在使用Jenkins自動構建Java專案時，出現以下的錯誤。錯誤日誌如下： 

+ /opt/maven/apache-maven-3.5.4/bin/mvn clean package -U -e -B -Dmaven.test.skip=true
[INFO] Error stacktraces are turned on.
[INFO] Scanning for projects...
[INFO] ------------------------------------------------------------------------
[INFO] BUILD FAILURE
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 0.096 s
[INFO] Finished at: 2018-10-17T19:09:42+08:00
[INFO] ------------------------------------------------------------------------
[ERROR] The goal you specified requires a project to execute but there is no POM in this directory (/root/.jenkins/workspace). Please verify you invoked Maven from the correct directory. -> [Help 1]
org.apache.maven.lifecycle.MissingProjectException: The goal you specified requires a project to execute but there is no POM in this directory (/root/.jenkins/workspace/). Please verify you invoked Maven from the correct directory.
    at org.apache.maven.lifecycle.internal.LifecycleStarter.execute (LifecycleStarter.java:85)
    at org.apache.maven.DefaultMaven.doExecute (DefaultMaven.java:305)
    at org.apache.maven.DefaultMaven.doExecute (DefaultMaven.java:192)
    at org.apache.maven.DefaultMaven.execute (DefaultMaven.java:105)
    at org.apache.maven.cli.MavenCli.execute (MavenCli.java:954)
    at org.apache.maven.cli.MavenCli.doMain (MavenCli.java:288)
    at org.apache.maven.cli.MavenCli.main (MavenCli.java:192)
    at sun.reflect.NativeMethodAccessorImpl.invoke0 (Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke (NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke (DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke (Method.java:498)
    at org.codehaus.plexus.classworlds.launcher.Launcher.launchEnhanced (Launcher.java:289)
    at org.codehaus.plexus.classworlds.launcher.Launcher.launch (Launcher.java:229)
    at org.codehaus.plexus.classworlds.launcher.Launcher.mainWithExitCode (Launcher.java:415)
    at org.codehaus.plexus.classworlds.launcher.Launcher.main (Launcher.java:356)
[ERROR] 
[ERROR] Re-run Maven using the -X switch to enable full debug logging.
[ERROR] 
[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/MissingProjectException
Build step '執行 shell' marked build as failure
SSH: Current build result is [FAILURE], not going to run.
Finished: FAILURE

去網上搜了一遍發現各種解決辦法，但是沒有什麼作用。仔細分析了下文章中日誌中的意思無非就是找不到POM檔案。我去Jenkins的workspace裡去檢視發現下面多了一級子目錄，也就是說pom檔案不在workspace中的工程目錄中。所以就會導致maven找不到pom檔案。所以，我在構建的時候直接在構建前加一個進入工程實際目錄的動作，在進行構建，就不會有問題了。

如下圖：

就能直接構建成功了。這是最簡便的方式。

事後分析了下造成這種情況：大概是拉取程式碼分支，程式碼分支裹了一層目錄，所以拉過來就多了一級目錄。