io.datakernel.http.AsyncServlet Maven / Gradle / Ivy

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/*
 * Copyright (C) 2015 SoftIndex LLC.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package io.datakernel.http;

import io.datakernel.async.Promise;
import io.datakernel.async.Promises;
import io.datakernel.exception.UncheckedException;
import org.jetbrains.annotations.NotNull;

import java.util.concurrent.Executor;
import java.util.function.Function;
import java.util.stream.Stream;

/**
 * An interface for a servlet function that asyncronously receives a {@link HttpRequest},
 * processes it and then returns a {@link HttpResponse}.
 */
@FunctionalInterface
public interface AsyncServlet {
	@NotNull
	Promise serve(@NotNull HttpRequest request) throws UncheckedException;

	default AsyncServlet then(AsyncServletDecorator decorator) {
		return decorator.serve(this);
	}

	@NotNull
	static AsyncServlet of(@NotNull Function fn) {
		return request -> Promise.of(fn.apply(request));
	}

	/**
	 * Wraps given {@link BlockingServlet} into async one using given {@link Executor}.
	 */
	@NotNull
	static AsyncServlet ofBlocking(@NotNull Executor executor, @NotNull BlockingServlet blockingServlet) {
		return request -> request.loadBody()
				.then($ -> Promise.ofBlockingCallable(executor,
						() -> blockingServlet.serve(request)));
	}

	Promise NEXT = Promise.of(null);

	static AsyncServlet firstSuccessful(AsyncServlet... servlets) {
		return httpRequest -> Promises.first(
				(httpResponse, e) -> e == null && httpResponse != null,
				Stream.of(servlets).map(servlet -> () -> servlet.serve(httpRequest)));
	}
}