Is it possible to use JavaLoader to get objects returned by CF-called web services, and JavaLoader-loaded objects to be the same classpath context? I mean, without a lot of difficulty?
// get a web service
ws = createObject("webservice", local.lms.wsurl);
// user created by coldfusion
user = ws.GenerateUserObject();
/* user status created by java loader.
** this api provider requires that you move the stubs
** (generated when hitting the wsdl from CF for the first time)
** to the classpath.
** this is one of the stubs/classes that gets called from that.
*/
UserStatus = javaLoader.create("com.geolearning.geonext.webservices.Status");
// set user status: classpath context clash
user.setStatus(UserStatus.Active);
Error:
Detail: Either there are no methods with the specified method name and
argument types or the setStatus method is overloaded with argument
types that ColdFusion cannot decipher reliably. ColdFusion found 0
methods that match the provided arguments. If this is a Java object
and you verified that the method exists, use the javacast function to
reduce ambiguity.
Message: The setStatus method was not found.
MethodName setStatus
Even though the call, on the surface, matches a method signature on user--setStatus(com.geolearning.geonext.webservices.Status)--the class is on a different classpath context. That's why I get the error above.
Jamie and I worked on this off-line and came up with a creative solution :)
(Apologies for the long answer, but I thought a bit of an explanation was warranted for those who find class loaders as confusing as I do. If you are not interested in the "why" aspect, feel free to jump to the end).
Issue:
The problem is definitely due to multiple class loaders/paths. Apparently CF web services use a dynamic URLClassLoader (just like the JavaLoader). That is how it can load the generated web service classes on-the-fly, even though those classes are not in the core CF "class path".
(Based on my limited understanding...) Class loaders follow a hierarchy. When multiple class loaders are involved, they must observe certain rules or they will not play well together. One of the rules is that child class loaders can only "see" objects loaded by an ancestor (parent, grandparent, etcetera). They cannot see classes loaded by a sibling.
If you examine the object created by the JavaLoader, and the other by createObject, they are indeed siblings ie both children of the CF bootstrap class loader. So the one will not recognize objects loaded by the other, which would explain why the setStatus call failed.
Given that a child can see objects loaded by a parent, the obvious solution is to change how the objects are constructed. Structure the calls so that one of the class loaders ends up as a parent of the other. Curiously that turned out to be trickier than it sounded. I could not find a way to make that happen, despite trying a number of combinations (including using the switchThreadContextClassLoader method).
Solution:
Finally I had a crazy thought: do not load any jars. Just use the web service's loader as the parentClassLoader. It already has everything it needs in its own individual "class path":
// display class path of web service class loader
dynamicLoader = webService.getClass().getClassLoader();
dynamicClassPath = dynamicLoader.getURLS();
WriteDump("CLASS PATH: "& dynamicClassPath[1].toString() );
The JavaLoader will automatically delegate calls for classes it cannot find to parentClassLoader - and bingo - everything works. No more more class loader conflict.
webService = createObject("webservice", webserviceURL, webserviceArgs);
javaLoader = createObject("component", "javaloader.JavaLoader").init(
loadPaths = [] // nothing
, parentClassLoader=webService.getClass().getClassLoader()
);
user = webService.GenerateUserObject();
userStatus = javaLoader.create("com.geolearning.geonext.webservices.Status");
user.setStatus(userStatus.Active);
WriteDump(var=user.getStatus(), label="SUCCESS: user.getStatus()");
Related
I have a custom grid control that inherits from TGrid called TFmGrid. This control was working fine in Rad Studio 10 Seattle Update One. I recently upgraded to 10.1 Berlin and started noticing this error message showing up on my TFmGrid controls both when I run the application and in the designer:
A descendant of TStyledPresentationProxy has not been registered for class TFmGrid. Maybe it is necessary to add the FMX.Grid.Style module to the uses section
The image below shows how the error message shows up on my grid controls:
I started by doing as the message suggests, and adding #include <FMX.Grid.Style.hpp> to the header file of my TFmGrid control, however this seems to have done nothing.
So as far as trying to register a decendant of TStyledPresentationProxy I am not exactly sure where to start. I found this documentation about a method which:
Attempts to register the presentation proxy class with the specified name or the specified combination of control class and control type.
So I assume I need to use this method or at least something similar, but I don't understand how I am supposed to go about calling this method.
But then that brings up the question of WHERE do I call this code?
My custom control has a method in its namespace called Register() which I believe was autogenerated by the IDE when the control was created:
namespace Fmgridu
{
void __fastcall PACKAGE Register()
{
TComponentClass classes[1] = {__classid(TFmGrid)};
RegisterComponents(L"Kalos FM Controls", classes, 0);
}
}
Do I need to call something in there to register a decendant of TStyledPresentationProxy? What is the proper way to go about this?
Just override virtual method DefinePresentationName in you TfmGrid and return name of presentation name for grid:
function TfmGrid.DefinePresentationName: string;
begin
Result := 'Grid-' + GetPresentationSuffix;
end;
Fm registers presentation by string name and uses class name for it, so if you create new component (based on existed) you automatically change classname, so system cannot find presentation for you. There are two solution:
Said that you will use presentation from TGrid (DefinePresentationName)
Register existed presentation for you class (look at the initialization section of FMX.Grid.Style.pas)
P.S. Year ago i wrote article about it in common eNew approach of development of FireMonkey control “Control – Model – Presentation”. Part 1 I hope it will help you
It's simple :
Just put "StyleBook" component to your form
I had the same issue with a test component I was developing.
Complementing Yaroslav Brovin's speech, I solved the problem by adding the class register in the initialization and finalization clauses at the end of the unit, like this:
initialization
TPresentationProxyFactory.Current.Register(<COMPONENT CLASSNAME HERE>, TControlType.Styled, TStyledPresentationProxy<TStyledGrid>);
finalization
TPresentationProxyFactory.Current.Unregister(<COMPONENT CLASSNAME HERE>, TControlType.Styled, TStyledPresentationProxy<TStyledGrid>);
In my case looks like this:
initialization
TPresentationProxyFactory.Current.Register(TSGrid, TControlType.Styled, TStyledPresentationProxy<TStyledGrid>);
finalization
TPresentationProxyFactory.Current.Unregister(TSGrid, TControlType.Styled, TStyledPresentationProxy<TStyledGrid>);
PS: Don't forget to declare the FMX.Presentation.Factory,
FMX.Presentation.Style and FMX.Grid.Style units in the uses clause
The following is an API reference for a method in "QmlDocument" class(Blackberry10).
Builder create (const QString &qmlAsset, boolautoLoad )
Creates and returns a builder for constructing a QmlDocument instance
with a parent object and an asset name to load the document from.
Parameters qmlAsset The QML asset name load the document from,
specified relative to the assets root. autoLoad if true the document
is automatic loaded, otherwise it is required to call load function
explicitly. The default is true . Since: BlackBerry 10.0.0
Now what is exactly meant by a "Builder" here. What is its purpose? what is the difference of creating an object from QmlDocument class with "new" keyword, and creating the object with the method defined above?
Builders are usually classes defined locally to the associated class (ie QmlDocument::Builder) that allow chaning of methods with operator . () in a way similar to that done with iostreams and operator << (). What it gets you is a more readable way of createing objects (and potentially their childre) in one statment rather than creating with a new operator and a number of function calls. A better example than QmlDocument might be the Container class:
Container *container1 = Container::create()
.preferredSize(200, 200)
.background(Color::Blue);
This creates a new Container, sets the preferred size and background color. The implementations details are hidden. Somewhat simmilar to an opaque type in C.
I am working on a system that uses drools to evaluate certain objects. However, these objects can be of classes that are loaded at runtime using jodd. I am able to load a file fine using the following function:
public static void loadClassFile(File file) {
try {
// use Jodd ClassLoaderUtil to load class into the current ClassLoader
ClassLoaderUtil.defineClass(getBytesFromFile(file));
} catch (IOException e) {
exceptionLog(LOG_ERROR, getInstance(), e);
}
}
Now lets say I have created a class called Tire and loaded it using the function above. Is there a way I can use the Tire class in my rule file:
rule "Tire Operational"
when
$t: Tire(pressure == 30)
then
end
Right now if i try to add this rule i get an error saying unable to resolve ObjectType Tire. My assumption would be that I would somehow need to import Tire in the rule, but I'm not really sure how to do that.
Haven't use Drools since version 3, but will try to help anyway. When you load class this way (dynamically, in the run-time, no matter if you use e.g. Class.forName() or Jodd), loaded class name is simply not available to be explicitly used in the code. I believe we can simplify your problem with the following sudo-code, where you first load a class and then try to use its name:
defineClass('Tire.class');
Tire tire = new Tire();
This obviously doesn't work since Tire type is not available at compile time: compiler does not know what type you gonna load during the execution.
What would work is to have Tire implementing some interface (e.g. VehiclePart). So then you could use the following sudo-code:
Class tireClass = defineClass('Tire.class');
VehiclePart tire = tireClass.newInstance();
System.out.println(tire.getPartName()); // prints 'tire' for example
Then maybe you can build your Drools rules over the interface VehiclePart and getPartName() property.
Addendum
Above make sense only when interface covers all the properties of dynamically loaded class. In most cases, this is not a valid solution: dynamically loaded classes simply do not share properties. So, here is another approach.
Instead of using explicit class loading, this problem can be solved by 'extending' the classloader class path. Be warn, this is a hack!
In Jodd, there is method: ClassLoaderUtil.addFileToClassPath() that can add a file or a path to the classloader in the runtime. So here are the steps that worked for me:
1) Put all dynamically created classes into some root folder, with the respect of their packages. For example, lets say we want to use a jodd.samples.TestBean class, that has two properties: number (int) and a value (string). We then need to put it this class into the root/jodd/samples folder.
2) After building all dynamic classes, extend the classloaders path:
ClassLoaderUtil.addFileToClassPath("root", ClassLoader.getSystemClassLoader());
3) load class and create it before creating KnowledgeBuilder:
Class testBeanClass = Class.forName("jodd.samples.TestBean");
Object testBean = testBeanClass.newInstance();
4) At this point you can use BeanUtils (from Jodd, for example:) to manipulate properties of the testBean instance
5) Create Drools stuff and add insert testBean into session:
knowledgeSession.insert(testBean);
6) Use it in rule file:
import jodd.samples.TestBean;
rule "xxx"
when
$t: TestBean(number == 173)
then
System.out.println("!!!");
end
This worked for me. Note that on step #2 you can try using different classloader, but you might need it to pass it to the KnowledgeBuilderFactory via KnowledgeBuilderConfiguration (i.e. PackageBuilderConfiguration).
Another solution
Another solution is to simply copy all object properties to a map, and deal with the map in the rules files. So you can use something like this at step #4:
Map map = new HashMap();
BeanTool.copy(testBean, map);
and later (step #5) add a map to Drools context instead of the bean instance. In this case it would be even better to use defineClass() method to explicitly define each class.
I have been researching this, and cannot seem to find anything about it.
We work on CF8. When my coworker tried installing my latest code updates, he started seeing errors that the argument supplied to a function was not of the specified interface type. Worked fine for me. Same set up. Sometimes it works for him. Also have the problem on our dev server.
I have since been able to isolate and reproduce the problem locally.
Here is the set up.
I have 2 mappings on the server:
"webapp/" goes to c:\webroot\
"packages/" goes to c:\webroot\[domain]
Then I created an interface, call it ISubject and a component that implements it, called Person, and saved both under packages. Here is the declaration for Person:
cfcomponent implements="packages.ISubject"
Finally, there is a component, called SubjectMediator with a function, called setSubject, that wants an object of the ISubject interface type. Here is the argument declaration for setSubject:
cfargument name="subject_object" type="packages.ISubject"
To implement:
variables.person = createObject("component", "packages.Person").Init();
variables.subjectMediator = createObject("component", "packages.SubjectMediator ").Init();
variables.subjectMediator.setSubject(variables.person);
That last line throws the error that Person is not of type ISubject. If I do isInstanceOf() on Person against ISubject it validates fine.
So the reason this is happening? Dumping getMetaData(variables.person) shows me that the interface path is webapp.[domain].ISubject. And indeed, if I change the type attribute of the argument to use this path instead of packages.ISubject, all is fine again.
Coldfusion seems to be arbitrarily choosing which mapping to resolve the interface to, and then simply doing a string comparison for check the type argument?
Anyone had to contend with this? I need the webapp mapping, and I cannot change all references to "packages" to "webapp.[domain]." I also am not able in this instance to use an application-specific mapping for webapp. While any of these 3 options would circumvent the issue, I'm hoping someone has some insight...
The best I've got is to set argument type to "any" and then check isInstanceOf() inside the function... Seems like poor form.
Thanks,
Jen
Can you move the contents of the packages mapping to outside the webroot? This seems like the easiest way to fix it.
I'm using the decorator pattern to implement caching for my Repositories as such:
IFooRepository()
IFooRepository FooRepository()
IFooRepository CachedFooRepository(IFooRepository fooRepository)
The Cached repository checks the cache for the requested object and if it doesn't exist, calls the FooRepository to retrieve and store it. I'm currently registering these types with StructureMap using the following method:
For<IFooRepository>().Use<CachedFooRepository()
.Ctor<IFooRepository>().Use<FooRepository>();
This works fine, but as the number of cached repositories grows, registering each one individually is becoming unwieldy and is error prone. Seeing as I have a common convention, I'm trying to scan my assembly using a custom IRegistrationConvention, but I can't seem to figure out how to pass the FooRepository to the constructor of CachedFooRepository in the void Process(Type type, Registry registry) function.
I've found examples to do something like:
Type interfaceType = type.GetInterface(type.Name.Replace("Cached", "I"));
registry.AddType(interfaceType, type);
or
Type interfaceType = type.GetInterface(type.Name.Replace("Cached", "I"));
registry.For(interfaceType).Use(type);
But neither method will allow me to chain the .Ctor. What am I missing? Any ideas?