JDBC

JDBC Application Six Step

• 1.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.
• 2.Register the JDBC driver: Requires that you initialize a driver so you can open a communication channel with the database.
• 3.Open a connection: Requires using the DriverManager.getConnection() method to create a Connection object, which represents a physical connection with the database.
• 4.Execute a query: Requires using an object of type Statement for building and submitting an SQL statement to the database.
• 5.Extract data from result set: Requires that you use the appropriate ResultSet.getXXX() method to retrieve the data from the result set.
• 6.Clean up the environment: Requires explicitly closing all database resources versus relying on the JVM's garbage collection.

//STEP 1. Import required packages
import java.sql.*;

public class JDBCPractice {
   // 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 = "root";
   static final String PASS = "";

   public static void main(String[] args) {
       Connection conn = null;
       Statement stmt = null;
       try{
          //STEP 2: Register JDBC driver
          ////forName(String name, boolean initialize, ClassLoader loader) method returns the Class object associated with the class or interface with the given string name, using the given class loader
          Class.forName("com.mysql.jdbc.Driver");
          //DriverManager.registerDriver(new 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