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package com.sun.hk2.component;
import org.jvnet.hk2.annotations.RunLevel;
import org.jvnet.hk2.component.ComponentException;
import org.jvnet.hk2.component.Inhabitant;
import org.jvnet.hk2.component.InhabitantListener;
import org.jvnet.hk2.component.RunLevelException;
import org.jvnet.hk2.component.RunLevelState;
import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Method;
import java.lang.reflect.Proxy;
/**
* An inhabitant that prevents activation unless the sufficient RunLevelState
* has been scheduled.
*
* @author Jeff Trent
*/
public class RunLevelInhabitant extends EventPublishingInhabitant {
private static boolean enabled = true;
/**
* Serves as the gating runLevel state.
*/
private final int runLevel;
/**
* The RunLevelState that will gate the activation of the underlying
* inhabitant.
*/
private final RunLevelState state;
/*public*/ RunLevelInhabitant(Inhabitant delegate,
int runLevel, RunLevelState state) {
this(delegate, runLevel, state, null);
}
/*public*/ RunLevelInhabitant(Inhabitant delegate,
int runLevel, RunLevelState state,
InhabitantListener listener) {
super(delegate, listener);
this.runLevel = runLevel;
this.state = state;
}
/*
* FOR INTERNAL USE ONLY
*/
public static void enable(boolean enable) {
enabled = enable;
}
@Override
public Class type() {
boolean wasInstantiated = isActive();
try {
return super.type();
} finally {
if (isActive() != wasInstantiated) {
// if we were inadvertently activated, better perform a latent check
verifyState();
}
}
}
@SuppressWarnings("rawtypes")
@Override
public T get(Inhabitant onBehalfOf) {
verifyState();
return super.get(onBehalfOf);
}
@Override
public U getByType(Class type) {
if (isStrict()) {
if (type.isInterface()) {
// try to activate to ensure a predictable activation order between dependant services
attemptToActivate();
return (U) Proxy.newProxyInstance(type.getClassLoader(), new Class[]{type},
new InvocationHandler() {
@Override
public Object invoke(Object proxy, Method method, Object[] objects)
throws Throwable {
if (isActive()) {
Object o = get();
return o == null ? null : method.invoke(o, objects);
}
throw new RunLevelException(getFailedActivationMessage(
getPlannedRunLevel(), getCurrentRunLevel()));
}
});
}
throw new RunLevelException("can't create proxy of type "
+ type + " for " + this );
}
return super.getByType(type);
}
/**
* Verifies that the state of the RunLevelService is appropriate for this
* instance activation.
*
* @throws ComponentException if not in an appropriate state for activation
*/
protected void verifyState() throws ComponentException {
if (enabled && !isActive()){
Integer planned = getPlannedRunLevel();
Integer current = getCurrentRunLevel();
if (!isValidActiveState(planned, current)) {
throw new RunLevelException(getFailedActivationMessage(planned, current));
}
}
}
/**
* Attempt to activate this instance. First check that the state of
* the RunLevelService is appropriate for this instance activation.
*/
private void attemptToActivate() {
if (isValidActiveState(getPlannedRunLevel(), getCurrentRunLevel())) {
get();
}
}
/**
* Determine whether or not the state of the RunLevelService is appropriate
* for this instance activation with the given planned/current run levels.
*
* @param planned the planned run level
* @param current the current run level
*
* @return true if the state of the RunLevelService is appropriate for
* this instance activation
*/
private boolean isValidActiveState(Integer planned, Integer current) {
return !isStrict() ||
((runLevel <= planned) && (runLevel <= (current + 1)));
}
/**
* Get the text for a failed activation of the run level service.
*
* @param planned the planned run level
* @param current the current run level
*
* @return the message
*/
private String getFailedActivationMessage(Integer planned, Integer current) {
return "unable to activate " + this +
"; minimum expected RunLevel is: " + runLevel +
"; planned is: " + planned +
"; current is: " + current;
}
/**
* Check whether the strict constraint rules should be followed.
*
* @return true if strict constraint rules should be followed
*/
private boolean isStrict() {
RunLevel rl = type().getAnnotation(RunLevel.class);
return rl == null || rl.strict();
}
/**
* Get the planned run level from the associated run level state.
*
* @return the planned run level
*/
private Integer getPlannedRunLevel() {
Integer planned = state.getPlannedRunLevel();
return planned == null ? RunLevel.KERNEL_RUNLEVEL : planned;
}
/**
* Get the current run level of the associated run level state.
*
* @return the current run level
*/
private Integer getCurrentRunLevel() {
Integer current = state.getCurrentRunLevel();
return current == null ? RunLevel.KERNEL_RUNLEVEL : current;
}
/**
* Get the run level state that is associated with this inhabitant.
*
* @return the run level state.
*/
public RunLevelState getState() {
return state;
}
}
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