今日在做maven項目部署時出現了這樣一個錯誤，開始時不得要領總以爲某個plugin找不到了或是版本不對：
於是重裝maven。。。
mvn -install -e
問題依舊
後來查看%MAVEN_HOME%/conf/settings.xml時發現：
<localRepository>E:/local_repo/repository</localRepository>中指向的目錄出了問題（原來目錄放在.m2中的後來給挪了一下位置，也許是覆蓋掉的吧，誰知道？），
於是將其改爲%MAVEN_HOME%/.m2/repository
問題解決！
總結一下：
1. 確保正確安裝maven。（通常跳過此步。。。）。
2. 確保相關的環境變量存在（M2_HOME、 MAVEN_HOME等）。
3. 確保settings.xml中的庫目錄指向正確的地址。
4. 如果還是不行就完全刪掉maven，然後參照第1條。
相關信息：
+ Error stacktraces are turned on.
[INFO] Scanning for projects...
[INFO] ------------------------------------------------------------------------
[INFO] Building dongao Bussiness Operation Support System
[INFO] task-segment: [install]
[INFO] ------------------------------------------------------------------------
[INFO] ------------------------------------------------------------------------
[ERROR] BUILD ERROR
[INFO] ------------------------------------------------------------------------
[INFO] The plugin 'org.apache.maven.plugins:maven-resources-plugin' does not exist or no valid version could be found
[INFO] ------------------------------------------------------------------------
[INFO] Trace
org.apache.maven.lifecycle.LifecycleExecutionException: The plugin 'org.apache.maven.plugins:maven-resources-plugin' does not exist or no valid version could be found
at org.apache.maven.lifecycle.DefaultLifecycleExecutor.verifyPlugin(DefaultLifecycleExecutor.Java:1286)
at org.apache.maven.lifecycle.DefaultLifecycleExecutor.getMojoDescriptor(DefaultLifecycleExecutor.java:1522)
at org.apache.maven.lifecycle.DefaultLifecycleExecutor.bindLifecycleForPackaging(DefaultLifecycleExecutor.java:1016)
at org.apache.maven.lifecycle.DefaultLifecycleExecutor.constructLifecycleMappings(DefaultLifecycleExecutor.java:980)
at org.apache.maven.lifecycle.DefaultLifecycleExecutor.executeGoal(DefaultLifecycleExecutor.java:458)
at org.apache.maven.lifecycle.DefaultLifecycleExecutor.executeGoalAndHandleFailures(DefaultLifecycleExecutor.java:311)
at org.apache.maven.lifecycle.DefaultLifecycleExecutor.executeTaskSegments(DefaultLifecycleExecutor.java:278)
at org.apache.maven.lifecycle.DefaultLifecycleExecutor.execute(DefaultLifecycleExecutor.java:143)
at org.apache.maven.DefaultMaven.doExecute(DefaultMaven.java:333)
at org.apache.maven.DefaultMaven.execute(DefaultMaven.java:126)
at org.apache.maven.cli.MavenCli.main(MavenCli.java:282)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:585)
at org.codehaus.classworlds.Launcher.launchEnhanced(Launcher.java:315)
at org.codehaus.classworlds.Launcher.launch(Launcher.java:255)
at org.codehaus.classworlds.Launcher.mainWithExitCode(Launcher.java:430)
at org.codehaus.classworlds.Launcher.main(Launcher.java:375)
Caused by: org.apache.maven.plugin.version.PluginVersionNotFoundException: The plugin 'org.apache.maven.plugins:maven-resources-plugin' does not exist or no valid version could
e found
at org.apache.maven.plugin.version.DefaultPluginVersionManager.resolvePluginVersion(DefaultPluginVersionManager.java:229)
at org.apache.maven.plugin.version.DefaultPluginVersionManager.resolvePluginVersion(DefaultPluginVersionManager.java:91)
at org.apache.maven.plugin.DefaultPluginManager.verifyPlugin(DefaultPluginManager.java:167)
at org.apache.maven.lifecycle.DefaultLifecycleExecutor.verifyPlugin(DefaultLifecycleExecutor.java:1257)
... 18 more
[INFO] ------------------------------------------------------------------------
[INFO] Total time: < 1 second
[INFO] Finished at: Tue Mar 10 16:11:26 CST 2009
[INFO] Final Memory: 1M/3M
[INFO] ------------------------------------------------------------------------
爲了方便找錯，通常在使用maven的時候都是離線模式（當然第一次安裝要在線的，除非你又本地庫了）加錯誤輸出，比如：
mvn package -e -o -Dmaven.test.skip=true 將某個工程編譯打包
-e --errors：打開錯誤輸出
-o --offline：離線模式
當然還有：-h 那個就是幫助了。