/*
* Copyright 2000-2017 JetBrains s.r.o.
*
* 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.intellij.openapi.components;
import org.jetbrains.annotations.Nullable;
/**
* Every component which would like to persist its state across IDEA restarts
* should implement this interface.
*
* See <a href="http://www.jetbrains.org/intellij/sdk/docs/basics/persisting_state_of_components.html">IntelliJ Platform SDK DevGuide</a>
* for detailed description.
*
* In general, implementation should be thread-safe, because "loadState" is called from the same thread where component is initialized.
* If component used only from one thread (e.g. EDT), thread-safe implementation is not required.
*/
public interface PersistentStateComponent<T> {
/**
* @return a component state. All properties, public and annotated fields are serialized. Only values, which differ
* from default (i.e. the value of newly instantiated class) are serialized. {@code null} value indicates
* that the returned state won't be stored, as a result previously stored state will be used.
* @see com.intellij.util.xmlb.XmlSerializer
*/
@Nullable
T getState();
/**
* This method is called when new component state is loaded. The method can and will be called several times, if
* config files were externally changed while IDEA running.
* @param state loaded component state
* @see com.intellij.util.xmlb.XmlSerializerUtil#copyBean(Object, Object)
*/
void loadState(T state);
/**
* This method is called when component is initialized but no state is persisted.
*/
default void noStateLoaded() {
}
}