I try to create the entity like this:
DatastoreService ds = DatastoreServiceFactory.getDatastoreService();
Entity stock = new Entity("Stock", 1);
stock.setProperty("Stock", "FCB");
ds.put(stock);
but keep getting the error:
No source code is available for type com.google.appengine.api.datastore.DatastoreService; did you forget to inherit a required module?
The error means just what it says, the GWT compiler needs access to the Java source it compiles to Javascript, and obviously DatastoreService is not something that should exist on the frontend - so you have an architecture issue here.
You'll need to write a proxy that can call a server component (Which in turns calls the DatastoreService) and returns DTOs/value objects (that you define and thus have the source for).
Cheers,
No source code is available
GWT transliterate Java to Javascript, reading it's source code and there a limited language support.
What you're trying to achieve is a Server only operation and you're adding this operation within the client code, which will run on a browser. Neither GAE allow this or GWT has the source of these classes nor capability to do so.
Solution
You need to create a request to your server that will access the DatastoreService , the return the output to the client code.
Below a example of a properly architect GWT web application:
Related
I have an Eclipse RAP 2.3 application with two entry points, say /first and /second.
In the GUI of the first entry point, there is a button with which I would like to open the second entry point in a new browser tab. The event handler of that button is currently
UrlLauncher launcher = RWT.getClient().getService( UrlLauncher.class );
launcher.openURL( "/second");
This already doesn't work when the application is deployed as myapp.war in a Tomcat web server (should then be /myapp/second).
My questions:
What's the best way to determine the URL to open within the event handler?
Do I have to fetch the HttpServletRequest, get the context path and so some string manipulation?
Is it actually safe to call RWT.getRequest() at this point?
Update
According to Rüdiger's comment I can acquire the context path in two different ways.
The first approach is
RWT.getRequest().getContextPath();
where RWT.getRequest() is documented with
This method is not recommended
Secondly, I could obtain it with
ApplicationContextImpl ac = (ApplicationContextImpl) RWT.getApplicationContext();
String contextPath = ac.getServletContext().getContextPath();
where the IDE displays the warning
Discouraged access: The type ApplicationContextImpl is not accessible due to restriction on required library ...\org.eclipse.rap.rwt_2.3.2.20150128-1013.jar
Despite the warning, it still works when deploying a WAR file with OSGi bundles to Tomcat.
So, in both cases there is some kind of warning, which makes the solutions look rather like workarounds.
Using RWT.getRequest() is not recommended because usually RWT would shield you from the lower-level servlet API and certain direct interactions with the request could even interfere with RWTs life cycle and yield funny responses.
While in your case it would be safe to access the ServletContext via RWT.getRequest(), I recommend to use
RWT.getUISession( display ).getHttpSession().getServletContext();
to access the servlet context.
The second approach accesses internal classes that aren't part of the public API and therefore shouldn't be use. The accessed classes may change or be (re)moved in the future without further notice and break your application.
I'm developing a GWT project at the moment and it's been up and running for a while. New functionality that is to be added require extensive testing, visualizing and simulating of a specific algorithm. I would like to export that specific algorithm so that I may call it directly from JavaScript and do some canvas magic.
How can I export a number of classes for direct use in JavaScript from a GWT project?
I've tried using the GWT exporter, following the Getting Started section closely.
I've noticed that my output directory contains a new generator class (TestClassExporterImpl.java) but the final JavaScript output contains no trace of my TestClass or the exported methods.
I'm sure I've made a mistake somewhere on the way or didn't understand the GWT exporter correctly.
Try to disable obfuscation, it will create the same names in Javascript as in the original Java code
I am trying to build a simple gwt project that fetches tweets and displays them.The server passes back the tweets of type twitter4j.Tweet to the client.
Both modules import twitter4j.Tweet.
But when I run I get the following error:
--- ERROR: Line 37: No source code is available for type twitter4j.Tweet; did you forget to inherit a required module?.
I seem to have problems in inheriting twitter4j. All the posts I have seen about inheriting a jar file are not clear about how to do so. I understand I must write an inheritance instruction into gwt.xml file, something like
---
but if I try
---
it does not work. Can anyone please explain?
In a post I found on the Web one person suggested not to inherit it but:
-- Don't put twitter4j to your gwt.xml. Just add it your project class path. and make all functionalities like status updating and all in your serviceImpl. Try
This confuses me even more. I have added the jar file to my project libraries. But it does not work
I suspect I am missing something quite elementary here, but I am totally stuck. Is there something like a GWT path?
Many thanks for any help
Keep in mind that everything in your client package is compiled to JavaScript and executed in the user's browser. Thus, you'll only be able to use twitter4j's classes on the server-side of your application; you'll have to create some sort of light-weight GWT-serializable "proxy object" to pass data back and forth between your client and server tiers.
Since you can't use twitter4j on the client side of your app, you will not need anything in your .gwt.xml file referencing it. Instead, you'll add twitter4j to your classpath and do all your updating on the server side (as mentioned toward the bottom of your question). You do mention that it "does not work," but there's not enough information in your question to try to figure out why.
I am developing an app using Grails and GWT for a client side.
I want to use the same date format both on the client side and on the server side (preferably defined in one file).
So far i've understood that Grails got it's own mechanism for internationalization (grails-app/i18n). I know i can access these messages from any server code using app context.
I can also access any resource file inside web-app directory.
For the client side, i can use ConstantsWithLookup interface and GWT.Create(...) to get an instance of it.
But, i still haven't found good solution to integrate these two together, so i have date format defined in one place. Any ideas or tips?
Thanks,
Sergey
After digging into Grails more, i came to a solution.
I've put constant into .properties file under grails-app/i18n.
Then, i hook to eventCompileEnd and i copy resources from grails-app/i18n to specific package in target\generated-sources.
After this step is completed, i generate google I18N interfaces using copied property files.
I've put this functionality to separate plugin.
_Events.groovy:
includeTargets << new File("${myPluginDir}/scripts/_MyInternal.groovy")
eventCompileEnd = {
internalCopyMessageResources();
}
eventCopyMessageResourcesEnd = {
generateI18NInterface();
}
Now it is possible to access localized data from server side and from client side.
I'm working on a GWT project and I find it very tedious to have to add a function to my servlet, then copy and paste the function signature into my Service interface, then copy and paste it into my ServiceAsync interface and change the return parameter to be a callback. Is there a tool or a setting where I can just add public methods to my class and they can get copied into the other interfaces? Even if its not automatic it would be nice to be able to select specific methods and have them copied automatically.
I'm using eclipse and ideally it would update my interface each time I save implementation since thats when it checks my code and complains that my changes break the interface.
If you add the method to your *Service interface, then Eclipse can auto-generate the method ("Add unimplemented methods...") in your *ServiceImpl servlet, which you can then just fill in. Also, if you've got the Google Eclipse plugin installed, it will underline the new method in your *Service interface and complain that it's not in the *ServiceAsync. It might have a CTRL + 1 option to generate it in that interface as well.
You don't really need a tool. Just factor out the many RPC methods by just one method that takes a Request/Response. all you need to do is create subclasses of Request/Response and you don't need to think about adding new methods in the 2 interfaces.
You can use Google Guice on the server side to map the incomming request to a class handling the call... or you could use a visitor approach to forward the incoming request to the code handling the request (without resorting on a big instanceof construct).
Instantiations WindowBuilder GWT Designer does exactly what you are looking for.
The RemoteService Wizard will create all three files at the same time as well as keep them in sync as you make changes.
http://www.instantiations.com/windowbuilder/gwtdesigner/index.html
FWIW - I am only a user/purchaser of this product. I am not employed or in any other way related to Instantiations.