Java gRPC 服务器未启动

Question

我正在尝试在我的代码中实现 gRPC 服务，条件是使用服务器 class 的一个实例，代码构建成功，但出现运行时错误。

我该如何解决这个错误？

Exception in thread "main" java.lang.NullPointerException: bindableService
   at com.google.common.base.Preconditions.checkNotNull(Preconditions.java:897)
   at io.grpc.internal.AbstractServerImplBuilder.addService(AbstractServerImplBuilder.java:120)
   at io.grpc.internal.AbstractServerImplBuilder.addService(AbstractServerImplBuilder.java:56)
   at com.mypackage.cu.comms.CURequestHandlerService.<init>(Unknown Source)
   at com.mypackage.cu.comms.CURequestHandlerService.start(Unknown Source)
   at com.mypackage.cu.entities.ControlUnit.initSystem(Unknown Source)
   at com.mypackage.cu.entities.ControlUnit.run(Unknown Source)
   at com.mypackage.cu.entities.ControlUnit.main(Unknown Source)

• 生成的 grpc java class 是 CURequestHandlerGrpc。
• 服务器 class CURequestHandlerService：

import io.grpc.Server;
import io.grpc.ServerBuilder;
import io.grpc.stub.StreamObserver;
\\ ..

public class CURequestHandlerService extends CURequestHandlerGrpc.CURequestHandlerImplBase {
  private final Server server;
  private static CURequestHandlerService INSTANCE = null;
  private CURequestHandlerService(int port) {
    this.server = ServerBuilder.forPort(port)
            .addService(INSTANCE)
            .build();
  }

  public static void start(int port) {
    if (INSTANCE == null)
      INSTANCE = new CURequestHandlerService(port);

    try {
      INSTANCE.server.start();
    } catch (IOException e) {
      System.out.println("Can't start GRPC server!");
    }
  }

• 在主 class

CURequestHandlerService.start(16440);

我正在使用 Ant 因为它是一个旧项目并且我正在维护它。 我将所有 grpc 依赖项 jars 添加到依赖项目录。

• 我的依赖项 jars：

amqp-client-5.7.3.jar
failureaccess-1.0.1.jar
grpc-all-1.27.0.jar
grpc-api-1.27.0.jar
grpc-auth-1.27.0.jar
grpc-context-1.27.0.jar
grpc-core-1.27.0.jar
grpc-netty-1.27.0.jar
grpc-netty-shaded-1.27.0.jar
grpc-protobuf-1.27.0.jar
grpc-protobuf-lite-1.27.0.jar
grpc-stub-1.27.0.jar
grpc-testing-1.27.0.jar
guava-28.2-jre.jar
json-smart-1.2.jar
lettuce-4.3.0.Final-shaded.jar
libthrift-0.9.3.jar
opencensus-api-0.20.0.jar
opencensus-contrib-grpc-metrics-0.20.0.jar
perfmark-api-0.21.0.jar
protobuf-java-3.11.3.jar
protobuf-java-util-3.11.3.jar
protoc-gen-grpc-java-1.27.0-linux-x86_64.exe
slf4j-api-1.7.22.jar
slf4j-simple-1.7.22.jar

Answer 1

在阅读grpc-java存储库中的服务器示例后，我发现问题不是依赖问题。 我偷偷告诉你，你必须将服务器 class 与从 Grpc 生成的 class 扩展的实现 class 分开。

• 服务器 class

/**
 * Grpc instance class that used to initiate the server and call implementation class
 */
public class GrpcServer {
    private final Server server;
    private static GrpcServer INSTANCE = null;
    private GrpcServer(int port) {
        this.server = ServerBuilder.forPort(port)
                .addService(new CURequestHandlerService())
                .build();
    }

    public static void start(int port) {
        if (INSTANCE == null)
            INSTANCE = new GrpcServer(port);

        try {
            INSTANCE.server.start();
            System.out.println("GRPC server started");
        } catch (IOException e) {
            System.out.println("Can't start GRPC server!");
        }
    }
}

• 执行 class

**
 * Request Handler class contains the implementation for all functions initiated in proto files
 * The implemented function 
 * */
public class CURequestHandlerService extends CURequestHandlerGrpc.CURequestHandlerImplBase{


  public synchronized void Method1(Messages.Method1Input input,
                                         StreamObserver<Messages.Method1Output> output) {
    //...
    output.onNext(outputResponse);
    output.onCompleted();
  }