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THE DIFFERENCE BETWEEN RPC AND DOCUMENT STYLE WSD

srisri's — Wed, 23 Mar 2011 08:40:49 +0000

THE DIFFERENCE BETWEEN RPC AND DOCUMENT STYLE WSDL

Summary

RPC style and document style are catchphrases frequently heard in the context of web services and the SOAP protocol. What exactly do they mean? How do they relate to the pair of terms "encoded/literal"? Where does the confusion about these terms come from? This article describes the WSDL binding style and use attributes.

By Susanne Rothaug

20 Nov 2004

Binding Style and Use

A web service is usually described by a WSDL (Web Services Description Language) document. In this document, the supported web service operations and messages are described abstractly and then bound to a concrete network protocol and message format. A typical WSDL document consists of the following elements: "types," "message," and "portType" for the abstract definitions; "binding" and "service" for the concrete specification. All of these elements are wrapped inside a "definitions" element.

In the context of RPC and document style, it is the binding element that we need to take a closer look at. A WSDL binding describes how the service is bound to a messaging protocol, either HTTP GET/POST, MIME, or SOAP. In practice, SOAP is the most universally used protocol; it is SOAP that the RPC/document distinction refers to. Usually HTTP(S) is used as transport protocol for the SOAP message – "SOAP over HTTP(S)."

The element of the WSDL contains a pair of parameters that influence the form of the resulting SOAP messages: binding style (RPC or document) and use (encoded or literal). See how style and use are defined in the WSDL fragment below:

 http://schemas.xmlsoap.org/soap/http" style="document" />

The "Style" Attribute

WSDL 1.1 specifies the style of the binding as either RPC or document. This choice corresponds to how the SOAP payload – i.e., how the contents of the element – can be structured. Here are some details of how each style affects the contents of :

Document: the content of is specified by XML Schema defined in the section. It does not need to follow specific SOAP conventions. In short, the SOAP message is sent as one "document" in the element without additional formatting rules having to be considered. Document style is the default choice.
RPC: The structure of an RPC style element needs to comply with the rules specified in detail in Section 7 of the SOAP 1.1 specification. According to these rules, may contain only one element that is named after the operation, and all parameters must be represented as sub-elements of this wrapper element.

As a consequence of the freedom of choice that the document style offers, the SOAP messages conforming to a document style WSDL may look exactly the same as the RPC equivalent.

The decisive question now is: What are the consequences of choosing one option or another? Why choose RPC over document, or document over RPC? In many cases, the SOAP messages generated from either RPC or document style WSDLs look exactly the same – so why offer the choice at all? The reason may be found in the history of the SOAP standard.

SOAP has its roots in synchronous remote procedure calls over HTTP and the appearance of the document accordingly followed these conventions. Later, it was seen as a simplification to use arbitrary XML in the SOAP body without adhering to conventions. This preference is reflected in the document style WSDL documents. So far, both options are represented in the WSDL specification and the choice of one or the other is mainly a question of personal taste since most SOAP clients today accept both versions.

The "Use" Attribute

The use attribute specifies the encoding rules of the SOAP message. This is also done within the element, as seen in the example above. The value can be encoded or literal. It refers to the serialization rules followed by the SOAP client and the SOAP server to interpret the contents of the element in the SOAP payload.

use="literal" means that the type definitions literally follow an XML schema definition.
use="encoded" refers to the representation of application data in XML, usually according to the SOAP encoding rules of the SOAP 1.1 specification. The rules to encode and interpret a SOAP body are in a URL specified by the encodingStyle attribute. Encoded is the appropriate choice where non-treelike structures are concerned, because all others can be perfectly described in XML Schema.

The combination of the style and use attributes leads to four possible style/use pairs:

RPC/encoded
RPC/literal
document/encoded
document/literal

Some of these combinations are rarely used in practice, such as document/encoded. In general, the literal use is gaining importance, and as far as RPC/encoded is concerned, the Web Services Interoperability Organization (WS-I) in its Basic Profile Version 1.0a of August 2003 ruled out the use of SOAP encoding with web services. Document/literal and RPC/literal will be the only allowed style/use combinations in the future.

SOA

srisri's — Tue, 22 Mar 2011 13:00:16 +0000

Loved this statement I heard somewhere ” Innovation is defined as making change in order to make something new,” SOA makes change easier”.

Push-based vs. Pull-based

srisri's — Mon, 07 Mar 2011 16:04:11 +0000

Push-based vs. Pull-based (courtesy wikipedia)

Most MVC frameworks follow a push-based architecture. These frameworks use actions that do the required processing, and then “push” the data to the view layer to render the results.^[4] Struts, Django, Ruby on Rails and Spring MVC are good examples of this architecture. An alternative to this is pull-based architecture (actually a pull-MVC as the Struts2 tag libs pull data from the actions via the actions getters), sometimes also called “component-based”. These frameworks start with the view layer, which can then “pull” results from multiple controllers as needed. In this architecture, multiple controllers can be involved with a single view. Struts2, Lift, Tapestry, JBoss Seam, Wicket and Stripes are examples of pull-based architectures.

Struts Filter vs Interceptors

srisri's — Mon, 07 Mar 2011 15:49:29 +0000

Filter:

Pattern: Intercepting Filter Pattern

Filters are java components- very similar to servlets- that you can use to intercept and process requests before they are sent to the servlet, or to process responses after the servlet has completed, but before the response goes back to the client. The container decides when to invoke the filters based on declarations in the Deployment Descriptor(web.xml). In the deployment descriptor , the developer maps which filters will be called for which request URL patterns. So its the deployer, not the programmer who decides which subset of requests or responses should be processed by which filters.

Request Filters can:

perform security checks
reformat request headers or bodies
audit or log requests

Response Filters can:

Compress the response stream
append or alter the response stream
create a different response altogether

Examples that have been identified for this design are

Authentication Filters
Logging and Auditing Filters
Image conversion Filters
Data compression Filters
Encryption Filters
Tokenizing Filters
Filters that trigger resource access events
XSL/T filters
Mime-type chain Filter

Interceptor:

Pattern: Interceptor Pattern

An interceptor is a stateless class that follows the interceptor pattern, as found in Filter and in AOP languages.

Interceptors are objects that dynamically intercept Action invocations. They provide the developer with the opportunity to define code that can be executed before and/or after the execution of an action. They also have the ability to prevent an action from executing. Interceptors provide developers a way to encapulate common functionality in a re-usable form that can be applied to one or more Actions.

Interceptors must be stateless and not assume that a new instance will be created for each request or Action. Interceptors may choose to either short-circuit the ActionInvocation execution and return a return code (such as Action.SUCCESS), or it may choose to do some processing before and/or after delegating the rest of the procesing using ActionInvocation.invoke().

E.g. Interceptors

Cookie Interceptor
Checkbox Interceptor
FileUpload Interceptor

More

Are Interceptors and Filters different ? , If yes then how ?

Apart from the fact that both Interceptors and filters are based on intercepting filter,there are few differences when it comes to Struts2.
Filters: (1)Based on Servlet Specification (2)Executes on the pattern matches on the request.(3) Not configurable method calls
Interceptors: (1)Based on Struts2. (2)Executes for all the request qualifies for a front controller( A Servlet filter ).And can be configured to execute additional interceptor for a particular action execution.(3)Methods in the Interceptors can be configured whether to execute or not by means of excludemethods or includeMethods.

A very nice explanation of N+1 Selects problem

srisri's — Fri, 04 Mar 2011 09:57:30 +0000

http://www.pramatr.com/2009/02/05/sql-n-1-selects-explained/

Eclipse: Failed to create Java Virtual Machine

srisri's — Mon, 21 Feb 2011 05:12:32 +0000

My main issue was, I wanted to use jdk1.5 with same version of JRE. But even after setting classpath I could only see jre1.6, thats because the jre version was registered with regedit. So to change it to 1.5 I might have to tinker with registry.

So the alternative to fix the issue is specify the arguments to run the eclipse, I just had to call eclipse with additional parameters to call specific virtual machine. And that fixed my issue

C:\eclipse\eclipse.exe -vm “C:\Program Files\Java\jdk\jre\bin\javaw.exe” “C:\Program Files\Java\jdk\jre\bin\client\jvm.dll”

Protect your privacy and avoid spam.

srisri's — Fri, 03 Sep 2010 00:23:16 +0000

If you are trying to register at some website which require registration and you don’t want to give your actual email but want to pass through the initial hiccup of entering into the website. Use mailinator.com. You can send all your spam which you don’t care. You can create any number of email addresses on the fly without any registration.

Failed to load or instantiate TagLibraryValidator class: org.apache.taglibs.standard.tlv.JstlCoreTLV

srisri's — Tue, 27 Jul 2010 22:22:37 +0000

Well after few hours of hair pulling at last I could resolve the issue deploying and executing spring-security-application. And I guess I have read lot of people have similar issue with Pet clinic Application.

The issue is simply removing the com.springsource.javax.servlet.jsp.jstl-1.2.0 from your library. or jsp api. It should work.

If it still doesnt work then follow the steps mentioned at this site

Thanks for vising and leave a note if it works.

Sri

Nice screen capture tools

srisri's — Thu, 03 Jun 2010 13:13:38 +0000

Jing

Thank God Its Friday

srisri's — Fri, 19 Mar 2010 18:50:10 +0000

I dont know who invented this statement, but I involuntarily become so lazy on friday’s. I am at work, relaxed and everything happens at a slow pace. Funny meetings, extended lunches, sleepy afternoons. Productivity is pathetic on friday’s, come monday its altogether a different person. I am on springs jumping from one task to another quickly, productivity is at a different level.

Its understood that I can say Thank God Its Friday, but should I really be thanking him or change attitude towards this day. Thank God its Friday I am enlightened. Thank god its Friday you have made me realize this bad attitude. I have 2 more days to correct my laziness.

Before someone wakes me up. Thank God.