Create custom format handler

If format is not supported, you will need to implement a handler for it by inheriting from DocumentFormatInstance class. Depending on the document’s features and required redactions, you will also need to implement one or several interfaces, allowing GroupDocs.Redaction to work with this document format.

InterfaceDescription
ITextualFormatInstanceRequired for document text redactions to work, replaces occurrences of given regular expression with text or a color block
IMetadataAccessRequired for metadata redactions, reads metadata and changes specific metadata item
IAnnotatedDocumentRequired for annotation redactions, changes or deletes annotations, matching given regular expression
IRasterizableDocumentRequired to rasterize (save document as a PDF with page images)
IImageFormatInstanceRequired for raster image format redactions, based on area top-left corner coordinates and area size

Each of these interfaces is optional, i.e. you don’t have to implement all of them, e.g. IImageFormatInstance - if you don’t need its functionality or IMetadataAccess, if your format does not support metadata.

Below, we create a DocumentFormatInstance class for plain text document, supporting only textual redactions:

import com.groupdocs.redaction.options.RedactorSettings;

public class PlainTextDocument extends DocumentFormatInstance implements ITextualFormatInstance
{
    private RedactorSettings _settings;
    private final java.util.List<String> _fileContent;
 
    public PlainTextDocument()
    {
        _fileContent = new java.util.ArrayList<>();
    }
 
    @Override
    public void initialize(DocumentFormatConfiguration config, RedactorSettings settings)
    {
        _settings = settings;
    }
 
    @Override
    public void load(java.io.InputStream input) throws java.lang.Exception
    {
        _fileContent.clear();
        java.io.BufferedReader reader = new java.io.BufferedReader(
                new java.io.InputStreamReader(input)
        );
        String line = reader.readLine();
        while (line != null)
        {
            _fileContent.add(line);
            line = reader.readLine();
        }            
        reader.close();
    }
 
    @Override
    public void save(java.io.OutputStream output) throws java.lang.Exception
    {
        java.io.BufferedWriter writer = new java.io.BufferedWriter(new java.io.OutputStreamWriter(output));
        for (String line : _fileContent)
        {
            writer.write(line);
        }
        writer.close();
    }
 
    @Override
    public RedactionResult replaceText(java.util.regex.Pattern regex, ReplacementOptions options)
    {
        try
        {
            if (options.getActionType() != ReplacementType.ReplaceString)
            {
                return RedactionResult.failed("This format allows only ReplaceString redactions!");
            }
            for (int i = 0; i < _fileContent.size(); i++)
            {
                _fileContent.set(i, regex.matcher(_fileContent.get(i)).replaceAll(options.getReplacement()));
            }
            return RedactionResult.successful();
        }
        catch (java.lang.Exception ex)
        {
            return RedactionResult.failed(ex.getMessage());
        }
    }
}

In order to use this class, we will need to add it to pre-configured formats, e.g. as a handler for logs ("*.log”):

DocumentFormatConfiguration format = new DocumentFormatConfiguration();
format.setExtensionFilter(".log");
format.setDocumentType(typeof(PlainTextDocument));

RedactorConfiguration config = DocumentFormatInstance.getDefaultConfiguration();
config.getAvailableFormats().add(format);

Security and password protection

If your format supports security options like password protection, you’ll have to pass true or false to SetAccessGranted method of DocumentFormatInstance class in your override of Load method and throw IncorrectPasswordException or PasswordRequiredException, if applicable. For instance:

@Override
public void load(java.io.InputStream input) throws java.lang.Exception
{
    try
    {
		// check security and load document 

        setAccessGranted(true);
    }
    catch (SomeSecurityException ex)
    {
        setAccessGranted(false);
		// Password, provided with LoadOptions
        if (string.IsNullOrEmpty(Password))
            throw new Exceptions.PasswordRequiredException();
        else
            throw new Exceptions.IncorrectPasswordException();
    }
}