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• Why would more CPU cores on virtual machine slow compile times?

  - by Sid

  [edit#2] If anyone from VMWare can hit me up with a copy of VMWare Fusion, I'd be more than happy to do the same as a VirtualBox vs VMWare comparison. Somehow I suspect the VMWare hypervisor will be better tuned for hyperthreading (see my answer too) I'm seeing something curious. As I increase the number of cores on my Windows 7 x64 virtual machine, the overall compile time increases instead of decreasing. Compiling is usually very well suited for parallel processing as in the middle part (post dependency mapping) you can simply call a compiler instance on each of your .c/.cpp/.cs/whatever file to build partial objects for the linker to take over. So I would have imagined that compiling would actually scale very well with # of cores. But what I'm seeing is: 8 cores: 1.89 sec 4 cores: 1.33 sec 2 cores: 1.24 sec 1 core: 1.15 sec Is this simply a design artifact due to a particular vendor's hypervisor implementation (type2:virtualbox in my case) or something more pervasive across more VMs to make hypervisor implementations more simpler? With so many factors, I seem to be able to make arguments both for and against this behavior - so if someone knows more about this than me, I'd be curious to read your answer. Thanks Sid [edit:addressing comments] @MartinBeckett: Cold compiles were discarded. @MonsterTruck: Couldn't find an opensource project to compile directly. Would be great but can't screwup my dev env right now. @Mr Lister, @philosodad: Have 8 hw threads, using VirtualBox, so should be 1:1 mapping without emulation @Thorbjorn: I have 6.5GB for the VM and a smallish VS2012 project - it's quite unlikely that I'm swapping in/out trashing the page file. @All: If someone can point to an open source VS2010/VS2012 project, that might be a better community reference than my (proprietary) VS2012 project. Orchard and DNN seem to need environment tweaking to compile in VS2012. I really would like to see if someone with VMWare Fusion also sees this (for VMWare vs VirtualBox compartmentalization) Test details: Hardware: Macbook Pro Retina CPU : Core i7 @ 2.3Ghz (quad core, hyper threaded = 8 cores in windows task manager) Memory : 16 GB Disk : 256GB SSD Host OS: Mac OS X 10.8 VM type: VirtualBox 4.1.18 (type 2 hypervisor) Guest OS: Windows 7 x64 SP1 Compiler: VS2012 compiling a solution with 3 C# Azure projects Compile times measure by VS2012 plugin called 'VSCommands' All tests run 5 times, first 2 runs discarded, last 3 averaged

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• How to force a clock update using ntp?

  - by ysap

  I am running Ubuntu on an ARM based embedded system that lacks a battery backed RTC. The wake-up time is somewhere during 1970. Thus, I use the NTP service to update the time to the current time. I added the following line to /etc/rc.local file: sudo ntpdate -s time.nist.gov However, after startup, it still takes a couple of minutes until the time is updated, during which period I cannot work effectively with tar and make. How can I force a clock update at any given time? UPDATE 1: The following (thanks to Eric and Stephan) works fine from command line, but fails to update the clock when put in /etc/rc.local: $ date ; sudo service ntp stop ; sudo ntpdate -s time.nist.gov ; sudo service ntp start ; date Thu Jan 1 00:00:58 UTC 1970 * Stopping NTP server ntpd [ OK ] * Starting NTP server [ OK ] Thu Feb 14 18:52:21 UTC 2013 What am I doing wrong? UPDATE 2: I tried following the few suggestions that came in response to the 1st update, but nothing seems to actually do the job as required. Here's what I tried: Replace the server to us.pool.ntp.org Use explicit paths to the programs Remove the ntp service altogether and leave just sudo ntpdate ... in rc.local Remove the sudo from the above command in rc.local Using the above, the machine still starts at 1970. However, when doing this from command line once logged in (via ssh), the clock gets updated as soon as I invoke ntpdate. Last thing I did was to remove that from rc.local and place a call to ntpdate in my .bashrc file. This does update the clock as expected, and I get the true current time once the command prompt is available. However, this means that if the machine is turned on and no user is logged in, then the time never gets updates. I can, of course, reinstall the ntp service so at least the clock is updated within a few minutes from startup, but then we're back at square 1. So, is there a reason why placing the ntpdate command in rc.local does not perform the required task, while doing so in .bashrc works fine?

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• How employable am I as a programmer?

  - by dsimcha

  I'm currently a Ph.D. student in Biomedical Engineering with a concentration in computational biology and am starting to think about what I want to do after graduate school. I feel like I've accumulated a lot of programming skills while in grad school, but taken a very non-traditional path to learning all this stuff. I'm wondering whether I would have an easy time getting hired as a programmer and could fall back on that if I can't find a good job directly in my field, and if so whether I would qualify for a more prestigious position than "code monkey". Things I Have Going For Me Approximately 4 years of experience programming as part of my research. I believe I have a solid enough grasp of the fundamentals that I could pick up new languages and technologies pretty fast, and could demonstrate this in an interview. Good math and statistics skills. An extensive portfolio of open source work (and the knowledge that working on these projects implies): I wrote a statistics library in D, mostly from scratch. I wrote a parallelism library (parallel map, reduce, foreach, task parallelism, pipelining, etc.) that is currently in review for adoption by the D standard library. I wrote a 2D plotting library for D against the GTK Cairo backend. I currently use it for most of the figures I make for my research. I've contributed several major performance optimizations to the D garbage collector. (Most of these were low-hanging fruit, but it still shows my knowledge of low-level issues like memory management, pointers and bit twiddling.) I've contributed lots of miscellaneous bug fixes to the D standard library and could show the change logs to prove it. (This demonstrates my ability read other people's code.) Things I Have Going Against Me Most of my programming experience is in D and Python. I have very little to virtually no experience in the more established, "enterprise-y" languages like Java, C# and C++, though I have learned a decent amount about these languages from small, one-off projects and discussions about language design in the D community. In general I have absolutely no knowledge of "enterprise-y" technlogies. I've never used a framework before, possibly because most reusable code for scientific work and for D tends to call itself a "library" instead. I have virtually no formal computer science/software engineering training. Almost all of my knowledge comes from talking to programming geek friends, reading blogs, forums, StackOverflow, etc. I have zero professional experience with the official title of "developer", "software engineer", or something similar.

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• What could be the best way to generalize data from Facebook and Twitter?

  - by Sjaak van der Heide

  I am not sure if this is the best subsite to ask this question, but I'm pretty sure it doesn't fit on the normal or facebook SO page... I've been asked to make a general API for connecting to several Social Media platforms (at the moment Facebook and Twitter). I have already realised both of them seperately. Meaning I retrieve the data I need from both Facebook and Twitter and hold the data in it's own dataclass. In my case a list of FacebookTimelineItems and a list of TwitterTimelineItems. now the hard part is taking the parts that are used in both (username, id, message and such) and make 1 general class that is eventually passed on to who/whatever sent the call to my API. these are two pics of the data classes I have: http://imageshack.us/photo/my-images/703/facebookdata.png/ http://imageshack.us/photo/my-images/204/twitterdata.png/ probably not 100% correct but it gives an idea what it looks like. Now I've been having several idea about how to go about and generalize the two, which is harder then I thought at first. Create an interface (TimelineItem) and let the other classes extend that one. this way I'll always be sure I have a class that contains at least the basic info I need. downside is that deserializing the JSON seems to be a nightmare. Use the two dataclasses I have and combine them into a new class afterwards, then pass that one back to whoever requested it. This would probably work but I get the idea it's not the best way to tackle this problem, and is pretty dodgy IF I get it working. Or, in case of the other two being nearly impossible. Keep the two seperated in the front end, and go sit in the corner crying because I've just figured out you can't lump together facebook and twitter... Note: I don't have to make the front end part (view), I just make sure the Model is nicely filled with data :) I hope I placed this in the right section, if I didn't I apologise and would like to know where I should go with my question. Thanks in advance for any replied/ideas/opinions on this.

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• Cron job running successfully suddenly reports script is not found

  - by Ted B

  What might cause cron to suddenly report a file it is supposed to run is "not found," when the file hasn't been touched, and in fact, the entire system hasn't been touched since it last ran successfully? I have a cronjob schedule I define by doing sudo crontab -e In it, I have dozens of cron jobs that run successfully.. I do not have a PATH specified, and I use absolute paths to call all my scheduled scripts, setting the PATH in them as needed. I do not specify a SHELL in the crontab. All scripts identify the shell as their first line. Without me touching the system, a particular job defined in the middle of other jobs will suddenly stop running. To debug this, I added an output redirection to a log file. In that, the output clearly shows the output of the script successfully running time after time for weeks, and then suddenly the following appears: /bin/sh: /home/iupress/bin/sync-email_images: not found /bin/sh: /home/iupress/bin/sync-email_images: not found /bin/sh: /home/iupress/bin/sync-email_images: not found /bin/sh: /home/iupress/bin/sync-email_images: not found /bin/sh: /home/iupress/bin/sync-email_images: not found /bin/sh: /home/iupress/bin/sync-email_images: not found /bin/sh: /home/iupress/bin/sync-email_images: not found /bin/sh: /home/iupress/bin/sync-email_images: not found /bin/sh: /home/iupress/bin/sync-email_images: not found If I do the ls command, copying and pasting that exact path from the error message, it clearly reports the file is still there (no surprise). Yet the log continues to report that file is "not found" until I take action. I can run the script manually and it runs just fine. If I do sudo crontab -e and save the file, the job runs on the next scheduled time, putting its output in the log, no longer reporting the script is "not found". It seems to me the contents of the script trying to be run are irrelevant since cron doesn't even process the file because it is "not found". I have a job scheduled below the one that is encountering this problem that I know is continuing to run, because I have its output mailed to me. So I know cron is running and continues to run at least one other job, even after it suddenly reports this job's script is "not found". All my lines end with a newline. I had no periods in the crontab until I added the redirection to a log file. I have now added a PATH specification, but left the absolute paths in the jobs. Unfortunately, I have no idea if and when this problem will occur. It will likely be weeks from now. By the way, I am running a script to syncronize the clock, and I see the time is exactly what it should be.

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• Paranoid management, contractor checking work [closed]

  - by user833345

  Just wanted to get some opinions and experiences on an issue I'm having at work. First, a little background. I've been working at a company for some time (past any probation periods) and rewriting a horrendous system. No tests, incomplete and broken functionality everywhere, enough copypasta to feed a small village, redundant code, more unused SQL tables than used ones and terrible performance. I've never seen such bad code, pretty much all of it is worthy of being posted on TheDailyWTF. The company has been operating for a number of years and have had a string of bad developers working on this system. I made a call on rewriting instead of refactoring since I judged it to be less work overall and decided that the result will address the requirements more appropriately, since the central requirement is to have a future-proof system for the next decade with plenty of room to scale up. Refactoring would have entailed untangling a huge ball of yarn and at the same time integrating it with a proper foundation or building a foundation from scratch. I've introduced the latest spiffy framework, unit & functional testing, CI, a bug tracker and agile workflow to the environment. I've fixed most of the performance issues of the old system (there were no indexes on any of the tables, for example). I've created an automated deployment process for the old system. The CTO has been maintaining the old system while I have been building the new one and he has been advising management that everything is being done as per best practices. However, management is hiring a contractor to come in and verify my work. In my experience, this is unprecedented. I can understand their reasoning to an extent, since they've had bad luck in the past, but can't help but feel somewhat offended at the fact that they distrust two senior developers who have been working with them for some time enough that a third party is being brought in. And it's not just me who is under watch - people's emails are constantly checked, someone had a remote desktop application installed on their computer of which I was asked to check the usage logs to try to determine if they were stealing sensitive data and there are CCTV cameras in one of the rooms. It's the first time I've decided to disable my Skype history at work. Am I right to feel indignant here? Has anyone else ever encountered such a situation? If so, how did it work out in the end? Was it worth sticking around? Should I just find another job?

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• Changing Silverlight application themes at runtime

  We have received a lot of questions how can the application theme be changed at run time. The most important thing here to mark is that each time the application theme is changed all the controls should be re-drawn. Without going into too much detail, we could explain the application themes as a mechanism to replace the content of the Generic.xaml file in every loaded Telerik assembly at runtime. This does not affect the controls that already have default style applied, hence the need to create new instances. Because in the Silverlight applications the RootVisual cannot be changed at run time, we need a way to reset the application UI. The following code is in App.xaml.cs. private void Application_Startup(object sender, StartupEventArgs e)     {           // Before:           // this.RootVisual = new MainPage();            this.RootVisual = new Grid();         this.ResetRootVisual();     }        public void ResetRootVisual()     {         var rootVisual = Application.Current.RootVisual as Grid;         rootVisual.Children.Clear();         rootVisual.Children.Add(new MainPage());     }   In Application_Startup() instead of creating new MainPage UserControl instance as RootVisual, we create a new Grid panel, that will contain the MainPage UserControl. In the ResetRootVisual() method we create the instance of MainPage and add it to the RootVisual panel. Then we have to create a method in the code behind which will set StyleManager.ApplicationTheme and then will call the ResetRootVisual() method: private void ChangeApplicationTheme(Theme theme) {     StyleManager.ApplicationTheme = theme;     (Application.Current as App).ResetRootVisual(); }   Here you can find an example which illustrates the described implementation of a Silverlight theme. For more information please refer to Teleriks online demos for Silverlight, the demos for WPF and help documentation for WPF and help documentation for Silverlight. Did you know that DotNetSlackers also publishes .net articles written by top known .net Authors? We already have over 80 articles in several categories including Silverlight. Take a look: here.

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• Indefinite loops where the first time is different

  - by George T

  This isn't a serious problem or anything someone has asked me to do, just a seemingly simple thing that I came up with as a mental exercise but has stumped me and which I feel that I should know the answer to already. There may be a duplicate but I didn't manage to find one. Suppose that someone asked you to write a piece of code that asks the user to enter a number and, every time the number they entered is not zero, says "Error" and asks again. When they enter zero it stops. In other words, the code keeps asking for a number and repeats until zero is entered. In each iteration except the first one it also prints "Error". The simplest way I can think of to do that would be something like the folloing pseudocode: int number = 0; do { if(number != 0) { print("Error"); } print("Enter number"); number = getInput(); }while(number != 0); While that does what it's supposed to, I personally don't like that there's repeating code (you test number != 0 twice) -something that should generally be avoided. One way to avoid this would be something like this: int number = 0; while(true) { print("Enter number"); number = getInput(); if(number == 0) { break; } else { print("Error"); } } But what I don't like in this one is "while(true)", another thing to avoid. The only other way I can think of includes one more thing to avoid: labels and gotos: int number = 0; goto question; error: print("Error"); question: print("Enter number"); number = getInput(); if(number != 0) { goto error; } Another solution would be to have an extra variable to test whether you should say "Error" or not but this is wasted memory. Is there a way to do this without doing something that's generally thought of as a bad practice (repeating code, a theoretically endless loop or the use of goto)? I understand that something like this would never be complex enough that the first way would be a problem (you'd generally call a function to validate input) but I'm curious to know if there's a way I haven't thought of.

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• dpkg crashing while trying to install a package

  - by Jonathan

  While attempting to install a package via apt-get the following. The first error I get is: E: dpkg was interrupted, you must manually run 'sudo dpkg --configure -a' to correct the problem. And, if I run that command the box spins out of control and I get the following in /var/log/syslog Aug 29 20:21:08 ip-10-202-191-4 kernel: [20571563.398546] ------------[ cut here ]------------ Aug 29 20:21:08 ip-10-202-191-4 kernel: [20571563.398552] WARNING: at /build/buildd/linux-3.0.0/arch/x86/xen/multicalls.c:182 xen_mc_flush+01c0() Aug 29 20:21:08 ip-10-202-191-4 kernel: [20571563.398561] Modules linked in: acpiphp Aug 29 20:21:08 ip-10-202-191-4 kernel: [20571563.398568] Pid: 31063, comm: java Tainted: G D W 3.0.0-14-virtual #23-Ubuntu Aug 29 20:21:08 ip-10-202-191-4 kernel: [20571563.398576] Call Trace: Aug 29 20:21:08 ip-10-202-191-4 kernel: [20571563.398580] [<c0648265>] ? printk+0x2d/0x2f Aug 29 20:21:08 ip-10-202-191-4 kernel: [20571563.398586] [<c0150462>] warn_slowpath_common+0x72/0xa0 Aug 29 20:21:08 ip-10-202-191-4 kernel: [20571563.398593] [<c0104883>] ? xen_mc_flush+0x1b3/0x1c0 Aug 29 20:21:08 ip-10-202-191-4 kernel: [20571563.398599] [<c0104883>] ? xen_mc_flush+0x1b3/0x1c0 Aug 29 20:21:08 ip-10-202-191-4 kernel: [20571563.398605] [<c01504b2>] warn_slowpath_null+0x22/0x30 Aug 29 20:21:08 ip-10-202-191-4 kernel: [20571563.398611] [<c0104883>] xen_mc_flush+0x1b3/0x1c0 Aug 29 20:21:08 ip-10-202-191-4 kernel: [20571563.398617] [<c0104e7a>] ? xen_extend_mmu_update+0x4a/0x70 Aug 29 20:21:08 ip-10-202-191-4 kernel: [20571563.398624] [<c0106565>] xen_set_pud_hyper+0x75/0x80 Aug 29 20:21:08 ip-10-202-191-4 kernel: [20571563.398630] [<c01065b9>] xen_set_pud+0x49/0x60 Aug 29 20:21:08 ip-10-202-191-4 kernel: [20571563.398636] [<c0132105>] pud_populate+0x45/0x60 Aug 29 20:21:08 ip-10-202-191-4 kernel: [20571563.398642] [<c0208a24>] __pmd_alloc+0x74/0x90 Aug 29 20:21:08 ip-10-202-191-4 kernel: [20571563.398648] [<c0208cb7>] handle_mm_fault+0x277/0x2c0 Aug 29 20:21:08 ip-10-202-191-4 kernel: [20571563.398655] [<c065f45b>] do_page_fault+0x15b/0x4a0 Aug 29 20:21:08 ip-10-202-191-4 kernel: [20571563.401923] [<c020ba24>] ? remove_vma+0x44/0x60 Aug 29 20:21:08 ip-10-202-191-4 kernel: [20571563.401923] [<c020d9b6>] ? sys_mmap_pgoff+0x106/0x1c0 Aug 29 20:21:08 ip-10-202-191-4 kernel: [20571563.401923] [<c065f300>] ? vmalloc_fault+0x190/0x190 Aug 29 20:21:08 ip-10-202-191-4 kernel: [20571563.401923] [<c065c79f>] error_code+0x67/0x6c Aug 29 20:21:08 ip-10-202-191-4 kernel: [20571563.401923] ---[ end trace 0b105e2a179ad013 ]---

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• How to Overcome or fix MIXED_DML_OPERATION error in Salesforce APEX without future method ?

  - by sathya

  How to Overcome or fix MIXED_DML_OPERATION error in Salesforce APEX without future method ?MIXED_DML_OPERATION :-one of the worst issues we have ever faced :)While trying to perform DML operation on a setup object and non-setup object in a single action you will face this error.Following are the solutions I tried and the final one worked out :-1. perform the 1st objects DML on normal apex method. Then Call the 2nd objects DML through a future method.    Drawback :- You cant get a response from the future method as its context is different and because its executing asynchronously and that its static.2. Tried the following option but it didnt work :-    1. perform the dml operation on the normal apex method.    2. tried calling the 2nd dml from trigger thinking that it would be in a different context. But it didnt work.    3. Some suggestions were given in some blogs that we could try System.runas()   Unfortunately that works only for test class.   4. Finally achieved it with response synchronously through the following solution :-    a. Created 2 apex:commandbuttons :-        1. <apex:commandButton value="Save and Send Activation Email" action="{!CreateContact}"  rerender="junkpanel" oncomplete="callSimulateUserSave()">            Note :- Oncomplete will not work if you dont have a rerender attribute. So just try refreshing a junk panel.        2. <apex:commandButton value="SimulateUserSave" id="SimulateUserSave" action="{!SaveUser}"  style="display:none;margin-left:5px;"/>        Have a junk panel as well just for rerendering  :-        <apex:outputPanel id="junkpanel"></apex:outputPanel>    b. Created this javascript function which is called from first button's oncomplete and clicks the second button :-                function callSimulateUserSave()                {                    // Specify the id of the button that needs to be clicked. This id is based on the Apex Component Hierarchy.                    // You will not get this value if you dont have the id attribute in the button which needs to be clicked from javascript                    // If you have any doubt in getting this value. Just hover over the button using Chrome developer tools to get the id.                    // But it will show like theForm:SimulateUserSave but you need to replace the colon with a dot here.                    // Note :- I have given display:none in the style of the second button to make sure that, it is not visible for the user.                    var mybtn=document.getElementById('{!$Component.theForm.SimulateUserSave}');                                    mybtn.click();                }    c. Apex Methods CreateContact and SaveUser are the pagereference methods which contains the code to create contact and user respectively.       After inserting the user inside the second apex method you can just set some public Properties in the page,        for ex:- created userid to get the user details and display in the page to show the acknowledgement to the users that the User is created.

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• Attaching two objects and changing their world matrices accordingly

  - by A-Type

  I'm having a hard time wrapping my head around the transformations required to bind two objects together in either a two-way or one-way relationship. I will need to implement both types. For the first case, I want to be able to 'couple' two ships together in space. The ships have different mass, of course. Forces applied to either ship will use combined mass and moment of inertia to calculate and move both ships. The trick is, being sure that the point at which they are coupled remains the same, and they don't move at all relative to each other. The second case is similar: I want a ship to be able to enter the atmosphere of a planet and move relative to the planet. The planet will be orbiting the sun, which is fixed at 0,0,0. Essentially, when the ship is sitting still outside of the atmosphere, the planet will move past it on its course-- but when the ship is sitting still inside the atmosphere, it moves and rotates with the planet, so that it is always relative to the horizon. Essentially, the vertices which make up the ship are now transformed just like the ones that make up the planet, except that the ship can move itself around relative to the planet. I get the feeling I can implement both of these with the same code. Essentially, I am thinking of giving each object (which I call Fixtures) a list of "slave" Fixtures onto which that Fixture's world matrix is imposed. So, this would be the planet imposing its world on any contained ships. In the case of coupling, I would simply make each ship a slave of the other, somehow. Obviously I can't just multiply the ship's world matrix by the planet's, or each ship by the others. What I'd like some help with is what calculations to make in order to get a nice, seamless relative world to the other object. I was thinking maybe I could just multiply the world of the slave by the inverse of the master, but then when you couple two ships you would lose all that world data. So, perhaps I need an intermediate "world" which is the absolute world, but use a secondary "final world" to actually transform the objects?

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• How to show pending messages using WLST?

  - by lmestre

  Here are the steps: 1. . ./setDomainEnv.sh2. java weblogic.WLST3. connect('weblogic','welcome1','t3://localhost:7001')4. domainRuntime()5. cd('ServerRuntimes/MS1/JMSRuntime/MS1.jms/JMSServers/JMSServer1/Destinations/JMSModule1!Queue1')6. cursor1=cmo.getMessages('true',9999999,10)                                                 **String(selector),Integer(timeout),Integer(state)7. msgs = cmo.getNext(cursor1, 10)                  ** This step gets 10 messages, you can call again cmo.getNext(cursor1, 10) to get the next 10 msgs8. print(msgs)My assumption, is that you had created:a. Managed Server MS1.b. JMS Server JMSServer1.c. Module called JMSModule1.d. Inside of JMSModule1, a Queue called Queue1.If you read my previous post:How to get Messages Pending Count from a Queue using WLST? https://blogs.oracle.com/LuzMestre/entry/how_to_get_messages_pendingYou can see that both are very similar.  Sometimes it is difficult to get a WLST Script sample, but you can use ls() function to know about other functionalities you don't have a sample code.***Until step 5, nothing new comparing to my previous post.5. cd('ServerRuntimes/MS1/JMSRuntime/MS1.jms/JMSServers/JMSServer1/Destinations/JMSModule1!Queue1')6. ls()You will see, MessagesPendingCount, getMessages along a lot of other functionalities available in this Queue. e.g, you can see:-r-x   getMessages                                  String : String(selector),Integer(timeout),Integer(state)Here you can check the complete MBean Reference:http://docs.oracle.com/cd/E23943_01/apirefs.1111/e13951/core/index.htmlSee JMSDestinationRuntimeMBean.Enjoy!

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• [JAVA]How to make my Oracle update/insert action through JAVA faster?

  - by gunbuster363

  [JAVA]How to make my Oracle update/insert action through JAVA faster? Hi everyone, I am facing a problem in my company that is - our program's speed is not fast enough. To be more specific, we are telecommunication company and this program handle call/internet serfing transaction made by every mobile phone users in our city. Because the amount of download content made by the iphone users is just too much, our program cannot handle them fast enough. The situation is, the amount of transaction made by users are double of the transaction processed by our program. Most of the running time of the program are dominated by DB transactions. I've search through the internet and browsed some sites ( for example: http://www.javaperformancetuning.com/tips/rawtips.shtml ) talking about java performace in DB, but I cannot find a suggestion suitable for us. these advices are not applicable/already used, for instance: 1)Use prepared statements. Use parametrized SQL Already used prepared statement. Each time will use different parameter by clear parameters and set parameters. 2)Tune the SQL to minimize the data returned (e.g. not 'SELECT *'). Sure, already used. 3)Use connection pooling. We hold a single connection during the program's execution. And I doubt that pooling cannot solve the problem because our program act as 1 user, so there are no problem for concurrent access to DB. If anyone of you think pooling is good, please tell me why. Thanks. 4)Try to combine queries and batch updates. Cannot do it. Every query/insert/update is depend on the database's information. For example, we look up the DB for the client's information, if we cannot find his usage, we insert the usage into DB, otherwise we do update. 5)Close resources (Connections, Statements, ResultSets) when finished Sure. 6)Select the fastest JDBC driver. I don't know. I've search on the internet about the type of driver available and I am very confused. We use oracle.jdbc.driver.OracleDriver and we use thin instead of oci, that's all I know. In addition, our program is a two-tier way ( java <- oracle ) 7)turn off auto-commit already done that. Looking forwards to any helps, thank you very much.

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• Traditional POS is Dead

  - by David Dorf

  Traditional POS is dead -- I've heard that one before. Here's an excerpt from Joe Skorupa's blog over at RIS where he relayed ten trends that were presented at NRF. 7. Mobile POS signals death of traditional POS. Shoppers don't love self-checkout, but they prefer it to long queues or dealing with associates. Fixed POS is expensive and bulky. Mobile POS frees floor space for other purposes and converts associates from being cashiers to being sales assistants that provide new levels of customer service and incremental basket sales. In addition to unplugging the POS, new alternatives are starting to take hold - thin client, POS as a service, and replacing POS software with e-commerce platforms. I'll grant that in some situations for some retailers there might be an opportunity to to ditch the traditional POS, but for the majority of retailers that's just not practical. Take it from a guy that had to wake up at 3am after every Thanksgiving to monitor POS systems across the US on Black Friday. If a retailer's website goes down on Black Friday, they will take a significant hit. If a retailer's chain-wide POS system goes down on Black Friday, that retailer will cease to exist. Mobile POS works great for Apple because the majority of purchases are one or two big-ticket items that don't involve cash. There's still a traditional POS in every store to fall back on (its just hidden). Try this at home: Choose your favorite e-commerce site and add an item to the cart while timing how long it takes. Now multiply that by 15 to represent the 15 items you might buy at store like Target. The user interface isn't optimized for bulk purchases, and that's how it should be. The webstore and POS are designed for different purposes. Self-checkout is a great addition to POS and so is mobile checkout. But they add capabilities to POS, not replace it. Centralized architectures, even those based in the cloud, are quite viable as long as there's resiliency in the registers. You cannot assume perfect access to the network, so a POS must always be able to sell regardless of connectivity. Clearly the different selling channels should be sharing common functionality. Things like calculating tax, accepting coupons, and processing electronic payments can be shared, usually through a service-oriented architecture. This lowers costs and providers greater consistency, both of which help retailers. On paper these technologies look really good and we should continue to push boundaries, but I'm not ready to call the patient dead just yet.

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• What is the use of Association, Aggregation and Composition (Encapsulation) in Classes

  - by SahilMahajanMj

  I have gone through lots of theories about what is encapsulation and the three techniques of implementing it, which are Association, Aggregation and Composition. What i found is, Encapsulation Encapsulation is the technique of making the fields in a class private and providing access to the fields via public methods. If a field is declared private, it cannot be accessed by anyone outside the class, thereby hiding the fields within the class. For this reason, encapsulation is also referred to as data hiding. Encapsulation can be described as a protective barrier that prevents the code and data being randomly accessed by other code defined outside the class. Access to the data and code is tightly controlled by an interface. The main benefit of encapsulation is the ability to modify our implemented code without breaking the code of others who use our code. With this feature Encapsulation gives maintainability, flexibility and extensibility to our code. Association Association is a relationship where all object have their own lifecycle and there is no owner. Let’s take an example of Teacher and Student. Multiple students can associate with single teacher and single student can associate with multiple teachers but there is no ownership between the objects and both have their own lifecycle. Both can create and delete independently. Aggregation Aggregation is a specialize form of Association where all object have their own lifecycle but there is ownership and child object can not belongs to another parent object. Let’s take an example of Department and teacher. A single teacher can not belongs to multiple departments, but if we delete the department teacher object will not destroy. We can think about “has-a” relationship. Composition Composition is again specialize form of Aggregation and we can call this as a “death” relationship. It is a strong type of Aggregation. Child object dose not have their lifecycle and if parent object deletes all child object will also be deleted. Let’s take again an example of relationship between House and rooms. House can contain multiple rooms there is no independent life of room and any room can not belongs to two different house if we delete the house room will automatically delete. The question is: Now these all are real world examples. I am looking for some description about how to use these techniques in actual class code. I mean what is the point for using three different techniques for encapsulation, How these techniques could be implemented and How to choose which technique is applicable at time.

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• Using Query Classes With NHibernate

  - by Liam McLennan

  Even when using an ORM, such as NHibernate, the developer still has to decide how to perform queries. The simplest strategy is to get access to an ISession and directly perform a query whenever you need data. The problem is that doing so spreads query logic throughout the entire application – a clear violation of the Single Responsibility Principle. A more advanced strategy is to use Eric Evan’s Repository pattern, thus isolating all query logic within the repository classes. I prefer to use Query Classes. Every query needed by the application is represented by a query class, aka a specification. To perform a query I: Instantiate a new instance of the required query class, providing any data that it needs Pass the instantiated query class to an extension method on NHibernate’s ISession type. To query my database for all people over the age of sixteen looks like this: [Test] public void QueryBySpecification() { var canDriveSpecification = new PeopleOverAgeSpecification(16); var allPeopleOfDrivingAge = session.QueryBySpecification(canDriveSpecification); } To be able to query for people over a certain age I had to create a suitable query class: public class PeopleOverAgeSpecification : Specification<Person> { private readonly int age; public PeopleOverAgeSpecification(int age) { this.age = age; } public override IQueryable<Person> Reduce(IQueryable<Person> collection) { return collection.Where(person => person.Age > age); } public override IQueryable<Person> Sort(IQueryable<Person> collection) { return collection.OrderBy(person => person.Name); } } Finally, the extension method to add QueryBySpecification to ISession: public static class SessionExtensions { public static IEnumerable<T> QueryBySpecification<T>(this ISession session, Specification<T> specification) { return specification.Fetch( specification.Sort( specification.Reduce(session.Query<T>()) ) ); } } The inspiration for this style of data access came from Ayende’s post Do You Need a Framework?. I am sick of working through multiple layers of abstraction that don’t do anything. Have you ever seen code that required a service layer to call a method on a repository, that delegated to a common repository base class that wrapped and ORMs unit of work? I can achieve the same thing with NHibernate’s ISession and a single extension method. If you’re interested you can get the full Query Classes example source from Github.

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• Zenoss Setup for Windows Servers

  - by Jay Fox

  Recently I was saddled with standing up Zenoss for our enterprise.  We're running about 1200 servers, so manually touching each box was not an option.  We use LANDesk for a lot of automated installs and patching - more about that later.The steps below may not necessarily have to be completed in this order - it's just the way I did it.STEP ONE:Setup a standard AD user.  We want to do this so there's minimal security exposure.  Call the account what ever you want "domain/zenoss" for our examples.***********************************************************STEP TWO:Make the following local groups accessible by your zenoss account.Distributed COM UsersPerformance Monitor UsersEvent Log Readers (which doesn't exist on pre-2008 machines)Here's the Powershell script I used to setup access to these local groups:# Created to add Active Directory account to local groups# Must be run from elevated prompt, with permissions on the remote machine(s).# Create txt file should contain the names of the machines that need the account added, one per line.# Script will process machines line by line.foreach($i in (gc c:\tmp\computers.txt)){# Add the user to the first group$objUser=[ADSI]("WinNT://domain/zenoss")$objGroup=[ADSI]("WinNT://$i/Distributed COM Users")$objGroup.PSBase.Invoke("Add",$objUser.PSBase.Path)# Add the user to the second group$objUser=[ADSI]("WinNT://domain/zenoss")$objGroup=[ADSI]("WinNT://$i/Performance Monitor Users")$objGroup.PSBase.Invoke("Add",$objUser.PSBase.Path)# Add the user to the third group - Group doesn't exist on < Server 2008#$objUser=[ADSI]("WinNT://domain/zenoss")#$objGroup=[ADSI]("WinNT://$i/Event Log Readers")#$objGroup.PSBase.Invoke("Add",$objUser.PSBase.Path)}**********************************************************STEP THREE:Setup security on the machines namespace so our domain/zenoss account can access itThe default namespace for zenoss is:  root/cimv2Here's the Powershell script:#Grant account defined below (line 11) access to WMI Namespace#Has to be run as account with permissions on remote machinefunction get-sid{Param ($DSIdentity)$ID = new-object System.Security.Principal.NTAccount($DSIdentity)return $ID.Translate( [System.Security.Principal.SecurityIdentifier] ).toString()}$sid = get-sid "domain\zenoss"$SDDL = "A;;CCWP;;;$sid" $DCOMSDDL = "A;;CCDCRP;;;$sid"$computers = Get-Content "c:\tmp\computers.txt"foreach ($strcomputer in $computers){    $Reg = [WMIClass]"\\$strcomputer\root\default:StdRegProv"    $DCOM = $Reg.GetBinaryValue(2147483650,"software\microsoft\ole","MachineLaunchRestriction").uValue    $security = Get-WmiObject -ComputerName $strcomputer -Namespace root/cimv2 -Class __SystemSecurity    $converter = new-object system.management.ManagementClass Win32_SecurityDescriptorHelper    $binarySD = @($null)    $result = $security.PsBase.InvokeMethod("GetSD",$binarySD)    $outsddl = $converter.BinarySDToSDDL($binarySD[0])    $outDCOMSDDL = $converter.BinarySDToSDDL($DCOM)    $newSDDL = $outsddl.SDDL += "(" + $SDDL + ")"    $newDCOMSDDL = $outDCOMSDDL.SDDL += "(" + $DCOMSDDL + ")"    $WMIbinarySD = $converter.SDDLToBinarySD($newSDDL)    $WMIconvertedPermissions = ,$WMIbinarySD.BinarySD    $DCOMbinarySD = $converter.SDDLToBinarySD($newDCOMSDDL)    $DCOMconvertedPermissions = ,$DCOMbinarySD.BinarySD    $result = $security.PsBase.InvokeMethod("SetSD",$WMIconvertedPermissions)     $result = $Reg.SetBinaryValue(2147483650,"software\microsoft\ole","MachineLaunchRestriction", $DCOMbinarySD.binarySD)}***********************************************************STEP FOUR:Get the SID for our zenoss account.Powershell#Provide AD User get SID$objUser = New-Object System.Security.Principal.NTAccount("domain", "zenoss") $strSID = $objUser.Translate([System.Security.Principal.SecurityIdentifier]) $strSID.Value******************************************************************STEP FIVE:Modify the Service Control Manager to allow access to the zenoss AD account.This command can be run from an elevated command line, or through Powershellsc sdset scmanager "D:(A;;CC;;;AU)(A;;CCLCRPRC;;;IU)(A;;CCLCRPRC;;;SU)(A;;CCLCRPWPRC;;;SY)(A;;KA;;;BA)(A;;CCLCRPRC;;;PUT_YOUR_SID_HERE_FROM STEP_FOUR)S:(AU;FA;KA;;;WD)(AU;OIIOFA;GA;;;WD)"******************************************************************In step two the script plows through a txt file that processes each computer listed on each line.  For the other scripts I ran them on each machine using LANDesk.  You can probably edit those scripts to process a text file as well.That's what got me off the ground monitoring the machines using Zenoss.  Hopefully this is helpful for you.  Watch the line breaks when copy the scripts.

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• How do we provide valid time estimates during Sprint Planning without doing "too much" design?

  - by Michael Edenfield

  My team is getting up to speed with Scrum, but most of us are more familiar with non-agile or "pseudo-"agile methodologies. The part that is the biggest hurdle for us is running an efficient Sprint Planning meeting where we break our backlog items into tasks, and estimate hours. (I'm using the terminology from the VS2010 Scrum Template; apologies if I use the wrong word somewhere.) When we try to figure out how long a task is going to take, we often fall into the trap of designing the feature at the code level -- table layout, interfaces, etc -- in order to figure out how long that's going to take. I'm pretty sure this is not the appropriate place to be doing that kind of design. We should be scheduling tasks for these design meetings during the sprint. However, we are having trouble figuring out how else to come up with meaningful estimates for the tasks. Are there any practical habits/techniques/etc. for making a judgement call about how long a feature is going to take, without knowing how you plan to implement it? If our time estimates are going to change significantly once the design has been completed, how can we properly budget our Sprint backlog ahead of time? EDIT: Just to clarify, since some of the comments/answers are very valid but I think addressing the wrong question. We know that what we're doing is not right, and that we should be building time into the sprint for this design. Conceptually all of the developers understand that. We also also bringing in a team member with Scrum experience to keep us on track if we start going off into the weeds. The problem is that, without going through this design process, we are finding it difficult to provide concrete time estimates for anything. We are constantly saying things like "well if we design it this way it might take 8 hours but if we end up having to do this other way instead that will take about 32 but it might not be as bad once we start trying to write it...". I also assume that this process will get better once we have some historical velocity to work from, but many of the technologies and architectural patterns we are using are new to us. But if potentially-wildly-wrong estimates are just a natural part of adapting this process then we will just need to recondition ourselves to accept that :)

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• JSR 355 Final Release, and moves JCP to version 2.9

  - by heathervc

  JSR 355, JCP EC Merge, passed the JCP EC Final Approval Ballot on 13 August 2012, with 14 Yes votes, 1 abstain (1 member did not vote) on the SE/EE EC, and 12 yes votes (2 members were not eligible to vote) on the ME EC.  JSR 355 posted a Final Release this week, moving the JCP program version to JCP 2.9.  The transition to a merged EC will happen after the 2012 EC Elections, as defined in the Appendix B of the JCP (pasted below), and the EC will operate under the new EC Standing Rules. In the previous version (2.8) of this Process Document there were two separate Executive Committees, one for Java ME and one for Java SE and Java EE combined. The single Executive Committee described in this version of the Process Document will be implemented through the following process: The 2012 annual elections will be held as defined in JCP 2.8, but candidates will be informed that if they are elected their term will be for only a single year, since all candidates must stand for re-election in 2013. Immediately after the 2012 election the two ECs will be merged. Oracle and IBM's second seats will be eliminated, resulting in a single EC with 30 members. All subsequent JSR ballots (even for in-progress JSRs) will then be voted on by the merged EC. For the 2013 annual elections three Ratified and two Elected Seats will be eliminated, thereby reducing the EC to 25 members. All 25 seats will be up for re-election in 2013. Members elected in 2013 will be ranked to determine whether their initial term will be one or two years. The 50% of Ratified and 50% of Elected members who receive the most votes will serve an initial two-year term, while all others will serve an initial one year term. All members elected in 2014 and subsequently will serve a two-year term. For clarity, note that the provisions specified in this version of the Process Document regarding a merged EC will apply to subsequent ballots on all existing JSRs, whether or not the Spec Leads of those JSRs chose to adopt this version of the Process Document in its entirety. <end of Appendix> Also of note:  the materials and minutes from the July EC meeting and the June EC Meeting are now available--following the July EC Meeting, Samsung and SK Telecom lost their EC seats. The June EC meeting also had a public portion--the audio from the public portion of the EC meeting are now posted online.  For Spec Leads there is also the recording of the EG Nominations call.

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• Nifty popup fails to register

  - by Snailer

  I'm new to Nifty GUI, so I'm following a tutorial here for making popups. For now, I'm just trying to get a very basic "test" popup to show, but I get multiple errors and none of them make much sense. To show a popup, I believe it is necessary to first have a Nifty Screen already showing, which I do. So here is the ScreenController for the working Nifty Screen: public class WorkingScreen extends AbstractAppState implements ScreenController { //Main is my jme SimpleApplication private Main app; private Nifty nifty; private Screen screen; public WorkingScreen() {} public void equip(String slotstr) { int slot = Integer.valueOf(slotstr); System.out.println("Equipping item in slot "+slot); //Here's where it STOPS working. app.getPlayer().registerPopupScreen(nifty); System.out.println("Registered new popup"); Element ele = nifty.createPopup(app.getPlayer().POPUP); System.out.println("popup is " +ele); nifty.showPopup(nifty.getCurrentScreen(), ele.getId(), null); } @Override public void initialize(AppStateManager stateManager, Application app) { super.initialize(stateManager, app); this.app = (Main)app; } @Override public void update(float tpf) { /** jME update loop! */ } public void bind(Nifty nifty, Screen screen) { this.nifty = nifty; this.screen = screen; } When I call equip(0) the system prints Equipping item in slot 0, then a lot of errors and none of the subsequent println()'s. Clearly it botches somewhere in Player.registerPopupScreen(Nifty nifty). Here's the method: public final String POPUP = "Test Popup"; public void registerPopupScreen(Nifty nifty) { System.out.println("Attempting new popup"); PopupBuilder b = new PopupBuilder(POPUP) {{ childLayoutCenter(); backgroundColor("#000a"); panel(new PanelBuilder() {{ id("List"); childLayoutCenter(); height(percentage(75)); width(percentage(50)); control(new ButtonBuilder("TestButton") {{ label("TestButton"); width("120px"); height("40px"); align(Align.Center); }}); }}); }}; System.out.println("PopupBuilder success."); b.registerPopup(nifty); System.out.println("Registerpopup success."); } Because that first println() doesn't show, it looks like this method isn't even called at all! Edit After removing all calls on the Player object, the popup works. It seems I'm not "allowed" to access the player from the ScreenController. Unfortunate, since I need information on the player for the popup. Is there a workaround?

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• C++ and SDL resource management for 2D game

  - by KuruptedMagi

  My first question is about stateManagers. I do not use the singleton pattern (read many random posts with various reasons not to use it), I have gameStateManager which runs the pointer cCurrentGameState-render(), etc. I want to make a transitioning game, this engine should ideally cover both a platformer and a bird's eye RPG (with some recoding, I just mean the base engine), both of which will load different levels and events, such as world map, dungeon, shops, etc. So I then thought, rather then having to store all this data within all the states, I would break the engine into gameStates, and playStates... when gameState reaches gameStatePlay(), gameStatePlay simply runs the usual handleInput, logic, and render for the playStates, just as the low level gameStateManager does. This lets me store all the player data within the base playstate class without storing useless data in the gameStates. Now I have added a seperate mapEditor, which uses editorStates from gameStateEditor. Is this too much usage of the gameState concept? It seems to work pretty well for me, so I was wondering if I am too far off a common implementation of this. My second question is on image resources. I have my sprite class with nothing but static members, mainly loadImage, applySurface, and my screen pointer. I also have a map pairing imageName enums with actual SDL_Surface pointers, and one pairing clipNumber enums with a wrapper class for a vector of clips, so that each reference in the map can have different amounts of clips with different sizes. I thought it would be better to store all these images, and screen within one static body, since 20 different goblins all use the same sprite sheet, and all need to print to the same screen, and of course, this way I do not need to pass my screen reference to every little entity. The imageMap seems to work very well, I can even add the ability to search through the map at creation of entity type to see if a particular image at creation, creating if it doesnt exist, and destroying the image if the last entity that needs it was just destroyed. The vectored clip map however, seems to take too long to initialize, so if i run past the state that initializes them to fast, the game crashes <. Plus, the clip map call is half of this line =P SPRITE::applySurface( cEditorMap.cTiles[x][y].iX, cEditorMap.cTiles[x][y].iY, SPRITE::mImages[ IMAGE_TILEMAP ], SPRITE::screen, SPRITE::mImageClips[IMAGE_TILEMAP]->clips.at( cEditorMap.cTiles[x][y].iTileType ) ); Again, do I have the right idea? I like the imageMap, but am I better off with each entity storing its own clips? My last question is about collision detection. I only grasp the basics, will look at per-pixel and circular soon, but how can I determine which side the collision comes from with just the basic square collision detection, I tried breaking each entity into 4 collision zones, but that just gave me problems with walking through walls and the like <. Also, is per-pixel color collision a good way to decide what collision just occured, or is checking multiple colors for multiple entities too taxing each cycle?

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• What is SOA ?

  - by llaszews

  First, let’s mention what SOA is not: • SOA is not the same thing as web services. Web Services implies the use of standard such as Java/JAX-RPC, .NET or REST. Web Services also implies the use of a WSDL, SOAP, and/or J2EE Connector Architecture (J2EE CA) and HTTP. SOA architectures can be implemented using J2EE CA, XML file transfer or Remote Procedural Call (RPC) over File Transfer Protocol (FTP), TCP/IP, Remote Method Invocation (RMI) or other protocols. In other words, Web Services are a very specific set of technologies. SOA is a concept and can be implemented in many different ways. Some very rudimentary, such as transfering flat files between applications. • SOA will not solve all of your problems. It will make your business more agile, increase business visibility, reduce integration costs and provide better reuse. However, if you don’t need help in these area or expect SOA to cure all of your IT problems, you are looking in the wrong place. • The concepts behind SOA are not new, but SOA is also not mature. SOA as it stands today has really only been around for 5 years. The concepts of standards based protocol handlers, predefined communication schemas and remote method invocation have been around for decades. So, what is SOA? SOA is an architectural blueprint, a way of developing applications, and a set of best practices. SOA is not an ‘out of the box’ solution you buy, install and then have up and running in a matter of months. SOA is a journey to a better way of doing business and the technology architecture to support this better way of doing business. SOA is also a broader set of technologies including more then just web services. Techologies like an Enterpirse Service Bus (ESB), Business Processs Execution Language (BPEL), message queues and Business Activity Monitoring (BAM) all are part of a SOA architecture. So, what is SOA? SOA is an architectural blueprint, a way of developing applications, and a set of best practices. SOA is not an ‘out of the box’ solution you buy, install and then have up and running in a matter of months. SOA is a journey to a better way of doing business and the technology architecture to support this better way of doing business. SOA is also a broader set of technologies including more then just web services. Techologies like an Enterpirse Service Bus (ESB), Business Processs Execution Language (BPEL), message queues and Business Activity Monitoring (BAM) all are part of a SOA architecture. Read more here: Oracle Modernization Solutions

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• Rendering My Fault Message

  - by onefloridacoder

  My coworkers setup  a nice way to get the fault messages from our service layer all the way back to the client’s service proxy layer.  This is what I needed to work on this afternoon.  Through a series of trials and errors I finally figured this out. The confusion was how I was looking at the exception in the quick watch viewer.  It appeared as though the EventArgs from the service call had somehow magically been cast back to FaultException(), not FaultException<T>.  I drilled into the EventArgs object with the quick watch and I copied this code to figure out where the Fault message was hiding.  Further, when I copied this quick watch code into the IDE I got squigglies.  Poop. 1: ((System 2: .ServiceModel 3: .FaultException<UnhandledExceptionFault>)(((System.Exception)(e.Result)).InnerException)).Detail.FaultMessage I wont bore you with the details but here’s how it turned out.   EventArgs which I’m calling “e” is not the result such as some collection of items you’re expecting.  It’s actually a FaultException, or in my case FaultException<T>.  Below is the calling code and the callback to handle the expected response or the fault from the completed event. 1: public void BeginRetrieveItems(Action<ObservableCollection<Model.Widget>> FindItemsCompleteCallback, Model.WidgetLocation location) 2: { 3: var proxy = new MyServiceContractClient(); 4:  5: proxy.RetrieveWidgetsCompleted += (s, e) => FindWidgetsCompleteCallback(FindWidgetsCompleted(e)); 6:  7: RetrieveWidgetsRequest request = new RetrieveWidgetsRequest { location.Id }; 8:  9: proxy.RetrieveWidgetsAsync(request); 10: } 11:  12: private ObservableCollection<Model.Widget> FindItemsCompleted(RetrieveWidgetsCompletedEventArgs e) 13: { 14: if (e.Error is FaultException<UnhandledExceptionFault>) 15: { 16: var fault = (FaultException<UnhandledExceptionFault>)e.Error; 17: var faultDetailMessage = fault.Detail.FaultMessage; 18:  19: UIMessageControlDuJour.Show(faultDetailMessage); 20: return new ObservableCollection<BinInventoryItemCountInfo>(); 21: } 22:  23: var widgets = new ObservableCollection<Model.Widget>(); 24:  25: if (e.Result.Widgets != null) 26: { 27: e.Result.Widgets.ToList().ForEach(w => widgets.Add(this.WidgetMapper.Map(w))); 28: } 29:  30: return widgets; 31: }

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• Creating Asynchronous Methods in EJB 3.1

  - by cindo

  Normal 0 false false false EN-US X-NONE X-NONE /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-qformat:yes; mso-style-parent:""; mso-padding-alt:0in 5.4pt 0in 5.4pt; mso-para-margin:0in; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:11.0pt; font-family:"Calibri","sans-serif"; mso-ascii-font-family:Calibri; mso-ascii-theme-font:minor-latin; mso-fareast-font-family:"Times New Roman"; mso-fareast-theme-font:minor-fareast; mso-hansi-font-family:Calibri; mso-hansi-theme-font:minor-latin; mso-bidi-font-family:"Times New Roman"; mso-bidi-theme-font:minor-bidi;} OBE of the Month: Creating Asynchronous Methods in EJB 3.1 This OBE covers creating an EJB 3.1 application that demonstrates the use of the @Asynchronous annotation in an Enterprise Java Bean (EJB) class or specific method. In this tutorial, you will create a Java EE 6 Web Application and add the following components to it - a Stateless Session Bean with two asynchronous methods. You define a Servlet to call the asynchronous methods and to keep track of the invocation and completion times to demonstrate the asynchronous nature of the method calls. The index.jsp will contain a form with a submit button, Run allowing you to execute the application. The form will submit to the Servlet which invokes the asynchronous methods defined in the session bean and the response is re-directed to response.jsp. Information about the asynchronous handling procedure is displayed to users. From this information, users will notice that the invoker thread and the called asynchronous thread are working concurrently. Check out this new OBE on the Oracle Learning Library: Creating Asynchronous Methods in EJB 3.1. This OBE is part of the new EJB 3.1 New Features Series. Related OBE’s that might interest you: Creating a No-Interface View Session Bean and Packaging in a WAR File Creating and Accessing a Session Bean in a  Web Application

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• WHERE x = @x OR @x IS NULL

  - by steveh99999

  Every SQL DBA and developer should read the blog of MVP Erland Sommarskog – but particularly  his article on dynamic search conditions in T-SQL. I’ve linked above to his SQL 2005 article but his 2008 version is also a must-read. I seem to regularly come across uses of the SQL in the title above… Erland’s article explains in detail why this is inefficient, but I came across a nice example recently… A stored procedure contained the following code :- WHERE @Name is null or [Name] like @Name as a nonclustered index exists on the Name column, you might assume this would be handled efficiently by SQL Server. However, I got the following output from SET STATISTICS IO Table 'xxxxx'. Scan count 15, logical reads 47760, physical reads 9, read-ahead reads 13872, lob logical reads 0, lob physical reads 0, lob read-ahead reads 0. Note the high number of logical reads… After a bit of investigation, we found that @Name could never actually be set to NULL in this particular example. ie the @x IS NULL was spurious… So, we changed the call to WHERE  [Name] like @Name Now, how much more efficient is this code ? Table 'xxxxx'. Scan count 3, logical reads 24, physical reads 0, read-ahead reads 0, lob logical reads 0, lob physical reads 0, lob read-ahead reads 0 A nice easy win in this case…… a full index scan has been replaced by a significantly more efficient index seek. I managed to recreate the same behaviour on Adventureworks – here’s a quick query to demonstrate :- USE adventureworks SET STATISTICS IO ON DECLARE @id INT = 51721 SELECT * FROM Sales.SalesOrderDetail WHERE @id IS NULL OR salesorderid = @id SELECT * FROM Sales.SalesOrderDetail WHERE salesorderid = @id Take a look at the STATISTICS IO output and compare the actual query plans used to prove the impact of  WHERE @id IS NULL. And just to follow some of Erland’s advice – here’s how you could get similar performance if it was possible that @id could actually sometimes contain NULL. DECLARE @sql NVARCHAR(4000), @parameterlist NVARCHAR(4000) DECLARE @id INT = 51721 – or change to NULL to prove query is functionally correct SET @sql = 'SELECT * FROM Sales.SalesOrderDetail WHERE 1 = 1' IF @id IS NOT NULL SET @sql = @sql + ' AND salesorderid = @id' IF @id IS NULL SET @sql = @sql + ' AND salesorderid IS NULL' SET @parameterlist = '@id INT' EXEC sp_executesql @sql, @parameterlist,@id Sometimes I think we focus too much on hardware and SQL Server configuration – when really the answer is focus on writing efficient SQL.

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