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package org.glassfish.appclient.server.core.jws;
import java.util.HashMap;
import java.util.Map;
/**
* Models the state (and transitions) related to Java Web Start support of
* app clients for a given client.
*
* As an app is enabled, disabled, suspended, or resumed, the state of
* how Java Web Start should respond is different. What transitions are
* permitted in each state is also enforced.
*
* Implementation note: I tried recording the valid transitions (action plus
* new state) as part of the state value definitions themselves in the enum.
* This did not seem to work; in any {@link Transition} values for earlier
* states, references to states defined later in the enum were null! It's
* probably a little cleaner design to keep the states and the set of valid
* transitions separate from each other anyway.
*
* @author tjquinn
*/
public class JavaWebStartState {
/**
* Records a transition to the new state that is implied by the current
* state and the specified action,
* executing the associated task as part of the transition (if the
* transition is valid).
*
* The specified action must match a valid transition from the
* current state.
*
* @param action the Action the server is notifying us about
* @param task the work to perform
*/
public void transition(final Action action, final Runnable task) {
final Transition t = validTransitions.get(currentStateValue).get(action);
if (t == null) {
throw new IllegalStateException(currentStateValue.toString() + " : " + action.toString());
}
final StateValue newStateValue = t.newStateValue;
if (task != null && ! t.isNOOP) {
task.run();
}
currentStateValue = newStateValue;
}
/**
* Reports whether the state represents a "running" condition.
* @return
*/
public boolean isRunning() {
return currentStateValue == StateValue.RUNNING;
}
/**
* Reports whether the state represents a "suspended" condition.
* @return
*/
public boolean isSuspended() {
return currentStateValue == StateValue.SUSPENDED;
}
/**
* Possible states
*/
private enum StateValue {
STOPPED, RUNNING, SUSPENDED
}
/**
* Possible actions the server can tell us about.
*/
public enum Action {
START, STOP, SUSPEND, RESUME
}
/**
* Records a valid transition given an action to a new state.
*/
private static class Transition {
final Action action;
final StateValue newStateValue;
final boolean isNOOP;
Transition(final Action action, final StateValue newState) {
this(action, newState, false);
}
Transition(final Action action, final StateValue newState, final boolean isNOOP) {
super();
this.action = action;
this.newStateValue = newState;
this.isNOOP = isNOOP;
}
}
private StateValue currentStateValue = StateValue.STOPPED;
/** the valid transitions for this state engine */
private final Map> validTransitions = initValidTransitions();
/**
* Legal state transitions:
*
* Action Transition From To start STOPPED RUNNING stop RUNNING
SUSPENDED
STOPPED(no-op) STOPPED suspend RUNNING
SUSPENDED(no-op) SUSPENDED resume SUSPENDED RUNNING
*
*/
private Map> initValidTransitions() {
final Map> result = new HashMap>();
addTransitionSet(result, StateValue.STOPPED,
new Transition(Action.START, StateValue.RUNNING),
new Transition(Action.STOP, StateValue.STOPPED, true /* is NOOP */));
addTransitionSet(result, StateValue.RUNNING,
new Transition(Action.STOP, StateValue.STOPPED),
new Transition(Action.SUSPEND, StateValue.SUSPENDED));
addTransitionSet(result, StateValue.SUSPENDED,
new Transition(Action.RESUME, StateValue.RUNNING),
new Transition(Action.SUSPEND, StateValue.SUSPENDED, true /* is NOOP */));
return result;
}
private void addTransitionSet(final Map> map, StateValue originalState, Transition... transitions) {
Map transitionsForState = map.get(originalState);
if (transitionsForState == null) {
transitionsForState = new HashMap();
map.put(originalState, transitionsForState);
}
for (Transition t : transitions) {
transitionsForState.put(t.action, t);
}
}
}