websocket基于java的demo

发表于 | 分类于

用java做后端开发的一个websocket小demo。

效果

后端部分

提供给前端的连接类：

MessageConnector.java
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
package message;

import com.google.gson.Gson;
import message.bean.TextMessage;

import javax.websocket.*;
import javax.websocket.server.PathParam;
import javax.websocket.server.ServerEndpoint;
import java.io.IOException;
import java.time.LocalDateTime;
import java.time.format.DateTimeFormatter;

@ServerEndpoint("/message/{clientId}")
public class MessageConnector {

    private static MessageConversation conversation = new MessageConversation();
    private String clientId;

    @OnOpen
    public void onOpen(@PathParam("clientId") String clientId, Session session) throws IOException {
        this.clientId = clientId;
        MessageClient existsClient = conversation.findClient(clientId);
        if (existsClient != null) {
            conversation.unregisterClient(existsClient);
        }
        conversation.registerClient(new MessageClient(clientId, session));
        System.out.println("新的客户端已登入：" + clientId);
    }

    @OnClose
    public void onClose() throws IOException {
        conversation.unregisterClient(conversation.findClient(clientId));
        System.out.println("客户端已退出：" + clientId);
    }

    @OnMessage
    public void onMessage(String message) throws IOException {
        System.out.println("收到消息：" + message);
        TextMessage textMessage = new Gson().fromJson(message, TextMessage.class);
        textMessage.time = LocalDateTime.now().format(DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss"));
        conversation.dispatchMessage(textMessage);
    }

    @OnError
    public void onError(Session session, Throwable error) {
        conversation.unregisterClient(conversation.findClient(clientId));
        System.out.println("客户端意外退出：" + clientId);
        error.printStackTrace();
    }
}

会话类：

MessageConversation.java
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
package message;

import com.google.gson.Gson;
import message.bean.TextMessage;

import java.util.HashSet;
import java.util.Set;

public class MessageConversation {
    private Set<MessageClient> clients = new HashSet<>();

    public MessageConversation() {
    }

    public void registerClient(MessageClient client) {
        clients.add(client);
    }

    public void unregisterClient(MessageClient client) {
        clients.remove(client);
    }

    public MessageClient findClient(String clientId) {
        return clients.stream().filter(client -> client.id.equals(clientId)).findFirst().orElse(null);
    }

    public void dispatchMessage(TextMessage textMessage) {
        clients.forEach(client -> {
            if (!textMessage.from.clientId.equals(client.id)) {
                client.session.getAsyncRemote().sendText(new Gson().toJson(textMessage));
            }
        });
    }
}

客户端类:

MessageClient.java
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
package message;

import javax.websocket.Session;
import java.util.Objects;

public class MessageClient {
    public String id;
    public Session session;
    public String name;

    public MessageClient(String id, Session session) {
        this.id = id;
        this.session = session;
    }

    @Override
    public boolean equals(Object o) {
        if (this == o) return true;
        if (o == null || getClass() != o.getClass()) return false;
        MessageClient that = (MessageClient) o;
        return Objects.equals(id, that.id);
    }

    @Override
    public int hashCode() {
        return Objects.hash(id);
    }
}

简单的消息类：

TextMessage.java
1
2
3
4
5
6
7
8
9
10
11
12
package message.bean;

public class TextMessage {

    public String text;
    public From from;
    public String time;
    public static class From {
        public String clientId;
        public String name;
    }
}

注意事项
依赖了：websocket标准和gson; websocket的jar包在tomcat的lib文件夹下有，gson的jar包需要到maven仓库中下载。

前端部分：

index.html
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
<!doctype html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport"
          content="width=device-width, user-scalable=no, initial-scale=1.0, maximum-scale=1.0, minimum-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>Document</title>
    <style>
        body, html {
            height: 100%;
            width: 100%;
            margin: 0;
        }

        * {
            box-sizing: border-box;
        }

        body {
            padding: 50px 0;
        }

        body > div {
            display: flex;
            flex-direction: column;
            max-width: 1000px;
            min-width: 800px;
            margin: 0 auto;
            border: 1px solid #f2f2f2;
            border-radius: 8px;
            height: 100%;
        }

        .message_area {
            flex: 1;
            overflow-y: auto;
        }

        .input_area {
            height: 80px;
            width: 100%;
            display: flex;
            border-top: 1px solid #f2f2f2;
        }

        .input_area > div:first-child {
            flex: 1;
        }

        .input_area > div:last-child {
            width: 100px;
        }

        .input_area textarea, .input_area button {
            width: 100%;
            height: 100%;
            border: none;
            outline: none;
        }

        .input_area textarea {
            padding: 12px;
            line-height: 1.6;
            letter-spacing: .3px;
        }

        .input_area button {
            background-color: #f9f9f9;
        }

        .input_area button:active {
            background-color: #eee;
        }

        .message_item {
            padding: 0 15px;
            margin: 12px 0;
        }

        .message_item .hd {
            font-size: 12px;
        }

        .message_item .hd .name {
            color: #555;
        }

        .message_item .hd .time {
            color: #666;
            padding-left: 15px;
        }

        .message_item .bd {
            line-height: 1.6;
            letter-spacing: .3px;
            font-size: 12px;
            padding: 8px 10px;
            margin-top: 8px;
            display: inline-block;
            border-radius: 4px;
            background-color: #fafafa;
        }

        .message_item.self {
            text-align: right;
        }

        .message_item.self .bd {
            color: #fff;
            background-color: #07c160;
        }

        .message_item.self .hd .name {
            color: #07c160;
        }

        .message_item.self .hd .time {
            display: none;
        }
    </style>
</head>
<body>
<div>
    <div class="message_area" id="message_area"></div>
    <div class="input_area">
        <div>
            <textarea id="messageInput" placeholder="输入要发送的消息"></textarea>
        </div>
        <div>
            <button id="btnSend" type="button" class="btn" onclick="send()">发送</button>
        </div>
    </div>
</div>
<script>
    const messageInput = document.querySelector('#messageInput'),
        message_area = document.querySelector('#message_area'),
        clientId = localStorage.clientId || (Date.now() + Math.random() * 1000000 ^ 0),
        name = localStorage.name || prompt('请输入一个昵称'),
        server = `ws://${location.hostname}:${location.port}${location.pathname}message/${clientId}`

    let socket = null;

    localStorage.setItem('clientId', clientId);
    localStorage.setItem('name', name);
    document.title = name;

    let shifted = false;
    document.addEventListener('keydown', e => {
        if (e.key === 'Shift') {
            shifted = true;
        }
    });
    document.addEventListener('keyup', e => {
        if (e.key === 'Shift') {
            shifted = true;
        }
    });
    messageInput.addEventListener('keypress', e => {
        if (!shifted && e.key === 'Enter') return requestAnimationFrame(send);
    })

    function createSocket() {
        socket = new WebSocket(server);
        socket.onclose = socket.onerror = e => {
            socket = null;
        };
        socket.onmessage = e => {
            const data = JSON.parse(e.data);
            appendMessage(data);
        };
    }

    createSocket();

    function send() {
        if (!socket) {
            createSocket();
        }

        const value = messageInput.value.trim();
        messageInput.value = '';
        if(!value) return;
        const data = {
            text: value,
            from: {
                clientId: clientId,
                name: name
            },
            time: ''
        };
        socket.send(JSON.stringify(data));
        appendMessage(data, true);
    }

    function appendMessage(data, isSelf) {
        const elem = document.createElement('div');
        elem.innerHTML = `
            <div class="hd"><span class="name">${data.from.name}</span><span class="time">${data.time}</span></div>
            <div class="bd">${data.text.replace(/\n/g, '<br>')}</div>
        `;
        elem.classList.add('message_item');
        if (isSelf) {
            elem.classList.add('self');
        }
        message_area.appendChild(elem)
        elem.scrollIntoView()
    }
</script>
</body>
</html>

要点：

  • 支持按住shift + enter键换行
  • 支持按enter快速发送消息
  • 客户端标识和昵称都存在了localStorage里面