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- package database;
- import java.sql.Connection;
- import java.sql.DriverManager;
- import java.sql.ResultSet;
- import java.sql.SQLException;
- import com.mysql.jdbc.Statement;
- public class DatabaseConnection {
- // JDBC driver name and database URL
- private final String JDBC_DRIVER = "com.mysql.jdbc.Driver";
- private String DB_URL = "jdbc:mysql://localhost/";
- private String DB_NAME;
- private Connection connection = null;
- // Database credentials
- static final String USER = "user";
- static final String PASS = "pass";
- public DatabaseConnection(String databaseName) {
- DB_NAME = databaseName;
- DB_URL = DB_URL + DB_NAME;
- }
- public Connection getConnection() {
- if (connection == null) {
- connection = getNewConnection();
- }
- return connection;
- }
- public Connection getNewConnection() {
- try{
- //STEP 2: Register JDBC driver
- Class.forName("com.mysql.jdbc.Driver");
- //STEP 3: Open a connection
- System.out.println("Connecting to database...");
- connection = DriverManager.getConnection(DB_URL,USER,PASS);
- System.out.println("Connected successfully");
- return connection;
- }catch(SQLException se){
- //Handle errors for JDBC
- se.printStackTrace();
- }catch(Exception e){
- //Handle errors for Class.forName
- e.printStackTrace();
- }
- return null;
- }
- public static void main(String[] args) {
- DatabaseConnection db = new DatabaseConnection("students");
- Connection conn = db.getConnection();
- Statement stmt = null;
- try{
- //STEP 4: Execute a query
- System.out.println("Creating statement...");
- stmt = (Statement) conn.createStatement();
- String sql;
- sql = "SELECT id, name FROM students";
- 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 name = rs.getString("name");
- // Float mark = rs.getFloat("mark");
- //Display values
- System.out.print("ID: " + id);
- // System.out.print(", Age: " + age);
- System.out.print(", Name: " + name);
- // System.out.println(", Mark: " + mark);
- }
- //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
- }
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