I have worked on RESTful Web Services at a high level (not very exhaustively), coded few REST based web services.
To begin my journey in RESTful WS, I read online articles (wiki, online tutorials etc.) and I came to know that it is an architectural style specifying constraints and when applied to web service induce desirable properties, such as performance, scalability etc. Ok, this is the theory part of this concept.
A simple example using JAX-RS:
#Path("/simple")
public class SimpleRESTService {
#GET
#Path("/{param}")
public Response getMsg(#PathParam("param") String message) {
String output = "Jersey say : " + message;
return Response.status(200).entity(output).build();
}
}
My doubt is:
If REST is architectural style (and using those guidelines build RESTful web services), what does JAX-RS do? To what I understood, REST is just architectural style and not any specification, what does JAX-RS has to do with this? I am having difficulty in understanding the relation between these two entities.
Can anyone help me understand this in simple words.
REST is indeed an architectural style of building web services independent of application-layer protocols (it could be implemented over FTP or HTTP as well).
JAX-RS is just a standardized API of Java EE with which you can easily implement RESTful services in Java. It is a toolkit for a developer to lift the burden off his shoulders, and as part of Java EE, it is implemented in application servers such as WildFly out of the box.
But note that it is just as possible to create REST services in frameworks like Spring using the Spring Web MVC and Spring HATEOAS modules.
Edit:
Although REST is a well-defined architectural style, it is (as you mentioned) not a specification so there is a lot of foggy areas about it among developers.
In a nutshell, all it states is "Hey man, if you use the communication protocol (say HTTP) this way and this way, it will be very convenient for you to change and scale and it will be very straightforward for the clients of your service to talk to you".
JAX-RS gives you the ability to define service endpoints with dynamic parts (eg.: /api/jediknights/{id}, so that the id could be anything), makes it easier to respond to the client in the format of your (or your client's) desire, like XML or JSON. It provides convenient wrapper objects to wrap your response body along with status codes and headers and many other things of convenience.
The catch however is: it is still your responsibility as a developer to adhere to the principles stated by the REST style. Nothing is really enforced upon you by JAX-RS.
To be fair, you could even achieve a RESTful web service by only using the somewhat lower-level Servlet API. JAX-RS just hides the unnecessary details from you and will make your life easier.
I hope it became a bit clearer :)
Java API for RESTful Web Services (JAX-RS), is a set if APIs to
developer REST service. JAX-RS is part of the Java EE6, and make
developers to develop REST web application easily.
You can read some more here: http://www.mkyong.com/tutorials/jax-rs-tutorials/
Related
I have started working on web application using jquery touch. My web services is written in soap and I want to call from my application. Can you suggest me how should I move ahead.
Is it possible to call from ajax?
While many people thinks that managing the complexity of SOAP in a JavaScript environment would be counter-productive, it could nevertheless be done, in particular if you are familiar with SOAP web-services and want to avoid the need to learn another middle-layer framework; a library that I would suggest is Apache-CXF support for JavaScript.
The CXF JavaScript client library is indeed a code generator which (with some limitations), in its easiest form, wsdl2js, gets a wsdl file and generates JavaScript
contructors - for an service
methods - for any service operation, and
objects - for any web service complex element/type
which can be directly called in your scripting. Other available tools generate the javascript code starting with the Java code server-side implementation (java2js), or on-the-fly (dynamic javascript).
Pros:
leverage a component of a widely used library for web-services implementation (CXF)
avoid another layer in the middle
easy to use (run the tools against the wsdl, load the generated sources)
Downsides:
client knows nothings about WS urls and ports; you need the URL at which the ws ranswers and thats'it
as a code generator, the JavaScript client generator is parallel to JAXB or JAX-WS. It defines a mapping from an abstract model of a web service to JavaScript objects. Unlike JAXB and JAX-WS, there is no committee that has standardized a 'JavaScript binding.' The CXF binding may not be to everyone's tastes.
Soap 1.1 only
No Authentication support
Using soap from the browser is technically possible, but a very bad idea. You'll spend all your time fighting to get the soap protocol to work correctly and you'll miss all the benefits of soap.
A much better approach would be to build a back end for your new web application using the framework of your choice, eg. J2EE, .Net or any other. All those platforms have nice soap libraries that will do the work for you. Then you will either generate the html pages on server (old school web site) or use a static page and expose the data as a JSON rest API (modern single page app).
In summary: soap is good for communicating between servers, terrible for communication with the browser.
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Closed 10 years ago.
Possible Duplicate:
WSDL vs REST Pros and Cons
can any one explain what is the difference between Restful web services and WSDL(Web Service and Description Language). And which one is more secure and how?
Thanks
WSDL is used to describe SOAP services. You're really asking for a comparison of SOAP and REST.
There is no inherent security difference between SOAP and RESTful services. Most likely any security issues will be with your specific implementation of them.
SOAP is more like RPC - it focuses on calling commands on a remote server. REST is resource oriented - you interact with the server by adding, retrieving, updating and deleting resources on the remote server, which corresponds to actions.
eg. With SOAP service you might call an updateAccount(account_id, details) method to save changes, but with a REST service you might PUT information to /account/<account_id>.
In Java, JAX-RS is a good place to start with RESTful services.
WSDL "Web Services Descriptor Language" is the standard for defining the content and behavior of SOAP based web services. It is part of a collection of WS* standards that define "Web Services". These standards cover discovery, transport, message format, authentication, non-repudation etc. etc.. These are formal standards managed by W3C.
REST is a style of network programming where every request is made in the form of a valid URL to identify the "key" of the object in combination with an http GET, PUT, POST, or DELETE action to identify what you want to do to it.
REST is a style rather than a standard messages can be in XML, JSON or any format you choose.
My opinion is that REST is great for doing simple things simply. SOAP etc. is great for complex "enterprise" level interactions with sophisticated security and workflow requirements, but, its overkill for simpler services.
As for security REST does not help you. But using standard web security (sessions, cookies, SSL etc. ) you can secure a RESTful service pretty well.
SOAP has built in bulletproof security but its configuration heavy requiring LDAP servers and managing public/private key pairs. Unless you really need it its best left alone.
Evening all :)
I'm looking to create a Java web application. I envisage that it will use Spring web MVC and JSPs, however I would like to expose certain functionality as REST calls so I can create an android client.
Does spring offer anything to help me in this area? How can I keep the REST code and the web front end code separate yet not have to maintain essentially 2 versions of my application (one for the web, one for REST clients).
Not looking for spoon feeding, just some pointers of where I should start reading.
As others have mentioned, Spring has pretty good in-built REST support now. When combined with annotations, this allows really simple set-up of a RESTful API. Spring can be configured with different view resolvers, which can automatically respond with a different view of the data depending on the Accept header for example. So you could return either JSON or JSP automatically from the same data, see the ContentNegotiatingViewResolver. Your Controller and Model can then be common and implemented once, leaving the work in the View layer.
I've used this approach before to return JSON when the request was via AJAX and a JSP view built with the same data when accessed by a browser.
Jersey is a pretty nifty tool. It integrates well with tools like Spring, Guice, and Jackson to provide you a pretty seamless way to create RESTful resources.
Jersey is pretty simple, works well, and serves as the reference implementation to boot. Plus, it has some nice REST client support, much of which will probably make it into the JAX-RS spec.
In terms of marrying that with Spring MVC, I'd recommend you make sure you model your application so that you have facades (Service classes) that provide all the core functionality you need and then simply reference them as needed in your MVC code or REST code. You shouldn't be duplicating business logic
You can do this using Spring 3.0. Spring 3.0 came out with the ability to specify #PathVariables to pull values out of the URL path (previously this was not easy in Spring MVC).
You would also use #RequestMapping to specify the HTTP method(s) each method in your controller should respond to.
I've also use Spring Security to implement an API key type of functionality. This way you can restrict access to your API in a way that is easy for REST clients to implement. I had to extend org.springframework.web.filter.GenericFilterBean and add a the proper Authentication like this
SecurityContextHolder.getContext().setAuthentication(apiKeyAuth)
There's a new REST API in Spring 3.0 MVC:
http://blog.springsource.com/2009/03/08/rest-in-spring-3-mvc/
http://www.springsource.org/download
Apache CXF integrates well with Spring and offers many method for exposing services. From the overview section of the CXF homepage:
CXF helps you build and develop
services using frontend programming
APIs, like JAX-WS and JAX-RS. These
services can speak a variety of
protocols such as SOAP, XML/HTTP,
RESTful HTTP, or CORBA and work over a
variety of transports such as HTTP,
JMS or JBI.
I am totally new to Spring Web Services and so what concept should I start concentrating on and where should I be looking for them and in general what steps would you recommend to get to speed with Spring Webservices Module.
Note: I have an requirement to build Web Service for and consume Web Service from different application and I have never worked with Web Service in the past, I am looking at Spring WS option because both application are developed using Spring Framework, is this a good assumption to look for Spring WS or not ?
Any guidance and suggestion for discussion kind of approach would be highly appreciated.
Thanks.
(...) I am looking at Spring WS option because both application are developed using Spring Framework, is this a good assumption to look for Spring WS or not?
It's not a wrong assumption (bad integration between Spring WS and Spring would be a total irony) but you should not exclude other stacks on the fact your applications are using Spring. JAX-WS stacks (like Apache CFX or JAX-WS RI) provide Spring integration as well.
Personally, I like JAX-WS (that I use for contract-first web services) and, while it's hard to be more specific without more details about your requirements, I simply don't think that Spring WS offers any advantages over JAX-WS and I would probably go for Apache CXF in your case.
Maybe have a look at what others are saying in this previous SO question (please read all answers, the accepted one is not really good in my opinion).
What are your protocol requirements? Do you have to use SOAP, or are you free to use your own XML marshalling over HTTP (e.g. a RESTful approach)?
If you must use SOAP, then see this guide I wrote to Spring WS web services. If you're free to use your own lightweight RESTful web services, then see this example I wrote on RESTful web services.
I wouldn't use Spring WS ONLY because of the reasoning you provide. You need to identify more functional requirments like:
Can you use markup (JSON, XML, etc.)
Should you provide content negotiation
Do you need to provide complex objects (i.e. SOAP as james suggests)
Are you providing a RESTful service
etc.
I've worked with web services a lot in the past few years and there seems to be a few major projects for creating them:
Apache Axis (primarily SOAP)
Apache CXF (primarily SOAP)
Jersey (REST)
Restlet (REST)
There are other offshoots like Spring WS, or even Spring MVC, but you need to evalute which will work best.
Personally I use Jersey a lot, which also provides Spring integration. Jersey also has an awesome HTTP client for consuming services, but don't confuse creating a web service as being akin to consuming a web service. They are separate workflows and you could use separate third-party projects for both (e.g. Apache HTTP Client for consuming, and Jersey for producing).
Spring WS might work best for you, but my advice would be don't use it just because the other applications use it...use whatever works best and fulfills your requirements.
Though this might appear as a duplicate of Java Web Services , I would like to know Where to start and to continue.In the past, I have invested so much of time to find where to start but I wasn't able to. There are so many jargons and chaos (at least for me!) while reading the pages about web services. There are so many terms - like JAX-RPC, JAX-WS, Axis, Rest, Servlet as WebService, EJB's as Web Service and other terms that I don't know. Can this User group consolidate and give a highlevel overview of Java Web Services which is easy to understand and follow? I appreciate your kindness and thanks for your help.
That's indeed a bit a jungle to understand web services. The wikipedia page is decent, but still lacks some elements.
I've flagged this answer as community wiki, so feel free to update it, or correct it. It's only a basis.
A bloated term:
First, the term web service is used to refer to many thing. While many people use it to refer to SOAP-based web service, the term can be used to denote any service provided through a web interface; this is a source of confusion.
Implementation and design style:
SOAP-based -- SOAP is still the de-facto standard for web services. SOAP is protocol on top of HTTP that describes the exchange of message and exception. SOAP grew from something simple to something very complicated with all the WS-* standards that have been added later. The most important are: WS-Policy, WS-Security, WS-Addressing, WS-Transaction. Another important spec is MTOM for large message.
RESTful -- The term RESTful relates to the fact that the service is stateless and all relevant information is passed as parameter. Also instead of using a protocol like SOAP, plain HTTP verbs are used, e.g. Get, Put, Delete, Update.
Stateless -- WS are usually stateless. Business processed sometimes rely on so-called correlation identifiers (with WS-Addressing) that are used to match requests and response together; this is the same idea like storing a session identifier in a cookie because HTTP is stateless.
Stateful -- There are some proposal to have stateful WS, but I don't know much about it.
Implementation and technology stacks:
Servlet -- The lowest-level way to implement a WS: you basically parse the request and spit the HTTP response all by yourself.
EJB -- Since EJB3, EJB can be exposed as web service very easily. Needs an EJB container, of course.
Apache Axis -- Used to be a popular technology stack which is declining now.
Apache CXF -- Another popular choice.
JBossWS -- Yet another popluar choice.
JAX-WS -- The official web service stack from Sun, very good. So far I know, this replaces JAX-RPC which was simply renamed JAX-WS.
Related concepts and jargon:
WSDL -- Defines the contract/interface of the web service, in case of SOAP-based WS.
Contract-first -- Refers to the fact that that a technology is able to support any WSDL provided upfront. On the contrary to an implementation technology which will generate the WSDL based on the implementation of the web service, in which case the WSDL can not always be customized as necessary
Profile -- To simplify this mess, they've introduced profiles which are groups of related specifications/capabilities that need to be supported for interoperability. The main one is WS-I Basic Profile.
UDDI and discovery -- It seems like some people thought the web service would be published in a public register so as to be discoverable by potential consumer. I don't think this vision gained much momentum.
The best explanation I know for "contract first" web services is Spring web service module.