How to debug WAR application inside eclipse?

I have seen many online tutorial explaining how to use eclipse to do remote debug of WAR file.

But what I want to know is how to do the debug inside eclipse just as debugging a JAVA application? I have Tomcat 7 configured in my eclipse as a server. And I have tested it with a sample servlet program successfully meaning I can set breakpoint in the source code and run into it.

My WAR application is built by gradle. I have imported the gradle project into my eclipse and build it ok inside eclipse by running gradle task inside "gradle tasks view". I added the project into the server. However, when I try to use "Debug as > Debug on Server", it fails and the breakpoint is not get hit. Anyone could share the experience to debug WAR inside eclipse?

I am a IntelliJ Idea user but I have a generic advice here. What you can do is that you can run your application (war/jar etc) with debug port on and then from eclipse use remote debug (or attached to a process sort of option).

Make sure you have exact copy of the code from which you have created war/jar otherwise lines might mismatch while debugging and will be hard to make sense.

On the "Servers" view, select the right tomcat server overview, then go on the "Modules" tab.

There, you can add the war by clicking on "Add External Web Module...".

Set the war path in the "Document base", and what ever you want on the "Path" field.

Example:
>Document base: "C:\eclipse-workspace\MyProject\war\myWarToDebug.war"
>
>Path: "/myapp"

Start the server in debug mode. Access your app using the url
<yourServerHost>:<serverPort>/<pathSetInModuleTab>.

Note that when reaching the breakpoint, Eclipse may say there is no sources found. Simply go on the server debug configuration and add the project sources in the "Source" tab.

Before debug you must decompile using jd gui for open class file inside war file and save as java project.