CliAvailabilityIndicator.java

package org.springframework.roo.shell;

import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;

/**
 * Annotates a method that can indicate whether a particular command is
 * presently available or not.
 * <p>
 * This annotation must only be applied to a public no-argument method that
 * returns primitive boolean. The method should be inexpensive to evaluate, as
 * this method can be called very frequently. If expensive operations are
 * necessary to compute command availability, it is suggested the method return
 * a boolean field that is maintained using the observer pattern.
 * <p>
 * It is possible that a particular availability method might be able to
 * represent the availability status of multiple commands. As such, an
 * availability indicator annotation will indicate the commands that it applies
 * to. If a specific command has multiple aliases (ie by using an array for
 * {@link CliCommand#value()}), only one of the commands need to be specified in
 * the {@link CliAvailabilityIndicator} annotation.
 * 
 * @author Ben Alex
 * @since 1.0
 */
@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.METHOD)
public @interface CliAvailabilityIndicator {

  /**
   * @return the name of the command or commands that this availability
   *         indicator represents
   */
  String[] value();
}