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Custom extractors allow you to use the attachment search feature of document indexes for non-default file types.
To define a custom search text extractor:
Create a class that implements the ISearchTextExtractor interface (CMS.Search namespace).
Define the ExtractContent method.
The ExtractContent method has the following parameters:
Register the extractor for a file extension by calling the SearchTextExtractorManager.RegisterExtractor method.
SearchTextExtractorManager.RegisterExtractor("extension", new CustomExtractorClass());Note: You need to call the RegisterExtractor method at the start of your application (when the application and modules are being initialized).
Rebuild your document search indexes.
The search uses the custom extractor to index document attachments with the specified extension.
Modifying custom extractors
The system stores the text content extracted from document attachments in the database. When rebuilding document indexes, the search loads the "cached" attachment text from the database. The text extraction process only runs for attachments that do not have any search content saved.
If you change the functionality of a custom extractor, you need to clear the attachment content from the database:
You can then Rebuild your document indexes, which updates the attachment content according to your extractor's new functionality.
The following example demonstrates how to create a very basic extractor for .txt files:
Open your web project in Visual Studio.
Create a new class in the App_Code folder (or Old_App_Codeon web application projects). For example, name the class CustomSearchTextExtractor.cs.
Add the following references to the class:
using CMS.Search;
using CMS.Base;
using CMS.Core;
using CMS.IO;
using CMS.DataEngine;Make the class implement the ISearchTextExtractor interface.
public class CustomSearchTextExtractor : ISearchTextExtractorDefine the ExtractContent method:
public XmlData ExtractContent(BinaryData data, ExtractionContext context)
{
if (data.Stream != null)
{
// Reads the text file's data stream
data.Stream.Position = 0;
string resultString = StreamReader.New(data.Stream).ReadToEnd();
// Adds text into the CONTENT search index field
XmlData contentData = new XmlData();
contentData.SetValue(SearchFieldsConstants.CONTENT, resultString);
return contentData;
}
return null;
}Extend the CMSModuleLoader partial class (outside of the CustomSearchTextExtractor class), and add a CMSLoaderAttribute attribute that registers your custom extractor for the .txt extension:
[RegisterCustomExtractors]
public partial class CMSModuleLoader
{
private class RegisterCustomExtractorsAttribute : CMSLoaderAttribute
{
// The system automatically calls the Init method when the application starts
public override void Init()
{
// Registers the CustomSearchText extractor for the .txt extension
SearchTextExtractorManager.RegisterExtractor("txt", new CustomSearchTextExtractor());
}
}
}Save the CustomSearchTextExtractor.cs file.
Log in to the Kentico administration interface.
Open the Smart search application and Rebuild your document search indexes.
The example is only intended as a demonstration — the system already contains a default extractor for .txt files. You can use the same approach to create extractors for other file types.