Saturday, January 4, 2025

Re: Digest for google-web-toolkit@googlegroups.com - 12 updates in 3 topics



On Friday, January 3, 2025 at 6:51:34 AM UTC+1 leon.p...@gmail.com wrote:
Hi Craig,

there are 101 hacks to try and keep the browser from caching. 
Problem is that it's a browser implementation on what to cache and what not, and how the browser determines what to cache when seems subject to change.
So for me I prefer to assume it doesn't work.

That's not my experience.
Note that refreshing a page is different from navigating to it (through a link), or going back to it from the navigation history (might also use bfcache), particularly when it comes to subresources.
 
Having said that; except for the last-modified flag my config is the same as yours. I'll add it - thanks!
If it works, it works.

Fwiw,
  • "Pragma: no-cache" never had a specified behavior in responses (it was initially created for requests)
  • Cache-Control is widespread (released in all browsers 11 years ago: https://caniuse.com/mdn-http_headers_cache-control) so you can replace Expires with a max-age directive.
  • I would also use no-cache over no-store: the content of the nocache files don't contain any user-sensitive information so it's ok to store them as long as you revalidate with the server that they're still up-to-date. For that, you need Last-Modified or ETag (preferred) response headers though (you can just use the file's modification date, or derive an ETag from its content). If your server doesn't send those, then I'd look for a better implementation (or work around it by implementing it myself in a filter as suggested here)
    See also https://jakearchibald.com/2016/caching-best-practices/ and https://web.dev/articles/http-cache#flowchart

--
You received this message because you are subscribed to the Google Groups "GWT Users" group.
To unsubscribe from this group and stop receiving emails from it, send an email to google-web-toolkit+unsubscribe@googlegroups.com.
To view this discussion visit https://groups.google.com/d/msgid/google-web-toolkit/7ebc1cda-a62d-4744-81a9-6474763828dcn%40googlegroups.com.
Posted by at No comments:

Thursday, January 2, 2025

Re: Digest for google-web-toolkit@googlegroups.com - 12 updates in 3 topics

Hi Craig,

there are 101 hacks to try and keep the browser from caching. 
Problem is that it's a browser implementation on what to cache and what not, and how the browser determines what to cache when seems subject to change.
So for me I prefer to assume it doesn't work.
Having said that; except for the last-modified flag my config is the same as yours. I'll add it - thanks!
If it works, it works.

rg,

Leon.


Op vrijdag 20 december 2024 om 23:43:33 UTC+1 schreef Craig Mitchell:
> make sure to clear the cache first

Sounds like you haven't setup your caching correctly.  Mine always works perfectly, never have to clear the cache in dev, or when doing a server update.  Here's my Filter:

/**
 * Tell the browser not to cache the .nocache files, by changing the expires time in the HTTP header.
 */
@Component
@Order(1)
public class ServletFilter implements Filter {
private static final String NO_CACHE = ".nocache.js";

@Override
public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {
String requestURI = ((HttpServletRequest)request).getRequestURI();

// Don't cache the nocache
if (requestURI.endsWith(NO_CACHE)) {
setNoCache((HttpServletResponse)response);
}

// Request HTTPS
((HttpServletResponse)response).setHeader("Strict-Transport-Security", "max-age=31536000; includeSubDomains");

chain.doFilter(request, response);
}

private void setNoCache(HttpServletResponse httpResponse) {
long currentTime = new Date().getTime();
httpResponse.setDateHeader("Last-Modified", currentTime);
httpResponse.setDateHeader("Expires", currentTime - 86400000L);
httpResponse.setHeader("Pragma", "no-cache");
httpResponse.setHeader("Cache-Control", "no-store");
}
}

On Friday, 20 December 2024 at 4:40:22 pm UTC+11 Leon wrote:
One thing that is also quite relevant when developing a GWT application is to realize that all GWT generated code lives in the browser and that browser caching can be a problem. Whenever you do a GWT compile and want to check the result in the browser, make sure to clear the cache first because the old code will very likely not be reloaded.
I always have the developer mode in the browser open when developing and never click reload, but always 'empty cache and hard reload'. You will need it a lot.
The same goes for server updates. Best to do them late in the day or early in the morning, so users can't have stale code in their browsers. 
Either that, or learn them to do the hard reload (but you can also try and learn dogs to fly, that might have the same level of success).

Neil, I think you are trying to learn GWT in the hardest way possible. 
GWT is a way to develop a UI using java, but it is not run as java, and at runtime will not have the same possibilities as java. 
So it has its limitations when compared to what you can do with java on the server.
When you've developed something for standard java to work, based on all available libraries and known server possibilities, which you want to port to GWT is like trying to port a sportscar into a tractor. It's not impossible, but it is quite the challenge.

On Thu, Dec 19, 2024 at 9:56 PM <google-we...@googlegroups.com> wrote:
Neil Aggarwal <ne...@propfinancing.com>: Dec 18 10:45PM -0600

I am getting this error on the server:
Type 'com.propfinancing.puzzle.slitherlink.Line' was not included in the
set of types which can be
serialized by this SerializationPolicy or its Class object could not be
loaded. For security purposes,
this type will not be serialized.: instance = Line 0
 
And looking in the .gwt.rpc file, it is not listed there.
 
Interestingly, I see this:
com.propfinancing.puzzle.slitherlink.Line$STATUS
which is an Enum in that class so the GWT compiler obviously processed the
class.
 
I did not get any warnings or error messages from the GWT compiler as to
why it
decided it did not like the class so now I have to guess what it did not
like.
 
Is there a way to improve the messaging to the user to help understand
what happened?
 
Thank you,
Neil
 
--
Neil Aggarwal, (972) 834-1565, http://www.propfinancing.com
We offer 30 year loans on single family houses!
Craig Mitchell <ma...@craig-mitchell.com>: Dec 18 11:08PM -0800

At a guess, the inner enum needs to be told it can be serialised. Ie:
 
import com.google.gwt.user.client.rpc.IsSerializable;
 
enum STATUS implements IsSerializable { ... }
 
On Thursday, 19 December 2024 at 3:46:31 pm UTC+11 Neil Aggarwal wrote:
 
Colin Alworth <co...@colinalworth.com>: Dec 19 06:19AM -0800

Enums never need to be marked as serializable - unlike records, the Enum
type itself is always serializable, and GWT-RPC assumes the same. From
https://www.gwtproject.org/doc/latest/DevGuideServerCommunication.html#DevGuideSerializableTypes
 
A type is serializable and can be used in a service interface if one of the
following is true:
...
* The type is an enumeration. Enumeration constants are serialized as a
name only; none of the field values are serialized.
 
 
That error message is indeed what is used when the standard serialization
policy is read from disk, so you've resolved that earlier issue. Can you
confirm that the policy file does include Line (that is, it is correctly
reachable from the remote service instance)? If not, the GWT-RPC generator
(run when the compiler is invoked) might not have seen a clear path to how
this type could be used. Common reasons for that include declaring a field
as being of type Object, which in your head means that any type could be
assigned, but GWT-RPC doesn't want to mark every possibly class as
potentially serializable (both for security reasons and to avoid generating
serialization code for your client for every possible type).
 
On Thursday, December 19, 2024 at 1:08:53 AM UTC-6 ma...@craig-mitchell.com
wrote:
 
Neil Aggarwal <ne...@propfinancing.com>: Dec 19 10:11AM -0600

> Enumeration constants are serialized as a name only; none of the field
values are serialized.
 
 
 
What are the consequences of not having the values?
 
Reading on the Internet, it means I can't use valueOf() and ordinal().
 
But, does it work normally otherwise?
 
Can I assign a constant value to a field, read that value, and compare the
value to one of the
constants?
 
 
 
> Can you confirm that the policy file does include Line
 
 
 
It does not have Line in it:
 
 
 
@FinalFields, true
 
*com*._3dmathpuzzles.play.client.GetPuzzleService, false, false, false,
false, _, 4203465842
 
*com*._3dmathpuzzles.slitherlink.RectangularWithDiagonalsPuzzle, true,
true, false, false,
*com*._3dmathpuzzles.slitherlink.RectangularWithDiagonalsPuzzle/2547295082,
2547295082
 
com.google.gwt.user.client.rpc.IncompatibleRemoteServiceException, true,
true, true, true,
com.google.gwt.user.client.rpc.IncompatibleRemoteServiceException/3936916533,
3936916533
 
com.google.gwt.user.client.rpc.RpcTokenException, true, true, false, false,
com.google.gwt.user.client.rpc.RpcTokenException/2345075298, 2345075298
 
com.google.gwt.user.client.rpc.XsrfToken, false, false, true, true,
com.google.gwt.user.client.rpc.XsrfToken/4254043109, 4254043109
 
com.propfinancing.puzzle.Puzzle, true, false, false, false,
com.propfinancing.puzzle.Puzzle/1723715424, 1723715424
 
com.propfinancing.puzzle.slitherlink.Box, true, true, false, false,
com.propfinancing.puzzle.slitherlink.Box/1302152982, 1302152982
 
com.propfinancing.puzzle.slitherlink.Box$STATE, true, true, false, false,
com.propfinancing.puzzle.slitherlink.Box$STATE/1639054469, 1639054469
 
com.propfinancing.puzzle.slitherlink.BoxWithDiagonals, true, true, false,
false, com.propfinancing.puzzle.slitherlink.BoxWithDiagonals/2774485663,
2774485663
 
com.propfinancing.puzzle.slitherlink.Component, true, false, false, false,
com.propfinancing.puzzle.slitherlink.Component/4011233562, 4011233562
 
com.propfinancing.puzzle.slitherlink.Line$STATUS, true, true, false, false,
com.propfinancing.puzzle.slitherlink.Line$STATUS/1640439993, 1640439993
 
com.propfinancing.puzzle.slitherlink.NumberedBox, true, true, false, false,
com.propfinancing.puzzle.slitherlink.NumberedBox/1782628205, 1782628205
 
com.propfinancing.puzzle.slitherlink.Puzzle, true, false, false, false,
com.propfinancing.puzzle.slitherlink.Puzzle/2584703185, 2584703185
 
com.propfinancing.puzzle.slitherlink.RectangularPuzzle, true, false, false,
false, com.propfinancing.puzzle.slitherlink.RectangularPuzzle/3177548746,
3177548746
 
com.propfinancing.puzzle.slitherlink.RectangularWithDiagonalsPuzzle, true,
false, false, false,
com.propfinancing.puzzle.slitherlink.RectangularWithDiagonalsPuzzle/3793384887,
3793384887
 
java.lang.Exception, true, false, true, false,
java.lang.Exception/1920171873, 1920171873
 
java.lang.RuntimeException, true, false, true, false,
java.lang.RuntimeException/515124647, 515124647
 
java.lang.String, true, true, true, true, java.lang.String/2004016611,
2004016611
 
java.lang.Throwable, true, false, true, false,
java.lang.Throwable/2953622131, 2953622131
 
java.util.ArrayList, true, true, false, false,
java.util.ArrayList/4159755760, 4159755760
 
java.util.HashMap, true, true, false, false, java.util.HashMap/1797211028,
1797211028
 
java.util.LinkedHashMap, true, true, false, false,
java.util.LinkedHashMap/3008245022, 3008245022
 
 
 
> the GWT-RPC generator (run when the compiler is invoked) might not have
seen a clear path to how this type could be used
 
 
 
Unfortunately, it is silent about the reason.
 
I am hoping we can improve it help the developer instead of leaving me to
make guesses.
 
 
 
Thank you,
 
Neil
 
 
 
--
 
Neil Aggarwal, (972) 834-1565, http://www.propfinancing.com
 
We offer 30 year loans on single family houses!
Leon <leon.p...@gmail.com>: Dec 19 07:50AM +0100

Hi Neil,
 
If you hardcode an url in your GWT calls, it will be tied to that specific
url. Local testing will not be possible (outside of hacking your own hosts
file) and if you modify your servername you'll need to update your source
code.
 
The webserver is the perfect place to forward your request to the tomcat
instance.
For apache webserver you can do this with the mod_proxy module. Nginx has
the same with proxy_forward (or something similar, don't know by heart).
 
rg,
 
Leon.
 
Vassilis Virvilis <vas...@gmail.com>: Dec 19 09:15AM +0200

I agree with Leon and I can only add that there is also libapache2-mod-jk
to directly proxy from apache to tomcat. The elevator's pitch is about
speed but I think that is also simpler to understand and setup.
 
 
--
Vassilis Virvilis
Neil Aggarwal <ne...@propfinancing.com>: Dec 18 03:48PM -0600

I wrote a very simple class:
 
 
 
*package* com._3dmathpuzzles.slitherlink;
 
 
 
*import* java.io.Serializable;
 
 
 
*public* *class* TestPuzzle *implements* Serializable {
 
*private* *static* *final* *long* *serialVersionUID* = 1L;
 
 
 
/** Constructor */
 
*public* TestPuzzle() {
 
*super*();
 
}
 
}
 
 
 
And updated my RPC call to use it and I still get this:
 
 
 
Exception while dispatching incoming RPC call
 
com.google.gwt.user.client.rpc.SerializationException:
 
Type 'com._3dmathpuzzles.slitherlink.TestPuzzle' was not assignable to
 
'com.google.gwt.user.client.rpc.IsSerializable' and did not have a custom
field serializer.
 
For security purposes, this type will not be serialized.: instance =
 
com._3dmathpuzzles.slitherlink.TestPuzzle@40a58058
 
 
 
I am not sure what to do about this. My class implements Serializable
and has a no-arg constructor.
 
 
 
Thank you,
 
Neil
 
 
 
--
 
Neil Aggarwal, (972) 834-1565, http://www.propfinancing.com
 
We offer 30 year loans on single family houses!
Colin Alworth <co...@colinalworth.com>: Dec 18 01:57PM -0800

You're triggering the LegacySerializationPolicy... we should make that
clearer when it happens.
 
This occurs when your <hash>.gwt.rpc policy file wasn't present on the
server (or wasnt at the expected path). Legacy serialization is much more
strict in what it will accept.
 
Generated policy files ensure that the server and client agree on what can
be serialized. This file is generated into the same directory as your
.nocache.js file, and should be available on the server if running in
production. If running with super dev mode and a separate server, you can
direct the server to download the current policy file from SDM by
specifying system property gwt.codeserver.port with the localhost port to
the SDM server. Be sure to reload the server application or hot reload
classes if they change, so that the server side classes match the client
(and the client's policy file).
 
On Wednesday, December 18, 2024 at 3:48:49 PM UTC-6 ne...@propfinancing.com
wrote:
 
Neil Aggarwal <ne...@propfinancing.com>: Dec 18 04:44PM -0600


> This occurs when your <hash>.gwt.rpc policy file wasn't present on the
> server (or wasnt at the expected path). Legacy serialization is much more
> strict in what it will accept.
 
I saw a warning about that in the log but not know what it meant.
I am serving the client side files from Apache and the server side files
from Tomcat so they are separate.
 
Where does the server side code expect the .gwt.rpc file to be?
 
Colin Alworth <co...@colinalworth.com>: Dec 18 06:11PM -0800

The server expects the client to tell it where the file should be, and the
client reports that the file should be in the same directory as its
.nocache.js file - we call that the "base directory" of a gwt application.
 
RemoteServiceServlet.getSerializationPolicy is responsible for looking this
up, based on the incoming request, and the expected name of the generated
file (according to the client). If using SDM and a port provided as I
mentioned, this method will defer to getCodeServerPolicyUrl() if no policy
file was found on the server itself. Otherwise, you'll see the warning you
mentioned.

On Wednesday, December 18, 2024 at 4:45:23 PM UTC-6 ne...@propfinancing.com
wrote:
 
Neil Aggarwal <ne...@propfinancing.com>: Dec 18 10:06PM -0600

I see this in the log:
 
 
 
com._3dmathpuzzles.play.server.GetPuzzleServiceImpl: ERROR: The module path
requested, /play/DiagonalSlitherlink/, is not in the same web application
as this servlet, /3dmp. Your module may not be properly configured or your
client and server code maybe out of date.
 
 
 
Looking at the source code for RemoteServiceServlet, I see that it wants
the module path to start with the
webapp context, but it does not match in my setup.
 
 
 
Is there a way to override the behavior, maybe load it manually or
something?
 
 
 
I see a method putCachedSerializationPolicy but it is private.
 
 
 
Thank you,
 
Neil
 
 
 
--
 
Neil Aggarwal, (972) 834-1565, http://www.propfinancing.com
 
We offer 30 year loans on single family houses!
Neil Aggarwal <ne...@propfinancing.com>: Dec 18 10:21PM -0600

> The server expects the client to tell it where the file should be, and
the client reports that the file should
 
> be in the same directory as its .nocache.js file
 
> we call that the "base directory" of a gwt application.
 
 
 
I decided to stop fighting with GWT and moved the module from Apache
to Tomcat. The test RPC started working once I did that.
 
 
 
I changed the code to try to retrieve my DiagonalSlitherlink puzzle, but it
it is giving me an error. I am investigating.
 
 
 
Thanks for the help!
 
 
 
Neil
 
 
 
--
 
Neil Aggarwal, (972) 834-1565, http://www.propfinancing.com
 
We offer 30 year loans on single family houses!
You received this digest because you're subscribed to updates for this group. You can change your settings on the group membership page.
To unsubscribe from this group and stop receiving emails from it send an email to google-web-tool...@googlegroups.com.

--
You received this message because you are subscribed to the Google Groups "GWT Users" group.
To unsubscribe from this group and stop receiving emails from it, send an email to google-web-toolkit+unsubscribe@googlegroups.com.
To view this discussion visit https://groups.google.com/d/msgid/google-web-toolkit/fc5b7786-994e-44f2-a27e-d4fe1e18305en%40googlegroups.com.
Posted by at No comments:
Subscribe to: Posts (Atom)