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Design Approach and Using Reflection to run methods in Java

I have a question. I have multiple classes in a package: Let's say package is
com.myPackage.first
And this package has the following classes:
firstGood
secondGood
thirdBad
fourthGood
Each of these classes have a method with the same name but different implementation. So say each have a one particular function called:
public void runMe(){
}
For now I want to come up with a way to given a class name, it'll go inside the class and run that particular method.
So conceptually, my method will look like those:
ArrayList<Class> classList ; // where classList is a list of classes I want to run
public void execute(){
for(Class c : classList){
// Go inside that class, (maybe create an intance of that class) and run the method called run me
}
}
or
public void execute(Class c, String methodToRun){
for(Class c : classList){
// Go inside that class, (maybe create an intance of that class) and run the method called run me
}
}
For now. what I have been able to do is get the name of the classes I want to run the
runMe()
method. So I have been able to come with a way to get the arraylist of classes I want to run. So what I need help with is coming up with a method such that it takes a class name and run the method I want it to. Any help is appreciated. Thanks

I suggest having a look at Class.forName ( ... ) to get the class object, Class.newInstance(); if your classes have a default constructor (or Class.getDeclaredConstructor(...) otherwise) to create a new instance and then Class.getDeclaredMethod( ... ) to find the method and invoke it.
All of this without any regard if your idea is really a good one, since I really didn't quite understand WHY you want to do what you want to do...

interface Me {
void runMe();
}
Then let all classes implement Me.
And have a list of Mes
List<Class<Me>> ...
Then
void test(Class<Me> cl) {
Me me = cl.newInstance();
me.runMe();
}

My adage is always use reflection to solve a problem - now you have two problems. In view of that have you considered a simple pattern like this:
interface Runner {
public void runMe();
}
static abstract class BaseRunner implements Runner {
public BaseRunner() {
// Automagically register all runners in the RunThem class.
RunThem.runners.add(this);
}
}
class FirstGood extends BaseRunner implements Runner {
#Override
public void runMe() {
System.out.println(this.getClass().getSimpleName() + ":runMe");
}
}
class SecondGood extends BaseRunner implements Runner {
#Override
public void runMe() {
System.out.println(this.getClass().getSimpleName() + ":runMe");
}
}
static class RunThem {
static final Set<Runner> runners = new HashSet<>();
static void runThem() {
for (Runner r : runners) {
r.runMe();
}
}
}
public void test() {
Runner f = new FirstGood();
Runner s = new SecondGood();
RunThem.runThem();
}
Here all of your runMe objects extend a base class whose constructor installs the object in a Set held by the class that calls their runMe methods.

inline
void execute() throws Exception{
for (Class<?> c : classesList)
{
//If you don't already have an instance then you need one
//note if the method is static no need for any existing instance.
Object obj = Class.forName(c.getName());
// name of the method and list of arguments to pass
Method m = c.getDeclaredMethod(methodName,null);
//method accessibility check
if(!m.isAccessible())
m.setAccessible(true);
//invoke method if method with arguements then pass them as new Object[]{arg0...} instead of null
//if method is static then m.innvoke(null,null)
m.invoke(obj, null);
}
}

I would recommend using an Interface that defines the runMe() method and then have all your classes implement that interface. Then you would have a list of this Interface:
List<MyInterface> classes = new ArrayList<MyInterface>();
Then you could easily iterate over it and invoke "runMe()" on all of them or if you only want to invoke it for instances of a certain class you could do it like this:
public void execute(Class classForWhichToExecute) {
for (MyInterface myInterface : classes) {
if (classForWhichToExecute.isAssignableForm(myInterface)) {
myInterface.runMe();
}
}
}
Of course this wouldn't work if your method is a static method - so adding more information from your side would help.

I would suggest to use an interface with a common method to override in each class. So that any class can be casted to interface and use its method to execute the method.
interface GoodAndBad{
public void runMe();
}
Implemented class
class FirstGood implements GoodAndBad{
#override
public void runMe(){
// Code to be executed
}
}
You can use execute() method as follows
public void execute(List<GoodAndBad> classList){
for(GoodAndBad c : classList){
c.runMe();
// Go inside that class, (maybe create an intance of that class) and
// run the method called run me
}
}
Change the Class to GoodAndBad interface to change the other method too.
This is loosely coupling objects to support favor over composition in Java Object Oriented Design Patterns.
Never use Strings of method names to execute a method at anytime. There are plenty of other cool solutions for that using design patterns.

How should I mock out a single method inside an object I'm trying to test?

I have a problem with a class that I am testing where in almost every method I want to test, one of the first things each method does is call this one specific method. This method that is called once by all of these other methods takes a long time to execute. I don't want to have to wait for this every time I run my tests, it really is just a huge waste of time.
I attempted to #Spy the method using Mocktio, but I ran into problems because the really long method doesn't return anything. Can someone suggest a good way to mock out a single method inside a class I am trying to test?
Example:
public class myClass {
public void methodOne() {
reallyLongMethod();
// More code
}
public void methodTwo() {
reallyLongMethod();
// More code
}
.
.
.
public void methodN() {
reallyLongMethod();
// More code
}
public void reallyLongMethod() {
}
}
This is the class I am trying to test. I want to test all of the 'methodX()' methods. I don't want to run reallyLongMethod everysingle time however.
So, is there a way to use Mockito 'Spy' to stub out reallyLongMethod()? Even though it doesn'treturn anything?

You can use a Spy with doNothing(), but make sure you use the spy during the test. Mockito spies copy the original, instead of delegating to it.
#RunWith(MockitoJUnitRunner.class)
public class YourTest {
// Option 1:
// #Spy MyClass myClass = new MyClass();
// Option 2 (see #Before method)
MyClass myClass;
#Before public void ignoreReallyLongMethod() {
myClass = spy(new MyClass()); // discard original
doNothing().when(myClass).reallyLongMethod();
}
#Test public void methodOneWorks() {
myClass.methodOne(); // you're using the spy here
assertEquals(42, myClass.getFoo());
}
}
Though this does evoke a code smell, don't mock or stub the class under test, as long as you're careful to test the method behavior (methodOne) and not the stubbed behavior (reallyLongMethod) you'll be good to go. If you do want to test reallyLongMethod you'll want to use a different object instance or else you'll "test" the doNothing() call alone. Do bear in mind that if reallyLongMethod and your other methods have any negative interactions, these tests won't tell you about that.
By the way, you can also do the equivalent without using Mockito, which may make a little clearer what you are or aren't doing with your mocks:
#RunWith(JUnit4.class)
public class YourTest {
MyClass myClass;
#Before public void createMyClass() {
myClass = new MyClass() { // create an anonymous inner class
#Override public void reallyLongMethod() {} // that does nothing here
};
}
}

easymock - mocking to use anyObject as parma of void setter method

Using EasyMock, how can I create the mock of the following class's process method? I want to create a mock which can accept any object of type MyObject.class.
public class Custom {
public void process(MyObject obj){
//code
}
}
I know how to do it if the method returns something, but with a void method I am not able to get my head around it.

Here's how to expect a call on a void method
Custom mock = EasyMock.createMock(Custom.class); // create the mock
mock.process(EasyMock.anyObject(MyObject.class)); // invoke the method
EasyMock.expectLastCall(); // register it as expected
EasyMock.replay(mock); // set the state
mock.process(new MyObject()); // invoke the method in the test
EasyMock.verify(mock); // verify the call

In order to mock a void method you simply call it on the mock object before calling replay.
#Test
public void testSomething() {
Custom mock = createMock(Custom.class);
mock.process(any(MyObject.class);
replay(mock);
// Your test comes here
// Optional - check the process was called
verify(mock);
}

Use Mockito to Stub methods in the same class as the class under test (CUT)

I am trying to test some legacy code using Mockito, and the method is a of type void.
I have stubbed out a lot of the calls to methods in other classes, this works fine.
However, I also need to be able to stub out certain calls to other methods inside the same class.
Currently this is not working.
e.g. My Class is like below:
public class Test {
public Test(dummy dummy) {
}
public void checkTask(Task task, List <String> dependencyOnLastSuccessList) throws TaskException {
callToOtherClass.method1 // This works fine, I can stub it using mockito
updateAndReschedule(Long id, String message) // call to method in same class, I cannot stub it
}
public void updateAndReschedule(Long id, String message) {
//method logic.....
}
}
This is my testClass showing what I have at the minute:
#Test
public void testMyMethod() {
Test testRef = new Test(taskJob);
Test spy = spy (testRef);
// when a particular method is called, return a specific object
when(callToOtherClass.method1).thenReturn(ObjectABC);
//doNothing when my local method is called
doNothing().when(spy).updateAndReschedule(1, "test");
//make method call
spy.checkTask(ts, taskDependencies);
}

You should instantiante testRef as follows:
Test testRef = new Test(taskJob) {
public void updateAndReschedule(Long id, String message) {
//do nothing
}
};
No need for the spy.

In my opinion the spy object instead of mock.
Spy is a mock created as a proxy to an existing real object; some methods can be stubbed, while the unstubbed ones are forwarded to the covered object
The spy is more elegant than anonymous implementation of chosen methods
Look at the example:
Mockito: Trying to spy on method is calling the original method
the nice article about mockito You can read
http://refcardz.dzone.com/refcardz/mockito

Mocking static method that is called multiple times

I have a static method, that is used in multiple places, mostly in static initialization block. It takes a Class object as parameter, and returns the class's instance.
I want to mock this static method only when particular Class object is used as parameter. But when the method is called from other places, with different Class objects, it returns null.
How can we have the static method execute actual implementation in case of parameters other than the mocked one?
class ABC{
void someMethod(){
Node impl = ServiceFactory.getImpl(Node.class); //need to mock this call
impl.xyz();
}
}
class SomeOtherClass{
static Line impl = ServiceFactory.getImpl(Line.class); //the mock code below returns null here
}
class TestABC{
#Mocked ServiceFactory fact;
#Test
public void testSomeMethod(){
new NonStrictExpectations(){
ServiceFactory.getImpl(Node.class);
returns(new NodeImpl());
}
}
}

What you want is a form of "partial mocking", specifically dynamic partial mocking in the JMockit API:
#Test
public void testSomeMethod() {
new NonStrictExpectations(ServiceFactory.class) {{
ServiceFactory.getImpl(Node.class); result = new NodeImpl();
}};
// Call tested code...
}
Only the invocations that match a recorded expectation will get mocked. Others will execute the real implementation, when the dynamically mocked class is called.