使用Maven插件构建Protocol Buffer项目时proto导入报错求助

问题描述 #

使用Maven插件开发Protocol Buffers项目时，构建报错：hello2.proto: Import "h/hello.proto" was not found or had errors，同时期望按指定包生成Java文件但未实现。

现有文件内容 #

hello.proto（路径：src/main/resources/proto/h/hello.proto）

syntax = "proto3";

//option java_multiple_files = true;
option java_package = "com.poc_cipertrace.hello";
option java_outer_classname = "HelloWorldRequest";

message HelloRequest {
  string name = 1;
}

hello2.proto（路径：src/main/resources/proto/hello2.proto）

syntax = "proto3";

option java_package = "com.poc.poc_cipertrace.hello";
option java_outer_classname = "HelloWorldResponse";

import "h/hello.proto";

message HelloResponse {
  HelloRequest h=1;
}

现有pom.xml插件配置

<plugin>
    <groupId>com.github.os72</groupId>
    <artifactId>protoc-jar-maven-plugin</artifactId>
    <version>3.6.0.1</version>
    <executions>
        <execution>
            <phase>generate-sources</phase>
            <goals>
                <goal>run</goal>
            </goals>
            <configuration>
                <includeMavenTypes>direct</includeMavenTypes>
                <inputDirectories>
                    <include>src/main/resources/proto</include>
                </inputDirectories>
                <outputTargets>
                    <outputTarget>
                        <type>java</type>
                        <outputDirectory>src/main/java</outputDirectory>
                    </outputTarget>
                    <outputTarget>
                        <type>grpc-java</type>
                        <pluginArtifact>io.grpc:protoc-gen-grpc-java:1.15.0</pluginArtifact>
                        <outputDirectory>src/main/java</outputDirectory>
                    </outputTarget>
                </outputTargets>
            </configuration>
        </execution>
    </executions>
</plugin>

项目结构 #

src/main/resources/proto
├── h
│ └── hello.proto
└── hello2.proto

修复步骤 #

1. 配置Proto搜索根路径 #

问题核心是protoc未将src/main/resources/proto识别为Proto文件的根目录，导致找不到h/hello.proto。需在插件配置中添加<protoPaths>指定根路径：

修改后的插件配置：

<plugin>
    <groupId>com.github.os72</groupId>
    <artifactId>protoc-jar-maven-plugin</artifactId>
    <version>3.6.0.1</version>
    <executions>
        <execution>
            <phase>generate-sources</phase>
            <goals>
                <goal>run</goal>
            </goals>
            <configuration>
                <includeMavenTypes>direct</includeMavenTypes>
                <!-- 添加Proto根路径，让protoc能找到h/hello.proto -->
                <protoPaths>
                    <protoPath>src/main/resources/proto</protoPath>
                </protoPaths>
                <inputDirectories>
                    <include>src/main/resources/proto</include>
                </inputDirectories>
                <outputTargets>
                    <outputTarget>
                        <type>java</type>
                        <!-- 建议生成到target目录，符合Maven规范，避免覆盖手动代码 -->
                        <outputDirectory>target/generated-sources/protobuf/java</outputDirectory>
                    </outputTarget>
                    <outputTarget>
                        <type>grpc-java</type>
                        <pluginArtifact>io.grpc:protoc-gen-grpc-java:1.15.0</pluginArtifact>
                        <outputDirectory>target/generated-sources/protobuf/grpc-java</outputDirectory>
                    </outputTarget>
                </outputTargets>
            </configuration>
        </execution>
    </executions>
</plugin>

2. 修正Proto文件的引用问题 #

hello2.proto中直接使用HelloRequest会因包名不一致导致识别失败，可选择以下两种方案：

• 方案一：添加统一package声明
  修改hello.proto：

  syntax = "proto3";
  package hello; // 添加package
  
  option java_package = "com.poc_cipertrace.hello";
  option java_outer_classname = "HelloWorldRequest";
  
  message HelloRequest {
    string name = 1;
  }
  

  修改hello2.proto：

  syntax = "proto3";
  package hello; // 添加相同的package
  
  option java_package = "com.poc.poc_cipertrace.hello";
  option java_outer_classname = "HelloWorldResponse";
  
  import "h/hello.proto";
  
  message HelloResponse {
    hello.HelloRequest h=1; // 使用全限定名引用
  }
  

• 方案二：统一java_package
  将hello2.proto的java_package改为com.poc_cipertrace.hello，生成的Java类会在同一个包下，可直接引用HelloRequest。

3. 配置Maven识别生成的源代码目录 #

如果将生成代码放到target目录，需要让Maven编译时包含该目录，可添加build-helper-maven-plugin：

<plugin>
    <groupId>org.codehaus.mojo</groupId>
    <artifactId>build-helper-maven-plugin</artifactId>
    <version>3.3.0</version>
    <executions>
        <execution>
            <id>add-source</id>
            <phase>generate-sources</phase>
            <goals>
                <goal>add-source</goal>
            </goals>
            <configuration>
                <sources>
                    <source>target/generated-sources/protobuf/java</source>
                    <source>target/generated-sources/protobuf/grpc-java</source>
                </sources>
            </configuration>
        </execution>
    </executions>
</plugin>

内容的提问来源于stack exchange，提问作者Nisarg Raval