Android上使用grpc的方法教程

前言

最近的一个项目使用到了grpc实现跨平台的远程调用，在安卓端使用的时候遇到了一些坑，这里记录一下。

首先根据grpc android的官方demo配置grpc依赖，测试它的hello world工程。

编译谷歌官方的helloworld工程

添加rotobuf-gradle-plugin插件

首先添加rotobuf-gradle-plugin插件，他是用来从proto文件自动生成java代码的:

//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文件并自动生成java代码

在src/main/目录下创建一个proto目录，并将官方的放到proto目录下

之后只需要rebuild一下就能看到build/generated/source/proto/目录下根据helloworld.proto生成了几个java类

添加安卓端grpc的依赖

//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'
 }

我这个时候报了这个错误

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.

这是因为com.google.code.findbugs:jsr305的版本不一致导致的

可以在app的build.gradle的android标签中配置一下解决

android {
 ...
 configurations.all {
 resolutionstrategy.force 'com.google.code.findbugs:jsr305:3.0.1'
 }
 ...
}

编写demo代码

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);
 }
 }
}

这段代码运行会崩溃:

caused by: io.grpc.managedchannelprovider$providernotfoundexception: no functional server found. try adding a dependency on the grpc-netty artifact

猜测google使用netty替代了okhttp，尝试换成grpc-netty的依赖:

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'
 ...
}

这么编译会报错

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决

android {
 ...
 packagingoptions {
 pickfirst 'meta-inf/index.list'
 pickfirst 'meta-inf/license'
 pickfirst 'meta-inf/io.netty.versions.properties'
 }
 ...
}

当然，还需要加上internet权限，要不然运行的时候还是会崩溃。

最终就能看的下面的打印，这样安卓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可以携带任意类型的数据，用法相当于c语言的void指针。在项目中是很常用的，但是谷歌在javalite的版本不支持any。

如果在proto文件中使用了any的话生成java代码就会有报错，例如将helloworld的proto文件改成下面的样子:

// 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 greetings
message helloreply {
 string message = 1;
}

报错如下

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

但是现在做的这个项目的linux端实现已经用了any，要改的话需要耗费比较大的精力。幸好尝试了下，发现安卓上也能跑支持any的grpc-java。

首先我们要使用grpc-protobuf依赖替换grpc-protobuf-lite依赖

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'
 ...
}

接着修改protobuf-gradle-plugin配置使得自动生成java的代码而不是javalite的代码

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 {}
   }
  }
 }
}

对应的修改helloworld的代码就能运行了

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代码可以点这里在我的中查看（也可以通过）

android方法数不能超过65535的问题

最后使用grpc，方法数会超过65535，可以使用com.android.support:multidex去解决

总结

以上就是这篇文章的全部内容了，希望本文的内容对大家的学习或者工作能带来一定的帮助，如有疑问大家可以留言交流，谢谢大家对的支持。