Null safety of Trigger.timer.

A botched startup (say by an error in InitializerFinder) can cause log to be filled with junk like:
Sep 20, 2012 1:10:50 PM hudson.ExtensionFinder$GuiceFinder instantiate
WARNING: Failed to load hudson.node_monitors.DiskSpaceMonitor
java.lang.InstantiationException: java.lang.ExceptionInInitializerError
	at net.java.sezpoz.IndexItem.instance(IndexItem.java:193)
	at hudson.ExtensionFinder$GuiceFinder.instantiate(ExtensionFinder.java:353)
	at hudson.ExtensionFinder$GuiceFinder.access$400(ExtensionFinder.java:232)
	at hudson.ExtensionFinder$GuiceFinder$SezpozModule$1.get(ExtensionFinder.java:509)
	at com.google.inject.internal.ProviderInternalFactory.provision(ProviderInternalFactory.java:84)
	at com.google.inject.internal.InternalFactoryToInitializableAdapter.provision(InternalFactoryToInitializableAdapter.java:52)
	at com.google.inject.internal.ProviderInternalFactory.circularGet(ProviderInternalFactory.java:66)
	at com.google.inject.internal.InternalFactoryToInitializableAdapter.get(InternalFactoryToInitializableAdapter.java:45)
	at com.google.inject.internal.ProviderToInternalFactoryAdapter$1.call(ProviderToInternalFactoryAdapter.java:46)
	at com.google.inject.internal.InjectorImpl.callInContext(InjectorImpl.java:1018)
	at com.google.inject.internal.ProviderToInternalFactoryAdapter.get(ProviderToInternalFactoryAdapter.java:40)
	at com.google.inject.Scopes$1$1.get(Scopes.java:59)
	at hudson.ExtensionFinder$GuiceFinder$4$1.get(ExtensionFinder.java:420)
	at com.google.inject.internal.InternalFactoryToProviderAdapter.get(InternalFactoryToProviderAdapter.java:41)
	at com.google.inject.internal.InjectorImpl$3$1.call(InjectorImpl.java:965)
	at com.google.inject.internal.InjectorImpl.callInContext(InjectorImpl.java:1011)
	at com.google.inject.internal.InjectorImpl$3.get(InjectorImpl.java:961)
	at hudson.ExtensionFinder$GuiceFinder._find(ExtensionFinder.java:389)
	at hudson.ExtensionFinder$GuiceFinder.find(ExtensionFinder.java:380)
	at hudson.ExtensionFinder._find(ExtensionFinder.java:149)
	at hudson.ClassicPluginStrategy.findComponents(ClassicPluginStrategy.java:289)
	at hudson.ExtensionList.load(ExtensionList.java:278)
	at hudson.ExtensionList.ensureLoaded(ExtensionList.java:231)
	at hudson.ExtensionList.getComponents(ExtensionList.java:149)
	at hudson.DescriptorExtensionList.load(DescriptorExtensionList.java:182)
	at hudson.ExtensionList.ensureLoaded(ExtensionList.java:231)
	at hudson.ExtensionList.size(ExtensionList.java:157)
	at java.util.AbstractCollection.isEmpty(AbstractCollection.java:86)
	at hudson.model.labels.LabelAtom.updateTransientActions(LabelAtom.java:107)
	at hudson.model.labels.LabelAtom.load(LabelAtom.java:189)
	at jenkins.model.Jenkins.getLabelAtom(Jenkins.java:1545)
	at jenkins.model.Jenkins.getSelfLabel(Jenkins.java:2422)
	at hudson.model.Node.getAssignedLabels(Node.java:240)
	at jenkins.model.Jenkins$17.run(Jenkins.java:2499)
	at org.jvnet.hudson.reactor.TaskGraphBuilder$TaskImpl.run(TaskGraphBuilder.java:146)
	at org.jvnet.hudson.reactor.Reactor.runTask(Reactor.java:259)
	at jenkins.model.Jenkins$7.runTask(Jenkins.java:875)
	at org.jvnet.hudson.reactor.Reactor$2.run(Reactor.java:187)
	at org.jvnet.hudson.reactor.Reactor$Node.run(Reactor.java:94)
	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1110)
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:603)
	at java.lang.Thread.run(Thread.java:722)
Caused by: java.lang.ExceptionInInitializerError
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:601)
	at net.java.sezpoz.IndexItem.instance(IndexItem.java:183)
	... 41 more
Caused by: java.lang.NullPointerException
	at hudson.node_monitors.AbstractNodeMonitorDescriptor.schedule(AbstractNodeMonitorDescriptor.java:73)
	at hudson.node_monitors.AbstractNodeMonitorDescriptor.<init>(AbstractNodeMonitorDescriptor.java:58)
	at hudson.node_monitors.AbstractNodeMonitorDescriptor.<init>(AbstractNodeMonitorDescriptor.java:54)
	at hudson.node_monitors.DiskSpaceMonitorDescriptor.<init>(DiskSpaceMonitorDescriptor.java:49)
	at hudson.node_monitors.DiskSpaceMonitor$1.<init>(DiskSpaceMonitor.java:62)
	at hudson.node_monitors.DiskSpaceMonitor.<clinit>(DiskSpaceMonitor.java:62)
	... 46 more

core/src/main/java/hudson/model/AperiodicWork.java

@@ -30,6 +30,7 @@ import hudson.triggers.Trigger;
 import jenkins.model.Jenkins;
 
 import java.util.Random;
+import java.util.Timer;
 import java.util.logging.Logger;
 
 
@@ -84,7 +85,10 @@ public abstract class AperiodicWork extends SafeTimerTask implements ExtensionPo
     @Override
     public final void doRun() throws Exception{
     	doAperiodicRun();
-    	Trigger.timer.schedule(getNewInstance(), getRecurrencePeriod());
+        Timer timer = Trigger.timer;
+        if (timer != null) {
+            timer.schedule(getNewInstance(), getRecurrencePeriod());
+        }
     }
     
     protected abstract void doAperiodicRun();

core/src/main/java/hudson/model/Queue.java

@@ -85,6 +85,7 @@ import java.util.List;
 import java.util.Map;
 import java.util.NoSuchElementException;
 import java.util.Set;
+import java.util.Timer;
 import java.util.TreeSet;
 import java.util.Map.Entry;
 import java.util.concurrent.atomic.AtomicInteger;
@@ -93,7 +94,6 @@ import java.util.concurrent.atomic.AtomicLong;
 import java.util.logging.Level;
 import java.util.logging.Logger;
 
-import javax.management.timer.Timer;
 import javax.servlet.ServletException;
 
 import jenkins.model.Jenkins;
@@ -1746,8 +1746,11 @@ public class Queue extends ResourceController implements Saveable {
         MaintainTask(Queue queue) {
             this.queue = new WeakReference<Queue>(queue);
 
-            long interval = 5 * Timer.ONE_SECOND;
-            Trigger.timer.schedule(this, interval, interval);
+            long interval = 5000;
+            Timer timer = Trigger.timer;
+            if (timer != null) {
+                timer.schedule(this, interval, interval);
+            }
         }
 
         protected void doRun() {

core/src/main/java/hudson/node_monitors/AbstractNodeMonitorDescriptor.java

@@ -36,6 +36,7 @@ import java.io.IOException;
 import java.util.Date;
 import java.util.HashMap;
 import java.util.Map;
+import java.util.Timer;
 import java.util.logging.Level;
 import java.util.logging.Logger;
 
@@ -70,11 +71,14 @@ public abstract class   AbstractNodeMonitorDescriptor<T> extends Descriptor<Node
     }
 
     private void schedule(long interval) {
-        Trigger.timer.scheduleAtFixedRate(new SafeTimerTask() {
-            public void doRun() {
-                triggerUpdate();
-            }
-        }, interval, interval);
+        Timer timer = Trigger.timer;
+        if (timer != null) {
+            timer.scheduleAtFixedRate(new SafeTimerTask() {
+                public void doRun() {
+                    triggerUpdate();
+                }
+            }, interval, interval);
+        }
     }
 
     /**

core/src/main/java/hudson/triggers/Trigger.java

@@ -62,6 +62,8 @@ import java.util.logging.Level;
 import java.util.logging.Logger;
 
 import antlr.ANTLRException;
+import javax.annotation.CheckForNull;
+import edu.umd.cs.findbugs.annotations.SuppressWarnings;
 
 /**
  * Triggers a {@link Build}.
@@ -278,26 +280,32 @@ public abstract class Trigger<J extends Item> implements Describable<Trigger<?>>
      *
      * If plugins want to run periodic jobs, they should implement {@link PeriodicWork}.
      */
-    public static Timer timer;
+    @SuppressWarnings("MS_SHOULD_BE_FINAL")
+    public static @CheckForNull Timer timer;
 
     @Initializer(after=JOB_LOADED)
     public static void init() {
         new DoubleLaunchChecker().schedule();
 
-        // start all PeridocWorks
-        for(PeriodicWork p : PeriodicWork.all())
-            timer.scheduleAtFixedRate(p,p.getInitialDelay(),p.getRecurrencePeriod());
-        
-        // start all AperidocWorks
-        for(AperiodicWork p : AperiodicWork.all())
-            timer.schedule(p,p.getInitialDelay());
-
-        // start monitoring nodes, although there's no hurry.
-        timer.schedule(new SafeTimerTask() {
-            public void doRun() {
-                ComputerSet.initialize();
+        Timer _timer = timer;
+        if (_timer != null) {
+            // start all PeridocWorks
+            for(PeriodicWork p : PeriodicWork.all()) {
+                _timer.scheduleAtFixedRate(p,p.getInitialDelay(),p.getRecurrencePeriod());
             }
-        }, 1000*10);
+
+            // start all AperidocWorks
+            for(AperiodicWork p : AperiodicWork.all()) {
+                _timer.schedule(p,p.getInitialDelay());
+            }
+
+            // start monitoring nodes, although there's no hurry.
+            _timer.schedule(new SafeTimerTask() {
+                public void doRun() {
+                    ComputerSet.initialize();
+                }
+            }, 1000*10);
+        }
     }
 
     /**

core/src/main/java/hudson/util/DoubleLaunchChecker.java

@@ -40,6 +40,7 @@ import java.util.logging.Logger;
 import java.util.logging.Level;
 import java.lang.management.ManagementFactory;
 import java.lang.reflect.Method;
+import java.util.Timer;
 
 /**
  * Makes sure that no other Hudson uses our <tt>JENKINS_HOME</tt> directory,
@@ -145,11 +146,14 @@ public class DoubleLaunchChecker {
     public void schedule() {
         // randomize the scheduling so that multiple Hudson instances will write at the file at different time
         long MINUTE = 1000*60;
-        Trigger.timer.schedule(new SafeTimerTask() {
-            protected void doRun() {
-                execute();
-            }
-        },(random.nextInt(30)+60)*MINUTE);
+        Timer timer = Trigger.timer;
+        if (timer != null) {
+            timer.schedule(new SafeTimerTask() {
+                protected void doRun() {
+                    execute();
+                }
+            },(random.nextInt(30)+60)*MINUTE);
+        }
     }
 
     /**

core/src/main/java/jenkins/model/Jenkins.java

@@ -727,7 +727,10 @@ public class Jenkins extends AbstractCIBase implements ModifiableTopLevelItemGro
      * @param pluginManager
      *      If non-null, use existing plugin manager.  create a new one.
      */
-    @edu.umd.cs.findbugs.annotations.SuppressWarnings("SC_START_IN_CTOR") // bug in FindBugs. It flags UDPBroadcastThread.start() call but that's for another class
+    @edu.umd.cs.findbugs.annotations.SuppressWarnings({
+        "SC_START_IN_CTOR", // bug in FindBugs. It flags UDPBroadcastThread.start() call but that's for another class
+        "ST_WRITE_TO_STATIC_FROM_INSTANCE_METHOD" // Trigger.timer
+    })
     protected Jenkins(File root, ServletContext context, PluginManager pluginManager) throws IOException, InterruptedException, ReactorException {
         long start = System.currentTimeMillis();
         
@@ -816,12 +819,15 @@ public class Jenkins extends AbstractCIBase implements ModifiableTopLevelItemGro
             }
             dnsMultiCast = new DNSMultiCast(this);
 
-            Trigger.timer.scheduleAtFixedRate(new SafeTimerTask() {
-                @Override
-                protected void doRun() throws Exception {
-                    trimLabels();
-                }
-            }, TimeUnit2.MINUTES.toMillis(5), TimeUnit2.MINUTES.toMillis(5));
+            Timer timer = Trigger.timer;
+            if (timer != null) {
+                timer.scheduleAtFixedRate(new SafeTimerTask() {
+                    @Override
+                    protected void doRun() throws Exception {
+                        trimLabels();
+                    }
+                }, TimeUnit2.MINUTES.toMillis(5), TimeUnit2.MINUTES.toMillis(5));
+            }
 
             updateComputerList();
 
@@ -2563,6 +2569,7 @@ public class Jenkins extends AbstractCIBase implements ModifiableTopLevelItemGro
     /**
      * Called to shut down the system.
      */
+    @edu.umd.cs.findbugs.annotations.SuppressWarnings("ST_WRITE_TO_STATIC_FROM_INSTANCE_METHOD")
     public void cleanUp() {
         for (ItemListener l : ItemListener.all())
             l.onBeforeShutdown();
@@ -2579,7 +2586,10 @@ public class Jenkins extends AbstractCIBase implements ModifiableTopLevelItemGro
         if(dnsMultiCast!=null)
             dnsMultiCast.close();
         interruptReloadThread();
-        Trigger.timer.cancel();
+        Timer timer = Trigger.timer;
+        if (timer != null) {
+            timer.cancel();
+        }
         // TODO: how to wait for the completion of the last job?
         Trigger.timer = null;
         if(tcpSlaveAgentListener!=null)