HelloWorldJDBC_main.java

Hello World. Create & initialize database if not present. Create one record, read and print all records.

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
 
/*

 * helloWorldJDBC: This example program shows the basic steps of creating

 * a JDBC application. This class performs the following. Inserts data into 

 * the database, retrieves the data using a ResultSet object, which is then 

 * displayed out to the screen.This example uses the JNI connection URL. In order 

 * to use JDBC you must specify your connection URL as "jdbc:raima:rdm://localhost" 

 * instead of the JNI which is "jdbc:raima:rdm://local". The comments are javadoc

 * style for consistency.

 * @author Kevin Hooks

 * Date : 2-2-2012

 */

public class HelloWorldJDBC_main {
 
/*

 * main: This method connects to the driver by using the connection URL

 * through JNI (TCP/IP). The database is then opened and cleaned up. 

 * The string "Hello World!" is then inserted into the database. Every 

 * object is initialized to null so that it can be used inside of each

 * block (try, catch, finally).

 * @param args

 * @throws SQLException 

 */

public static void main(String[] args) throws SQLException {
// Connection object used for connecting to driver

 Connection Conn = null; 
 
// Statement object used for executing SQL Statements

 Statement Stmt = null;
 
// Prepared Statement object used for preparing SQL Statements

 PreparedStatement prepStmt = null;
 
// Result Set object used for storing queried values

 ResultSet rs = null;
 
// The try block contains the main portion of the code. The code is contained

// inside here so that if it fails the exception will be caught inside the

// catch blocks.

try

 {
// Connects to driver using connection URL and passed into Connection

// Object

 Conn = DriverManager.getConnection("jdbc:raima:rdm://local");
 
// Creates the Statement object to be used for future SQL Statement

// executions

 Stmt = Conn.createStatement();
 
// Opens database

 Stmt.executeUpdate("USE \"hello_worldJDBC\"");
 
//Used to clear table if there is previous data

 Stmt.executeUpdate("DELETE FROM hello_table");
 
// Prepares the insert statement for execution

 prepStmt = Conn.prepareStatement("INSERT INTO hello_table (f00) VALUES (?)");
 
// Performs a setter method for a string setting the value of the

// parameter above

 prepStmt.setString(1, "Hello World!");
 
//Executes prepared Statement

 prepStmt.execute();
 
// Commits all changes

 Conn.commit();
 
// Executes a select statement and stores queried results in the result

// set

 rs = Stmt.executeQuery("SELECT * FROM hello_table");
 
// Loops through the result set, checking for when the next value is

// null. We only expect 1 iteration. The contents of helloString are

// then received from the getter method. The results are then printed

// to the screen

while (rs.next() != false)
 {
 String helloString = rs.getString(1);
 System.out.println(helloString);
 }
 }
 
// The catch block is used to catch an exceptions that are thrown above and 

// display them to the screen. Currently the only type of exception we can

// expect would be a SQLException otherwise we would have to have another

// catch block for each possible exception 

catch (SQLException exception)
 {
 System.err.println("An exception has occured : " + exception.toString());
 System.exit (1);
 }
 
// The finally block is used to execute after the try block has been

// performed. It is also executed if an exception is thrown, this way you

// can clean up any open objects without missing the .close() on a failure.

// Every object must be closed as you would a handle in ODBC. 

finally

 {
if (rs != null)
 {
 rs.close();
 }
 
if (prepStmt != null)
 {
 prepStmt.close();
 }
 
if (Stmt != null)
 {
 Stmt.close();
 }
 
if (Conn != null)
 {
 Conn.close();
 }
 }
 }
}