如何用Maven Enforcer规则确保自定义Compat模块优先于Protobuf类路径？

一、通用场景：强制模块X类路径优先于Y #

要确保模块M的直接依赖X在Y之前加载，最简便的方式是用Maven Enforcer的Groovy脚本规则，直接检查依赖声明顺序，防止未来被意外调换：

在模块M的pom.xml中添加如下配置：

<plugin>
  <groupId>org.apache.maven.plugins</groupId>
  <artifactId>maven-enforcer-plugin</artifactId>
  <version>3.4.1</version>
  <executions>
    <execution>
      <id>enforce-x-before-y</id>
      <goals>
        <goal>enforce</goal>
      </goals>
      <configuration>
        <rules>
          <scriptRule>
            <script>
              <![CDATA[
                def xGroup = "你的X模块groupId"
                def xArtifact = "你的X模块artifactId"
                def yGroup = "你的Y模块groupId"
                def yArtifact = "你的Y模块artifactId"

                def xSeen = false
                for (dep in project.dependencies) {
                  if (dep.groupId == xGroup && dep.artifactId == xArtifact) {
                    xSeen = true
                  } else if (dep.groupId == yGroup && dep.artifactId == yArtifact) {
                    if (!xSeen) {
                      fail("依赖${yGroup}:${yArtifact}不能出现在${xGroup}:${xArtifact}之前，请调整pom中的依赖声明顺序")
                    }
                  }
                }
                // 可选：检查两个依赖是否都存在
                if (!project.dependencies.any { it.groupId == xGroup && it.artifactId == xArtifact }) {
                  fail("未检测到依赖${xGroup}:${xArtifact}")
                }
                if (!project.dependencies.any { it.groupId == yGroup && it.artifactId == yArtifact }) {
                  fail("未检测到依赖${yGroup}:${yArtifact}")
                }
              ]]>
            </script>
            <language>groovy</language>
          </scriptRule>
        </rules>
      </configuration>
    </execution>
  </executions>
  <dependencies>
    <dependency>
      <groupId>org.codehaus.groovy</groupId>
      <artifactId>groovy-all</artifactId>
      <version>3.0.17</version>
      <scope>runtime</scope>
    </dependency>
  </dependencies>
</plugin>

这个脚本会遍历模块的直接依赖列表，一旦发现Y在X之前声明就抛出错误，锁定顺序。

二、Protobuf兼容模块的类路径强制 #

针对你遇到的Protobuf 2.4/2.5 ABI冲突问题，要确保自定义的compat模块优先于官方protobuf-java:2.5加载，只需要调整上面的脚本，针对运行时依赖做检查：

<plugin>
  <groupId>org.apache.maven.plugins</groupId>
  <artifactId>maven-enforcer-plugin</artifactId>
  <version>3.4.1</version>
  <executions>
    <execution>
      <id>enforce-protobuf-compat-order</id>
      <goals>
        <goal>enforce</goal>
      </goals>
      <configuration>
        <rules>
          <scriptRule>
            <script>
              <![CDATA[
                def compatGroup = "你的compat模块groupId"
                def compatArtifact = "你的compat模块artifactId"
                def protobufGroup = "com.google.protobuf"
                def protobufArtifact = "protobuf-java"
                def protobufVersion = "2.5"

                def compatSeen = false
                // 检查运行时依赖的顺序
                for (dep in project.runtimeDependencies) {
                  if (dep.groupId == compatGroup && dep.artifactId == compatArtifact) {
                    compatSeen = true
                  } else if (dep.groupId == protobufGroup && dep.artifactId == protobufArtifact && dep.version == protobufVersion) {
                    if (!compatSeen) {
                      fail("Protobuf兼容模块${compatGroup}:${compatArtifact}必须在官方${protobufGroup}:${protobufArtifact}:${protobufVersion}之前加载，请调整pom中的运行时依赖声明顺序")
                    }
                  }
                }
                // 可选：检查两个依赖是否存在
                if (!project.runtimeDependencies.any { it.groupId == compatGroup && it.artifactId == compatArtifact }) {
                  fail("未检测到Protobuf兼容模块依赖")
                }
                if (!project.runtimeDependencies.any { it.groupId == protobufGroup && it.artifactId == protobufArtifact && it.version == protobufVersion }) {
                  fail("未检测到官方protobuf-java:2.5依赖")
                }
              ]]>
            </script>
            <language>groovy</language>
          </scriptRule>
        </rules>
      </configuration>
    </execution>
  </executions>
  <dependencies>
    <dependency>
      <groupId>org.codehaus.groovy</groupId>
      <artifactId>groovy-all</artifactId>
      <version>3.0.17</version>
      <scope>runtime</scope>
    </dependency>
  </dependencies>
</plugin>

关键说明 #

1. Maven默认按直接依赖的声明顺序排列类路径，所以只要pom里先写compat模块、再写官方protobuf，就能保证顺序；Enforcer规则的作用是防止后续有人误改顺序。
2. 用runtimeDependencies是因为你的compat模块是运行时依赖，确保检查的是运行时类路径的顺序，和实际运行时的加载逻辑一致。
3. 如果涉及传递依赖，可以把脚本中的runtimeDependencies换成dependencyTree（需要额外依赖解析树的组件），但直接依赖场景下，检查声明顺序足够覆盖需求。

内容的提问来源于stack exchange，提问作者Mark VY