Source not found appears in MyEclipse because the Java EE Generic Library you are referencing has no associated source code, such as:
Here's a solution to the problem:
Step one: To download apache-tomcat-7.0.57-src.zip source files, Baidu or go to apache-tomcat official website to download
Step two: The source code is associated. There are two ways of doing this:
Method 1: You can click Attach source directly on the source not found page, select the source file that you downloaded in step one, OK. Such as:
Method 2: Click the right mouse button in project engineering, select Properties ..., select Java Build Path->libraries in the Pop-up dialog box, select the source attachment below the package that needs to be added. In the pop-up dialog box, select the appropriate source code file (clip) by the top way, and then OK. :
Solution to source not found problem in MyEclipse