org.xins.server.EngineStateMachine Maven / Gradle / Ivy
/*
* $Id: EngineStateMachine.java,v 1.14 2010/09/29 17:21:48 agoubard Exp $
*
* See the COPYRIGHT file for redistribution and use restrictions.
*/
package org.xins.server;
import org.xins.common.MandatoryArgumentChecker;
/**
* State machine for the XINS server engine.
*
* @version $Revision: 1.14 $ $Date: 2010/09/29 17:21:48 $
* @author Ernst de Haan
*/
final class EngineStateMachine {
/**
* Lock for the _state field. This object must be locked on
* before _state may be read or changed.
*/
private final Object _stateLock;
/**
* The current state.
*/
private EngineState _state;
/**
* Constructs a new EngineStateMachine object. Initially the
* state will be {@link EngineState#INITIAL}.
*/
EngineStateMachine() {
_stateLock = new Object();
_state = EngineState.INITIAL;
}
/**
* Gets the current state.
*
* @return
* the current state, cannot be null.
*/
EngineState getState() {
synchronized (_stateLock) {
return _state;
}
}
/**
* Changes the current state.
*
* If the state change is considered invalid, then an
* {@link IllegalStateException} is thrown.
*
* @param newState
* the new state, cannot be null.
*
* @throws IllegalArgumentException
* if newState == null.
*
* @throws IllegalStateException
* if the state change is considered invalid.
*/
void setState(EngineState newState)
throws IllegalArgumentException, IllegalStateException {
// Check preconditions
MandatoryArgumentChecker.check("newState", newState);
synchronized (_stateLock) {
// Remember the current state
EngineState oldState = _state;
// Determine name of current and new state
String oldStateName = (oldState == null)
? null
: oldState.getName();
String newStateName = newState.getName();
// Short-circuit if the current equals the new state
if (oldState == newState) {
return;
// Always allow changing state to DISPOSING
} else if (oldState != EngineState.DISPOSING
&& newState == EngineState.DISPOSING) {
// The first state change should be to bootstrap the framework
} else if (oldState == EngineState.INITIAL
&& newState == EngineState.BOOTSTRAPPING_FRAMEWORK) {
// Bootstrapping the framework may fail
} else if (oldState == EngineState.BOOTSTRAPPING_FRAMEWORK
&& newState == EngineState.FRAMEWORK_BOOTSTRAP_FAILED) {
// Bootstrapping the framework can be retried
} else if (oldState == EngineState.FRAMEWORK_BOOTSTRAP_FAILED
&& newState == EngineState.BOOTSTRAPPING_FRAMEWORK) {
// Bootstrapping the framework may succeed, in which case the API
// will be constructed
} else if (oldState == EngineState.BOOTSTRAPPING_FRAMEWORK
&& newState == EngineState.CONSTRUCTING_API) {
// Construction of API may fail
} else if (oldState == EngineState.CONSTRUCTING_API
&& newState == EngineState.API_CONSTRUCTION_FAILED) {
// API construction can be retried
} else if (oldState == EngineState.API_CONSTRUCTION_FAILED
&& newState == EngineState.CONSTRUCTING_API) {
// Construction of API may succeed, in which case the API is
// bootstrapped
} else if (oldState == EngineState.CONSTRUCTING_API
&& newState == EngineState.BOOTSTRAPPING_API) {
// Bootstrapping the API may fail
} else if (oldState == EngineState.BOOTSTRAPPING_API
&& newState == EngineState.API_BOOTSTRAP_FAILED) {
// Bootstrapping the API can be retried
} else if (oldState == EngineState.API_BOOTSTRAP_FAILED
&& newState == EngineState.BOOTSTRAPPING_API) {
// If bootstrapping the API succeeds, then the next step is either to
// determine the watch interval...
} else if (oldState == EngineState.BOOTSTRAPPING_API
&& newState == EngineState.INITIALIZING_API) {
// ...or to skip that and start initializing the API
} else if (oldState == EngineState.BOOTSTRAPPING_API
&& newState == EngineState.INITIALIZING_API) {
// API initialization may fail
} else if (oldState == EngineState.INITIALIZING_API
&& newState == EngineState.API_INITIALIZATION_FAILED) {
// API initialization may be retried, but then the interval is
// determined first
} else if (oldState == EngineState.API_INITIALIZATION_FAILED
&& newState == EngineState.INITIALIZING_API) {
// API initialization may succeed, in which case the engine is ready
} else if (oldState == EngineState.INITIALIZING_API
&& newState == EngineState.READY) {
// While the servet is ready, the watch interval may be redetermined,
// which is the first step in reinitialization
} else if (oldState == EngineState.READY
&& newState == EngineState.INITIALIZING_API) {
// After disposal the state changes to the final disposed state
} else if (oldState == EngineState.DISPOSING
&& newState == EngineState.DISPOSED) {
// Otherwise the state change is not allowed, fail!
} else {
// Log error
Log.log_3101(oldStateName, newStateName);
// Throw exception
String error = "The state "
+ oldStateName
+ " cannot be followed by the state "
+ newStateName
+ '.';
throw new IllegalStateException(error);
}
// Perform the state change
_state = newState;
Log.log_3100(oldStateName, newStateName);
}
}
}