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• Welcome to the Java Training Beat!

  - by tmcginn

  We are a group of dedicated training developers for Java, located in the US, India, and now Mexico. In this blog we will announce new training content and events that might be of interest to our readers. In this first installment of the Java Training Beat, I would like to introduce three new Oracle By Example (OBE) modules I recently released and posted to the Oracle Online Learning Library. Creating a Simple Java Message Service (JMS) Producer with NetBeans and GlassFish - covers how to create a simple text message producer with NetBeans 7 and GlassFish. Creating Java Message Service (JMS) Resources in WebLogic Server 12c - covers how to create JMS resources using the console and WebLogic Server 12c. With this tutorial, you can replicate the results of the first tutorial in WebLogic. Creating a Publish/Subscribe Model with Message-Driven Beans and GlassFish Server - covers how to create a publish/subscribe application using JMS. This tutorial includes a short case study that includes a JSF front-end application that sends a hotel reservation request object to the server as a MapMessage. Hope you find these useful!  And do check out the Online Learning Library - we have a wide range of additional content posted and more being added every month!

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• Question about modeling with MVC (the pattern, not the MS stuff / non web)

  - by paul

  I'm working on an application in which I'm looking to employ the MVC pattern, but I've come up against a design decision point I could use some help with. My application is going to deal with the design of state-machines. Currently the MVC model holds information about the machine's states, inputs, outputs, etc. The view is going to show a diagram for the machine, graphically allowing the user to add new states, establish transitions, and put the states in a pleasing arrangement, among other things. I would like to store part of the diagram's state (e.g. the x and y state positions) when the machine information is stored for later retrieval, and am wondering how best to go about structuring the model(s?) for this. It seems like this UI information is more closely related to the view than to the state-machine model, so I was thinking that a secondary model might be in order, but I am reluctant to pursue this route because of the added complexity. Adding this information to the current model doesn't seem the right way to go about it either. This is the my first time using the MVC pattern so I'm still figuring things out. Any input would be appreciated.

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• Which version management design methodology to be used in a Dependent System nodes?

  - by actiononmail

  This is my first question so please indicate if my question is too vague and not understandable. My question is more related to High Level Design. We have a system (specifically an ATCA Chassis) configured in a Star Topology, having Master Node (MN) and other sub-ordinate nodes(SN). All nodes are connected via Ethernet and shall run on Linux OS with other proprietary applications. I have to build a recovery Framework Design so that any software entity, whether its Linux, Ramdisk or application can be rollback to previous good versions if something bad happens. Thus I think of maintaining a State Version Matrix over MN, where each State(1,2....n) represents Good Kernel, Ramdisk and application versions for each SN. It may happen that one SN version can dependent on other SN's version. Please see following diagram:- So I am in dilemma whether to use Package Management Methodology used by Debian Distributions (Like Ubuntu) or GIT repository methodology; in order to do a Rollback to previous good versions on either one SN or on all the dependent SNs. The method should also be easier for upgrading SNs along with MNs. Some of the features which I am trying to achieve:- 1) Upgrade of even single software entity is achievable without hindering others. 2) Dependency checks must be done before applying rollback or upgrade on each of the SN 3) User Prompt should be given in case dependency fails.If User still go for rollback, all the SNs should get notification to rollback there own releases (if required). 4) The binaries should be distributed on SNs accordingly so that recovery process is faster; rather fetching every time from MN. 5) Release Patches from developer for bug fixes, feature enhancement can be applied on running system. 6) Each version can be easily tracked and distinguishable. Thanks

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• &quot;The protocol 'net.msmq' is not supported.&quot;

  - by John Breakwell

  The “Lessons Learned” blog has an update covering the error message "The protocol 'net.msmq' is not supported." "The protocol 'net.msmq' is not supported." OMG, a new lesson! Will wonders never cease? So I ran into an interesting issue setting up a WCF service to consume an MSMQ queue. I won't bother you with the details of how to actually build a WCF/MSMQ service; there are plenty of tutorials on the subject. I want to share with you an interesting error that I ran into and the surprisingly simple fix. The error occurs when attempting to generate a Service Reference or even simply browsing to the WSDL of your WCF/MSMQ service in the form of a YSOD with the following error: "The protocol 'net.msmq' is not supported." After a lot of Googling on the subject turning up plenty of questions with the same error but no answers. So I went digging into some application level config files on a server that already had a WCF/MSMQ service successfully set up by the network admin, and the answer was amazingly simple: If you are hosting an MSMQ/WCF service in IIS, you have to tell IIS to allow net.msmq protocol. It's in the advanced settings for the application or site in which you are hosting the service. .... aaaand, that's it.

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• Been doing .NET for several years and am thinking about a platform change. Where do people suggest I go?

  - by rsteckly

  Hi, I've been programming in .NET for several years now and am thinking maybe its time to do a platform switch. Any suggestions about which platform would be the best to learn? I've been thinking about going back to C++ development or just focusing on T-SQL within the Microsoft stack. I'm thinking of switching because: a) I feel that the .NET platform is increasingly becoming commodified--meaning that its more about learning a GUI and certain things to click around than really understanding programming. I'm concerned that this will lend itself to making developers on that stack increasingly paid less. b) It's very frustrating to spend your entire day essentially debugging something that should work but doesn't. Usually, Microsoft releases something that suggests anyone can just click here and there and poof there's your application. Most of the time it doesn't work and winds up sucking so much more time than it was supposed to save. c) I recently led a team in a small startup to build a WPF application. We were really hit hard with people complaining about having to download the runtime. Our code was also not portable to any other platform. Added to which, the ram usage and slowness to load of the app was remarkable for its size. I researched it and we could not find a way to optimize it. d) I'm a little concerned about being wedded to the Windows platform. What are the pros and cons of adding another platform and which platform do people suggest? Thanks!

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• Algorithms for Data Redundancy and Failover for distributed storage system?

  - by kennetham

  I'm building a distributed storage system that works with different storage sizes. For instance, my storage devices have sizes of 50GB, 70GB, 150GB, 250GB, 1000GB, 5 storage systems in one system. My application will store any files to the storage system. Question: How can I build a distributed storage with the idea of data redundancy and fail-over to store documents, videos, any type of files at the same time ensuring that should one of any storage devices fail, there would be another copy of these files on another storage device. However, the concern is, 50GB of storage can only store this maximum number of files as compared to 70GB, 150GB etc. With one storage in mind, bringing 5 storage systems like a cloud storage, is there any logical way to distribute or store the files through my application? How do I ensure data redundancy through different storage sizes? Is there any algorithm to collate multiple blob files into a single file archive? What is the best solution for one cloud storage with multiple different storage sizes? I open this topic with the objective of discussing the best way to implement this idea, assuming simplicity, what are the issues of this implementation, performance measurements and discussion of the limitations.

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• How to setup users for desktop app with SQL Azure as backend?

  - by Manuel

  I'm considering SQL Azure as DB for a new application I'm developing. The reason I want to go with Azure is because I don't want to have to maintain yet another database(s) and I want my users to be able to access the data from anywhere. The problem is that I'm not clear regarding how to users will connect. The application is a basic CRUD type of windows app. I've read that you need to add your IP to SQL Azure's firewall to connect to it, but I don't know if it's only for administration purposes only. Can anyone clarify if anyone (anywhere) can access the data with the proper credentials? Which of the following scenarios would work best (if at all)? A) Add each user to SQL Azure and have the app connect directly to Azure as if it was connecting to SQL Server B) Add an anonymous user SQL Azure and pass the real user's password/hash with every call so the Azure database can service the requests accordingly. C) Put a WCF service in between so that it handles the authentication stuff. The service will only serve the appropriate information to the user given his/her authentication and SQL Azure would be open to the service exclusively. D) - ideas are welcomed - This is confusing because all Azure examples I see are for websites. I have a hard time believing SQL Azure wouldn't handle the case of desktop apps connecting to it. So what's the best practice?

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• How to build a good service layer in ASP.NET?

  - by Swippen

  I have looked through some questions, technologies for building a good service layer but I have some questions regarding this that I need help with. First some information of what I have for requirements. We currently have a number of web applications that talk to each other in a spiderweb looking way (all talking to each other in a confusing way via webservices and database data). We want to change this so that all applications go through a service layer where we can work more with cache and encapsulate common functionality and more. We want this layer to also have a Web API so that 3rd party clients can consume information from the service. The problem I see is that if we build the service layer with say MVC4 Web API don't we need to communicate between the application using the webAPI meaning we have to construct URLs and consume JSON/Xml. That does not sound too effective. I assume a better method would be working with entities and WCF to communicate between the application but then we might loose the Web API magic? So the question is if there is a way to consume a service layer as both a Web API (JSON/XML) and as a more backend service layer with entities. If we are forced to use 2 different service layers we might have to duplicate some functionality and other bad things. Hope the question is clear enough and please ask if you need any more information.

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• Task-It Source Code

  Download Source Code I've received many questions about when the source code for the Task-It application will be released. Well, the time has finally come. I haven't been able to release this sooner due to the flurry of releases that have been coming out lately. Silverlight 4, WCF RIA Services, and even our Q1 Rad Controls. Each time I got the latest bits I ran into issues (either bugs or visual issues) in the Task-It that needed to be fixed. Having said that, the app is far from perfect. There are still some bugs lurking and things that need to be fixed up visually (especially the RadGridView filtering popup), but the main purpose of this app is to show the RadControls for Silverlight 4 in the context of a real-world application, and I don't want to keep delaying the release of the source code. Minimum requirements To run the app you will need the latest Silverlight bits. Silverlight 4 RTM, VS2010 and the ...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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• Advice on whether to use scripting, run time compile or something else

  - by Gaz83

  I work in the prodution area at my works and I design and create the software to run our automated test equipment. Everytime I get involved with a new machine I end up with a different and (hopefully) better design. Anyway I have come to the point where I feel I need to start standardization all the machines with the same program. I see a problem when it comes to applying updates as at the moment the test procedures are hard coded into the program at each station. I neeed to be able to update the core program without affecting the testing section. The way I see it that this will mean splitting the program into 2 sections. Main UI - This is the core that talks to everything on the machine such as cameras, sensors, printer etc and is a standalone application. Test Procedure - This is the steps that is executeted everytime the machine runs through a test. The main UI will load the test procedure and execute when ever a test is required. My question is what is the best approach to this in terms of having an application load a file and execute the code with in? Take into account that the code in the test procedure will need access to public methods on the UI/core system to communicate to sensors etc. I have heard about MS Roslyn and had a quick look, would this solve my issue?

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• Getting Error whileInitializing entities [closed]

  - by R76

  I am new'b as WPF Dev. I am developing Window application in WPF using mvvmlight framework. I have created database in Sqlserver compact 4.0. I have made a Ado.net Entity Data Model. When I trying to initialize the Entity object in service it throws the error like: Error 'The invocation of the constructor on type 'PointOfSale.ViewModels.ProductsViewModel' that matches the specified binding constraints threw an exception.' Line number '7' and line position '10'. stack Trace at System.Windows.Markup.XamlReader.RewrapException(Exception e, IXamlLineInfo lineInfo, Uri baseUri) at System.Windows.Markup.WpfXamlLoader.Load(XamlReader xamlReader, IXamlObjectWriterFactory writerFactory, Boolean skipJournaledProperties, Object rootObject, XamlObjectWriterSettings settings, Uri baseUri) at System.Windows.Markup.WpfXamlLoader.LoadBaml(XamlReader xamlReader, Boolean skipJournaledProperties, Object rootObject, XamlAccessLevel accessLevel, Uri baseUri) at System.Windows.Markup.XamlReader.LoadBaml(Stream stream, ParserContext parserContext, Object parent, Boolean closeStream) at System.Windows.Application.LoadComponent(Object component, Uri resourceLocator) at PointOfSale.MainWindow.InitializeComponent() in e:\VarniApplication\PointOfSale\PointOfSale\MainWindow.xaml:line 1 at PointOfSale.MainWindow..ctor() in E:\VarniApplication\PointOfSale\PointOfSale\MainWindow.xaml.cs:line 27 Inner Exception {"Unable to load the specified metadata resource."} My code: xyzEntities entites; public ctor() { entites = new xyzEntities(); //This line throws an error } I have installed sql server compact 4.0 from web installer 3.0. and added the sql server compact toolbox from the extension manager. Tell me if I am missing something to install or missing something to write code.

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• How often do you review fundamentals?

  - by mlnyc

  So I've been out of school for a year and a half now. In school, of course we covered all the fundamentals: OS, databases, programming languages (i.e. syntax, binding rules, exception handling, recursion, etc), and fundamental algorithms. the rest were more in-depth topics on things like NLP, data mining, etc. Now, a year ago if you would have told me to write a quicksort, or reverse a singly-linked list, analyze the time complexity of this 'naive' algorithm vs it's dynamic programming counterpart, etc I would have been able to give you a decent and hopefully satisfying answer. But if you would have asked me more real world questions I might have been stumped (things like how would handle logging for an application, or security difference between GET and POST, differences between SQL Server and Oracle SQL, anything I list on my resume as currently working with [jQuery questions, ColdFusion questions, ...] etc) Now, I feel things are the opposite. I haven't wrote my own sort since graduating, and I don't really have to worry much about theoretical things that do not naturally fall into problems I am trying to solve. For example, I might give you some great SQL solutions using an analytical function that I would have otherwise been stumped on or write a cool web application using angular or something but ask me to write an algo for insertAfter(Element* elem) and I might not be able to do it in a reasonable time frame. I guess my question here to the experienced programmers is how do you balance the need to both learn and experiment with new technologies (fun!), working on personal projects (also fun!) working and solving real world problems in a timeboxed environment (so I might reach out to a library that does what I want rather than re-invent the wheel so that I can focus on the problem I am trying to solve) (work, basically), and refreshing on old theoretical material which is still valid for interviews and such (can be a drag)? Do you review older material (such as famous algorithms, dynamic programming, Big-O analysis, locking implementations) regularly or just when you need it? How much time do you dedicate to both in your 'deliberate practice' and do you have a certain to-do list of topics that you want to work on?

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• From release to business

  - by geneotech

  So let's say that I've finished programming a simple, indie MMO game similiar to Tibia. I've got a stable server application that is ready to launch, i've got a tested bug-free working client application that is ready to play and the game's official website (ready to host) with payment system and client that is ready to download for free. Let's say none of them break copyright laws, and no matter how impossible it sounds, let's for now say it's true. My game divides accounts into two groups - free and premium. If someone gets premium, he's granted access to all possible game features, that of course, need server authorisation to work properly. Let's say that the "premium account" can be bought on the website for a fixed money/month. Free accounts mean that everyone can actually play, but without paying, you get limited access. This is what the mentioned payment system will be for. Well, I'm completely novice to these business entities issues, so in short: what, in terms of law, are steps from here to the state where my game earns money in a fully legal way ? Also, is there for example, something like verification if game gives the user what it actually offers when paying on its website ? I live in Europe, if it changes something.

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• Standard/Compliance for web programming?

  - by MarkusK

  I am working with developers right now that write code the way they want and when i tell them to do it other way they respond that its just matter of preference how to do it and they have their way and i have mine. I am not talking about the formatting of code, but rather of way site is organized in classes and the way the utilize them. and the way they create functions and process forms etc. Their coding does not match my standards, but again they argue that its matter of preference and as long as goal achieved the can be different way's to do it. I agree but their way is proven to have bugs and we spend a lot of time going back and forth with them to fix all problems security or functionality, yet they still write same code no matter how many times i asked them to stop doing certain things. Now i am ready to dismiss them but friend of mine told me that he has same exact problem with freelance developers he work with. So i don't want to trade one bad apple for another. Question is is there some world wide (or at least europe and usa) accepted standard or compliance on how write secure web based applications. What application architecture should be for maintainable application. Is there are some general standard that can be used for any language ruby php or java govern security and functionality and quality of code? Or at least for PHP and MySQL i use for my website. So i can make them follow this strict standard and stop making excuses.

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• Using Bulk Operations with Coherence Off-Heap Storage

  - by jpurdy

  Some NamedCache methods (including clear(), entrySet(Filter), aggregate(Filter, …), invoke(Filter, …)) may generate large intermediate results. The size of these intermediate results may result in out-of-memory exceptions on cache servers, and in some cases on cache clients. This may be particularly problematic if out-of-memory exceptions occur on more than one server (since these operations may be cluster-wide) or if these exceptions cause additional memory use on the surviving servers as they take over partitions from the failed servers. This may be particularly problematic with clusters that use off-heap storage (such as NIO or Elastic Data storage options), since these storage options allow greater than normal cache sizes but do nothing to address the size of intermediate results or final result sets. One workaround is to use a PartitionedFilter, which allows the application to break up a larger operation into a number of smaller operations, each targeting either a set of partitions (useful for reducing the load on each cache server) or a set of members (useful for managing client result set sizes). It is also possible to return a key set, and then pull in the full entries using that key set. This also allows the application to take advantage of near caching, though this may be of limited value if the result is large enough to result in near cache thrashing.

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• Apress Deal of the Day - 17/March/2011

  - by TATWORTH

  v\:* {behavior:url(#default#VML);} o\:* {behavior:url(#default#VML);} w\:* {behavior:url(#default#VML);} .shape {behavior:url(#default#VML);} Normal 0 false false false false EN-GB X-NONE X-NONE MicrosoftInternetExplorer4 /* 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:0cm 5.4pt 0cm 5.4pt; mso-para-margin:0cm; 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;} Today’s $10 Deal of the day at http://www.apress.com/info/dailydeal  is  Beginning SQL Server Modeling: Model-Driven Application Development in SQL Server 2008 Get ready for model-driven application development with SQL Server Modeling! This book covers Microsoft's SQL Server Modeling (formerly known under the code name "Oslo") in detail and contains the information you need to be successful with designing and implementing workflow modeling.

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• Lubuntu 12.10: Icon Display Problems

  - by SlcBullseye

  First off, I would like to let you know that I am new to Linux. I finally decided to give it a try and my first project was installing Lubuntu on an old PC and using it for a media server for my PS3. So, one thing that I noticed right away is that my icons for applications, files, folders, etc...are not visible. If I move my mouse over the name of the application or file (It only works if I move the mouse up from the bottom of the name) then the icon will appear, but if I move my mouse back over any other place on the file the icon will disappear again. Also, if I open a folder sometimes an icon or two will be displayed but the rest won't, and like I said before if I move my mouse over the top of the application or file the icon will disappear. Is there any way to fix this? Is this normal? Or could it be a problem with my hardware? I never had this issue when I was running the last OS (Windows XP). Any help would be greatly appreciated. Remember, I am new to Linux so a thorough explanation would be helpful. Also, if there are any tips, tricks, references, or recommendations any of you have to help me jump in and become more familiar with using Linux that would be great! I'm very interested in taking advantage of the power Linux has. Currently I am studying computer programming so maybe one day I will be able to develop my own Linux distribution.

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• Best method to implement a filtered search

  - by j0N45

  I would like to ask you, your opinion when it comes to implement a filtered search form. Let's imagine the following case: 1 Big table with lots of columns It might be important to say that this SQL Server You need to implement a form to search data in this table, and in this form you'll have several check boxes that allow you to costumize this search. Now my question here is which one of the following should be the best way to implement the search? Create a stored procedure with a query inside. This stored procedure will check if the parameters are given by the application and in the case they are not given a wildcard will be putted in the query. Create a dynamic query, that is built accordingly to what is given by the application. I am asking this because I know that SQL Server creates an execution plan when the stored procedure is created, in order to optimize its performance, however by creating a dynamic query inside of the stored procedure will we sacrifice the optimization gained by the execution plan? Please tell me what would be the best approach in your oppinion.

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• What's the benefit to learn Java programming?

  - by user30139

  I'm from the PHP world. Recently I'm trying to learn about Java. Because simply I'm a bit interested in Android development. Learning about Java gives more control about my cellphone. Say I could fine tune some applications to fit my personal requirements or even make my own ones. Still Java is a new world to me. I guess I'm already too comfortable with weak typed languages such as PHP. Honestly I think application development of no matter which kind wouldn't make too much difference. Because just as web development mostly framework based, what the developer do is to fill the blanks meaning to follow the protocols the given by the framework. Most of the code is still about business logic, that's what application development all about, right? The big difference seems to lie on the programming languages. Comparing to PHP, Java holds a whole package of constraints and practices. At this point, what are the benefits to learn programming in it?

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• How come I cannot make this file executable (chmod permissions)?

  - by bappi48

  I downloaded Android Development Tool for linux (ADT) and placed it in home directory. After unzipping the files, when I double click the "eclipse" executable file; the eclipse works perfectly fine. But If I unzip the ADT in a different directory, in my case directory E: (is shown when I boot in windows 7) There double clicking the same "eclipse" executable file does not run eclipse. It shows error message: Could not display /media/Software/00.AndroidLinux/ADT/eclipse/eclipse. There is no application installed for executable files. Do you want to search for an application to open this file? If I press yes in the Dialog, it finds "Pypar2" which is not my solution. I found that the "eclipse" file permission is following -rw------- 1 tanvir tanvir 63050 Feb 4 19:05 eclipse I tried to change the permission by "chmod +x eclipse" , but no use. This command does not change the file permission at all in this case. what should I do? Relevant output of cat /proc/mounts: /dev/sda6 /media/Software fuseblk rw,nosuid,nodev,relatime,user_id=0,group_id=0,default_permissions,allow_other,blksize=4096 0 0 Please not that I'm new to Ubuntu and still learning day by day.

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• Which topics do I need to research to enable me to complete my self-assigned "Learning Project"?

  - by Anonymous -

  I want to continue learning C#. I've read parts of a few books recommended on here and the language is feeling more familiar by the day. I'd like to tackle a mid-sized personal project to take my expertise to the next level. What I'd like to do, is create an application that 'manages expenses', that runs on multiple machines on a LAN. So for example, say we have person1 and person2 on seperate machines running the application, when person1 enters an expense, it will appear on person2's (pretty UI) view of the expenses database and vice versa. What topics do I need to research to make this possible for me? I plan on learning WPF for the UI (though the steep learning curve (or so I'm told) has me a little anxious about that at this stage. With regards to the database, which database would you recommend I use? I don't want a 'server' for the database to run on, so do I need to use an embedded database that each client machine runs a copy of that updates to each other (upon startup/entering of expense on any machine etc)? What topics under networking should I be looking at? I haven't studied networking before in any language, so do I need to learn about sockets or?

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• Serve up syntactic XHTML5 using the text/html MIME type?

  - by cboettig

  I have a site currently written with HTML5 tags. I'd like to be able to parse the site as XML, with support for namespaces, etc, to facilitate programmatic extraction of data. Currently I have <!DOCTYPE html> and <meta charset="utf-8"> Which I gather is equivalent in HTML5 to explicitly setting the content-types as <meta http-equiv="Content-Type" content="text/html; charset=utf-8" /> for my current setup. In order to serve XML it sounds like the right thing to do is <?xml version="1.0" encoding="UTF-8"?> <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd"> <html xmlns="http://www.w3.org/1999/xhtml"> Should I also change my Content-Type to <meta http-equiv="content-type" content="application/xhtml+xml; charset=iso-8859-1" /> Or is that not necessary? What is the advantage of having content-type be "application/xhtml+xml"? What is the disadvantage? (Sounds like it may break internet explorer rendering of the site? but maybe that information is out of date now?) Many thanks!

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• On Developing Web Services with Global State

  - by user74418

  I'm new to web programming. I'm more experienced and comfortable with client-side code. Recently, I've been dabbling in web programming through Python's Google App Engine. I ran into some difficulty while trying to write some simple apps for the purposes of learning, mainly involving how to maintain some kind of consistent universally-accessible state for the application. I tried to write a simple queueing management system, the kind you would expect to be used in a small clinic, or at a cafeteria. Typically, this is done with hardware. You take a number from a ticketing machine, and when your number is displayed or called you approach the counter for service. Alternatively, you could be given a small pager, which will beep or vibrate when it is your turn to receive service. The former is somewhat better in that you have an idea of how many people are still ahead of you in the queue. In this situation, the global state is the last number in queue, which needs to be updated whenever a request is made to the server. I'm not sure how to best to store and maintain this value in a GAE context. The solution I thought of was to keep the value in the Datastore, attempt to query it during a ticket request, update the value, and then re-store it with put. My problem is that I haven't figured out how to lock the resource so that other requests do not check the value while it is in the middle of being updated. I am concerned that I may end up ticket requests that have the same queue number. Also, the whole solution feels awkward to me. I was wondering if there was a more natural way to accomplish this without having to go through the Datastore. Can anyone with more experience in this domain provide some advice on how to approach the design of the above application?

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• What are the signs that a ten days debugging session will not resolve an issue? [on hold]

  - by smonff

  Ten days ago, we fixed a bug on a large application and the hot fix has created a disappearing of some data from the user point of view (side effect). Data are not deleted, but have been set to hidden status. It could be possible to get the data back, but the thing seems to be hard: we've already spent 10 days to understand and reproduce the problem (mostly with SQL queries but sometimes it is necessary to update the database to test the application logic). My questions are : is 10 days a normal amount of time for these kind of problems? should we keep on and retrieve the data or should we give up this work (so the customer-relationship person will tell these users sorry for the loss, but your data have disappeared or maybe tell nothing at all)? what can be the signs that shows that we should stop to search for how to solve this issue? Edit about the context : we are a small team(3), users are not the customers, and lost data are not about the users money, bank or vital data. This is a question from a confused developer about development methodologies and business concerns, not about how we should deal with the customers.

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• Game with changing logic

  - by rsprat

  I'm planing to develop a puzzle like mobile game (android/ios) with a different logic for each puzzle. Say, for example one puzzle could be a Rubik's cube and another one a ball maze. Many more new puzzles will appear during the life of the game, and I want the users to be able to play those new puzzles. The standard way for managing this would be through application updates. Each time a new puzzle or bunch of puzzles appear, create a new update for the app that the user can download. However, I would like to do it in a more transparent way. When a new puzzle appears, the basic info of the puzzle would be displayed in the app menu, and the user would be able to play it by just clicking it. What comes to my mind is that the app would automatically download a .dll or .jar and inject it in the application at runtime. Is that even possible? Are there any restrictions from the OS? Is there a better way for solving it? Thanks alot

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