/// <summary>
/// Attempts to retrieve any stored data from the document cache.
/// </summary>
/// <param name="type"></param>
/// <param name="key"></param>
/// <param name="nav"></param>
/// <returns></returns>
protected virtual bool TryGetCachedData(string type, string key, out XPathDataCacheItem item)
{
object value;
Document doc = this.Document;
if (null == doc)
{
throw new NullReferenceException("This data source is not part of the document heirarchy and cannot use the caching capabilities available");
}
IPDFCacheProvider cacheProv = doc.CacheProvider;
if (null != cacheProv)
{
if (cacheProv.TryRetrieveFromCache(type, key, out value))
{
if (!(value is XPathDataCacheItem))
{
throw new InvalidCastException("The data returned from the cache for this XPath datasource '" + this.ID + "' was not an XPathNavigator.");
}
item = (XPathDataCacheItem)value;
return(true);
}
}
item = null;
return(false);
}
protected System.Data.DataSet CreateSet()
{
if (null == this.LoadedData)
{
this.LoadedData = new XPathDataCacheItem(new System.Data.DataSet(this.ID), null);
return(this.LoadedData.DataSet);
}
else
{
return(this.LoadedData.DataSet);
}
}
/// <summary>
/// Adds the XPath document to the documents cache provider.
/// </summary>
/// <param name="type"></param>
/// <param name="key"></param>
/// <param name="nav"></param>
protected virtual void AddToCache(string type, string key, XPathDataCacheItem item)
{
Document doc = this.Document;
if (null == doc)
{
throw new NullReferenceException("This data source is not part of the document heirarchy and cannot use the caching capabilities available");
}
IPDFCacheProvider cacheProv = doc.CacheProvider;
if (null != cacheProv)
{
DateTime expires = DateTime.Now.AddMinutes(this.CacheDuration);
cacheProv.AddToCache(type, key, item, expires);
}
}
/// <summary>
/// Overrides the base implementation to load the actual data at the path
/// </summary>
/// <param name="path"></param>
/// <param name="context"></param>
/// <param name="root">If true then this is the top level selection of data and should use this sources assigned data. If false then it should use the current data context.</param>
/// <returns></returns>
protected override object DoSelectData(string path, PDFDataContext context)
{
//Get sthe source data from the implementation
string key = this.GetCacheKey(context);
XPathDataCacheItem item = null;
if (null != this.LoadedData)
{
item = this.LoadedData;
}
else if (this.CacheDuration <= 0 || !this.TryGetCachedData(this.Type.ToString(), key, out item))
{
if (context.ShouldLogVerbose)
{
context.TraceLog.Begin(TraceLevel.Verbose, LOG_CATEGORY, "Directly loading the data for datasource component '" + this.ID + "' with cache key '" + key + "'");
}
//Load the actual source data.
item = LoadSourceXPathData(context);
this.LoadedData = item;
//Quick fall-out (don't cache it, as not a normal situation)
if (null == item)
{
context.TraceLog.Add(TraceLevel.Warning, LOG_CATEGORY, "No Data was returned from the Datasource '" + this.ID + "'.");
return(null);
}
//Transform as required
XPathNavigator nav = item.Navigator;
if (null != this.Transformer)
{
nav = this.Transformer.TransformData(item.Navigator, this.CacheDuration, this, context);
}
if (this.CacheDuration > 0)
{
this.AddToCache(this.Type.ToString(), key, item);
if (context.ShouldLogVerbose)
{
context.TraceLog.End(TraceLevel.Verbose, LOG_CATEGORY, "Completed loading the data for datasource component '" + this.ID + "' and added it to the cache with key '" + key + "'");
}
else if (context.ShouldLogMessage)
{
context.TraceLog.Add(TraceLevel.Message, LOG_CATEGORY, "Completed loading the data for datasource component '" + this.ID + "' and added it to the cache with key '" + key + "'");
}
}
else if (context.ShouldLogVerbose)
{
context.TraceLog.End(TraceLevel.Verbose, LOG_CATEGORY, "Completed loading the data for datasource component '" + this.ID + "'. Not cached");
}
else if (context.ShouldLogMessage)
{
context.TraceLog.Add(TraceLevel.Message, LOG_CATEGORY, "Completed loading the data for datasource component '" + this.ID + "'. Not cached");
}
}
else //cache hit
{
this.LoadedData = item;
if (context.ShouldLogMessage)
{
context.TraceLog.Add(TraceLevel.Message, LOG_CATEGORY, "Cache hit on datasource '" + this.ID + "' with cache key '" + key + "'");
}
}
//We have the data
//Now we need a resolver for the prefixes and select statements.
if (null == this.Resolver)
{
this.Resolver = this.Document.CreateNamespaceResolver(this.Namespaces, item.Navigator.NameTable);
}
//Push this onto the context
context.NamespaceResolver = this.Resolver;
XPathNodeIterator itter;
//Finally return the select to return an itterator
if (string.IsNullOrEmpty(path))
{
itter = item.Navigator.Select("*", context.NamespaceResolver);
if (itter.Count == 0)
{
context.TraceLog.Add(TraceLevel.Warning, LOG_CATEGORY, "ZERO items were retrieved from the Datasource '" + this.ID + "'");
}
}
else
{
itter = item.Navigator.Select(path, context.NamespaceResolver);
if (itter.Count == 0)
{
context.TraceLog.Add(TraceLevel.Warning, LOG_CATEGORY, "ZERO items were retrieved from the Datasource '" + this.ID + "' based on the select path '" + path + "'");
}
}
return(itter);
}
