com.espertech.esper.runtime.client.util.AdapterStateManager Maven / Gradle / Ivy
/*
***************************************************************************************
* Copyright (C) 2006 EsperTech, Inc. All rights reserved. *
* http://www.espertech.com/esper *
* http://www.espertech.com *
* ---------------------------------------------------------------------------------- *
* The software in this package is published under the terms of the GPL license *
* a copy of which has been included with this distribution in the license.txt file. *
***************************************************************************************
*/
package com.espertech.esper.runtime.client.util;
/**
* A utility to manage the state transitions for an InputAdapter.
*/
public class AdapterStateManager {
private AdapterState state = AdapterState.OPENED;
private boolean stateTransitionsAllowed = true;
/**
* @return the state
*/
public AdapterState getState() {
return state;
}
/**
* Transition into the STARTED state (from the OPENED state).
*
* @throws IllegalStateTransitionException if the transition is not allowed
*/
public void start() throws IllegalStateTransitionException {
assertStateTransitionsAllowed();
if (state != AdapterState.OPENED) {
throw new IllegalStateTransitionException("Cannot start from the " + state + " state");
}
state = AdapterState.STARTED;
}
/**
* Transition into the OPENED state.
*
* @throws IllegalStateTransitionException if the transition isn't allowed
*/
public void stop() throws IllegalStateTransitionException {
assertStateTransitionsAllowed();
if (state != AdapterState.STARTED && state != AdapterState.PAUSED) {
throw new IllegalStateTransitionException("Cannot stop from the " + state + " state");
}
state = AdapterState.OPENED;
}
/**
* Transition into the PAUSED state.
*
* @throws IllegalStateTransitionException if the transition isn't allowed
*/
public void pause() throws IllegalStateTransitionException {
assertStateTransitionsAllowed();
if (state != AdapterState.STARTED) {
throw new IllegalStateTransitionException("Cannot pause from the " + state + " state");
}
state = AdapterState.PAUSED;
}
/**
* Transition into the STARTED state (from the PAUSED state).
*
* @throws IllegalStateTransitionException if the state transition is not allowed
*/
public void resume() throws IllegalStateTransitionException {
assertStateTransitionsAllowed();
if (state != AdapterState.PAUSED) {
throw new IllegalStateTransitionException("Cannot resume from the " + state + " state");
}
state = AdapterState.STARTED;
}
/**
* Transition into the DESTROYED state.
*
* @throws IllegalStateTransitionException if the transition isn't allowed
*/
public void destroy() throws IllegalStateTransitionException {
if (state == AdapterState.DESTROYED) {
throw new IllegalStateTransitionException("Cannot destroy from the " + state + " state");
}
state = AdapterState.DESTROYED;
}
/**
* Disallow future state changes, and throw an IllegalStateTransitionException if they
* are attempted.
*/
public void disallowStateTransitions() {
stateTransitionsAllowed = false;
}
private void assertStateTransitionsAllowed() {
if (!stateTransitionsAllowed) {
throw new IllegalStateTransitionException("State transitions have been disallowed");
}
}
}