Question

我正在尝试使用以下代码实验室使用Java创建gRPC服务。我创建了一个样本原型文件。在使用Maven编译.proto时，出现了构建失败错误。它说没有找到javax.annotation.Generated配音类。

您能帮我找到问题的根本原因和解决此问题的步骤。我觉得这应该是版本控制问题，但不清楚如何解决。

https://codelabs.developers.google.com/codelabs/cloud-grpc-java/index.html?index=..%2F..index#2

错误：

[ERROR] COMPILATION ERROR :
[INFO] -------------------------------------------------------------
[ERROR] /home/grpc_hello_server/target/generated-sources/protobuf/grpc-java/com/example/grpc/GreetingServiceGrpc.java:[20,18] cannot find symbol
  symbol:   class Generated
  location: package javax.annotation
[INFO] 1 error
[INFO] -------------------------------------------------------------
[INFO] ------------------------------------------------------------------------
[INFO] BUILD FAILURE
[INFO] ------------------------------------------------------------------------
[INFO] Total time:  9.845 s
[INFO] Finished at: 2020-06-29T16:56:21-07:00
[INFO] ------------------------------------------------------------------------
[ERROR] Failed to execute goal org.apache.maven.plugins:maven-compiler-plugin:3.1:compile (default-compile) on project grpc_hello_server: Compilation failure
[ERROR] /home/grpc_hello_server/target/generated-sources/protobuf/grpc-java/com/example/grpc/GreetingServiceGrpc.java:[20,18] cannot find symbol
[ERROR]   symbol:   class Generated
[ERROR]   location: package javax.annotation
[ERROR]
[ERROR] -> [Help 1]
[ERROR]
[ERROR] To see the full stack trace of the errors, re-run Maven with the -e switch.
[ERROR] Re-run Maven using the -X switch to enable full debug logging.
[ERROR] For more information about the errors and possible solutions, please read the following articles:
[ERROR] [Help 1] http://cwiki.apache.org/confluence/display/MAVEN/MojoFailureException.

pom.xml

  <project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/maven-v4_0_0.xsd">
  <modelVersion>4.0.0</modelVersion>
  <groupId>com.example.grpc</groupId>
  <artifactId>grpc_hello_server</artifactId>
  <packaging>jar</packaging>
  <version>1.0-SNAPSHOT</version>
  <name>grpc_hello_server</name>
  <url>http://maven.apache.org</url>
  <dependencies>
    <dependency>
      <groupId>junit</groupId>
      <artifactId>junit</artifactId>
      <version>3.8.1</version>
      <scope>test</scope>
    </dependency>

    <dependency>
        <groupId>io.grpc</groupId>
        <artifactId>grpc-netty</artifactId>
        <version>1.7.0</version>
    </dependency>

    <dependency>
        <groupId>io.grpc</groupId>
        <artifactId>grpc-protobuf</artifactId>
        <version>1.7.0</version>
    </dependency>

    <dependency>
        <groupId>io.grpc</groupId>
        <artifactId>grpc-stub</artifactId>
        <version>1.7.0</version>
    </dependency>
  </dependencies>
  <properties>
    <maven.compiler.source>1.6</maven.compiler.source>
    <maven.compiler.target>1.6</maven.compiler.target>
  </properties>
  <build>
      <extensions>
          <extension>
              <groupId>kr.motd.maven</groupId>
              <artifactId>os-maven-plugin</artifactId>
              <version>1.6.2</version>
          </extension>
      </extensions>
      <plugins>
          <plugin>
              <groupId>org.xolstice.maven.plugins</groupId>
              <artifactId>protobuf-maven-plugin</artifactId>
              <version>0.5.0</version>
              <configuration>
                  <protocArtifact>com.google.protobuf:protoc:3.4.0:exe:${os.detected.classifier}</protocArtifact>
                  <pluginId>grpc-java</pluginId>
                  <pluginArtifact>io.grpc:protoc-gen-grpc-java:1.7.0:exe:${os.detected.classifier}</pluginArtifact>
              </configuration>
              <executions>
                  <execution>
                      <goals>
                          <goal>compile</goal>
                          <goal>compile-custom</goal>
                      </goals>
                  </execution>
              </executions>
          </plugin>
      </plugins>
  </build>
</project>

Answer 1

您是否使用Java 1.6？

    <maven.compiler.source>1.6</maven.compiler.source>
    <maven.compiler.target>1.6</maven.compiler.target>

您可以将其更改为1.7，然后查看是否有效吗？

Answer 2

问题是由于缺少Java 9+的pom.xml中的依赖关系

    <dependency> <!-- necessary for Java 9+ -->
        <groupId>org.apache.tomcat</groupId>
        <artifactId>annotations-api</artifactId>
        <version>6.0.53</version>
        <scope>provided</scope>
    </dependency>

无法在项目grpc_hello_server上执行目标org.apache.maven.plugins：maven-compiler-plugin：3.1：compile（default-compile）：编译失败

2 个答案: