incorporting external jars

[jonathan]

my gwt app relies on external libraries such as
java.beans.PropertyChangeEvent and my own custom classes from another
eclipse project.
what's the best way of incorporating them?
I added these libs to gwt compiler classpath, but I get
[ERROR] Line 70: No source code is available for type
java.beans.PropertyC
hangeEvent; did you forget to inherit a required module?

Do I have to make all external dependencies into a module? please
help.
thanks!

[Vitali Lovich]

GWT only implements a very small portion of the JRE (a lot of stuff is not available from a browser context anyways).  So what you're trying to do apparently is use a Java library within your client code which more likely than not will not work.

GWT has two parts to it.  Client code that is java translated into javascript run on the browser & server code which is regular java code running on a traditional app server.

Hope this helps

[ds]

Hi,
Would be nice if you could please explain it in detail. I am also
facing the same probem. How can I overcome the same. I have added a
crimson-1.1.3.jar in order to import javax.xml.parsers,org.w3c.dom and
org.xml.sax packages in a GWt-Ext app. But when I run my app, I get
"Line 31: No source code is available for type
javax.xml.parsers.DocumentBuilderFactory; did you forget to inherit a
required module?"
"Line 32: No source code is available for type
javax.xml.parsers.DocumentBuilder; did you forget to inherit a
required module?"
"Line 33: No source code is available for type org.w3c.dom.Document;

did you forget to inherit a required module?"

Thanks
ds

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[mikedshaffer]

Thanks to Vitali for answering this so promptly, so in the effort of
teamwork, I'll attempt to follow up and answer ds's inquiry.

Every modern programming language needs a "container" to run it's code
in. Java has a container, .Net has a container, even old Visual Basic
had a container. Not trying to be condescending here, just trying
to be clear. Most modern software development is done using a high
order language which at the end of the compilation process, what is
produced by a compiler is native programming code. OK, so far?

The application container that runs Javascript is also known as a web
browser. GWT is a compiler that compiles high order Java code into
the native language of the browser, Javascript. So the GWT compiler
needs to know how to convert Java code into Javascript. And that's
the power of GWT. But the container dictates what can be compiled, or
said another way, if the container can't or won't allow something that
perhaps you can do in the higher order language, it's the compiler's
"job" to tell you that.

The browser as an application container, has very strict rules placed
upon it. No amount of Javascript running in a browser can directly
access the file system of the client. Need to dig into the client
system and get things like IP addresses and info like that? The
browser can't allow code to do that. The browser is also single
threaded so any threading access can't be done. All of these things
(and many more) are very, very easy to do in Java. We've got the File
class, System.IO, all of those libraries out there. And even though
it is very simple to do in Java, since Javascript can't do it, GWT
can't compile the resulting Javascript code out. And that's what
these errors mean. In so many words, these errors are saying "you are
trying to get me to create Javascript from Java code that the browser
will not allow."

The GWT guys have done and continue to do an amazing job of creating a
compiler that turns Java into Javascript. Virtually everything you
can do in a browser, in Javascript is available to you in the GWT Java
development process. But there are literally thousands of libraries
that you won't be able to use in the browser, that they are not going
to move into GWT or more appropriately, that they *can't* move into
GWT. Not a Google/GWT problem, but a Javascript/Browser "problem".
If you take a look at
http://code.google.com/docreader/#p=google-web-toolkit-doc-1-5&s=google-web-toolkit-doc-1-5&t=RefJreEmulation
you'll see everything that GWT can do.

The basic rule is that if you can do it in Javascript, GWT can do it.

Hopefully this helps. If you do a search in these forums, you'll see
these error messages and this discussion repeated throughout.

Good luck!

Later,

Shaffer