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Our Address Book App (contd.)

// JDBCDemo1.java import java.sql.*; import java.io.*; /** Demonstrates the use of JDBC to interact with a database. */ public class JDBCDemo1 { /** The JDBC driver. */ private static final String DB_DRIVER = "org.gjt.mm.mysql.Driver"; /** The database URL. */ private static final String DB_URL = "jdbc:mysql:///test_db"; /** Returns a database connection. */ public Connection getConnection() throws ClassNotFoundException, SQLException { Connection con = null; Class.forName(DB_DRIVER); con = DriverManager.getConnection(DB_URL, "", ""); return con; } /** Creates the addressbook table. */ public void createTable(Connection con) throws SQLException { Statement stmt = null; String query; try { query = "create table address_book(" + " nickname varchar(20) not null," + " name varchar(30)," + " email varchar(50)," + " primary key(nickname))"; stmt = con.createStatement(); stmt.executeUpdate(query); } finally { // Clean up if (stmt != null) { stmt.close(); } } } /** Adds an entry to the addressbook. Returns 1 if the entry is added successfully. */ public int add(Connection con, String nickName, String name, String email) throws SQLException { // The return value int n = 0; Statement stmt = null; String query; try { query = "insert into address_book(nickname, name, email)" + " values('" + nickName + "', '" + name + "', '" + email + "')"; stmt = con.createStatement(); n = stmt.executeUpdate(query); } finally { // Clean up if (stmt != null) { stmt.close(); } } return n; } /** Searches for an entry in the addressbook. */ public AddressBookEntry lookup(Connection con, String nickName) throws SQLException { // The return value AddressBookEntry entry = null; Statement stmt = null; ResultSet rs = null; String query; int j; String name; String email; try { query = "select nickname, name, email from address_book" + " where nickname = '" + nickName + "'"; stmt = con.createStatement(); rs = stmt.executeQuery(query); j = 1; if(rs.next()) { // Fetch values nickName = rs.getString(j++); name = rs.getString(j++); email = rs.getString(j++); // Update the return value entry = new AddressBookEntry(nickName, name, email); } } finally { // Clean up try { if (rs != null) { rs.close(); } } catch(Exception ex) {} try { if (stmt != null) { stmt.close(); } } catch(Exception ex) {} } return entry; } /** Main. */ public static void main(String[] args) { JDBCDemo1 jdbcDemo = new JDBCDemo1(); Connection con = null; BufferedReader in; boolean continueFlag = true; String choiceStr; int choice; String nickName; String name; String email; AddressBookEntry entry; try { // Get a database connection con = jdbcDemo.getConnection(); // Obtain a reader for reading standard input for convenience in = new BufferedReader(new InputStreamReader(System.in)); while(continueFlag) { System.out.println(); System.out.println(); System.out.println(" *** Address Book Menu ***"); System.out.println(); System.out.println("Choose your option from 1-4 below"); System.out.println("1. Create the addressbook table"); System.out.println("2. Add an entry to the addressbook"); System.out.println("3. Search an entry in the addressbook"); System.out.println("4. Quit"); System.out.print("Enter your choice [1-4]: "); choiceStr = in.readLine(); try { // Determine the option choice = Integer.parseInt(choiceStr); // Handle option switch(choice) { case 1: // Create table jdbcDemo.createTable(con); printResult("Table created successfully."); break; case 2: // Add an entry System.out.println("Enter the following information."); System.out.print("Nickname: "); nickName = in.readLine(); System.out.print("Name: "); name = in.readLine(); System.out.print("Email: "); email = in.readLine(); jdbcDemo.add(con, nickName, name, email); printResult("Entry added successfully."); break; case 3: // Search an entry System.out.print("Enter the nickname to search: "); nickName = in.readLine(); entry = jdbcDemo.lookup(con, nickName); if (entry != null) { printResult(entry.toString()); } else { printResult("No such nickname in the addressbook."); } break; case 4: // Quit continueFlag = false; break; default: // Invalid choice System.out.println(); System.out.println("Invalid choice."); break; } } catch(NumberFormatException ex) { System.out.println(); System.out.println("Invalid choice."); } } } catch(Exception ex) { ex.printStackTrace(); } finally { // Clean up try { if (con != null) { con.close(); } } catch(SQLException ex) { } // Check if it was a normal exit if (!continueFlag) { System.out.println(); System.out.println("Thank you for using the addressbook."); System.out.println(); } } } /** Prints a result. */ public static void printResult(String msg) { System.out.println(); System.out.println("RESULT: " + msg); } } The Sample Code... Explained »

Nitin runs http://www.TechnoBuff.com, which provides Java developers will the tools, articles and resources they need to succeed.

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News Tags: programming, Java, database, Email, Code

About the author:
Nitin runs http://www.TechnoBuff.com, which provides Java developers will the tools, articles and resources they need to succeed. Many more Java, ASP, PHP, .NET, and C++ articles like this one are available at http://www.devarticles.com. If you're in search of free scripts to help make your life as a developer easier, why not check out http://www.devscripts.com.