org.springframework.statemachine.ensemble.StateMachineEnsemble.java Source code

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/*
 * Copyright 2015-2016 the original author or authors.
 *
 * 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
 *
 * https://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 org.springframework.statemachine.ensemble;

import org.springframework.statemachine.StateMachine;
import org.springframework.statemachine.StateMachineContext;

/**
 * {@code StateMachineEnsemble} is a contract between a {@link StateMachine} and
 * arbitrary ensemble of other {@link StateMachine}s.
 *
 * @author Janne Valkealahti
 *
 * @param <S> the type of state
 * @param <E> the type of event
 */
public interface StateMachineEnsemble<S, E> {

    /**
     * Request a join to a state machine ensemble. This method
     * is a request to join an ensemble and doesn't guarantee
     * a requester will eventually successfully join. Join operation
     * needs to be used together with {@link EnsembleListener} and
     * {@link EnsembleListener#stateMachineJoined(StateMachine, StateMachineContext)}
     * is called with a {@link StateMachine} instance for successful join.
     *
     * @param stateMachine the state machine
     */
    void join(StateMachine<S, E> stateMachine);

    /**
     * Request a leave from an ensemble. This method is a request to
     * leave an ensemble. After this method is called no further processing
     * is done for a instance of {@link StateMachine}. Additionally
     * {@link EnsembleListener#stateMachineLeft(StateMachine, StateMachineContext)}
     * is called when leave request is fully processed.
     *
     * @param stateMachine the state machine
     */
    void leave(StateMachine<S, E> stateMachine);

    /**
     * Adds the ensemble listener.
     *
     * @param listener the listener
     */
    void addEnsembleListener(EnsembleListener<S, E> listener);

    /**
     * Removes the ensemble listener.
     *
     * @param listener the listener
     */
    void removeEnsembleListener(EnsembleListener<S, E> listener);

    /**
     * Sets the state as a {@link StateMachineContext}.
     *
     * @param context the state machine context
     */
    void setState(StateMachineContext<S, E> context);

    /**
     * Gets the state as a {@link StateMachineContext}.
     *
     * @return the state machine context
     */
    StateMachineContext<S, E> getState();

    /**
     * Gets the ensemble leader. If returned machine
     * is {@code NULL} it indicates that this ensemble
     * doesn't know any leader.
     *
     * @return the ensemble leader
     */
    StateMachine<S, E> getLeader();
}