Maven 编译器插件总是将一组源检测为“过时" [英] Maven compiler plugin always detecting a set of sources as "stale"
问题描述
已修复:这是 maven-compiler-plugin 3.1 中的已知错误
FIXED: this is a known bug in maven-compiler-plugin 3.1
我正在将 1000 多个 java-sources 项目的基于 ant 的构建转换为 maven.到目前为止一切顺利，但每次启动 mvn compile 它都会重新编译所有内容(而不是重用旧类)
I am converting an ant-based build of a 1000+ java-sources project to maven. So far so good, but every time launch mvn compile it recompiles everything (instead of reusing old classes)
使用 mvn -X compile 报告
[DEBUG] Stale source detected: /project_path/src/main/java/package_path/AFile1.java
[DEBUG] Stale source detected: /project_path/src/main/java/package_path/AFile2.java
...
(仅适用于某个包中的文件，它可能未从其余代码中引用；不是我的来源，我只是想对构建进行 mavenize)
(only for files in a certain package, which is possibly unreferenced from the rest of the code; not my sources, I am just trying to mavenize the build)
编译不会失败，更新时间戳的类正在生成
Compilation does not fail, and classes with updated timestamps are being generated at
/project_path/target/classes/package_path/AFile1.class
/project_path/target/classes/package_path/AFile2.class
...
但是，在查看时间戳时，java文件自昨天以来没有变化，类文件是最新的.为什么这些来源被确定为陈旧的?我该如何调试这个问题?
However, when looking at timestamps, the java files have not changed since yesterday, and the class files are current. Why are these sources determined to be stale? How can I debug this issue?.
即使没有发生任何更改，也必须重新编译 1k+ 文件，这很麻烦...
It is a drag to have to recompile 1k+ files even when no changes have occurred...
示例输出:
$ mvn clean compile
[INFO] Scanning for projects...
[INFO]
[INFO] ------------------------------------------------------------------------
[INFO] Building MyProject 1.9.0-SNAPSHOT
[INFO] ------------------------------------------------------------------------
[WARNING] The POM for net.sourceforge:jffmpeg:jar:1.1.0 is missing, no dependency information available
[INFO]
[INFO] --- maven-clean-plugin:2.4.1:clean (default-clean) @ my-project ---
[INFO] Deleting /project_path/target
[INFO]
[INFO] --- maven-resources-plugin:2.5:resources (default-resources) @ my-project ---
[debug] execute contextualize
[INFO] Using 'UTF-8' encoding to copy filtered resources.
[INFO] skip non existing resourceDirectory /project_path/src/main/resources
[INFO]
[INFO] --- maven-compiler-plugin:3.1:compile (default-compile) @ my-project ---
[INFO] Changes detected - recompiling the module!
[INFO] Compiling 1162 source files to project_path/target/classes
....
[INFO] ------------------------------------------------------------------------
[INFO] BUILD SUCCESS
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 11.215s
[INFO] Finished at: Tue Jul 30 12:42:25 CEST 2013
[INFO] Final Memory: 25M/429M
[INFO] ------------------------------------------------------------------------
$ mvn compile
[INFO] Scanning for projects...
[INFO]
[INFO] ------------------------------------------------------------------------
[INFO] Building MyProject 1.9.0-SNAPSHOT
[INFO] ------------------------------------------------------------------------
[WARNING] The POM for net.sourceforge:jffmpeg:jar:1.1.0 is missing, no dependency information available
[INFO]
[INFO] --- maven-resources-plugin:2.5:resources (default-resources) @ my-project ---
[debug] execute contextualize
[INFO] Using 'UTF-8' encoding to copy filtered resources.
[INFO] skip non existing resourceDirectory /project_path/src/main/resources
[INFO]
[INFO] --- maven-compiler-plugin:3.1:compile (default-compile) @ my-project ---
[INFO] Changes detected - recompiling the module!
[INFO] Compiling 1162 source files to /project_path/target/classes
...
[INFO] ------------------------------------------------------------------------
[INFO] BUILD SUCCESS
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 12.140s
[INFO] Finished at: Tue Jul 30 12:42:44 CEST 2013
[INFO] Final Memory: 22M/379M
[INFO] ------------------------------------------------------------------------
推荐答案
这是 maven-compiler-plugin 3.1 中的一个已知问题.它正在 https://issues.apache.org/jira/browse/MCOMPILER-209 中被跟踪(useIncrementalCompilation 标志已损坏).
This is a known problem in maven-compiler-plugin 3.1. It is being tracked in https://issues.apache.org/jira/browse/MCOMPILER-209 (the useIncrementalCompilation flag is broken).
该问题与另一个 3.1 错误无关，https://issues.apache.org/jira/browse/MCOMPILER-205(其中不产生 .class 输出的文件总是被标记为 'stale').
The problem is unrelated to another 3.1 bug, https://issues.apache.org/jira/browse/MCOMPILER-205 (where files that do not produce .class outputs are always flagged as 'stale').
进一步测试后，回到 3.0 并没有真正解决问题(它只在下一次 mvn clean compile 之前有效.然而，正如 Michael Lemke 在评论中建议的那样，标记 useIncrementalCompilation 到 false 是一个可行的替代品；现在，每次只重新编译有问题的包(而不是整个代码库).
After testing further, going back to 3.0 did not actually fix the problem (it only works until the next mvn clean compile. However, as Michael Lemke suggests in comments, marking useIncrementalCompilation to false is a workable substitute; now, only the offending package gets recompiled each time (instead of the whole code-base).
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