this plugin requires plugin Editor Library to be installed.
The plugin Editor Library is requested in version >= 2.10.1.10.2 (release version 2) but only 3.46.1.22.43 (of release version different from 2) was found.
The following plugin is affected: Struts2 Support
Now i have resolved another plugin for Struts 2 support. This plugin is called Netbeans Struts2 Plug-in and its a re-pack for the plugin i was trying to install. Though this plugin in not certified but it is working good. The developers have tested it on netbeans 7.4 but i'm using it not netbeans8 and i have not suffered any issues.
I have found another way, that is using maven. That is also a good way but i would not recommend it if you have slow internet connection.