I am learning the REST architecture these days. I have developed many small small projetcs using jersey. My question is what exaclty is JAX_RS ? I understand that JAX-RS is a set of interfaces (all the javax.ws.rs.* classes) which contains annotations like GET,POST and a lot more. Jersey is one of the bundle which has classes which implement those methods. My doubt is if we download java , do the JAX_RS interfaces come with that ? I have used maven to build REST. There i have seen a lot of entries being added to pom which does my job, but i want to get the actual feel of what exactly is this JAX-RS. Any help is appreciated ! sorry if this is foolish !
JAX-RS is just a specification. A specification specifies how such a framework should work (in a PDF file), and provides different Java interfaces and annotations and enums (like javax.ws.rs.* classes), but no functional code.
The URL for JAX-RS specification are:
JAX-RS 1.1 (you probably use this one) https://jcp.org/en/jsr/detail?id=311
JAX-RS 2.0 https://jcp.org/en/jsr/detail?id=339
Along with the specification there are implementations of that specification, which is functional code (java jars), that you can use in your applications. Such implementations are JERSEY and RestEasy (usually applications use only one).
Now what you need is a JAX-RS tutorial. Take the first two results from google:
http://docs.oracle.com/javaee/6/tutorial/doc/giepu.html (I find this one very good)
http://www.vogella.com/tutorials/REST/article.html (this one is very comprehensive, IMHO)
Related
I am using Guice as my dependency injection framework. I'd like something that I can add that will make creating REST services easier.
I've had a look at guice-servlet and it works well for directing paths to HTTP servlets, but that's all it appears to do, I was expecting a JAX-RS like annotation syntax to work but it doesn't.
Having not actually used JAX-RS I've googled around and it appears that Jersey is the reference implementation for this but it looks like it uses its own dependency injection framework and doesn't work well with Guice. In addition it has 5+MB worth of dependencies which seems alot for what I am after.
Is Guice designed in such a way that it doesn't lend itself to JAX-RS, if so what else should I be doing?
I think that maybe the guice-servlet module has misguided you. Guice is a DI framework. Period. The real goal of the guice-servlet module is not providing the servlet's and filter's shortcut declaration but giving support for the special scopes request and session. Those nice shorcut declarations are syntatic sugar.
Chosing a JAX-RS implementation in Java is a bit out of the question. You have several options (Jersey, Resteasy, Spring...). If you are going full JavaEE then you don't have to choose. You just use the annotations (and the DI) out of the box.
If you are not using a JavaEE server (just a web server like Tomcat or any other fancy thing like an Android app) then you must choose your implementation. If you are using DI also (which I recommend) then there is one more decision to make.
So you are not using JavaEE and you want to implement some REST API using JAX-RS and dependency injection. You do some research and end up choosing Jersey and Guice. Good choice, I've chosen those in my last projects too. Yes, the dependency graph of Jersey is a bit bloated. I know, it could be way better.
Now your problem is how to make it work together because Jersey uses it's own DI framework (HK2) which is a bad thing.
You have a lot of references on SO about Jersey-Guice integration. Your best bet is the Guice HK2 bridge.
What? You want a direct reference on SO? No problem, here is a good one. Don't forget to upvote the answer. ;-)
Jersey and Google Guice integration
I've created a RESTful web service using jersey and JAX-RS annotations. It's also documented using enunciate and looks great. However, SOAP support has been requested as an option. I noticed in this outdated enunciate example JAX-WS and JAX-RS annotations in the same class. Is this possible? I've tried it myself and enunciate generates documentation correctly, but the services don't actually work.
I'd prefer to have the exact same class support both interfaces rather than two separate classes (one soap one rest) pointing to the business logic class. This would prevent possibly having code in two places.
Here's the example on outdated software versions:
http://docs.codehaus.org/display/ENUNCIATE/A+Rich+Web+service+API+for+Spring
I'm using
Jersey 1.8
Spring 3.0.5
Weblogic 11g
Thanks!
/Chip
I'm not sure what might not be working, but a lot of the Enunciate example modules use both the SOAP and REST annotations on the same class.
Here's one for Jersey/JAX-WS.
Here's one for JBoss WS/RestEasy.
Here's one for CXF.
We ended up making a separate service for SOAP than the REST service. We also found it best to have interfaces for each that enunciate could generate from. This way we could control what documentation it generated. It also started functioning smoother. Still having a problem with the namespaces though as they're all default and ns0 is generated but enunciate links are to ns2/3/4/5/etc. So many links are broken.
For example, Play-framework supports RESTful services like this: RESTful on Play! framework
How does this compare to something like Jax-RS Jersey implementation? Does a framework like Play run circles around Jersey because of all it's cool bells and whistles, and it does REST too?
Developer productivity is important, but so is a proper implementation. Perhaps using an MVC framework for REST only services is 'wrong'?
Note, only RESTful services, no UI components at all.
Even though it's not "wrong" to use an MVC framework for RESTful services, there are some pros and cons versus using a JAX-RS implementation.
(Disclaimer: I have only used Jersey and Play! for fun, and not on production-grade systems, so I have tailored my comments more generally to MVC vs. JAX-RS. Keep in mind that these are broad generalizations.)
MVC frameworks--at least the ones that are considered developer friendly and "slick"--typically save you from having to build a persistence layer (the model part). Most also simplify "routing" requests using either scaffolding via convention or some form of configuration. The downsides are that you have to conform to some conventions for your controllers and usually have to write a view for each resource (or build layers of abstractions to avoid rewriting the same code).
JAX-RS excels at defining the routing (using Java annotations) as well as eliminating any restrictions on the service class. In my experience, that has greatly reduced the amount of boilerplate code and developer overhead. Jersey and Apache CXF also handle the XML or JSON serialization using JAXB annotations, which eliminates the need to figure out the view in an MVC context. The downside here is that you have to figure out your own ORM or persistence layer, which could be good or bad depending on whether you're building on top of existing data or creating a greenfield system (or using something other than an JPA/RDBMS e.g. NoSQL data store).
My own personal comment: Play! is a really cool framework, but I'd choose CXF (or Jersey) over an MVC framework any day for building out a RESTful service. In my experience, this frees up the developer to focus on the logic needed for the service, and opens up options for different database approaches. Right tool for the right job.
As a rule of thumb: For Scala, use Play. For Java, use Jersey.
You can use Jersey/Scala and Play/Java; I've done both. It works. It isn't bad. But unless you have a particular reason to do that, I wouldn't mix ecosystems. Java and Scala are interoperable but they have different ecosystems, I would avoid adding Java-isms if you are using Scala or Scala-isms and dependencies if you are running straight Java.
Jersey and Play are generally close for REST services. Neither really has any killer features over the other.
Jersey defines URL mappings in annotations, Play defines them in a service wide route file. And they bundle or have varying quality of integration with different libraries for things like XML, JSON, database, testing, mocking, dependency injection libraries and app server deployment.
The Java world has JMS, Spring, JUnit, jdbi/hibernate/jpa, Jetty/Grizzly. The Scala world has Akka, specs2/ScalaTest, Anorm/slick. Jersey is a better fit for the first world, Scala for the second. You can definitely cross that, but it will be a little less elegant and might require more glue coding.
JAX-RS is a standard and implementations can be created by different vendors. Jersey is one such implementation. The other frameworks may make use of JAX-RS but are not standards. So it is not a one-to-one comparison.
I have never heard of Play before but it does look interesting, more akin to Rails and Django than Jersey. What I like about Jersey is that it can be integrated into existing Java web applications by simply adding the JARs and declaring some things in the web.xml. What I find confusing about Jersey and JAX-RS is the routing.
Play seems to make routing easier, however, correct me if I'm wrong, seems like it is an all-or-nothing framework and cannot be used alongside other servlets in the same web application.
I have been trying to figure out how to use JAX-RS for quite some time. I started from the very basic concepts and then to gradually understand the annotation styled programming, the meaning of #Path, #Get, #Post, etc.
To my understanding, as to what has been mentioned in a lot of places, JAX-RS is a framework that focuses on applying Java annotations to plain Java objects (Page 27, Bill Burke, RESTful Java).
I have then got confused beyond this point. If JAX-RS in itself is a framework that defines APIs dealing with annotations in order to implement RESTful web service, what's the meaning of "implementation of JAX-RS" such as "Jersey" and "JBoos Resteasy". Another layer on top of JAX-RS? Why do we need them?
Could someone provide me some insights about it? Many thanks!!!
JAX-RS is a standard defined in Java Specification Request 311 (JSR-311) and Jersey / RESTEasy are implementations of it.
Being implementations mean that the spec says "if you put #GET("/foo") on a method (bar()), you may access data X" - now in an app server, someone needs to go in and actually read your deployed code, parse the byte code with the #GET annotation and then if the user actually browses to e.g. http://localhost/foo get this web request to reach bar() and translate the return value of bar() into a http answer (e.g in XML or JSON representation).
So the spec with the name "JAX-RS" only provides the syntax and semantics of e.g. #GET, but the work of parsing requests, calling the right methods, marshalling the result values etc. need to be done by a package that implements the Spec.
Work on the version 2.0 of the standard has started as JRS-339.
See also http://en.wikipedia.org/wiki/Jax-rs
JAX-RS is a specification for RESTful Web Services with Java. There is a reference implementation that is included in Java EE but since it is a specification, other frameworks can be written to implement the spec, and that includes Jersey, Resteasy, and others.
My question is very simple, my intention is to generate a repository with your responses so it could serve to the community when selecting frameworks for developing enterprise general purpose applications.
This could apply very well for general purpose languages such as C++, C# or Java.
What Framework do you recommend for generating Layered Architectures?
Based on you experience why do you prefer the usage of some Framework versus your own architecture?
How long do you believe your selected Framework will stay as a preferred option in the software development industry?
This is indeed an overly general question, especially since there are so many interpretations of the very word framework, and within the world of frameworks many different kinds for different tasks. Nevertheless, I'll give it a shot for Java.
Java
Java EE
The default overall enterprise framework of Java is called Java EE. Java EE strongly emphasis a layered architecture. It's a quite large framework and learning every aspect of it can take some time. It supports several types of applications. Extremely small and simple ones may only use JSP files with some scriptlets, while larger ones may use much more.
Java EE doesn't really enforce you to use all parts of it, but you pick and choose what you like.
Top down it consists of the following parts:
Web layer
For the web layer Java EE primarily defines a component and MVC based Web Framework called JSF - JavaServer Faces. JSF utilizes an XML based view description language (templating language) called Facelets. Pages are created by defining templates and letting template clients provide content for them, including other facelets and finally placing components and general markup on them.
JSF provides a well defined life-cyle for doing all the things that every web app should do: converting request values, validating them, calling out to business logic (the model) and finally delegating to a (Facelets) view for rendering.
For a more elaborate description look up some of the articles by BalusC here, e.g. What are the main disadvantages of Java Server Faces 2.0?
Business layer
The business layer in the Java EE framework is represented by a light-weight business component framework called EJB - Enterprise JavaBeans. EJBs are supposed to contain the pure business logic of an application. Among others EJBs take care of transactions, concurrency and when needed remoting.
An ordinary Java class becomes an EJB by applying the #Stateless annotation. By default, every method of that bean is then automatically transactional. Meaning, if the method is called and no transaction is active one is started, otherwise one is joined. If needed this behavior can be tuned or even disabled. In the majority of cases transactions will be transparent to the programmer, but if needed there is an explicit API in Java EE to manage them manually. This is the JTA API - Java Transaction API.
Methods on an EJB can easily be made to execute asynchronous by using the #Asynchronous annotation.
Java EE explicitly supports layering via the concept of a separate module specifically for EJBs. This isolates those beans and prevents them from accessing their higher layer. See this Packaging EJB in JavaEE 6 WAR vs EAR for a more elaborate explanation.
Persistence layer
For persistence the Java EE framework comes with a standard ORM framework called JPA - Java Persistence API. This is based on annotating plain java classes with the #Entity annotation and a property or field on them with #Id. Optionally (if needed) further information can be specified via annotations on how objects and object relations map to a relational database.
JPA heavily emphasizes slim entities. This means the entities themselves are as much as possible POJOs that can be easily send to other layers and even remote clients. An entity in Java EE typically does not take care of its own persistence (i.e. it does not hold any references to DB connections and such). Instead, a separate class called the EntityManager is provided to work with entities.
The most convenient way of working with this EntityManager is from within an EJB bean, which makes obtaining an instance and the handling of transactions a breeze. However, using JPA in any other layer, even outside the framework (e.g. in Java SE) is supported as well.
These are the most important services related to the traditional layers in a typical enterprise app, but the Java EE framework supports a great many additional services. Some of which are:
Messaging
Messaging is directly supported in the Java EE framework via the JMS API - Java Messaging Service. This allows business code to send messages to so-called queues and topics. Various parts of the application or even remote applications can listen to such a queue or topic.
The EJB component framework even has a type of bean that is specifically tailored for messaging; the message driven bean which has a onMessage method that is automatically invoked when a new message for the queue or topic that the bean is listening to comes in.
Next to JMS, Java EE also provides an event-bus, which is a simple light-weight alternative to full blown messaging. This is provided via the CDI API, which is a comprehensive API that among others provides scopes for the web layer and takes care of dependency injections. Being a rather new API it currently partially overlaps with EJB and the so-called managed beans from JSF.
Remoting
Java EE provides a lot of options for remoting out of the box. EJBs can be exposed to external code willing and able to communicate via a binary protocol by merely letting them implement a remote interface.
If binary communication is not an option, Java EE also provides various web service implementations. This is done via among others JAX-WS (web services, soap) and JAX-RS (Rest).
Scheduling
For scheduling periodic or timed jobs, Java EE offers a simple timer API. This API supports CRON-like timers using natural language, as well as timers for delayed execution of code or follow up checks.
This part of Java EE is usable but as mentioned fairly basic.
There are quite some more things in Java EE, but I think this about covers the most important things.
Spring
An alternative enterprise framework for Java is Spring. This is a proprietary, though fully open source framework.
Just as the Java EE framework, the Spring framework contains a web framework (called Spring MVC), a business component framework (simply called Spring, or Core Spring Framework) and a web services stack (called Spring Web Services).
Although many parts of the Java EE framework can be used standalone, Spring puts more emphasis on building up your own stack than Java EE does.
The choice of Java EE vs Spring is often a religiously influenced one. Technically both frameworks offer a similar programming model and a comparable amount of features. Java EE may be seen as slightly more light-weight (emphasis convention over configuration) and having the benefit of type-safe injections, while Spring may offer more of those smaller convenience methods that developers often need.
Additionally Spring offers a more thoroughly and directly usable security API (called Spring Security), where Java EE leaves a lot of security details open to (third party) vendors.
To specifically answer the second question:
Developing your own framework gives you the burden of having to maintain it and educating new developers in using it.
The larger your framework becomes, the more time you have to devote specifically to it and the less time you thus have to solve your actual business problem. This is okay if your business problem is the framework, but otherwise it can become a bit of a problem, even for very large companies that can dedicate a group of people to such a framework.
If you're a smaller company (say ~15 developer max) this can really become a huge burden.
Additionally, if your own framework is the kind of framework that can take advantage of third party developments (e.g. third parties can develop components for JSF), then your own framework obviously won't be able to take advantage of that.
Unless of course you open source your own framework, but this will only significantly increase the burden of supporting it. Just dumping your source code on sourceforge does not really count. You will have to actively support it. All of a sudden your framework becomes their framework with maybe 'weird' feature requests and awkward error reports for environments that you have no personal interest in.
This also assumes that your framework will actually be used by external users. Unless it's really very, very, good and you put lots of energy in it, this will probably not happen if it's simply the umpteenth Java web- or ORM framework.
Obviously, some people have to take up the job of creating new frameworks, otherwise the industry just stagnates, but if your prime concern is your business problem I would really think twice of starting your own framework.
Very vague question, I'm not really sure it's ever a good idea to "write your own" at this point for a work project (unless writing your own, IS the project). If it's a learning exercise, fine, but otherwise go use one of the libraries written by people who have been doing it far longer. If you really want to get involved, read their code, try and contribute patches etc.
For .Net there is Sharp Architecture Which is a pretty popular framework for layered applications.
Here's some of the stuff I use (I don't use Sharp Architecture)
First, the infrastructure stuff
For Dependency Injection, I use StructureMap. I use it because it's way more robust and performant than anything I would or could write, and it's very well supported within the .Net community. It also sticks to being DI, and doesn't venture out into other things that I might want to use other libs for (AOP etc). The fluent configuration is fantastic (but many .Net DI Tools have that now)
For AOP, I use Linfu Dynamic Proxy. I know a lot of people that like the code weaver variety for performance reasons, but that's always seemed a bit like premature optimization to me.
For a DataMapper, I use AutoMapper. This is one where I'm on again off again. If you can do your mappings based just on convention, then great, I'll use it. Once I have to start tweaking the configuration to do special things.... to me that starts to get into the gray area where the code might be more clear with just some left=>right wrapped in a function.
Web/UI
Asp.Net MVC. Although to be quite honest, I'm having a falling out lately and may soon be moving to FubuMvc. Asp.Net MVC seems like it has split personalities in terms of API design (dynamic over here, static over there, using blocks to render forms, but System.Actions to render other things etc). Combine that with the fact that it's not really OSS (you can't submit a patch), and to me there's a compelling reason why the community should come up with something better that's OSS.
Persistence
NHibernate, Specifically Fluent NHibernate. Sure I'd love to write my own OR/M, but at the same time I'm certain that the hordes of developers who have worked on NHibernate are way smarter than me.
Services/Distribution etc
WCF for Synchronous calls
NServiceBus for Messaging and most async calls.
Most of this stuff is OSS, so how long will it be around, well, I would imagine a good long while.
This question doesn't work very well. Selecting frameworks is difficult, and very context specific. For each selection process you might end up with a simple shortlist and a simple list of questions to answer, but those lists do not transfer well to other selections.
The number of parameters and the parameter sensitivity influencing a decision is very large, and at enterprise level a lot of them are not technical.
Currently, there are no frameworks available that are ready to support these near-term enterprise needs:
the switch for most of the workforce from pc to tablet and phone;
the switch from web client and rdbms to p2p/disconnected based storage and distribution