I was trying to express a lot of ideas in a small space, and I have edited it since, but it's still not as clear as I'd like. You and I agree, but I have struggled to get this point across.
Spring is a bloated mess, but when it first came out it was lean new framework and a relief from EJBv1 and EJBv2. In response, EJBv3 was much better, but in the meantime Spring became the new normal, and grew into some strange swiss army chainsaw glue with now-deprecated awful xml configuration replaced by the horror of not-quite-code-but-compiled-into-the-classfile @Annotations!
The 'new Spring' is Spring Boot, which was a response to this then-obscure framework called Dropwizard which showed that all you had to do was pick a handful of very good libraries get work done. Guava, Jersey, Jackson, Jetty; some decent ORM, and you're good to go. Some of these are backed by new Java specs like JAX-RS and JPA that are legitimately pretty good.
I think the biggest problem Java still has in the hearts and minds of people outside the 'enterprise' is not because of Java, but because of the complexities that only manifest in environments where your code isn't 100% greenfield every time.
Dependency Injection isn't something you realize you need until you realize you need it -- and then you realize you need it Really Badly.
Externalized XML config files declaring reusable beans isn't something you think you need until your client is asking how they can reconfigure something in the shipped software when they can't just recompile it to what they need.
Since they're compiled into the code, it means you can't change them without recompiling, so they're not actually configuration. But they're not actually code either, so they can't be subclassed or inherited, don't support generics, and have other quirks [1]. Furthermore, they are a sort of explicit notation to make you feel like you're getting 'convention' over 'configuration', but if it were truly convention you wouldn't need them in the first place.
For example, to teach my class how to serialize itself into JSON, I can compile com.fasterxml.jackson annotations into it, but by doing so I've made a particular JSON library a dependency of myproject-datatypes. I'd rather my myproject-controller or some other layer of my application take care of how the data looks over JSON. Luckily Jackson supports an entirely different way [2] of teaching it how to map a class, but not all libraries are so nice.
That is not to say annotations don't have their place. They're good declarative structures, but in my opinion they are used in places where they shouldn't be. This blog post [3] from 2009 accurately describes how I feel about annotations.
Annotations are data about the code. The fact that you can't change them without recompiling the code is a feature, not a bug.
If you want that kind of flexibility, use external files (e.g. XML) but now the two can get out of sync, which is what is commonly referred to as XML hell.
The rule of thumb is simple: whenever you need to add information about something in your source (class, method, field, package), use an annotation. If you need to add information about something that is not source code (port, host, various sizes, etc...) then use an external file. In particular, if you specify a reference to Java code in your XML, you should use an annotation instead.
> to teach my class how to serialize itself into JSON, I can compile com.fasterxml.jackson annotations into it, but by doing so I've made a particular JSON library a dependency of myproject-datatypes
Right, because at the moment, there is no standard cross-library convention for that. One day, there will be, as there is for serializing to XML:
> Since they're compiled into the code, it means you can't change them without recompiling, so they're not actually configuration.
Neither xml was configuration. I cannot remember ever changing xml for deployment. Actually in many ways the whole build jar/war process feels a lot like compiling in Javaland and while I'll happily pick jars or wars apart for troubleshooting deploying the result in production would break multiple guidelines at most places I guess (hope).
> Furthermore, they are a sort of explicit notation to make you feel like you're getting 'convention' over 'configuration', but if it were truly convention you wouldn't need them in the first place.
Partially agree but then again every other framework I have seen demands you do something: put x classes in y folder, subclass another class or implement an interface or something.
Compared to magical directory layout annotations are less well, magic, more explicit.
Compared to subclassing it is more flexible (although I remember enjoying Propel with Symfony 1.)
Compared to marker interfaces? Not sure.
That said once you accept them there is plenty of things you don't have to specify but can override if you want/need to.
Edit: As for your third reference it is out of sync itself:
> The same goes for EJB. I have a class named FooStatelessBean. How about we assume it's a stateless session bean, and it's interface is defined by its public methods? It can then provide FooRemote and FooLocal for me, and I don't need to configure anything or keep three classes in sync
I only use three annotations on such ones: @Named at the class telling the DI framework to pick it up for injection using its name as the name (although I can override it right there and then if I need to.) @Stateless tells it to make a suitable bunch of them and that it is OK to give any of them out to anyone at runtime and @PersistenceContext (at an instance variable) tells me that I want a reference to the ORM layer.
I could easily create a combined annotation for @Named and @Stateless, even naming it @Stateless and just importing my @Stateless instead of the standard (across all Java EE implementations) one.
I guess I could also create a superclass that does all this and subclass it but some day I'll leave the project and another one will have to maintain it.
Could we have picked this out from the name? Yep. Would it be magical? Yep, more so than annotations. Would it tie my hands with regards to naming classes? Yep.
> which was a response to this then-obscure framework called Dropwizard
I sat in with an AMA in NYC with Dave Syer. He said it was inspired by a project he was co-opted to which used Rails.
Not the actual architecture of Rails, mind you, but the "just works", out-of-the-box, no-configuration experience.
Disclosure: I work for Pivotal. So do many of Spring's core committers. There's a lot of feedback from Labs and Cloud R&D into Spring, but they're still a largely self-directed team.
Trying to upvote this because it's good info! But, but, I have one better :)
Spring Boot 1.0 GA Released [1] blog post, says, and links to a Spring Issue SPR-9888:
"It's been 18 months since the original request [2] to "improve containerless web application architectures", that gave birth to Spring Boot, was raised."
The body of the original issue [2] says, midway down:
"I think that Spring's web application architecture can be significantly simplified if it were to provided tools and a reference architecture that leveraged the Spring component and configuration model from top to bottom. Embedding and unifying the configuration of those common web container services within a Spring Container bootstrapped from a simple main() method.
Though there are many frameworks and platforms today that no longer require a container I think inspiration can be drawn most from DropWizard (http://dropwizard.codahale.com/).
Another project I've seen inspired by DropWizard but leveraging Spring is HalfPipe (https://github.com/32degrees/halfpipe). Though I don't think HalfPipe goes far enough. I think to truly provide simplification the entire architecture, wherever reasonable, must be embedded within the Spring container rather than without. Though it does have several other interesting ideas."
It could absolutely be both. Dave Syer is not the only person who drove Spring Boot. Phil Webb is the main day-to-day driver, from what I can tell. He's definitely been active in soliciting feedback from Labs Pivots.
> The 'new Spring' is Spring Boot, which was a response to this then-obscure framework called Dropwizard
This is correct, but what pisses me off is that the Spring folks clearly copied Dropwizard, then failed to even mention Dropwizard in their various docs, blogs, talks, etc, which you're thinking is fine. But they DO mention other (less useful) projects as supposed alternatives for Spring Boot, essentially, pretending as if Dropwizard doens't even exist when clearly it's the reason that Spring Boot exists! Shameful.
Spring hails Boot as the new way of doing things, but it's still by no means a clean break for the rest of the Spring ecosystem where programming by XML (or annotations) is still king and the APIs are still a horrible, overcomplicated mess. There's no undoing that.
Annotations are great for class metadata - JPA or beans binding or servlets and filter paths.
Externalizing binding was the kind of nice thing that almost never quite worked right. XML (or YAML because sysads are people too) for configurable parts is ok, but if you need to mix and match services it was never ever needed. The binding API allowed that years before spring style of depencency injection brought madness into the enterprise world and in a extremely better and clean way, using the facilities of the language instead of creating ugly reflective glue that kind of worked
Spring is a bloated mess, but when it first came out it was lean new framework and a relief from EJBv1 and EJBv2. In response, EJBv3 was much better, but in the meantime Spring became the new normal, and grew into some strange swiss army chainsaw glue with now-deprecated awful xml configuration replaced by the horror of not-quite-code-but-compiled-into-the-classfile @Annotations!
The 'new Spring' is Spring Boot, which was a response to this then-obscure framework called Dropwizard which showed that all you had to do was pick a handful of very good libraries get work done. Guava, Jersey, Jackson, Jetty; some decent ORM, and you're good to go. Some of these are backed by new Java specs like JAX-RS and JPA that are legitimately pretty good.
I think the biggest problem Java still has in the hearts and minds of people outside the 'enterprise' is not because of Java, but because of the complexities that only manifest in environments where your code isn't 100% greenfield every time.
Dependency Injection isn't something you realize you need until you realize you need it -- and then you realize you need it Really Badly.
Externalized XML config files declaring reusable beans isn't something you think you need until your client is asking how they can reconfigure something in the shipped software when they can't just recompile it to what they need.