com.getperka.flatpack.visitors.SingletonContext Maven / Gradle / Ivy
package com.getperka.flatpack.visitors;
/*
* #%L
* FlatPack serialization code
* %%
* Copyright (C) 2012 - 2013 Perka Inc.
* %%
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
* #L%
*/
import com.getperka.flatpack.FlatPackVisitor;
import com.getperka.flatpack.ext.Acceptor;
import com.getperka.flatpack.ext.VisitorContext;
/**
* Allows a single value to be be replaced.
*
* @param the value type
*/
public class SingletonContext extends VisitorContext implements Acceptor {
private T value;
protected SingletonContext() {}
@Override
public T accept(FlatPackVisitor visitor, T singleton) {
getWalker().walk(visitor, singleton, this);
return getValue(singleton);
}
@Override
public boolean canReplace() {
return true;
}
@Override
public void replace(T newValue) {
ensure(canReplace());
markReplaced();
this.value = newValue;
}
/**
* Visible for testing.
*/
T getValue(T fallback) {
return didRemove() ? null : didReplace() ? value : fallback;
}
}