Jansi is a small java library that allows you to use ANSI escape codes to format your console output which works even on Windows.
It also provides the required JNI libraries:
- Kernel32 and WindowsSupport for ANSI support on Windows
- CLibrary for POSIX tty functions on Unix and Windows
- Implements ANSI escape colorization/handling that is missing on the Windows platform, using integrated JNI library.
- Strips ANSI escape codes if process output is is being redirected and not attached to a terminal.
- Easy to use Ansi escape sequence builder API.
- JNI access to low-level console features.
Most unix terminals support rendering ANSI escape codes when Java sends them
via System.out, but when this is done on Windows, they don't get interpreted
and you get garbage on the console.
Furthermore, even when on Unix, when process output is being redirected to a file, you typically don't want to output escape codes to the file since most file viewers and editors will not properly display the escape codes.
Jansi detects and abstracts the ANSI support provided by the attached terminal. When your Java application uses Jansi, it can always assume that standard out and error streams support ANSI sequences. Depending on the platform and if the application output is attached to a real terminal, Jansi will do one of the following with the ANSI escape codes that it receives:
- Pass them through untouched
- Filter them out
- Use platform specific APIs to implement the terminal commands represented by the escape sequence
Enabling the Jansi ANSI support into your application is as simple as doing a simple static method call:
import org.fusesource.jansi.AnsiConsole;
...
AnsiConsole.systemInstall();Disabling it is also done via a static method:
AnsiConsole.systemUninstall();It is safe to call those methods multiple times, they keep track of how many
times systemInstall() has been called and only uninstalls when the
systemUninstall() method is called a corresponding number of times.
Using the Ansi escape sequence builder:
import static org.fusesource.jansi.Ansi.*;
import static org.fusesource.jansi.Ansi.Color.*;
...
System.out.println( ansi().eraseScreen().fg(RED).a("Hello").fg(GREEN).a(" World").reset() );The above will clear the screen, write Hello in red and World in green,
then reset the color attributes so that subsequent data printed to the stream
uses the default colors.
But there is an even simpler way to accomplish the above using the render
method:
System.out.println( ansi().eraseScreen().render("@|red Hello|@ @|green World|@") );