I got a method that does the following:
private void computeHierarchie(GlobalKey key) {
HierarchieValue hierarchieValue = hierarchieFactory.createHierarchie(selectedKey);
....
}
GlobalKey has 4 childs: KeyA, KeyB, KeyC and KeyD.
At the moment my factory looks like the following:
public class HierarchieFactory {
// inject someFacade which has 4 different methods
public HierarchieValue createHierarchie(GlobalKey key) {
if (key instanceof KeyA) {
return someFacade.computeHierarchie((KeyA) key);
}
if (key instanceof KeyB) {
return someFacade.computeHierarchie((KeyB) key);
}
if (key instanceof KeyC) {
return someFacade.computeHierarchie((KeyC) key);
}
if (key instanceof KeyD) {
return someFacade.computeHierarchie((KeyD) key);
}
return new HierarchieValue();
}
}
I really don't like this switch-case thing, but to be honest, I can't compute any worthy refactoring. I tried something like the following:
public abstract class AbstractHierarchieFactory {
//inject someFacade
abstract <T extends GlobalKey> HierarchieValue createHierarchie(T key);
}
And then the 4 classes extending this one. One would look like:
public class KonzernHierarchieFactory extends AbstractHierarchieFactory {
#Override
HierarchieValue createHierarchie(KonzernKey konzernKey) {
return evaFacade.computeHierarchie(konzernKey);
}
}
This would be so nice!
But sadly this doens't work. Do you have any other suggestions? There must be a standard way to solve this problem.
This seems like a prime example for a Visitor pattern.
e.g. let's say you have a KeyVisitor interface with the methods visitA(KeyA key), …, visitD(KeyD key). Then you can code the a method into your Key classes (which must obviously also available from a common base class):
void visit(KeyVisitor visitor) { visitor.visitX(this); }
Where you replace the X with your A..D, depending on class. Now your factory can implement KeyVisitor and handle your key classes separately.
Related
I am trying to use mapstruct to transform an object as below
Source
MainObject
{
String key;
List<ChildObject> children;
}
ChildObject{
String childVar1;
String childVar2;
}
Target
List<TargetObj> targetObjects;
TargetObj{
String key;
String var1;
String var2;
}
I need to prepare a list of TargetObj instances with the key mapped from the key from MainObject and var1 and var2 mapped from ChildObject.
I tried to use ObjectFactory and Decorator as mentioned in the mapstruct documentation. But couldn't find a way to get this done. Both cases I got an error which states cannot return iterable object from non iterable parameters.
You can try and use a combination of #BeforeMapping or #AfterMapping with the #Context.
Your mapper can look like:
#Mapper
public interface MyMapper {
default List<TargetObj> map(MainObject source) {
if (source == null) {
return Collections.emptyList(); // or null or whatever you prefer
}
return map(source.getChildren(), new CustomContext(source));
}
List<TargetObject> map(List<ChildObject> children, #Context CustomContext context);
#Mapping(target = "key", ignore = true) // key is mapped in the context
TargetObject map(ChildObject child, #Context CustomContext context);
}
And the custom context would look something like:
public class CustomContext {
protected final MainObject mainObject;
public CustomContext(MainObject mainObject) {
this.mainObject = mainObject;
}
#AfterMapping // of #BeforeMapping
public void afterChild(#MappingTarget ChildObject child) {
child.setKey(mainObject.getKey());
// More complex mappings if needed
}
}
The goal is to do manual mapping from your MainObject to the List<TargetObj> by using other methods that MapStruct will generate
Assuming that we have an object with the following attributes:
public class MyObject {
private String attr1;
private Integer attr2;
//...
public String getAttr1() {
return this.attr1;
}
public Integer getAttr2() {
return this.attr2;
}
}
One way of sorting a list mylist of this object, based on its attribute attr1 is:
mylist.sort(Comparator.comparing(MyObject::getAttr1));
Is it possible to use this code inside a method in a dynamic way and replace the getAttr1 part with a method that returns the getter of an attribute of the object based on its name? Something like:
public void sortListByAttr(List<MyObject> list, String attr) {
list.sort(Comparator.comparing(MyObject::getGetterByAttr(attr)));
}
The MyObject::getGetterByAttr(attr) part does not compile, I wrote it just as an example to explain my idea
I tried to implement a method with the following code new PropertyDescriptor(attr, MyObject.class).getReadMethod().invoke(new MyObject()) but It's still not possible to call a method with a parameter from the comparing method
You could add a method like
public static Function<MyObject,Object> getGetterByAttr(String s) {
switch(s) {
case "attr1": return MyObject::getAttr1;
case "attr2": return MyObject::getAttr2;
}
throw new IllegalArgumentException(s);
}
to your class, but the returned function is not suitable for Comparator.comparing, as it expects a type fulfilling U extends Comparable<? super U> and while each of String and Integer is capable of fulfilling this constraint in an individual invocation, there is no way to declare a generic return type for getGetterByAttr to allow both type and be still compatible with the declaration of comparing.
An alternative would be a factory for complete Comparators.
public static Comparator<MyObject> getComparator(String s) {
switch(s) {
case "attr1": return Comparator.comparing(MyObject::getAttr1);
case "attr2": return Comparator.comparing(MyObject::getAttr2);
}
throw new IllegalArgumentException(s);
}
to be used like
public void sortListByAttr(List<MyObject> list, String attr) {
list.sort(getComparator(attr));
}
This has the advantage that it also may support properties whose type is not Comparable and requires a custom Comparator. Also, more efficient comparators for primitive types (e.g. using comparingInt) would be possible.
You may also consider using a Map instead of switch:
private static Map<String,Comparator<MyObject>> COMPARATORS;
static {
Map<String,Comparator<MyObject>> comparators=new HashMap<>();
comparators.put("attr1", Comparator.comparing(MyObject::getAttr1));
comparators.put("attr2", Comparator.comparing(MyObject::getAttr2));
COMPARATORS = Collections.unmodifiableMap(comparators);
}
public static Comparator<MyObject> getComparator(String s) {
Comparator<MyObject> comparator = COMPARATORS.get(s);
if(comparator != null) return comparator;
throw new IllegalArgumentException(s);
}
More dynamic is only possible via Reflection, but this would complicate the code, add a lot of potential error source, with only little benefit, considering that you need only to add one line of source code for adding support for another property in either of the examples above. After all, the set of defined properties gets fixed at compile time.
You could also have a single place where this comparators would be defined:
static enum MyObjectComparator {
ATTR1("attr1", Comparator.comparing(MyObject::getAttr1));
MyObjectComparator(String attrName, Comparator<MyObject> comparator) {
this.comparator = comparator;
this.attrName = attrName;
}
private final Comparator<MyObject> comparator;
private final String attrName;
private static MyObjectComparator[] allValues = MyObjectComparator.values();
public static Comparator<MyObject> findByValue(String value) {
return Arrays.stream(allValues)
.filter(x -> x.attrName.equalsIgnoreCase(value))
.map(x -> x.comparator)
.findAny()
.orElseThrow(RuntimeException::new);
}
}
And your usage would be:
public void sortListByAttr(List<MyObject> list, String attr) {
list.sort(MyObjectComparator.findByValue(attr));
}
I have an idea for a specific event handling based on generics, but seems like Weld can't handle them. I asked google but couldn't find an alternative CDI extension for this.
Question: is there a CDI extension, that can handle event propagation of generic-typed events?
In the following the explicit problem I have.
I have three general events, EntityCreated, EntityChanged and EntityDeleted. The base class for them is defined like this:
public abstract class DatabaseEvent<TargetType> {
public TargetType target;
public DatabaseEvent(TargetType target) {
this.target = target;
}
}
The events then are simple inherited classes:
public class EntityCreatedEvent<TargetType> extends DatabaseEvent<TargetType> {
public EntityCreatedEvent(TargetType target) {
super(target);
}
}
I fire them like this:
public abstract class MyHome<EntityType> {
private EntityType entity;
#Inject
Event<EntityCreatedEvent<EntityType>> entityCreatedEvent;
public void fireCreatedEvent() {
EntityCreatedEvent<EntityType> payload = new EntityCreatedEvent<EntityType>(entity);
entityCreatedEvent.fire(payload);
}
}
I want to observe them like this:
public void handleProjectCreated(#Observes EntityCreatedEvent<Project> event) { ... }
When launching the server Weld tells me it can't handle generic-typed events. The CDI-way of doing things would be to use additional qualifiers instead of the generics to distiguish them, e.g.:
public void handleProjectCreated(#Observes #ProjectEvent EntityCreatedEvent event) { ... }
However, I fire the events from that MyHome base class, where I can't just fire with the #ProjectEvent: it might not be a project but another type.
My solution up to now is to skip that typing altogether and handle them like this:
public void handleProjectCreated(#Observes EntityCreatedEvent event) {
if(event.target instanceof Project) { ... }
}
This solution is okay, but not perfect.
I guess you can do this with dinamically binding qualifier members. This is what your code would look like:
public abstract class MyHome {
private EntityType entity;
#Inject
Event<EntityCreatedEvent> entityCreatedEvent;
public void fireCreatedEvent() {
entityCreatedEvent.select(getTypeBinding()).fire(new EntityCreatedEvent(entity));
}
private TypeBinding getTypeBinding() {
return new TypeBinding() {
public Class<? extends EntityType> value() {return entity.getClass();}
};
}
#Qualifier
#Target({ PARAMETER, FIELD })
#Retention(RUNTIME)
public #interface EntityTypeQualifier {
Class<? extends EntityType> value();
}
public abstract class TypeBinding extends AnnotationLiteral<EntityTypeQualifier> implements EntityTypeQualifier {}
//Observers
public void handleEntityType1Created(#Observes #EntityTypeQualifier(EntityType1.class) EntityCreatedEvent event) {}
public void handleEntityType2Created(#Observes #EntityTypeQualifier(EntityType2.class) EntityCreatedEvent event) {}
As this CDI issue points it is not possible to fire an without having the type of T at runtime.
But, if you have the type of T (i.e. you have an instance) you can use the Event as an Instance, and select the event to be fired using a dynamic type literal.
Edit:
Perhaps a more concise way to ask this question is: Does Spring provide a way for me to resolve ambiguous candidates at injection time by providing my own listener/factory/decision logic?
In fact, arguably the #Environmental qualifier on the member field below is unnecessary: if an #Inject-ion is ambiguous... let me help? In fact, #ResolveWith(EnvironmentalResolver.class) would be alright too..
When Spring attempts to inject a dependency (using annotations) I understand that I need to #Qualifier an #Inject point if I am to have multiple components that implement that interface.
What I'd like to do is something like this:
class MyFoo implements Foo {
#Inject
#Environmental
private Bar bar;
}
#Environmental(Environment.Production)
class ProductionBar implements Bar {
}
#Environmental({Environment.Dev, Environment.Test})
class DevAndTestBar implements Bar {
}
I would expect that I need to create some kind of ambiguity resolver which would look something (vaguely) like this:
class EnvironmentalBeanAmbiguityResolver {
// set from configuration, read as a system environment variable, etc.
private Environment currentEnvironment;
public boolean canResolve(Object beanDefinition) {
// true if definition has the #Environmental annotation on it
}
public Object resolve(Collection<Object> beans) {
for (Object bean : beans) {
// return bean if bean #Environmental.values[] contains currentEnvironment
}
throw new RuntimeException(...);
}
}
One example of where this would be useful is we have a service that contacts end-users. Right now I just have a hacked together AOP aspect that before the method call to the "MailSender', checks for a "Production" environment flag and if it is not set, it sends the email to us instead of the users email. I'd like to instead of wrapping this in an AOP aspect specific to mail sending, instead be able to differentiate services based on the current environment. Sometime's it is just a matter of "production" or "not production" as I've demonstrated above, but a per-environment definition works too.
I think this can be reused for region too... e.g. #Regional and #Regional(Region.UnitedStates) and so on and so forth.
I'd imagine #Environmental would actually be a #Qualifier that way if you wanted to depend directly on something environmental you could (an #Environmental(Production) bean would likely depend directly on an #Environmental(Production) collaborator - so no ambiguity for lower level items --- same a #Regional(US) item would depend on other #Regional(US) items expiclitly and would bypass my yet-to-be-understood BeanAmbiguityResolver)
Thanks.
I think I solved this!
Consider the following:
public interface Ambiguity {
public boolean isSatisfiedBy(BeanDefinitionHolder holder);
}
#Target({ METHOD, CONSTRUCTOR, FIELD })
#Retention(RUNTIME)
public #interface Ambiguous {
Class<? extends Ambiguity> value();
}
#Target(TYPE)
#Retention(RUNTIME)
public #interface Environmental {
public static enum Environment {
Development, Testing, Production
};
Environment[] value() default {};
}
#Named
public class EnvironmentalAmbiguity implements Ambiguity {
/* This can be set via a property in applicationContext.xml, which Spring
can use place holder, environment variable, etc. */
Environment env = Environment.Development;
#Override
public boolean isSatisfiedBy(BeanDefinitionHolder holder) {
BeanDefinition bd = holder.getBeanDefinition();
RootBeanDefinition rbd = (RootBeanDefinition) bd;
Class<?> bc = rbd.getBeanClass();
Environmental env = bc.getAnnotation(Environmental.class);
return (env == null) ? false : hasCorrectValue(env);
}
private boolean hasCorrectValue(Environmental e) {
for (Environment env : e.value()) {
if (env.equals(this.env)) {
return true;
}
}
return false;
}
}
#Named
public class MySuperDuperBeanFactoryPostProcessor implements
BeanFactoryPostProcessor, AutowireCandidateResolver {
private DefaultListableBeanFactory beanFactory;
private AutowireCandidateResolver defaultResolver;
#Override
public void postProcessBeanFactory(ConfigurableListableBeanFactory arg)
throws BeansException {
if (arg instanceof DefaultListableBeanFactory) {
beanFactory = (DefaultListableBeanFactory) arg;
defaultResolver = beanFactory.getAutowireCandidateResolver();
beanFactory.setAutowireCandidateResolver(this);
return;
}
throw new FatalBeanException(
"BeanFactory was not a DefaultListableBeanFactory");
}
#Override
public Object getSuggestedValue(DependencyDescriptor descriptor) {
return defaultResolver.getSuggestedValue(descriptor);
}
#Override
public boolean isAutowireCandidate(BeanDefinitionHolder holder,
DependencyDescriptor descriptor) {
Ambiguity ambiguity = getAmbiguity(descriptor);
if (ambiguity == null) {
return defaultResolver.isAutowireCandidate(holder, descriptor);
}
return ambiguity.isSatisfiedBy(holder);
}
private Ambiguity getAmbiguity(DependencyDescriptor descriptor) {
Ambiguous ambiguous = getAmbiguousAnnotation(descriptor);
if (ambiguous == null) {
return null;
}
Class<? extends Ambiguity> ambiguityClass = ambiguous.value();
return beanFactory.getBean(ambiguityClass);
}
private Ambiguous getAmbiguousAnnotation(DependencyDescriptor descriptor) {
Field field = descriptor.getField();
if (field == null) {
MethodParameter methodParameter = descriptor.getMethodParameter();
if (methodParameter == null) {
return null;
}
return methodParameter.getParameterAnnotation(Ambiguous.class);
}
return field.getAnnotation(Ambiguous.class);
}
}
Now if I have an interface MyInterface and two classes that implement it MyFooInterface and MyBarInterface like this:
public interface MyInterface {
public String getMessage();
}
#Named
#Environmental({ Environment.Testing, Environment.Production })
public class MyTestProdInterface implements MyInterface {
#Override
public String getMessage() {
return "I don't always test my code, but when I do, I do it in production!";
}
}
#Named
#Environmental(Environment.Development)
public class DevelopmentMyInterface implements MyInterface {
#Override
public String getMessage() {
return "Developers, developers, developers, developers!";
}
}
If I want to #Inject MyInterface I would get the same multiple bean definition error that one would expect. But I can add #Ambiguous(EnvironmentalAmbiguity.class) and then the EnvironmentalAmbiguity will tell which bean definition it is satisfied by.
Another approach would have been to use a List and go through them all seeing if they are satisfied by a given bean definition, this would mean that the dependnecy wouldn't need the #Ambiguous annotation. That might be more "IoC-ish" but I also thought it might perform poorly. I have not tested that.
New to the world of TDD and I have soon find out that mocking at times is not as easy.
We are using MOQ at work so I need to learn how to do this using moq
I have some code using the command pattern and works a treat.However If were to test drive it I would not know how to do it implementing the code below.
I have done the following
Created BaseToolStripMenuItem:ToolStripMenuItem and added a Command Property (see below)
Created a windows form and added a menuStrip with 2 item Open and Exit
In the form I just add to map the command to a button and all works a treat.
I would like to change the code so that I can UnitTest using Moq but cannot see how???
Can you help?
Any suggestions?
Thanks a lot!!
public interface ICommand
{
void Execute()
}
public abstract class BaseCmd :ICommand
{
protected ProcessMenuCommand ProcessCommand;
protected MenuCommandFactory Factory;
protected BaseCmd(ProcessMenuCommand processMenuCommand, MenuCommandFactory cmdfactory)
{
ProcessCommand = processMenuCommand;
Factory = cmdfactory;
}
abstract public void Execute();
}
public class BaseToolStripMenuItem : ToolStripMenuItem
{
public BaseToolStripMenuItem()
{
Click += MenuItemClick;
Command = null;
}
public BaseCmd Command { get; set; }
private void MenuItemClick(object sender, EventArgs args)
{
if (Command != null) Command.Execute();
}
}
public class MenuCommandFactory
{
private readonly ProcessMenuCommand _processMenuCommand;
public MenuCommandFactory(ProcessMenuCommand processMenuCommand)
{
_processMenuCommand = processMenuCommand;
}
public OpenFileCmd OpenFile()
{
return new OpenFileCmd(_processMenuCommand,this);
}
public ExitCmd Exit()
{
return new ExitCmd(_processMenuCommand, this);
}
}
public class OpenFileCmd:BaseCmd
{
public OpenFileCmd(ProcessMenuCommand processMenu,MenuCommandFactory menuCommandFactory)
:base(processMenu,menuCommandFactory)
{
}
public override void Execute()
{
ProcessCommand.OpenFile();
}
}
public class ProcessMenuCommand
{
public void OpenFile()
{
MessageBox.Show("Open a file");
}
public void Exit()
{
MessageBox.Show("Exiting");
}
}
public class ExitCmd:BaseCmd
{
public ExitCmd(ProcessMenuCommand processMenu, MenuCommandFactory menuCommandFactory)
:base(processMenu,menuCommandFactory)
{
}
public override void Execute()
{
ProcessCommand.Exit();
}
}
//In the form
public partial class Form1 : Form
{
private ProcessMenuCommand menuCommandProcessor;
private MenuCommandFactory factory;
public Form1()
{
InitializeComponent();
// Created editor and factory.
menuCommandProcessor = new ProcessMenuCommand();
factory = new MenuCommandFactory(menuCommandProcessor);
// Get concrete command objects from factory and assign to corresponding menu items and tool strip buttons.
tsOpen.Command = factory.OpenFile();
tsExit.Command = factory.Exit();
}
}
However If were to test drive it I would not know how to do it implementing the code below
The idea about TDD is that it drives you towards an implementation. There are many implementations you could never arrive at using TDD, so your question doesn't really make much sense.
Try to write some tests that drive you towards your goal without having a preconceived image of the solution at which you wish to arrive. It will often turn out that you end up at an entirely different (and better) place than what you originally thought.
A simple Novice Rule: no abstract classes. Try designing again with only interfaces and concrete classes. You'll notice it's easier to test-drive the result.
As for "how to TDD a Command object", a Command is just a class that provides a single action. Test-drive it the same way you would test-drive any method, except you name the method Execute().