API to clear internal browser cache

[minduch]

Describe the bug
There seems to be no way to clear the internal cache of the browser used in Eclipse (new Browser(..)). In Windows (7-10), when MSIE11 is used, the best way to clear the cache is to execute the process:

          Process p=Runtime.getRuntime().exec(new String [] {
              "RunDll32.exe",
              "InetCpl.cpl",
              "ClearMyTracksByProcess",
              "8"
          });
          p.waitFor();

but when MSEdge is used in some mode in Windows 11 (I don't know if it's MSIE11 compatible mode or just normal Edge mode), then there is NO way to actually clear the cache.

For all these operations, you must refresh the SWT Browser instance with a reload once the cache has been cleared (of course), or do this prior to creating the Browser instance.

From the browser component, you can e.g. press F12 to open the DevTools and from there clear the cache. But for some reason, that is not the cache being used. Even if clearing the cache in a stand-alone instance of MS Edge and clearing the cache (Shift+Ctrl+Del > Clear now and also [Clear browsing data for Internet Explorer mode](edge://settings/clearBrowserData#)) does not help. Trying other methods to locate directory such as %LOCALAPPDATA%\Microsoft\Edge\User Data\Default\Cache\Cache_Data and deleting all files does not work either (the directory can be queried using e.g. the command reg query HKEY_CURRENT_USER\Software\Microsoft\Edge\Profiles /s /f Path, replying e.g. Path REG_SZ
C:\Users\USERNAME\AppData\Local\Microsoft\Edge\User Data\Default).

Other locations such as %LOCALAPPDATA%\Microsoft\Packages\Microsoft.MicrosoftEdge.Stable_8wekyb3d8bbwe where 8wekyb3d8bbwe could be different for every machine and Windows update, e.g. in my case

Microsoft.MicrosoftEdge.Stable_8wekyb3d8bbwe
Microsoft.MicrosoftEdgeDevToolsClient_8wekyb3d8bbwe
Microsoft.MicrosoftEdge_8wekyb3d8bbwe

under wich directory the subdirectory AC\Temp could be found and certain posts on the internet suggests to delete files or directories beginning with #! or something like it (this could be related to older versions os MS Edge).

The problem is that we have an embedded Jetty instance running on localhost serving a port with HTTP. Changing files on for the webserver, e.g. JavaScript files are never reflected in the internal Eclipse Browser component when created using new Browser(parent...). Jetty is configured to use Etag (weak ETags) and we even add Last-Modified timestamp, but nothing helps. We use the SWT Browser component to load content from http://localhost:port/....

If MSEdge (or any other browser - without clearing the cache) is used to load the SAME modified file (e.g. JavaScript), then it shows the correct content. BUT NOT the internal SWT Browser component! So one really starts to wonder what goes on under the hood (the Eclipse File System? We also try to refresh that one in the Workspace)...

It is imperative to clear this cache, whether done using an API or that we do it programmatically in order for our code to work.

Please advise best way to do so. I can't find any documentation that actually works to clear the MSEdge cache used for Eclipse new Browser(..) instances.

Environment:

1. Select the platform(s) on which the behavior is seen:

• • All OS
• • Windows
• • Linux
• • macOS

2. Additional OS info (e.g. OS version, Linux Desktop, etc)
   Windows 11. We do use Eclipse with "Wild Web Developer" if this would perhaps interfere?

3. JRE/JDK version
   Java 17 or 18, any flavor (Temurin, etc).

Version since
Eclipse 4.24, currently on 4.25 M1.

Workaround (or) Additional context
If anybody knows how to do this, please comment! Thank you very much.

[Phillipus]

When starting Eclipse with the following setting, and using the internal browser

-Dorg.eclipse.swt.browser.DefaultType=edge

a folder is created at C:\Users\USERNAME\AppData\Local\Eclipse\EBWebView - is that the cache?

[minduch]

I'm not really sure what you mean @Phillipus.

In Windows versions prior to 11, you can specify the browser to MS Edge by using -Dorg.eclipse.swt.browser.DefaultType=edge as you stated, but this doesn't change anything as there is no MS IE 11 under Windows 11, i.e. it's always MS Edge.

The problem is that the internal SWT Browser component is not loading changed files always, regardless of ETag or Last-Modified in HTTP headers. So we need to clear the cache sometimes to make sure the browser component really loads the updated files. For MS IE 11 we have such processing in place: calling the process RunDll32.exe InetCpl.cpl ClearMyTracksByProcess 8. But for MS Edge we don't know how to do it!

I do not know what the directory C:\Users\USERNAME\AppData\Local\Eclipse\EBWebView is: for me, it contains a subdirectory ico_dir with a few .icofiles, that's all.

[Phillipus]

For me on Windows 11, when I use -Dorg.eclipse.swt.browser.DefaultType=edge and launch Eclipse and use the internal browser in Eclipse I get a whole directory full of cached stuff in C:\Users\USERNAME\AppData\Local\Eclipse\EBWebView - I just thought it might offer a clue as to where stuff was being cached. If not, ignore it.

[minduch]

OK @Phillipus, but not for me.

I launch an Eclipse product instance from inside Eclipse in Run or Debug mode, and it is in this (second) instance of Eclipse that the problems occurs in. That is the one creating the SWT Browser component failing. This I actually forgot to mention - it is quite important. However, the cache needs to be cleared in all cases, we had to do so for many years with MSIE11 and we must now do so for MSEdge, so the problem remains...

[Phillipus]

I launch an Eclipse product instance from inside Eclipse in Run or Debug mode

So do I. The product name is "Archi" and when launched with -Dorg.eclipse.swt.browser.DefaultType=edge a folder is created with the product name - C:\Users\USERNAME\AppData\Local\Archi\EBWebView. In this folder are loads of cache type files and settings.

as there is no MS IE 11 under Windows 11, i.e. it's always MS Edge.

That's not really the case, or maybe it's Edge that looks like IE 11. It seems to be a browser that looks and behaves like IE11 when used in Eclipse or an RCP app. Because when specifying -Dorg.eclipse.swt.browser.DefaultType=edge you'll see a different internal browser.

[niraj-modi]

@nnemkin Any idea on how to clear the cache for embedded Edge browser ?

[nnemkin]

@niraj-modi

There is the ClearBrowsingData method, a recent addition to the WebView2 API. Nowhere to expose it though.

A simpler option is to delete the data folder, which is by default located in %LOCALAPPDATA%\<APP_NAME>\EBWebView. Deleting will likely require the app to be shut down.

WebView should respect ETag and Last-Modified. If it doesn't, something is seriously broken.

[minduch]

Thanks @nnemkin.

You are so right: the directory to clear would be %LOCALAPPDATA%\<APP_NAME>\EBWebView\Default\Cache\Cache_Data. Clearing that directory does the trick (e.g. APPNAME = "Eclipse" in our case when launching from Eclipse in Debug/Run mode, and iiziGo when packaged into our product with its launcher). But then again, someone could drop in the plugins into Eclipse from e.g. the Eclipse Market Place into another product, then it could be another value than Eclipse.

What is the best API to use to get the APP_NAME, except parsing System.getProperty(..) values? Is there any "Workbench" API to do so (that could perhaps also apply to RCP's also embedding WebView)?` I can't seem to find some simple API to use, but there probably is one.

I even thought this could work (once MSEdge Browser component is ready):

browser.evaluate("caches.keys().then((keyList) => Promise.all(keyList.map((key) => caches.delete(key))))");

In regards to ETag and Last-Modified, we've seen that WebView doesn't even issue requests to the embedded Jetty sometimes, it just grabs it from the cache directly - don't ask me why (sounds crazy, I know)! That's why we need to clear the cache. And this has been the case for a looong time, even with MSIE in early Eclipse versions since 3.7.

[nnemkin]

The API for APP_NAME is the static method Display.getAppName().

If a resource has a far future expiration date, then the server won't try to re-fetch it. With DevTools you should be able to figure out why exactly the resource is loaded from a cache.

[minduch]

Thanks a lot @nnemkin!

About the resource dates, I know. But with only ETag, it shouldn't do that, and not the Weak ones used in Jetty, now that we use MS Edge. We have similar problems in very different environments such as Cordova WebView on iOS or Android -- dates OK too. We need to clear the cache there too between program versions, and they use the file: protocol or alike, no web server. We have tried to figure this out for years but given up on it... Nothing can really explain it.

[sratz]

Note: With #1548 the edge data directory is configurable using org.eclipse.swt.internal.win32.Edge.userDataFolder via Display#setData().

And - when SWT is used in Eclipse - this is set to <workspace>\.metadata\.plugins\org.eclipse.swt\EBWebView\ with eclipse-platform/eclipse.platform.ui#2434 + eclipse-platform/eclipse.platform.ui#2469.

An official Browser#clearData(...) API would have to be provided for all Browser implementations. Not sure if that is feasible.