[FIXED JENKINS-36494] Switch to a try with resources form of impersonation

core/src/main/java/hudson/WebAppMain.java

@@ -23,6 +23,7 @@
  */
 package hudson;
 
+import hudson.security.ACLContext;
 import jenkins.util.SystemProperties;
 import com.thoughtworks.xstream.converters.reflection.PureJavaReflectionProvider;
 import com.thoughtworks.xstream.core.JVM;
@@ -59,7 +60,6 @@ import javax.xml.transform.TransformerFactoryConfigurationError;
 import java.io.File;
 import java.io.FileOutputStream;
 import java.io.IOException;
-import java.lang.reflect.Method;
 import java.net.URL;
 import java.net.URLClassLoader;
 import java.util.Date;
@@ -370,25 +370,20 @@ public class WebAppMain implements ServletContextListener {
     }
 
     public void contextDestroyed(ServletContextEvent event) {
-        try {
-            ACL.impersonate(ACL.SYSTEM, new Runnable() {
-                @Override
-                public void run() {
-                    terminated = true;
-                    Jenkins instance = Jenkins.getInstanceOrNull();
-                    if (instance != null)
-                        instance.cleanUp();
-                    Thread t = initThread;
-                    if (t != null && t.isAlive()) {
-                        LOGGER.log(Level.INFO, "Shutting down a Jenkins instance that was still starting up", new Throwable("reason"));
-                        t.interrupt();
-                    }
+        try (ACLContext old = ACL.as(ACL.SYSTEM)) {
+            terminated = true;
+            Jenkins instance = Jenkins.getInstanceOrNull();
+            if (instance != null)
+                instance.cleanUp();
+            Thread t = initThread;
+            if (t != null && t.isAlive()) {
+                LOGGER.log(Level.INFO, "Shutting down a Jenkins instance that was still starting up", new Throwable("reason"));
+                t.interrupt();
+            }
 
-                    // Logger is in the system classloader, so if we don't do this
-                    // the whole web app will never be undepoyed.
-                    Logger.getLogger("").removeHandler(handler);
-                }
-            });
+            // Logger is in the system classloader, so if we don't do this
+            // the whole web app will never be undepoyed.
+            Logger.getLogger("").removeHandler(handler);
         } finally {
             JenkinsJVMAccess._setJenkinsJVM(false);
         }