In this article, we'll be discussing some advanced topics and best practices for Kotlin MVC architecture. We'll also be providing some code examples to illustrate these concepts.
One of the most important aspects of Kotlin MVC architecture is how to properly handle requests. There are two ways to do this: through filters and handlers.
Filters are used to pre-process requests before they are handled by handlers. This is useful for tasks such as authentication and authorization, input validation, and logging.
Filters are registered in the application's configuration file:
// Register a filter for all requests
configuration.addFilter("MyFilter", "/*") {
// ...
}
// Register a filter for specific requests
configuration.addFilter("MyFilter", "/my-path") {
// ...
}
Once a filter is registered, it will be invoked for all matching requests. The filter has access to the request's Parameters, Headers, and Body. It can also set Headers and Attributes on the request, which will be available to handlers.
Here's a simple example of a filter that logs all requests:
class RequestLoggingFilter : Filter {
override fun invoke(call: Call, next: Next) {
val request = call.request
val path = request.path
val method = request.method
val query = request.queryString
val headers = request.headers.entries.joinToString { "${it.key}: ${it.value}" }
val body = request.body.asText()
val log = "$method $path $query $headers $body"
println(log)
// Invoke the next filter or handler in the chain
next(call)
}
}
This filter logs the request method, path, query string, headers, and body to the console.
Handlers are used to process requests and generate responses. They have access to the request's Parameters, Headers, Attributes, and Body.
Handlers are registered in the application's configuration file:
// Register a handler for all requests
configuration.addHandler("MyHandler", "/*") {
// ...
}
// Register a handler for specific requests
configuration.addHandler("MyHandler", "/my-path") {
// ...
}
Once a handler is registered, it will be invoked for all matching requests. The handler can set Headers and Attributes on the response, which will be available to filters and other handlers.
Here's a simple example of a handler that returns a "Hello, World!" response:
class HelloWorldHandler : Handler {
override fun invoke(call: Call) {
val response = call.response
response.status = Status.OK
response.body = "Hello, World!"
}
}
This handler sets the response status to 200 OK and the body to "Hello, World!".
Routing is used to map requests to handlers. There are two ways to do this: through configuration and code.
Routing can be configured in the application's configuration file:
configuration.addRoute("MyRoute", "/my-path") {
// ...
}
Once a route is registered, it will be invoked for all matching requests. The route has access to the request's Parameters, Headers, and Body. It can also set Headers and Attributes on the request, which will be available to filters and handlers.
Here's a simple example of a route that maps requests to the "Hello, World!" handler:
class HelloWorldRoute : Route {
override fun invoke(call: Call, next: Next) {
val request = call.request
val path = request.path
if (path == "/hello-world") {
val handler = HelloWorldHandler()
handler(call)
} else {
// Invoke the next route in the chain
next(call)
}
}
}
This route checks the request path. If it's "/hello-world", it invokes the "Hello, World!" handler. Otherwise, it invokes the next route in the chain.
Routing can also be done in code:
val route = Route {
// ...
}
configuration.addRoute(route)
Once a route is registered, it will be invoked for all matching requests. The route has access to the request's Parameters, Headers, and Body. It can also set Headers and Attributes on the request, which will be available to filters and handlers.
Here's a simple example of a route that maps requests to the "Hello, World!" handler:
val route = Route {
val request = it.request
val path = request.path
if (path == "/hello-world") {
val handler = HelloWorldHandler()
handler(it)
} else {
// Invoke the next route in the chain
it.next()
}
}
This route checks the request path. If it's "/hello-world", it invokes the "Hello, World!" handler. Otherwise, it invokes the next route in the chain.
Here are some general best practices to keep in mind when working with Kotlin MVC architecture: