单模块Maven项目JaCoCo报告未在Maven Site展示，却生成空聚合报告

项目背景 #

• 基于Java 11的单模块Jar库项目，继承自通用父pom，父子项目均无子模块
• 父pom包含<pluginManagement>节点，父子pom均配置JaCoCo，子pom配置覆盖父pom
• 父pom的<reporting>节点无JaCoCo配置

需求 #

在Maven Site页面的「项目报告」中生成JaCoCo覆盖率报告的入口链接

问题现象 #

• 执行mvn clean test site后，完整的单元测试JaCoCo报告已生成在target/site/jacoco目录，但Site页面未显示该报告的链接
• Site页面反而始终显示「Jacoco Aggregate」链接，点击后为空报告，target/site/jacoco-aggregate仅包含少量基础文件（含index.html）
• JaCoCo数据文件jacoco.exec生成在正确路径target/code-coverage/data/

已尝试操作 #

• 查阅官方文档，确认单模块项目中JaCoCo报告应自动加入Site页面，无需额外配置
• 将父pom中JaCoCo插件从<build><pluginManagement>移至<build>节点，避免被误识别为多模块项目
• 注释插件的自定义配置，仅保留prepare-agent和report核心目标，问题依旧

控制台警告（正常项目也会出现） #

[INFO] Skipping JaCoCo execution due to missing execution data file.

父pom配置 #

<build>
  <pluginManagement>
    ...
  </pluginManagement>
  <plugins>
    <plugin>
      <groupId>org.jacoco</groupId>
      <artifactId>jacoco-maven-plugin</artifactId>
      <version>0.8.11</version>
      <executions>
        <execution>
          <id>default-prepare-agent</id>
          <goals>
            <goal>prepare-agent</goal>
          </goals>
          <configuration>
            <skip>${jacoco.skip}</skip>
            <propertyName>argline.jacoco</propertyName>
            <destFile>${project.build.directory}/code-coverage/data/jacoco.exec</destFile>
            <includes>
              <include>${jacoco.include}</include>
            </includes>
            <excludes>
              <exclude>${jacoco.exclude}</exclude>
            </excludes>
          </configuration>
        </execution>
        <execution>
          <id>default-report</id>
          <goals>
            <goal>report</goal>
          </goals>
          <phase>test</phase>
          <configuration>
            <skip>${jacoco.skip}</skip>
            <dataFile>${project.build.directory}/code-coverage/data/jacoco.exec</dataFile>
            <outputDirectory>${project.build.directory}/code-coverage/report</outputDirectory>
            <includes>
              <include>${jacoco.include}</include>
            </includes>
              <excludes>
                <exclude>${jacoco.exclude}</exclude>
              </excludes>
          </configuration>
        </execution>
      </executions>
    </plugin>
    ...
  </plugins>
</build>

项目pom配置 #

<reporting>
  <plugins>
    <plugin>
      <groupId>org.jacoco</groupId>
      <artifactId>jacoco-maven-plugin</artifactId>
      <version>0.8.11</version>
      <configuration>
        <outputDirectory>${project.build.directory}/site/jacoco</outputDirectory>
      </configuration>
    </plugin>
  ...
  </plugins>
</reporting>
<build>
  <plugins>
    <plugin>
      <groupId>org.jacoco</groupId>
      <artifactId>jacoco-maven-plugin</artifactId>
      <version>${version.jacoco}</version>
      <executions>
        <!-- first execution : for preparing JaCoCo runtime agent -->
        <execution>
          <id>default-prepare-agent</id>
          <goals>
            <goal>prepare-agent</goal>
          </goals>
        </execution>
        <!-- second execution : for creating code coverage reports -->
        <execution>
          <id>default-report</id>
          <goals>
            <goal>report</goal>
          </goals>
          <phase>test</phase>
          <configuration>
            <skip>${jacoco.skip}</skip>
            <dataFile>${project.build.directory}/code-coverage/data/jacoco.exec</dataFile>
            <outputDirectory>${project.build.outputDirectory}/site/jacoco</outputDirectory>
            <includes>
              <include>${jacoco.include}</include>
            </includes>
            <excludes>
              <exclude>${jacoco.exclude}</exclude>
            </excludes>
          </configuration>
        </execution>
      </executions>
    </plugin>
    ...
</build>

解决方案 #

问题根源 #

1. 父pom中report目标的输出目录未指向Site报告的标准路径，导致Site插件无法识别报告位置
2. 子pom重复配置JaCoCo插件，且<reporting>节点未明确指定报告目标，触发了JaCoCo的聚合报告逻辑（针对多模块设计）

修复步骤 #

1. 调整父pom的JaCoCo配置

将report目标的输出目录改为Site报告的标准路径，同时移除phase绑定，让其自动关联Site生命周期：

<build>
  <pluginManagement>
    ...
  </pluginManagement>
  <plugins>
    <plugin>
      <groupId>org.jacoco</groupId>
      <artifactId>jacoco-maven-plugin</artifactId>
      <version>0.8.11</version>
      <executions>
        <execution>
          <id>default-prepare-agent</id>
          <goals>
            <goal>prepare-agent</goal>
          </goals>
          <configuration>
            <skip>${jacoco.skip}</skip>
            <propertyName>argline.jacoco</propertyName>
            <destFile>${project.build.directory}/code-coverage/data/jacoco.exec</destFile>
            <includes>
              <include>${jacoco.include}</include>
            </includes>
            <excludes>
              <exclude>${jacoco.exclude}</exclude>
            </excludes>
          </configuration>
        </execution>
        <execution>
          <id>default-report</id>
          <goals>
            <goal>report</goal>
          </goals>
          <!-- 移除phase配置，让report目标自动绑定到site生命周期 -->
          <configuration>
            <skip>${jacoco.skip}</skip>
            <dataFile>${project.build.directory}/code-coverage/data/jacoco.exec</dataFile>
            <!-- 修改为Site报告的标准目录 -->
            <outputDirectory>${project.reporting.outputDirectory}/jacoco</outputDirectory>
            <includes>
              <include>${jacoco.include}</include>
            </includes>
            <excludes>
              <exclude>${jacoco.exclude}</exclude>
            </excludes>
          </configuration>
        </execution>
      </executions>
    </plugin>
    ...
  </plugins>
</build>

2. 简化子pom配置

移除<build>中重复的JaCoCo插件配置（直接继承父pom），并在<reporting>中明确指定报告目标，避免触发聚合报告：

<reporting>
  <plugins>
    <plugin>
      <groupId>org.jacoco</groupId>
      <artifactId>jacoco-maven-plugin</artifactId>
      <version>0.8.11</version>
      <!-- 明确指定仅生成基础报告，排除聚合报告 -->
      <reportSets>
        <reportSet>
          <reports>
            <report>report</report>
          </reports>
        </reportSet>
      </reportSets>
    </plugin>
    ...
  </plugins>
</reporting>
<!-- 移除build中的JaCoCo插件重复配置 -->

3. 验证结果

执行mvn clean test site，此时Site页面的「项目报告」中会显示「JaCoCo」链接，指向target/site/jacoco下的完整覆盖率报告，「Jacoco Aggregate」链接会自动消失。

额外说明 #

• 控制台的Skipping JaCoCo execution due to missing execution data file警告是Site生命周期中部分JaCoCo目标的正常检查逻辑，只要jacoco.exec生成正常且报告能显示，该警告可忽略。

内容的提问来源于stack exchange，提问作者dan