Solution: The imported racks cannot be encapsulated into a referenced libraries.

About importing Jar packs, Java WEB projects can be in the project's \webroot\web-inf\lib directory, the project's jar bag directly copy into the good, MyEclipse will load the jar package, and generate the only referenced Libraries.

However, when I recently used MyEclipse to do projects, one day suddenly all the projects have no "referenced libraries" This thing, originally imported jar bag with libraries peer, The jar packages that are copied to the Lib directory are not automatically encapsulated in the referenced Library, and if too many jars are imported, the directory structure of the project is very long and ugly, and the internet search is not resolved, and then when I restart MyEclipse, Changed a workspace, there is no such problem, I do not understand why this, but, if someone encounters the same problem, might as well try, before I encountered MyEclipse problems, will also replace workspace, often can solve the problem, So if you change a workspace, you may be able to make the directory structure from the left side of the following figure back to the right side: