Category Archives: Java/Java EE

eclipse neon – removing redundant types in java 7 diamond operators

Posted on by
Reply

I’m really excited that Neon comes with a feature to remove the redundant types that haven’t been needed since Java 7. For example, List<String> list = new ArrayList<String>(); vs List<String> list = new ArrayList<>(); We have the diamond operator, but there hasn’t been any easy way that I know of for dealing with the old code.

How to use it

I wanted to run JUST this rule so my commit doesn’t have other things in it. (I like to run these rules one at a time). Here’s what I did:

  1. Select project
  2. Source > Cleanup
  3. Use custom profile
  4. Configure
  5. Uncheck box on member access tab
  6. Uncheck box on missing code tab
  7. Uncheck all boxes on unnecessary code tab
  8. Check box for Remove redundant type arguments (1.7 or higher)
  9. Ok
  10. Finish
  11. Wait about 30 seconds
  12. Sync with repository
  13. Spot check three classes – all good!
  14. Commit the 202 files that had changes in it
  15. Enjoy the cleaner code 🙂

mongrel tomcat launcher not working on neon

Posted on by
2

Edit: The solution is here

I used to use sydeo to launch Tomcat and then switched to Mongrel which I’ve been using for a few years. I had trouble with Mongrel in Eclipse Neon.

Symptoms

  • Clicking Start – get pop up with “The chosen operation is not available” and “Plugin net.sf.mongrel.plugin was unable to load class net.sf.mongrel.actions.StartActionDelegate” in the Eclipse log
  • Clicking Restart – get pop up with “The chosen operation is not available” and “Plugin net.sf.mongrel.plugin was unable to load class net.sf.mongrel.actions.RestartActionDelegate” in the Eclipse log
  • Clicking Stop – get pop up with “The chosen operation is not available” and “Plugin net.sf.mongrel.plugin was unable to load class net.sf.mongrel.actions.StopActionDelegate” in the Eclipse log
  • Opening Mongrel in the Eclipse preferences – get “An error has occurred while creating this preference page” and “Unable to create the selected preference page. An error occurred while automatically activating bundle net.sf.mongrel.plugin (1288).” The full Eclipse message in the error log is at the bottom of this post.

Attempt at solving

I checked the update site from Marketplace (by pasting the update site into “install new software” into Eclipse) and saw that there is only one version of Mongrel available. So it isn’t that I’m not using the latest version. I also tried uninstalling Mongrel and re-installing it. Nope. (You can uninstall a plugin through Marketplace if you installed it that way). Nothing.

I also learned I’m not the only one with this problem.

Workaround

The workaround is to use the WTP (web tool plugin) that comes with Eclipse as described here. Not a big deal. I just like the single button approach. I had upgraded to Java 8 since I last used WTP so I immediately got “unable to start Tomcat” with this log message in the console:

java.lang.UnsupportedClassVersionError: com/javaranch/jforum/csrf/CsrfListener : Unsupported major.minor version 52.0 (unable to load class com.javaranch.jforum.csrf.CsrfListener)

It was immediately obvious to me that WTP was pointing to Java 7 since I successfully launched this project in Mars a few days ago. I clicked on “runtime” in the Tomcat profile and choose Java 8 from the pull down. This updated the classpath and then I was successful.

Full message in case curious

eclipse.buildId=4.6.0.I20160606-1100

java.version=1.8.0_45

java.vendor=Oracle Corporation

BootLoader constants: OS=macosx, ARCH=x86_64, WS=cocoa, NL=en_US

Framework arguments:  -product org.eclipse.epp.package.jee.product -product org.eclipse.epp.package.jee.product -product org.eclipse.epp.package.jee.product -keyring /Users/nyjeanne/.eclipse_keyring

Command-line arguments:  -os macosx -ws cocoa -arch x86_64 -product org.eclipse.epp.package.jee.product -product org.eclipse.epp.package.jee.product -data file:/Users/nyjeanne/Documents/workspace/ -product org.eclipse.epp.package.jee.product -keyring /Users/nyjeanne/.eclipse_keyring

org.eclipse.equinox.registry

Error

Fri Jun 24 10:48:29 EDT 2016

Unable to create the selected preference page.

java.lang.ClassNotFoundException: An error occurred while automatically activating bundle net.sf.mongrel.plugin (975).

at org.eclipse.osgi.internal.hooks.EclipseLazyStarter.postFindLocalClass(EclipseLazyStarter.java:116)

at org.eclipse.osgi.internal.loader.classpath.ClasspathManager.findLocalClass(ClasspathManager.java:529)

at org.eclipse.osgi.internal.loader.ModuleClassLoader.findLocalClass(ModuleClassLoader.java:325)

at org.eclipse.osgi.internal.loader.BundleLoader.findLocalClass(BundleLoader.java:334)

at org.eclipse.osgi.internal.loader.BundleLoader.findClassInternal(BundleLoader.java:411)

at org.eclipse.osgi.internal.loader.BundleLoader.findClass(BundleLoader.java:361)

at org.eclipse.osgi.internal.loader.BundleLoader.findClass(BundleLoader.java:353)

at org.eclipse.osgi.internal.loader.ModuleClassLoader.loadClass(ModuleClassLoader.java:161)

at java.lang.ClassLoader.loadClass(ClassLoader.java:357)

at org.eclipse.osgi.internal.framework.EquinoxBundle.loadClass(EquinoxBundle.java:564)

at org.eclipse.core.internal.registry.osgi.RegistryStrategyOSGI.createExecutableExtension(RegistryStrategyOSGI.java:174)

at org.eclipse.core.internal.registry.ExtensionRegistry.createExecutableExtension(ExtensionRegistry.java:905)

at org.eclipse.core.internal.registry.ConfigurationElement.createExecutableExtension(ConfigurationElement.java:243)

at org.eclipse.core.internal.registry.ConfigurationElementHandle.createExecutableExtension(ConfigurationElementHandle.java:55)

at org.eclipse.ui.internal.WorkbenchPlugin$1.run(WorkbenchPlugin.java:291)

at org.eclipse.swt.custom.BusyIndicator.showWhile(BusyIndicator.java:70)

at org.eclipse.ui.internal.WorkbenchPlugin.createExtension(WorkbenchPlugin.java:286)

at org.eclipse.ui.internal.PluginAction.createDelegate(PluginAction.java:122)

at org.eclipse.ui.internal.PluginAction.runWithEvent(PluginAction.java:219)

at org.eclipse.ui.internal.WWinPluginAction.runWithEvent(WWinPluginAction.java:228)

at org.eclipse.jface.action.ActionContributionItem.handleWidgetSelection(ActionContributionItem.java:565)

at org.eclipse.jface.action.ActionContributionItem.lambda$5(ActionContributionItem.java:436)

at org.eclipse.jface.action.ActionContributionItem$$Lambda$34/501727405.handleEvent(Unknown Source)

at org.eclipse.swt.widgets.EventTable.sendEvent(EventTable.java:84)

at org.eclipse.swt.widgets.Display.sendEvent(Display.java:4248)

at org.eclipse.swt.widgets.Widget.sendEvent(Widget.java:1501)

at org.eclipse.swt.widgets.Widget.sendEvent(Widget.java:1524)

at org.eclipse.swt.widgets.Widget.sendEvent(Widget.java:1509)

at org.eclipse.swt.widgets.Widget.notifyListeners(Widget.java:1313)

at org.eclipse.swt.widgets.Display.runDeferredEvents(Display.java:4072)

at org.eclipse.swt.widgets.Display.readAndDispatch(Display.java:3698)

at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine$4.run(PartRenderingEngine.java:1121)

at org.eclipse.core.databinding.observable.Realm.runWithDefault(Realm.java:336)

at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine.run(PartRenderingEngine.java:1022)

at org.eclipse.e4.ui.internal.workbench.E4Workbench.createAndRunUI(E4Workbench.java:150)

at org.eclipse.ui.internal.Workbench$5.run(Workbench.java:687)

at org.eclipse.core.databinding.observable.Realm.runWithDefault(Realm.java:336)

at org.eclipse.ui.internal.Workbench.createAndRunWorkbench(Workbench.java:604)

at org.eclipse.ui.PlatformUI.createAndRunWorkbench(PlatformUI.java:148)

at org.eclipse.ui.internal.ide.application.IDEApplication.start(IDEApplication.java:138)

at org.eclipse.equinox.internal.app.EclipseAppHandle.run(EclipseAppHandle.java:196)

at org.eclipse.core.runtime.internal.adaptor.EclipseAppLauncher.runApplication(EclipseAppLauncher.java:134)

at org.eclipse.core.runtime.internal.adaptor.EclipseAppLauncher.start(EclipseAppLauncher.java:104)

at org.eclipse.core.runtime.adaptor.EclipseStarter.run(EclipseStarter.java:388)

at org.eclipse.core.runtime.adaptor.EclipseStarter.run(EclipseStarter.java:243)

at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)

at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)

at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)

at java.lang.reflect.Method.invoke(Method.java:497)

at org.eclipse.equinox.launcher.Main.invokeFramework(Main.java:673)

at org.eclipse.equinox.launcher.Main.basicRun(Main.java:610)

at org.eclipse.equinox.launcher.Main.run(Main.java:1519)

Caused by: org.osgi.framework.BundleException: Error loading bundle activator.

at org.eclipse.osgi.internal.framework.BundleContextImpl.start(BundleContextImpl.java:716)

at org.eclipse.osgi.internal.framework.EquinoxBundle.startWorker0(EquinoxBundle.java:932)

at org.eclipse.osgi.internal.framework.EquinoxBundle$EquinoxModule.startWorker(EquinoxBundle.java:309)

at org.eclipse.osgi.container.Module.doStart(Module.java:581)

at org.eclipse.osgi.container.Module.start(Module.java:449)

at org.eclipse.osgi.framework.util.SecureAction.start(SecureAction.java:470)

at org.eclipse.osgi.internal.hooks.EclipseLazyStarter.postFindLocalClass(EclipseLazyStarter.java:107)

… 51 more

Caused by: java.lang.ClassNotFoundException: org.eclipse.core.internal.compatibility.PluginActivator cannot be found by net.sf.mongrel.plugin_1.0.0.201101221622

at org.eclipse.osgi.internal.loader.BundleLoader.findClassInternal(BundleLoader.java:448)

at org.eclipse.osgi.internal.loader.BundleLoader.findClass(BundleLoader.java:361)

at org.eclipse.osgi.internal.loader.BundleLoader.findClass(BundleLoader.java:353)

at org.eclipse.osgi.internal.framework.BundleContextImpl.loadBundleActivator(BundleContextImpl.java:757)

at org.eclipse.osgi.internal.framework.BundleContextImpl.start(BundleContextImpl.java:711)

… 57 more

performance engineer’s guide to hotspot JIT compilation – monica beckwith – qcon

Posted on by
Reply

For more QCon posts, see my live blog table of contents. This presentation is about the compiler and also the runtime.

Major pieces

  • Execution engine
    • Heap management/garbage collection
    • JIT compilation
  • Runtime
    • VM Class loading
    • Interpretter
    • Byte code verification,etc

Runtime goal – convert from bytecode to native code and do optimizations along the way

Compilation Techniques and Notes

  • Pre-compiled/ahead of time
  • profile guided – based on critical hotspots
  • Adaptive optimization (Java uses Profile guided and Adaptive optimization)
  • Identify root of compilation
  • replace method or on stack – depends on number of times through loop
  • Server compiler has a higher threshold than client compiler for the threshold at which you need optimizations
  • Tiered compilation – tier 1 is client compiler with no profiling info, tier 2 and 3 are client compiler with profiling info. Then comes server compiler
  • CodeCache order of magnitude larger when tiered compilation is enabled. If need more can use -XX:ReservedCodeCacheSize
  • Inlining – many different parameters when figuring out when to inline
  • Vectorization – SIMD (SIngle Instruction Multiple Data). Can generate stubs and benefit from caching size chunks. For SuperWord Level Parallelism, you need to unroll the loop, do analysis/pre-optimization, etc. Still in infancy with Hotspot.
  • Escape analysis – Want to see if object only is used in a compile method. Need entire graph to confirm not in a static field/returned from method/passed as parameter/etc. If really local, can optimize by storing in registers.
  • Objects are 8 byte aligned by default. Fields are aligned by type.
  • OOP (ordinary object pointer) is a managed pointer. The size can be changed to optimize.
  • Compressed Class Pointers – part of the Metaspace. Class data is outside of heap.

Deoptimization

  1. dependency issues
  2. class unloading/redefinition
  3. uncommon path
  4. profiled info isn’t useful for path [like with databases when db assumes something different than you want]

If curious about details

To get information about what compiler thinks/did:

  • PrintCompilation – ex: what level instructions were compiled at
  • PrintInlining – use -XX:+UnlockDiagonsticVMOptions