Set up logging Leave feedback

By default logging is disabled when processing documents, but the product provides embedded implementations that write the log to the console or to a file.

There is an interface that we can utilize:

• ILogger - defines the interface for logging different process event like errors, warnings and information messages (traces).

There are classes that we can utilize:

• ConsoleLogger - defines the methods that are required for logging to console.
• FileLogger - defines the methods that are required for logging to file.

There are 3 types of messages in the log file:

• Error - for unrecoverable exceptions
• Warning - for recoverable/expected/known exceptions
• Trace - for general information

The logger is passed to the SignatureSettings constructor, and the settings are passed to the Signature constructor.

The setLogLevel method of SignatureSettings decides which kinds of messages reach the logger. The values are int flags of the LogLevel class that can be combined with |: LogLevel.Error, LogLevel.Warning and LogLevel.Trace. The default, LogLevel.All, logs all three, and LogLevel.None logs nothing.

SignatureSettings settings = new SignatureSettings(new ConsoleLogger());
// Errors and warnings, without the step-by-step traces.
settings.setLogLevel(LogLevel.Error | LogLevel.Warning);

The level only filters the log: exceptions are thrown as before.

Note

setLogLevel takes effect starting with GroupDocs.Signature for Java 26.10. In earlier versions the level was compared as a single value instead of a set of flags, so with the default LogLevel.All, or with a combination such as LogLevel.Error | LogLevel.Warning, nothing reached the logger.

In this example, we’ll log into the file so we need to use FileLogger class.

// Create logger and specify the output file
FileLogger fileLogger = new FileLogger("output.log");

// Create SignatureSettings and specify FileLogger
SignatureSettings settings = new SignatureSettings(fileLogger);

Signature signature = new Signature("sample.docx", settings);
try
{
    QrCodeSignOptions options = new QrCodeSignOptions("JohnSmith");
    // sign document to file
    signature.sign(outputFilePath, options);
}
finally
{
    signature.dispose();
}

In this example, we’ll log into the console so we need to use ConsoleLogger class.

// Create logger that writes to the console
ConsoleLogger consoleLogger = new ConsoleLogger();

// Create SignatureSettings and specify ConsoleLogger instance
SignatureSettings settings = new SignatureSettings(consoleLogger);

Signature signature = new Signature("sample.docx", settings);
try
{
    QrCodeSignOptions options = new QrCodeSignOptions("JohnSmith");
    // sign document to file
    signature.sign(outputFilePath, options);
}
finally
{
    signature.dispose();
}

The ConsoleLogging, ConsoleLoggingWithLogLevels and FileLogging classes of the Java examples run these loggers with different log levels.

GroupDocs.Signature writes a warning when an operation succeeds but the result may not be what you expect. Warnings are logged when the log level includes LogLevel.Warning, as the default does. Starting with GroupDocs.Signature for Java 26.10, you may see these warnings:

See Certificate validity, digests and logging for the setAllowExpired and setAllowNotYetValid methods.