Add request handling infrastructure
HandlerMapping, HandlerAdapter, HandlerResultHandler (+ HandlerResult) as the basic request handling contracts. DispatcherHandler to drive overall request handling. DispatcherApp provides minimal implementations of the above contracts enough to put together a running example that returns 200 text/plain "Hello world".
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Rossen Stoyanchev
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/*
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* Copyright 2002-2015 the original author or authors.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package org.springframework.reactive.web;
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import java.nio.charset.Charset;
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import java.util.HashMap;
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import java.util.Map;
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import io.netty.buffer.ByteBuf;
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import io.reactivex.netty.protocol.http.server.HttpServer;
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import org.reactivestreams.Publisher;
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import org.reactivestreams.Subscriber;
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import org.reactivestreams.Subscription;
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import org.springframework.http.MediaType;
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import org.springframework.reactive.web.rxnetty.RequestHandlerAdapter;
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import org.springframework.web.context.support.StaticWebApplicationContext;
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/**
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* @author Rossen Stoyanchev
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*/
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public class DispatcherApp {
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public static void main(String[] args) {
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StaticWebApplicationContext wac = new StaticWebApplicationContext();
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wac.registerSingleton("handlerMapping", SimpleUrlHandlerMapping.class);
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wac.registerSingleton("handlerAdapter", PlainTextHandlerAdapter.class);
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wac.registerSingleton("resultHandler", PlainTextResultHandler.class);
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wac.refresh();
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SimpleUrlHandlerMapping handlerMapping = wac.getBean(SimpleUrlHandlerMapping.class);
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handlerMapping.addHandler("/text", new HelloWorldTextHandler());
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DispatcherHttpHandler dispatcherHandler = new DispatcherHttpHandler();
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dispatcherHandler.initStrategies(wac);
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RequestHandlerAdapter requestHandler = new RequestHandlerAdapter(dispatcherHandler);
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HttpServer<ByteBuf, ByteBuf> server = HttpServer.newServer(8080);
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server.start(requestHandler::handle);
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server.awaitShutdown();
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}
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private static class SimpleUrlHandlerMapping implements HandlerMapping {
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private final Map<String, Object> handlerMap = new HashMap<>();
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public void addHandler(String path, Object handler) {
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this.handlerMap.put(path, handler);
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}
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@Override
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public Object getHandler(ServerHttpRequest request) {
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return this.handlerMap.get(request.getURI().getPath());
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}
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}
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private interface PlainTextHandler {
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Publisher<String> handle(ServerHttpRequest request, ServerHttpResponse response);
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}
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private static class HelloWorldTextHandler implements PlainTextHandler {
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@Override
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public Publisher<String> handle(ServerHttpRequest request, ServerHttpResponse response) {
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return new Publisher<String>() {
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@Override
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public void subscribe(Subscriber<? super String> subscriber) {
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subscriber.onSubscribe(new AbstractSubscription<String>(subscriber) {
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@Override
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protected void requestInternal(long n) {
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invokeOnNext("Hello world.");
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invokeOnComplete();
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}
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});
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}
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};
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}
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}
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private static class PlainTextHandlerAdapter implements HandlerAdapter {
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@Override
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public boolean supports(Object handler) {
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return PlainTextHandler.class.isAssignableFrom(handler.getClass());
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}
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@Override
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public Publisher<HandlerResult> handle(ServerHttpRequest request, ServerHttpResponse response,
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Object handler) {
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PlainTextHandler textHandler = (PlainTextHandler) handler;
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final Publisher<String> resultPublisher = textHandler.handle(request, response);
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return new Publisher<HandlerResult>() {
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@Override
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public void subscribe(Subscriber<? super HandlerResult> handlerResultSubscriber) {
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handlerResultSubscriber.onSubscribe(new AbstractSubscription<HandlerResult>(handlerResultSubscriber) {
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@Override
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protected void requestInternal(long n) {
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resultPublisher.subscribe(new Subscriber<Object>() {
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@Override
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public void onSubscribe(Subscription subscription) {
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subscription.request(Long.MAX_VALUE);
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}
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@Override
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public void onNext(Object result) {
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invokeOnNext(new HandlerResult(result));
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}
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@Override
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public void onError(Throwable error) {
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invokeOnError(error);
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}
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@Override
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public void onComplete() {
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invokeOnComplete();
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}
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});
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}
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});
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}
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};
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}
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}
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private static class PlainTextResultHandler implements HandlerResultHandler {
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@Override
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public boolean supports(HandlerResult result) {
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Object value = result.getReturnValue();
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return (value != null && String.class.equals(value.getClass()));
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}
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@Override
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public Publisher<Void> handleResult(ServerHttpRequest request, ServerHttpResponse response,
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HandlerResult result) {
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response.getHeaders().setContentType(MediaType.TEXT_PLAIN);
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return response.writeWith(new Publisher<byte[]>() {
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@Override
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public void subscribe(Subscriber<? super byte[]> writeSubscriber) {
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writeSubscriber.onSubscribe(new AbstractSubscription<byte[]>(writeSubscriber) {
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@Override
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protected void requestInternal(long n) {
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Charset charset = Charset.forName("UTF-8");
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invokeOnNext(((String) result.getReturnValue()).getBytes(charset));
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invokeOnComplete();
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}
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});
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}
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});
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}
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}
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private static abstract class AbstractSubscription<T> implements Subscription {
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private final Subscriber<? super T> subscriber;
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private volatile boolean terminated;
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public AbstractSubscription(Subscriber<? super T> subscriber) {
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this.subscriber = subscriber;
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}
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protected boolean isTerminated() {
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return this.terminated;
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}
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@Override
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public void request(long n) {
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if (isTerminated()) {
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return;
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}
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if (n > 0) {
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requestInternal(n);
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}
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}
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protected abstract void requestInternal(long n);
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@Override
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public void cancel() {
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this.terminated = true;
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}
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protected void invokeOnNext(T data) {
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this.subscriber.onNext(data);
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}
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protected void invokeOnError(Throwable error) {
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this.terminated = true;
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this.subscriber.onError(error);
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}
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protected void invokeOnComplete() {
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this.terminated = true;
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this.subscriber.onComplete();
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}
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}
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}
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