了解proto3后,接下来看官方Demo作为训练,这里建议看一遍之后自己动手搭建出来,一方面巩固之前的知识,一方面是对整个流程更加熟悉.

官方Demo地址: https://github.com/grpc/grpc-java
例子是一个简单的路由映射的应用，它允许客户端获取路由特性的信息，生成路由的总结，以及交互路由信息，如服务器和其他客户端的流量更新.

1.1定义服务

也就是写proto文件

//指定proto3格式
syntax = "proto3";
//一些生成代码的设置
option java_multiple_files = true;//以外部类模式生成
option java_package = "cn.mrdear.route";//所在包名
option java_outer_classname = "RouteProto";//最外层类名称//定义服务
service RouteGuide{//得到指定点的feature//一个 简单 RPC ， 客户端使用存根发送请求到服务器并等待响应返回，就像平常的函数调用一样。rpc GetFeature(Point) returns (Feature) {}//获取一个矩形内的点//一个 服务器端流式 RPC ， 客户端发送请求到服务器，拿到一个流去读取返回的消息序列。 客户端读取返回的流，//直到里面没有任何消息。从例子中可以看出，通过在 响应 类型前插入 stream 关键字，可以指定一个服务器端的流方法。rpc ListFeatures(Rectangle) returns (stream Feature){}//记录该点//一个 客户端流式 RPC ， 客户端写入一个消息序列并将其发送到服务器，同样也是使用流。一旦客户端完成写入消息，//它等待服务器完成读取返回它的响应。通过在 请求 类型前指定 stream 关键字来指定一个客户端的流方法。rpc RecordRoute(stream Point) returns (RouteSummary){}//路由交流//一个 双向流式 RPC 是双方使用读写流去发送一个消息序列。两个流独立操作，因此客户端和服务器//可以以任意喜欢的顺序读写：比如， 服务器可以在写入响应前等待接收所有的客户端消息，或者可以交替 的读取和写入消息，//或者其他读写的组合。每个流中的消息顺序被预留。你可以通过在请求和响应前加 stream 关键字去制定方法的类型。rpc RouteChat(stream RouteNote) returns (stream RouteNote){}
}//代表经纬度
message Point {int32 latitude = 1;int32 longitude = 2;
}
//由两个点确定的一个方块
message Rectangle{Point lo = 1;Point hi = 2;
}
//某一位置的名称
message Feature {string name = 1;Point location = 2;
}// Not used in the RPC.  Instead, this is here for the form serialized to disk.
message FeatureDatabase {repeated Feature feature = 1;
}
//给某一点发送消息
message RouteNote{Point location = 1;string message = 2;
}//记录收到的信息
message RouteSummary{int32 point_count = 1;int32 feture_count = 2;int32 distance = 3;int32 elapsed_time = 4;
}

执行mvn compile生成如下代码:

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1.2编写RouteGuideService

该类就是这个项目所提供给外部的功能.该类需要继承RouteGuideGrpc.RouteGuideImplBase,这个类提供了我们所定义分服务接口,继承后覆盖需要实现的自定义方法.

简单 RPC
简单RPC和普通方法调用形式差不多,客户端传来一个实体,服务端返回一个实体.

    @Overridepublic void getFeature(Point request, StreamObserver<Feature> responseObserver) {System.out.println("getFeature得到的请求参数: " + request.toString());
//        responseObserver.onError(); 代表请求出错responseObserver.onNext(checkFeature(request));//包装返回信息responseObserver.onCompleted();//结束一次请求}//找到复核的featureprivate Feature checkFeature(Point location) {for (Feature feature : features) {if (feature.getLocation().getLatitude() == location.getLatitude()&& feature.getLocation().getLongitude() == location.getLongitude()) {return feature;}}// No feature was found, return an unnamed feature.return Feature.newBuilder().setName("").setLocation(location).build();}

其中StreamObserver<Feature>是一个应答观察者,用于封装返回的信息,服务器把该信息传给客户端.请求结束要调用onCompleted()方法.

服务器端流式 RPC
在proto文件中声明了stream,但是从接口上看不出来和简单RPC的区别,代码中最主要的区别是多次调用responseObserver.onNext()的方法,最后完成时写回数据.

    @Overridepublic void listFeatures(Rectangle request, StreamObserver<Feature> responseObserver) {int left = min(request.getLo().getLongitude(), request.getHi().getLongitude());int right = max(request.getLo().getLongitude(), request.getHi().getLongitude());int top = max(request.getLo().getLatitude(), request.getHi().getLatitude());int bottom = min(request.getLo().getLatitude(), request.getHi().getLatitude());for (Feature feature : features) {//如果不存在则继续if (!RouteGuideUtil.exists(feature)) {continue;}int lat = feature.getLocation().getLatitude();int lon = feature.getLocation().getLongitude();if (lon >= left && lon <= right && lat >= bottom && lat <= top) {//找到符合的就写入responseObserver.onNext(feature);}}//最后标识完成responseObserver.onCompleted();}

客户端流式 RPC
服务端就需要一直监控客户端写入情况,因此需要一个StreamObserver接口,其中onNext方法会在客户端每次写入时调用,当写入完毕时调用onCompleted()方法.具体还要到后面客户端调用分析.

@Overridepublic StreamObserver<Point> recordRoute(StreamObserver<RouteSummary> responseObserver) {return new StreamObserver<Point>() {int pointCount;int featureCount;int distance;Point previous;long startTime = System.nanoTime();//客户端每写入一个Point,服务端就会调用该方法@Overridepublic void onNext(Point point) {System.out.println("recordRoute得到的请求参数: " + point.toString());pointCount++;if (RouteGuideUtil.exists(checkFeature(point))) {featureCount++;}if (previous != null) {distance += calcDistance(previous, point);}previous = point;}@Overridepublic void onError(Throwable throwable) {throwable.printStackTrace();System.err.println("Encountered error in recordRoute");}//客户端写入结束时调用@Overridepublic void onCompleted() {long seconds = NANOSECONDS.toSeconds(System.nanoTime() - startTime);responseObserver.onNext(RouteSummary.newBuilder().setPointCount(pointCount).setFetureCount(featureCount).setDistance(distance).setElapsedTime((int) seconds).build());responseObserver.onCompleted();}};}

双向流式 RPC
和客户端流式RPC差不多.

    @Overridepublic StreamObserver<RouteNote> routeChat(StreamObserver<RouteNote> responseObserver) {return new StreamObserver<RouteNote>() {@Overridepublic void onNext(RouteNote note) {List<RouteNote> notes = getOrCreateNotes(note.getLocation());for (RouteNote prevNote : notes.toArray(new RouteNote[0])) {responseObserver.onNext(prevNote);}notes.add(note);}@Overridepublic void onError(Throwable t) {t.printStackTrace();System.err.println("Encountered error in routeChat");}@Overridepublic void onCompleted() {responseObserver.onCompleted();}};}

1.3创建服务端

和Helloworld一样的形式,最主要的是addService(new RouteGuideService(features)),这里把需要注册的服务给注册上.

public class RouteGuideServer {private final int port;//服务端端口private final Server server;//服务器public RouteGuideServer(int port) throws IOException {this.port = port;//获取初始化数据List<Feature> features = RouteGuideUtil.parseFeatures(RouteGuideUtil.getDefaultFeaturesFile());//初始化Server参数server = ServerBuilder.forPort(port)//添加指定服务.addService(new RouteGuideService(features)).build();}/*** 启动服务*/public void start() throws IOException {server.start();System.out.println("Server started, listening on " + port);//程序退出时关闭资源Runtime.getRuntime().addShutdownHook(new Thread(() -> {System.err.println("*** shutting down gRPC server since JVM is shutting down");RouteGuideServer.this.stop();System.err.println("*** server shut down");}));}/*** 关闭服务*/public void stop() {if (server != null) {server.shutdown();}}/*** 使得server一直处于运行状态*/private void blockUntilShutdown() throws InterruptedException {if (server != null) {server.awaitTermination();}}public static void main(String[] args) throws IOException, InterruptedException {RouteGuideServer server = new RouteGuideServer(50051);server.start();server.blockUntilShutdown();}}

1.4编写客户端

客户端需要一个channel和一个存根blockingStub或者asyncStub根据业务需要选择同步或者异步.

    private final ManagedChannel channel;//grpc信道,需要指定端口和地址private final RouteGuideGrpc.RouteGuideBlockingStub blockingStub;//阻塞/同步存根private final RouteGuideGrpc.RouteGuideStub asyncStub;//非阻塞,异步存根public RouteGuideClient(String host,int port) {//创建信道channel = ManagedChannelBuilder.forAddress(host, port).usePlaintext(true).build();//创建存根blockingStub = RouteGuideGrpc.newBlockingStub(channel);asyncStub = RouteGuideGrpc.newStub(channel);}/*** 关闭方法*/public void shutdown() throws InterruptedException {channel.shutdown().awaitTermination(5, TimeUnit.SECONDS);}

简单grpc
和调用普通方法形式差不多.

public void getFeature(int lat,int lon){System.out.println("start getFeature");Point request = Point.newBuilder().setLatitude(lat).setLongitude(lon).build();Feature feature;try {//同步阻塞调用feature = blockingStub.getFeature(request);System.out.println("getFeature服务端返回 :" + feature);} catch (StatusRuntimeException e) {System.out.println("RPC failed " +e.getStatus());}}

调用代码:

 public static void main(String[] args) throws InterruptedException {RouteGuideClient client = new RouteGuideClient("localhost", 50051);try {client.getFeature(409146138, -746188906);//成功案例client.getFeature(0, 0);//失败案例} finally {client.shutdown();}}

客户端日志

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服务端日志(参数都为0的时候,这边并没拿到参数)

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服务器端流式 RPC
和简单RPC差不多,只不过返回的是一个集合类.

//2.服务端流式RPCpublic void listFeatures(int lowLat, int lowLon, int hiLat, int hiLon){System.out.println("start listFeatures");Rectangle request =Rectangle.newBuilder().setLo(Point.newBuilder().setLatitude(lowLat).setLongitude(lowLon).build()).setHi(Point.newBuilder().setLatitude(hiLat).setLongitude(hiLon).build()).build();Iterator<Feature> features;try {features = blockingStub.listFeatures(request);for (int i = 1; features.hasNext(); i++) {Feature feature = features.next();System.out.println("getFeature服务端返回 :" + feature);}} catch (Exception e) {System.out.println("RPC failed " +e.getMessage());}}

客户端日志:

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服务端日志:

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客户端流式 RPC
该种方式两遍都是异步操作,所以需要互相监听,也因此需要使用阻塞存根.服务端监听Point的写入,客户端监听RouteSummary的写回.

public void recordRoute(List<Feature> features, int numPoints) throws InterruptedException {System.out.println("start recordRoute");final CountDownLatch finishLatch = new CountDownLatch(1);//建一个应答者接受返回数据StreamObserver<RouteSummary> responseObserver = new StreamObserver<RouteSummary>() {@Overridepublic void onNext(RouteSummary summary) {System.out.println("recordRoute服务端返回 :" + summary);}@Overridepublic void onError(Throwable t) {System.out.println("RecordRoute Failed");finishLatch.countDown();}@Overridepublic void onCompleted() {System.out.println("RecordRoute finish");finishLatch.countDown();}};//客户端写入操作StreamObserver<Point> requestObserver = asyncStub.recordRoute(responseObserver);Random random = new Random();try {for (int i = 0; i < numPoints; ++i) {int index = random.nextInt(features.size());Point point = features.get(index).getLocation();System.out.println("客户端写入point:" + point);requestObserver.onNext(point);Thread.sleep(random.nextInt(1000) + 500);if (finishLatch.getCount() == 0) {return;}}} catch (RuntimeException e) {requestObserver.onError(e);throw e;}//标识已经写完requestObserver.onCompleted();// Receiving happens asynchronouslyif (!finishLatch.await(1, TimeUnit.MINUTES)) {System.out.println("recordRoute can not finish within 1 minutes");}}

客户端日志:

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服务端日志:

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双向流式 RPC
和客户端流式RPC比较接近,同样都需要双方监控.

public CountDownLatch routeChat() {System.out.println("start routeChat");final CountDownLatch finishLatch = new CountDownLatch(1);//写入监听StreamObserver<RouteNote> requestObserver =//写回监听asyncStub.routeChat(new StreamObserver<RouteNote>() {//服务端每写回一个操作就调用@Overridepublic void onNext(RouteNote note) {System.out.println("服务端写回: " + note);}@Overridepublic void onError(Throwable t) {t.printStackTrace();System.out.println("RouteChat Failed:");finishLatch.countDown();}@Overridepublic void onCompleted() {System.out.println("Finished RouteChat");finishLatch.countDown();}});try {RouteNote[] requests ={newNote("First message", 0, 0), newNote("Second message", 0, 1),newNote("Third message", 1, 0), newNote("Fourth message", 1, 1)};for (RouteNote request : requests) {System.out.println("客户端写入:" + request);requestObserver.onNext(request);}} catch (RuntimeException e) {requestObserver.onError(e);throw e;}//标识写完requestObserver.onCompleted();return finishLatch;}

这里调用需要特殊处理下;

            CountDownLatch finishLatch = client.routeChat();if (!finishLatch.await(1, TimeUnit.MINUTES)) {System.out.println("routeChat can not finish within 1 minutes");}

客户端日志:

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服务端日志:

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官方Demo之后,入门算结束,接下来就要看详细的官方文档,然后在项目中使用,这个过程会遇到不少问题,解决这些问题就是对这个技术的熟练.

附录:

相关代码: https://github.com/nl101531/JavaWEB