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Java EE Microprofile

I know it could be a pretty vague topic but please can someone explain it in plain English. I've read some articles regarding the trending topic java EE's 'microprofile' but was not able to clearly understand its purpose.
My understanding in this emerging concept is that java community finds way to reshape the Java EE model to become a microservices friendly framework or platform.
If we can already create a distributed microservice application in few minutes using spring boot or other API / library then why do we need microprofile?

I am active within the MicroProfile community on a daily basis (and primary author of the FAQ on MicroProfile.io). As Gimby mentions, check out the FAQ.
Basically, the JCP is a standards organization and doing innovation using a process designed for standardizing technology is a no-no. The idea of MicroProfile is to do rapid innovation with Enterprise Java and Microservices that leads to technology standardization. To James' point, yes, it is getting off the ground using Java EE technologies so it will feel more natural for Java EE developers.
Going forward, however, MicroProfile will not be limited to Java EE technologies. It may adopt other non-Java EE frameworks or even create new APIs. Once features/technologies are mature enough, we'll look to standardize them. If you like the idea of standards around Java microservices and want to participate in innovating-before-standardizing, then join the MicroProfile google group and feel free to get involved in doing so. You can have direct input and even contribute code that will eventually be part of a standard.
Hope this helps.

If you like Spring Boot then I'd stick with it really. One of the whole points of microservices is for teams to use the technology that suits their needs and that they are happy with.
IMHO the Java EE Microprofile is focussed on helping help folks who know or like Java EE to move to microservices reusing their Java EE knowledge; rather than having to relearn how to do things on Spring Boot. e.g. so they can reuse CDI if they prefer that to Spring DI

Why is the play framework not built on top of the Servlet API?

I started playing with the playframework recently and really enjoy the simplicity.
But one nagging question I've had is why it eschews the servlet specification all together? What was the main motivation behind such an architectural decision?

From the FAQ
We are fully aware that we made
choices that are pretty uncommon in
the Java world, and that Play does not
blindly follow all the so-called Java
‘good practices’. But all of the Play
team members are very experienced Java
developers and we are totally aware of
the choices we made and the rules we
broke.
Java itself is a very generic
programming language and not
originally designed for web
application development. It is a very
different thing to write a generic and
reusable Java library and to create a
web application. A web application
itself doesn’t need to be designed to
be reusable. You need less
abstraction, less configuration.
Reusability does exist for web
applications, but through web service
APIs rather than language-level
integration.
When the development time tends to
zero you can concentrate on your
application features and experiment
quickly, instead of trying to abstract
things for future developments.
Play! applications can be deployed as web application on other web server containers, but it is mainly designed as a full stack framework; Play is the platform. And, in my opinion, this is what makes it beautiful and fast.

Checkout Guillaume Bort's blog. (Founder of Play!Framework). He explains it all on his blog.
EDIT : The link has changed, thanks procrastinate_later

WHich is the best path or flow to learn java from web site perspective

I have just started learning java and i have about 8 months time. My main aim is to build web application using java. But as there are many java technologies/frameworks available i am conufused how should i go
IDE i am using is eclipse
The path which i am thinking is below
1)Learn Core Java
2)Project: Build Java Invoicing System with JDBC or mysql to test java knowledge
3)Learn Servlets / JSP to
4)Build small site like simple logon/memberarea/catalogue using servlets/jsp
Now guys I really don't know where the following things stand in my path and which things they will help
1)Java EE
2)Spring or spring MVC, what's the difference?
3)Hibernate
4)Wicket
5)Struts
I really don't know how should i learn those and which things to choose from.
what should be my final project which can be build using those because if i see from my current stage even website can be build using servlets/jsp. then why do i need those other technologies
Can anyone give an example of a project which can be build using new technologies and not using jsp/servlet, so that I can get an idea why we need those?

Lot's of stuff to learn in here so I would take it a bit at a time. I'm going to assume you are relatively comfortable with the Java language and core APIs.
First learn about JDBC and databases. Get a basic functional JDBC example app working (not visual just some a vanilla Java app) that does read/insert/update/delete of some records in a table. This will give you the basis for building whatever app you choose. Almost all interesting applications involve some sort of persistence/database.
Learn the main JDBC APIs (Connection, PreparedStatement, ResultSet) and write some code that uses these to get comfortable.
Learn about how transactions work in databases if you aren't familiar already and how JDBC uses them (Connection.commit and rollback)
Next you could look into the spring framework. This has a several useful features that come in handy when building these applications. The main ones to get to know the dependency injection functionality and the JDBC libraries it has. The DI stuff is a bit of a "duh"? if you haven't used it before but it is very useful/powerful especially for medium size + apps. The JDBC libraries help with the cruft of dealing with the raw JDBC APIs and make your code less error-prone.
Once you've got some basic JDBC and Spring stuff worked out you can then start bringing in a web framework.
This is more difficult because there are so many. In the interest of getting something up and running quickly I would probably go with Wicket. It runs inside a servlet container like Jetty, easy to get up and running with a basic web page or two and relatively easy to evolve of the project over time without going down too many blind alleys. I've found that frameworks like JSF (the Java EE default web/view framework) takes a lot of up front time investment to get going on. Most of these frameworks, including Wicket, can leverage the spring stuff you've got above.
Avoid JSP, it's unpleasent technology and outdated by virtually everything else.
To answer some of your other points.
Hibernate is a tool for mapping an object model to a relational model. In it's most basic form you define a Java class for each DB table with the class having one Java property (variable+getter+setter) for each DB column. You can also add references from one class to another to model database relations. It is good but it takes a bit of getting used to.
Spring I've explained partly above. Spring is much bigger than just DI and some JDBC libraries. It also has transaction management libs and bunch of other stuff. Spring MVC is a web framework which lives under the spring umbrella and makes use of a lot of the spring libraries internally. I've never used it so can't offer an opinion on it.
Java EE is an umbrella term for a large set of "enterprise" specifications/libraries. JSF is a web view framework that is part of Java EE.
That's my very high level advice. To summarise I would learn basic DB/JDBC then some spring stuff and then start building a basic web app using what you've learned already.
Hope that helps. There's plenty of info out there on the web on all these topics and you can always ask questions here on more specific parts if you need help. Good luck and enjoy!
EDIT (to address comment):
All of the above is my recommendation/opinion on how to approach learning Java web development.
In summary
Learning JDBC/transactions/databases is a must
Spring is optional but I strongly recommend. Spring is a big library but you can pick and choose the bits you like/need.
Web frameworks the choice is really yours. From what I have tried (JSF/JSP/Wicket) Wicket is the easiest to get going with so you don't spend too much time frustrated with the getting the initial setup. JSP is awful, it's very easy to make a mess with it. JSF is powerful but heavy and probably more suited to very enterprisy projects than a first web app.
Hibernate is optional but can make life easier simply because you can work with Java objects when you do DB queries/updates rather than writing tedious insert/update statements. Hibernate isn't the only tool like this but it's the one I've used most and does the job well. Just don't go too overboard with the "clever" hibernate features initially.
You could easily use Spring MVC instead of Wicket. That may be a perfectly good choice, I've not used Spring MVC myself so can't comment. I'm sure it will integrate well with spring stuff tho so that would certainly be a positive factor.
Do some more research if you're not sure, there's no end of people happy to give their opinion! But really you just have to dive in and try something.

You are correct. If all your applications are served by servlets, JSPs, and JDBC, then maybe you don't need to learn anything else.
I commend you for learning the fundamentals first before diving into a thicket of frameworks that you don't understand. That's a good thing.
But if you reach the point where you have those down cold, maybe looking at these other technologies can help you improve your game.
1)Java EE
You are learning (part) of Java EE when you use servlets, JSPs, and JDBC. They're a subset of the full Java EE machinery - EJBs, JMS, JNDI, etc.
2)Spring or spring MVC whats
difference
Spring is an alternative framework developed by Rod Johnson and Springsource, now part of VMWare, that is based on dependency injection, aspect-oriented programming, and framework modules. Spring web MVC is one module in the Spring framework, based on servlets, that acts as the front end for web applications.
3)Hibernate
An object-relational mapping technology (ORM), built on top of SQL and JDBC, that lets you map objects to tables. It has its own object-based query language.
4)Wicket
Another web MVC alternative to Spring MVC, Struts, JSF, etc.
5)Struts
The first web MVC framework. It's gone through versions 1.0 and 2.0, and has now been supplated by Java Server Faces. It's still used, though. Like all other web MVC frameworks in Java, it's based on servlets and JSPs.

From a Java perspective it might be best to start looking at Java EE. All the others you mentioned are alternative technologies, which might be useful to you if you decide that what the standard framework offers isn't your cup of tea. But for that to decide, it's never a bad idea to at least know what the standard framework is about.
Truth be told, before 2006 the standard framework had a bad reputation and some of the sentiments that form the basis for recommending alternative technologies are still based on that. Starting with version 5, Java EE got dramatically better. The latest version, Java EE 6 is arguably one of the best Java frameworks that's out there. Of course, the best is a highly subjective term and naturally it won't be the best one for each and every person out there.
At any length, Java EE 6 is a very complete framework that allows a large range of application to be written without depending on any additional library. Being the standard framework, most other frameworks at least depend on some parts of it.
Most typically EJB, CDI and JSF are replaced by alternative technologies. E.g. the core Spring container replaces EJB and CDI and Spring MVC replaces JSF. A full Spring stack typically still uses JPA, JTA, JMS and Servlet from Java EE. Wicket on its turn only replaces JSF, or when used with a Spring stack replaces Spring MVC.
Hibernate is a special case. It doesn't replace anything from Java EE, but is instead often used as an implementation for one of the key APIs of Java EE: JPA. The original creator of Hibernate, Gavin King, is one of the prime supporters of the Java EE framework and is in fact the spec lead of one of the most important parts of modern Java EE: CDI.
Wicket by itself is a very nice web framework, but in practice it isn't used as often as JSF. I won't go into the discussion whether Wicket or JSF is 'better' (this is mostly a religious battle anyway), but due to the popularity of JSF there are simply more people experienced with it and there is a large community offering many things for JSF like component libraries and extensions.
Struts has historically been completely replaced by JSF. The original creator or Struts, Craig Mcclanahan, was the one who started JSF as the successor of Struts. Nevertheless, Struts was once the absolute de-facto standard for web frameworks in Java. It's not often advised to be used for new projects, but till this day it's still used in a huge number of existing applications. So even though it's not really 'hot' to learn Struts anno 2011 knowledge of it may still be very practical for when you have to maintain existing applications.
ps
See this answer for a general description about Java EE: Frameworks for Layering reusable Architectures

I'm sure that nobody seriously can tell you the best way, because this would mean that (s)he would have tried all. Why do you want to learn a Java web application framework? Just to learn it to be prepared for the (next) job? In that case it is likely that you've learned the wrong one.
The next question would be what you want to do with the web application framework. Do you want to make a website a little bit active, e.g. make each page look similar (corporate design), auto-generate menus from an internal structure, or do you want to write a real web application, e.g. with database access.
I'd first define the goal what you want to achieve. IMHO a good way to motivate you to make it right is to take a small project which helps you to solve a small problem.
Then I would start with Java Server Pages (JSP) and servlets to understand the basic concepts. Then you can try to do the same with a few well-known web application frameworks, e.g. Wicket.

study roadmap for newcomer into java ee

I'm the newcomer into java ee,I have studied about core java,servlet,jsp.
Could anyone give me some suggestion(some books,forums,etc) on how to promote my skills into java ee?
Thanks a lot in advance.

One good place to start is Sun's Java 6 EE Tutorial on the Sun web site.

I would recommend Server-Based Java Programming. This isn't a Java EE book per se, but it explains what a Java based server needs to do and how to do it with good example code. It will give you the foundation to understand to understand what Java EE is trying to accomplish and why things are the way they are.
In the same vein, I would recommend Expert One-on-One J2EE Development without EJB. This book is written by the founder of the Spring project and provides insight to the problems with Java EE that Spring is trying to solve. Note this was written before Spring was open sourced, so it's more a 'this is how a server framework that's not Java EE could work' book, not a 'how to use Spring' book. Even if you are using straight Java EE, it helps to know what issues you could run into (with J2EE) or what the motivations were for Java EE 5 (based on Spring & Hibernate philosophies).
I would not recommend the actual specifications from Sun. They are dense, technical and better used as a reference.

To be an effective J2EE developer, you'll have to have a few frameworks under your belt. Start boning up on Spring, JSF, Hibernate, etc.
For more details, see my answer to this question.
Spring is an excellent first choice of framework, for reasons that may not become apparent until you've used it on a large project. But the best tutorial I know for learning it is Manning's Spring In Action.

web applications -- where to start?

I'm fairly new at webapp development in Java and have been looking around for a decent tutorial on this subject. I've found a whole bunch of frameworks from struts to seam. Which framework should I look at considering my level of expertise in this area is fairly low?
Also is there a global tutorial on web application fundamentals?

Java EE tutorial covers the basics of web applications.
As far as frameworks go, take a look at this question

I would suggest to learn Seam as it builds further on JSF, an industry standard.
It is also one of the newer and better web application frameworks available in the Java landscape today.
Furthermore, it has great support for both EJB3 and simple pojo development.
You should also do some background reading about servlets.

I cannot help you with Java, but here is a link to an excellent SO post that will help you with the second question.

If you want something easy for web applications development I would highly recommend grails. Other frameworks are good but learning curve and configuration complexity is high. Most of the time you will find against them.
With Grails you will have application up and running in few minutes.

I'd focus on learning HTTP/HTML first - you need to know the basics of static web development before building dynamic web applications.
Then just do some basic Servlets and JSPs - all other Java web frameworks are built on this - and if you jump right into higher level frameworks, sooner or later you're going to run into an issue you need to debug / develop that's going to require knowledge of how the underlying servlet / JSP APIs work.
After you learn the basics start looking at other frameworks built on top of this to see what they offer.