First Class Headers - A

Asir S Vedamuthu, webMethods - Monday February 07, 2005

Lets begin with a simple example. The following example shows the WSDL definition of a simple service providing stock quotes. This service supports a single operation called GetLastTradePrice, which is deployed using the SOAP 1.2 protocol over HTTP. I added 3 statements to turn on WS-Security header support. Again, just 3 statements - import schema statement, header in input message reference component and header in output message reference component.

<?xml version="1.0"?>
<wsdl:description name="StockQuote" xmlns:wsdl="http://www.w3.org/@@@@/@@/wsdl"
  targetNamespace="http://example.com/stockquote"
  xmlns:tns="http://example.com/stockquote"
  xmlns:wsoap="http://www.w3.org/@@@@/@@/wsdl/soap"
  xmlns:wsse="http://docs.oasis-open.org/wss/2004/01/oasis-200401-wss-wssecurity-secext-1.0.xsd">
    
  <xs:import
   namespace="http://docs.oasis-open.org/wss/2004/01/oasis-200401-wss-wssecurity-secext-1.0.xsd"
   schemaLocation="http://docs.oasis-open.org/wss/2004/01/oasis-200401-wss-wssecurity-secext-1.0.xsd"/>
     
  <wsdl:types>
    <xs:schema targetNamespace="http://example.com/stockquote"
      xmlns:xs="http://www.w3.org/2001/XMLSchema">
      <xs:element name="TradePriceRequest">
        <xs:complexType>
          <xs:all>
            <xs:element name="tickerSymbol" type="xs:string"/>
          </xs:all>
        </xs:complexType>
      </xs:element>
      <xs:element name="TradePrice">
        <xs:complexType>
          <xs:all>
            <xs:element name="price" type="xs:float"/>
          </xs:all>
        </xs:complexType>
      </xs:element>
    </xs:schema>
  </wsdl:types>
  
  <wsdl:interface name="StockQuoteInterface">
    <wsdl:operation name="GetLastTradePrice" 
      pattern="http://www.w3.org/@@@@/@@/wsdl/in-out">
      <wsdl:input element="tns:GetLastTradePriceInput">
      	<wsdl:header element="wsse:Security" required="true" mustUnderstand="true"/>
      </wsdl:input>
      <wsdl:output element="tns:GetLastTradePriceOutput">
        <wsdl:header element="wsse:Security" required="true" mustUnderstand="true"/>
      </wsdl:output>
    </wsdl:operation>
  </wsdl:interface>
  
  <wsdl:binding name="StockQuoteSoapBinding" interface="tns:StockQuoteInterface"
    type="http://www.w3.org/@@@@/@@/wsdl/soap" 
    wsoap:protocol="http://www.w3.org/2003/05/soap/bindings/HTTP/">
    <wsdl:operation ref="tns:GetLastTradePrice" 
      wsoap:action="http://example.com/GetLastTradePrice"/>
  </wsdl:binding>
  
  <wsdl:service name="StockQuoteService" interface="tns:StockQuoteInterface">
    <wsdl:documentation>My first service</wsdl:documentation>
    <wsdl:endpoint name="StockQuoteEndPoint" binding="tns:StockQuoteBinding" 
    address="http://example.com/endpoint/stockquote"/>
  </wsdl:service>
  
</wsdl:description>

Proposed solution has nine parts:

(1) Introduce a NEW Header Component

Header Component

An Header Component describes an abstract piece of header data (message headers) that is associated with the exchange of messages between the communicating parties. The presence of an Header Component in a WSDL description indicates that the service supports headers and may require a Web Service consumer/client that interacts with the service to use the described header. Zero or more such headers may be used.

Header Component has 5 properties:

{element} REQUIRED. A reference to an XML element declaration in the {element declarations} property of The Description Component. This element represents an header data.
{required} REQUIRED. An xs:boolean. If the value of this property is true, then the Web Service consumer/client MUST use the Header that is identified by the {element} property.
{mustUnderstand} OPTIONAL. An xs:boolean. If the property is true, then the bindings that support expression of mandatory data should mark them as mandatory in an appropriate way.

Header Component's XML Representation is,

<header element="xs:QName" mustUnderstand="xs:boolean"? required="xs:boolean"?>
  <documentation />?
</header>

Header Component's mapping is,

{element} = The element declaration from the {element declarations} property of The Descriptions Component resolved to by the value of the element attribute information item if present, otherwise empty. It is an error for the element attribute information item to have a value and that value does not resolve to a global element declaration from the {element declarations} property of The Descriptions Component.
{mustUnderstand} = actual value of the mustUnderstand attribute information item if present, otherwise absent.
{required} = actual value of the required attribute information item if present, otherwise "false".

(2) Hook Header Component into the Interface Fault Component

Add the property {headers}

Add the property {headers} to the Interface Fault Component: {headers} OPTIONAL. A set of Header components that describe a subset of header data.

In the {headers} property, the Header component's {element} property MUST be unique. That is, multiple Header components for the same element declaration within a given Interface Fault component is disallowed.

Modify the XML Representation of Interface Fault Component

<description>
  <interface>
    <fault
          name="xs:NCName" 
          element="xs:QName"? >
      <documentation />?
      [ <header /> | <feature /> | <property /> ]*
    </fault>
  </interface>
</description>

Modify the Mapping of Interface Fault's XML Representation to Component Properties

Addition to Table 2-3:

{headers} = The set of Header components corresponding to the header element information items in [children], if any.

(3) Hook Header Component into the Message Reference Component

Add the property {headers}

Add the property {headers} to the Message Reference Component: {headers} OPTIONAL. A set of Header components that describe a subset of header data.

In the {headers} property, the Header component's {element} property MUST be unique. That is, multiple Header components for the same element declaration within a given Message Reference component is disallowed.

Modify the XML Representation of Message Reference Component

<description>
  <interface>
    <operation>
      <input
            messageLabel="xs:NCName"?
            element="union of xs:QName, xs:Token"? > 
        <documentation />?
        [ <header /> | <feature /> | <property /> ]*
      </input>
      <output
            messageLabel="xs:NCName"?
            element="union of xs:QName, xs:Token"? >
        <documentation />?
        [ <header /> | <feature /> | <property /> ]*
      </output>
    </operation>
  </interface>
</description>

Modify the Mapping of Message Reference's XML Representation to Component Properties

Addition to Table 2-6:

{headers} = The set of Header components corresponding to the header element information items in [children], if any.

(4) Syntax Level Default Mechanism to Disable Header Construction

Modify the XML Representation of Binding Component

<description>
  <binding
        name="xs:NCName" 
        interface="xs:QName"?
        type="xs:anyURI"
        disableHeadersDefault="xs:boolean"? >
    <documentation />?
    [ <fault /> | <operation /> | <feature /> | <property /> ]*
  </binding>
</description>

The disableHeadersDefault attribute information item allows users to specify a default value for the {disable headers} property of all the Binding Fault and Binding Message Reference Components in a Binding Component. This is a syntactic convenience and does not affect the underlying component model.

(5) Mechanism to Disable Header Construction for the Binding Fault Component

Add the property {disable headers} to Binding Fault Component

{disable headers} OPTIONAL. An xs:boolean. If this property exists and is true, then headers MUST NOT be constructed for this Binding Fault Component. Scope of {disable headers} is limited to the WSDL Header components defined for the Interface Fault Component in {fault reference}. This property does not interact with any other WSDL feature, Bindings, Extensions or Feature and Properties framework.

Modify the XML Representation of Binding Fault Component

<description>
  <binding>
    <fault
          ref="xs:QName" disableHeaders="xs:boolean"? >
      <documentation />?
      [ <feature /> | <property /> ]*
    </fault>
  </binding>
</description>

Modify the Mapping of Binding Fault's XML Representation to Component Properties

Addition to Table 2-11:

{disable headers} = The actual value of the disableHeaders attribute information item, if present. If not, the actual value of the disableHeadersDefault attribute information item of the parent wsdl:binding element information item, if present. If not the value as defined by the concrete binding, if applicable.

(6) Mechanism to Disable Header Construction for the Binding Message Reference Component

Add the property {disable headers} to Binding Message Reference Component

{disable headers} OPTIONAL. An xs:boolean. If this property exists and is true, then headers MUST NOT be constructed for this Binding Message Reference Component. Scope of {disable headers} is limited to the WSDL Header components defined for the Message Reference component being bound by this Binding Message Reference component. This property does not interact with any other WSDL feature, Bindings, Extensions or Feature and Properties framework.

Modify the XML Representation of Binding Message Reference Component

<description>
  <binding>
    <operation>
      <input
            messageLabel="xs:NCName"? disableHeaders="xs:boolean"? >
        <documentation />?
        [ <feature /> | <property /> ]*
      </input>
      <output
            messageLabel="xs:NCName"? disableHeaders="xs:boolean"? >
        <documentation />?
        [ <feature /> | <property /> ]*
      </output>
    </operation>
  </binding>
</description>

Modify the Mapping of Binding Fault's XML Representation to Component Properties

Addition to Table 2-11:

{disable headers} = The actual value of the disableHeaders attribute information item, if present. If not, the actual value of the disableHeadersDefault attribute information item of the ancestor wsdl:binding element information item, if present. If not the value as defined by the concrete binding, if applicable.

(7) Add to SOAP Binding's Default Binding Rules

SOAP Header block construction

Default value of the Binding element's disableHeadersDefault attribute information item is false. Default value of the Binding Fault Component's {disable headers} property and Binding Message Reference Component's {disable headers} property is false.

In the Binding Message Reference or Binding Fault component, if the {disable headers} is false and and if the {headers} property of the bound Message Reference or Interface Fault component exists and non empty, element information item conforming to an Header component's {element} property, in the bound Message Reference or Interface Fault component's {headers} property, MUST be turned into a SOAP Header Block.

These elements are serialized according to their schemas, and if the Header component's {mustUnderstand} property, in the bound Message Reference or Interface Fault component's {headers} property, exists with the value "true", that particular SOAP Header Block should be marked as "mustUnderstand='true'" or "mustUnderstand='1'" as per the SOAP specification.

(8) Add to HTTP Binding's Default Binding Rules

HTTP Header construction

Only element information items of type "xs:string" or "xs:anyURI" may be serialized. All complex data types are ignored. Attributes on data elements are ignored.

Each such element information item is serialized as follows:

The HTTP header name used is the element information item local name. The element information item local name MUST follow the field-name production rules as specified in section 4.2 of [IETF RFC 2616]; if not, the element information item MUST be ignored. If an HTTP header corresponding to the element information item local name is set by a different mechanism other than the HTTP Binding, such as the HTTP stack or another feature, then an error MUST be raised.

The HTTP header content is serialized from the corresponding element information item value in UTF-8. If this serialization is NOT possible, then the element information item MUST be ignored.

(9) Changes to XML Schema for WSDL 2.0

PENDING