HackMD[JAVA] Spring boot + WebSocket STOMP 批次介接比特幣價格API推播到前端畫面
tags: Java Spring Boot WebSocket
[實作目的] Server端介接Cryptowatch API，定時批次取得比特幣即時價格，並推播到前端畫面。
程式碼傳送門：GitHub
啟動程式後，瀏覽器連上localhost:8080即可
功能展示
因為Cryptowatch API沒有付費的話，會有介接的使用次數限制。因此也將該資訊於前端展示，並且將批次設定為5秒執行一次以減少quota的使用。
幾秒後…的畫面
前端程式碼
-
pom.xml
這邊主要使用到的依賴有：
- Spring Boot
- webSocket
- webjars (用於打包前端靜態資源成jar檔)
- httpClient
<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<groupId>com.abby.websocket</groupId>
<artifactId>BTC-price-websocket-demo</artifactId>
<version>0.0.1-SNAPSHOT</version>
<packaging>jar</packaging>
<name>BTC-price-websocket-demo</name>
<description>Demo project for WebSocket</description>
<!-- 新版Spring Boot會和webjars不相容，暫不處理引用舊版-->
<parent>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-parent</artifactId>
<version>2.1.0.BUILD-SNAPSHOT</version>
<relativePath/> <!-- lookup parent from repository -->
</parent>
<properties>
<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
<project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
<java.version>11</java.version>
</properties>
<dependencies>
<!-- websocket -->
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-websocket</artifactId>
</dependency>
<!--將web前端資源（如jQuery & Bootstrap）打成jar包文件-->
<dependency>
<groupId>org.webjars</groupId>
<artifactId>webjars-locator</artifactId>
<version>0.32-1</version>
</dependency>
<dependency>
<groupId>org.webjars</groupId>
<artifactId>sockjs-client</artifactId>
<version>1.0.2</version>
</dependency>
<dependency>
<groupId>org.webjars</groupId>
<artifactId>stomp-websocket</artifactId>
<version>2.3.3</version>
</dependency>
<dependency>
<groupId>org.webjars</groupId>
<artifactId>bootstrap</artifactId>
<version>3.3.7</version>
</dependency>
<dependency>
<groupId>org.webjars</groupId>
<artifactId>jquery</artifactId>
<version>3.1.0</version>
</dependency>
<!-- lombok -->
<dependency>
<groupId>org.projectlombok</groupId>
<artifactId>lombok</artifactId>
</dependency>
<!-- httpClient -->
<dependency>
<groupId>org.apache.httpcomponents</groupId>
<artifactId>httpclient</artifactId>
</dependency>
<dependency>
<groupId>org.apache.httpcomponents</groupId>
<artifactId>httpcore</artifactId>
</dependency>
<dependency>
<groupId>commons-lang</groupId>
<artifactId>commons-lang</artifactId>
<version>2.6</version>
</dependency>
<dependency>
<groupId>com.squareup.okhttp3</groupId>
<artifactId>okhttp</artifactId>
<version>3.8.1</version>
</dependency>
</dependencies>
<build>
<plugins>
<plugin>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-maven-plugin</artifactId>
</plugin>
</plugins>
</build>
</project>
-
WebSocketConfig.java
後端WebSocket功能相關的部分。
@EnableWebSocketMessageBroker 用於開啟使用STOMP協議來傳輸基於代理（MessageBroker）的消息，這時候controller開始支援websocket的@MessageMapping，就像是使用RESTful的@requestMapping那樣。
至於HttpHandShakeInterceptor、SocketChannelInterceptor在這次的範例中不是重點這邊不贅述
，gitHub上的原始碼我有寫了相關註解，有需要再看看就好。
@Configuration
@EnableWebSocketMessageBroker
public class WebSocketConfig implements WebSocketMessageBrokerConfigurer {
/**
* 註冊client端連進Server端之路徑
* 並使用攔截器設定可以連進來的來源位置(這邊範例使用 "*" 意思是都不擋)
*/
@Override
public void registerStompEndpoints(StompEndpointRegistry registry) {
registry.addEndpoint("/endpoint-websocket").addInterceptors(new HttpHandShakeInterceptor()).setAllowedOrigins("*").withSockJS();
}
/**
* 配置訊息代理
* enableSimpleBroker： server端推送給client端的路徑prefix
* setApplicationDestinationPrefixes： client端發送給server端的路徑prefix
*/
@Override
public void configureMessageBroker(MessageBrokerRegistry registry) {
registry.enableSimpleBroker("/topic");
registry.setApplicationDestinationPrefixes("/app");
}
/**
* 註冊由client端傳到server端的攔截器
*/
@Override
public void configureClientInboundChannel(ChannelRegistration registration) {
registration.interceptors(new SocketChannelInterceptor());
}
/**
* 註冊由server端傳到client端的攔截器
*/
@Override
public void configureClientOutboundChannel(ChannelRegistration registration) {
registration.interceptors(new SocketChannelInterceptor());
}
}
-
CoinResult.java
CoinResult是用於將API回傳json字串，轉換為Java物件的承接DTO
這邊介接的API為Cryotiwatcgh網站提供的幣安交易所BTC/USDT即時價格：https://api.cryptowat.ch/markets/binance/btcusdt/price
該API回傳的資料格式如下：
@Data是依賴套件Lombok內的annotation，使用之後等於自動寫了constroctor、getter、setter、並覆寫toString、equals、hashCode，可以快速地幫我們建立好entity。
【Lombok詳細介紹推薦這篇文章】：Java - 五分鐘學會 Lombok 用法
@JsonIgnoreProperties(ignoreUnknown = true)
@Data
public class CoinResult {
/**
* 用於轉換API回傳json字串為Java物件的實體
*/
@JsonProperty("result")
private Result result;
@JsonProperty("allowance")
private Allowance allowance;
@Data
@JsonIgnoreProperties(ignoreUnknown = true)
public static class Result {
/**
* 價格
*/
@JsonProperty("price")
private String price;
}
@Data
@JsonIgnoreProperties(ignoreUnknown = true)
public static class Allowance {
/**
* 本次查詢扣點
*/
@JsonProperty("cost")
private String cost;
/**
* 剩餘扣點餘額
*/
@JsonProperty("remaining")
private String remaining;
/**
* API提供網站的無上限查詢限制升級提示訊息
*/
@JsonProperty("upgrade")
private String upgrade;
}
}
-
OutMessage.java
OutMessage是server端向client端發送的物件，這裡會將從API裡拿到的CoinResult資訊，在service層處理為顯示給前端畫面使用者看文字內容、發送來源、時間。
@Data
@AllArgsConstructor
@NoArgsConstructor
public class OutMessage {
private String from;
private String content;
private Date time = new Date();
public OutMessage(String content) {
this.content = content;
}
}
-
CoinService.java
CoinService實作了打到Cryptowath的API去獲取目前BTC/USDT的價格資料，並轉為CoinResult物件。
@Slf4j
public class CoinService {
public static CoinResult getStockInfo() {
String host = "https://api.cryptowat.ch";
String path = "/markets/binance/btcusdt/price";
String method = "GET";
Map<String, String> headers = new HashMap<String, String>();
Map<String, String> querys = new HashMap<String, String>();
try {
//GET方式打過去
HttpResponse response = HttpUtils.doGet(host, path, method, headers, querys);
//將response的body轉為字串
String responseText = EntityUtils.toString(response.getEntity());
//將json格式的字串轉成Java的物件
CoinResult coinResult = JsonUtils.objectFromJson(responseText, CoinResult.class);
log.info("console印出API回傳資訊=======================================");
System.out.println(coinResult.toString());
return coinResult;
} catch (Exception e) {
e.printStackTrace();
}
return null;
}
}
-
CoinSchedule.java
Spring內建的批次作業功能，使用@Scheduled註解並設定時間即會定時執行該方法。
記得要在啟動類別加上@EnableScheduling才會生效。
@Component
public class CoinSchedule {
@Autowired
private WebSocketService ws;
/**
* 每5秒一次，推送給client端
*/
@Scheduled(cron = "*/5 * * * * ?")
public void coinInfo() {
ws.sendCoinInfo();
}
}
前端程式碼：
-
index.html
前端畫面。
<!DOCTYPE html>
<html>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />
<head>
<title>Hello WebSocket</title>
<link href="/webjars/bootstrap/css/bootstrap.min.css" rel="stylesheet">
<link href="/main.css" rel="stylesheet">
<script src="/webjars/jquery/jquery.min.js"></script>
<script src="/webjars/sockjs-client/sockjs.min.js"></script>
<script src="/webjars/stomp-websocket/stomp.min.js"></script>
<script src="/app.js"></script>
</head>
<body>
<noscript><h2 style="color: #ff0000">Seems your browser doesn't support Javascript! Websocket relies on Javascript being
enabled. Please enable
Javascript and reload this page!</h2></noscript>
<div id="main-content" class="container">
<div class="row">
<div class="col-md-6">
<form class="form-inline">
<div class="form-group">
<label for="connect">向Server端建立WebSocket連結</label>
<button id="connect" class="btn btn-default" type="submit">Connect</button>
<button id="disconnect" class="btn btn-default" type="submit" disabled="disabled">Disconnect
</button>
</div>
</form>
</div>
</div>
<div class="row">
<div class="col-md-12">
<table id="conversation" class="table table-striped">
<thead>
<tr>
<th>價格資訊</th>
</tr>
</thead>
<tbody id="notice">
</tbody>
</table>
</div>
</div>
</div>
</body>
</html>
-
app.js
前端的js。
connect()中的var socket = new SockJS('/endpoint-websocket');就是對應到在server端WebSocketConfig.java內registerStompEndpoints註冊的路徑。
第21~23行就是指該client端要訂閱來自server端發送的哪些內容 (本範例的server端只有發送一個coin_info主題，但實際上可以有很多個)，對應到後端WebSocketService的template.convertAndSend("/topic/coin_info",new OutMessage(msg));這行。
var stompClient = null;
function setConnected(connected) {
$("#connect").prop("disabled", connected);
$("#disconnect").prop("disabled", !connected);
if (connected) {
$("#conversation").show();
}
else {
$("#conversation").hide();
}
$("#notice").html("");
}
function connect() {
var socket = new SockJS('/endpoint-websocket');
stompClient = Stomp.over(socket);
stompClient.connect({}, function (frame) {
setConnected(true);
console.log('Connected: ' + frame);
stompClient.subscribe('/topic/coin_info', function (result) {
showContent(JSON.parse(result.body));
});
});
}
function disconnect() {
if (stompClient !== null) {
stompClient.disconnect();
}
setConnected(false);
console.log("Disconnected");
}
function showContent(body) {
$("#notice").html("<tr><td>" + body.content + "</td> <td>"+new Date(body.time).toLocaleString()+"</td></tr>");
}
$(function () {
$("form").on('submit', function (e) {
e.preventDefault();
});
$( "#connect" ).click(function() { connect(); });
$( "#disconnect" ).click(function() { disconnect(); });
});
以上就是這個Demo的解說。
程式碼傳送門：GitHub
