有时，即使重新导入Maven项目也无法工作。在eclipse中正确地更新项目并不是一个确定的过程。 我发现的唯一100%安全的程序是:

Disable Maven Nature, run mvn eclipse:clean, restart, cross your fingers and Pray 3 times. If this won't work, delete the project, run mvn eclipse:clean, re-import refresh, pray and use the force. If this still doesn't work, restart Eclipse, or even better your computer. While waiting for the reboot, you can make a random donation to fix your Karma. Repeat step 2 and don't forget to pray and control your anger. Anger leads to hate. Hate leads to suffering. Try all the other answers posted in this thread. You might need to try them all for 3 times at least before giving up. Format your Computer, re-install Eclipse and Maven. No need to pray anymore, all gods hate you anyway Delete your git project, burn the physical drive that stored the remote repository, and write your project from scratch. Find a time machine, travel to the past and convince yourself to follow another, non-programming career or at least to avoid Java

我无法让mvn eclipse:clean等与开普勒一起工作。

然而，我改变了创建和扩展变量，只使用eclipse类路径中的外部jar。这反映在我的.classpath中没有var。

这纠正了问题。我更新了Maven。

这个问题(https://bugs.eclipse.org/394042)在m2e 1.5.0中得到修复，该版本可用于Eclipse Kepler和Luna:

http://download.eclipse.org/technology/m2e/releases/1.5

如果你也使用m2e-wtp，你还需要安装m2e-wtp 1.1.0:

http://download.eclipse.org/m2e-wtp/releases/luna/1.1

我使用Eclipse 4.3.2 (Kepler)和M2E 1.4。X和摸索了好几次这个问题!

在我的情况下，“mvn eclipse:eclipse”命令还生成Checkstyle, PMD和Findbugs配置，所以“mvn eclipse:clean”对我没有帮助，因为它会再次删除所有这些配置文件。

对我来说，最好的解决办法就是删除所有。”类路径”文件:

find . -name ".classpath" -delete

然后将项目导入eclipse。

I tried Marco's steps but no luck. Instead if you just get the latest m2e plugin from the link he provides and one by one right click on each project -> Maven -> Update Dependencies the error still pops up but the issue is resolved. That is to say the warnings disappear in the Markers view. I encountered this issue after importing some projects into SpringSource Tool Suite (STS). When I returned to my Eclipse Juno installation the warnings were displaying. Seeing that I had m2e 1.1 already installed I tried Marco's steps to no avail. Getting the latest version fixed it however.

这个问题已经在m2e 1.5.0中修复，该版本可用于Eclipse Kepler(4.3)和Luna (4.4)

请参阅https://bugs.eclipse.org/bugs/show_bug.cgi?id=374332#c14

这个问题是由于STS (Spring IDE/Eclipse)，以及Eclipse和其他基于Eclipse的IDE使用m2e(clipse)插件，但是Eclipse: Eclipse可能已经在项目上运行了。当m2e遇到"var" .classpath条目时，它抛出此错误。

更新站点指定在以下url: http://eclipse.org/m2e/m2e-downloads.html

如果你因为任何原因不能使用m2e 1.5.0，那么:

Disable the maven nature for the project (via the right-click menu) Run mvn eclipse:clean (while your project is open in STS/eclipse). Depending on the timing, you might need to do a refresh or two on the project before re-enabling the maven nature. You should be able to see that your project has lost it's Maven nature. (The eclipse:clean goal just deletes the .project, .classpath and .settings/ files/directories. You can also just remove those files (again while the project is open) instead of running mvn eclipse:clean.) Re-enable the maven nature. (Most of the time, this can be done by right-clicking on the project in question in the package explorer pane, and then choosing 'Configure'-> 'Convert to Maven Project')