java - 为什么 Maven enforcer 会限制为 Java 1.6？

Question

当我在我的项目上运行 mvn test 时，出现 JDK 版本错误。

这是输出:

[INFO] Scanning for projects...
[INFO] 
[INFO] -----------------------< net.rorynolan:Detrendr >-----------------------
[INFO] Building Detrendr 0.0.0.9003-SNAPSHOT
[INFO] --------------------------------[ jar ]---------------------------------
[INFO] 
[INFO] --- maven-enforcer-plugin:1.3.1:enforce (enforce-rules) @ Detrendr ---
[INFO] Adding ignorable dependency: null:jcodings:null
[INFO]   Adding ignore: org/jcodings/*
[INFO] Adding ignorable dependency: null:jnr-constants:null
[INFO]   Adding ignore: com/kenai/constantine/*
...
[INFO] Adding ignorable dependency: com.sun:tools:null
[INFO]   Adding ignore: *
[INFO] Restricted to JDK 1.6 yet org.junit.platform:junit-platform-commons:jar:1.3.1:test contains org/junit/platform/commons/JUnitException.class targeted to JDK 1.8
[INFO] Restricted to JDK 1.6 yet org.junit.jupiter:junit-jupiter-api:jar:5.3.1:test contains org/junit/jupiter/api/AssertArrayEquals.class targeted to JDK 1.8
[INFO] Restricted to JDK 1.6 yet org.junit.jupiter:junit-jupiter-engine:jar:5.3.1:test contains org/junit/jupiter/engine/Constants.class targeted to JDK 1.8
[INFO] Restricted to JDK 1.6 yet org.junit.platform:junit-platform-engine:jar:1.3.1:test contains org/junit/platform/engine/TestDescriptor.class targeted to JDK 1.8
[WARNING] Rule 5: org.apache.maven.plugins.enforcer.EnforceBytecodeVersion failed with message:
Found Banned Dependency: org.junit.platform:junit-platform-commons:jar:1.3.1
Found Banned Dependency: org.junit.jupiter:junit-jupiter-api:jar:5.3.1
Found Banned Dependency: org.junit.jupiter:junit-jupiter-engine:jar:5.3.1
Found Banned Dependency: org.junit.platform:junit-platform-engine:jar:1.3.1
Use 'mvn dependency:tree' to locate the source of the banned dependencies.
[INFO] ------------------------------------------------------------------------
...
[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/MojoExecutionException

我的 pom.xml 位于 https://github.com/rorynolan/ij_detrendr/blob/master/pom.xml .

mvn help:effective-pom中有线索

我能看到的地方

<plugin>
  <artifactId>maven-enforcer-plugin</artifactId>
  <version>1.3.1</version>
  ...
  <rules>
    ...  
    <enforceBytecodeVersion>
      <maxJdkVersion>1.6</maxJdkVersion>
        <excludes>
          <exclude>com.headius:invokebinder</exclude>
          <exclude>com.sun:tools</exclude>
        </excludes>
      </enforceBytecodeVersion>
      <banCircularDependencies />
    </rules>
  </configuration>
</plugin>

但这就是我所拥有的。我尝试将 maven enforcer 插件显式添加到我自己的 pom.xml 但无济于事。

Answer 1

您的项目 pom parent 是:net.imagej:pom-imagej:13.2.0这是org.scijava:pom-scijava:8.4.0的 parent 其中包含以下与 Java 版本相关的摘录:

<scijava.jvm.version>1.6</scijava.jvm.version>

<plugin>
  <artifactId>maven-compiler-plugin</artifactId>
  <version>3.1</version>
  <!-- Require the Java 6 platform. -->
  <configuration>
    <source>${scijava.jvm.version}</source>
    <target>${scijava.jvm.version}</target>
  </configuration>
</plugin>

<plugin>
  <artifactId>maven-enforcer-plugin</artifactId>
  ...
  <enforceBytecodeVersion>
    <maxJdkVersion>${scijava.jvm.version}</maxJdkVersion>
    ...
  </enforceBytecodeVersion>
</plugin>  

因此，执行者规则及其对 Java 1.6 的坚持是通过您的项目的父系继承的。

Java 1.6 的这一限制与编译为 Java 1.8 的 JUnit5 库冲突。

您可以也许可以在您自己的 POM 中覆盖 enforcer 插件(参见 the Maven docs 中对 combine.self="override" 的引用)，但事实上您的模块的grandparent (org.scijava:pom-scijava:8.4.0) 明确声明它希望在 Java 1.6 上运行，强烈建议任何此类覆盖都会导致问题。

我认为更明智的做法是以下之一:

• 从 Junit5 降级到与 Java 1.6 兼容的 Junit4 版本
• 将你的父版本(net.imagej:pom-imagej:13.2.0)升级到与 Java 8 兼容的版本，注意:net.imagej:pom-imagej :13.2.0 已有 3 年历史，因此您可能会发现升级到最新版本后此问题就会消失。