Groovy: Delegate instance method to meta class - groovy

I'm findind a way easier to implement this kind of feature:
RESTClient client = new RESTClient("https://api.github.com", JSON)
class CoreApi {}
RESTClient.methods*.name.each { name ->
if (! CoreApi.methods.contains(name)) {
CoreApi.metaClass.static."$name" = {Object... args -> client."$name"(*args)}
}
}
and then we can use CoreApi.get(path: "/users/your-user")
Is there any annotation available in groovy for implement this kind of behaviour? What's it called?

You are looking for #Delegate
class CoreApi {
#Delegate RESTClient client
}
But it doesn't work for static methods
Static methods, synthetic methods or methods from the GroovyObject interface are not candidates for delegation

Related

IoC container struggles with generics

I have an existing program with some plugin infrastructure that currently relies on plugin classes having parameterless constructors. I'd like to offer plugin authors the opportunity to just require some infrastructure from my program by specifying parameters for the constructor.
Internally, I use some generic wrapper class to encapsulate the plugin's classes and to make them behave to the rest of my program like older pre-plugin era internal classes.
I have some placeholder here representing my infrastructure:
public interface IInfrastructure
{
}
public class Infrastructure : IInfrastructure
{
}
Some plugin interface specification:
public interface IPlugin
{
}
the plugin implementation requiring my infrastructure:
public class Plugin : IPlugin
{
public Plugin(IInfrastructure _)
{
}
}
and my generic wrapper class expecting some plugin class
public class PluginWrapper<TImpl> where TImpl: class, IPlugin
{
public PluginWrapper(TImpl _)
{
}
}
After registering the involved types:
ServiceLocator.Default.RegisterType<IInfrastructure, Infrastructure>(RegistrationType.Transient);
ServiceLocator.Default.RegisterType(typeof(Plugin),typeof(Plugin), RegistrationType.Transient);
var wrapperType = typeof(PluginWrapper<>).MakeGenericType(typeof(Plugin));
ServiceLocator.Default.RegisterType(wrapperType, wrapperType,RegistrationType.Transient);
I find out that I can resolve the "inner" plugin type:
Assert.NotNull(ServiceLocator.Default.ResolveType<Plugin>());
but I can't resolve the "Wrapper" type.
Assert.NotNull(ServiceLocator.Default.ResolveType<PluginWrapper<Plugin>>());
Am I hitting a limitation of Catel's IoC container, or am I doing something wrong?
When not using the generic registration method, I passed the registration type in the position of the "tag" parameter by accident.
So, changing the registration part to this version:
ServiceLocator.Default.RegisterType<IInfrastructure, Infrastructure>(RegistrationType.Transient);
ServiceLocator.Default.RegisterType(typeof(Plugin),typeof(Plugin),registrationType:RegistrationType.Transient);
var wrapperType = typeof(PluginWrapper<>).MakeGenericType(typeof(Plugin));
ServiceLocator.Default.RegisterType(wrapperType, wrapperType, registrationType:RegistrationType.Transient);
fixes the problem and everything goes as expected.

Mock constructor of a class

I am writing test class for my java class. I am using Junit5 with Mockito.
I am using Junit5 which isnt compatible with Power Mockito so I am using Mockito only.
I have class Emp which have function findSalary like below and EmpProfileClient is initialized at constructor.
Class Emp {
......
public void findSalary(empId) {
...
TaxReturn taxReturn = new TaxReturn(EmpProfileClient);
int value = taxReturn.apply(new TaxReturnRequest.withEmpId(empId))
.returnInRupee();
...
}
}
When I am writing the test case, I mocked EmpProfileClient, but since we are creating TaxReturn in a method, How I can mock TaxReturn.apply so I can write the expectation to get the value as per my choice which I set in the test class?
If you want to mock this, the TaxReturn class should be an injected bean in the Emp class. Add an injection framework (like Spring) and inject the TaxReturn class. In the test you write you can inject a Mock instead of the real class. See #InjectMocks annotation of the mockito framework.
If I understood your question correctly(you are looking for mocking taxReturn.apply) I'd suggest next:
First. Refactor your taxReturn instantiation(as it is would be much easier to mock method behavior in comparison for trying to mock local variable)
public class EmpService {
public int findSalary(Integer empId) {
//...
// It's doesn't matter what the actual empProfileClient type is
// as you mocking creation behavior anyway
Object empProfileClient = null;
TaxReturn taxReturn = createClient(empProfileClient);
int value = taxReturn.apply(new TaxReturnRequest().withEmpId(empId))
.returnInRupee();
//...
return value; // or whatever
}
protected TaxReturn createClient(Object empProfileClient) {
return new TaxReturn(empProfileClient);
}
}
Second. Use Mockito.spy() in your test:
class EmpServiceTest {
#Test
void findSalary() {
TaxReturn taxReturn = Mockito.mock(TaxReturn.class);
// this is the main idea, here you using partial EmpService mock instance
// part is mocked(createClient()) and other part(findSalary()) is tested
EmpService service = Mockito.spy(EmpService.class);
when(service.createClient(any())).thenReturn(taxReturn);
when(taxReturn.apply(any(TaxReturnRequest.class))).thenReturn(taxReturn);
int yourExpectedValue = 5;
when(taxReturn.returnInRupee()).thenReturn(yourExpectedValue);
assertEquals(yourExpectedValue, service.findSalary(0));
}
}
Keep in mind that any(), spy(), when() and mock() methods are part of Mockito API. So there is nothing hidden here

JukitoRunner, bind mock of final class

How to bind mock of final class in Jukito ?
For example :
public final class SomeFinalClass(){
public SomeFinalClass(String someString){
}
}
//Testing class
#Runwith(JukitoRunner.class)
public class TestingClass(){
#Inject
private SomeFinalClass someFinalClassMock;
public static class TestModule extends JukitoModule {
#Override
protected void configureTest() {
// bind(SomeClient.class).in(TestSingleton.class);
}
#Provides
public SomeFinalClass getSomkeFinalClass() {
return Mokito.mock(SomeFinalClass.class); //throws error
}
}
}
Is there a way i can use PowerMockito with JukitoRunner ?
You can mock a final class if you're using Mockito 2. From Mockito 2 Wiki:
Mocking of final classes and methods is an incubating, opt-in feature. It uses a combination of Java agent instrumentation and subclassing in order to enable mockability of these types. As this works differently to our current mechanism and this one has different limitations and as we want to gather experience and user feedback, this feature had to be explicitly activated to be available ; it can be done via the mockito extension mechanism by creating the file src/test/resources/mockito-extensions/org.mockito.plugins.MockMaker containing a single line: mock-maker-inline.
After you created this file, Mockito will automatically use this new engine and one can do :
final class FinalClass {
final String finalMethod() { return "something"; }
}
FinalClass concrete = new FinalClass();
FinalClass mock = mock(FinalClass.class);
given(mock.finalMethod()).willReturn("not anymore");
assertThat(mock.finalMethod()).isNotEqualTo(concrete.finalMethod());

Parameter specified as non-null is null when using Mokito anyObject() on Kotlin function

My code as below, refering to the solution in https://stackoverflow.com/a/30308199/3286489
import org.mockito.Mock
import org.mockito.Mockito
import org.mockito.MockitoAnnotations
import org.mockito.Mockito.*
class SimpleClassTest {
private fun <T> anyObject(): T {
Mockito.anyObject<T>()
return uninitialized()
}
private fun <T> uninitialized(): T = null as T
lateinit var simpleObject: SimpleClass
#Mock lateinit var injectedObject: InjectedClass
#Before
fun setUp() {
MockitoAnnotations.initMocks(this)
}
#Test
fun testSimpleFunction() {
simpleObject = SimpleClass(injectedObject)
verify(injectedObject).settingDependentObject(anyObject())
}
}
I still have the below error
java.lang.IllegalArgumentException: Parameter specified as non-null is null: method my.package.InjectedClass.settingDependentObject, parameter dependentObject
Did I miss anything?
UPDATED
Below is the code tested (simplest form and working)
class SimpleClass(val injectedClass: InjectedClass) {
fun simpleFunction() {
injectedClass.settingDependentObject(DependentClass(Response.Builder().build()))
}
}
open class DependentClass(response: Response) {
}
open class InjectedClass() {
lateinit var dependentObject: DependentClass
fun settingDependentObject(dependentObject: DependentClass) {
this.dependentObject = dependentObject
}
}
By default Kotlin classes and members are final. Mockito cannot mock final classes or methods.
Thus when you write:
verify(injectedObject).settingDependentObject(anyObject())
the real implementation is called which requires non null argument.
To fix that either open your class and method or, even better, change SimpleClass to accept an interface as its constructor argument and mock the interface instead.
There is a project specifically to help deal with Kotlin "closed by default" in unit testing with Mockito. For JUNIT, you can use the kotlin-testrunner which is an easy way to make any Kotlin test automatically open up classes for testing as they are loaded by the classloader. Usage is simple, just add one annotation of #RunWith(KotlinTestRunner::class), for example:
#RunWith(KotlinTestRunner::class)
class MyKotlinTestclass {
#Test
fun test() {
...
}
}
This is thoroughly covered in the article Never say final: mocking Kotlin classes in unit tests
This covers your use case in an automatic way by allowing all classes to be mocked that otherwise would not be allowed.
I ran into the same issue with Mockito when using RETURNS_DEEP_STUBS. It seems like nulls are still returned for nested objects, even when using the kotlin-allopen plugin.
Please check out and comment on this issue on Mockito if you're having the same problem.
You can use this function instead
inline fun <reified T : Any> any(): T = Mockito.any(T::class.java) ?: T::class.java.newInstance()

groovy: variable scope in closures in the super class (MissingPropertyException)

I have the impression that closures run as the actual class being called (instead of the implementing super class) and thus break when some variables are not visible (e.g. private in the super class).
For example
package comp.ds.GenericTest2
import groovy.transform.CompileStatic
#CompileStatic
class ClosureScopeC {
private List<String> list = new ArrayList<String>()
private int accessThisPrivateVariable = 0;
void add(String a) {
list.add(a)
println("before ${accessThisPrivateVariable} ${this.class.name}")
// do something with a closure
list.each {String it ->
if (it == a) {
// accessThisPrivateVariable belongs to ClosureScopeC
accessThisPrivateVariable++
}
}
println("after ${accessThisPrivateVariable}")
}
}
// this works fine
a = new ClosureScopeC()
a.add("abc")
a.add("abc")
// child class
class ClosureScopeD extends ClosureScopeC {
void doSomething(String obj) {
this.add(obj)
}
}
b = new ClosureScopeD()
// THIS THROWS groovy.lang.MissingPropertyException: No such property: accessThisPrivateVariable for class: comp.ds.GenericTest2.ClosureScopeD
b.doSomething("abc")
The last line throws a MissingPropertyException: the child class calls the "add" method of the super class, which executes the "each" closure, which uses the "accessThisPrivateVariable".
I am new to groovy, so I think there must be an easy way to do this, because otherwise it seems that closures completely break the encapsulation of the private implementation done in the super class ... this seems to be a very common need (super class implementation referencing its own private variables)
I am using groovy 2.1.3
I found this to be a good reference describing how Groovy variable scopes work and applies to your situation: Closure in groovy cannot use private field when called from extending class
From the above link, I realized that since you have declared accessThisPrivateVariable as private, Groovy would not auto-generate a getter/setter for the variable. Remember, even in Java, private variables are not accessible directly by sub-classes.
Changing your code to explicitly add the getter/setters, solved the issue:
package com.test
import groovy.transform.CompileStatic
#CompileStatic
class ClosureScopeC {
private List<String> list = new ArrayList<String>()
private int accessThisPrivateVariable = 0;
int getAccessThisPrivateVariable() { accessThisPrivateVariable }
void setAccessThisPrivateVariable(int value ){this.accessThisPrivateVariable = value}
void add(String a) {
list.add(a)
println("before ${accessThisPrivateVariable} ${this.class.name}")
// do something with a closure
list.each {String it ->
if (it == a) {
// accessThisPrivateVariable belongs to ClosureScopeC
accessThisPrivateVariable++
}
}
println("after ${accessThisPrivateVariable}")
}
}
// this works fine
a = new ClosureScopeC()
a.add("abc")
a.add("abc")
// child class
class ClosureScopeD extends ClosureScopeC {
void doSomething(String obj) {
super.add(obj)
}
}
b = new ClosureScopeD()
b.doSomething("abc")
There is a simpler way, just make the access modifier (should rename the property really) to protected, so the sub-class has access to the property.. problem solved.
protected int accessThisProtectedVariable
To clarify on your statement of concern that Groovy possibly has broken encapsulation: rest assured it hasn't.
By declaring a field as private, Groovy is preserving encapsulation by intentionally suspending automatic generation of the public getter/setter. Once private, you are now responsible and in full control of how or if there is a way for sub-classes (protected) or all classes of objects (public) to gain access to the field by explicitly adding methods - if that makes sense.
Remember that by convention, Groovy ALWAYS calls a getter or setter when your codes references the field. So, a statement like:
def f = obj.someField
will actually invoke the obj.getSomeField() method.
Likewise:
obj.someField = 5
will invoke the obj.setSomeField(5) method.

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