前言
最近的一個項目使用到了grpc實現跨平臺的遠程調用，在安卓端使用的時候遇到了一些坑，這里記錄一下。
首先根據grpc android的官方Demo配置grpc依賴，測試它的hello world工程。
編譯谷歌官方的helloworld工程
添加rotobuf-gradle-plugin插件
首先添加rotobuf-gradle-plugin插件，他是用來從proto文件自動生成java代碼的:
//Project的build.gradle中添加rotobuf-gradle-plugin插件buildscript { ... dependencies { ... classpath "com.google.protobuf:protobuf-gradle-plugin:0.8.0" ... } ...}//App的build.gradle中添加下面配置apply plugin: 'com.google.protobuf'protobuf { protoc { artifact = 'com.google.protobuf:protoc:3.0.0' } plugins { javalite { artifact = "com.google.protobuf:protoc-gen-javalite:3.0.0" } grpc { artifact = 'io.grpc:protoc-gen-grpc-java:1.0.0' // CURRENT_GRPC_VERSION } } generateProtoTasks { all().each { task -> task.plugins { javalite {} grpc { // Options added to --grpc_out option 'lite' } } } }}添加proto文件并自動生成java代碼
在src/main/目錄下創建一個proto目錄，并將官方的helloworld.proto放到proto目錄下
之后只需要rebuild一下就能看到build/generated/source/proto/目錄下根據helloworld.proto生成了幾個Java類
添加安卓端grpc的依賴
//App的build.gradle中添加下面配置 dependencies { ... compile 'io.grpc:grpc-okhttp:1.1.2' compile 'io.grpc:grpc-protobuf-lite:1.1.2' compile 'io.grpc:grpc-stub:1.1.2' compile 'javax.annotation:javax.annotation-api:1.2' ...}configurations.all { resolutionStrategy.force 'com.google.code.findbugs:jsr305:3.0.1' }我這個時候報了這個錯誤
Warning:Conflict with dependency ‘com.google.code.findbugs:jsr305'. Resolved versions for app (3.0.0) and test app (2.0.1) differ. See http://g.co/androidstudio/app-test-app-conflict for details.
這是因為com.google.code.findbugs:jsr305的版本不一致導致的
可以在App的build.gradle的android標簽中配置一下解決
android { ... configurations.all { resolutionStrategy.force 'com.google.code.findbugs:jsr305:3.0.1' } ...}編寫demo代碼
public class MainActivity extends AppCompatActivity { private static final String TAG = "GrpcDemo"; private static final int PROT = 55055; private static final String NAME = "linjw"; private static final String HOST = "localhost"; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); startServer(PROT); startClient(HOST, PROT, NAME); } private void startServer(int port){ try { Server server = ServerBuilder.forPort(port) .addService(new GreeterImpl()) .build() .start(); } catch (IOException e) { e.printStackTrace(); Log.d(TAG, e.getMessage()); } } private void startClient(String host, int port, String name){ new GrpcTask(host, port, name).execute(); } private class GreeterImpl extends GreeterGrpc.GreeterImplBase { public void sayHello(HelloRequest request, StreamObserver<HelloReply> responseObserver) { responseObserver.onNext(sayHello(request)); responseObserver.onCompleted(); } private HelloReply sayHello(HelloRequest request) { return HelloReply.newBuilder() .setMessage("hello "+ request.getName()) .build(); } } private class GrpcTask extends AsyncTask<Void, Void, String> { private String mHost; private String mName; private int mPort; private ManagedChannel mChannel; public GrpcTask(String host, int port, String name) { this.mHost = host; this.mName = name; this.mPort = port; } @Override protected void onPreExecute() { } @Override protected String doInBackground(Void... nothing) { try { mChannel = ManagedChannelBuilder.forAddress(mHost, mPort) .usePlaintext(true) .build(); GreeterGrpc.GreeterBlockingStub stub = GreeterGrpc.newBlockingStub(mChannel); HelloRequest message = HelloRequest.newBuilder().setName(mName).build(); HelloReply reply = stub.sayHello(message); return reply.getMessage(); } catch (Exception e) { StringWriter sw = new StringWriter(); PrintWriter pw = new PrintWriter(sw); e.printStackTrace(pw); pw.flush(); return "Failed... : " + System.lineSeparator() + sw; } } @Override protected void onPostExecute(String result) { try { mChannel.shutdown().awaitTermination(1, TimeUnit.SECONDS); } catch (InterruptedException e) { Thread.currentThread().interrupt(); } Log.d(TAG, result); } }}這段代碼運行會崩潰:
Caused by: io.grpc.ManagedChannelProvider$ProviderNotFoundException: No functional server found. Try adding a dependency on the grpc-netty artifact
猜測google使用netty替代了okhttp，嘗試換成grpc-netty的依賴:
dependencies { ... compile 'io.grpc:grpc-netty:1.1.2' compile 'io.grpc:grpc-protobuf-lite:1.1.2' compile 'io.grpc:grpc-stub:1.1.2' compile 'javax.annotation:javax.annotation-api:1.2' ...}這么編譯會報錯
com.android.build.api.transform.TransformException: com.android.builder.packaging.DuplicateFileException: Duplicate files copied in APK META-INF/INDEX.LIST
需要加上下面的配置解決
android { ... packagingOptions { pickFirst 'META-INF/INDEX.LIST' pickFirst 'META-INF/LICENSE' pickFirst 'META-INF/io.netty.versions.properties' } ...}當然，還需要加上INTERNET權限，要不然運行的時候還是會崩潰。
最終就能看的下面的打印，這樣安卓grpc的helloworld就成功了。
03-03 00:04:20.000 6137-6137/linjw.com.grpcdemo D/GrpcDemo: hello linjw
使用com.google.protobuf.Any
Any可以攜帶任意類型的數據，用法相當于c語言的void指針。在項目中是很常用的，但是谷歌在javalite的版本不支持Any。
如果在proto文件中使用了Any的話生成java代碼就會有報錯，例如將helloworld的proto文件改成下面的樣子:
// Copyright 2015, Google Inc.// All rights reserved.//// Redistribution and use in source and binary forms, with or without// modification, are permitted provided that the following conditions are// met://// * Redistributions of source code must retain the above copyright// notice, this list of conditions and the following disclaimer.// * Redistributions in binary form must reproduce the above// copyright notice, this list of conditions and the following disclaimer// in the documentation and/or other materials provided with the// distribution.// * Neither the name of Google Inc. nor the names of its// contributors may be used to endorse or promote products derived from// this software without specific prior written permission.//// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.syntax = "proto3";option java_multiple_files = true;option java_package = "io.grpc.examples.helloworld";option java_outer_classname = "HelloWorldProto";option objc_class_prefix = "HLW";package helloworld;import "google/protobuf/any.proto";// The greeting service definition.service Greeter { // Sends a greeting rpc SayHello (google.protobuf.Any) returns (HelloReply) {}}// The request message containing the user's name.message HelloRequest { string name = 1;}// The response message containing the greetingsmessage HelloReply { string message = 1;}
報錯如下
google/protobuf/any.proto: File not found.helloworld.proto: Import “google/protobuf/any.proto” was not found or had errors.helloworld.proto:44:17: “google.protobuf.Any” is not defined.
使用grpc-jave代替grpc-javalite
但是現在做的這個項目的linux端實現已經用了Any，要改的話需要耗費比較大的精力。幸好嘗試了下，發現安卓上也能跑支持Any的grpc-java。
首先我們要使用grpc-protobuf依賴替換grpc-protobuf-lite依賴
dependencies { ... compile 'io.grpc:grpc-netty:1.1.2' compile 'io.grpc:grpc-protobuf:1.1.2' compile 'io.grpc:grpc-stub:1.1.2' compile 'javax.annotation:javax.annotation-api:1.2' ...}接著修改protobuf-gradle-plugin配置使得自動生成java的代碼而不是javalite的代碼
protobuf { protoc { artifact = 'com.google.protobuf:protoc:3.0.0' } plugins { grpc { artifact = 'io.grpc:protoc-gen-grpc-java:1.0.0' // CURRENT_GRPC_VERSION } } generateProtoTasks { all().each { task -> task.builtins { java {} } task.plugins { grpc {} } } }}對應的修改helloworld的代碼就能運行了
public class MainActivity extends AppCompatActivity { private static final String TAG = "GrpcDemo"; private static final int PROT = 55055; private static final String NAME = "linjw"; private static final String HOST = "localhost"; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); startServer(PROT); startClient(HOST, PROT, NAME); } private void startServer(int port){ try { Server server = ServerBuilder.forPort(port) .addService(new GreeterImpl()) .build() .start(); } catch (IOException e) { e.printStackTrace(); Log.d(TAG, e.getMessage()); } } private void startClient(String host, int port, String name){ new GrpcTask(host, port, name).execute(); } private class GreeterImpl extends GreeterGrpc.GreeterImplBase { public void sayHello(Any request, StreamObserver<HelloReply> responseObserver) { try { responseObserver.onNext(sayHello(request.unpack(HelloRequest.class))); responseObserver.onCompleted(); } catch (InvalidProtocolBufferException e) { e.printStackTrace(); } } private HelloReply sayHello(HelloRequest request) { return HelloReply.newBuilder() .setMessage("hello "+ request.getName()) .build(); } } private class GrpcTask extends AsyncTask<Void, Void, String> { private String mHost; private String mName; private int mPort; private ManagedChannel mChannel; public GrpcTask(String host, int port, String name) { this.mHost = host; this.mName = name; this.mPort = port; } @Override protected void onPreExecute() { } @Override protected String doInBackground(Void... nothing) { try { mChannel = ManagedChannelBuilder.forAddress(mHost, mPort) .usePlaintext(true) .build(); GreeterGrpc.GreeterBlockingStub stub = GreeterGrpc.newBlockingStub(mChannel); HelloRequest message = HelloRequest.newBuilder().setName(mName).build(); HelloReply reply = stub.sayHello(Any.pack(message)); return reply.getMessage(); } catch (Exception e) { StringWriter sw = new StringWriter(); PrintWriter pw = new PrintWriter(sw); e.printStackTrace(pw); pw.flush(); return "Failed... : " + System.lineSeparator() + sw; } } @Override protected void onPostExecute(String result) { try { mChannel.shutdown().awaitTermination(1, TimeUnit.SECONDS); } catch (InterruptedException e) { Thread.currentThread().interrupt(); } Log.d(TAG, result); } }}完整的demo代碼可以點這里在我的github中查看（也可以通過本地下載）
Android方法數不能超過65535的問題
最后使用grpc，方法數會超過65535，可以使用com.android.support:multidex去解決
總結
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