One of the biggest debates in Ajax development today is JSON versus
XML. This is at the heart of the data end of Ajax since you usually
receive JSON or XML from the server side (although these are not the
only methods of receiving data). Below I will be listing pros and cons
of both methods.
If you have been developing Ajax applications for any length of time
you will more than likely be familiar with XML data. You also know that
XML data is very powerful and that there are quite a few ways to deal
with the data. One way to deal with XML data is to simply apply a XSLT
style sheet to the data (I won't have time in this post to go over the
inconsistent browser support of XSLT, but it is something to look into
if you want to do this). This is useful if you just want to display the
data. However, if you want to do something programmatically with the
data (like in the instance of a web service) you will need to parse the
data nodes that are returned to the XMLHTTPRequest object (this is done
by going through the object tag by tag and getting the needed data). Of
course there are quite a few good pre-written libraries that can make
going through the XML data easier and I recommend using a good one (I
won't go into depth as to what libraries I prefer here, but perhaps in a
future post). One thing to note is that if you want to get XML data
from another domain you will have to use a server side proxy as the
browser will not allow this type of receiving data across domains.
JSON is designed to be a more programmatic way of dealing with data.
JSON (JavaScript Object Notation) is designed to return data as
JavaScript objects. In an Ajax application using JSON you would receive
text through the XMHTTPRequest object (or by directly getting the data
through the script tag which I will touch on later) and then pass that
text through an eval statement or use DOM manipulation to pass it into a
script tag (if you haven't already read my post on using JSON without
using eval click here
to read the post). The power of this is that you can use the data in
JavaScript without any parsing of the text. The down side would be if
you just wanted to display the data there is no easy way to do this with
JSON. JSON is great for web services that are coming from different
domains since if you load the data through a script tag then you can get
the data without a domain constraint.
The type of data that you use for your application will depend on
quite a few factors. If you are going to be using the data
programmatically then in most cases JSON is the better data method to
use. On the other hand if you just want to display the data returned I
would recommend XML. Of course there may be other factors such as if you
are using a web service, which could dictate the data method. If you
are getting data from a different domain and JSON is available this may
be the better choice. For Ruby on Rails developers, if you would prefer
to use JSON and XML is all that is available the 2.0 release allows you
to change XML into JSON. One of the biggest reasons that people use JSON
is the size of the data. In most cases JSON uses a lot less data to
send to your application (of course this may very depending on the data
and how the XML is formed).
I would recommend that you take a good look at the application that
you are building and decide based on the above which type of data you
should deal with. There may be more factors than the above including
corporate rules and developer experience, but the above should have
given you a good idea as to when to use either data method.
If you would like to contact me regarding any of the above you can make me your friend on Social Ajaxonomy and send a message to me through the service (Click here to go to my profile on Social Ajaxonomy).
By David Hurth
Source : http://www.ajaxonomy.com/2007/xslt/xml-versus-json-what-best-your-app
Monday, June 25, 2012
WSDL and WADL
Defining the Contract
An important part of any web service is the contract (or interface) which it defines between the service and any clients that might use it. This is important for a number of reasons: visualization with tools, interaction with other specifications (e.g., web service choreography), code generation, and enforcing a high-level agreement between the client and service provided (that still gives the service freedom to change the underlying implementation). Taken together, they give pretty compelling use cases for having web services contracts, although advocates of minimalism may disagree.
When IBM, Microsoft, and Ariba submitted WSDL 1.1 to the W3C in 2001 as a language for describing web services in conjunction with SOAP 1.1, HTTP POST and GET, and MIME, it quickly became a standard used by every SOAP toolkit. This happened in spite of the fact that it never progressed beyond being a W3C Note (which, according to W3C, is a document available for "discussion" and not officially endorsed by the W3C). In fact, though there is both a WSDL 1.1 and 1.2, WSDL 2.0 is the only version of the specification officially endorsed by the W3C.
With the rise in popularity of RESTful web services, there also became a need to describe contracts for these types of web services as well. Although WSDL 2.0 attempts to fill the gap by providing support for HTTP binding, another specification fills this need in an arguably better way: WADL, a specification developed at Sun by Marc Hadley. Though it has not been submitted to any official standards body (OASIS, W3C, etc.), WADL is promising because of its more comprehensive support for REST-style services.
Contract-First Development
In general there are two different approaches to development of web services in the real world: code-first or contract-first. Code-first is where existing code (generally methods/functions) is turned into a web service using tooling, e.g. the java2wsdl script in Apache Axis. Contract-first is where the actual web services contract is developed first (usually in WSDL), then this is then associated with the appropriate implementation--often using code generation with a tool such as the wsdl2java script in Apache Axis.
Though code-first is a highly popular approach, contract-first is generally considered to be best practice in order to shield the consumers of a service from changes in the underlying code base. By providing an XML-based contract, you are also protecting the client from the vagaries of how different Web Service toolkits generate contracts from code, differences in the way that language types are translated to XML types, etc. Though writing WSDL or WADL rather than code may involve some additional learning curve at the beginning, it pays off in the long run with more robustly designed services.
WSDL 1.1
An official W3C standard, the Web Services Description Language (WSDL) is an XML language for describing web services. WSDL 1.1 (which is still in wide use) has five major elements-
types, message, portType, binding, and service
-in that order (figure 1 below); all these major elements may be defined 0 or more times in a WSDL document, except for <types>, which may be 0 or 1 time. Here's a short description of each:
Figure 1: Major elements of WSDL 1.1. (1)
At first blush, having all these different parts of WSDL seems a bit overly complex--after all, do you really need to define both a part (message) for an operation as well as an operation separately (this was my first reaction...)? Well, WSDL 1.1 was created to be highly decoupled, and to maximize reuse of every possible piece; for example, one can define a message that can be used both as an input or an output, or can be used by multiple port type operations. The end result of this structure, however, was a bit unnecessary and hard to read, so the authors of the WSDL 2.0 improved this by removing the <message> section, and using defined elements instead.
WSDL 2.0
WSDL underwent a major renovation in version 2.0, changing the root tag to <description>, and ushering in many other changes and additions. I've already covered much of the structure in WSDL 1.1, so here I will describe mainly the differences:
Figure 2: Major elements of WSDL 2.0. (1)
WSDL Styles
This developerWorks articledoes a great job of explaining the different styles of WSDL, so I will only summarize briefly here.
In general, an RPC (or "remote procedure call") style service will define the references in its message parts as XML Schema types; a Document style service will define element references on its message parts (the soap:binding will use the appropriate style attribute). An Encoded style will encode the types of the children of the soap:body in the SOAP message; a literal style will not encode them, but leave them as literal XML elements (the binding of input and output messages will have the appropriate use attribute).
RPC vs. Document (where "ns:myElement" is a reference to a defined element) WSDL definitions
e, generally speaking, four distinct styles of
WSDL: RPC/Encoded, RPC/Literal, Document/Literal, and Document/Literal
Wrapped. As explained in Part 1,
RPC/Encoded, once ubiquitous, is now pretty much dead: unless you have
to interact with a legacy web service, use something else. Of the
remaining styles, RPC/Literal has the drawback that you cannot really
validate the types in the SOAP message. With Document/Literal, you can
validate the types but you lose the name of the operation in the SOAP.
This is where the Document/Literal Wrapped style comes in handy: it
"wraps" the body of the document payload in an element that represents
the operation name (it also has the additional benefit of enforcing only
one child of soap:body as mandated by WS-I). The only real drawback
of Document/Literal Wrapped is that you cannot "overload" web service
operation names, but this is a minor quibble. Generally speaking, using
this style of WSDL is your best bet, unless your SOAP toolkit is
unable to work with it.
Message Exchange Patterns
Message exchange patterns are the "handshake protocol" of web services. They let a client know what type (in/out) of messages or faults must be exchanged, and in what order.
WSDL 1.1 defined 4 basic message exchange patterns:
A WSDL document can be divided into "abstract" and "concrete" portions that by convention often are defined in two or more files (where the concrete file imports the abstract one). The abstract elements are <types>, <message>, and <portType> (or <interface> in 2.0); the concrete ones are <binding> and <service>. Separating these two sections allows for maximal reuse and flexibility in defining services.
A great illustration of this principle is with WS-RP (Web Services for Remote Portlets), a specification essentially for exchanging portlet content between different servers (e.g., a Java application server and, say, Microsoft Sharepoint). WS-RP defines in its specifications all of the types and operations that will be used in the web service of the "producer". The producer server only has to specify the actual concrete WSDL.
WADL
WADL, or Web Application Description Language, is a specification developed to be an alternative to WSDL with specific support for RESTful web services. Whether or not WADL will be widely adopted is still an open question-- certainly it would help if it were submitted to a standards body--but it is interesting nevertheless to present it in contrast with WSDL. Here, instead of providing a more comprehensive overview (the 11/09/2006 specification is very easy to read), I'll provide an example to give a flavor of how it works in the form of the ever-popular stock quote example (Figure 3 below). Notice how it defines both resources and representations, as well as the methods that can be used to manipulate the resources.
Figure 3: A WADL example.
WADL does a nice job of capturing the style of REST. As with any other technology, though, most will wait to use it until it sees some significant adoption.
Conclusion
This has certainly been a whirlwind tour of WSDL and WADL. We've covered some of the most important points here in a fairly concise fashion, but there is quite a lot which can be said about the subject. I encourage anyone who wants to dive deeper to look at the References below (You can find References at the bottom of the original version of the article on the web).
By Brennan Spies
Source : http://www.ajaxonomy.com/2008/xml/web-services-part-2-wsdl-and-wadl
An important part of any web service is the contract (or interface) which it defines between the service and any clients that might use it. This is important for a number of reasons: visualization with tools, interaction with other specifications (e.g., web service choreography), code generation, and enforcing a high-level agreement between the client and service provided (that still gives the service freedom to change the underlying implementation). Taken together, they give pretty compelling use cases for having web services contracts, although advocates of minimalism may disagree.
When IBM, Microsoft, and Ariba submitted WSDL 1.1 to the W3C in 2001 as a language for describing web services in conjunction with SOAP 1.1, HTTP POST and GET, and MIME, it quickly became a standard used by every SOAP toolkit. This happened in spite of the fact that it never progressed beyond being a W3C Note (which, according to W3C, is a document available for "discussion" and not officially endorsed by the W3C). In fact, though there is both a WSDL 1.1 and 1.2, WSDL 2.0 is the only version of the specification officially endorsed by the W3C.
With the rise in popularity of RESTful web services, there also became a need to describe contracts for these types of web services as well. Although WSDL 2.0 attempts to fill the gap by providing support for HTTP binding, another specification fills this need in an arguably better way: WADL, a specification developed at Sun by Marc Hadley. Though it has not been submitted to any official standards body (OASIS, W3C, etc.), WADL is promising because of its more comprehensive support for REST-style services.
Contract-First Development
In general there are two different approaches to development of web services in the real world: code-first or contract-first. Code-first is where existing code (generally methods/functions) is turned into a web service using tooling, e.g. the java2wsdl script in Apache Axis. Contract-first is where the actual web services contract is developed first (usually in WSDL), then this is then associated with the appropriate implementation--often using code generation with a tool such as the wsdl2java script in Apache Axis.
Though code-first is a highly popular approach, contract-first is generally considered to be best practice in order to shield the consumers of a service from changes in the underlying code base. By providing an XML-based contract, you are also protecting the client from the vagaries of how different Web Service toolkits generate contracts from code, differences in the way that language types are translated to XML types, etc. Though writing WSDL or WADL rather than code may involve some additional learning curve at the beginning, it pays off in the long run with more robustly designed services.
WSDL 1.1
An official W3C standard, the Web Services Description Language (WSDL) is an XML language for describing web services. WSDL 1.1 (which is still in wide use) has five major elements-
types, message, portType, binding, and service
-in that order (figure 1 below); all these major elements may be defined 0 or more times in a WSDL document, except for <types>, which may be 0 or 1 time. Here's a short description of each:
- <types>: This is where XML types to be used in the WSDL document are defined. Traditionally, this has meant using XML Schema, but newer versions of WSDL also support Relax NG.
- <message>: This is the section where the input or output parts of an operation are defined, i.e. the "parameters" or "return types". It may have multiple child <part> elements, though WS-I forbids the use of more than one part per message in a document literal style service. The <part> itself may have an element (referring to a qualified XML element) or a type (referring to an XML Schema type) attribute; the later is use in RPC/encoded style services, the former in RPC/literal or Document/literal style services (see WSDL Styles).
- <portType>: Here is where the operations that a web service offers are defined in terms of messages (input and output, with faults). Faults (referring to SOAP faults here) are the web service equivalent of the exception in languages like C++ or Java; most SOAP toolkits will translate SOAP faults into exceptions at runtime.
- <binding>: This is the "how" of a service, specifying the binding of the operations defined in the portType(s) to specific protocols, such as SOAP.
- <service>: This is the "where" of the service, specifying the address where a bound operation may be found.
<definitions>
<types>?
<!-- Defines the XML types used in the WSDL -->
</types>
<message>*
<part element="..." or type="..."/>*
</message>
<portType>*
<!-- Defines the web service "methods" -->
<operation>*
<input message="..."/>?
<output message="..."/>?
<fault message="..."/>*
</operation>
</portType>
<binding>*
<operation>
<!-- Binding of the operation to a protocol, e.g. SOAP -->
</operation>
</binding>
<service>*
<port name="..." binding="...">
<!-- Specifies the address of a service,
e.g., with soap:address -->
</port>
</service>
</definitions>
At first blush, having all these different parts of WSDL seems a bit overly complex--after all, do you really need to define both a part (message) for an operation as well as an operation separately (this was my first reaction...)? Well, WSDL 1.1 was created to be highly decoupled, and to maximize reuse of every possible piece; for example, one can define a message that can be used both as an input or an output, or can be used by multiple port type operations. The end result of this structure, however, was a bit unnecessary and hard to read, so the authors of the WSDL 2.0 improved this by removing the <message> section, and using defined elements instead.
WSDL 2.0
WSDL underwent a major renovation in version 2.0, changing the root tag to <description>, and ushering in many other changes and additions. I've already covered much of the structure in WSDL 1.1, so here I will describe mainly the differences:
- <interface>: As the name implies, this section tends to resemble interfaces in Java, which makes sense since they serve very similar purposes. Like interfaces, they can define multiple operation "signatures" and can be extended for reusability. The <interface> replaces the <portType> of WSDL 1.1, and adds explicit input faults and output faults. The child <operation> elements here can also explicitly define message-exchange patterns in their pattern attribute (see below).
- <binding>: This element has children that are identical to those of the interface, so that a binding can be specified for each. The major difference over version 1.1 is that bindings are re-usable. To be re-usable the binding simply omits the interface attribute; it may be specified later in the service declaration.
- <service>: Child <port> are replaced by similar <endpoint> elements.
<description>
<types>?
<!-- Defines the XML types used in the WSDL, as in 1.1 -->
</types>
<interface name="..." extends="...">*
<fault element="..."/>*
<operation pattern="..message pattern uri..">*
<input element="..."/>*
<output element="..."/>*
<infault ref="..some fault..."/>*
<outfault ref="..some fault"/>*
</operation>
</interface>
<binding interface="..."?>
<!-- The binding of a protocol to an interface, same structure
as the interface element -->
</binding>
<service interface="...">
<!-- Defines the actual addresses of the bindings, as in 1.1,
but now "ports" are called "endpoints" -->
<endpoint binding="..." address="..."/>*
</service>
</description>
WSDL Styles
This developerWorks articledoes a great job of explaining the different styles of WSDL, so I will only summarize briefly here.
In general, an RPC (or "remote procedure call") style service will define the references in its message parts as XML Schema types; a Document style service will define element references on its message parts (the soap:binding will use the appropriate style attribute). An Encoded style will encode the types of the children of the soap:body in the SOAP message; a literal style will not encode them, but leave them as literal XML elements (the binding of input and output messages will have the appropriate use attribute).
RPC vs. Document (where "ns:myElement" is a reference to a defined element) WSDL definitions
<!-- RPC request message --> <message name="input"> <part name="param" type="xsd:int"/> </message> <!-- Document request message --> <message name="input"> <part name="param" element="ns:myElement"/> </message> Encoded Vs. Literal SOAP Messages <!-- Encoded SOAP request --> <soap:body> <param xsi:type="xsd:int">1</param> <soap:body> <!-- Literal SOAP request --> <soap:body> <param>1<param> <soap:body>
Message Exchange Patterns
Message exchange patterns are the "handshake protocol" of web services. They let a client know what type (in/out) of messages or faults must be exchanged, and in what order.
WSDL 1.1 defined 4 basic message exchange patterns:
- One-way: An operation only receives an <input>.
- Request-response: An operation receives a request, then issues a response. Here the <input> child of <operation> is defined before the <output>
- Solicit-response: An operation sends a request, then waits for a response. Here the <output> would be defined before the <input>.
- Notification: An operation sends a message only.
- In-only: Here a service operation only receives an inbound message, but does not reply. This MEP cannot use a fault. When referred to by an operation's pattern attribute, it has the value "http://www.w3.org/ns/wsdl/in-only".
- Robust In-only: Identical to In-only, except that this type of MEP can trigger a fault. When referred to by an operation's pattern attribute, it has the value "http://www.w3.org/ns/wsdl/robust-in-only".
- In-Out: Identical to the request-response of WSDL 1.1. A fault here replaces the out message. When referred to by an operation's pattern attribute, it has the value "http://www.w3.org/ns/wsdl/in-out".
- In-Optional Out: Similar to In-Out, except that the out message is optional. When referred to by an operation's pattern attribute, it has the value "http://www.w3.org/ns/wsdl/in-opt-out".
- Out-Only: The service operation produces an out-only message, and cannot trigger a fault. When referred to by an operation's pattern attribute, it has the value "http://www.w3.org/ns/wsdl/out-only".
- Robust Out-Only: Similar to Out-Only, except that this type of MEP can trigger a fault. When referred to by an operation's pattern attribute, it has the value "http://www.w3.org/ns/wsdl/robust-out-only".
- Out-Optional In: The service produces an out message first, which may optionally be followed by an inbound response. When referred to by an operation's pattern attribute, it has the value "http://www.w3.org/ns/wsdl/out-opt-in".
A WSDL document can be divided into "abstract" and "concrete" portions that by convention often are defined in two or more files (where the concrete file imports the abstract one). The abstract elements are <types>, <message>, and <portType> (or <interface> in 2.0); the concrete ones are <binding> and <service>. Separating these two sections allows for maximal reuse and flexibility in defining services.
A great illustration of this principle is with WS-RP (Web Services for Remote Portlets), a specification essentially for exchanging portlet content between different servers (e.g., a Java application server and, say, Microsoft Sharepoint). WS-RP defines in its specifications all of the types and operations that will be used in the web service of the "producer". The producer server only has to specify the actual concrete WSDL.
WADL
WADL, or Web Application Description Language, is a specification developed to be an alternative to WSDL with specific support for RESTful web services. Whether or not WADL will be widely adopted is still an open question-- certainly it would help if it were submitted to a standards body--but it is interesting nevertheless to present it in contrast with WSDL. Here, instead of providing a more comprehensive overview (the 11/09/2006 specification is very easy to read), I'll provide an example to give a flavor of how it works in the form of the ever-popular stock quote example (Figure 3 below). Notice how it defines both resources and representations, as well as the methods that can be used to manipulate the resources.
<application xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://research.sun.com/wadl/2006/10 wadl.xsd" xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:ex="http://www.example.org/types" xmlns="http://research.sun.com/wadl/2006/10"> <grammars> <include href="ticker.xsd"/> </grammars> <resources base="http://www.example.org/services/"> <resource path="getStockQuote"> <method name="GET"> <request> <param name="symbol" style="query" type="xsd:string"/> </request> <response> <representation mediaType="application/xml" element="ex:quoteResponse"/> <fault status="400" mediaType="application/xml" element="ex:error"/> </response> </method> </resource> </resources> </application>
WADL does a nice job of capturing the style of REST. As with any other technology, though, most will wait to use it until it sees some significant adoption.
Conclusion
This has certainly been a whirlwind tour of WSDL and WADL. We've covered some of the most important points here in a fairly concise fashion, but there is quite a lot which can be said about the subject. I encourage anyone who wants to dive deeper to look at the References below (You can find References at the bottom of the original version of the article on the web).
By Brennan Spies
Source : http://www.ajaxonomy.com/2008/xml/web-services-part-2-wsdl-and-wadl
SOAP vs. REST
Developers new to web services are often intimidated by parade of
technologies and concepts required to understand it: REST, SOAP, WSDL,
XML Schema, Relax NG, UDDI, MTOM, XOP, WS-I, WS-Security,
WS-Addressing, WS-Policy, and a host of other WS-* specifications that
seem to multiply like rabbits. Add to that the Java specifications,
such as JAX-WS, JAX-RPC, SAAJ, etc. and the conceptual weight begins
to become heavy indeed. In this series of articles I hope to shed some
light on the dark corners of web services and help navigate the sea
of alphabet soup (1).
Along the way I'll also cover some tools for developing web services,
and create a simple Web Service as an example. In this article I will
give a high-level overview of both SOAP and REST.
Introduction
There are currently two schools of thought in developing web services: the traditional, standards-based approach (SOAP) and conceptually simpler and the trendier new kid on the block (REST). The decision between the two will be your first choice in designing a web service, so it is important to understand the pros and cons of the two. It is also important, in the sometimes heated debate between the two philosophies, to separate reality from rhetoric.
SOAP
In the beginning there was...SOAP. Developed at Microsoft in 1998, the inappropriately-named "Simple Object Access Protocol" was designed to be a platform and language-neutral alternative to previous middleware techologies like CORBA and DCOM. Its first public appearance was an Internet public draft (submitted to the IETF) in 1999; shortly thereafter, in December of 1999, SOAP 1.0 was released. In May of 2000 the 1.1 version was submitted to the W3C where it formed the heart of the emerging Web Services technologies. The current version is 1.2, finalized in 2005. The examples given in this article will all be SOAP 1.2.
Together with WSDL and XML Schema, SOAP has become the standard for exchanging XML-based messages. SOAP was also designed from the ground up to be extensible, so that other standards could be integrated into it and there have been many, often collectively referred to as WS-*: WS-Addressing, WS-Policy, WS-Security, WS-Federation, WS-ReliableMessaging, WS-Coordination, WS-AtomicTransaction, WS-RemotePortlets, and the list goes on. Hence much of the perceived complexity of SOAP, as in Java, comes from the multitude of standards which have evolved around it. This should not be reason to be too concerned: as with other things, you only have to use what you actually need.The basic structure of SOAP is like any other message format (including HTML itself): header and body. In SOAP 1.2 this would look something like :
Note that the <Header> element is optional here, but the <Body> is mandatory.
The SOAP <Header>
SOAP uses special attributes in the standard "soap-envelope" namespace to handle the extensibility elements that can be defined in the header. The most important of these is the mustUnderstand attribute. By default, any element in the header can be safely ignored by the SOAP message recipient unless the the mustUnderstand attribute on the element is set to "true" (or "1", which is the only value recognized in SOAP 1.1). A good example of this would be a security token element that authenticates the sender/requestor of the message. If for some reason the recipient is not able to process these elements, a fault should be delivered back to the sender with a fault code of MustUnderstand.
Because SOAP is designed to be used in a network environment with multiple intermediaries (SOAP "nodes" as identified by the <Node> element), it also defines the special XML attributes role to manage which intermediary should process a given header element and relay, which is used to indicate that this element should be passed to the next node if not processed in the current one.
The SOAP <Body>
The SOAP body contains the "payload" of the message, which is defined by the WSDL's <Message> part. If there is an error that needs to be transmitted back to the sender, a single <Fault> element is used as a child of the <Body>.
The SOAP <Fault>The <Fault> is the standard element for error handling. When present, it is the only child element of the SOAP<Body>. The structure of a fault looks like :
Here, only the <Code> and <Reason>
child elements are required, and the <Subcode> child of
<Code> is also optional. The body of the Code/Value element is a
fixed enumeration with the values:
SOAP Encoding
Section 5 of the SOAP 1.1 specification describes SOAP encoding, which was originally developed as a convenience for serializing and de-serializing data types to and from other sources, such as databases and programming languages. Problems, however, soon arose with complications in reconciling SOAP encoding and XML Schema, as well as with performance. The WS-I organization finally put the nail in the coffin of SOAP encoding in 2004 when it released the first version of the WS-I Basic Profile, declaring that only literal XML messages should be used (R2706). With the wide acceptance of WS-I, some of the more recent web service toolkits do not provide any support for (the previously ubiquitous) SOAP encoding at all.
A Simple SOAP Example
Putting it all together, below is an example of a simple request-response in SOAP for a stock quote. Here the transport binding is HTTP.
If you play your cards right, you may never have to actually see a
SOAP message in action; every SOAP engine out there will do its best
to hide it from you unless you really want to see it. If something
goes wrong in your web service, however, it may be useful to know what
one looks like for debugging purposes.
REST
Much in the way that Ruby on Rails was a reaction to more complex web application architectures, the emergence of the RESTful style of web services was a reaction to the more heavy-weight SOAP-based standards. In RESTful web services, the emphasis is on simple point-to-point communication over HTTP using plain old XML (POX).
The origin of the term "REST" comes from the famous thesis from Roy Fielding describing the concept of Representative State Transfer (REST). REST is an architectural style that can be summed up as four verbs (GET, POST, PUT, and DELETE from HTTP 1.1) and the nouns, which are the resources available on the network (referenced in the URI). The verbs have the following operational equivalents:HTTP CRUD Equivalent
==============================
GET read
POST create,update,delete
PUT create,update
DELETE delete
A service to get the details of a user called 'dsmith', for example, would be handled using an HTTP GET to http://example.org/users/dsmith. Deleting the user would use an HTTP DELETE, and creating a new one would mostly likely be done with a POST. The need to reference other resources would be handled using hyperlinks (the XML equivalent of HTTP's href, which is XLinks' xlink:href) and separate HTTP request-responses.
A Simple RESTful Service
Re-writing the stock quote service above as a RESTful web service provides a nice illustration of the differences between SOAP and REST web services.
Though slightly modified (to include the ticker symbol in the
response), the RESTful version is still simpler and more concise than
the RPC-style SOAP version. In a sense, as well, RESTful web services
are much closer in design and philosophy to the Web itself.
Defining the Contract
Traditionally, the big drawback of REST vis-a-vis SOAP was the lack of any way of specifying a description/contract for the web service. This, however, has changed since WSDL 2.0 defines a full compliment of non-SOAP bindings (all the HTTP methods, not just GET and POST) and the emergence of WADL as an alternative to WSDL. This will be discussed in more detail in coming articles.
Summary and Pros/Cons
SOAP and RESTful web services have a very different philosophy from each other. SOAP is really a protocol for XML-based distributed computing, whereas REST adheres much more closely to a bare metal, web-based design. SOAP by itself is not that complex; it can get complex, however, when it is used with its numerous extensions (guilt by association).
To summarize their strengths and weaknesses:
** SOAP **
Pros:
Pros:
Source : http://www.ajaxonomy.com/2008/xml/web-services-part-1-soap-vs-rest
Introduction
There are currently two schools of thought in developing web services: the traditional, standards-based approach (SOAP) and conceptually simpler and the trendier new kid on the block (REST). The decision between the two will be your first choice in designing a web service, so it is important to understand the pros and cons of the two. It is also important, in the sometimes heated debate between the two philosophies, to separate reality from rhetoric.
SOAP
In the beginning there was...SOAP. Developed at Microsoft in 1998, the inappropriately-named "Simple Object Access Protocol" was designed to be a platform and language-neutral alternative to previous middleware techologies like CORBA and DCOM. Its first public appearance was an Internet public draft (submitted to the IETF) in 1999; shortly thereafter, in December of 1999, SOAP 1.0 was released. In May of 2000 the 1.1 version was submitted to the W3C where it formed the heart of the emerging Web Services technologies. The current version is 1.2, finalized in 2005. The examples given in this article will all be SOAP 1.2.
Together with WSDL and XML Schema, SOAP has become the standard for exchanging XML-based messages. SOAP was also designed from the ground up to be extensible, so that other standards could be integrated into it and there have been many, often collectively referred to as WS-*: WS-Addressing, WS-Policy, WS-Security, WS-Federation, WS-ReliableMessaging, WS-Coordination, WS-AtomicTransaction, WS-RemotePortlets, and the list goes on. Hence much of the perceived complexity of SOAP, as in Java, comes from the multitude of standards which have evolved around it. This should not be reason to be too concerned: as with other things, you only have to use what you actually need.The basic structure of SOAP is like any other message format (including HTML itself): header and body. In SOAP 1.2 this would look something like :
<env:Envelope xmlns:env="http://www.w3.org/2003/05/soap-envelope"> <env:Header> <!- Header information here -> </env:Header> <env:Body> <!- Body or "Payload" here, a Fault if error happened -> </env:Body> </env:Envelope>
The SOAP <Header>
SOAP uses special attributes in the standard "soap-envelope" namespace to handle the extensibility elements that can be defined in the header. The most important of these is the mustUnderstand attribute. By default, any element in the header can be safely ignored by the SOAP message recipient unless the the mustUnderstand attribute on the element is set to "true" (or "1", which is the only value recognized in SOAP 1.1). A good example of this would be a security token element that authenticates the sender/requestor of the message. If for some reason the recipient is not able to process these elements, a fault should be delivered back to the sender with a fault code of MustUnderstand.
Because SOAP is designed to be used in a network environment with multiple intermediaries (SOAP "nodes" as identified by the <Node> element), it also defines the special XML attributes role to manage which intermediary should process a given header element and relay, which is used to indicate that this element should be passed to the next node if not processed in the current one.
The SOAP <Body>
The SOAP body contains the "payload" of the message, which is defined by the WSDL's <Message> part. If there is an error that needs to be transmitted back to the sender, a single <Fault> element is used as a child of the <Body>.
The SOAP <Fault>The <Fault> is the standard element for error handling. When present, it is the only child element of the SOAP<Body>. The structure of a fault looks like :
<env:Fault xmlns:m="http://www.example.org/timeouts"> <env:Code> <env:Value>env:Sender</env:Value> <env:Subcode> <env:Value>m:MessageTimeout</env:Value> </env:Subcode> </env:Code> <env:Reason> <env:Text xml:lang="en">Sender Timeout</env:Text> </env:Reason> <env:Detail> <m:MaxTime>P5M</m:MaxTime> </env:Detail> </env:Fault>
- VersionMismatch: this indicates that the node that "threw" the fault found an invalid element in the SOAP envelope, either an incorrect namespace, incorrect local name, or both.
- MustUnderstand: as discussed above, this code indicates that a header element with the attribute mustUnderstand="true" could not be processed by the node throwing the fault. A NotUnderstood header block should be provided to detail all of the elements in the original message which were not understood.
- DataEncodingUnknown: the data encoding specified in the envelope's encodingSytle attribute is not supported by the node throwing the fault.
- Sender: This is a "catch-all" code indicating that the message sent was not correctly formed or did not have the appropriate information to succeed.
- Receiver: Another "catch-all" code indicating that the message could not be processed for reasons attributable to the processing of the message rather than to the contents of the message itself.
SOAP Encoding
Section 5 of the SOAP 1.1 specification describes SOAP encoding, which was originally developed as a convenience for serializing and de-serializing data types to and from other sources, such as databases and programming languages. Problems, however, soon arose with complications in reconciling SOAP encoding and XML Schema, as well as with performance. The WS-I organization finally put the nail in the coffin of SOAP encoding in 2004 when it released the first version of the WS-I Basic Profile, declaring that only literal XML messages should be used (R2706). With the wide acceptance of WS-I, some of the more recent web service toolkits do not provide any support for (the previously ubiquitous) SOAP encoding at all.
A Simple SOAP Example
Putting it all together, below is an example of a simple request-response in SOAP for a stock quote. Here the transport binding is HTTP.
The request:GET /StockPrice HTTP/1.1 Host: example.org Content-Type: application/soap+xml; charset=utf-8 Content-Length: nnn <?xml version="1.0"?> <env:Envelope xmlns:env="http://www.w3.org/2003/05/soap-envelope" xmlns:s="http://www.example.org/stock-service"> <env:Body> <s:GetStockQuote> <s:TickerSymbol>IBM</s:TickerSymbol> </s:GetStockQuote> </env:Body> </env:Envelope> The response:HTTP/1.1 200 OK Content-Type: application/soap+xml; charset=utf-8 Content-Length: nnn <?xml version="1.0"?> <env:Envelope xmlns:env="http://www.w3.org/2003/05/soap-envelope" xmlns:s="http://www.example.org/stock-service"> <env:Body> <s:GetStockQuoteResponse> <s:StockPrice>45.25</s:StockPrice> </s:GetStockQuoteResponse> </env:Body> </env:Envelope>
REST
Much in the way that Ruby on Rails was a reaction to more complex web application architectures, the emergence of the RESTful style of web services was a reaction to the more heavy-weight SOAP-based standards. In RESTful web services, the emphasis is on simple point-to-point communication over HTTP using plain old XML (POX).
The origin of the term "REST" comes from the famous thesis from Roy Fielding describing the concept of Representative State Transfer (REST). REST is an architectural style that can be summed up as four verbs (GET, POST, PUT, and DELETE from HTTP 1.1) and the nouns, which are the resources available on the network (referenced in the URI). The verbs have the following operational equivalents:HTTP CRUD Equivalent
==============================
GET read
POST create,update,delete
PUT create,update
DELETE delete
A service to get the details of a user called 'dsmith', for example, would be handled using an HTTP GET to http://example.org/users/dsmith. Deleting the user would use an HTTP DELETE, and creating a new one would mostly likely be done with a POST. The need to reference other resources would be handled using hyperlinks (the XML equivalent of HTTP's href, which is XLinks' xlink:href) and separate HTTP request-responses.
A Simple RESTful Service
Re-writing the stock quote service above as a RESTful web service provides a nice illustration of the differences between SOAP and REST web services.
The request:GET /StockPrice/IBM HTTP/1.1 Host: example.org Accept: text/xml Accept-Charset: utf-8 The response:HTTP/1.1 200 OK Content-Type: text/xml; charset=utf-8 Content-Length: nnn <?xml version="1.0"?> <s:Quote xmlns:s="http://example.org/stock-service"> <s:TickerSymbol>IBM</s:TickerSymbol> <s:StockPrice>45.25</s:StockPrice> </s:Quote>
Defining the Contract
Traditionally, the big drawback of REST vis-a-vis SOAP was the lack of any way of specifying a description/contract for the web service. This, however, has changed since WSDL 2.0 defines a full compliment of non-SOAP bindings (all the HTTP methods, not just GET and POST) and the emergence of WADL as an alternative to WSDL. This will be discussed in more detail in coming articles.
Summary and Pros/Cons
SOAP and RESTful web services have a very different philosophy from each other. SOAP is really a protocol for XML-based distributed computing, whereas REST adheres much more closely to a bare metal, web-based design. SOAP by itself is not that complex; it can get complex, however, when it is used with its numerous extensions (guilt by association).
To summarize their strengths and weaknesses:
** SOAP **
Pros:
- Langauge, platform, and transport agnostic
- Designed to handle distributed computing environments
- Is the prevailing standard for web services, and hence has better support from other standards (WSDL, WS-*) and tooling from vendors
- Built-in error handling (faults)
- Extensibility
- Conceptually more difficult, more "heavy-weight" than REST
- More verbose
- Harder to develop, requires tools
Pros:
- Language and platform agnostic
- Much simpler to develop than SOAP
- Small learning curve, less reliance on tools
- Concise, no need for additional messaging layer
- Closer in design and philosophy to the Web
- Assumes a point-to-point communication model--not usable for distributed computing environment where message may go through one or more intermediaries
- Lack of standards support for security, policy, reliable messaging, etc., so services that have more sophisticated requirements are harder to develop ("roll your own")
- Tied to the HTTP transport model
Source : http://www.ajaxonomy.com/2008/xml/web-services-part-1-soap-vs-rest
Monday, June 11, 2012
jquery datepicker localization persian , fa
<script type="text/javascript">
jQuery(function ($) {
$.datepicker.regional['fa'] = {
closeText:'بستن',
prevText:'<قبلي',
nextText:'بعدي>',
currentText:'امروز',
monthNames:['فروردين', 'ارديبهشت', 'خرداد', 'تير', 'مرداد', 'شهريور', 'مهر', 'آبان', 'آذر', 'دي', 'بهمن', 'اسفند'],
monthNamesShort:['فروردين', 'ارديبهشت', 'خرداد', 'تير', 'مرداد', 'شهريور', 'مهر', 'آبان', 'آذر', 'دي', 'بهمن', 'اسفند'],
dayNames:['يکشنبه', 'دوشنبه', 'سهشنبه', 'چهارشنبه', 'پنجشنبه', 'جمعه', 'شنبه'],
dayNamesShort:['يك', 'دو', 'سه', 'چه', 'پن', 'جم', 'شن'],
dayNamesMin: ['ي', 'د', 'س', 'چ ', 'پ', 'ج ', 'ش'],
weekHeader:'هف',
dateFormat:'yy/mm/dd',
firstDay:6,
isRTL:true,
showMonthAfterYear:false,
yearSuffix:'',
timeOnlyTitle: 'افقط زمان' ,
timeText: 'زمان',
hourText: 'ساعت',
minuteText: 'دقيقه',
secondText: 'ثانيه',
ampm: false,
month: 'ماه',
week: 'هفته',
day: 'روز',
allDayText: 'همه روزها'
};
$.datepicker.setDefaults($.datepicker.regional['fa']);
});
</script>
jQuery(function ($) {
$.datepicker.regional['fa'] = {
closeText:'بستن',
prevText:'<قبلي',
nextText:'بعدي>',
currentText:'امروز',
monthNames:['فروردين', 'ارديبهشت', 'خرداد', 'تير', 'مرداد', 'شهريور', 'مهر', 'آبان', 'آذر', 'دي', 'بهمن', 'اسفند'],
monthNamesShort:['فروردين', 'ارديبهشت', 'خرداد', 'تير', 'مرداد', 'شهريور', 'مهر', 'آبان', 'آذر', 'دي', 'بهمن', 'اسفند'],
dayNames:['يکشنبه', 'دوشنبه', 'سهشنبه', 'چهارشنبه', 'پنجشنبه', 'جمعه', 'شنبه'],
dayNamesShort:['يك', 'دو', 'سه', 'چه', 'پن', 'جم', 'شن'],
dayNamesMin: ['ي', 'د', 'س', 'چ ', 'پ', 'ج ', 'ش'],
weekHeader:'هف',
dateFormat:'yy/mm/dd',
firstDay:6,
isRTL:true,
showMonthAfterYear:false,
yearSuffix:'',
timeOnlyTitle: 'افقط زمان' ,
timeText: 'زمان',
hourText: 'ساعت',
minuteText: 'دقيقه',
secondText: 'ثانيه',
ampm: false,
month: 'ماه',
week: 'هفته',
day: 'روز',
allDayText: 'همه روزها'
};
$.datepicker.setDefaults($.datepicker.regional['fa']);
});
</script>
Primefaces calendar localization persian , fa
<script type="text/javascript">
PrimeFaces.locales ['fa'] = {
closeText:'بستن',
prevText:'<قبلي',
nextText:'بعدي>',
currentText:'امروز',
monthNames:['فروردين', 'ارديبهشت', 'خرداد', 'تير', 'مرداد', 'شهريور', 'مهر', 'آبان', 'آذر', 'دي', 'بهمن', 'اسفند'],
monthNamesShort:['فروردين', 'ارديبهشت', 'خرداد', 'تير', 'مرداد', 'شهريور', 'مهر', 'آبان', 'آذر', 'دي', 'بهمن', 'اسفند'],
dayNames:['يکشنبه', 'دوشنبه', 'سهشنبه', 'چهارشنبه', 'پنجشنبه', 'جمعه', 'شنبه'],
dayNamesShort:['يك', 'دو', 'سه', 'چه', 'پن', 'جم', 'شن'],
dayNamesMin: ['ي', 'د', 'س', 'چ ', 'پ', 'ج ', 'ش'],
weekHeader:'هف',
dateFormat:'yy/mm/dd',
firstDay:6,
isRTL:true,
showMonthAfterYear:false,
yearSuffix:'',
timeOnlyTitle: 'افقط زمان' ,
timeText: 'زمان',
hourText: 'ساعت',
minuteText: 'دقيقه',
secondText: 'ثانيه',
ampm: false,
month: 'ماه',
week: 'هفته',
day: 'روز',
allDayText: 'همه روزها'
};
</script>
PrimeFaces.locales ['fa'] = {
closeText:'بستن',
prevText:'<قبلي',
nextText:'بعدي>',
currentText:'امروز',
monthNames:['فروردين', 'ارديبهشت', 'خرداد', 'تير', 'مرداد', 'شهريور', 'مهر', 'آبان', 'آذر', 'دي', 'بهمن', 'اسفند'],
monthNamesShort:['فروردين', 'ارديبهشت', 'خرداد', 'تير', 'مرداد', 'شهريور', 'مهر', 'آبان', 'آذر', 'دي', 'بهمن', 'اسفند'],
dayNames:['يکشنبه', 'دوشنبه', 'سهشنبه', 'چهارشنبه', 'پنجشنبه', 'جمعه', 'شنبه'],
dayNamesShort:['يك', 'دو', 'سه', 'چه', 'پن', 'جم', 'شن'],
dayNamesMin: ['ي', 'د', 'س', 'چ ', 'پ', 'ج ', 'ش'],
weekHeader:'هف',
dateFormat:'yy/mm/dd',
firstDay:6,
isRTL:true,
showMonthAfterYear:false,
yearSuffix:'',
timeOnlyTitle: 'افقط زمان' ,
timeText: 'زمان',
hourText: 'ساعت',
minuteText: 'دقيقه',
secondText: 'ثانيه',
ampm: false,
month: 'ماه',
week: 'هفته',
day: 'روز',
allDayText: 'همه روزها'
};
</script>
Saturday, June 9, 2012
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