If I have a class, where all methods should evaluate only if a boolean attribute is true, what is the best way to define it in terms of best practices?
Is there a way to replace the recurring isEnabled check in all the methods by a single check? The current form works, I'm looking for a way to improve it to not have isEnabled checked in all the methods.
#Singleton
public class SomeClass implements SomeInterface {
EventPublisher eventPubilsher;
boolean isEnabled;
#Inject
public SomeClass(final Decider decider, EventPublisher, eventPublisher) {
this.isEnabled = decider.isSomethingEnabled();
this.eventPublisher = eventPublisher;
}
#Override
public void method1() {
if(isEnabled){
eventPublisher.publishSomething1();
}
}
#Override
public void method2() {
if(isEnabled){
eventPublisher.publishSomething2();
}
}
#Override
public void method3() {
if(isEnabled){
eventPublisher.publishSomething3();
}
}
}
You can have implementation for enabled stuff, and one for disabled stuff. The disabled implementation won't do anything:
public class DisabledSomeClass implements SomeInterface {
#Override
public void method1() {
}
#Override
public void method2() {
}
#Override
public void method3() {
}
}
Enabled one will publish stuff:
public class EnabledSomeClass implements SomeInterface {
EventPublisher eventPublisher;
public EnabledSomeClass(EventPublisher eventPublisher) {
this.eventPublisher = eventPublisher;
}
#Override
public void method1() {
eventPublisher.publishSomething1();
}
#Override
public void method2() {
eventPublisher.publishSomething2();
}
#Override
public void method3() {
eventPublisher.publishSomething3();
}
}
Then extract the logic, if functionality is enabled in new factory class - SomeInterfaceFactory (probably not the best name, but you get the idea), it will return the correct implementation, depending on whether something is enabled.
public class SomeInterfaceFactory {
public static SomeInterface getInstance(Decider decider, EventPublisher eventPublisher) {
if (decider.isSomethingEnabled()) {
return new EnabledSomeClass(eventPublisher);
} else {
return new DisabledSomeClass();
}
}
}
This should work
#Singleton
public class SomeClass implements SomeInterface {
EventPublisher eventPubilsher;
boolean isEnabled;
#Inject
public SomeClass(final Decider decider, EventPublisher, eventPublisher) {
this.isEnabled = decider.isSomethingEnabled();
this.eventPublisher = eventPublisher;
}
#Override
public void method1() {
publish(ep->ep.publishSomething1());
}
#Override
public void method2() {
publish(ep->ep.publishSomething2());
}
#Override
public void method3() {
publish(ep->ep.publishSomething3());
}
private void publish(Consumer<EventPublisher> callback){
if(isEnabled) callback.accept(eventPublished);
}
}
A Runnable interface can receive a lambda without args and run a lambda function with run() method. So, you can create a method inside your Decider class and receive a Runnable as a parameter, like:
class Decider{
private boolean enabled;
//...
public void execute(Runnable runnable){
if(enabled) runnable.run();
}
}
And receive your Decider and do:
//...
EventPublisher eventPubilsher;
Decider decider;
#Inject
public SomeClass(final Decider decider, EventPublisher, eventPublisher) {
this.decider = decider;
this.eventPublisher = eventPublisher;
}
#Override
public void method1() {
Decider.execute(() -> eventPublisher.publishSomething1());
}
//...
You're locking the evaluation of the condition to the constructor. If you want any flexibility, you should pull it out.
public class SomeClass implements SomeInterface {
boolean isEnabled;
public SomeClass(EventPublisher, eventPublisher) {
//
}
public void addDecide(boolean value){
isEnabled = value;
}
boolean getEnabled(){
return isEnabled;
}
#Override
public void method3() {
if(getEnabled()){
eventPublisher.publishSomething3();
}
}
}
You can even go crazy and add a supplier:
public void addDecide(Supplier<Boolean> supplier){
supplier = supplier;
}
boolean getEnabled(){
return supplier.get();
}
Related
I have a function that returns void
public interface IProductService {
void delete(String id);
}
Generic method
public interface IRequestHandler<C , R> {
R handler(C c);
Class<C> commandType();
}
Implementation of generic interface
#Singleton
public record DeleteProductCommandHandler(IProductService iProductService)
implements IRequestHandler<DeleteProductCommand, Void> {
#Override
public Void handler(DeleteProductCommand deleteProductCommand) {
return iProductService.delete(deleteProductCommand.id);
}
#Override
public Class<DeleteProductCommand> commandType() {
return DeleteProductCommand.class;
}
}
How can I use void in IRequestHandler<DeleteProductCommand, Void> so that I can map void from iProductService.delete(deleteProductCommand.id);
Option 1:
Just return null:
#Override
public Void handler(DeleteProductCommand deleteProductCommand) {
iProductService.delete(deleteProductCommand.id);
return null;
}
Option 2:
Update the IProductService::delete method to return something meaningful, e.g. a boolean value like Collection::remove does:
public interface IProductService {
boolean delete(String id);
}
#Singleton
public record DeleteProductCommandHandler(IProductService iProductService)
implements IRequestHandler<DeleteProductCommand, Boolean> {
#Override
public Boolean handler(DeleteProductCommand deleteProductCommand) {
return iProductService.delete(deleteProductCommand.id);
}
#Override
public Class<DeleteProductCommand> commandType() {
return DeleteProductCommand.class;
}
}
I have a code block like below:
public Interface ISupClass{
void call();
void call1();
...
}
public class NormalClass implements ISupClass{
void call(){
....operations...
}
void call1(){
....operations...
}
...
}
public class DailyClass implements ISupClass{
void call(){
....operations...
}
void call1(){
....operations...
}
...
}
Then I call them from main service like that;
Instances:
private INormalClass dailyClass = new DailyClass();
private INormalClass normalClass = new NormalClass();
Method:
public void call(int type, boolean isDaily){
if(type == 0) {
if(isDaily){
dailyClass.call();
}
else{
normalClass.call();
}
}
if(type == 1) {
if(isDaily){
dailyClass.call1();
}
else{
normalClass.call1();
}
}
...
}
Is there a way to escape from isDaily check in above code block? Or how can I implement it effectively? I have just tried to implement with Java Generics but this doesn't look possible?
I know this looks like related with polimorfizm. But I wonder somethink like about it;
public Interface ISupClass<E>
call(E type)
...
public class NormalClass implements ISupClass<Boolen.FALSE>
...
public class DailyClass implements ISupClass<Boolen.TRUE>
...
public void call(int type, boolean isDaily){
supClass.call(isDaily);
(In case I understood what is the question)
This is the point of using interfaces. Simply do something like this:
public class Example {
public static interface ISupClass {
void doSomething();
}
public static class NormalClass implements ISupClass {
#Override
public void doSomething() {
System.out.println("I am a normal class.");
}
}
public static class DailyClass implements ISupClass {
#Override
public void doSomething() {
System.out.println("I am a daily class.");
}
}
public static void doSomething(ISupClass clazz) {
clazz.doSomething();
}
public static void main(String[] args) {
doSomething(new DailyClass());
doSomething(new NormalClass());
}
}
So, in your case instead of passing boolean isDaily, pass argument ISupClass in call method.
public void call(int type, ISupClass caller) {
caller.call();
}
Now, generics is a totally different story and I am not able to see how it is related to the question.
From what I understand, public void call(int type, boolean isDaily){...} is an orchestrator/mediator method that manipulates the one or the other instance according to the flags received in the parameters.
In this case, why not use a Map<Boolean, INormalClass> to store the two instances in a way where you can retrieve them from a boolean key :
Map<Boolean, INormalClass> map = new HashMap<>();
map.put(Boolean.TRUE, new DailyClass());
map.put(Boolean.FALSE, new NormalClass());
//...
public void call(int type, boolean isDaily){
INormalClass obj = map.get(isDaily);
if(type == 0) {
obj.call();
}
if(type == 1) {
obj.call1();
}
}
You could add default method to the interface:
public interface ISupClass {
default void call(int type) {
if (type == 0) {
call();
} else if(type == 1) {
call1();
}
}
void call();
void call1();
}
It leads you to following code:
public static void call(int type, boolean isDaily) {
if (isDaily) {
dailyClass.call(type);
} else {
normalClass.call(type);
}
}
I'm trying to get rid of big switch statement from my code and I thought that Strategy pattern based on my existing enum would be nice. The concept is like:
public class MyStrategy {
public MyStrategy() {
Option.Option1.setMethodToExecute(this::action1);
Option.Option2.setMethodToExecute(this::action2);
}
public void executeChoosenMethod(int i) {
Option.values()[i].execute();
// instead of
// switch(convertItoOption()) {
// case Option1:...
// case Option2:...
// }
}
private void action1() {
System.out.println("action1");
}
private void action2() {
System.out.println("action2");
}
private enum Option {
Option1, Option2;
private InvokeAction methodToExecute;
public void setMethodToExecute(InvokeAction methodToExecute) {
this.methodToExecute = methodToExecute;
}
public void execute() {
methodToExecute.execute();
}
}
#FunctionalInterface
private interface InvokeAction {
void execute();
}
}
so I can use it like:
public class StrategyTest {
public static void main(String[] args) {
MyStrategy strategy = new MyStrategy();
//user choose 0 or 1
strategy.executeChoosenMethod(0);
strategy.executeChoosenMethod(1);
}
}
but I don't like this part with Option.Option1.setMethodToExecute(this::action1); since my enum has more and more options and I would like to have all of this inside enum. What would be perfect is something like this:
public class MyStrategy {
public void executeChoosenMethod(int i) {
Option.values()[i].execute();
}
private void action1() {
System.out.println("action1");
}
private void action2() {
System.out.println("action2");
}
private enum Option {
Option1(MyStrategy.this::action1),
Option2(MyStrategy.this::action2);
private InvokeAction methodToExecute;
private Option(InvokeAction method) {
methodToExecute = method;
}
public void execute() {
methodToExecute.execute();
}
}
#FunctionalInterface
private interface InvokeAction {
void execute();
}
}
but this is impossible since enum is static and I don't have access to enclosing instance by MyStrategy.this. I need enum, because I have set of options and it is convenient to use methods like values() or valueOf(), but what I would like to have is single line invoke instead of growing switch.
Do you have any ideas how to achieve sometghing like this or is there any workaround to make this enum constructor call possible Option1(MyStrategy.this::action1) ?
With enums you could implement it like this:
public class MyStrategy {
public void executeChoosenMethod(int i) {
Option.values()[i].execute(this);
}
private void action1() {
System.out.println("action1");
}
private void action2() {
System.out.println("action2");
}
private enum Option {
Option1(MyStrategy::action1),
Option2(MyStrategy::action2);
private InvokeAction methodToExecute;
private Option(InvokeAction method) {
methodToExecute = method;
}
public void execute(MyStrategy s) {
methodToExecute.execute(s);
}
}
#FunctionalInterface
private interface InvokeAction {
void execute(MyStrategy s);
}
}
This uses the fact the with lambdas you can make method references to arbitrary instance methods and call them on a specific instance by passing in the instance as first parameter.
you're right. This isn't possible with enum. But why not just use a good old class:
public class MyStrategy {
public MyStrategy() {
buildUp();
}
public void executeChoosenMethod(int i) {
actions.get(i).execute();
}
private void action1() {
System.out.println("action1");
}
private void action2() {
System.out.println("action2");
}
private List<InvokeAction> actions = new ArrayList<>();
private void buildUp() {
actions.add(this::action1);
actions.add(this::action2);
}
#FunctionalInterface
private interface InvokeAction {
void execute();
}
}
This question already has an answer here:
Methods in Enums [duplicate]
(1 answer)
Closed 8 years ago.
Right now, I have an enum for a variety of values, and I was wondering if there is any way I would be able to store a method in an enum. For example:
public enum myEnum{
one("first", callFirstMethod),
two("second", callSecondMethod),
three("last", callThirdMethod);
public String message;
public Method met;
myEnum(String m, Method meth){
message = m;
met = meth;
}
}
public class myMethods{
public void callFirstMethod(){
System.out.println("First!");
}
public void callSecondMethod(){
System.out.println("Second!");
}
public void callThirdMethod(){
System.out.println("Third!");
}
}
Then by using something like:
Method method = myEnum.one.callFirstMethod();
To call the method. Is something like this possible? I've tried playing around/looking around on google, and nothing is really turning up. Thank you for the help!
Use an interface and have the interface instance as the second enum parameter, or give it an abstract method that is implemented in the instance. For instance:
enum MyEnum {
ONE("first", new MyInterface() {
#Override
public void commonMethod() {
System.out.println("First!");
}
}) {
#Override
public void abstractEnumMethod() {
System.out.println("abstract enum meuthod, first!");
}
},
TWO("second", new MyInterface() {
#Override
public void commonMethod() {
System.out.println("Second!");
}
}) {
#Override
public void abstractEnumMethod() {
System.out.println("abstract enum meuthod, second!");
}
},
THREE("last", new MyInterface() {
#Override
public void commonMethod() {
System.out.println("Third!");
}
}) {
#Override
public void abstractEnumMethod() {
System.out.println("abstract enum meuthod, third!");
}
};
private String message;
private MyInterface myType;
private MyEnum(String m, MyInterface myType) {
message = m;
this.myType = myType;
}
public String getMessage() {
return message;
}
public MyInterface getMyType() {
return myType;
}
public void enumMethod() {
System.out.println(message);
}
public abstract void abstractEnumMethod();
}
interface MyInterface {
void commonMethod();
}
The answer all depends on what it's you want to achieve. For example, you could provide a common method within you enum and inspect the instance of the enum calling it...
public class TestEnum {
public static void main(String[] args) {
MyEnum.ONE.doStuff();
MyEnum.TWO.doStuff();
MyEnum.THREE.doStuff();
}
public enum MyEnum {
ONE("first"),
TWO("second"),
THREE("last");
public String message;
MyEnum(String m) {
message = m;
}
public void doStuff() {
System.out.println(name());
if (ONE.equals(this)) {
System.out.println("...Do stuff for one");
} else if (TWO.equals(this)) {
System.out.println("...Do stuff for two");
} else if (THREE.equals(this)) {
System.out.println("...Do stuff for three");
}
}
}
}
Which outputs...
one
...Do stuff for one
two
...Do stuff for two
three
...Do stuff for three
I have managed to successfully implement a custom injection annotation with target PARAMETER. I do not understand how I make my the annotation support target METHOD as well though?
Here is my sample code:
Hello annotation:
#Retention(RUNTIME)
#Target({METHOD, PARAMETER})
public #interface Hello {
}
Hello annotation resolver:
#Singleton
public class HelloResolver {
public static class HelloInjectionResolver extends ParamInjectionResolver<Hello> {
public HelloInjectionResolver() {
super(HelloValueFactoryProvider.class);
}
}
#Singleton
public static class HelloValueFactoryProvider extends AbstractValueFactoryProvider {
#Inject
public HelloValueFactoryProvider(final MultivaluedParameterExtractorProvider extractorProvider,
final ServiceLocator injector) {
super(extractorProvider, injector, UNKNOWN);
}
#Override
protected Factory<?> createValueFactory(final Parameter parameter) {
if (!String.class.equals(parameter.getRawType())) return null;
if (parameter.getAnnotation(Hello.class) == null) return null;
return new AbstractContainerRequestValueFactory<String>() {
#Override
public String provide() {
final DateTime now = DateTime.now();
if (22 < now.getHourOfDay() || now.getHourOfDay() < 6) {
throw new WebApplicationException(FORBIDDEN);
} else {
return format("Hello, it is %s o'clock so I am awake! :)", forPattern("HH:mm").print(now));
}
}
};
}
}
public static class Binder extends AbstractBinder {
#Override
protected void configure() {
bind(HelloValueFactoryProvider.class).to(ValueFactoryProvider.class).in(Singleton.class);
bind(HelloInjectionResolver.class).to(
new TypeLiteral<InjectionResolver<Hello>>() {
}
).in(Singleton.class);
}
}
}
Hello resources:
#Path("hello")
public class HelloResource {
#GET
#Path("method")
#Produces(APPLICATION_JSON)
#Hello
public String method() {
return "Hello!";
}
#GET
#Path("param")
#Produces(APPLICATION_JSON)
public String param(#Hello final String hello) {
return hello;
}
}
When I hit
http://localhost:8080/hello/method
I get a Hello! back no matter if the hour is within the forbidden interval.
I am not sure this will work, but you could try this:
public static class HelloInjectionResolver extends ParamInjectionResolver<Hello> {
public HelloInjectionResolver() {
super(HelloValueFactoryProvider.class);
}
public boolean isMethodParameterIndicator() {
return true;
}
}
Warning: I have not tried this myself but in theory that should allow your resolver to work as a parameter in the method.