org.mycore.util.concurrent.MCRDecorator Maven / Gradle / Ivy
/*
* This file is part of *** M y C o R e ***
* See http://www.mycore.de/ for details.
*
* MyCoRe is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* MyCoRe is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with MyCoRe. If not, see .
*/
package org.mycore.util.concurrent;
import java.util.Optional;
import com.google.common.reflect.TypeToken;
/**
* Classes can implement this interface if they want to use
* the decorator pattern. Contains some static helper methods
* to check if an instance is implementing the decorator.
*
* @author Matthias Eichner
*/
public interface MCRDecorator {
/**
* Returns the enclosing instance.
*
* @return the decorated instance
*/
V get();
/**
* Checks if the given object is decorated by this interface.
*
* @param decorator the interface to check
* @return true if the instance is decorated by an MCRDecorator
*/
static boolean isDecorated(Object decorator) {
return TypeToken.of(decorator.getClass()).getTypes().interfaces().stream()
.filter(tt -> tt.isSubtypeOf(MCRDecorator.class)).findAny().isPresent();
}
/**
* Returns an optional with the enclosing value of the decorator. The decorator
* should implement the {@link MCRDecorator} interface. If not, an empty optional
* is returned.
*
*
* - get: MCRDecorator -> MCRDecorator -> MCRDecorator -> object
*
- resolve: MCRDecorator -> MCRDecorator -> MCRDecorator -> object
*
*
* @param decorator the MCRDecorator
* @return an optional with the decorated instance
*/
@SuppressWarnings("unchecked")
static Optional get(Object decorator) {
if (isDecorated(decorator)) {
try {
return Optional.of(((MCRDecorator) decorator).get());
} catch (Exception exc) {
return Optional.empty();
}
}
return Optional.empty();
}
/**
* Same as {@link #get()}, but returns the last object which does not implement
* the decorator interface anymore.
*
*
* - get: MCRDecorator -> MCRDecorator -> MCRDecorator -> object
*
- resolve: MCRDecorator -> MCRDecorator -> MCRDecorator -> object
*
*
* @param decorator the MCRDecorator
* @return an optional with the decorated instance
*/
static Optional resolve(Object decorator) {
Optional base = get(decorator);
while (base.isPresent()) {
Optional nextLevel = get(base.get());
if (nextLevel.isPresent()) {
base = nextLevel;
} else {
break;
}
}
return base;
}
}