maven-plugin-plugin：3.6.4：描述​​符失败。：NullPointerException

Question

我的 pom 中有几个不一致的地方，所以我尝试升级所有版本，java 到 11 以及所有插件都是最新的。

现在我的 maven-plugin-plugin 遇到严重问题：

[INFO] --- maven-plugin-plugin:3.6.4:descriptor (default-descriptor) @ latex-maven-plugin ---
[INFO] Using 'UTF-8' encoding to read mojo source files.
[INFO] java-javadoc mojo extractor found 0 mojo descriptor.
[INFO] bsh mojo extractor found 0 mojo descriptor.
[INFO] ant mojo extractor found 0 mojo descriptor.
[INFO] ------------------------------------------------------------------------
[INFO] BUILD FAILURE
[INFO] ------------------------------------------------------------------------
[INFO] Total time:  15.423 s
[INFO] Finished at: 2022-03-03T02:49:06+01:00
[INFO] ------------------------------------------------------------------------
[ERROR] Failed to execute goal org.apache.maven.plugins:maven-site-plugin:3.9.1:site (default-site) on project latex-maven-plugin: failed to get report for org.apache.maven.plugins:maven-jxr-plugin: Failed to execute goal org.apache.maven.plugins:maven-plugin-plugin:3.6.4:descriptor (default-descriptor) on project latex-maven-plugin: Execution default-descriptor of goal org.apache.maven.plugins:maven-plugin-plugin:3.6.4:descriptor failed.: NullPointerException -> [Help 1]

在 https://github.com/Reissner /maven-latex-插件 我推送了最新的工作版本。

如果我在编译器插件中一致地从 java 8 升级到 java 11，但将插件-插件版本保留为原始 3.3，我会获得

[INFO] Applying mojo extractor for language: java-annotations
[INFO] ------------------------------------------------------------------------
[INFO] BUILD FAILURE
[INFO] ------------------------------------------------------------------------
[INFO] Total time:  9.367 s
[INFO] Finished at: 2022-03-04T22:25:03+01:00
[INFO] ------------------------------------------------------------------------
[ERROR] Failed to execute goal org.apache.maven.plugins:maven-plugin-plugin:3.3:descriptor (default-descriptor) on project latex-maven-plugin: Execution default-descriptor of goal org.apache.maven.plugins:maven-plugin-plugin:3.3:descriptor failed.: IllegalArgumentException -> [Help 1]

足够有趣的结果，即使升级mockito 会导致插件-插件出现问题。

另外升级插件插件也没有帮助。 唯一改变的是抛出异常的类型。 所以使用 maven-plugin-plugin 3.6.0 我得到一个空指针异常。

Caused by: java.lang.NullPointerException
    at org.apache.maven.tools.plugin.extractor.annotations.JavaAnnotationsMojoDescriptorExtractor.extractFieldParameterTags (JavaAnnotationsMojoDescriptorExtractor.java:405)
at org.apache.maven.tools.plugin.extractor.annotations.JavaAnnotationsMojoDescriptorExtractor.populateDataFromJavadoc (JavaAnnotationsMojoDescriptorExtractor.java:286)```

As i want a newer version for the plugin I tried hard to find out what's going wrong. 
Here is part of the stacktrace for 3.6.4: 

引起原因：java.lang.NullPointerException 在 org.apache.maven.tools.plugin.extractor.annotations.JavaAnnotationsMojoDescriptorExtractor.extractFieldParameterTags (JavaAnnotationsMojoDescriptorExtractor.java:408) 在 org.apache.maven.tools.plugin.extractor.annotations.JavaAnnotationsMojoDescriptorExtractor.populateDataFromJavadoc （JavaAnnotationsMojoDescriptorExtractor.java:280）

Note that the exceptions now come at a different place. 

I found the source I give below: 

private Map<String, JavaField>extractFieldParameterTags(JavaClass javaClass, Map<String, JavaClass> javaClassesMap) {
  try {
    Map<String, JavaField> rawParams = new TreeMap<>();

    // we have to add the parent fields first, so that they will be overwritten by the local fields if
    // that actually happens...
    JavaClass superClass = javaClass.getSuperJavaClass();

    if (superClass != null) {
      if (superClass.getFields().size() > 0) {
        rawParams = extractFieldParameterTags( superClass, javaClassesMap );
      }
      // maybe sources comes from scan of sources artifact
      superClass = javaClassesMap.get(superClass.getFullyQualifiedName());
      if (superClass != null) {
        rawParams = extractFieldParameterTags(superClass, javaClassesMap);
      }
    } else {
      rawParams = new TreeMap<>();
    }

    for (JavaField field : javaClass.getFields()) {
      rawParams.put(field.getName(), field); // <----- line 408
    }

    return rawParams;
  } catch (NoClassDefFoundError e) {
    getLogger().warn( "Failed extracting parameters from " + javaClass );
    throw e;
  }
}

I marked line 408 but cannot find a reason why this shall go wrong. 

Help very much appreciated. 

Answer 1

经过很很长一段时间，我找到了类似于我的问题的答案。
希望读者自己决定这是否值得贴上“答案”的标签。
无论如何，这都是一个警告。

我有一个类

package eu.simuline.m2latex.core;
public enum Target {
    txt() {
        private final String TXT_OUTPUT_FILES = "^T$T\\.txt$";

        // may throw BuildFailureException TEX01
        public void processSource(LatexProcessor latexProcessor,
                                LatexMainDesc desc) throws BuildFailureException {
            latexProcessor.processLatex2txt(desc);
        }

        public String getPatternOutputFiles(Settings settings) {
            return "^T$T\\.txt$";
        }
    }, ...;
...
}

貌似与mojos无关，也在核心包中，
意味着，将软件变成 Maven 插件的功能真的很远。

不管你信不信，去掉这条线

        private final String TXT_OUTPUT_FILES = "^T$T\\.txt$";

就可以解决问题。
我无法弄清楚maven-plugin-plugin执行什么样的分析。