(); }catch(SQLException se){ //Handle errors for JDBC se.printStackTrace(); }catch(Exception e){ //Handle errors for Class.forName e.printStackTrace(); }finally{ //finally block used to close resources try{ if(stmt!=null) stmt.close(); }catch(SQLException se2){ }// nothing we can do try{ if(conn!=null) conn.close(); }catch(SQLException se){ se.printStackTrace(); }//end finally try }//end try System.out.println("Goodbye!"); }//end main }//end FirstExample
C:\>javac FirstExample.java C:\>
C:\>java FirstExample Connecting to database... Creating statement... ID: 100, Age: 18, First: Zara, Last: Ali ID: 101, Age: 25, First: Mahnaz, Last: Fatma ID: 102, Age: 30, First: Zaid, Last: Khan ID: 103, Age: 28, First: Sumit, Last: Mittal C:\>
Programming thought of the day:
- Q: What do you call the security outside of a Samsung Store?
- A: Guardians of the Galaxy.
