Difference Between Document Style and RPC Style WebService

A WSDL SOAP binding can be either a Remote Procedure Call (RPC) style binding or a document style binding. A SOAP binding can also have an encoded use or a literal use. This gives you four style/use models:

1. RPC/encoded
2. RPC/literal
3. Document/encoded
4. Document/literal

The terminology here is very unfortunate: RPC versus document. These terms imply that the RPC style should be used for RPC programming models and that the document style should be used for document or messaging programming models. That is not the case at all. The style has nothing to do with a programming model. It merely dictates how to translate a WSDL binding to a SOAP message. Nothing more. You can use either style with any programming model.

the terms encoded and literal are only meaningful for the WSDL-to-SOAP mapping, though, at least here, the traditional meanings of the words make a bit more sense.

See basically there is difference in WSDL and SOAP messages. Now we know there are different parts in WSDL file , the specific pasts having difference are

1.  <message&gt: and 
2. <binding&gt: 

here is how

A message part may declare either a type attribute or an element attribute, but not both. Which to use depends on the kind of messaging you're doing. If you're using RPC-style messaging, the part elements must use the type attribute; if you're using document-style messaging, the part elements must use the element attribute
     RPC Style 
<definitions name="BookPrice" ...>
  ...
  <message name="GetBulkBookPriceRequest">
    <part name="isbn" type="xsd:string"/>
    <part name="quantity" type="xsd:int"/>
  </message>
  <message name="GetBulkBookPriceResponse">
    <part name="price" type="mh:prices" />
  </message>
  ...
</definitions>
Document Style
<message name="SubmitPurchaseOrderMessage">
    <part name="order" element="mh:purchaseOrder" />
  </message>

The soapbind:binding and soapbind:body elements are responsible for expressing the SOAP-specific details of the Web service. 
• soapbind:binding tells us that the "messaging style" is RPC (or document) and that the "network application" protocol is HTTP. 
• The soapbind:body element tells us that both the input and output messages use literal encoding.
You may have noticed that attributes of the soapbind:body element change depending on whether you use RPC- or document-style messaging. The soapbind:body element has four kinds of attributes: 
1. use :- required to be literal ( ?? can it be document?? ) if absent default=literal
2. namespace :- In "rpc"-style messages, the namespace attribute must be specified with a valid URI. In document style it must not be specified.
3. part :- specifies which part elements in the message definition are being used. necessary only if you are using a subset of the part elements declared by a message
4. and encodingStyle : - never used

RPC style specify the namespace attribute in the soapbind:body. In contrast, document-style messages must not specify the namespace attribute in the soapbind:body element. The namespace of the XML document fragment is derived from its XML schema

Example of a rpc style

<?xml version="1.0" encoding="UTF-8"?>

<definitions name="BookQuoteWS"

 targetNamespace="http://www.Monson-Haefel.com/jwsbook/BookQuote"

 xmlns:mh="http://www.Monson-Haefel.com/jwsbook/BookQuote"

 xmlns:soapbind="http://schemas.xmlsoap.org/wsdl/soap/"

 xmlns:xsd="http://www.w3.org/2001/XMLSchema"

 xmlns="http://schemas.xmlsoap.org/wsdl/">

  ...

  <!-- binding tells us which protocols and encoding styles are used -->

  <binding name="BookPrice_Binding" type="mh:BookQuote">

    <soapbind:binding style="rpc"

     transport="http://schemas.xmlsoap.org/soap/http"/>

    <operation name="getBookPrice">

      <soapbind:operation style="rpc"

       soapAction=

       "http://www.Monson-Haefel.com/jwsbook/BookQuote/GetBookPrice"/>

        <input>

          <soapbind:body use="literal"

           namespace="http://www.Monson-Haefel.com/jwsbook/BookQuote" />

        </input>

        <output>

          <soapbind:body use="literal"

           namespace="http://www.Monson-Haefel.com/jwsbook/BookQuote" />

        </output>

    </operation>

  </binding>

  ...

</definitions>

In contrast, document-style messages must not specify the namespace attribute in the soapbind:body element. The namespace of the XML document fragment is derived from its XML schema

<!-- binding tells us which protocols and encoding styles are used -->

<binding name="SubmitPurchaseOrder_Binding" type="mh:SubmitPurchaseOrder">

  <soapbind:binding style="document"

   transport="http://schemas.xmlsoap.org/soap/http"/>

  <operation name="submit">

    <soapbind:operation style="document"/>

      <input>

        <soapbind:body use="literal" />

      </input>

      <output>

        <soapbind:body use="literal" />

      </output>

  </operation>

</binding>

As an example lets consider one java method in all four ways

public void myMethod(int x, float y);
   

RPC Encoded

<message name="myMethodRequest">     <part name="x" type="xsd:int"/>     <part name="y" type="xsd:float"/> </message> <message name="empty"/>   <portType name="PT">     <operation name="myMethod">         <input message="myMethodRequest"/>         <output message="empty"/>     </operation> </portType>   <binding .../> 

Now invoke this method with "5" as the value for parameter x and "5.0" for parameter y. That sends a SOAP message which looks something like below.

 RPC/encoded SOAP message for myMethod

 <soap:envelope>

    <soap:body>

        <myMethod>

            <x xsi:type="xsd:int">5</x>

            <y xsi:type="xsd:float">5.0</y>

        </myMethod>

    </soap:body>

</soap:envelope>

Strengths

• The WSDL is about as straightforward as it's possible for WSDL to be.
• The operation name appears in the message, so the receiver has an easy time dispatching this message to the implementation of the operation.

Weakness

·         The type encoding info (such as xsi:type="xsd:int") is usually just overhead which degrades throughput performance.

·         You cannot easily validate this message since only the 5 and 5.0 lines contain things defined in a schema; the rest of the soap:body contents comes from WSDL definitions.

·         Although it is legal WSDL, RPC/encoded is not WS-I compliant.

RPC Literal

The RPC/literal WSDL for this method looks almost the same as the RPC/encoded WSDL (see Listing 4). The use in the binding is changed from encoded to literal. That's it.

 RPC/literal WSDL for myMethod

<message name="myMethodRequest">

    <part name="x" type="xsd:int"/>

    <part name="y" type="xsd:float"/>

</message>

<message name="empty"/>

<portType name="PT">

    <operation name="myMethod">

        <input message="myMethodRequest"/>

        <output message="empty"/>

    </operation>

</portType>

<binding .../> 

<!-- I won't bother with the details, just assume it's RPC/literal. -->

What about the SOAP message for RPC/literal (see Listing 5)? Here there is a bit more of a change. The type encodings have been removed.

 RPC/literal SOAP message for myMethod

<soap:envelope>

    <soap:body>

        <myMethod>

            <x>5</x>

            <y>5.0</y>

        </myMethod>

    </soap:body>

</soap:envelope>

Strengths

·         The WSDL is still about as straightforward as it is possible for WSDL to be.

·         The operation name still appears in the message.

·         The type encoding info is eliminated.

·         RPC/literal is WS-I compliant.

Weaknesses

·         You still cannot easily validate this message since only the < x ...  >5< / x > and < y ... > 5.0< / y > lines contain things defined in a schema; the rest of the soap:body contents comes from WSDL definitions.

Document Encoded

Nobody follows this style , it's not WSI compliant

Document Literal

The WSDL for document/literal changes somewhat from the WSDL for RPC/literal. The differences are highlighted in bold 

Strengths

• There is no type encoding info.
• You can finally validate this message with any XML validator. Everything within the soap:body is defined in a schema.
• Document/literal is WS-I compliant, but with restrictions (seeweaknesses).

Weaknesses

• The WSDL is getting a bit more complicated. This is a very minor weakness, however, since WSDL is not meant to be read by humans.
• The operation name in the SOAP message is lost. Without the name, dispatching can be difficult, and sometimes impossible.
• WS-I only allows one child of the soap:body in a SOAP message. As you can see in Listing 7, this example's soap:body has two children.
• 
  

WSDL

WSDL stands for Web Service Description Language. as the full form suggests it is a document that describes Web Service.

WSDL is used to specify the exact

•  message format,
• Internet protocol,
• and address 

that a client must use to communicate with a particular Web service.

Note :- that WSDL 1.1 is not specific to SOAP; it can be used to describe non-SOAP-based Web services as well.

A WSDL document contains seven important elements: types, import, message, portType, operations, binding, and service, which are nested in the definitions element.

A WSDL description of a "stock quote" service:

<?xml version="1.0"?>

<definitions name="StockQuote"

             targetNamespace="http://example.com/stockquote.wsdl"

             xmlns:tns="http://example.com/stockquote.wsdl"

             xmlns:xsd1="http://example.com/stockquote.xsd"

             xmlns:soap="http://schemas.xmlsoap.org/wsdl/soap/"

             xmlns="http://schemas.xmlsoap.org/wsdl/">

  <types>

    <schema targetNamespace="http://example.com/stockquote.xsd"

            xmlns="http://www.w3.org/2000/10/XMLSchema">

      <element name="TradePriceRequest">

        <complexType>

          <all>

            <element name="tickerSymbol" type="string"/>

          </all>

        </complexType>

      </element>

      <element name="TradePrice">

         <complexType>

           <all>

             <element name="price" type="float"/>

           </all>

         </complexType>

      </element>

    </schema>

  </types>

  <message name="GetLastTradePriceInput">

    <part name="body" element="xsd1:TradePriceRequest"/>

  </message>

  <message name="GetLastTradePriceOutput">

    <part name="body" element="xsd1:TradePrice"/>

  </message>

  <portType name="StockQuotePortType">

    <operation name="GetLastTradePrice">

      <input message="tns:GetLastTradePriceInput"/>

      <output message="tns:GetLastTradePriceOutput"/>

    </operation>

  </portType>

  <binding name="StockQuoteSoapBinding" type="tns:StockQuotePortType">

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

    <operation name="GetLastTradePrice">

      <soap:operation soapAction="http://example.com/GetLastTradePrice"/>

      <input>

        <soap:body use="literal"/>

      </input>

      <output>

        <soap:body use="literal"/>

      </output>

    </operation>

  </binding>

  <service name="StockQuoteService">

    <documentation>My first service</documentation>

    <port name="StockQuotePort" binding="tns:StockQuoteSoapBinding">

      <soap:address location="http://example.com/stockquote"/>

    </port>

  </service>

</definitions>

• some data types are defined using XML Schema
• some simple message types are defined from the data types
• the port type describes a single operation GetLastTradePrice, which uses the message types for input/output
• the binding tells that the communication is through SOAP
• the port associates the binding with the URI http://example.com/stockquote where the running service can be accessed

The XML Declaration

< ? xml version= " 1 . 0 " encoding = " UTF-8 " ? >

A WSDL document must use either UTF-8 or UTF-16 encoding; other encoding systems are not allowed.

The Definitions Element

The root element of all WSDL documents is the definitions element, which encapsulates the entire document and also provides a WSDL document with its name.

The definitions element usually contains several XML namespace declarations, which is normal for a root element. 

Name attribute is not important nothing refers to it, its optional.

The definitions element also declares a targetNamespace attribute, which identifies the namespace of elements defined in the WSDL document—much as it does in XML schema documents.

The types Element

The types element serves as a container for defining any data types that are not described by the XML schema built-in types: complex types and custom simple types.

You can also define an array type inside type.

The Import Element

The import element makes available in the present WSDL document the definitions from a specified namespace in another WSDL document. This feature can be useful if you want to modularize WSDL documents—for example, to separate the abstract definitions (the types, message, and portType elements) from the concrete definitions (the binding, service, and port elements).

 Use of the import element is convenient, but it can also create versioning headaches. If WSDL documents are maintained separately, the risk of an imported document being changed without regard to the WSDL documents that import it is pretty high. Take care to ensure that imported WSDL documents are not changed without considering versioning.

You can use import and types together, but you should list the import elements before the types element in a WSDL document.

The WSDL Abstract Interface the message type , portType , and Operations Element

The abstract interface of the Web service is described by

•          message,
•          portType,
•         and operation elements

Message	Can be simple or complex or simple custom
Operation	Like a java method , defines input & output messages for an operation.
Port Type	Like interface ( collections of operation )

The Message Type

describes outgoing and ingoing messages. The way to define a message element depends on whether you use RPC-style or document-style messaging.

They may describe

•         call parameters,
•         call return values,
•         header blocks,
•         or faults

        A message part may declare either a type attribute or an element attribute, but not both. Which to use depends on the kind of messaging you're doing. If you're using RPC-style messaging, the part elements must use the type attribute; if you're using document-style messaging, the part elements must use the element attribute

     RPC Style 

<definitions name="BookPrice" ...>

  ...

  <message name="GetBulkBookPriceRequest">

    <part name="isbn" type="xsd:string"/>

    <part name="quantity" type="xsd:int"/>

  </message>

  <message name="GetBulkBookPriceResponse">

    <part name="price" type="mh:prices" />

  </message>

  ...

</definitions>

Document Style

<message name="SubmitPurchaseOrderMessage">

    <part name="order" element="mh:purchaseOrder" />

  </message>

The Port Type

A portType defines the abstract interface of a Web service.

The "methods" of the portType are its operation elements.

Binding Element

 The binding element maps an abstract portType to a set of

·         concrete protocols such as SOAP and HTTP,

·         messaging styles (RPC or document),

·         and encoding styles (Literal or SOAP Encoding).

The Service and port elements

The service element contains one or more port elements, each of which represents a different Web service.

how WSDL tells if WebService is one way or two way.

The port type  should have input and output. input before ouptput indicates that in coming msg shud come before outgoing.

<portType name="BookQuote">

  <operation name="getBookPrice">

     <input name="isbn" message="mh:GetBookPriceRequest"/>

     <output name="price" message="mh:GetBookPriceResponse"/>

     <fault name="InvalidArgumentFault" message="mh:InvalidArgumentFault"/>

     <fault name="SecurityFault" message="mh:SecurityFault"/>

  </operation>

</portType>

and one way messaging is like

<portType name="SubmitPurchaseOrder_PortType">

  <operation name="SubmitPurchaseOrder">

     <input name="order" message="mh:SubmitPurchaseOrderMessage"/>

  </operation>

</portType>