I work with REST service provided by RESTeasy. It's REST, so there is no WSDL, right? Does that mean that I have to write all entities on my own and do unmarshalling on my own?
If it would be rest service, I could just download WSDL and then generate client from it. How do i do it with REST, that is served as xml in Atom feed?
I don't really see any advantage in REST, if it has no way of generating client and doesn't provide any public specification of entities.
Thank you for your help.
Correct, with REST, there's no WSDL like there's with SOAP. That does not mean there's no unmarshalling directly to objects however. You can still use Jax-RS to bind the JSON/XML to an object, so you'll have the flexibility of mapping directly like you would in SOAP, you just need to build this class rather than letting SOAP build it for you.
Consider the example here
Related
I am new to web services in Java.
In SOAP web services, we have wsdl that tells us about the services like the operations etc. but in REST, we don't get wsdl.
So, my question is if someone wants to know the service details, then how that can be found in case of REST web services.
SOAP introduced WSDL to describe services, which can automatically be discovered and integrated with a mechanisms like UDDI. In reality SOAP is used just as hardcoded RPCs. If you use REST, many details like exceptionhandling, operation types, idempotency are handled using well known HTTP mechanisms. The only thing you need to know is the payload encoding. If you use XML, you may use XSDs to describe the services, if you use JSON you need to handle this on your own (its a lot simpler). The structure of your URLs should be designed so its intuitive enough, to be described in a one paged readme file.
To cut a long answer short: WebServices were so complicated you need a lot of boilerplating, REST services should be so simple, that a developr does not have to redefine and redocument the basics.
With REST there is no single established way to achieve this yet, however there are couple of options emerging:
Swagger http://swagger.wordnik.com/ - Inspects annotations in your source code (supports web frameworks JAX-RS annotations, Spring annotatins, Play2) and generates a JSON document describing your APIs. This JSON document can be displayed as an interactive web page as end user documentation using swagger-ui.
Json Home https://datatracker.ietf.org/doc/html/draft-nottingham-json-home-02 - Specification for a JSON document that describes your RESTful APIs
WADL http://en.wikipedia.org/wiki/Web_Application_Description_Language
I'm writing a bridge between two old application on our network. One has a webservice that takes URL encoded parameters (GET) and returns an XML document. Like this:
http://mytest.com/getData/?format=xml&dateStart=2012-01-01
My question is this - I can use the XSD for the xml returned and marshall it into Java objects (xjc defined).. but is there any way to map the requests/responses to a jax-ws webservice (or similar?) It's not SOAP - so I can't go the WSDL, CXF/JAX-WS route, can I?
I was really hoping for an elegant solution to this without having to code it all from scratch (URL request , returned stream, then marshal). Is there a framework out there that would allow me configure a request? I thought WSDL supported verb="GET" but sadly, I can't seem to get it working with Apache CXF and WSDL2JAVA.
Am I totally off base here?
I think JAX-RS may be of use here. Just create XSD schemas and convert them to Java classes, and use a REST client for that site.
You can probably do it with CXF too. See here.
Check out WSGen or you can add ?WSDL to the end of your JAX-WS endpoint to get the generated WSDL. This way all you have to do is create your JAX-WS annotated classes similar to your JAX-RS ones and the WSDL is generated and it should be able to handle your XJC generated objects with no problems.
http://metro.java.net/guide/ch02.html#create-a-metro-web-services-endpoint
In most tutorials that I have seen so far people are using wsconsume or something like that to create classes that clients can use to access an EJB 3 Web Service.
Is this the only possible option? As my EJB's interface is annotated with WebMethod, WebParam, etc. isn't it possible to create a dynamic proxy or use runtime bytecode enhancement to create the proxies, etc. on the fly? E.g.:
MyWebService webService = WebServiceEnhance.getWebService(MyWebService.class);
webService.webMethod("foo");
A link to good reference material is also highly appreciated.
One way is to deal with pure XML request/response. You can trap sample request/response for the web service you want to consume using either SoapUI or Fiddler and then use these samples as templates within your client.
I just want to implement a service in java that will:
take some arguments, then search the database
return the JSON object of the fetched data
I need help to identify the ways through which I can implement this thing.
e.g. Suppose I am getting the name of the book as argument I want to render.
On service part, I have to fetch book data and convert it to JSON and write/return to response.
I was looking at the Apache Axis2 but I am not sure that I am going in the right direction.
So, pls help.
Need guidelines not implementation.
Thanks
I would suggest using JAX-RS based services which would be ideal for your scenario as you want json data. These are pretty easy to get started with. Jersey is a widely used frameworks. Also see RESTEasy.
If you are returning the data in JSON then you probably don't need to implement a full web service, which uses XML for both the request and the response.
A normal dynamic web application (written as a Java Servlet) will be able to read request parameters in the HTTP payload and return a JSON-encoded HTTP response.
However you need to consider your clients; if they are only able to access web services then you need to forget about a JSON response and simply objectify the response. However if the clients can access web resources without issue then go with the servlet approach.
If you need to go with web services then look at the Metro 2 framework.
One way to do this is to keep it standards-based.
If you are using the JEE5/6 framework, your best bet would be to go with JAX-WS - comes built-in with the JSE too (if I remember correctly)
You really just have to annotate a POJO with #WebService to achieve this.
Regarding creating a JSON response, a good bet is to stick with the implementation from http://code.google.com/p/google-gson/ ; simple and straightforward
Axis2 can handle/support the webservice related part, iaw, transforming java objects into JSON and vice-versa and providing an easy-to-use API for the communication part.
Hibernate or JPA could be useful for database related tasks, although it might be easier to just use JDBC to send some simple SQL commands to the database (especially if the database already existst).
Im a little confused on the varying definitions and implementations of web services available as implementations. Need some clarification please.
Ones I have used till now:
If a vendor gives me a specific format of XML that I can send populated with data to request and I make a simple HTTP POST over the internet passing in the XML String as the payload, is this a web service call ? If so, is there a specific name to it, this kind of web service ? Because obviously, it does not use anything like Axis, WSDL or SOAP to establish this connection.
A variant of this is If the vendor gives me an XSD, I use JAXB to make a java class out of it and pass in the serialized version of the object, which eventually works out to be the same as option 1.
RESTful web service: Vendor gives me a URL like http://restfulservice/products and I can make HTTP Requests to the URL and depending on what HTTP verb I use, the appropropriate action is called and the response sent over the wire.
Ones I have only read about\ have a vague idea about
SOAP. How does this work?.. Ive read the W3Schools tutorial and I undertsand that there is a very specific form of XML that is standardized according to W3C standards that we use to pass the same kind of messages as we did in option 1. But how does this work in real life? Vendor sends me what? Do I generate classes? Do I serialize some objects and http post them over to an address? Or do the generated objects themselves have connection methods that will do them for me?
What about WSDL? When does a vendor send me WSDL and what do I do with it ? I guess I can generate classes from it. If yes, then what do I do with the generated classes ?
When do I need that axis jar to generate classes from something that the vendor sends ?
As you can see, I have some clear and other mostly vague ideas about the different kinds of web services available. would help if someone ould clarify and\or point to more real-world resources. I've looked a little bit into Java Web Services on the internet and the numerous four letter acronyms that get thrown at me make me dizzy.
Thanks
If a vendor gives me a specific format
of XML that I can send populated with
data to request and I make a simple
HTTP POST over the internet passing in
the XML String as the payload, is this
a web service call ? If so, is there a
specific name to it, this kind of web
service ?
This is still a web service, yes. It doesn't have an "official" name, I usually refer to it as XML-over-HTTP, mainly because I can't think of a better name.
SOAP. How does this work?.. Ive read
the W3Schools tutorial and I
undertsand that there is a very
specific form of XML that is
standardized according to W3C
standards that we use to pass the same
kind of messages as we did in option 1
SOAP provides a standard wrapper layer around the sort of messages you were sending in (1). This wrapper provides information such as an indication as to which operation you are invoking. It can also provide security services, transaction information, and so on. It's a pretty thin layer, usually.
What about WSDL? When does a vendor
send me WSDL and what do I do with it
? I guess I can generate classes from
it. If yes, then what do I do with the
generated classes ?
Again, WSDL is a pretty thin layer, this time around an XML Schema. It defines the operations that SOAP messages will invoke at runtime, as well as the Schema types of the requests and responses. Its a way of formalising the XML document exchange interface.
Say, for example, you had an XML Schema, and have a web service as you described
Using JAXB to generate java source from the schema
Send XML documents conforming to that schema over HTTP to the web service
With WSDL and SOAP, you would extend this a bit :
Write a thin WSDL wrapper around the XML Schema, formalising which operations are available.
Use a WSDL import tool to generate client/server stubs for that WSDL/Schema. In Java, this often incorporates JAXB.
Use a SOAP client/server to invoke the web service
As you can see, it's essentially the same process. The difference is that SOAP/WSDL provides additional information and context to the tools, allowing those tools to do more of the work for you. It's not hugely different, though.
If you get a WSDL document from somewhere, all you really need to know is that it defines a service interface. You run it through your favourite language's binding generator to make some code that you can use to call the service. Typically that means you'll be talking over the wire to the service using SOAP messages over HTTP. SOAP's just a wrapper round sending pretty arbitrary XML messages.
Axis is a library for doing this stuff in Java (both client and server side). I suspect that there are better implementations in other libraries.