Introduction
The way I previously created messages to send to
the GovTalk service I used
the XMLDocument to create
the request. While this worked it left a number of problems; not least that for every message a special function would need to created. This is OK for
the short term but
the biggest cost
in any software project is maintenance and this would be a headache to maintain. So
the following is a somewhat better way of achieving
the same thing. For
the purposes of this article I am going to be using
the CompanyNumberSearch request of
the GovTalk service – although this technique would work for any service that accepted XML.
The C# functions which send and receive
the messages remain
the same.
The magic
sauce in this is
the XSLT which defines
the structure of
the request, and
the use of objects
in conjunction with reflection to provide
the content. It is a bit like Sweet Chilli
Sauce added to Chicken on a bed of rice. So on to
the Sweet Chilli
Sauce The Sweet Chilli
Sauce The request to search for a company based on it’s number is as follows; <GovTalkMessage xsi:schemaLocation="http://www.govtalk.gov.uk/CM/envelope http://xmlgw.companieshouse.gov.uk/v1-0/schema/Egov_ch-v2-0.xsd" xmlns="http://www.govtalk.gov.uk/CM/envelope" xmlns:dsig="http://www.w3.org/2000/09/xmldsig#" xmlns:gt="http://www.govtalk.gov.uk/schemas/govtalk/core" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" >
<EnvelopeVersion>1.0</EnvelopeVersion>
<Header>
<MessageDetails>
<Class>NumberSearch</Class>
<Qualifier>request</Qualifier>
<TransactionID>1</TransactionID>
</MessageDetails>
<SenderDetails>
<IDAuthentication>
<SenderID>????????????????????????????????</SenderID>
<Authentication>
<Method>CHMD5</Method>
<Value>????????????????????????????????</Value>
</Authentication>
</IDAuthentication>
</SenderDetails>
</Header>
<GovTalkDetails>
<Keys/>
</GovTalkDetails>
<Body>
<NumberSearchRequest xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="http://xmlgw.companieshouse.gov.uk/v1-0/schema/NumberSearch.xsd">
<PartialCompanyNumber>99999999</PartialCompanyNumber>
<DataSet>LIVE</DataSet>
<SearchRows>1</SearchRows>
</NumberSearchRequest>
</Body>
</GovTalkMessage>
This is
the XML that we send to
the GovTalk Service and we get back a list of companies that match
the criteria passed
A message is structured
in two parts;
The envelope which identifies
the person sending
the request, with
the name of
the request, and
the body which gives
the detail of
the company we are looking for.
The Chilli
What makes it possible is
the use of XSLT to define
the message – and serialization to convert each request object into XML. To start we need to create an object which will represent
the contents of
the message we are sending. However there is a common properties
in all
the messages that we send to Companies House. These properties are as follows
SenderId –
the id of
the person sending
the message
SenderPassword –
the password associated with Id
TransactionId – Unique identifier for
the message
AuthenticationValue – authenticates
the request
Because these properties are unique to
the Companies House message, and because they are shared with all messages they are perfect candidates for a base class.
The class is as follows;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Security.Cryptography;
using System.Text;
using System.Text.RegularExpressions;
using Microsoft.WindowsAzure.ServiceRuntime;
namespace CompanyHub.Services
{
public class GovTalkRequest
{
public GovTalkRequest()
{
try
{
SenderID = RoleEnvironment.GetConfigurationSettingValue("SenderId");
SenderPassword = RoleEnvironment.GetConfigurationSettingValue("SenderPassword");
TransactionId = DateTime.Now.Ticks.ToString();
AuthenticationValue = EncodePassword(String.Format("{0}{1}{2}", SenderID, SenderPassword, TransactionId));
}
catch (System.Exception ex)
{
throw ex;
}
}
/// <summary>
/// returns
the Sender ID to be used when communicating with
the GovTalk Service
/// </summary>
public String SenderID
{
get;
set;
}
/// <summary>
/// return
the password to be used when communicating with
the GovTalk Service
/// </summary>
public String SenderPassword
{
get;
set;
} // end SenderPassword
/// <summary>
/// Transaction Id - uses
the Time and Date converted to Ticks
/// </summary>
public String TransactionId
{
get;
set;
} // end TransactionId
/// <summary>
/// calculate
the authentication value that will be used when
/// communicating with
/// </summary>
public String AuthenticationValue
{
get;
set;
} // end AuthenticationValue property
/// <summary>
/// encodes password(s) using MD5
/// </summary>
/// <param name="clearPassword"></param>
/// <returns></returns>
public static String EncodePassword(String clearPassword)
{
MD5CryptoServiceProvider md5Hasher = new MD5CryptoServiceProvider();
byte[] hashedBytes;
UTF32Encoding encoder = new UTF32Encoding();
hashedBytes = md5Hasher.ComputeHash(ASCIIEncoding.Default.GetBytes(clearPassword));
String result = Regex.Replace(BitConverter.ToString(hashedBytes), "-", "").ToLower();
return result;
}
}
}
There is nothing particularly clever here, except for
the EncodePassword method which hashes
the value made up of
the SenderId, Password and Transaction id.
Each message inherits from this object. So for
the Company Number Search
in addition to
the properties above we need a partial number, which dataset to search – for
the purposes of
the project we only need to search
the LIVE set so this can be set
in the constructor and
the SearchRows. Again all are set as properties. With
the SearchRows and DataSet initialized
in the constructor.
public class CompanyNumberSearchRequest : GovTalkRequest, IDisposable
{
/// <summary>
///
/// </summary>
public CompanyNumberSearchRequest() : base()
{
DataSet = "LIVE";
SearchRows = 1;
}
/// <summary>
/// Company Number to search against
/// </summary>
public String PartialCompanyNumber { get; set; }
/// <summary>
/// What DataSet should be searched for
the company
/// </summary>
public String DataSet { get; set; }
/// <summary>
/// How many rows should be returned
/// </summary>
public int SearchRows { get; set; }
public void Dispose()
{
DataSet = String.Empty;
PartialCompanyNumber = String.Empty;
DataSet = "LIVE";
SearchRows = 1;
}
}
As well as inheriting from our base class, I have also inherited from IDisposable – not just because it is just plain good practice to dispose of objects when coding, but it gives also gives us more versatility when using
the object.
There are four stages
in making a request and this is reflected
in the four methods we execute
in making a call to
the Companies House service;
Create a request
Send a request
Check
the status
If OK then get
the results of
the request
I’ve implemented each of these stages within a static class called Toolbox – which also means I don’t need to create an instance of
the class to use it.
When making a request there are three stages;
Get
the template for
the message
Serialize
the object representing
the message
Transform
the serialized object using a predefined XSLT file.
Each of my templates I have defined as an embedded resource. When retrieving a resource of this kind we have to include
the full namespace to
the resource.
In making
the code re-usable as much as possible I defined
the full ‘path’ within
the GetRequest method.
requestFile = String.Format("CompanyHub.Services.Schemas.{0}", RequestFile);
So we now have
the full path of
the file within
the assembly. Now all we need do is retrieve
the assembly and get
the resource.
asm = Assembly.GetExecutingAssembly();
sr = asm.GetManifestResourceStream(requestFile);
Once retrieved
So this can be returned to
the calling function and we now have a stream of XSLT to define
the message. Time now to serialize
the request to create
the other side of this message.
// Serialize object containing Request, Load into XML Document
t = Obj.GetType();
ms = new MemoryStream();
serializer = new XmlSerializer(t);
xmlTextWriter = new XmlTextWriter(ms, Encoding.ASCII);
serializer.Serialize(xmlTextWriter, Obj);
ms = (MemoryStream)xmlTextWriter.BaseStream;
GovTalkRequest = Toolbox.ConvertByteArrayToString(ms.ToArray());
First off we need
the type of
the object so we make a call to
the GetType method of
the object containing
the Message properties.
Next we need a MemoryStream, XmlSerializer and an XMLTextWriter so these can be initialized.
The object is serialized by making
the call to
the Serialize method of
the serializer object.
The result of that is then converted into a MemoryStream. That MemoryStream is then converted into a string.
ConvertByteArrayToString
This is a fairly simple function which uses an ASCIIEncoding object found within
the System.Text namespace to convert an array of bytes into a string.
public static String ConvertByteArrayToString(byte[] bytes)
{
System.Text.ASCIIEncoding enc = new System.Text.ASCIIEncoding();
return enc.GetString(bytes);
}
I only put it into a function because I will be using this
in various places.
The Sauce
When adding support for other messages outside of creating a new object to store
the properties of
the message,
the C# components do not need to change. It is
in the XSLT file that
the versatility of
the technique lies.
The XSLT file determines
the format of
the message. For
the CompanyNumberSearch
the XSLT file is as follows;
<?xml version="1.0"?>
<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
<xsl:template match="/">
<GovTalkMessage xsi:schemaLocation="http://www.govtalk.gov.uk/CM/envelope http://xmlgw.companieshouse.gov.uk/v1-0/schema/Egov_ch-v2-0.xsd" xmlns="http://www.govtalk.gov.uk/CM/envelope" xmlns:dsig="http://www.w3.org/2000/09/xmldsig#" xmlns:gt="http://www.govtalk.gov.uk/schemas/govtalk/core" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" >
<EnvelopeVersion>1.0</EnvelopeVersion>
<Header>
<MessageDetails>
<Class>NumberSearch</Class>
<Qualifier>request</Qualifier>
<TransactionID>
<xsl:value-of select="CompanyNumberSearchRequest/TransactionId"/>
</TransactionID>
</MessageDetails>
<SenderDetails>
<IDAuthentication>
<SenderID><xsl:value-of select="CompanyNumberSearchRequest/SenderID"/></SenderID>
<Authentication>
<Method>CHMD5</Method>
<Value>
<xsl:value-of select="CompanyNumberSearchRequest/AuthenticationValue"/>
</Value>
</Authentication>
</IDAuthentication>
</SenderDetails>
</Header>
<GovTalkDetails>
<Keys/>
</GovTalkDetails>
<Body>
<NumberSearchRequest xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="http://xmlgw.companieshouse.gov.uk/v1-0/schema/NumberSearch.xsd">
<PartialCompanyNumber>
<xsl:value-of select="CompanyNumberSearchRequest/PartialCompanyNumber"/>
</PartialCompanyNumber>
<DataSet>
<xsl:value-of select="CompanyNumberSearchRequest/DataSet"/>
</DataSet>
<SearchRows>
<xsl:value-of select="CompanyNumberSearchRequest/SearchRows"/>
</SearchRows>
</NumberSearchRequest>
</Body>
</GovTalkMessage>
</xsl:template>
</xsl:stylesheet>
The outer two tags define that this is a XSLT stylesheet and
the root tag from which
the nodes are searched for.
The GovTalkMessage is
the format of
the message that will be sent to Companies House.
We first set up
the XslCompiledTransform object which will transform
the XSLT template and
the serialized object into
the request to Companies House.
xslt = new XslCompiledTransform();
resultStream = new MemoryStream();
writer = new XmlTextWriter(resultStream, Encoding.ASCII);
doc = new XmlDocument();
The Serialize method require XmlTextWriter to write
the XML (writer) and a stream to place
the transferred object into (writer).
The XML will be loaded into an XMLDocument object (doc) prior to
the transformation.
// create XSLT Template
xslTemplate = Toolbox.GetRequest(Template);
xslTemplate.Seek(0, SeekOrigin.Begin);
templateReader = XmlReader.Create(xslTemplate);
xslt.Load(templateReader);
I have stored all
the templates as a series of Embedded Resources and
the GetRequestCall takes
the name of
the template and extracts
the relevent XSLT file.
/// <summary>
/// Gets
the framwork XML which makes
the request
/// </summary>
/// <param name="RequestFile"></param>
/// <returns></returns>
public static Stream GetRequest(String RequestFile)
{
String requestFile = String.Empty;
Stream sr = null;
Assembly asm = null;
try
{
requestFile = String.Format("CompanyHub.Services.Schemas.{0}", RequestFile);
asm = Assembly.GetExecutingAssembly();
sr = asm.GetManifestResourceStream(requestFile);
}
catch (Exception)
{
throw;
}
finally
{
asm = null;
}
return sr;
} // end private static stream GetRequest
We first take
the template name and expand it to include
the full namespace to
the Embedded Resource I like to keep all my schemas
in the same directory and so
the namespace reflects this.
The rest is
the default namespace for
the project.
Then we get
the currently executing assembly (which will contain
the resources with
the call to GetExecutingAssembly() )
Finally we get a stream which contains
the XSLT file. We use this stream and then load an XmlReader with
the contents of
the template, and that is
in turn loaded into
the XslCompiledTransform object.
We convert
the object containing
the message properties into Xml by serializing it; calling
the Serialize() method of
the XmlSerializer object. To set up
the object we do
the following;
t = Obj.GetType();
ms = new MemoryStream();
serializer = new XmlSerializer(t);
xmlTextWriter = new XmlTextWriter(ms, Encoding.ASCII);
We first determine
the type of
the object being transferred by calling GetType() We create an XmlSerializer object by passing
the type of
the object being serialized.
The serializer writes to a memory stream and that is linked to an XmlTextWriter.
Next job is to serialize
the object and load it into an XmlDocument.
serializer.Serialize(xmlTextWriter, Obj);
ms = (MemoryStream)xmlTextWriter.BaseStream;
xmlRequest = new XmlTextReader(ms);
GovTalkRequest = Toolbox.ConvertByteArrayToString(ms.ToArray());
doc.LoadXml(GovTalkRequest);
Time to transform
the XML to construct
the full request.
xslt.Transform(doc, writer);
resultStream.Seek(0, SeekOrigin.Begin);
request = Toolbox.ConvertByteArrayToString(resultStream.ToArray());
So that creates
the full request to be sent to Companies House.
Sending
the request
So far we have a string with a request for
the Companies House service. Now we need to send
the request to
the Companies House Service.
Configuration within an Azure project
There are entire blog entries written about configuration within an Azure project – most of this is out of scope for this article but
the following is a summary.
Configuration is defined
in two files within
the parent project *.csdef which contains
the definition of configuration setting.
<?xml version="1.0" encoding="utf-8"?>
<ServiceDefinition name="OnlineCompanyHub" xmlns="http://schemas.microsoft.com/ServiceHosting/2008/10/ServiceDefinition">
<WebRole name="CompanyHub.Host">
<InputEndpoints>
<InputEndpoint name="HttpIn" protocol="http" port="80" />
</InputEndpoints>
<ConfigurationSettings>
<Setting name="DiagnosticsConnectionString" />
<Setting name="DataConnectionString" />
</ConfigurationSettings>
</WebRole>
<WebRole name="CompanyHub.Services">
<InputEndpoints>
<InputEndpoint name="HttpIn" protocol="http" port="8080" />
</InputEndpoints>
<ConfigurationSettings>
<Setting name="DiagnosticsConnectionString" />
<Setting name="SenderId"/>
<Setting name="SenderPassword" />
<Setting name="GovTalkUrl"/>
</ConfigurationSettings>
</WebRole>
<WorkerRole name="CompanyHub.Worker">
<ConfigurationSettings>
<Setting name="DiagnosticsConnectionString" />
</ConfigurationSettings>
</WorkerRole>
</ServiceDefinition>
Above is
the configuration definition from
the project. What we are interested
in however is
the ConfigurationSettings tag of
the CompanyHub.Services WebRole.
There are four configuration settings here, but at
the moment we are interested
in the second to forth settings; SenderId, SenderPassword and GovTalkUrl
The value of these settings are defined
in the ServiceDefinition.cscfg file;
<?xml version="1.0"?>
<ServiceConfiguration serviceName="OnlineCompanyHub" xmlns="http://schemas.microsoft.com/ServiceHosting/2008/10/ServiceConfiguration">
<Role name="CompanyHub.Host">
<Instances count="2" />
<ConfigurationSettings>
<Setting name="DiagnosticsConnectionString" value="UseDevelopmentStorage=true" />
<Setting name="DataConnectionString" value="UseDevelopmentStorage=true" />
</ConfigurationSettings>
</Role>
<Role name="CompanyHub.Services">
<Instances count="2" />
<ConfigurationSettings>
<Setting name="DiagnosticsConnectionString" value="UseDevelopmentStorage=true" />
<Setting name="SenderId" value="UserID"/>
<Setting name="SenderPassword" value="Password"/>
<Setting name="GovTalkUrl" value="http://xmlgw.companieshouse.gov.uk/v1-0/xmlgw/Gateway"/>
</ConfigurationSettings>
</Role>
<Role name="CompanyHub.Worker">
<Instances count="2" />
<ConfigurationSettings>
<Setting name="DiagnosticsConnectionString" value="UseDevelopmentStorage=true" />
</ConfigurationSettings>
</Role>
</ServiceConfiguration>
Look for
the Role tag that contains our project name (CompanyHub.Services).
Having configured
the parameters we can now transmit
the request. This is done by ‘POST’ing a stream of XML to
the Companies House servers.
govTalkUrl = RoleEnvironment.GetConfigurationSettingValue("GovTalkUrl");
request = WebRequest.Create(govTalkUrl);
request.Method = "POST";
request.ContentType = "text/xml";
writer = new StreamWriter(request.GetRequestStream());
writer.WriteLine(RequestMessage);
writer.Close();
We use
the WebRequest object to send
the object. Set
the method of sending to ‘POST’ and
the type of data as text/xml. Once set up all we do is write
the request to
the writer – this sends
the request to Companies House.
Did
the Request Work Part I – Getting
the response
Having sent a request – we now need
the result of that request.
response = request.GetResponse();
reader = response.GetResponseStream();
result = Toolbox.ConvertByteArrayToString(Toolbox.ReadFully(reader));
The WebRequest object has a GetResponse() method which allows us to get
the response sent back. Like many of these calls
the results come
in the form of a stream which we convert into a string.
Did
the Request Work Part II – Translating
the Response
Much like XSLT and XML were used to create
the original request, so it can be used to extract
the response and by deserializing
the result we create an object that contains
the response.
Did it work?
It would be really great if everything worked all
the time. Of course if it did then I don’t suppose people would pay me and others
the big bucks so that our programmes do not
a) Collapse
in a heap (this is an area of memory)
b) Blow every fuse
in the place
in a shower of sparks (this will probably not happen this being real life and not a Hollywood movie, but it was possible to blow
the sound system of a BBC Model B with a poorly coded setting)
c) Go nuts and trap everyone outside
the airlock (this was from a movie, and unless NASA get a manned moon/mars mission set up unlikely to happen)
d) Go nuts and take over
the world (this was also from a movie, but please note life has a habit of being of exceeding
the wildest imaginations of Hollywood writers (note writers – Hollywood executives have no imagination and judging by recent output of that town have turned plagiarism into an art form).
e) Freeze
in total confusion because
the cleaner pulled
the plug to
the internet router (this has happened)
So anyway – we need to check to see if our request actually worked. Within
the GovTalk response there is a section that details
the status of
the message and a description of what went wrong (if anything did). I have defined an XSLT template which will extract these into an XML document.
<?xml version="1.0"?>
<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
xmlns:ev="http://www.govtalk.gov.uk/CM/envelope"
xmlns:gt="http://www.govtalk.gov.uk/schemas/govtalk/core"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
<xsl:template match="/">
<GovTalkStatus xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:xsd="http://www.w3.org/2001/XMLSchema">
<Status>
<xsl:value-of select="ev:GovTalkMessage/ev:Header/ev:MessageDetails/ev:Qualifier"/>
</Status>
<Text>
<xsl:value-of select="ev:GovTalkMessage/ev:GovTalkDetails/ev:GovTalkErrors/ev:Error/ev:Text"/>
</Text>
<Location>
<xsl:value-of select="ev:GovTalkMessage/ev:GovTalkDetails/ev:GovTalkErrors/ev:Error/ev:Location"/>
</Location>
<Number>
<xsl:value-of select="ev:GovTalkMessage/ev:GovTalkDetails/ev:GovTalkErrors/ev:Error/ev:Number"/>
</Number>
<Type>
<xsl:value-of select="ev:GovTalkMessage/ev:GovTalkDetails/ev:GovTalkErrors/ev:Error/ev:Type"/>
</Type>
</GovTalkStatus>
</xsl:template>
</xsl:stylesheet>
Only thing different about previous XSL files is
the references to two namespaces ev & gt. These are defined
in the GovTalk response at
the top of
the response;
xsi:schemaLocation="http://www.govtalk.gov.uk/CM/envelope http://xmlgw.companieshouse.gov.uk/v1-0/schema/Egov_ch-v2-0.xsd"
xmlns="http://www.govtalk.gov.uk/CM/envelope"
xmlns:dsig="http://www.w3.org/2000/09/xmldsig#"
xmlns:gt="http://www.govtalk.gov.uk/schemas/govtalk/core"
If we do not put these references into
the XSLT template then
the XslCompiledTransform object will not be able to find
the relevant tags.
Deserialization is a fairly simple activity.
encoder = new ASCIIEncoding();
ms = new MemoryStream(encoder.GetBytes(statusXML));
serializer = new XmlSerializer(typeof(GovTalkStatus));
xmlTextWriter = new XmlTextWriter(ms, Encoding.ASCII);
messageStatus = (GovTalkStatus)serializer.Deserialize(ms);
We set up a serialization object using
the object type containing
the error state and pass to it
the results of a transformation between
the XSLT above and
the GovTalk response.
Now we have an object containing any error state, and
the error message. All we need to do is check
the status. If there is an error then we can flag an error. If not then we extract
the results and pass that as an object back to
the calling function. We go this by guess what – defining an XSLT template for
the result and using that to create an Xml Stream which can be deserialized into a .Net object.
In this instance
the XSLT to create
the result of a Company Number Search is;
<?xml version="1.0" encoding="us-ascii"?>
<xsl:stylesheet version="1.0"
xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
xmlns:ev="http://www.govtalk.gov.uk/CM/envelope"
xmlns:sch="http://xmlgw.companieshouse.gov.uk/v1-0/schema"
exclude-result-prefixes="ev">
<xsl:template match="/">
<CompanySearchResult xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:xsd="http://www.w3.org/2001/XMLSchema">
<CompanyNumber>
<xsl:value-of select="ev:GovTalkMessage/ev:Body/sch:NumberSearch/sch:CoSearchItem/sch:CompanyNumber"/>
</CompanyNumber>
<CompanyName>
<xsl:value-of select="ev:GovTalkMessage/ev:Body/sch:NumberSearch/sch:CoSearchItem/sch:CompanyName"/>
</CompanyName>
</CompanySearchResult>
</xsl:template>
</xsl:stylesheet>
and
the object definition is;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
namespace CompanyHub.Services
{
public class CompanySearchResult
{
public CompanySearchResult()
{
CompanyNumber = String.Empty;
CompanyName = String.Empty;
}
public String CompanyNumber { get; set; }
public String CompanyName { get; set; }
}
}
Our entire code to make calls to send a request, and interpret
the results are;
String request = String.Empty;
String response = String.Empty;
GovTalkStatus status = null;
fault = null;
try
{
using (CompanyNumberSearchRequest requestObj = new CompanyNumberSearchRequest())
{
requestObj.PartialCompanyNumber = CompanyNumber;
request = Toolbox.CreateRequest(requestObj, "CompanyNumberSearch.xsl");
response = Toolbox.SendGovTalkRequest(request);
status = Toolbox.GetMessageStatus(response);
if (status.Status.ToLower() == "error")
{
fault = new HubFault()
{
Message = status.Text
};
}
else
{
Object obj = Toolbox.GetGovTalkResponse(response, "CompanyNumberSearchResult.xsl", typeof(CompanySearchResult));
}
}
}
catch (FaultException<ArgumentException> ex)
{
fault = new HubFault()
{
FaultType = ex.Detail.GetType().FullName,
Message = ex.Detail.Message
};
}
catch (System.Exception ex)
{
fault = new HubFault()
{
FaultType = ex.GetType().FullName,
Message = ex.Message
};
}
finally
{
}
Wrap up
So there we have it – a reusable set of functions to send and interpret XML results from an internet based service.
The code is reusable with a little change with any service which uses XML as a transport mechanism – and as for
the Companies House GovTalk service all I need to do is create various objects for
the result and message sent and
the relevent XSLT files. I might need minor changes for other services but something like 70-90% will be exactly
the same.
