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/*
* Copyright 2011 Vaadin Ltd.
*
* 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.
*/
package com.vaadin.data.util;
import com.vaadin.data.Property;
import com.vaadin.data.Property.ValueChangeEvent;
import com.vaadin.data.Property.ValueChangeNotifier;
/**
* Wrapper class that helps implement two-phase commit for a non-transactional
* property.
*
* When accessing the property through the wrapper, getting and setting the
* property value take place immediately. However, the wrapper keeps track of
* the old value of the property so that it can be set for the property in case
* of a roll-back. This can result in the underlying property value changing
* multiple times (first based on modifications made by the application, then
* back upon roll-back).
*
* Value change events on the {@link TransactionalPropertyWrapper} are only
* fired at the end of a successful transaction, whereas listeners attached to
* the underlying property may receive multiple value change events.
*
* @see com.vaadin.data.Property.Transactional
*
* @author Vaadin Ltd
* @since 7.0
*
* @param <T>
*/
public class TransactionalPropertyWrapper<T> extends AbstractProperty<T>
implements ValueChangeNotifier, Property.Transactional<T> {
private Property<T> wrappedProperty;
private boolean inTransaction = false;
private boolean valueChangePending;
private T valueBeforeTransaction;
public TransactionalPropertyWrapper(Property<T> wrappedProperty) {
this.wrappedProperty = wrappedProperty;
if (wrappedProperty instanceof ValueChangeNotifier) {
((ValueChangeNotifier) wrappedProperty)
.addListener(new ValueChangeListener() {
@Override
public void valueChange(ValueChangeEvent event) {
fireValueChange();
}
});
}
}
@Override
public Class getType() {
return wrappedProperty.getType();
}
@Override
public T getValue() {
return wrappedProperty.getValue();
}
@Override
public void setValue(T newValue) throws ReadOnlyException {
// Causes a value change to be sent to this listener which in turn fires
// a new value change event for this property
wrappedProperty.setValue(newValue);
}
@Override
public void startTransaction() {
inTransaction = true;
valueBeforeTransaction = getValue();
}
@Override
public void commit() {
endTransaction();
}
@Override
public void rollback() {
try {
wrappedProperty.setValue(valueBeforeTransaction);
} finally {
valueChangePending = false;
endTransaction();
}
}
protected void endTransaction() {
inTransaction = false;
valueBeforeTransaction = null;
if (valueChangePending) {
fireValueChange();
}
}
@Override
protected void fireValueChange() {
if (inTransaction) {
valueChangePending = true;
} else {
super.fireValueChange();
}
}
public Property<T> getWrappedProperty() {
return wrappedProperty;
}
}
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