ch.ralscha.extdirectspring.controller.SSEWriter.java Source code

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Here is the source code for ch.ralscha.extdirectspring.controller.SSEWriter.java

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/**
 * Copyright 2010-2014 Ralph Schaer <ralphschaer@gmail.com>
 *
 * 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 ch.ralscha.extdirectspring.controller;

import java.io.IOException;

import javax.servlet.http.HttpServletResponse;

import org.springframework.http.MediaType;
import org.springframework.util.StringUtils;

import ch.ralscha.extdirectspring.bean.SSEvent;
import ch.ralscha.extdirectspring.util.ExtDirectSpringUtil;

/**
 * This class allows you to send server sent events in a streaming fashion. Add this class
 * as a parameter to the method and send {@link SSEvent} with {@link #write(SSEvent)} to
 * the client.
 * <p>
 * Example:
 *
 * <pre>
 *  {@literal @}ExtDirectMethod(ExtDirectMethodType.SSE)
 *  public void sse(SSEWriter sseWriter) {
 *    SSEvent event = new SSEvent();
 *    event.set....
 *    sseWriter.write(event);
 *    //do something else or wait for something or ...
 *    sseWriter.write(event);
 *    //...
 *  }
 * </pre>
 */
public class SSEWriter {
    private final HttpServletResponse response;

    private static final MediaType EVENT_STREAM = new MediaType("text", "event-stream",
            ExtDirectSpringUtil.UTF8_CHARSET);

    public SSEWriter(HttpServletResponse response) {
        this.response = response;

        response.setContentType(EVENT_STREAM.toString());
        response.setCharacterEncoding(EVENT_STREAM.getCharSet().name());
    }

    /**
     * Creates a {@link SSEvent} object and sets the data property to the provided
     * parameter. Then it writes the event into the servlet output stream and flushes the
     * response.
     *
     * @param data the value that becomes the data part of the {@link SSEvent}. If null
     * nothing is written.
     * @throws IOException
     */
    public void write(Object data) throws IOException {
        if (data != null) {
            SSEvent sseEvent = new SSEvent();
            sseEvent.setData(data.toString());
            write(sseEvent);
        }
    }

    /**
     * Writes the event into the servlet output stream and flushes the response. The
     * method does not close the output stream.
     *
     * @param sseEvent the event object
     * @throws IOException
     */
    public void write(SSEvent sseEvent) throws IOException {
        StringBuilder sb = new StringBuilder(32);

        if (StringUtils.hasText(sseEvent.getComment())) {
            for (String line : sseEvent.getComment().split("\\r?\\n|\\r")) {
                sb.append(":").append(line).append("\n");
            }
        }

        if (StringUtils.hasText(sseEvent.getId())) {
            sb.append("id:").append(sseEvent.getId()).append("\n");
        }

        if (StringUtils.hasText(sseEvent.getEvent())) {
            sb.append("event:").append(sseEvent.getEvent()).append("\n");
        }

        if (StringUtils.hasText(sseEvent.getData())) {
            for (String line : sseEvent.getData().split("\\r?\\n|\\r")) {
                sb.append("data:").append(line).append("\n");
            }
        }

        if (sseEvent.getRetry() != null) {
            sb.append("retry:").append(sseEvent.getRetry()).append("\n");
        }

        sb.append("\n");
        response.getOutputStream().write(sb.toString().getBytes(ExtDirectSpringUtil.UTF8_CHARSET));
        response.getOutputStream().flush();

    }

}