org.springframework.statemachine.StateContext.java Source code

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Here is the source code for org.springframework.statemachine.StateContext.java

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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;

import java.util.Collection;

import org.springframework.messaging.Message;
import org.springframework.messaging.MessageHeaders;
import org.springframework.statemachine.action.Action;
import org.springframework.statemachine.guard.Guard;
import org.springframework.statemachine.state.State;
import org.springframework.statemachine.transition.Transition;

/**
 * {@code StateContext} is representing of a current context used in
 * various stages in a state machine execution. These include for example
 * {@link Transition}s, {@link Action}s and {@link Guard}s order to get access
 * to event headers and {@link ExtendedState}.
 * <p>
 * Context really is not a current state of a state machine but
 * more like a snapshot of where state machine is when this context
 * is passed to various methods.
 *
 * @author Janne Valkealahti
 *
 */
public interface StateContext<S, E> {

    /**
     * Gets the stage this context is attached.
     *
     * @return the stage
     */
    Stage getStage();

    /**
     * Gets the message associated with a context. Message may be null if transition
     * is not triggered by a signal.
     *
     * @return the message
     */
    Message<E> getMessage();

    /**
     * Gets the event associated with a context. Event may be null if transition
     * is not triggered by a signal.
     *
     * @return the event
     */
    E getEvent();

    /**
     * Gets the event message headers.
     *
     * @return the event message headers
     */
    MessageHeaders getMessageHeaders();

    /**
     * Gets the message header. If header is not a {@code String} object's
     * {@link Object#toString()} method is used to resolve a key name.
     *
     * @param header the header
     * @return the message header
     */
    Object getMessageHeader(Object header);

    /**
     * Gets the state machine extended state.
     *
     * @return the state machine extended state
     */
    ExtendedState getExtendedState();

    /**
     * Gets the transition.
     *
     * @return the transition
     */
    Transition<S, E> getTransition();

    /**
     * Gets the state machine.
     *
     * @return the state machine
     */
    StateMachine<S, E> getStateMachine();

    /**
     * Gets the source state of this context. Generally source
     * is where a state machine is coming from which may be different
     * than what the transition source is.
     *
     * @return the source state
     */
    State<S, E> getSource();

    /**
     * Gets the source states of this context. Multiple sources are
     * only valid during a context when machine is joining from multiple
     * orthogonal regions.
     *
     * @return the source state
     * @see #getSource()
     */
    Collection<State<S, E>> getSources();

    /**
     * Gets the target state of this context. Generally target
     * is where a state machine going to which may be different
     * than what the transition target is.
     *
     * @return the target state
     */
    State<S, E> getTarget();

    /**
     * Gets the target states of this context. Multiple targets are
     * only valid during a context when machine is forking into multiple
     * orthogonal regions.
     *
     * @return the target states
     * @see #getTarget()
     */
    Collection<State<S, E>> getTargets();

    /**
     * Gets the exception associated with a context.
     *
     * @return the exception
     */
    Exception getException();

    /**
     * Enumeration of possible stages context is attached.
     */
    public static enum Stage {
        EVENT_NOT_ACCEPTED, EXTENDED_STATE_CHANGED, STATE_CHANGED, STATE_ENTRY, STATE_EXIT, STATEMACHINE_ERROR, STATEMACHINE_START, STATEMACHINE_STOP, TRANSITION, TRANSITION_START, TRANSITION_END;
    }
}