如何运行 akka grpc java 示例

Question

好的，按照使用 Java 的先决条件和说明 8 项目创建工作。

sbt new akka/akka-grpc-quickstart-java.g8

然后继续使用指南

./gradlew compileJava也可以。

但是随后./gradlew --info runServer因以下错误/问题而失败：

Task ':runServer' is not up-to-date because:
Task has not declared any outputs.

和

Error: Main method not found in class com.example.helloworld.GreeterServer, please define the main method as:
   public static void main(String[] args)

原帖：

我无法运行 Akka-GRPC 示例。 我在这里尝试按照本指南进行操作，但是当我下载示例项目时，它似乎不完整。

那是树命令 output：

.
├── build.sbt
├── project
│   ├── build.properties
│   └── plugins.sbt
├── sbt
├── sbt.bat
└── sbt-dist
    ├── bin
    │   ├── sbt
    │   ├── sbt.bat
    │   ├── sbt-launch.jar
    │   └── sbt-launch-lib.bash
    └── conf
        ├── sbtconfig.txt
        └── sbtopts

4 directories, 11 files

项目结构中没有源文件或 gradlew oder pom.xml。

接下来，我从 GitHub 克隆了该示例的存储库，并按照自述文件中的说明进行操作，主要是命令sbt new akka/akka-grpc-quickstart-java.g8 。

$ sbt new akka/akka-grpc-quickstart-java.g8
[info] Loading settings for project akka-grpc-quickstart-java-g8-build from paradox.sbt,giter8.sbt ...
[info] Loading project definition from /home/johannes/IdeaProjects/akka-grpc-quickstart-java.g8/project
error: error while loading String, class file '/modules/java.base/java/lang/String.class' is broken
(class java.lang.NullPointerException/null)
[error] java.io.IOError: java.lang.RuntimeException: /packages cannot be represented as URI
...//had to remove stacktrace was too long for this post
[error]     at xsbt.boot.Boot.main(Boot.scala)
Project loading failed: (r)etry, (q)uit, (l)ast, or (i)gnore? [error] java.io.IOError: java.lang.RuntimeException: /packages cannot be represented as URI
[error] Use 'last' for the full log.

然后我进入源文件所在的 project/sources 文件夹./src/main/g8/ 并尝试按照那里的指南中的说明进行操作。 由于某些属性错误，这也不起作用：

在此之前，我必须在./gradle/wrapper/gradle-wrapper.properties 中设置另一个 gradle 版本（6.1.1，是 4.5.1）以使其与 Java 13 兼容。

$ ./gradlew compileJava

FAILURE: Build failed with an exception.

* What went wrong:
A problem occurred configuring root project 'g8'.
> Could not resolve all artifacts for configuration ':classpath'.
   > Could not find gradle.plugin.com.lightbend.akka.grpc:akka-grpc-gradle-plugin:$akka_grpc_version$.
     Searched in the following locations:
       - file:/home/johannes/.m2/repository/gradle/plugin/com/lightbend/akka/grpc/akka-grpc-gradle-plugin/$akka_grpc_version$/akka-grpc-gradle-plugin-$akka_grpc_version$.pom
       - https://plugins.gradle.org/m2/gradle/plugin/com/lightbend/akka/grpc/akka-grpc-gradle-plugin/$akka_grpc_version$/akka-grpc-gradle-plugin-$akka_grpc_version$.pom
     Required by:
         project :

* Try:
Run with --stacktrace option to get the stack trace. Run with --info or --debug option to get more log output. Run with --scan to get full insights.

* Get more help at https://help.gradle.org

BUILD FAILED in 4s

为了至少暂时让它工作，我将属性硬编码到 build.gradle 文件中：

     //classpath 'gradle.plugin.com.lightbend.akka.grpc:akka-grpc-gradle-plugin:$akka_grpc_version$'
     classpath 'gradle.plugin.com.lightbend.akka.grpc:akka-grpc-gradle-plugin:0.7.3'

但这也只是让我到目前为止：

$ ./gradlew compileJava

FAILURE: Build failed with an exception.

* Where:
Build file '/home/johannes/IdeaProjects/akka-grpc-quickstart-java.g8/src/main/g8/build.gradle' line: 20

* What went wrong:
A problem occurred evaluating root project 'g8'.
> Failed to apply plugin [id 'com.google.protobuf']
   > Could not create an instance of type com.google.protobuf.gradle.ProtobufSourceDirectorySet.
      > 'void org.gradle.api.internal.file.DefaultSourceDirectorySet.<init>(java.lang.String, java.lang.String, org.gradle.api.internal.file.FileResolver, org.gradle.api.internal.file.collections.DirectoryFileTreeFactory)'

* Try:
Run with --stacktrace option to get the stack trace. Run with --info or --debug option to get more log output. Run with --scan to get full insights.

* Get more help at https://help.gradle.org

BUILD FAILED in 1s

由于字符限制，再次无法包含整个堆栈跟踪。

我错过了什么？ 我应该进一步采用哪种方法？

Answer 1

编辑：同时，拉取请求被接受，主回购（ https://github.com/akka/akka-grpc-quickstart-java.g8 ）是最新的。

我使用 sbt new... 下载了项目，但是 pom.xml 中出现错误（固定版本： https://github.com/olitazl/akka-grpc-quickstart-java.g8 ）

示例项目的问题是缺少 GreeterServer 内部的public修饰符GreeterServer 。

因此，您必须将public添加到 GreeterServer class 和其中的方法main 。

    public class GreeterServer ...
    public static void main(...)

如果您从我的存储库重新创建您的项目，问题也已解决。