Unsupported IClasspathEntry kind=4这个异常会导致项目无法使用spring ide启动
来自：http://blog.csdn.net/kongqz/article/details/7770765
英文解释如下：
Please see https://bugs.eclipse.org/bugs/show_bug.cgi?id=374332#c14
The problem is caused by the fact that the STS (the Spring
IDE/Eclipse) uses the m2e(clipse) plugin but that eclipse:eclipse has
been probably been run on the project. When m2e encounters a "var"
.classpath entry, it throws this error.
In order to fix this problem, you need to do 2 things:
Make sure that the version of the m2e(clipse) plugin that you're running is at least 1.1.0. The update site is here:
https://repository.sonatype.org/content/repositories/forge-sites/m2e/1.1.0/N/LATEST/Disable the maven nature for the project (via the right-click menu), run mvn eclipse:clean (while your project is
open in STS/eclipse), and then re-enable the maven nature.
中文解释就是
问题是因为使用spring ide使用了m2eclipse 插件，但是这个插件的使用前提是不允许命令 mvn eclipse:eclipse在项目上执行过，如果执行过，就会抛出这个异常。
现阶段修复这个问题需要做两件事
1、保证m2e插件的版本高于 1.1.0，如果没有到站点升级 : https://repository.sonatype.org/content/repositories/forge-sites/m2e/1.1.0/N/LATEST/
2、去掉项目的maven特性，右键菜单就能去除，然后执行 mvn eclipse:clean，并且重新激活 maven 特性