* To add the {@code --verbose} option to a command, simply declare a {@code @Mixin}-annotated field with type {@code LoggingMixin} * (if your command is a class), or a {@code @Mixin}-annotated method parameter of type {@code LoggingMixin} if your command * is a {@code @Command}-annotated method. *
** This mixin can be used on multiple commands, on any level in the command hierarchy. *
** Make sure that {@link #configureLoggers} is called before executing any command. * This can be accomplished with: *
* public static void main(String... args) {
* new CommandLine(new MyApp())
* .setExecutionStrategy(LoggingMixin::executionStrategy))
* .execute(args);
* }
*
*/
public class LoggingMixin {
/**
* This mixin is able to climb the command hierarchy because the
* {@code @Spec(Target.MIXEE)}-annotated field gets a reference to the command where it is used.
*/
private @Spec(MIXEE) CommandSpec mixee; // spec of the command where the @Mixin is used
private boolean[] verbosity = new boolean[0];
// Each subcommand that mixes in the LoggingMixin has its own instance of this class,
// so there may be many LoggingMixin instances.
// We want to store the verbosity value in a single, central place, so
// we find the top-level command,
// and store the verbosity level on our top-level command's LoggingMixin.
//
// In the main method, `LoggingMixin::executionStrategy` should be set as the execution strategy:
// that will take the verbosity level that we stored in the top-level command's LoggingMixin
// to configure Log4j2 before executing the command that the user specified.
private static LoggingMixin getTopLevelCommandLoggingMixin(CommandSpec commandSpec) {
return ((MyApp) commandSpec.root().userObject()).loggingMixin;
}
/**
* Sets the specified verbosity on the LoggingMixin of the top-level command.
* @param verbosity the new verbosity value
*/
@Option(names = {"-v", "--verbose"}, description = {
"Specify multiple -v options to increase verbosity.",
"For example, `-v -v -v` or `-vvv`"})
public void setVerbose(boolean[] verbosity) {
getTopLevelCommandLoggingMixin(mixee).verbosity = verbosity;
}
/**
* Returns the verbosity from the LoggingMixin of the top-level command.
* @return the verbosity value
*/
public boolean[] getVerbosity() {
return getTopLevelCommandLoggingMixin(mixee).verbosity;
}
/**
* Configures Log4j2 based on the verbosity level of the top-level command's LoggingMixin,
* before invoking the default execution strategy ({@link picocli.CommandLine.RunLast RunLast}) and returning the result.
* * Example usage: *
*
* public void main(String... args) {
* new CommandLine(new MyApp())
* .setExecutionStrategy(LoggingMixin::executionStrategy))
* .execute(args);
* }
*
*
* @param parseResult represents the result of parsing the command line
* @return the exit code of executing the most specific subcommand
*/
public static int executionStrategy(ParseResult parseResult) {
getTopLevelCommandLoggingMixin(parseResult.commandSpec()).configureLoggers();
return new CommandLine.RunLast().execute(parseResult);
}
/**
* Configures the Log4j2 console appender(s), using the specified verbosity:
*