It's time to ask question on StackOverflow because I did not find a good one in Google.
We have a legacy systems(2 in my case) that provide some functionality via RESTful web-services.
Now we are building a Java EE system that will consume RESTful services from that legacy systems.
Questiuon: how to build convenient facade API over mentioned RESTful web-services to use them easily in our Java EE app?
Are there some frameworks to easily consume a set of REST web-services and it can be XML-configured?
There is a number of options
The most "low level" - HTTP Client (http://hc.apache.org/httpclient-3.x/)
Something more abstract - RestEasy ClientRequest/ClientRespons (http://docs.jboss.org/resteasy/docs/1.2.GA/javadocs/org/jboss/resteasy/client/ClientRequest.html) there is a number of tutorials how to work with it
You might like it most due to XML config - Spring Framework RestTemplate support (see, for instance http://static.springsource.org/spring/docs/3.0.x/javadoc-api/org/springframework/web/client/RestTemplate.html), there is a number of tutorials in the web too.
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 have an api that I need to call that uses json-rpc-1.0 (I have no control of the implementation). I'd like to be able to manipulate jaxb objects and have them marshal into json-rpc-1.0 format. Is this something that jackson/jersey-json can accomplish or is there a different library that can achieve this goal?
No, Jersey cannot be configured to support JSON-RPC, but Jersey could be used to implement JSON-RPC. JSON-RPC specifies a protocol with requests and responses and can be implemented over HTTP. Jersey (and all JAX-RPC implementations) can be used to implement any HTTP based protocol.
However, since the latest JSON-RPC spec (2.0 - http://www.jsonrpc.org/specification) does not specify how request and responses are mapped to HTTP verbs (POST, GET, etc.) and status codes, there could be some incompatibilities between JSON-RPC implementations.
Instead of using Jersey to implement JSON-RPC, you might be better off using an existing JSON-RPC implementation, see also http://en.wikipedia.org/wiki/JSON-RPC#Implementations
I have a GWT application, with a Native Java backend, and a compiled Javascript front-end (as usual).
My GWT service should also be accessible from other clients, including a java applet. Initially my idea was to double the GWT service as a SOAP service, and use a soap client from the applet to access the GWT service, but I am wondering if it might be possible to use the built-in GWT client infrastructure to call the server from Java.
The problem with this approach is serializing the request and deserialize the response so as to be compatible with the GWT service.
One solution is to use GWT SyncProxy:
http://code.google.com/p/gwt-syncproxy/
which is explained here:
(dead) http://www.gdevelop.com/blog/2010/01/testing-gwt-rpc-services/
(Wayback Archive) http://wayback.archive.org/web/20130107141210/http://www.gdevelop.com/blog/2010/01/testing-gwt-rpc-services/
You can use it directly or, since they provide the source, you take a peek to see how they serialize the request and deserialize the response.
Another approach is to use Restlet to provide the services and then convert your GWT client to make REST calls. The Restlet people provide a GWT library to facilitate this.
http://wiki.restlet.org/docs_2.0/13-restlet/275-restlet/144-restlet.html
They provide an example of calling the REST service via Restlet from different clients, including GWT client, Java SE, and Android:
http://wiki.restlet.org/docs_2.0/13-restlet/21-restlet/318-restlet/303-restlet.html
Edit:
I only know RESTlet from evaluating it last year for my GWT project. I'm no expert and I didn't end up using it, but this is no reflection, good or bad, on RESTlet.
OP asks:
What would be the advantage of using the Restlet framework over JAX-RS ?
Essentially, JAX-RS is an just API (like JDBC) - you still need to pick an implementation or use the reference implementation Jersey. RESTLet has an extension for supporting JAX-RS API.
http://www.restlet.org/about/faq#07
7. What is the link between Restlet and JAX-RS (JSR-311)?
...
To summarize, both APIs have very different designs but are potentially complementary. The good news is that Jérôme Louvel (Restlet's creator) is an active member of the JSR-311 Expert Group and that an implementation of the JAX-RS API was made on top of the Restlet API. This "JAX-RS extension for Restlet" was developed by Stephan Koops in the context of his Master thesis and is one of the most advanced implementations available. For more documentation on this extension, please refer to this page.
OP asks:
Is it possible to use Tomcat / web.xml infrastructure instead of org.reslet.server
http://wiki.restlet.org/docs_2.0/13-restlet/275-restlet/312-restlet.html
This edition is aimed for development and deployment of Restlet applications inside Java EE application server, or more precisely inside Servlet containers such as Apache Tomcat.
This question already has answers here:
SOAP vs REST (differences)
(13 answers)
Closed 5 years ago.
For now I have a slight idea about the differences between SOAP and RESTful services.
My question is when I should use SOAP, and when I should use RESTful; which one is "better" when it comes to performance/speed or request handling?
I'm implementing it for the first time in RESTful (Java) and I want know more about it; I've dealt with SOAP before.
This is a follow-up question to this post.
REST is almost always going to be faster. The main advantage of SOAP is that it provides a mechanism for services to describe themselves to clients, and to advertise their existence.
REST is much more lightweight and can be implemented using almost any tool, leading to lower bandwidth and shorter learning curve. However, the clients have to know what to send and what to expect.
In general, When you're publishing an API to the outside world that is either complex or likely to change, SOAP will be more useful. Other than that, REST is usually the better option.
REST vs. SOAP Web Services
I am seeing a lot of new web services are implemented using a REST
style architecture these days rather than a SOAP one. Lets step back a
second and explain what REST is.
What is a REST web service?
The acronym REST stands for representational state transfer, and this
basically means that each unique URL is a representation of some
object. You can get the contents of that object using an HTTP GET, to
delete it, you then might use a POST, PUT, or DELETE to modify the
object (in practice most of the services use a POST for this).
Who's using REST?
All of Yahoo's web services use REST, including Flickr and Delicious.
APIs use it, pubsub, bloglines, Technorati, and both eBay, and Amazon
have web services for both REST and SOAP.
Who's using SOAP?
Google seams to be consistent in implementing their web services to
use SOAP, with the exception of Blogger, which uses XML-RPC. You will
find SOAP web services in lots of enterprise software as well.
REST vs. SOAP
As you may have noticed the companies I mentioned that are using REST
APIs haven't been around for very long, and their APIs came out this
year mostly. So REST is definitely the trendy way to create a web
service, if creating web services could ever be trendy (lets face it
you use soap to wash, and you rest when your tired). The main
advantages of REST web services are:
Lightweight - not a lot of extra XML markup Human Readable Results
Easy to build - no toolkits required. SOAP also has some advantages:
Easy to consume - sometimes Rigid - type checking, adheres to a
contract Development tools For consuming web services, its sometimes a
toss up between which is easier. For instance Google's AdWords web
service is really hard to consume (in ColdFusion anyway), it uses SOAP
headers, and a number of other things that make it kind of difficult.
On the converse, Amazon's REST web service can sometimes be tricky to
parse because it can be highly nested, and the result schema can vary
quite a bit based on what you search for.
Whichever architecture you choose make sure its easy for developers
to access it, and well documented.
Freitag, P. (2005). "REST vs SOAP Web Services". Retrieved from http://www.petefreitag.com/item/431.cfm on June 13, 2010
SOAP
Simple Object Access Protocol (SOAP) is a standard, an XML language, defining a message architecture and message formats. It is used by Web services. It contains a description of the operations.
WSDL is an XML-based language for describing Web services and how to access them. It will run on SMTP, HTTP, FTP, etc. It requires middleware support and well-defined mechanism to define services like WSDL+XSD and WS-Policy.
SOAP will return XML based data
REST
Representational State Transfer (RESTful) web services. They are second-generation Web services.
RESTful web services communicate via HTTP rather than SOAP-based services and do not require XML messages or WSDL service-API definitions. For REST middleware is not required, only HTTP support is needed. It is a WADL standard, REST can return XML, plain text, JSON, HTML, etc.
REST is an architecture.
REST will give human-readable results.
REST is stateless.
REST services are easily cacheable.
SOAP is a protocol. It can run on top of JMS, FTP, and HTTP.
REST has no WSDL (Web Description Language) interface definition.
REST is over HTTP, but SOAP can be over any transport protocols such as HTTP, FTP, SMTP, JMS, etc.
REST stands for representational state transfer whereas SOAP stands for Simple Object Access Protocol.
SOAP defines its own security where as REST inherits security from the underlying transport.
SOAP does not support error handling, but REST has built-in error handling.
REST is lightweight and does not require XML parsing. REST can be consumed by any client, even a web browser with Ajax and JavaScript. REST consumes less bandwidth, it does not require a SOAP header for every message.
REST is useful over any protocol which provide a URI. Ignore point 5 for REST as mentioned below in the picture.
REST vs. SOAP
SOAP:
► SOAP is simple object access protocol that run on TCP/UDP/SMTP.
► SOAP read and write request response messages in XML format.
► SOAP uses interface in order to define the services.
► SOAP is more secure as it has its own security and well defined standards.
► SOAP follows RPC and Document style to define web services.
► SOAP uses SOAP-UI as client tools for testing.
REST
► REST is representational state transfer that uses underlying HTTP protocols.
► REST is stateless.
► REST is an architectural style that is used to describe and define web services.
► REST can read and write request response messages in JSON/XML/Plain HTML.
► REST uses URI for each resource that is used in web service.A resource can be image text method etc.
► REST uses set of verbs, like HTTP's GET, POST, PUT, DELETE.
► REST is easy to develop and easy to manage as compared to SOAP UI.
► REST has light-weight client tools or plugins that can easily be integrated inside a browser.
► REST services are cacheable.
Difference between REST and SOAP:
SOAP Web services:
If your application needs a guaranteed level of reliability and security then SOAP offers additional standards to ensure this type of operation.
If both sides (service provider and service consumer) have to agree on the exchange format then SOAP gives the rigid specifications for this type of interaction.
RestWeb services:
Totally stateless operations: for stateless CRUD (Create, Read, Update, and Delete) operations.
Caching situations: If the information needs to be cached.
SOAP web service always make a POST operation whereas using REST you can choose specific HTTP methods like GET, POST, PUT, and DELETE.
Example: to get an item using SOAP you should create a request XML, but in the case of REST you can just specify the item id in the URL itself.
REST is easier to use for the most part and is more flexible. Unlike SOAP, REST doesn’t have to use XML to provide the response. We can find REST-based Web services that output the data in the Command Separated Value (CSV), JavaScript Object Notation (JSON) and Really Simple Syndication (RSS) formats.
We can obtain the output we need in a form that’s easy to parse within the language we need for our application.REST is more efficient (use smaller message formats), fast and closer to other Web technologies in design philosophy.