早速使ってみましょう。
今回はtomcat7.0.41を使用しています。
手始めにチャットを作ってみます。
①WebSocketServlet
tomcatと言えばHttpServletを継承してサーブレットを作成しますが、
websocketは「WebSocketServlet」を継承してサーブレットを作ります。
public class ChatServlet extends WebSocketServlet {
②クライアントからの接続要求
接続が来たらcreateWebSocketInboundが呼ばれます。
接続が来たらcreateWebSocketInboundが呼ばれます。
@Override
protected StreamInbound createWebSocketInbound(String subProtocol, HttpServletRequest request) {
return new EchoMessageInbound(byteBufSize,charBufSize);
}
③上記で生成するEchoMessageInboundクラスを定義します
private static final class EchoMessageInbound extends MessageInbound {
private String name = null;
public EchoMessageInbound(int byteBufferMaxSize, int charBufferMaxSize) {
super();
setByteBufferMaxSize(byteBufferMaxSize);
setCharBufferMaxSize(charBufferMaxSize);
}
@Override
protected void onOpen(WsOutbound outbound) {
super.onOpen(outbound);
peers.add(this);
}
@Override
protected void onClose(int status) {
super.onClose(status);
peers.remove(this);
}
@Override
protected void onBinaryMessage(ByteBuffer message) throws IOException {
System.out.println("onBinaryMessage");
getWsOutbound().writeBinaryMessage(message);
}
@Override
protected void onTextMessage(CharBuffer message) throws IOException {
System.out.println("onTextMessage[" + message + "]");
if( message.toString().indexOf("joined") > 0 ) {
name = message.toString().split(" ")[0];
}
for( EchoMessageInbound u: peers ) {
u.getWsOutbound().writeTextMessage(CharBuffer.wrap(""+message.toString()));
}
}
}
これだけです。
④あとはクライアント側
websocket.js
※これはJavaDayTokyoでデモで使用されたファイルです。
/*
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS HEADER.
*
* Copyright (c) 2013 Oracle and/or its affiliates. All rights reserved.
*
* The contents of this file are subject to the terms of either the GNU
* General Public License Version 2 only ("GPL") or the Common Development
* and Distribution License("CDDL") (collectively, the "License"). You
* may not use this file except in compliance with the License. You can
* obtain a copy of the License at
* https://glassfish.dev.java.net/public/CDDL+GPL_1_1.html
* or packager/legal/LICENSE.txt. See the License for the specific
* language governing permissions and limitations under the License.
*
* When distributing the software, include this License Header Notice in each
* file and include the License file at packager/legal/LICENSE.txt.
*
* GPL Classpath Exception:
* Oracle designates this particular file as subject to the "Classpath"
* exception as provided by Oracle in the GPL Version 2 section of the License
* file that accompanied this code.
*
* Modifications:
* If applicable, add the following below the License Header, with the fields
* enclosed by brackets [] replaced by your own identifying information:
* "Portions Copyright [year] [name of copyright owner]"
*
* Contributor(s):
* If you wish your version of this file to be governed by only the CDDL or
* only the GPL Version 2, indicate your decision by adding "[Contributor]
* elects to include this software in this distribution under the [CDDL or GPL
* Version 2] license." If you don't indicate a single choice of license, a
* recipient has the option to distribute your version of this file under
* either the CDDL, the GPL Version 2 or to extend the choice of license to
* its licensees as provided above. However, if you add GPL Version 2 code
* and therefore, elected the GPL Version 2 license, then the option applies
* only if the new code is made subject to such option by the copyright
* holder.
*/
var wsUri = "ws://" + document.location.host + "/Chat/websocket";
var websocket = new WebSocket(wsUri);
var username;
websocket.onopen = function(evt) { onOpen(evt) };
websocket.onmessage = function(evt) { onMessage(evt) };
websocket.onerror = function(evt) { onError(evt) };
var output = document.getElementById("output");
function join() {
username = textField.value;
websocket.send(username + " joined");
}
function send_message() {
websocket.send(username + ": " + textField.value);
}
function onOpen() {
writeToScreen("Connected to " + wsUri);
}
function onMessage(evt) {
console.log("onMessage");
writeToScreen("RECEIVED: " + evt.data);
if (evt.data.indexOf("joined") != -1) {
userField.innerHTML += evt.data.substring(0, evt.data.indexOf(" joined")) + "\n";
} else {
chatlogField.innerHTML += evt.data + "\n";
}
}
function onError(evt) {
writeToScreen('<span style="color: red;">ERROR:</span> ' + evt.data);
}
function writeToScreen(message) {
output.innerHTML += message + "<br>";
}
⑤最後にhtml index.html
※これはJavaDayTokyoでデモで使用されたファイルを参考にしています。
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>WebSocket Chat</title>
</head>
<body>
<h1>Chat!</h1>
<div style="text-align: center;">
<form action="">
<table>
<tr>
<td>
Users<br/>
<textarea readonly="true" rows="6" cols="20" id="userField"></textarea>
</td>
<td>
Chat Log<br/>
<textarea readonly="true" rows="6" cols="50" id="chatlogField"></textarea>
</td>
</tr>
<tr>
<td colspan="2">
<input id="textField" name="name" value="Duke" type="text"><br>
<input onclick="join();" value="Join" type="button">
<input onclick="send_message();" value="Chat" type="button">
</td>
</tr>
</table>
</form>
</div>
<div id="output"></div>
<script language="javascript" type="text/javascript" src="websocket.js">
</script>
</body>
</html>
⑤完成です
これだけではwebsocketの威力は感じにくいかもしれません。
このチャットアプリを少し応用して複数の人が１つのcanvasに絵が書けるアプリを作ってみました。
とても簡単に作る事ができ、websocketの威力を味わえた気がします。
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