Develop Reference

gwt-dev - Librairies with same package name

This is my first post on stackoverflow, please be indulgent.
Within my project, I use the library commons-digester-1.8.
Following a need, I now use the library gwt-dev-2.3.0.
When launching the application I get this error :
Exception caught while initializing context java.lang.NoSuchMethodError: org/apache/commons/digester/xmlrules/DigesterLoader.createDigester(Lorg/xml/sax/InputSource;)Lorg/apache/commons/digester/Digester;
at fr.cnasea.commons.webfwk.util.config.lecture.XMLDigesterReader.getConfig(XMLDigesterReader.java:157)
at fr.cnasea.commons.webfwk.util.config.CnaseaAppConfigurator.configure(CnaseaAppConfigurator.java:76)
at fr.cnasea.osiris.commons.gwt.server.Config.contextInitialized(Config.java:47)
It turns out that the two libraries have the same class in the same package with the same method:
Same class
Since the use of gwt-dev, it is the method of this library which is called.
I tried to use newer versions of gwt-dev but the environment makes it not possible
How can I fix it?
Thanks for your help :)

(From my answer to your same question on the github project)
The gwt-dev.jar should not be on your server classpath - it is only used to compile your application. The same is true for gwt-user.jar. Only gwt-servlet.jar (and possibly requestfactory-server.jar) should end up on your server classpath, the others are intended only to be present when compiling, either to do the work of compiling, or to provide the compiler the classes you need.

NoSuchMethodError after cleaning the project

I'm currently getting this error:
java.lang.NoSuchMethodError: org.json.JSONObject.keySet()Ljava/util/Set;
at ee.ut.cs.Parser.accessLint(Parser.java:39)
I have tried cleaning the project to no awail.
I suspect I have an error in the src/plugin/parse-htmlraw/build.xml while creating the jar file but I'm not certain. I understand that this error is because the function does not exist at runtime, but the object is created which means that the class is there, just not that function. I decompiled the .class file in created jar and it has the necessary functions.
Code is available at https://github.com/jaansusi/WCAGgrader
Q: What is wrong with the build that produces this error?
The problem is that even if I put the necessary class files in the jar I create, they are not linked correctly and the class that's called in the jar can't locate functions inside the other classes. The class object JSONObject is created but the functions inside the JSONObject class can't be found.

If you do not find the problematic version, there is a possibility you get it (especially if you are using Spring) from the following dependency -
<artifactId>android-json</artifactId>
<groupId>com.vaadin.external.google</groupId>
excluding it worked for me,
An easy way of analyzing dependencies is the maven-helper plugin in Intellij, see here

Check for the version you have used.
There might be a case where 2 different versions are being used which in turn causes this error.

To their own maven local repository com\Google\code\gson\gson, see if there are two or more version about json, will have to do is to delete the old, and remember to look at any other place in the project is introduced into the old version of the dependence, if any, change the old version of the dependence to the new version is perfectly solved this problem

NoClassDefFoundError when code moved from R2007a to R2013a

I am working on moving code from R2007a to R2013a. I am getting a java.lang.NoClassDefFoundError during my run in R2013a which does not appear in R2007a. It occurs when I call.
feval('get',fname,jevent);
Where fname is a product.ProxyField object for an Object Filter and jevent is a product.format.java.internal.JavaEvent.
The class is in a jar file on the path and is being accessed by another class in the same jar file. The stack trace does not leave the realm of the product if that helps.
I do not have access to the original code for the jar file. I do have access to code derived from that original code and both classes are in the same package. I'm guessing this has something to do with differences in the java version but I'm not sure what to do since I don't have the original code to recompile.
Unfortunately I can't provide actual source or full detail but a google search only yielded results for MATLAB startup issues. Any thoughts?

Seems like the difference between R2007a and R2013a is that the first uses 1.5 jre and second uses 1.6 jre. It would be easier to help you if you provided the stack trace showing the exception. Sometimes classes get moved around in between jvm versions, so having the actual missing classes would help in determining if the missing class is a class that was just moved around to a different package. You could take the missing class, google it adding the same exception message as you put above and seeing who else ran into similar issues.

Scala - class is broken

I am trying to build a project that has an external dependency on one of the jars. I have a Java version of the class that uses class X from the jar and that builds fine. As soon as I try to build taht using scala, I am getting an error that the "class X is broken" followed by NullPointerExcpetion. What might be the reason for it?

You have a broken dependency on your MANIFEST file. Add the dependency of that X class and try again.

This can happen if your external dependency itself depending on something external. This way builder can not make a whole class, so it is reporting you that class or jar is broken.

JavaCompiler returning null

I am creating a program along the lines of Codingbat.com.
During Runtime, it needs to compile code, and then execute it. This has all been handled.
Currently, I am forced to use the JavacTool, which requires it to be packed alongside.
I have 2 basic questions:
1) How can I stop the ToolProvider.getSystemJavaCompiler() from returning null when ran from an executable jar?
2) If the above is not possible, is there a way to add the jar of com.sun.tools.javac.api.JavacTool; without having it as a referenced library, so that it acts like a regular import?
Thanks for answering this, if you would like, I could upload the Jar with the referenced library, and the jar without it.
Just to be clear, the one with the referenced library works, but it is way to large, and slower then the jar that is ran through eclipse, that uses the JavaCompiler, not the JavacTool
Thanks
Edit:
I am pretty sure this is possible with java as I have seen it before, yet forget where and how.

I suspect it's just a problem of which version of Java you run. If you run the version which comes with the JRE, it won't have the tools available. If you run the version which comes with the JDK, it will.
As an example, here's a short but complete program:
import javax.tools.*;
public class Test
{
public static void main(String[] args)
{
System.out.println(ToolProvider.getSystemJavaCompiler());
}
}
Running it with the JRE version of java.exe on my laptop:
c:\Users\Jon\Test>"\Program Files\java\jre7"\bin\java Test
null
And now with the JDK:
c:\Users\Jon\Test>"\Program Files\Java\jdk1.7.0"\bin\java Test
com.sun.tools.javac.api.JavacTool#441944ae
So try explicitly specifying the a Java binary associated with the JDK.

So you already know that all your users will have a JDK installed and you know how to find the classpath of the JDK when you're in your Java program. You don't need to load a DLL. You need to load the com.sun.tools.javac.api.JavacTool class in tools.jar. See How to load a jar file at runtime on how to load tools.jar