Develop Reference

system classloader does not use the overriden method

I have a program that generates classes using JCodemodel and a dynamic class loader. I parse a yaml file, generate the required classes and map the structure of the file . Everything is fine so far.
Snakeyaml handles the parse and write nicely, so the definition of classes if fine.
Then I try to access a method properties() which is redefined in the yaml.
I first load the file into a "Tree", load its root element as a "Compute" and print its class and methods ; then I call the overridden method.
The computeb class is dynamicaly generated, as well as the computeb$Properties.
here is the code (I replaced my packages by shorter ones):
Tree tree = Parser.load(new FileInputStream("src/test/resources/tree.yaml"));
mypackage.Compute c = (mypackage.Compute) tree.root();
System.err.println("class : " + c.getClass());
for (Method m : c.getClass().getMethods()) {
System.err.println(" method : " + m);
}
System.err.println("properties() class is " + c.properties().getClass().getName());
The result is :
class : class computeb
method : public computeb$Property computeb.properties()
method : public mypackage.Compute$Property mypackage.Compute.properties()
(...)
properties() class is mypackage.Compute$Property
As you notice, the class has the two methods present, however the properties() method called is the second one. I would want to call the first one (which is defined in the classloader) . Why does it happen this way ? What should I do ?

OK I got it, I had an issue while statically generating the classes on a specific folder.
Since I had to resolve existing classes to avoid creating them twice, I only resolved classes that were starting with my package prefix.
This worked well in static generation, but in dynamic generation I had previously generated classes I could not load, while they already were present. Basically that means that my class generator was creating another class with same name, so sometimes the classloader could refer to one class, sometimes to another.
I'm working on correcting this dirty mess.

How to resolve file name issue with multiple interfaces names, created in a file

how to :
when i create multiple interface(s) to check details, I have learn that of multiple extension of interface with interfaces.
it gives me error with file name , because previous I was named the file with interface name ,primarily developed but when i make new interface(s) ,editor frequently told me to rename the file name with currently developed interface .
what is the conflict & how to resolve .

Each public type has to be in its own file. For example, if you have class declared like this:
public class MyClass {...}
You have to put it in a file called MyClass.java.
An interface is also considered a type in Java. Therefore, if you have an interface such as:
public interface MyInterface {....}
You also have to put it in its own file named like the name of the interface, that is, MyInterface.java.
The same is also true of enum. If it's public enum, it goes in its own file named like the enum.
If you have non-public types, you can put them in the same file as another type. But as soon as you make them public, you need to move them to their own file.

Use Constants interface in GWT Project

I have not yet used Constants interface in GWT and I am having problem to run the example CellTable. The deferred binding fails and the central error message is: "No resource found for contactDataBaseCategories". contactDataBaseCategories is a method defined in the interface DataBaseConstants and returns an array of Strings. I suspect I must create a properties (txt?) file and to define the categories, but I am not sure, since I come across this case for the first time. How can I do it properly to make the example of the CellTable run?
Update: I have created the ContactDatabase.DatabaseConstants.properties file in the same package in which the interface is declared, I have added the line in the file:
contactDataBaseCategories = friends, coWorkers, other
but it still does not work. The error is again : "No resource found for contactDataBaseCategories" and then
"Deferred Binding failed for com.al.celltablöeexample.ContactDatabase.DatabaseConstants".
What going wrong?

This is how i do it
Constant interface
public interface DataBaseConstants extends Constants
{
#Key("contact-database-categories")
String contactDataBaseCategories();
}
property file. DataBaseConstants.properties
contact-database-categories = "Your String"
You can use it
public DataBaseConstants dbConstant= GWT.create( DataBaseConstants .class );
dbConstant.contactDataBaseCategories();
Edited
If you want to pass string array then you can do it like this
#DefaultStringArrayValue({"cat1", "cat2", "cat3", "cat4", "cat5"})
String[] contactDataBaseCategories();
More about Constants

I have finally managed it. The problem was that it could not find the resource/file: ContactDatabase.DatabaseConstants.properties. I have changed it to DatabaseConstants.properties and I removed the inner interface to its own file. The same I did in the class CwCellTable on the interface CwConstants. In the example page moreover, the instantiation of the CwConstants interface is missed, and one must do also this (in the constructor), like in the ContactDatabase class.

Just to add to Dilantha's answer you can then set
contact-database-categories = Family, Friends, Coworkers, Businesses, Contacts
in order to comply with the example.
Tip : In order to make the example work create a costructor in CwCellList and add the following :
initWidget(onInitialize());

How to invoke methods of a class (in java) when class name and method name are stored in two different strings

Well, not sure if the question sounds a little weird but let me try to put forth the clarification :
I have a JSP page. On this JSP page, I am calling a java class defined in one of my packages under my projects. This class connects to database and access a table which has got fields namely - functionname, function class. Now I am able to retrieve in my JSP the two strings, lets say -
String funName = "ComFunctions";
String className = "funLog");
Now, I want to invoke this function using this class name i.e. basically something like - className.funName
Is it possible in Java? Actually, these functions and class names will be retrieved in a for loop, so I can't directly call using real classname but have to use strings.
Kindly suggest if there is a way or worl around or if the question is still unclear.
I tried the following approach so far but no luck -
Class c = Class.forName(className);
Object o = c.newInstance();
Method m = c.getMethod(funName, String.class); // Not sure what is supposed to be second parameter here i.e. after funName
Error - the above code gives " No class found error". And i made sure that class is there under the package. Even adding package name i.e. packge.classname didnt help and it says "Symbol not found" for package name.
Any pointers please?
Example class that I am trying to invoke -
package mypackage;
public class ComFunctions extends WDriverInitialize{
public static void main(String[] args){
}
public static void funLog(String username){
System.out.println(userName);
}
}

You need to make sure the compiled class is in the webapp's classpath (ie, WEB-INF/classes) and use the FQN (ie, add the package name). You could also make a JAR file of your classes and add that to the WEB-INF/lib folder.
Also, the extra parameter in getMethod is to fetch a method with the matching parameters (ie, in your example, one that takes a String

You're missing one piece of the puzzle, and that's the method arguments. Without it, you can't really be sure what method funName is referring to, and what arguments to pass to it.
And of course, the class needs to be in the classpath.

Java - Multiple Package In Eclipse Issue

I have the following set of packages within my source folder.
The packages are shapes,model,views.
Say I have a class file in my model folder that has the following piece of code:
shapes.interfaceforshapes[][] temp = model.get2dshapearray();
if(temp[x][y].getClass().isInstance(shapes.cTriangle)){
}
Please note in the above code temp[x][y] will return a class that interfaces my shapeInterface
and all classes within the shapes folder interface this.
Am I doing the correct thing to say "Is the class within my array of type cTriangle"?
I currently get the error:
shapes.cTriangle cannot be resolved to a variable
but I don't want to match a variable, I want to test it agaisnt the class cTriangle within my package shape.
Thanks

Use instanceOf operator if you want to check if the object is an instance of a certain class, while the isInstance method expects an instance of a class.
if( temp[x][y] instanceOf shapes.cTriangle) {//dosomething }

That is not how isInstance(Object) works. You have to call it on a class and pass in the object you want to match. You would do:
shapes.cTriangle.class.isInstance(temp[x][y]);
assuming cTriangle is a class and temp[x][y] returns an object and you want to check if that object is of type cTriangle.