Add support for Inject

[decebals]

#554

[decebals]

Now everything (almost) is configurable via DI container and the things remain perfectly the same until now if no DI container is detected. Only one new tiny dependency is added (javax.inject) with scope provided .
I tested on pippo-demo and pippo-test projects to see that things work perfectly without inject.
I tested with Spring and Guice, in complex scenario (inject new webserver, new template engine, ..) and things work as expected.

From the beginning, we wanted this feature to be as unobtrusive as possible, with as less as possible changes.
My implementation started from the idea that both Spring and Guice (the most important DI containers from Java) have support for optional inject for the fields annotated with standard javax.inject.Inject.
The idea is to use java.util.Optional<T> option for that fields.
In theory the using of java.util.Optional is discouraged for fields (according documentation) but many people (included Spring and Guice teams that implemented a such support in their libraries) consider a perfect fit and I agree with that.
My idea was to add lazy initialization in getters (Application and ControllerApplication) and to initialize the injected fields that are not touched by injection.

I think that we can do the code more compact but this is another story. For example for each inject aware field we have a declaration and a lazy initialization getter (and in some cases a setter):

@InjectprivateOptional<ErrorHandler> errorHandler = Optional.empty();
publicErrorHandlergetErrorHandler() {
if (!errorHandler.isPresent()) {
errorHandler = Optional.of(newDefaultErrorHandler(this));
}
returnerrorHandler.get();
}
publicvoidsetErrorHandler(ErrorHandlererrorHandler) {
this.errorHandler = Optional.of(errorHandler);
}

I prefer something more verbose/light as:

@InjectprivateOptional<ErrorHandler> errorHandler;
publicErrorHandlergetErrorHandler() {
returnOptionalUtils.setOnNull(Supplier<ErrorHandler>).get();
}

Also the proposed implementation with lazy initialization getters come with some improvements from performance point of view because the objects are initialized only on request.

That is all. I will add in my next two comments how I tested with Spring and Guice. If this PR will be accepted, after merge I will update pippo-demo project (pippo-demo-spring and pippo-demo-guice). With this PR the pippo-spring and pippo-guice are no longer needed and should be deleted.

[decebals]

For Spring Test, I modified pippo-demo-spring

publicclassSpringApplication3extendsControllerApplication {
@InjectprivateList<? extendsController> controllers;
@OverrideprotectedvoidonInit() {
// add routes for static contentaddPublicResourceRoute();
addWebjarsResourceRoute();
addControllers(controllers.toArray(newController[0]));
}
}

@Configuration@ComponentScanpublicclassSpringConfiguration3extendsSpringConfiguration {
@BeanpublicContactServicecontactService() {
returnnewInMemoryContactService();
}
@BeanpublicTemplateEnginetemplateEngine() {
returnnewSimpleTemplateEngine();
}
@BeanpublicRouterrouter() {
returnnewCustomRouter();
}
@BeanpublicWebServerwebServer() {
returnnewTjwsServer();
}
@BeanpublicPippoSettingspippoSettings() {
returnnewPippoSettings();
}
@BeanpublicApplicationapplication() {
returnnewSpringApplication3();
}
@BeanpublicPippopippo() {
returnnewPippo(application()).setServer(webServer());
}
}

publicclassSpringDemo3 {
publicstaticvoidmain(String[] args) {
ApplicationContextcontext = newAnnotationConfigApplicationContext(SpringConfiguration3.class);
Pippopippo = context.getBean(Pippo.class);
pippo.start();
}
}

@Path@ComponentpublicclassContactsControllerextendsController {
@InjectprivateContactServicecontactService;
@InjectprivateTemplateEnginetemplateEngine;
@GETpublicvoidsayHello() {
StringWriterwriter = newStringWriter();
Map<String, Object> model = newHashMap<>();
model.put("name", "Decebal");
templateEngine.renderString("Hello ${name}", model, writer);
getResponse().send(writer.toString());
}
}

[decebals]

For Guice Test, I modified pippo-demo-guice

publicclassGuiceApplication3extendsControllerApplication {
@InjectprivateList<? extendsController> controllers;
@OverrideprotectedvoidonInit() {
// add routes for static contentaddPublicResourceRoute();
addWebjarsResourceRoute();
addControllers(controllers.toArray(newController[0]));
}
}

publicclassGuiceModule3extendsAbstractModule {
@Overrideprotectedvoidconfigure() {
bind(ContactService.class).to(InMemoryContactService.class).asEagerSingleton();
bind(Application.class).to(GuiceApplication3.class).asEagerSingleton();
bind(Router.class).to(CustomRouter.class).in(Scopes.SINGLETON);
bind(TemplateEngine.class).to(SimpleTemplateEngine.class).asEagerSingleton();
bind(WebServer.class).to(TjwsServer.class).in(Scopes.SINGLETON);
bind(Pippo.class);
bindOptionalApplication();
bindOptionalControllerApplication();
}
@Singleton@Provides@InjectpublicList<? extendsController> controllers(ContactsControllercontacts) {
returnArrays.asList(contacts);
}
privatevoidbindOptionalApplication() {
OptionalBinder.newOptionalBinder(binder(), ContentTypeEngines.class);
OptionalBinder.newOptionalBinder(binder(), ErrorHandler.class);
OptionalBinder.newOptionalBinder(binder(), HttpCacheToolkit.class);
OptionalBinder.newOptionalBinder(binder(), Languages.class);
OptionalBinder.newOptionalBinder(binder(), Messages.class);
OptionalBinder.newOptionalBinder(binder(), MimeTypes.class);
OptionalBinder.newOptionalBinder(binder(), Router.class);
OptionalBinder.newOptionalBinder(binder(), WebSocketRouter.class);
OptionalBinder.newOptionalBinder(binder(), RequestResponseFactory.class);
OptionalBinder.newOptionalBinder(binder(), RoutePreDispatchListenerList.class);
OptionalBinder.newOptionalBinder(binder(), RoutePostDispatchListenerList.class);
OptionalBinder.newOptionalBinder(binder(), TemplateEngine.class);
OptionalBinder.newOptionalBinder(binder(), newTypeLiteral<RouteHandler<?>>(){});
OptionalBinder.newOptionalBinder(binder(), newTypeLiteral<List<Initializer>>(){});
}
privatevoidbindOptionalControllerApplication() {
OptionalBinder.newOptionalBinder(binder(), ControllerFactory.class);
OptionalBinder.newOptionalBinder(binder(), ControllerInitializationListenerList.class);
OptionalBinder.newOptionalBinder(binder(), ControllerInstantiationListenerList.class);
OptionalBinder.newOptionalBinder(binder(), ControllerInvokeListenerList.class);
OptionalBinder.newOptionalBinder(binder(), newTypeLiteral<List<MethodParameterExtractor>>(){});
}
}

publicclassGuiceDemo3 {
publicstaticvoidmain(String[] args) {
Injectorinjector = Guice.createInjector(newGuiceModule3());
Pippopippo = injector.getInstance(Pippo.class);
pippo.start();
}
}

@PathpublicclassContactsControllerextendsController {
@InjectprivateContactServicecontactService;
@InjectprivateTemplateEnginetemplateEngine;
@GETpublicvoidsayHello() {
StringWriterwriter = newStringWriter();
Map<String, Object> model = newHashMap<>();
model.put("name", "Decebal");
templateEngine.renderString("Hello ${name}", model, writer);
getResponse().send(writer.toString());
}
}

I don't like the complexity of GuiceModule3 (extra bindOptionalApplication and bindOptionalControllerApplication methods) but probably we can improve the code here (disclaimer: I'm not a good Guice connoisseur),

[mhagnumdw]

@Singleton@Provides@InjectpublicList<? extendsController> controllers(ContactsControllercontacts) {
returnArrays.asList(contacts);
}

Sorry I didn't understand why ContactsController contacts. contacts ?!

What if I have dozens of controllers?

[mhagnumdw]

@decebals , will you still make changes or can I test this version in my application?

[decebals]

@decebals , will you still make changes or can I test this version in my application?

I think that you can test it. The code is perfect functional from what I see until now. Maybe little adjustments in time.

[decebals]

@Singleton@Provides@InjectpublicList<? extendsController> controllers(ContactsControllercontacts) {
returnArrays.asList(contacts);
}

Sorry I didn't understand why ContactsController contacts. contacts ?!

What if I have dozens of controllers?

Your question is good. In my last (relative big) project I use Pippo with Spring. In Spring this part with gathering all controllers and inject them in application is easy and automatically. All you have to do is to add Component annotation on each controller class and enable component scan ( @ComponentScan) in configuration.
In Guice I think that you need to register each controller by hand, no support for component scan in core (at least as far as I know). I am not a Guice guy and I am sure that the example code presented by me related to Guice can be improved.
Maybe there's someone here who can help us.

[decebals]

Your question is good. In my last (relative big) project I use Pippo with Spring. In Spring this part with gathering all controllers and inject them in application is easy and automatically. All you have to do is to add Component annotation on each controller class and enable component scan ( @ComponentScan) in configuration. In Guice I think that you need to register each controller by hand, no support for component scan in core (at least as far as I know). I am not a Guice guy and I am sure that the example code presented by me related to Guice can be improved. Maybe there's someone here who can help us.

In the end I think that I solved the problem in an elegant way using Guice Multibinding and Reflections.
Now the code looks like:

publicclassGuiceModule3extendsAbstractModule {
@Overrideprotectedvoidconfigure() {
bind(ContactService.class).to(InMemoryContactService.class).asEagerSingleton();
bind(Application.class).to(GuiceApplication3.class).asEagerSingleton();
bind(Router.class).to(CustomRouter.class).in(Scopes.SINGLETON);
bind(TemplateEngine.class).to(SimpleTemplateEngine.class).asEagerSingleton();
bind(WebServer.class).to(TjwsServer.class).in(Scopes.SINGLETON);
bind(Pippo.class);
bindControllers();
bindOptionalApplication();
bindOptionalControllerApplication();
}
privatevoidbindControllers() {
// retrieve controller classesReflectionsreflections = newReflections(getClass().getPackage().getName());
Set<Class<? extendsController>> controllers = reflections.getSubTypesOf(Controller.class);
// bind found controllersMultibinder<Controller> multibinder = Multibinder.newSetBinder(binder(), Controller.class);
controllers.forEach(controller -> multibinder.addBinding().to(controller));
}
}

publicclassGuiceApplication3extendsControllerApplication {
@InjectprivateSet<Controller> controllers;
@OverrideprotectedvoidonInit() {
// add routes for static contentaddPublicResourceRoute();
addWebjarsResourceRoute();
addControllers(controllers.toArray(newController[0]));
}
}

I tested with multiple controllers and the result is good.

[mhagnumdw]

I already use the Reflections lib and it is very good!

[mhagnumdw]

@decebals , will you still make changes or can I test this version in my application?

I think that you can test it. The code is perfect functional from what I see until now. Maybe little adjustments in time.

My boot is heavily modified, so for now I won't be able to test it thoroughly. But I have good news: with this version my application continues to work normally.

[mhagnumdw]

I'm trying to adapt my application to this model...

@decebals , I use the EntityManager configured via the com.google.inject.persist.jpa.JpaPersistModule.JpaPersistModule Guice module.

The JpaPersistModule receives a set of properties via the properties(Map<?,?> properties) method. I got these properties from the ro.pippo.core.Application.getPippoSettings() instance. Do you have any idea what the best way to do this is now?

Application.getPippoSettings() will not be available when creating the Guice module.

[mhagnumdw]

For Guice Test, I modified pippo-demo-guice

publicclassGuiceApplication3extendsControllerApplication {
@InjectprivateList<? extendsController> controllers;
// ...
}

For me, Guice's dependency injection just only worked like this:

@InjectprivateSet<Controller> controllers;

obs: Set or List

[decebals]

obs: Set or List

Yes, it's Set instead of List. Sorry for inconvenient.
I will update the snippet code.

[decebals]

In #590 (comment), it's Set instead of List. Probably you copied the initial code.

[decebals]

I'm trying to adapt my application to this model...

@decebals , I use the EntityManager configured via the com.google.inject.persist.jpa.JpaPersistModule.JpaPersistModule Guice module.

The JpaPersistModule receives a set of properties via the properties(Map<?,?> properties) method. I got these properties from the ro.pippo.core.Application.getPippoSettings() instance. Do you have any idea what the best way to do this is now?

Application.getPippoSettings() will not be available when creating the Guice module.

I inject PippoSettings in Spring also, together with Application and other services. When I need PippoSettings I injected where I need it.
My approach with application.properties is hybrid, the same file is used by PippoSettings (internal stuff like server port, ..) but it is also used by Spring. I injected the properties in my services via Spring @Value annotation. So, if I need one or more properties in a service (or other component outside Pippo), I don't retrieve that information via PippoSettings, but using the DI container support for properties.

As I mentioned in #565, the pippo - spring integration is good enough for me and without this PR. This PR is useful when you want to fine tuning the pippo stack from DI (Spring, Guice), entirely.

[decebals]

I obtained relative (only one problem related to gathering all controllers in a set/list collection) good result with Avaje Inject library. It's a dependency injection library inspired by Dagger2, with very good performance and a small size (48 KB - version 5.13). It's useful when the total size of application matters, but you want to use a DI container.

The code in this case looks like:

//@SingletonpublicclassAvajeApplicationextendsControllerApplication {
privateList<Controller> controllers;
// @InjectpublicAvajeApplication(List<Controller> controllers) {
this.controllers = controllers;
}
@OverrideprotectedvoidonInit() {
// add routes for static contentaddPublicResourceRoute();
addWebjarsResourceRoute();
addControllers(controllers.toArray(newController[0]));
}
}

@FactorypublicclassAvajeConfiguration {
@BeanpublicContactServicecontactService() {
returnnewInMemoryContactService();
}
@BeanpublicPippoSettingspippoSettings() {
returnnewPippoSettings();
}
// @Bean// public List<Controller> controllers(ContactsController contactsController) {// System.out.println("AvajeConfiguration.controllers");// return Collections.singletonList(contactsController);// }@BeanpublicApplicationapplication(ContactsControllercontactsController, TestControllertestController) {
returnnewAvajeApplication(Arrays.asList(contactsController, testController));
}
// @Bean// public Pippo pippo(Application application, WebServer webServer) {// return new Pippo(application).setServer(webServer);// }
}

publicclassAvajeDemo {
publicstaticvoidmain(String[] args) {
BeanScopebeanScope = BeanScope.newBuilder().build();
Pippopippo = beanScope.get(Pippo.class);
pippo.start();
}
}

@Path@SingletonpublicclassContactsControllerextendsController {
@InjectContactServicecontactService;
@InjectTemplateEnginetemplateEngine;
@GETpublicvoidindex() {
getResponse().bind("contacts", contactService.getContacts());
getResponse().render("contacts");
}
}

[mhagnumdw]

I'm trying to adapt my application to this model...
@decebals , I use the EntityManager configured via the com.google.inject.persist.jpa.JpaPersistModule.JpaPersistModule Guice module.
The JpaPersistModule receives a set of properties via the properties(Map<?,?> properties) method. I got these properties from the ro.pippo.core.Application.getPippoSettings() instance. Do you have any idea what the best way to do this is now?
Application.getPippoSettings() will not be available when creating the Guice module.

I inject PippoSettings in Spring also, together with Application and other services. When I need PippoSettings I injected where I need it. My approach with application.properties is hybrid, the same file is used by PippoSettings (internal stuff like server port, ..) but it is also used by Spring. I injected the properties in my services via Spring @Value annotation. So, if I need one or more properties in a service (or other component outside Pippo), I don't retrieve that information via PippoSettings, but using the DI container support for properties.

As I mentioned in #565, the pippo - spring integration is good enough for me and without this PR. This PR is useful when you want to fine tuning the pippo stack from DI (Spring, Guice), entirely.

Hi! I understand that it is possible to inject PippoSettings into a Guice component. But this only works after Guice is ready. In my case I would need PippoSettings when creating the Guice modules.

To explain it better, something like this:

Injectorinjector = Guice.createInjector(
newPippoGuiceModule(),
newAppJpaPersistModule("persistenceUnitName", pippoSettings), // <<< need PippoSettings instance herenewAppGuiceModule()
);
GuiceInjector.set(injector);
Pippopippo = injector.getInstance(Pippo.class);
pippo.start();

ps: I'm looking for a way to work around this problem.

[mhagnumdw]

privatevoidbindControllers() {
// retrieve controller classesReflectionsreflections = newReflections(getClass().getPackage().getName());
Set<Class<? extendsController>> controllers = reflections.getSubTypesOf(Controller.class);
// bind found controllersMultibinder<Controller> multibinder = Multibinder.newSetBinder(binder(), Controller.class);
controllers.forEach(controller -> multibinder.addBinding().to(controller));
}

We might have abstract controllers, so maybe it's better to avoid bind errors (at least in Guice):

Reflectionsreflections = newReflections(getClass().getPackage().getName(), newSubTypesScanner());
Set<Class<? extendsController>> controllers = reflections.getSubTypesOf(Controller.class)
.stream()
.filter(clazz -> clazz.isAnnotationPresent(ro.pippo.controller.Path.class))
.collect(Collectors.toSet())

Or some other logic that checks if it's a concrete class.

[decebals]

Hi! I understand that it is possible to inject PippoSettings into a Guice component. But this only works after Guice is ready. In my case I would need PippoSettings when creating the Guice modules.

To explain it better, something like this:

Injectorinjector = Guice.createInjector(
newPippoGuiceModule(),
newAppJpaPersistModule("persistenceUnitName", pippoSettings), // <<< need PippoSettings instance herenewAppGuiceModule()
);
GuiceInjector.set(injector);
Pippopippo = injector.getInstance(Pippo.class);
pippo.start();

ps: I'm looking for a way to work around this problem.

I don't visualize your implementation. How AppJpaPersistModule looks like?

[decebals]

Hi! I understand that it is possible to inject PippoSettings into a Guice component. But this only works after Guice is ready. In my case I would need PippoSettings when creating the Guice modules.

What about https://stackoverflow.com/questions/39734343/injecting-a-dependency-into-guice-module?

[mhagnumdw]

I don't visualize your implementation. How AppJpaPersistModule looks like?

Oh, sorry 😅, I forgot to mention it's a class of mine. It's just a wrapper for Guice's JpaPersistModule.

It goes something like this:

publicclassAppJpaPersistModuleimplementsModule {
privatefinalPippoSettingssettings;
publicJPAGuiceModule(PippoSettingssettings) {
this.settings = settings;
}
@Overridepublicvoidconfigure(Binderbinder) {
JpaPersistModulejpaModule = newJpaPersistModule(Constantes.PU_NAME);
jpaModule.properties( ... ); // TODO: get properties from PippoSettings and add herebinder.install(jpaModule);
}
}

ps: But I think I'll change the strategy so I don't need PippoSettings there... I'm still not sure what it's going to look like... I'm still seeing it...

[mhagnumdw]

@decebals , I use Freemarker and it's not working. The problem is that the ro.pippo.freemarker.FreemarkerTemplateEngine.init(Application) method is not being called.

To make it work I did:

• Annotated the ro.pippo.core.AbstractTemplateEngine.init(Application) method with @javax.inject.Inject
• Annotated the ro.pippo.freemarker.FreemarkerTemplateEngine.init(Application) method with @javax.inject.Inject

I configure the Guice module like this:

@Overrideprotectedvoidconfigure() {
bind(Application.class).to(PippoApplication.class).asEagerSingleton();
bind(TemplateEngine.class).to(FreemarkerTemplateEngine.class).asEagerSingleton();
// ...
}

It would be nice to be able to leave the annotation just on the AbstractTemplateEngine class.

[decebals]

It would be nice to be able to leave the annotation just on the AbstractTemplateEngine class.

@mhagnumdw
I think that I have a solution based on #591. Please review #591 and if you consider that is OK I can merge it in master branch (and in inject branch) and I will continue work on this PR.

[mhagnumdw]

@decebals , please update from master.

[decebals]

@decebals , please update from master.

Done.

[mhagnumdw]

@decebals , please update from master.

[decebals]

@decebals , please update from master.

Done

[mhagnumdw]

Currently I register a content type like this: registerContentTypeEngine(GsonEngine.class).

What do you think we also use dependency injection to register ContentTypeEngine?

In Guice we can use MapBinder, in Spring I think it's also called MapBinder.

If you agree, could you implement it? So I would validate doing the tests in my application.

[decebals]

If you agree, could you implement it? So I would validate doing the tests in my application.

Sure, I will do it. Now I am in a mini vacation with family.

[sonarqubecloud]

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[decebals]

@mhagnumdw I don't know if you abandoned the ship but I will write here some of my conclusions :).
I found a method less intrusive based on Nullable annotation.
So, for each field that is a possible candidate for injection from outside (application) I added two annotations:

importjavax.annotation.Nullable;
importjavax.inject.Inject;
classMyClass {
@Inject@NullableprivateGreetinggreeting;
}

Both Spring and Guice know how to deal with this combination of annotations.
By the way, a similar approach is available for setter:

importjavax.annotation.Nullable;
importjavax.inject.Inject;
classMyClass {
privateGreetinggreeting;
@InjectpublicvoidsetGreeting(@NullableGreetinggreeting) {
this.greeting = greeting;
}
}

What I don't like is that in all situations (our initial solution based on Optional, the solution based on Nullable on field or setter parameter), in Guice (only here), you (the developer) are forced to inject something (via OptionalBinder or Providers.of(null)). For example see the snippet code from #590 (comment), bindOptionalXYZ are relative big and that doesn't smell good to me.

And this problem is because javax.inject.Inject doesn't come with support for optional.
The only cleaner solution for both Spring and Guice (for Guice in particular, because I have no problems in Spring) is to add both @Autowire (Spring) and @com.google.inject.Inject (Guice) on fields:

importorg.springframework.beans.factory.annotation.Autowired;
importcom.google.inject.Inject;
classMyClass {
@Autowired(required = false)
@Inject(optional = true)
privateGreetinggreeting;
}

but in this case we must add guice and spring-beans as dependencies ONLY for compile phase (Java is OK if it doesn't find the annotations declared in import section at runtime).

Everything started from the idea to have something/everything configurable via most popular java IoC (Spring and Guice), but without forcing the pippo developer to use IoC (or a specific IoC).

[mhagnumdw]

Hi @decebals !!

I paused this activity for timing reasons. I still think it's a worthwhile activity. But unfortunately, given its magnitude, I won't have time to see it carefully.

My application that uses Pippo is only receiving fixes and they are sporadic.