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  • MVVM and service pattern

    - by alfa-alfa
    I'm building a WPF application using the MVVM pattern. Right now, my viewmodels calls the service layer to retrieve models (how is not relevant to the viewmodel) and convert them to viewmodels. I'm using constructor injection to pass the service required to the viewmodel. It's easily testable and works well for viewmodels with few dependencies, but as soon as I try to create viewModels for complex models, I have a constructor with a LOT of services injected in it (one to retrieve each dependencies and a list of all available values to bind to an itemsSource for example). I'm wondering how to handle multiple services like that and still have a viewmodel that I can unit test easily. I'm thinking of a few solutions: Creating a services singleton (IServices) containing all the available services as interfaces. Example: Services.Current.XXXService.Retrieve(), Services.Current.YYYService.Retrieve(). That way, I don't have a huge constructor with a ton of services parameters in them. Creating a facade for the services used by the viewModel and passing this object in the ctor of my viewmodel. But then, I'll have to create a facade for each of my complexe viewmodels, and it might be a bit much... What do you think is the "right" way to implement this kind of architecture ?

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  • decouple software components via nameconvention

    - by csteinmueller
    I'm currently evaluating alternatives to refactor a drivermanagement. In my multitier architecture I have Baseclass DAL.Device //my entity Interfaces BL.IDriver //handles the dataprocessing between application and device BL.IDriverCreator //creates an IDriver from a Device BL.IDriverFactory //handles the driver creation requests Every specialization of Device has a corresponding IDriver implementation and a corresponding IDriverCreator implementation. At the moment the mapping is fix via a type check within the business layer / DriverFactory. That means every new driver needs a) changing code within the DriverFactory and b) referencing the new IDriver implementation / assembly. On a customers point of view that means, every new driver, used or not, needs a complex revalidation of their hardware environment, because it's a critical process. My first inspiration was to use a caliburn micro like nameconvention see Caliburn.Micro: Xaml Made Easy BL.RestDriver BL.RestDriverCreator DAL.RestDevice After receiving the RestDevicewithin the IDriverFactory I can load all driver dlls via reflection and do a namesplitting/comparing (extracting the xx from xxDriverCreator and xxDevice) Another idea would be a custom attribute (which also leads to comparing strings). My question: is that a good approach above layer borders? If not, what would be a good approach?

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  • Implementing Explosions

    - by Xkynar
    I want to add explosions to my 2D game, but im having a hard time with the architecture. Several game elements might be responsible for explosions, like, lets say, explosive barrels and bullets (and there might be chain reactions with close barrels). The only options i can come up with are: 1 - Having an array of explosions and treat them as a game element as important as any other Pros: Having a single array which is updated and drawn with all the other game element arrays makes it more organized and simple to update, and the explosive barrels at a first glance would be easy to create, simply by passing the explosion array as a pointer to each explosive barrel constructor Cons: It might be hard for the bullets to add an explosion to the vector, since bullets are shot by a Weapon class which is located in every mob, so lets say, if i create a new enemy and add it to the enemy array, that enemy will have a weapon and functions to be able to use it, and if i want the weapon (rocket launcher in this case) to have access to the explosions array to be able to add a new one, id have to pass the explosion array as a pointer to the enemy, which would then pass it to the weapon, which would pass it to the bullets (ugly chain). Another problem I can think of is a little more weird: If im checking the collisions between explosions and barrels (so i create a chain reaction) and i detect an explosion colliding with a barrel, if i add a new explosion while im iterating the explosions java will trow an exception. So this is kinda annoying, i cant iterate through the explosions and add a new explosion, i must do it in another way... The other way which isnt really well thought yet is to just add an explosive component to every element that might explode so that when it dies, it explodes or something, but i dont have good ways on implementing this theory either Honestly i dont like either the solutions so id like to know how is it usually done by actual game developers, sorry if my problem seems trivial and dumb.

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  • What is the most effective approach to learn an unfamiliar complex program? [closed]

    - by bdroc
    Possible Duplicate: How do you dive into large code bases? I have quite a bit of experience with different programming languages and writing small and functional programs for a variety of purposes. My coding skills aren't what I have a problem with. In fact, I've written a decent web application from scratch for my startup. However, I have trouble jumping into unfamiliar applications. What's the most effective way to approach learning a new program's structure and/or architecture so that I can start attacking the code effectively? Are there useful tools for their respective languages (Python and Java are my two primary languages)? Should I be starting with just looking at function names or documentation? How do you veterans approach this problem? I find this has to be with minimal help from coworkers or contributors who are already familiar with the application and have better things to do than help me. I'd love to practice this skill in an open source project so any suggestions for starting points (maybe mildly complex) would be great too!

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  • How do OSes work on multiple CPUs? [on hold]

    - by user3691093
    Assumption: "OS es (atleast in some part) should be written in assembly.Assembly programs are CPU specefic." If so how can one os run on different CPUs ? For example: how is that I can load Ubuntu on different systems having different CPUs (like intel i3,i5,i7, amd a8,a6,etc) from the same bootable disk? Does the disk contain seporate assembly programs for each CPU? Are these CPUs 'similar' enough to run the same assembly program? Is my assumption wrong? Something else.... Thanks for responding. I tried to find out in what way are the CPUs that I mentioned 'similar'. I came across the concepts of Instruction Set Architecture and Microarchitecture of CPUs.A CPU will understand a program if it is combatible with its ISA. Even if CPUs are 'wired up' differently (different microarchitecture) , as long as the ISA implemented on top is same ,the program will work. ARM and x86 have different ISA ( that why there are 2 windows 8 versions, right?). And if an app program is written in an HLL with compilers for both platforms we will saved from wasting time writing 2 programs. Did I understand anything wrong? Are there programs that can take a compiled program as input and produce a program executable on another CPU as output? Is it possible? (Virtualisation?) 32 bit windows programs do install on 64 bit windows ,dont they? Arent 64 bit CPUs 'differerent' from 32 bit CPUs? They do get seporate OS versions, right? Is this backward combatibility achieved using programes mentioned in (3) ?

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  • Help identify the pattern for reacting on updates

    - by Mike
    There's an entity that gets updated from external sources. Update events are at random intervals. And the entity has to be processed once updated. Multiple updates may be multiplexed. In other words there's a need for the most current state of entity to be processed. There's a point of no-return during processing where the current state (and the state is consistent i.e. no partial update is made) of entity is saved somewhere else and processing goes on independently of any arriving updates. Every consequent set of updates has to trigger processing i.e. system should not forget about updates. And for each entity there should be no more than one running processing (before the point of no-return) i.e. the entity state should not be processed more than once. So what I'm looking for is a pattern to cancel current processing before the point of no return or abandon processing results if an update arrives. The main challenge is to minimize race conditions and maintain integrity. The entity sits mainly in database with some files on disk. And the system is in .NET with web-services and message queues. What comes to my mind is a database queue-like table. An arriving update inserts row in that table and the processing is launched. The processing gathers necessary data before the point of no-return and once it reaches this barrier it looks into the queue table and checks whether there're more recent updates for the entity. If there are new updates the processing simply shuts down and its data is discarded. Otherwise the processing data is persisted and it goes beyond the point of no-return. Though it looks like a solution to me it is not quite elegant and I believe this scenario may be supported by some sort of middleware. If I would use message queues for this then there's a need to access the queue API in the point of no-return to check for the existence of new messages. And this approach also lacks elegance. Is there a name for this pattern and an existing solution?

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  • How to export SQL Server data from corrupted database (with disk write error)

    - by damitamit
    IT realised there was a disk write error on our production SQL Server 2005 and hence was causing the backups to fail. By the time they had realised this the nightly backup was old, so were not able to just restore the backup on another server. The database is still running and being used constantly. However DBCC CheckDB fails. Also the SQL Server backup task fails, Copy Database fails, Export Data Wizard fails. However it seems all the data can be read from the tables (i.e using bcp etc) Another observation I have made is that the Transaction Log is nearly double the size of the Database. (Does that mean all the changes arent being written to the MDF?) What would be the best plan of attack to get the database to a state where backups are working and the data is safe? Take the database offline and use the MDF/LDF to somehow create the database on another sql server? Export the data from the database using bcp. Create the database (use the Generate Scripts function on the corrupt db to create the schema on the new db) on another sql server and use bcp again to import the data. Some other option that is the right course of action in this situation? The IT manager says the data is safe as if the server fails, the data can be restored from the mdf/ldf. I'm not sure so insisted that we start exporting the data each night as a failsafe (using bcp for example). IT are also having issues on the hardware side of things as supposedly the disk error in on a virtualized disk and can't be rebuilt like a normal raid array (or something like that). Please excuse my use of incorrect terminology and incorrect assumptions on how Sql Server operates. I'm the application developer and have been called to help (as it seems IT know less about SQL Server than I do). Many Thanks, Amit

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  • Database cluster... without Master/Slave?

    - by RadiantHex
    Hi there! I'm wondering if it is possible to have a set of SQLdb servers to which data is written and have them replicate, avoiding conflicting information. I imagine that a Master/Slave structure would be mandatory, I would like to know if a system where servers have no hierarchy could support replication. Currently I'm using MySQL, but I would be happy to move to another database if needed. Any ideas? :)

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  • Oracle TimesTen In-Memory Database Performance on SPARC T4-2

    - by Brian
    The Oracle TimesTen In-Memory Database is optimized to run on Oracle's SPARC T4 processor platforms running Oracle Solaris 11 providing unsurpassed scalability, performance, upgradability, protection of investment and return on investment. The following demonstrate the value of combining Oracle TimesTen In-Memory Database with SPARC T4 servers and Oracle Solaris 11: On a Mobile Call Processing test, the 2-socket SPARC T4-2 server outperforms: Oracle's SPARC Enterprise M4000 server (4 x 2.66 GHz SPARC64 VII+) by 34%. Oracle's SPARC T3-4 (4 x 1.65 GHz SPARC T3) by 2.7x, or 5.4x per processor. Utilizing the TimesTen Performance Throughput Benchmark (TPTBM), the SPARC T4-2 server protects investments with: 2.1x the overall performance of a 4-socket SPARC Enterprise M4000 server in read-only mode and 1.5x the performance in update-only testing. This is 4.2x more performance per processor than the SPARC64 VII+ 2.66 GHz based system. 10x more performance per processor than the SPARC T2+ 1.4 GHz server. 1.6x better performance per processor than the SPARC T3 1.65 GHz based server. In replication testing, the two socket SPARC T4-2 server is over 3x faster than the performance of a four socket SPARC Enterprise T5440 server in both asynchronous replication environment and the highly available 2-Safe replication. This testing emphasizes parallel replication between systems. Performance Landscape Mobile Call Processing Test Performance System Processor Sockets/Cores/Threads Tps SPARC T4-2 SPARC T4, 2.85 GHz 2 16 128 218,400 M4000 SPARC64 VII+, 2.66 GHz 4 16 32 162,900 SPARC T3-4 SPARC T3, 1.65 GHz 4 64 512 80,400 TimesTen Performance Throughput Benchmark (TPTBM) Read-Only System Processor Sockets/Cores/Threads Tps SPARC T3-4 SPARC T3, 1.65 GHz 4 64 512 7.9M SPARC T4-2 SPARC T4, 2.85 GHz 2 16 128 6.5M M4000 SPARC64 VII+, 2.66 GHz 4 16 32 3.1M T5440 SPARC T2+, 1.4 GHz 4 32 256 3.1M TimesTen Performance Throughput Benchmark (TPTBM) Update-Only System Processor Sockets/Cores/Threads Tps SPARC T4-2 SPARC T4, 2.85 GHz 2 16 128 547,800 M4000 SPARC64 VII+, 2.66 GHz 4 16 32 363,800 SPARC T3-4 SPARC T3, 1.65 GHz 4 64 512 240,500 TimesTen Replication Tests System Processor Sockets/Cores/Threads Asynchronous 2-Safe SPARC T4-2 SPARC T4, 2.85 GHz 2 16 128 38,024 13,701 SPARC T5440 SPARC T2+, 1.4 GHz 4 32 256 11,621 4,615 Configuration Summary Hardware Configurations: SPARC T4-2 server 2 x SPARC T4 processors, 2.85 GHz 256 GB memory 1 x 8 Gbs FC Qlogic HBA 1 x 6 Gbs SAS HBA 4 x 300 GB internal disks Sun Storage F5100 Flash Array (40 x 24 GB flash modules) 1 x Sun Fire X4275 server configured as COMSTAR head SPARC T3-4 server 4 x SPARC T3 processors, 1.6 GHz 512 GB memory 1 x 8 Gbs FC Qlogic HBA 8 x 146 GB internal disks 1 x Sun Fire X4275 server configured as COMSTAR head SPARC Enterprise M4000 server 4 x SPARC64 VII+ processors, 2.66 GHz 128 GB memory 1 x 8 Gbs FC Qlogic HBA 1 x 6 Gbs SAS HBA 2 x 146 GB internal disks Sun Storage F5100 Flash Array (40 x 24 GB flash modules) 1 x Sun Fire X4275 server configured as COMSTAR head Software Configuration: Oracle Solaris 11 11/11 Oracle TimesTen 11.2.2.4 Benchmark Descriptions TimesTen Performance Throughput BenchMark (TPTBM) is shipped with TimesTen and measures the total throughput of the system. The workload can test read-only, update-only, delete and insert operations as required. Mobile Call Processing is a customer-based workload for processing calls made by mobile phone subscribers. The workload has a mixture of read-only, update, and insert-only transactions. The peak throughput performance is measured from multiple concurrent processes executing the transactions until a peak performance is reached via saturation of the available resources. Parallel Replication tests using both asynchronous and 2-Safe replication methods. For asynchronous replication, transactions are processed in batches to maximize the throughput capabilities of the replication server and network. In 2-Safe replication, also known as no data-loss or high availability, transactions are replicated between servers immediately emphasizing low latency. For both environments, performance is measured in the number of parallel replication servers and the maximum transactions-per-second for all concurrent processes. See Also SPARC T4-2 Server oracle.com OTN Oracle TimesTen In-Memory Database oracle.com OTN Oracle Solaris oracle.com OTN Oracle Database 11g Release 2 Enterprise Edition oracle.com OTN Disclosure Statement Copyright 2012, Oracle and/or its affiliates. All rights reserved. Oracle and Java are registered trademarks of Oracle and/or its affiliates. Other names may be trademarks of their respective owners. Results as of 1 October 2012.

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  • How do I rename the Tfs_xxxConfiguration database for TFS 2010?

    - by Jaxidian
    When we installed TFS 2010, we made some poor decisions in naming our databases. I have figured out how to rename everything except for the Tfs_xxxConfiguration database. How can I get this renamed? I can only find a read-only display of the connection string to it - cannot find where to alter that connection string either directly or indirectly. I'd really prefer to not have to rebuild it from scratch... again... Thanks!

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  • how many tables can an MS SQL database hold?

    - by Peter Turner
    I've ran into this cryptic statement for SQL Server: Files Per Database 32,767. What does that mean exactly? Is there a maximum number of tables for a given version of SQL Server. We try to support SQL Server post 2005 32-bit and 64-bit. So if anyone has a handy dandy table they use to figure out how many tables they can have per DB for Microsoft SQL Servers I'd heartily appreciate seeing it.

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  • How can I synchronize one set of data with another?

    - by RenderIn
    I have an old database and a new database. The old records were converted to the new database recently. All our old applications continue to point to the old database, but the new applications point to the new database. Currently the old database is the only one being updated, so throughout the day the new database becomes out of sync. It is acceptable for the new database to be out of sync for a day, so until all our applications are pointed to the new database I just need to write a nightly cron job that will bring it up to date. I do not want to purge the new database and run the complete conversion script each night, as that would reduce uptime and would create a mess in our auditing of that table. I'm thinking about selecting all the data from the old database, converting it to the new database structure in memory, and then checking for the existence of each record before inserting it in the new database. After that's done, I'd select everything from the new database and check if it exists in the old one, and if not delete it. Is this the simplest way to do this?

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  • Sqlite3 : "Database is locked" error

    - by Miraaj
    Hi all, In my cocoa application I am maintaining a SQLite db within resources folder and trying to do some select, delete operations in it but after some time it starts giving me 'Database is locked' error. The methods which I am using for select delete operations are as follows: // method to retrieve data if (sqlite3_open([databasePath UTF8String], &database) != SQLITE_OK) { sqlite3_close(database); NSAssert(0, @"Failed to open database"); } NSLog(@"mailBodyFor:%d andFlag:%d andFlag:%@",UId,x,Ffolder); NSMutableArray *recordsToReturn = [[NSMutableArray alloc] initWithCapacity:2]; NSString *tempMsg; const char *sqlStatementNew; NSLog(@"before switch"); switch (x) { case 9: // tempMsg=[NSString stringWithFormat:@"SELECT * FROM users_messages"]; tempMsg=[NSString stringWithFormat:@"SELECT message,AttachFileOriName as oriFileName,AttachmentFileName as fileName FROM users_messages WHERE id = (select message_id from users_messages_status where id= '%d')",UId]; NSLog(@"mail body query - %@",tempMsg); break; default: break; } sqlStatementNew = [tempMsg cStringUsingEncoding:NSUTF8StringEncoding]; sqlite3_stmt *compiledStatementNew; NSLog(@"before if statement"); if(sqlite3_prepare_v2(database, sqlStatementNew, -1, &compiledStatementNew, NULL) == SQLITE_OK) { NSLog(@"the sql is finalized"); while(sqlite3_step(compiledStatementNew) == SQLITE_ROW) { NSMutableDictionary *recordDict = [[NSMutableDictionary alloc] initWithCapacity:3]; NSString *message; if((char *)sqlite3_column_text(compiledStatementNew, 0)){ message = [NSString stringWithUTF8String:(char *)sqlite3_column_text(compiledStatementNew, 0)]; } else{ message = @""; } NSLog(@"message - %@",message); NSString *oriFileName; if((char *)sqlite3_column_text(compiledStatementNew, 1)){ oriFileName = [NSString stringWithUTF8String:(char *)sqlite3_column_text(compiledStatementNew, 1)]; } else{ oriFileName = @""; } NSLog(@"oriFileName - %@",oriFileName); NSString *fileName; if((char *)sqlite3_column_text(compiledStatementNew, 2)){ fileName = [NSString stringWithUTF8String:(char *)sqlite3_column_text(compiledStatementNew, 2)]; } else{ fileName = @""; } NSLog(@"fileName - %@",fileName); [recordDict setObject:message forKey:@"message"]; [recordDict setObject:oriFileName forKey:@"oriFileName"]; [recordDict setObject:fileName forKey:@"fileName"]; [recordsToReturn addObject:recordDict]; [recordDict release]; } sqlite3_finalize(compiledStatementNew); sqlite3_close(database); NSLog(@"user messages return -%@",recordsToReturn); return recordsToReturn; } else{ NSLog(@"Error while creating retrieving mailBodyFor in messaging '%s'", sqlite3_errmsg(database)); sqlite3_close(database); } // method to delete data if (sqlite3_open([databasePath UTF8String], &database) != SQLITE_OK) { sqlite3_close(database); NSAssert(0, @"Failed to open database"); } NSString *deleteQuery = [[NSString alloc] initWithFormat:@"delete from users_messages_status where id IN(%@)",ids]; NSLog(@"users_messages_status msg deleteQuery - %@",deleteQuery); sqlite3_stmt *deleteStmnt; const char *sql = [deleteQuery cStringUsingEncoding:NSUTF8StringEncoding]; if(sqlite3_prepare_v2(database, sql, -1, &deleteStmnt, NULL) != SQLITE_OK){ NSLog(@"Error while creating delete statement. '%s'", sqlite3_errmsg(database)); } else{ NSLog(@"successful deletion from users_messages"); } if(SQLITE_DONE != sqlite3_step(deleteStmnt)){ NSLog(@"Error while deleting. '%s'", sqlite3_errmsg(database)); } sqlite3_close(database); Things are going wrong in this sequence Data is retrieved 'Database is locked' error arises on performing delete operation. When I retry to perform 1st step.. it now gives same error. Can anyone suggest me: If I am doing anything wrong or missing some check? Is there any way to unlock it when it gives locked error? Thanks, Miraaj

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  • Tales from the Trenches – Building a Real-World Silverlight Line of Business Application

    - by dwahlin
    There's rarely a boring day working in the world of software development. Part of the fun associated with being a developer is that change is guaranteed and the more you learn about a particular technology the more you realize there's always a different or better way to perform a task. I've had the opportunity to work on several different real-world Silverlight Line of Business (LOB) applications over the past few years and wanted to put together a list of some of the key things I've learned as well as key problems I've encountered and resolved. There are several different topics I could cover related to "lessons learned" (some of them were more painful than others) but I'll keep it to 5 items for this post and cover additional lessons learned in the future. The topics discussed were put together for a TechEd talk: Pick a Pattern and Stick To It Data Binding and Nested Controls Notify Users of Successes (and failures) Get an Agent – A Service Agent Extend Existing Controls The first topic covered relates to architecture best practices and how the MVVM pattern can save you time in the long run. When I was first introduced to MVVM I thought it was a lot of work for very little payoff. I've since learned (the hard way in some cases) that my initial impressions were dead wrong and that my criticisms of the pattern were generally caused by doing things the wrong way. In addition to MVVM pros the slides and sample app below also jump into data binding tricks in nested control scenarios and discuss how animations and media can be used to enhance LOB applications in subtle ways. Finally, a discussion of creating a re-usable service agent to interact with backend services is discussed as well as how existing controls make good candidates for customization. I tried to keep the samples simple while still covering the topics as much as possible so if you’re new to Silverlight you should definitely be able to follow along with a little study and practice. I’d recommend starting with the SilverlightDemos.View project, moving to the SilverlightDemos.ViewModels project and then going to the SilverlightDemos.ServiceAgents project. All of the backend “Model” code can be found in the SilverlightDemos.Web project. Custom controls used in the app can be found in the SivlerlightDemos.Controls project.   Sample Code and Slides

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  • Windows Azure Use Case: Infrastructure Limits

    - by BuckWoody
    This is one in a series of posts on when and where to use a distributed architecture design in your organization's computing needs. You can find the main post here: http://blogs.msdn.com/b/buckwoody/archive/2011/01/18/windows-azure-and-sql-azure-use-cases.aspx  Description: Physical hardware components take up room, use electricity, create heat and therefore need cooling, and require wiring and special storage units. all of these requirements cost money to rent at a data-center or to build out at a local facility. In some cases, this can be a catalyst for evaluating options to remove this infrastructure requirement entirely by moving to a distributed computing environment. Implementation: There are three main options for moving to a distributed computing environment. Infrastructure as a Service (IaaS) The first option is simply to virtualize the current hardware and move the VM’s to a provider. You can do this with Microsoft’s Hyper-V product or other software, build the systems and host them locally on fewer physical machines. This is a good option for canned-applications (where you have to type setup.exe) but not as useful for custom applications, as you still have to license and patch those servers, and there are hard limits on the VM sizes. Software as a Service (SaaS) If there is already software available that does what you need, it may make sense to simply purchase not only the software license but the use of it on the vendor’s servers. Microsoft’s Exchange Online is an example of simply using an offering from a vendor on their servers. If you do not need a great deal of customization, have no interest in owning or extending the source code, and need to implement a solution quickly, this is a good choice. Platform as a Service (PaaS) If you do need to write software for your environment, your next choice is a Platform as a Service such as Windows Azure. In this case you no longer manager physical or even virtual servers. You start at the code and data level of control and responsibility, and your focus is more on the design and maintenance of the application itself. In this case you own the source code and can extend or change it as you see fit. An interesting side-benefit to using Windows Azure as a PaaS is that the Application Fabric component allows a hybrid approach, which gives you a basis to allow on-premise applications to leverage distributed computing paradigms. No one solution fits every situation. It’s common to see organizations pick a mixture of on-premise, IaaS, SaaS and PaaS components. In fact, that’s a great advantage to this form of computing - choice. References: 5 Enterprise steps for adopting a Platform as a Service: http://blogs.msdn.com/b/davidmcg/archive/2010/12/02/5-enterprise-steps-for-adopting-a-platform-as-a-service.aspx?wa=wsignin1.0  Application Patterns for the Cloud: http://blogs.msdn.com/b/kashif/archive/2010/08/07/application-patterns-for-the-cloud.aspx

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  • Should I be using a JavaScript SPA designed when security is important

    - by ryanzec
    I asked something kind of similar on stackoverflow with a particular piece of code however I want to try to ask this in a broader sense. So I have this web application that I have started to write in backbone using a Single Page Architecture (SPA) however I am starting to second guess myself because of security. Now we are not storing and sending credit card information or anything like that through this web application but we are storing sensitive information that people are uploading to us and will have the ability to re-download too. The obviously security concern that I have with JavaScript is that you can't trust anything that comes from JavaScript however in a Backbone SPA application, everything is being sent through JavaScript. There are two security features that I will have to build in JavaScript; permissions and authentication. The authentication piece is just me override the Backbone.Router.prototype.navigate method to check the fragment it is trying to load and if the JavaScript application.session.loggedIn is not set to true (and they are not viewing a none authenticated page), they are redirected to the login page automatically. The user could easily modify application.session.loggedIn to equal true (or modify Backbone.Router.prototype.navigate method) but then they would also have to not so easily dynamically embedded a link into the page (or modify a current one) that has the proper classes, data-* attributes, and href values to then load a page that should only be loaded when they user has logged in (and has the permissions). So I have an acl object that deals with the permissions stuff. All someone would have to do to view pages or parts of pages they should not be able to is to call acl.addPermission(resource, permission) with the proper permissions or modify the acl.hasPermission() to always return true and then navigate away and then back to the page. Now certain things is EMCAScript 5 like Object.seal() or Object.freeze() would help with some of this however we have to support IE 8 which does not support those pieces of functionality. Now the REST API also performs security checks on every request so technically even if they are able to see parts of the interface that they should not be able to, they still should not be able to actually affect any data. The main benefits for me in developing a JavaScript SPA application is that the application is a lot more responsive since it is only transferring the minimum amount of JSON data for the requested action and performing the minimum amount of work too. There are also other things that I think are beneficial like you are going to have to develop an API for the data (which is good if you want expand your application to different platforms/technologies) or their is more of a separation between front-end and back-end however if security is a concern, it is really wise to go down the road of a JavaScript SPA application for the front-end?

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  • Characteristics of a Web service that promote reusability and change

    Characteristics of a Web service that promote reusability and change:  Standardized Data Exchange Formats (XML, JSON) Standardized communication protocols (Soap, Rest) Promotes Loosely Coupled Systems  Standardized Data Exchange Formats (XML, JSON) XML W3.org defines Extensible Markup Language (XML) as a simplistic text format derived from SGML. XML was designed to solve challenges found in large-scale electronic publishing. In addition,  XML is playing an important role in the exchange of data primarily focusing on data exchange on the web. JSON JavaScript Object Notation (JSON) is a human-readable text-based standard designed for data interchange. This format is used for serializing and transmitting data over a network connection in a structured format. The primary use of JSON is to transmit data between a server and web application. JSON is an alternative to XML. Standardized communication protocols (Soap, Rest) Soap W3Scools.com defines SOAP as a simple XML-based protocol. This protocol lets applications exchange data over HTTP.  SOAP provides a way to communicate between applications running on different operating systems, with different technologies and programming languages. Rest In 2007, Stefan Tilkov defines Representational State Transfer (REST) as a set of principles that outlines how Web standards are supposed to be used.  Using REST in an application will ensure that it exploits the Web’s architecture to its benefit. Promotes Loosely Coupled Systems “Loose coupling as an approach to interconnecting the components in a system or network so that those components, also called elements, depend on each other to the least extent practicable. Coupling refers to the degree of direct knowledge that one element has of another.” (TechTarget.com, 2007) “Loosely coupled system can be easily broken down into definable elements. The extent of coupling in a system can be measured by mapping the maximum number of element changes that can occur without adverse effects. Examples of such changes include adding elements, removing elements, renaming elements, reconfiguring elements, modifying internal element characteristics and rearranging the way in which elements are interconnected.” (TechTarget.com, 2007) References: W3C. (2011). Extensible Markup Language (XML). Retrieved from W3.org: http://www.w3.org/XML/ W3Scools.com. (2011). SOAP Introduction. Retrieved from W3Scools.com: http://www.w3schools.com/soap/soap_intro.asp Tilkov, Stefan. (2007). A Brief Introduction to REST. Retrieved from Infoq.com: http://www.infoq.com/articles/rest-introduction TechTarget.com. (2011). loose coupling. Retrieved from TechTarget.com: http://searchnetworking.techtarget.com/definition/loose-coupling

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  • How do you manage extensibility in your multi-tenant systems?

    - by Brian MacKay
    I've got a few big web based multi-tenant products now, and very soon I can see that there will be a lot of customizations that are tenant specific. An extra field here or there, maybe an extra page or some extra logic in the middle of a workflow - that sort of thing. Some of these customizations can be rolled into the core product, and that's great. Some of them are highly specific and would get in everyone else's way. I have a few ideas in mind for managing this, but none of them seem to scale well. The obvious solution is to introduce a ton of client-level settings, allowing various 'features' to be enabled on per-client basis. The downside with that, of course, is massive complexity and clutter. You could introduce a truly huge number of settings, and over time various types of logic (presentation, business) could get way out of hand. Then there's the problem of client-specific fields, which begs for something cleaner than just adding a bunch of nullable fields to the existing tables. So what are people doing to manage this? Force.com seems to be the master of extensibility; obviously they've created a platform from the ground up that is super extensible. You can add on to almost anything with their web-based UI. FogBugz did something similiar where they created a robust plugin model that, come to think of it, might have actually been inspired by Force. I know they spent a lot of time and money on it and if I'm not mistaken the intention was to actually use it internally for future product development. Sounds like the kind of thing I could be tempted to build but probably shouldn't. :) Is a massive investment in pluggable architecture the only way to go? How are you managing these problems, and what kind of results are you seeing? EDIT: It does look as though FogBugz handled the problem by building a fairly robust platform and then using that to put together their screens. To extend it you create a DLL containing classes that implement interfaces like ISearchScreenGridColumn, and that becomes a module. I'm sure it was tremendously expensive to build considering that they have a large of devs and they worked on it for months, plus their surface area is perhaps 5% of the size of my application. Right now I am seriously wondering if Force.com is the right way to handle this. And I am a hard core ASP.Net guy, so this is a strange position to find myself in.

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  • Single Responsibility Principle Implementation

    - by Mike S
    In my spare time, I've been designing a CMS in order to learn more about actual software design and architecture, etc. Going through the SOLID principles, I already notice that ideas like "MVC", "DRY", and "KISS", pretty much fall right into place. That said, I'm still having problems deciding if one of two implementations is the best choice when it comes to the Single Responsibility Principle. Implementation #1: class User getName getPassword getEmail // etc... class UserManager create read update delete class Session start stop class Login main class Logout main class Register main The idea behind this implementation is that all user-based actions are separated out into different classes (creating a possible case of the aptly-named Ravioli Code), but following the SRP to a "tee", almost literally. But then I thought that it was a bit much, and came up with this next implementation class UserView extends View getLogin //Returns the html for the login screen getShortLogin //Returns the html for an inline login bar getLogout //Returns the html for a logout button getRegister //Returns the html for a register page // etc... as needed class UserModel extends DataModel implements IDataModel // Implements no new methods yet, outside of the interface methods // Haven't figured out anything special to go here at the moment // All CRUD operations are handled by DataModel // through methods implemented by the interface class UserControl extends Control implements IControl login logout register startSession stopSession class User extends DataObject getName getPassword getEmail // etc... This is obviously still very organized, and still very "single responsibility". The User class is a data object that I can manipulate data on and then pass to the UserModel to save it to the database. All the user data rendering (what the user will see) is handled by UserView and it's methods, and all the user actions are in one space in UserControl (plus some automated stuff required by the CMS to keep a user logged in or to ensure that they stay out.) I personally can't think of anything wrong with this implementation either. In my personal feelings I feel that both are effectively correct, but I can't decide which one would be easier to maintain and extend as life goes on (despite leaning towards Implementation #1.) So what about you guys? What are your opinions on this? Which one is better? What basics (or otherwise, nuances) of that principle have I missed in either design?

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  • Where should you put constants and why?

    - by Tim Meyer
    In our mostly large applications, we usually have a only few locations for constants: One class for GUI and internal contstants (Tab Page titles, Group Box titles, calculation factors, enumerations) One class for database tables and columns (this part is generated code) plus readable names for them (manually assigned) One class for application messages (logging, message boxes etc) The constants are usually separated into different structs in those classes. In our C++ applications, the constants are only defined in the .h file and the values are assigned in the .cpp file. One of the advantages is that all strings etc are in one central place and everybody knows where to find them when something must be changed. This is especially something project managers seem to like as people come and go and this way everybody can change such trivial things without having to dig into the application's structure. Also, you can easily change the title of similar Group Boxes / Tab Pages etc at once. Another aspect is that you can just print that class and give it to a non-programmer who can check if the captions are intuitive, and if messages to the user are too detailed or too confusing etc. However, I see certain disadvantages: Every single class is tightly coupled to the constants classes Adding/Removing/Renaming/Moving a constant requires recompilation of at least 90% of the application (Note: Changing the value doesn't, at least for C++). In one of our C++ projects with 1500 classes, this means around 7 minutes of compilation time (using precompiled headers; without them it's around 50 minutes) plus around 10 minutes of linking against certain static libraries. Building a speed optimized release through the Visual Studio Compiler takes up to 3 hours. I don't know if the huge amount of class relations is the source but it might as well be. You get driven into temporarily hard-coding strings straight into code because you want to test something very quickly and don't want to wait 15 minutes just for that test (and probably every subsequent one). Everybody knows what happens to the "I will fix that later"-thoughts. Reusing a class in another project isn't always that easy (mainly due to other tight couplings, but the constants handling doesn't make it easier.) Where would you store constants like that? Also what arguments would you bring in order to convince your project manager that there are better concepts which also comply with the advantages listed above? Feel free to give a C++-specific or independent answer. PS: I know this question is kind of subjective but I honestly don't know of any better place than this site for this kind of question. Update on this project I have news on the compile time thing: Following Caleb's and gbjbaanb's posts, I split my constants file into several other files when I had time. I also eventually split my project into several libraries which was now possible much easier. Compiling this in release mode showed that the auto-generated file which contains the database definitions (table, column names and more - more than 8000 symbols) and builds up certain hashes caused the huge compile times in release mode. Deactivating MSVC's optimizer for the library which contains the DB constants now allowed us to reduce the total compile time of your Project (several applications) in release mode from up to 8 hours to less than one hour! We have yet to find out why MSVC has such a hard time optimizing these files, but for now this change relieves a lot of pressure as we no longer have to rely on nightly builds only. That fact - and other benefits, such as less tight coupling, better reuseability etc - also showed that spending time splitting up the "constants" wasn't such a bad idea after all ;-)

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