This question is being asked everywhere on Google but I'm still having trouble with it. Here is what I'm trying to do. So like my title states, I'm getting an 'object is not an instance of declaring class' error. Any ideas? Thanks!
Main.java
Class<?> base = Class.forName("server.functions.TestFunction");
Method serverMethod = base.getMethod("execute", HashMap.class);
serverMethod.invoke(base, new HashMap<String, String>());
TestFunction.java
package server.functions;
import java.util.HashMap;
import java.util.Map;
import server.*;
public class TestFunction extends ServerBase {
public String execute(HashMap<String, String> params)
{
return "Test function successfully called";
}
}
You're invoking the method with the class, but you need an instance of it. Try this:
serverMethod.invoke(base.newInstance(), new HashMap<String, String>());
You are trying to invoke the execute method on the object base, which is actually a Class object returned by your Class.forName() call.
This would work for a static (class) method - but execute is a non-static (instance) method.
(It would also work for calling an instance method of an object of type Class - but that's not what you are trying to achieve here!)
You need an actual instance of TestFunction to invoke the method on, or you need to make the method static.
When invoking a static method by reflection, the first argument to invoke() is ignored, so it is conventional to set it to null, which clarifies the fact that there's no instance involved.
Although your current example method would do the same thing for any TestFunction object, in general an instance method could produce a different result for each object - so the .invoke() reflection method needs to know which object to run the method on.
Related
I need to create a custom classes based on some input. What I have atm is this:
final Class service = ...;
final Method method = ...;
final DynamicType.Unloaded unloadedType = new ByteBuddy()
.subclass(Object.class)
.name(service.getClass().getSimpleName() + "DynamicResolver")
.defineMethod(
endpointName,
resolveReturnType(method),
Modifier.PUBLIC)
.withParameters(parameters)
.intercept(MethodDelegation
.withDefaultConfiguration()
.withBinders(Morph.Binder.install(Morphing.class))
.to(interceptor).andThen(
MethodCall.invoke(method).on(service).withArgument(arguments)
))
.make()
What I am doing here is creating a class with a single method that delegates to provided one. However, the created method and delegate method have a bit different parameters. The created method has one argument more (in parameters). The created method does not take that argument, hence the arguments array with argument indexes (one argument less).
So far it's OK. Now, I need to add additional argument when calling delegation method. For the sake of simplicity of the example, imagine we have to add one more string to delegate call.
As I saw from the documentation, the way to manipulate the arguments is using #Morph. So I did:
public interface Morphing<T> {
T invoke(Object[] args);
}
and my interceptor:
public class Interceptor {
#RuntimeType
public Object invoke(
#Morph final Morphing<Integer> m,
#AllArguments final Object[] args
) {
System.out.println("!!!");
return m.invoke(args);
}
}
Unfortunately, this is not working. When I remove the #Morph argument, the interceptor gets called.
What am I missing here?
EDIT: Is the #Morph used only for subclasses and not when delegating to another instance?
EDIT2: example
Byte Buddy is binding a method of the Object class such that your desired interceptor is no longer triggered. You can add filter(isDeclaredBy(MyInterceptor.class)) after the withDefaultConfiguration() to avoid this. Doing so, you will get an exception that Byte Buddy cannot bind any of your methods.
The reason that #Morph makes the class ineligable is that there is no super method to be called. In your example, you are defining a new method which does not have an original implementation. You'd need to override an existing method to use the annotation.
I'm writing an application that has an instance of a class that contains the esper engine. There are a number of instance variables that I would like to read and set using instance method calls from the EPL in the engine. I don't get any compilation errors and the code runs. But the instance method is not called.
epl statements:
module myModule;
create variable com.tp.main.MyClass myClass;
select myProperty from MyEvent unidirectional, method:myClass.getMyProperty() as myProperty;
A hint could be that if I don't use the method: key word in front of the method call I get an error that myClass.getMyProperty class could not be found. The documentation sometimes uses the method: key word and sometimes not in the examples for calling instance methods from Class-type variables.
I have also tried using the addVariable method in the API with the same results.
code for the method.
public Result getMyProperty() {
Result result = new Result();
result.setResult("propertyValue");
logger.info("This method was called");
return result;
}
The class Result is a POJO with getter and setter for a string.
public class Result {
private String result;
public String getResult() {
return result;
}
public void setResult(String str) {
result = str;
}
}
What am I missing?
You could look at a regression test class. The specific one you may want to look at is ExecFromClauseMethodVariable. Maybe your code does not assign a value to the variable?
Github:
https://github.com/espertechinc/esper/blob/3e396d77308532b202ee452100eaaf9e7a044906/esper-regression/src/test/java/com/espertech/esper/regression/epl/fromclausemethod/ExecFromClauseMethodVariable.java
Problem solved and I thought it might be useful to share the solution. Credit to user650839 who pointed me in the right direction. Here is what ended up fixing the problem.
I reverted back to declaring the variable in the runtime configuration API. I found that I must register the variable class, initialize it with the instance object (this) and finally import the class. Here is the snippet of code that does this configuration in the runtime configuration API.
Configuration configuration = new Configuration();
configuration.addVariable("myClass", com.tp.main.MyClass.class, this);
configuration.addImport(com.tp.main.MyClass.class);
epService = EPServiceProviderManager.getProvider(trade.getTradeName(), configuration);
It seems there is a limitation when declaring the Class variable in the EPL. You cannot initialize it with the instance object you want to use. In the runtime configuration API I was able to initialize it with "this" instance of the object which contains all of the instance variables I want to access from the EPL.
The EPL statement did not change. However, it does seem that you must use the key word method: in front of the method call or you get an error "cannot find class..."
I have a Java class package.SStream where I have implemented the method getValue() which returns a JavaPairDStream<String, Integer>
I want to use this method in Scala's main method
I've imported the class package.SStream in Scala
and when I try to call the method like this in Scala
val x = SStream.getValue()
I get this error :
[error] value getValue is not a member of object package.SStream
That error sounds like your getValue() is not a static method.
Is it defined as a static method or an instance method in your package.SStream class?
I am sure this is quite a common question now, but I really can't get away with this issue I am having on mocking private method which internally calls another method and returns a collection.
Class that I am testing has a public method which calls private method to get Collection object. I use PowerMock to create a spy of private method.
public void method1(String s)
{
Collection<Object> list = invokePrivate()
}
private Collection<Object> invokePrivate()
{
Wrapper wrapperObj = Factory.getInstance.getWrapper();
Collection<Object> list = wrapperObj.callWrapperMethod(); // This always calls into real method, instead of mocked version.
return list;
}
Test Class-:
So In order to test public method "method1" I create a spy using PowerMockito to spy over private method and return a demo list.
MainClass obj = new MainClass();
MainClass spy = PowerMockito.spy(obj);
PowerMockito.when(spy, method(MainClass.class, "inokePrivate"))
.thenReturn(list); // demo list which exists as a test class member.
Above calls into private method which in turns tries to call wrapperObj.callWrapperMethod() which resides in a different artifact and breaks there because some implementation it doesn't find there.
So I try to mock wrapperObj.callWrapperMethod.
WrapperClass wr = new WrapperClass();
WrapperClass spy1 = PowerMockito.spy(wr);
when(spy1.callWrapperMethod()).thenReturn(list) // demo list which exists as a test class member.
Above mocking again calls into actual implementation of callWrapperMethod() and breaks in there.
How can I prevent calling into actual implementation of wrapper method?
Few of the answers that helped me-:
Mockito:How to mock method called inside another method
Testing Private method using mockito
[UPDATE] -: as suggested as I did following-:
PowerMockito.doReturn(list).when(spy1).callWrapperMethod(); // This returns me demo list successfully.
But now when I call private method from PowerMockito control goes into invokePrivate method and again tries to call original callWrapperMethod instead of return list from spy version.
I suggest to not do it this way. Your private method should not retrieve the singleton factory object using a static method.
Static stuff breaks "easy" mocking; forces you to use "power" mocking; and thereby, creates more problems than it solves.
Change your code to use dependency injection. Do something like this:
class YourClass {
private final Factory factory;
public YourClass() {
this(Factory.getInstance(); }
YourClass(Factory theFactory) {
this.factory = theFactory;
...
This will allow you to use the second constructor in your unit test; to provide a (easily mocked) factory object for your class. Thereby you eliminate the whole need for PowerMock.
Long story short - when code is hard to test; change the code; and not the test. As a side effect, you are improving the quality of your code - because you loose the hard dependency on that singleton object.
And just to be complete: I also recommend to avoid "breaking" the Law of Demeter ( http://en.wikipedia.org/wiki/Law_of_Demeter ): if your class needs the wrapper; then it should hold a wrapper object; if it needs that factory; then it should hold a factory object. But you should not hold one object ... to retrieve another object from there, to run something on that second object. As you see - doing so leads exactly to the sort of problem that you are facing.
My previous post was not very clear, sorry for that. I will try to give a better example of what I am trying to do.
I have an Java application that will load .class files and runs them in a special enviroment (the Java app has built-in functions) Note: This is not a library.
That Java application will then display an applet, and I want to modify the variables in the applet.
The main class of the applet is called 'client'.
The Java application will load the applet by creating an new instance of class 'client'.
I already got access to the 'client' class. the Java application will put the applet in a variable:
Applet client = (Applet) loadedClientClass.newInstance();
So I did this:
Class<?> class_client = client.getClass();
I can now read and set the fields but the 'client' class will call a funation of an other class, like this:
otherClass.someVoid(false);
And if I try something like:
class_client.getDeclaredMethod("otherClass.someVoid",boolean.class);
It will fail, saying that the function can not be found.
'otherClass' is the direct class name, it is not a reference to a new instance of the class as far as I know.
Is there any way to get 'otherClass.someVoid'?
You're using getDeclaredMethod like a static method (expecting it to return methods from any class), but it only returns method from the class itself. Here's how you can call otherClass.someVoid(false).
Class<?> otherClass = Class.forName("com.xyz.OtherClass"); // Get the class
Method method = otherClass.getDeclaredMethod("someVoid", boolean.class);
// If the method is an Class (ie static) method, invoke it on the Class:
method.invoke(otherClass, false);
// If the method is an instance (ie non-static) method, invoke it on an instance of the Class:
Object otherInstance = otherClass.newInstance(); // Get an instance of other class - this approach assumes there is a default constructor
method.invoke(otherInstance, false);
If the class isn't initialized, the var someInteger doesn't exist. It's a member variable, so it only exists inside of instances of the class. So, you can't change it since it's doesn't exist. Now, if you made it a static variable, then you could change it.
Is there any way to change 'otherClass.someInteger' through the
'mainClass' class?
No.
But you can get it via OtherClass' class via Class.forName:
Class<?> theOtherClazz = Class.forName("OtherClass");
And then get the methods via theOtherClazz.getDeclaredMethod