基于okhttp和RxJava封装的自动重连的WebSocket

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一. 概述

RxWebSocket是一个基于okhttp和RxJava封装的WebSocket客户端,此库的核心特点是 除了手动关闭WebSocket(就是RxJava取消订阅),WebSocket在异常关闭的时候(onFailure,发生异常,如WebSocketException等等),会自动重连,永不断连.其次,对WebSocket做的缓存处理,同一个URL,共享一个WebSocket.

由于是基于RxJava封装,所以带来了无限可能,可以和RxBinding,Rxlifecycle一起使用,方便对WebSocket的管理.

效果图

项目已经上传Jcenter,依赖方法:

//本项目 
compile 'io.github.dzsf:RxWebSocket:1.0.0' 

二. 使用方法

0.初始化,可以也忽略直接使用.

如果你想使用自己的okhttpClient:

OkHttpClient yourClient = new OkHttpClient(); 
RxWebSocketUtil.getInstance().setClient(yourClient); 

 是否打印日志:

RxWebSocketUtil.getInstance().setShowLog(BuildConfig.DEBUG); 

1.获取一个WebSocket,接收消息,多种方式:

RxWebSocketUtil.getInstance().getWebSocketInfo(url) 
        .subscribe(new Action1<WebSocketInfo>() { 
            @Override 
            public void call(WebSocketInfo webSocketInfo) { 
                mWebSocket = webSocketInfo.getWebSocket(); 
                Log.d("MainActivity", webSocketInfo.getString()); 
                Log.d("MainActivity", "ByteString:" + webSocketInfo.getByteString()); 
            } 
        }); 
 
mWebSocket.send("hello word"); 
 
//get StringMsg 
RxWebSocketUtil.getInstance().getWebSocketString(url) 
        .subscribe(new Action1<String>() { 
            @Override 
            public void call(String s) { 
            } 
        }); 
// get ByteString 
RxWebSocketUtil.getInstance().getWebSocketByteString(url) 
        .subscribe(new Action1<ByteString>() { 
            @Override 
            public void call(ByteString byteString) { 
            } 
        }); 
//get WebSocket 
RxWebSocketUtil.getInstance().getWebSocket(url) 
        .subscribe(new Action1<WebSocket>() { 
            @Override 
            public void call(WebSocket webSocket) { 
            } 
        }); 
// 带timeout的WebSocket,当在指定时间内没有收到消息,就重连WebSocket.为了适配小米平板. 
RxWebSocketUtil.getInstance().getWebSocketInfo(url,10, TimeUnit.SECONDS) 
        .subscribe(new Action1<WebSocketInfo>() { 
            @Override 
            public void call(WebSocketInfo webSocketInfo) { 
            } 
        }); 

2.发送消息:

//用WebSocket的引用直接发 
mWebSocket.send("hello word"); 
 
//url 对应的WebSocket 必须打开,否则报错 
RxWebSocket.send(sendUrl, "hello"); 
RxWebSocket.send(sendUrl, ByteString.EMPTY); 
 
//异步发送,若WebSocket已经打开,直接发送,若没有打开,打开一个WebSocket发送完数据,直接关闭. 
RxWebSocket.asyncSend(sendUrl, "hello"); 
RxWebSocket.asyncSend(sendUrl, ByteString.EMPTY); 

3.关闭WebSocket:

项目是依托RxJava实现的,所以关闭WebSocket的方法也就是在适当的时候注销 Observable,项目里的demo里,写了一个简单的lifecycle,将Observable生命绑定到Activity的onDestroy,自动注销.代码细节请看demo,因为内部实现了同一个URL的WebSocket共享机制,所以当外部所有持有这个URL的Observable都注销后,这个WebSocket连接就会自动关闭.请看原理解析部分

//注意取消订阅,有多种方式,比如 rxlifecycle 
mSubscription = RxWebSocketUtil.getInstance().getWebSocketInfo(url) 
        .subscribe(new Action1<WebSocketInfo>() { 
            @Override 
            public void call(WebSocketInfo webSocketInfo) { 
                mWebSocket = webSocketInfo.getWebSocket(); 
 
                if (webSocketInfo.isOnOpen()) { 
                    Log.d("MainActivity", " on WebSocket open"); 
                } else { 
                    String string = webSocketInfo.getString(); 
 
                    if (string != null) { 
                        Log.d("MainActivity", string); 
                        textview.setText(Html.fromHtml(string)); 
                    } 
 
                    ByteString byteString = webSocketInfo.getByteString(); 
 
                    if (byteString != null) { 
                        Log.d("MainActivity", 
                            "webSocketInfo.getByteString():" + 
                            byteString); 
                    } 
                } 
            } 
        }); 
 
//注销 
if (mSubscription != null) { 
    mSubscription.unsubscribe(); 
} 
 
//lifecycle注销,详情看demo 
RxWebSocketUtil.getInstance().getWebSocketString(url) 
            .compose(this.<String>bindOnActivityEvent(ActivityEvent.onDestory)) 
            .subscribe(new Action1<String>() { 
                @Override 
                public void call(String s) { 
                } 
            }); 

三. 原理解析

1. 首先需要将okhttp的WebSocket包装成Observable,由于需要将WebSocket,Stringmsg,ByteString等信息一同发送给观察者所以先构建一个WebSocketInfo类,将信息封装:

public class WebSocketInfo { 
    private WebSocket mWebSocket; 
    private String mString; 
    private ByteString mByteString; 
    private boolean onOpen; 
    //其他省略 
} 

onOpen字段主要用来判断当前的这个WebSocketInfo是否是当WebSocket打开时发送的消息(onOpen),这时,Stringmsg和ByteString都是null.

2. 将WebSocketInfo包装成Observable发出:

private final class WebSocketOnSubscribe implements Observable.OnSubscribe<WebSocketInfo> { 
    private String url; 
    private WebSocket webSocket; 
    private WebSocketInfo startInfo; 
    private WebSocketInfo stringInfo; 
    private WebSocketInfo byteStringInfo; 
 
    public WebSocketOnSubscribe(String url) { 
        this.url = url; 
        startInfo = new WebSocketInfo(true); 
        stringInfo = new WebSocketInfo(); 
        byteStringInfo = new WebSocketInfo(); 
    } 
 
    @Override 
    public void call(final Subscriber<?super WebSocketInfo> subscriber) { 
        if (webSocket != null) { 
            //降低重连频率 
            if (!"main".equals(Thread.currentThread().getName())) { 
                SystemClock.sleep(2000); 
            } 
        } 
 
        initWebSocket(subscriber); 
    } 
 
    private void initWebSocket( 
        final Subscriber<?super WebSocketInfo> subscriber) { 
        webSocket = client.newWebSocket(getRequest(url), 
                new WebSocketListener() { 
                    @Override 
                    public void onOpen(final WebSocket webSocket, 
                        Response response) { 
                        if (showLog) { 
                            Log.d("RxWebSocketUtil", url + " --> onOpen"); 
                        } 
 
                        webSocketMap.put(url, webSocket); 
                        AndroidSchedulers.mainThread().createWorker().schedule(new Action0() { 
                                @Override 
                                public void call() { 
                                    if (!subscriber.isUnsubscribed()) { 
                                        subscriber.onStart(); 
                                        startInfo.setWebSocket(webSocket); 
                                        subscriber.onNext(startInfo); 
                                    } 
                                } 
                            }); 
                    } 
 
                    @Override 
                    public void onMessage(WebSocket webSocket, String text) { 
                        if (!subscriber.isUnsubscribed()) { 
                            stringInfo.setWebSocket(webSocket); 
                            stringInfo.setString(text); 
                            subscriber.onNext(stringInfo); 
                        } 
                    } 
 
                    @Override 
                    public void onMessage(WebSocket webSocket, ByteString bytes) { 
                        if (!subscriber.isUnsubscribed()) { 
                            byteStringInfo.setWebSocket(webSocket); 
                            byteStringInfo.setByteString(bytes); 
                            subscriber.onNext(byteStringInfo); 
                        } 
                    } 
 
                    @Override 
                    public void onFailure(WebSocket webSocket, Throwable t, 
                        Response response) { 
                        if (showLog) { 
                            Log.e("RxWebSocketUtil", 
                                t.toString() + 
                                webSocket.request().url().uri().getPath()); 
                        } 
 
                        if (!subscriber.isUnsubscribed()) { 
                            subscriber.onError(t); 
                        } 
                    } 
 
                    @Override 
                    public void onClosing(WebSocket webSocket, int code, 
                        String reason) { 
                        webSocket.close(1000, null); 
                    } 
 
                    @Override 
                    public void onClosed(WebSocket webSocket, int code, 
                        String reason) { 
                        if (showLog) { 
                            Log.d("RxWebSocketUtil", 
                                url + " --> onClosed:code= " + code); 
                        } 
                    } 
                }); 
        subscriber.add(new MainThreadSubscription() { 
                @Override 
                protected void onUnsubscribe() { 
                    webSocket.close(3000, "手动关闭"); 
                } 
            }); 
    } 
} 

实现一个WebSocketOnSubscribe 将WebSocket的回调转化成subscriber调用.发送给Observable下游.在onOpen时调用 subscriber.onStart(),并且发送一个onOpen的WebSocketInfo.在subscriber注销的时候关闭WebSocket.在call方法最上面有个SystemClock.sleep(2000),这个主要是为了降低在断连的时候的重连频率,将在下面讲到.

包装成Observable:

Observable.create(new WebSocketOnSubscribe(url)) 
            .subscribeOn(Schedulers.io()) 
            .observeOn(AndroidSchedulers.mainThread()); 

3. 实现自动重连:

Observable.create(new WebSocketOnSubscribe(url)) 
            //自动重连 
            .timeout(timeout, timeUnit).retry() 
            .subscribeOn(Schedulers.io()) 
            .observeOn(AndroidSchedulers.mainThread()); 

RxJava retry操作符,很完美的实现了这个功能,当上游发出Throwable的时候,retry将错误吃掉,并重新调用 onSubscribe的call方法,也就是WebSocketOnSubscribe的call,就会重新初始化一个WebSocket连接,达到重连的目的,如果一直没有网络,这个retry的调用频率非常高,所以在call方法里面,当是重连的时候,就SystemClock.sleep(2000),休眠2秒,这样重连的频率就是2秒重连一次. 当然在retry上面还有一个timeout操作符.当subscriber.onNext()在指定时间间隔里没有调用,就发出一个timeoutException,让retry重连WebSocket.这个主要是为了适配部分国产机型,当WebSocket发生连接异常时,不会及时发出错误,如小米平板.在每次重连都会把原来的WebSocket关闭.

4. 实现同一个URL的WebSocket共享

Observable.create(new WebSocketOnSubscribe(url)) 
        //自动重连 
        .timeout(timeout, timeUnit) 
        .retry() 
        //共享 
        .doOnUnsubscribe(new Action0() { 
            @Override 
            public void call() { 
                observableMap.remove(url); 
                webSocketMap.remove(url); 
 
                if (showLog) { 
                    Log.d("RxWebSocketUtil", "注销"); 
                } 
            } 
        }) 
        .doOnNext(new Action1<WebSocketInfo>() { 
            @Override 
            public void call(WebSocketInfo webSocketInfo) { 
                if (webSocketInfo.isOnOpen()) { 
                    webSocketMap.put(url, webSocketInfo.getWebSocket()); 
                } 
            } 
        }) 
        .share() 
        .subscribeOn(Schedulers.io()) 
        .observeOn(AndroidSchedulers.mainThread()); 

实现共享功能,主要是为了防止一个URL的WebSocket,建立多个连接,这个主要是由RxJava的share操作符实现,share操作符,使得一个Observable可以有多个subscriber,当有多个subscriber时,当所有的subscriber都取消订阅,这个Observable才会取消订阅.

getWebSocketInfo()方法完整代码:

public Observable<WebSocketInfo> getWebSocketInfo(final String url, final long timeout, final TimeUnit timeUnit) { 
    Observable<WebSocketInfo> observable = observableMap.get(url); 
    if (observable == null) { 
        observable = Observable.create(new WebSocketOnSubscribe(url)) 
                //自动重连 
                .timeout(timeout, timeUnit) 
                .retry() 
                //共享 
                .doOnUnsubscribe(new Action0() { 
                    @Override 
                    public void call() { 
                        observableMap.remove(url); 
                        webSocketMap.remove(url); 
                        if (showLog) { 
                            Log.d("RxWebSocketUtil", "注销"); 
                        } 
                    } 
                }) 
                .doOnNext(new Action1<WebSocketInfo>() { 
                    @Override 
                    public void call(WebSocketInfo webSocketInfo) { 
                        if (webSocketInfo.isOnOpen()) { 
                            webSocketMap.put(url, webSocketInfo.getWebSocket()); 
                        } 
                    } 
                }) 
                .share() 
                .subscribeOn(Schedulers.io()) 
                .observeOn(AndroidSchedulers.mainThread()); 
        observableMap.put(url, observable); 
    } else { 
        observable = Observable.merge(Observable.just(new WebSocketInfo(webSocketMap.get(url), true)), observable); 
    } 
    return observable; 
} 

doOnUnsubscribe作用:在Observable注销,即 WebSocket关闭时,移除map中的缓存的Observable和WebSocket.

doOnNext作用: 判断接收到的WebSocketInfo是否是WebSocket在onOpen的时候发的,然后将其缓存起来.作用就是:如果有一个相同的URL订阅Observable,就从缓存中取,这个时候我们应该把一个WebSocket的onOpen事件也发给这个订阅者:

//使用merge操作符,将onOpen事件发给订阅者 
observable = Observable.merge(Observable.just(new WebSocketInfo(webSocketMap.get(url), true)), observable); 

这样的话,同一个URL的WebSocket,不管在什么地方什么时间订阅,都能收到一个onOpen事件,外部表现的就像一个新的WebSocket.

getWebSocketInfo方法的几种变体:

/** 
 * default timeout: 30 days 
 * <p> 
 * 若忽略小米平板,请调用这个方法 
 * </p> 
 */ 
public Observable<WebSocketInfo> getWebSocketInfo(String url) { 
    return getWebSocketInfo(url, 30, TimeUnit.DAYS); 
} 
 
public Observable<String> getWebSocketString(String url) { 
    return getWebSocketInfo(url) 
            .map(new Func1<WebSocketInfo, String>() { 
                @Override 
                public String call(WebSocketInfo webSocketInfo) { 
                    return webSocketInfo.getString(); 
                } 
            }) 
            .filter(new Func1<String, Boolean>() { 
                @Override 
                public Boolean call(String s) { 
                    return s != null; 
                } 
            }); 
} 
 
public Observable<ByteString> getWebSocketByteString(String url) { 
    return getWebSocketInfo(url) 
            .map(new Func1<WebSocketInfo, ByteString>() { 
                @Override 
                public ByteString call(WebSocketInfo webSocketInfo) { 
                    return webSocketInfo.getByteString(); 
                } 
            }) 
            .filter(new Func1<ByteString, Boolean>() { 
                @Override 
                public Boolean call(ByteString byteString) { 
                    return byteString != null; 
                } 
            }); 
} 
 
public Observable<WebSocket> getWebSocket(String url) { 
    return getWebSocketInfo(url) 
            .map(new Func1<WebSocketInfo, WebSocket>() { 
                @Override 
                public WebSocket call(WebSocketInfo webSocketInfo) { 
                    return webSocketInfo.getWebSocket(); 
                } 
            }); 
} 

5 . send信息到服务端

上面已经讲到WebSocketInfo包含了WebSocket,所以在订阅后,就可以拿到这个WebSocket引用就可以WebSocket.send发送消息到服务端.当然我们的RxWebSocketUtil已经将开启的WebSocket已经缓存.所以我们也可以这样发消息:

/** 
 * 如果url的WebSocket已经打开,可以直接调用这个发送消息. 
 * 
 * @param url 
 * @param msg 
 */ 
public void send(String url, String msg) { 
    WebSocket webSocket = webSocketMap.get(url); 
    if (webSocket != null) { 
        webSocket.send(msg); 
    } else { 
        throw new IllegalStateException("The WebSokcet not open"); 
    } 
} 
 
/** 
 * 如果url的WebSocket已经打开,可以直接调用这个发送消息. 
 * 
 * @param url 
 * @param byteString 
 */ 
public void send(String url, ByteString byteString) { 
    WebSocket webSocket = webSocketMap.get(url); 
    if (webSocket != null) { 
        webSocket.send(byteString); 
    } else { 
        throw new IllegalStateException("The WebSokcet not open"); 
    } 
} 

当指定的URL的WebSocket没有打开会直接报错.

异步发送消息到服务端

/** 
 * 不用关心url 的WebSocket是否打开,可以直接发送 
 * 
 * @param url 
 * @param msg 
 */ 
public void asyncSend(String url, final String msg) { 
    getWebSocket(url) 
            .first() 
            .subscribe(new Action1<WebSocket>() { 
                @Override 
                public void call(WebSocket webSocket) { 
                    webSocket.send(msg); 
                } 
            }); 
 
} 
 
/** 
 * 不用关心url 的WebSocket是否打开,可以直接发送 
 * 
 * @param url 
 * @param byteString 
 */ 
public void asyncSend(String url, final ByteString byteString) { 
    getWebSocket(url) 
            .first() 
            .subscribe(new Action1<WebSocket>() { 
                @Override 
                public void call(WebSocket webSocket) { 
                    webSocket.send(byteString); 
                } 
            }); 
} 

这两种发送方式,你不用关心URL的WebSocket是否打开,可以直接发送.实现思路也很简单,getWebSocket(url)会获取到Observable,或者是从缓存中取,或者是重新开启一个WebSocket,但你都不需要关心,经过first操作符后,如果是从缓存取的Observable,就注销的当前的Observable,当是新开的WebSocket,注销掉当前的subscriber后,就没有其他subscriber了,这个新开的WebSocket就会关闭(share操作符作用).

想了解更多内容，请访问：

51CTO和华为官方合作共建的鸿蒙技术社区

https://harmonyos.51cto.com