It seems that you shouldn't initialize your driver as WebDriver driver = null;
It should be just WebDriver driver;
In addition you write
public WebDriver initDriver(){
if (driver == null ){
driver = new FirefoxDriver();
driver.get("http://mysite")}
}
But if you want to have single browser you should have
public WebDriver initDriver(){
if (driver == null) {
driver = new FirefoxDriver();
}
return driver;
}