Java tutorial
/* * Copyright 2002-2018 the original author or authors. * * 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 * * https://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 org.springframework.http.codec; import java.time.Duration; import org.springframework.lang.Nullable; /** * Representation for a Server-Sent Event for use with Spring's reactive Web support. * {@code Flux<ServerSentEvent>} or {@code Observable<ServerSentEvent>} is the * reactive equivalent to Spring MVC's {@code SseEmitter}. * * @author Sebastien Deleuze * @author Arjen Poutsma * @since 5.0 * @param <T> the type of data that this event contains * @see ServerSentEventHttpMessageWriter * @see <a href="https://www.w3.org/TR/eventsource/">Server-Sent Events W3C recommendation</a> */ public final class ServerSentEvent<T> { @Nullable private final String id; @Nullable private final String event; @Nullable private final Duration retry; @Nullable private final String comment; @Nullable private final T data; private ServerSentEvent(@Nullable String id, @Nullable String event, @Nullable Duration retry, @Nullable String comment, @Nullable T data) { this.id = id; this.event = event; this.retry = retry; this.comment = comment; this.data = data; } /** * Return the {@code id} field of this event, if available. */ @Nullable public String id() { return this.id; } /** * Return the {@code event} field of this event, if available. */ @Nullable public String event() { return this.event; } /** * Return the {@code retry} field of this event, if available. */ @Nullable public Duration retry() { return this.retry; } /** * Return the comment of this event, if available. */ @Nullable public String comment() { return this.comment; } /** * Return the {@code data} field of this event, if available. */ @Nullable public T data() { return this.data; } @Override public String toString() { return ("ServerSentEvent [id = '" + this.id + "\', event='" + this.event + "\', retry=" + this.retry + ", comment='" + this.comment + "', data=" + this.data + ']'); } /** * Return a builder for a {@code SseEvent}. * @param <T> the type of data that this event contains * @return the builder */ public static <T> Builder<T> builder() { return new BuilderImpl<>(); } /** * Return a builder for a {@code SseEvent}, populated with the give {@linkplain #data() data}. * @param <T> the type of data that this event contains * @return the builder */ public static <T> Builder<T> builder(T data) { return new BuilderImpl<>(data); } /** * A mutable builder for a {@code SseEvent}. * * @param <T> the type of data that this event contains */ public interface Builder<T> { /** * Set the value of the {@code id} field. * @param id the value of the id field * @return {@code this} builder */ Builder<T> id(String id); /** * Set the value of the {@code event} field. * @param event the value of the event field * @return {@code this} builder */ Builder<T> event(String event); /** * Set the value of the {@code retry} field. * @param retry the value of the retry field * @return {@code this} builder */ Builder<T> retry(Duration retry); /** * Set SSE comment. If a multi-line comment is provided, it will be turned into multiple * SSE comment lines as defined in Server-Sent Events W3C recommendation. * @param comment the comment to set * @return {@code this} builder */ Builder<T> comment(String comment); /** * Set the value of the {@code data} field. If the {@code data} argument is a multi-line * {@code String}, it will be turned into multiple {@code data} field lines as defined * in the Server-Sent Events W3C recommendation. If {@code data} is not a String, it will * be {@linkplain org.springframework.http.codec.json.Jackson2JsonEncoder encoded} into JSON. * @param data the value of the data field * @return {@code this} builder */ Builder<T> data(@Nullable T data); /** * Builds the event. * @return the built event */ ServerSentEvent<T> build(); } private static class BuilderImpl<T> implements Builder<T> { @Nullable private String id; @Nullable private String event; @Nullable private Duration retry; @Nullable private String comment; @Nullable private T data; public BuilderImpl() { } public BuilderImpl(T data) { this.data = data; } @Override public Builder<T> id(String id) { this.id = id; return this; } @Override public Builder<T> event(String event) { this.event = event; return this; } @Override public Builder<T> retry(Duration retry) { this.retry = retry; return this; } @Override public Builder<T> comment(String comment) { this.comment = comment; return this; } @Override public Builder<T> data(@Nullable T data) { this.data = data; return this; } @Override public ServerSentEvent<T> build() { return new ServerSentEvent<>(this.id, this.event, this.retry, this.comment, this.data); } } }