1. An application execution time reducing method performed by an image forming apparatus that includes a non-transitory computer software program organized according to a software structure, for executing an application on a processor of the image forming apparatus, the software structure including the application, an application framework, and a native function providing function, and the application framework including an interface, a middleware, and an application library, the method comprising: executing a first process, in which the application executes the native function providing function via the middleware by: calling the interface from the application; calling the middleware from the interface; calling the native function providing function via the middleware; authenticating the application by the middleware; executing the middleware via the interface from the application; executing the native function providing function from the middleware; and taking information about the native function from the native function providing function; executing the native function by using the information about the native function; notifying the interface of a finish of the application from the middleware; and notifying the application of the finish of the application from the interface; wherein the middleware authenticates the application when executed from the application; and executing a second process, in which the application executes the native function providing function while bypassing the middleware by: registering the information about the native function onto a platform in the application library, when a process of the application is started; executing the native function on the platform by using the information about the native function; and deleting the information about the native function from the platform, when the process of the application is terminated, wherein the information about the native function is registered onto the platform when a digital signature included in the application is authenticated, and the application is terminated when the digital signature is not authenticated; wherein the application and the interface are implemented in JAVA®, and the middleware, the application library, and the native function providing function are used to implement the native function.