How to fix Eclipse validation error “No grammar constraints detected for the document”?

Question

Eclipse 3.5.2 is throwing an XML schema warning message:

No grammar constraints (DTD or XML schema) detected for the document.

The applica

Answer 1

It can be because of your proxy settings. See this and this. You can try attaching javadoc by URL to a library without it. If it is okay in your browser, but not in your editor, then it's a connection problem. I solved the same problem by asking the admin about the proxy settings. Although all other applications did work, eclipse didn't, so I had to enter the config "manually". It would be great if developers added a button "check connection"...