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• The Dreaded Startup Repair Loop on Win 7

  - by HighAltitudeCoder

  For most people, upgrading to Windows 7 has been a relatively painless process.  Not me.  I am in the unlucky 1% or less who had a somewhat less pleasant experience.  First, I cloned my entire onto a larger (and much faster) solid state hard drive, only experiencing minimal problems. Then, I bought the Retail version of Windows 7 Ultimate, took a deep breath and... oh yeah, I almost forgot - BACK UP THE COMPUTER.  The next morning I upgraded to Win 7 and everything seemed fine, until... I rebooted the system, the nice Windows 7 launch graphics come up, it's about to launch and AWWW, are you kidding me?!?!  Back to the BIOS splash screen?  Next comes the sequence of failure - attempt repair - unable to repair - do you want to wipe your hard drive decisions. Because I purchased the retail version, a number is provided where I could call Microsoft Tech support.  When I did, they instructed me to click "Install" from my installation CD, which did not work.  When I tried the "Upgrade" option, it reaches an impasse, telling you that yoiu have a newer version of Win 7, and thus cannot Upgrade.  If you choose "Install" you willl lose everything... files, programs, EVERYTHING.  Or at least this is what it tells you.  I was not willing to take the risk. To make things worse, I had installed a new antivirus software application before I realized my system was unstable (Trend Micro Titanium Internet Security), and this was causing additional problems. One interesting thing, and the only saving grace as it turns out, was that my system WOULD successfully reboot into the OS if I chose to restart it, rather than shut it down.  If I chose to shut down, I would have to go through the loop again until I was given the option to restart. As it turned out, I needed to update my BIOS.  I assumed that since I had updated my BIOS a long time ago to settings that were stable under Windows Vista Ultimate x64, I incorrectly expected Win 7 to adopt the same settings and didn't expect there to be any problems.  WRONG. My BIOS had a setting to halt the boot cycle if various kinds of errors were detected.  Windows Vista didn't care about this, but forget it under Windows 7.  I turned immediately corrected that BIOS setting.  Next, there were the two separate BIOS settings: enable USB mouse and enable USB keyboard.  The only sequence of events that would work were to start my reboot process over from stratch with a hard-wired non-usb keyboard and mouse.  Whent the system booted under these settings, it doesn't detect any errors due to either the mouse or keyboard, and actually booted for the first time in a long while (let me tell ya, that's an amazing experience after fiddling with settings for two entire weekends!) Next step: leave your old mouse and keyboard connected, but also connect your other two devices (mouse, keyboard) that use USB connections.  During the boot cycle, the operating system will not fail due to missing requirements during startup, and it will then pick up the new drivers necessary to use your new hardware. If you think you are in the clear here, you are wrong.  The next VERY IMPORTANT step is to remember to change your settings in the BIOS upon next startup.  Specifically, yoiu will need ot change your BIOS to enable USB mouse and enable USB keyboard input.  If you don't, Windows will detect an incompatibility upon the next startup, and you will be stuck once again in the endless cycle of reboot/Startup Repair/reboot/Startup Repair, without ever reaching a successful boot. Here's the thing - the BIOS and the drivers registered in Win 7 need to match.  If they don't, you're going to lose another weekend worrying and fiddling, all the while wondering if you've permanently damaged your hard drive beyond repair. (Sigh).  In the end, things worked out.  I must note that it is saddening to see how many posts there are out there that recommend just doing a clean install, as if it's the only option.  How many countless poor souls have lost their data, their backups, their pictures and videos, all for nothing other than the fact that the person giving advice just didn't know what to do at that point? My advice to you, try having a look at your BIOS settings first and making sure Win 7 can find your BIOS settings, and also disabling in your BIOS anything that might halt your system boot-up process if it encounters errors.

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• How do I dig myself out of this DEEP hole? [closed]

  - by user74847

  I may be a bit bias in the way i word this but any opinions and suggestions are welcome. I should start by saying i have a MSc in CS and a degree in new media +6 years expereince and im probably around a middleweight developer. I started a web development company with my friend from uni a year ago, there was a 4 month gap in the middle where i went miles away work on a big project. Ive since returned and picked up where we left off. A year on though i find im still staying up til 5am and getting up at 9 sometimes 2-3 days without sleep. While i was away i was working 9-5 and struggling to keep up with doing stuff for my clients 8 hours ahead, after work, so things stagnated. We currently have about 12 active projects, with one other part time developer and a full time freelancer who is dealing with one of our major projects. I am solely responsible for concurrently developing 2 big sites similar to gumtree in functionality, at the same time as about 5-6+ small WordPress based 5-10page sites. a lot of the content isnt in yet or the client is delaying so i chop and change project every other day which does my head in. Is it reasonable to expect myself to remember the intricate details of each project when i come back to it a week later? and remember the details of a task which hasnt been written down? my business partner seems to think so. or am i just forgetful? Im particularly bad at estimating timescales which doesnt help, added to that a lot of the technologies im am using are new to me (a magento site took weeks to theme rather than days and was full of bugs, even after 1000's of google searches and hours reading forums) im still trying to learn and find the best CMS for us to use and getting my head around the likes of Bootstrap and jquery, Cpanel / Linux (we just got a blank vps for me to set up with no experience) even installing an SSL certificate caused everyone's mail clients to go down which was more stress for me to sort out. I find the pressure of the workload and timescales and trying to learn this stuff so fast is beginning to turn me against my career path. The fact that i never seem to get anything done really winds up my business partner and iv come to associate him with the stress and pain of the whole situation especially when I get berated or a look that says "oh you retard" when I forget something. Even today i spent hours learning how a particular themeforest theme worked with wordpress and how i could twist it to work for our partiuclar needs, on the surface had done no work, that triggered a 30 minute tirade of anger and stress and questioning what i had done from my business partner. had i taken too long to work on that? shoudl i have done it in 2 hours instead of 6? i told him i would take 2 hours. i was wrong. I feel like im running myself into the ground. My sleeping pattern has got so bad that when im working im half asleep and making mistakes, my eyes are constantly purple underneath, i literally fall asleep at my desk, its affecting my social life too, ive not slept more than lightly for the last year and grind through impossible code puzzles in my half sleep wich keeps me awake, when im already exhausted. plus the work is rushed and buggy when it does get done so drags on into the next project. I also procrastinate quite badly, pacing the livingroom, looking out the window when Im alone for three days straight in the flat and start to get cabin fever which means i do even less work and the negative feedback loop continues. I get told im the only one with the problem when i say that i cant work from home any more, and examples of other freelancers get brought up. an office wouldnt bring any extra cash in to the company but im convinced having that moving more than 2 meters away from my bed to go to "work" would get me working, at the moment i feel guilty like i should be working 24-7. It is important that we do all this work to raise enough cash to get our business to the next level but every month still feels like a struggle to pay the rent (there is about £20K coming in by Jan) and i have to borrow money from friends often to buy food or get a taxi to a meeting, so it is vital the money keeps coming in. (im also 20 mins late for nearly all meetings but thats a different issue) have you experienced anything similar? how can i deal with the issues ive raised? is it realistic to develop 10 sites at once? how can i improve my relationship with my business partner? do you struggle to work at home? how do you deal with that? i think if i dont get my life on track by feb i will seriously consider giving it all up, but that seems like such a waste. any ideas!!? i need help! Thanks.

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• Data Source Security Part 4

  - by Steve Felts

  So far, I have covered Client Identity and Oracle Proxy Session features, with WLS or database credentials.  This article will cover one more feature, Identify-based pooling.  Then, there is one more topic to cover - how these options play with transactions.Identity-based Connection Pooling An identity based pool creates a heterogeneous pool of connections.  This allows applications to use a JDBC connection with a specific DBMS credential by pooling physical connections with different DBMS credentials.  The DBMS credential is based on either the WebLogic user mapped to a database user or the database user directly, based on the “use database credentials” setting as described earlier. Using this feature enabled with “use database credentials” enabled seems to be what is proposed in the JDBC standard, basically a heterogeneous pool with users specified by getConnection(user, password). The allocation of connections is more complex if Enable Identity Based Connection Pooling attribute is enabled on the data source.  When an application requests a database connection, the WebLogic Server instance selects an existing physical connection or creates a new physical connection with requested DBMS identity. The following section provides information on how heterogeneous connections are created:1. At connection pool initialization, the physical JDBC connections based on the configured or default “initial capacity” are created with the configured default DBMS credential of the data source.2. An application tries to get a connection from a data source.3a. If “use database credentials” is not enabled, the user specified in getConnection is mapped to a DBMS credential, as described earlier.  If the credential map doesn’t have a matching user, the default DBMS credential is used from the datasource descriptor.3b. If “use database credentials” is enabled, the user and password specified in getConnection are used directly.4. The connection pool is searched for a connection with a matching DBMS credential.5. If a match is found, the connection is reserved and returned to the application.6. If no match is found, a connection is created or reused based on the maximum capacity of the pool: - If the maximum capacity has not been reached, a new connection is created with the DBMS credential, reserved, and returned to the application.- If the pool has reached maximum capacity, based on the least recently used (LRU) algorithm, a physical connection is selected from the pool and destroyed. A new connection is created with the DBMS credential, reserved, and returned to the application. It should be clear that finding a matching connection is more expensive than a homogeneous pool.  Destroying a connection and getting a new one is very expensive.  If you can use a normal homogeneous pool or one of the light-weight options (client identity or an Oracle proxy connection), those should be used instead of identity based pooling. Regardless of how physical connections are created, each physical connection in the pool has its own DBMS credential information maintained by the pool. Once a physical connection is reserved by the pool, it does not change its DBMS credential even if the current thread changes its WebLogic user credential and continues to use the same connection. To configure this feature, select Enable Identity Based Connection Pooling.  See http://docs.oracle.com/cd/E24329_01/apirefs.1211/e24401/taskhelp/jdbc/jdbc_datasources/EnableIdentityBasedConnectionPooling.html  "Enable identity-based connection pooling for a JDBC data source" in Oracle WebLogic Server Administration Console Help. You must make the following changes to use Logging Last Resource (LLR) transaction optimization with Identity-based Pooling to get around the problem that multiple users will be accessing the associated transaction table.- You must configure a custom schema for LLR using a fully qualified LLR table name. All LLR connections will then use the named schema rather than the default schema when accessing the LLR transaction table.  - Use database specific administration tools to grant permission to access the named LLR table to all users that could access this table via a global transaction. By default, the LLR table is created during boot by the user configured for the connection in the data source. In most cases, the database will only allow access to this user and not allow access to mapped users. Connections within Transactions Now that we have covered the behavior of all of these various options, it’s time to discuss the exception to all of the rules.  When you get a connection within a transaction, it is associated with the transaction context on a particular WLS instance. When getting a connection with a data source configured with non-XA LLR or 1PC (using the JTS driver) with global transactions, the first connection obtained within the transaction is returned on subsequent connection requests regardless of the values of username/password specified and independent of the associated proxy user session, if any. The connection must be shared among all users of the connection when using LLR or 1PC. For XA data sources, the first connection obtained within the global transaction is returned on subsequent connection requests within the application server, regardless of the values of username/password specified and independent of the associated proxy user session, if any.  The connection must be shared among all users of the connection within a global transaction within the application server/JVM.

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• Determining the angle to fire a shot when target and shooter moves, and bullet moves with shooter velocity added in

  - by Azaral

  I saw this question: Predicting enemy position in order to have an object lead its target and followed the link in the answer to stack overflow. In the stack overflow page I used the 2nd answer, the one that is a large mathematical derivation. My situation is a little different though. My first question though is will the answer provided in the stack overflow page even work to begin with, assuming the original circumstances of moving target and stationary shooter. My situation is a little different than that situation. My target moves, the shooter moves, and the bullets from the shooter start off with the velocities in x and y added to the bullets' x and y velocities. If you are sliding to the right, the bullets will remain in front of you as you move so as long as your velocity remains constant. What I'm trying to do is to get the enemy to be able to determine where they need to shoot in order to hit the player. Unless the player and enemy is stationary, the velocity from the ship adding to the velocity of the bullets will cause a miss. I'd rather like to prevent that. I used the formula in the stack overflow answer and did what I thought were the appropriate adjustments. I've been banging at this for the last four hours and I just can't make it click. It is probably something really simple and boneheaded that I am missing (that seems to be a lot of my problems lately). Here is the solution presented from the stack overflow answer: It boils down to solving a quadratic equation of the form: a * sqr(x) + b * x + c == 0 Note that by sqr I mean square, as opposed to square root. Use the following values: a := sqr(target.velocityX) + sqr(target.velocityY) - sqr(projectile_speed) b := 2 * (target.velocityX * (target.startX - cannon.X) + target.velocityY * (target.startY - cannon.Y)) c := sqr(target.startX - cannon.X) + sqr(target.startY - cannon.Y) Now we can look at the discriminant to determine if we have a possible solution. disc := sqr(b) - 4 * a * c If the discriminant is less than 0, forget about hitting your target -- your projectile can never get there in time. Otherwise, look at two candidate solutions: t1 := (-b + sqrt(disc)) / (2 * a) t2 := (-b - sqrt(disc)) / (2 * a) Note that if disc == 0 then t1 and t2 are equal. If there are no other considerations such as intervening obstacles, simply choose the smaller positive value. (Negative t values would require firing backward in time to use!) Substitute the chosen t value back into the target's position equations to get the coordinates of the leading point you should be aiming at: aim.X := t * target.velocityX + target.startX aim.Y := t * target.velocityY + target.startY Here is my code, after being corrected by Sam Hocevar (thank you again for your help!). It still doesn't work. For some reason it never enters the section of code inside the if(disc = 0) (obviously because it is always less than zero but...). However, if I plug the numbers from my game log on the enemy and player positions and velocities it outputs a valid firing solution. I have looked at the code side by side a couple of times now and I can't find any differences. There has got to be something simple I'm missing here. If someone else could look at this code and determine what is going on here I'd appreciate it. I know it's not going through that section because if it were, shouldShoot would become true and the enemy would be blasting away at the player. This section calls the function in question, CalculateShootHeading() if(shouldMove) { UseEngines(); } x += xVelocity; y += yVelocity; CalculateShootHeading(); if(shouldShoot) { ShootWeapons(); } UpdateWeapons(); This is CalculateShootHeading(). This is inside the enemy class so x and y are the enemy's x and y and the same with velocity. One output from my game log gives Player X = 2108, Player Y = -180.956, Player X velocity = 10.9949, Player Y Velocity = -6.26017, Enemy X = 1988.31, Enemy Y = -339.051, Enemy X velocity = 1.81666, Enemy Y velocity = -9.67762, 0 enemy projectiles. The output from the console tester is Bullet position = 2210.49, -239.313 and Player Position = 2210.49, -239.313. This doesn't make any sense. The only thing that could be different is the code or the input into my function in the game and I've checked that and I don't think that it is wrong as it's updated before this and never changed. float const bulletSpeed = 30.f; float const dx = playerX - x; float const dy = playerY - y; float const vx = playerXVelocity - xVelocity; float const vy = playerYVelocity - yVelocity; float const a = vx * vx + vy * vy - bulletSpeed * bulletSpeed; float const b = 2.f * (vx * dx + vy * dy); float const c = dx * dx + dy * dy; float const disc = b * b - 4.f * a * c; shouldShoot = false; if (disc >= 0.f) { float t0 = (-b - std::sqrt(disc)) / (2.f * a); float t1 = (-b + std::sqrt(disc)) / (2.f * a); if (t0 < 0.f || (t1 < t0 && t1 >= 0.f)) { t0 = t1; } if (t0 >= 0.f) { float shootx = vx + dx / t0; float shooty = vy + dy / t0; heading = std::atan2(shooty, shootx) * RAD2DEGREE; } shouldShoot = true; }

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• Using XA Transactions in Coherence-based Applications

  - by jpurdy

  While the costs of XA transactions are well known (e.g. increased data contention, higher latency, significant disk I/O for logging, availability challenges, etc.), in many cases they are the most attractive option for coordinating logical transactions across multiple resources. There are a few common approaches when integrating Coherence into applications via the use of an application server's transaction manager: Use of Coherence as a read-only cache, applying transactions to the underlying database (or any system of record) instead of the cache. Use of TransactionMap interface via the included resource adapter. Use of the new ACID transaction framework, introduced in Coherence 3.6.   Each of these may have significant drawbacks for certain workloads. Using Coherence as a read-only cache is the simplest option. In this approach, the application is responsible for managing both the database and the cache (either within the business logic or via application server hooks). This approach also tends to provide limited benefit for many workloads, particularly those workloads that either have queries (given the complexity of maintaining a fully cached data set in Coherence) or are not read-heavy (where the cost of managing the cache may outweigh the benefits of reading from it). All updates are made synchronously to the database, leaving it as both a source of latency as well as a potential bottleneck. This approach also prevents addressing "hot data" problems (when certain objects are updated by many concurrent transactions) since most database servers offer no facilities for explicitly controlling concurrent updates. Finally, this option tends to be a better fit for key-based access (rather than filter-based access such as queries) since this makes it easier to aggressively invalidate cache entries without worrying about when they will be reloaded. The advantage of this approach is that it allows strong data consistency as long as optimistic concurrency control is used to ensure that database updates are applied correctly regardless of whether the cache contains stale (or even dirty) data. Another benefit of this approach is that it avoids the limitations of Coherence's write-through caching implementation. TransactionMap is generally used when Coherence acts as system of record. TransactionMap is not generally compatible with write-through caching, so it will usually be either used to manage a standalone cache or when the cache is backed by a database via write-behind caching. TransactionMap has some restrictions that may limit its utility, the most significant being: The lock-based concurrency model is relatively inefficient and may introduce significant latency and contention. As an example, in a typical configuration, a transaction that updates 20 cache entries will require roughly 40ms just for lock management (assuming all locks are granted immediately, and excluding validation and writing which will require a similar amount of time). This may be partially mitigated by denormalizing (e.g. combining a parent object and its set of child objects into a single cache entry), at the cost of increasing false contention (e.g. transactions will conflict even when updating different child objects). If the client (application server JVM) fails during the commit phase, locks will be released immediately, and the transaction may be partially committed. In practice, this is usually not as bad as it may sound since the commit phase is usually very short (all locks having been previously acquired). Note that this vulnerability does not exist when a single NamedCache is used and all updates are confined to a single partition (generally implying the use of partition affinity). The unconventional TransactionMap API is cumbersome but manageable. Only a few methods are transactional, primarily get(), put() and remove(). The ACID transactions framework (accessed via the Connection class) provides atomicity guarantees by implementing the NamedCache interface, maintaining its own cache data and transaction logs inside a set of private partitioned caches. This feature may be used as either a local transactional resource or as logging XA resource. However, a lack of database integration precludes the use of this functionality for most applications. A side effect of this is that this feature has not seen significant adoption, meaning that any use of this is subject to the usual headaches associated with being an early adopter (greater chance of bugs and greater risk of hitting an unoptimized code path). As a result, for the moment, we generally recommend against using this feature. In summary, it is possible to use Coherence in XA-oriented applications, and several customers are doing this successfully, but it is not a core usage model for the product, so care should be taken before committing to this path. For most applications, the most robust solution is normally to use Coherence as a read-only cache of the underlying data resources, even if this prevents taking advantage of certain product features.

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• What's New in Oracle VM VirtualBox 4.2?

  - by Fat Bloke

  A year is a long time in the IT industry. Since the last VirtualBox feature release, which was a little over a year ago, we've seen: new releases of cool new operating systems, such as Windows 8, ChromeOS, and Mountain Lion; we've seen a myriad of new Linux releases from big Enterprise class distributions like Oracle 6.3, to accessible desktop distros like Ubuntu 12.04 and Fedora 17; and we've also seen the spec of a typical PC or laptop double in power. All of these events have influenced our new VirtualBox version which we're releasing today. Here's how... Powerful hosts  One of the trends we've seen is that as the average host platform becomes more powerful, our users are consistently running more and more vm's. Some of our users have large libraries of vm's of various vintages, whilst others have groups of vm's that are run together as an assembly of the various tiers in a multi-tiered software solution, for example, a database tier, middleware tier, and front-ends.  So we're pleased to unveil a more powerful VirtualBox Manager to address the needs of these users: VM Groups Groups allow you to organize your VM library in a sensible way, e.g.  by platform type, by project, by version, by whatever. To create groups you can drag one VM onto another or select one or more VM's and choose Machine...Group from the menu bar. You can expand and collapse groups to save screen real estate, and you can Enter and Leave a group (think iPad navigation here) by using the right and left arrow keys when groups are selected. But groups are more than passive folders, because you can now also perform operations on groups, rather than all the individual VMs. So if you have a multi-tiered solution you can start the whole stack up with just one click. Autostart Many VirtualBox users run dedicated services in their VMs, for example, running a Wiki. With these types of VM workloads, you really want the VM start up when the host machine boots up. So with 4.2 we've introduced a cross-platform Auto-start mechanism to allow you to treat VMs as host services. Headless VM Launching With VM's such as web servers, wikis, and other types of server-class workloads, the Console of the VM is pretty much redundant. For some time now VirtualBox has offered a separate launch mechanism for these VM's, namely the command-line interface commands VBoxHeadless or VBoxManage startvm ... --type headless commands. But with 4.2 we also allow you launch headless VMs from the Manager. Simply hold down Shift when launching the VM from the Manager.  It's that easy. But how do you stop a headless VM? Well, with 4.2 we allow you to Close the VM from the Manager. (BTW best to use the ACPI Shutdown method which allows the guest VM to close down gracefully.) Easy VM Creation For our expert users, the  New VM Wizard was a little tiresome, so now there's a faster 2-click VM creation mode. Just Hide the description when creating a new VM. Powerful VMs  As the hosts have become more powerful, so are the guests that are running inside them. Here are some of the 4.2 features to accommodate them: Virtual Network Interface Cards  With 4.2, it's now possible to create VMs with up to 36 NICs, when using the ICH9 chipset emulation. But with great power comes great responsibility (didn't Obi-Wan say something similar?), and so we have also introduced bandwidth limiting to prevent a rogue VM stealing the whole pipe. VLAN tagging Some of our users leverage VLANs extensively so we've enhanced the E1000 NICs to support this.  Processor Performance If you are running a CPU which supports Nested Paging (aka EPT in the Intel world) such as most of the Core i5 and i7 CPUs, or are running an AMD Bulldozer or later, you should see some performance improvements from our work with these processors. And while we're talking Processors, we've added support for some of the more modern VIA CPUs too. Powerful Automation Because VirtualBox runs atop a fully blown operating system, it makes sense to leverage the capabilities of the host to run scripts that can drive the guest VMs. Guest Automation was introduced in a prior release but with 4.2 we've revamped the APIs to allow a richer and more powerful set of operations to be executed by the guest. Check out the IGuest APIs in the VirtualBox Programming Guide and Reference (SDK). Powerful Platforms  All the hardcore engineering that has gone into 4.2 has been done for a purpose and that is to deliver a fast and powerful engine that can run almost any x86 OS because of the integrity of the virtualization. So we're pleased to add support for these platforms: Mac OS X "Mountain Lion"  Windows 8 Windows Server 2012 Ubuntu 12.04 (“Precise Pangolin”) Fedora 17 Oracle Linux 6.3  Here's the proof: We don't have time to go into the myriad of smaller improvements such as support for burning audio CDs from a guest, bi-directional clipboard control,  drag-and-drop of files into Linux guests, etc. so we'll leave that as an exercise for the user as soon as you've downloaded from the Oracle or community site and taken a peek at the User Guide. So all in all, a pretty solid release, one that we hope you'll enjoy discovering. - FB 

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• Who could ask for more with LESS CSS? (Part 1 of 3&ndash;Features)

  - by ToStringTheory

  It wasn’t very long ago that I first began to get into CSS precompilers such as SASS (Syntactically Awesome Stylesheets) and LESS (The Dynamic Stylesheet Language) and I had been hooked on the idea since.  When I finally had a new project come up, I leapt at the opportunity to try out one of these languages. Introduction To be honest, I was hesitant at first to add either framework as I didn’t really know much more than what I had read on their homepages, and I didn’t like the idea of adding too much complexity to a project - I couldn’t guarantee I would be the only person to support it in the future. Thankfully, both of these languages just add things into CSS.  You don’t HAVE to know LESS or SASS to do anything, you can still do your old school CSS, and your output will be the same.  However, when you want to start doing more advanced things such as variables, mixins, and color functions, the functionality is all there for you to utilize. From what I had read, SASS has a few more features than LESS, which is why I initially tried to figure out how to incorporate it into a MVC 4 project. However, through my research, I couldn’t find a way to accomplish this without including some bit of the Ruby on Rails framework on the computer running it, and I hated the fact that I had to do that.  Besides SASS, there is little chance of me getting into the RoR framework, at least in the next couple years.  So in the end, I settled with using LESS. Features So, what can LESS (or SASS) do for you?  There are several reasons I have come to love it in the past few weeks. 1 – Constants Using LESS, you can finally declare a constant and use its value across an entire CSS file. The case that most people would be familiar with is colors.  Wanting to declare one or two color variables that comprise the theme of the site, and not have to retype out their specific hex code each time, but rather a variable name.  What’s great about this is that if you end up having to change it, you only have to change it in one place.  An important thing to note is that you aren’t limited to creating constants just for colors, but for strings and measurements as well. 2 – Inheritance This is a cool feature in my mind for simplicity and organization.  Both LESS and SASS allow you to place selectors within other selectors, and when it is compiled, the languages will break the rules out as necessary and keep the inheritance chain you created in the selectors. Example LESS Code: #header {   h1 {     font-size: 26px;     font-weight: bold;   }   p {     font-size: 12px;     a     {       text-decoration: none;       &:hover {         border-width: 1px       }     }   } } Example Compiled CSS: #header h1 {   font-size: 26px;   font-weight: bold; } #header p {   font-size: 12px; } #header p a {   text-decoration: none; } #header p a:hover {   border-width: 1px; } 3 - Mixins Mixins are where languages like this really shine.  The ability to mixin other definitions setup a parametric mixin.  There is really a lot of content in this area, so I would suggest looking at http://lesscss.org for more information.  One of the things I would suggest if you do begin to use LESS is to also grab the mixins.less file from the Twitter Bootstrap project.  This file already has a bunch of predefined mixins for things like border-radius with all of the browser specific prefixes.  This alone is of great use! 4 – Color Functions This is the last thing I wanted to point out as my final post in this series will be utilizing these functions in a more drawn out manner.  Both LESS and SASS provide functions for getting information from a color (R,G,B,H,S,L).  Using these, it is easy to define a primary color, and then darken or lighten it a little for your needs.  Example: Example LESS Code: @base-color: #111; @red:        #842210; #footer {   color: (@base-color + #003300);   border-left:  2px;   border-right: 2px;   border-color: desaturate(@red, 10%); } Example Compiled CSS: #footer {    color: #114411;    border-left:  2px;    border-right: 2px;    border-color: #7d2717; } I have found that these can be very useful and powerful when constructing a site theme. Conclusion I came across LESS and SASS when looking for the best way to implement some type of CSS variables for colors, because I hated having to do a Find and Replace in all of the files using the colors, and in some instances, you couldn’t just find/replace because of the color choices interfering with other colors (color to replace of #000, yet come colors existed like #0002bc).  So in many cases I would end up having to do a Find and manually check each one. In my next post, I am going to cover how I’ve come to set up these items and the structure for the items in the project, as well as the conventions that I have come to start using.  In the final post in the series, I will cover a neat little side project I built in LESS dealing with colors!

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• Simple BizTalk Orchestration & Port Tutorial

  - by bosuch

  (This is a reference for a lunch & learn I'm giving at my company) This demo will create a BizTalk process that monitors a directory for an XML file, loads it into an orchestration, and drops it into a different directory. There’s no real processing going on (other than moving the file from one location to another), but this will introduce you to Messages, Orchestrations and Ports. To begin, create a new BizTalk Project names OrchestrationPortDemo: When the solution has been created, right-click the OrchestrationPortDemo solution name and select Add -> New Item. Add a BizTalk Orchestration named DemoOrchestration: Click Add and the orchestration will be created and displayed in the BizTalk Orchestration Designer. The designer allows you to visually create your business processes: Next, you will add a message (the basic unit of communication) to the orchestration. In the Orchestration View, right-click Messages and select New Message. In the message properties window, enter DemoMessage as the Identifier (the name), and select .NET Classes -> System.Xml.XmlDocument for Message Type. This indicates that we’ll be passing a standard Xml document in and out of the orchestration. Next, you will add Send and Receive shapes to the orchestration. From the toolbox, drag a Receive shape onto the orchestration (where it says “Drop a shape from the toolbox here”). Next, drag a Send shape directly below the Receive shape. For the properties of both shapes, select DemoMessage for Message – this indicates we’ll be passing around the message we created earlier. The Operation box will have a red exclamation mark next to it because no port has been specified. We will do this in a minute. On the Receive shape properties, you must be sure to select True for Activate. This indicates that the orchestration will be started upon receipt of a message, rather than being called by another orchestration. If you leave it set to false, when you try to build the application you’ll receive the error “You must specify at least one already-initialized correlation set for a non-activation receive that is on a non self-correlating port.” Now you’ll add ports to the orchestration. Ports specify how your orchestration will send and receive messages. Drag a port from the toolbox to the left-hand Port Surface, and the Port Configuration Wizard launches. For the first port (the receive port), enter the following information: Name: ReceivePort Select the port type to be used for this port: Create a new Port Type Port Type Name: ReceivePortType Port direction of communication: I’ll always be receiving <…> Port binding: Specify later By choosing “Specify later” you are choosing to bind the port (choose where and how it will send or receive its messages) at deployment time via the BizTalk Server Administration console. This allows you to change locations later without building and re-deploying the application. Next, drag a port to the right-hand Port Surface; this will be your send port. Configure it as follows: Name: SendPort Select the port type to be used for this port: Create a new Port Type Port Type Name: SendPortType Port direction of communication: I’ll always be sending <…> Port binding: Specify later Finally, drag the green arrow on the ReceivePort to the Receive_1 shape, and the green arrow on the SendPort to the Send_1 shape. Your orchestration should look like this: Now you have a couple final steps before building and deploying the application. In the Solution Explorer, right-click on OrchestrationPortDemo and select Properties. On the Signing tab, click “Sign the assembly”, and choose <New…> from the drop-down. Enter DemoKey as the Key file name, and deselect “Protect my key file with a password”. This will create the file DemoKey.snk in your solution. Signing the assembly gives it a strong name so that it can be deployed into the global assembly cache (GAC). Next, click the Deployment tab, and enter OrchestrationPortDemo as the Application Name. Save your solution. Click “Build OrchestrationPortDemo”. Your solution should (hopefully!) build with no errors. Click “Deploy OrchestrationPortDemo”. (Note – If you’re running Server 2008, Vista or Win7, you may get an error message. If so, close Visual Studio and run it as an administrator) That’s it! Your application is ready to be configured and fired up in the BizTalk Server Administration console, so stay tuned!

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• BIP 11g Dynamic SQL

  - by Tim Dexter

  Back in the 10g release, if you wanted something beyond the standard query for your report extract; you needed to break out your favorite text editor. You gotta love 'vi' and hate emacs, am I right? And get to building a data template, they were/are lovely to write, such fun ... not! Its not fun writing them by hand but, you do get to do some cool stuff around the data extract including dynamic SQL. By that I mean the ability to add content dynamically to your your query at runtime. With 11g, we spoiled you with a visual builder, no more vi or notepad sessions, a friendly drag and drop interface allowing you to build hierarchical data sets, calculated columns, summary columns, etc. You can still create the dynamic SQL statements, its not so well documented right now, in lieu of doc updates here's the skinny. If you check out the 10g process to create dynamic sql in the docs. You need to create a data trigger function where you assign the dynamic sql to a global variable that's matched in your report SQL. In 11g, the process is really the same, BI Publisher just provides a bit more help to define what trigger code needs to be called. You still need to create the function and place it inside a package in the db. Here's a simple plsql package with the 'beforedata' function trigger. Spec create or replace PACKAGE BIREPORTS AS whereCols varchar2(2000); FUNCTION beforeReportTrig return boolean; end BIREPORTS; Body create or replace PACKAGE BODY BIREPORTS AS   FUNCTION beforeReportTrig return boolean AS   BEGIN       whereCols := ' and d.department_id = 100';     RETURN true;   END beforeReportTrig; END BIREPORTS; you'll notice the additional where clause (whereCols - declared as a public variable) is hard coded. I'll cover parameterizing that in my next post. If you can not wait, check the 10g docs for an example. I have my package compiling successfully in the db. Now, onto the BIP data model definition. 1. Create a new data model and go ahead and create your query(s) as you would normally. 2. In the query dialog box, add in the variables you want replaced at runtime using an ampersand rather than a colon e.g. &whereCols.   select     d.DEPARTMENT_NAME, ...  from    "OE"."EMPLOYEES" e,     "OE"."DEPARTMENTS" d  where   d."DEPARTMENT_ID"= e."DEPARTMENT_ID" &whereCols   Note that 'whereCols' matches the global variable name in our package. When you click OK to clear the dialog, you'll be asked for a default value for the variable, just use ' and 1=1' That leading space is important to keep the SQL valid ie required whitespace. This value will be used for the where clause if case its not set by the function code. 3. Now click on the Event Triggers tree node and create a new trigger of the type Before Data. Type in the default package name, in my example, 'BIREPORTS'. Then hit the update button to get BIP to fetch the valid functions.In my case I get to see the following: Select the BEFOREREPORTTRIG function (or your name) and shuttle it across. 4. Save your data model and now test it. For now, you can update the where clause via the plsql package. Next time ... parametrizing the dynamic clause.

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• Tweaking Hudson memory usage

  - by rovarghe

  Hudson 3.1 has some performance optimizations that greatly reduces its memory footprint. Prior to this Hudson used to always hold the entire data model (all jobs and all builds) in memory which affected scalability. Some installations configured heap sizes in excess of 1GB to counteract this. Hudson 3.1.x maintains an MRU cache and only loads jobs and builds as they are required. Because of the inability to change existing APIs and be backward compatible with plugins, there were limits to how far we could go with this approach. Memory optimizations almost always come with a related cost, in this case its additional I/O that has to be performed to load data on request. On a small site that has frequent traffic, this is usually not noticeable since the MRU cache will usually hold on to all the data. A large site with infrequent traffic might experience some delays when the first request hits the server after a long gap. If you have a large heap and are able to allocate more memory, the cache settings can be adjusted to take advantage of this and even go back to pre-3.1 behavior. All the cache settings can be passed as options to the JVM container (Tomcat or the default Jetty container) using the -D option. There are two caches, independant of each other, one for Jobs and the other for Builds. For the jobs cache: hudson.jobs.cache.evict_in_seconds ( default=60 ) Seconds from last access (could be because of a servlet request or a background cron thread) a job should be purged from the cache. Set this to 0 to never purge based on time. hudson.jobs.cache.initial_capacity ( default=1024 ) Initial number of jobs the cache can accomodate. Setting this to the number of jobs you typically display on your Hudson landing page or home page will speed up consecutive access to that page. If the default is too large you may consider downsizing and using that memory for the Builds cache instead. hudson.jobs.cache.max_entries ( default=1024) Maximum number of jobs in the cache. The default is large enough for most installations, but if you find I/O activity when always accessing the hudson home page you might consider increasing this, but first verify if the I/O is caused by frequent eviction (see above), rather than by the cache not being large enough. For the builds cache: The builds cache is used to store Build objects as they are read from storage. Typically this happens when a user drills down into the details of a particular Job from the hudson hom epage. The cache is shared among builds for different jobs since in most installations all jobs are not accessed with the same frequency, so a per-job builds cache would be a waste of memory. hudson.job.builds.cache.evict_in_seconds ( default=60 ) Same as the equivalent Job cache, applied to Build. hudson.job.builds.cache.initial_capacity" ( default=512 ) Same as equivalent Job cache setting. Note the smaller initial size. If your site stores a large number of builds and has frequent access to more builds you might consider bumping this up. hudson.job.builds.cache.max_entries ( default=10240 ) The default max is large enough for most installations, the builds cache has bigger sized objects, so be careful about increasing the upper limit on this. See section on monitoring below. Sample usage: java -jar hudson-war-3.1.2-SNAPSHOT.war -Dhudson.jobs.cache.evict_in_seconds=300 \ -Dhudson.job.builds.cache.evict_in_seconds=300 Monitoring cache usage The 'jmap' tool that comes with the JDK can be used to monitor cache performance in an indirect way by looking at the number of Job and Build objects in each cache. Find the PID of the hudson instance and run $ jmap -histo:live <pid | grep 'hudson.model.*Lazy.*Key$' Here's a sample output: num #instances #bytes class name 523: 28 896 hudson.model.RunMap$LazyRunValue$Key 1200: 3 96 hudson.model.LazyTopLevelItem$Key These are the keys to the Jobs (LazyTopLevelItem$Key) and Builds (RunMap$LazyRunValue$Key) in the caches, so counting the number of keys is a good indicator of the number of items in the cache at any given moment. The size in bytes can be ignored, they are just the size of the keys, not the actual sizes of the objects they hold. Those sizes can only be obtained with a profiler. With the output above we can conclude that there are 3 jobs and 28 builds in memory. The 28 builds can all be from 1 job or all 3 jobs. Over time on an idle system, these should get evicted and memory cache should be empty. In practice, because of background cron threads and triggers, jobs rarely fall down to zero. Access of a job or a build by a cron thread resets the eviction timer.

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• Openlayers - Redraw() layer. Add / Remove layer.

  - by Ozaki

  TLDR: I have an Openlayers map with a layer called 'track' I want to remove track and add track back in. I have an image 'imageFeature' on a layer that rotates on load to the direction being set. I want it to update this rotation that is set in 'styleMap' on a layer called 'tracking'. I set the var 'stylemap' to apply the external image & rotation. The 'imageFeature' is added to the layer at the coords specified. 'imageFeature' is removed. 'imageFeature' is added again in its new location. Rotation is not applied.. As the 'styleMap' applies to the layer I think that I have to remove the layer and add it again rather than just the 'imageFeature' Layer: var tracking = new OpenLayers.Layer.GML("Tracking", "coordinates.json", { format: OpenLayers.Format.GeoJSON, styleMap: styleMap }); styleMap: var styleMap = new OpenLayers.StyleMap({ fillOpacity: 1, pointRadius: 10, rotation: heading, }); Now wrapped in a timed function the imageFeature: map.layers[3].addFeatures(new OpenLayers.Feature.Vector( new OpenLayers.Geometry.Point(longitude, latitude), {rotation: heading, type: parseInt(Math.random() * 3)} )); Type refers to a lookup of 1 of 3 images.: styleMap.addUniqueValueRules("default", "type", lookup); var lookup = { 0: {externalGraphic: "Image1.png", rotation: heading}, 1: {externalGraphic: "Image2.png", rotation: heading}, 2: {externalGraphic: "Image3.png", rotation: heading} } I have tried the 'redraw()' function: but it returns "tracking is undefined" or "map.layers[2]" is undefined. tracking.redraw(true); map.layers[2].redraw(true); Heading is a variable: from a JSON feed. var heading = 13.542; But so far can't get anything to work it will only rotate the image onload. The image will move in coordinates as it should though. So what am I doing wrong with the redraw function or how can I get this image to rotate live? Thanks in advance -Ozaki Add: I managed to get map.layers[2].redraw(true); to sucessfully redraw layer 2. But it still does not update the rotation. I am thinking because the stylemap is updating. But it runs through the style map every n sec, but no updates to rotation and the variable for heading is updating correctly if i put a watch on it in firebug.

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• Make @JsonTypeInfo property optional

  - by Mark Peters

  I'm using @JsonTypeInfo to instruct Jackson to look in the @class property for concrete type information. However, sometimes I don't want to have to specify @class, particularly when the subtype can be inferred given the context. What's the best way to do that? Here's an example of the JSON: { "owner": {"name":"Dave"}, "residents":[ {"@class":"jacksonquestion.Dog","breed":"Greyhound"}, {"@class":"jacksonquestion.Human","name":"Cheryl"}, {"@class":"jacksonquestion.Human","name":"Timothy"} ] } and I'm trying to deserialize them into these classes (all in jacksonquestion.*): public class Household { private Human owner; private List<Animal> residents; public Human getOwner() { return owner; } public void setOwner(Human owner) { this.owner = owner; } public List<Animal> getResidents() { return residents; } public void setResidents(List<Animal> residents) { this.residents = residents; } } public class Animal {} public class Dog extends Animal { private String breed; public String getBreed() { return breed; } public void setBreed(String breed) { this.breed = breed; } } public class Human extends Animal { private String name; public String getName() { return name; } public void setName(String name) { this.name = name; } } using this config: @JsonTypeInfo(use = JsonTypeInfo.Id.CLASS, include = JsonTypeInfo.As.PROPERTY, property = "@class") private static class AnimalMixin { } //... ObjectMapper objectMapper = new ObjectMapper(); objectMapper.getDeserializationConfig().addMixInAnnotations(Animal.class, AnimalMixin.class); Household household = objectMapper.readValue(json, Household.class); System.out.println(household); As you can see, the owner is declared as a Human, not an Animal, so I want to be able to omit @class and have Jackson infer the type as it normally would. When I run this though, I get org.codehaus.jackson.map.JsonMappingException: Unexpected token (END_OBJECT), expected FIELD_NAME: missing property '@class' that is to contain type id (for class jacksonquestion.Human) Since "owner" doesn't specify @class. Any ideas? One initial thought I had was to use @JsonTypeInfo on the property rather than the type. However, this cannot be leveraged to annotate the element type of a list.

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• NHibernate mapping with optimistic-lock="version" and dynamic-update="true" is generating invalid up

  - by SteveBering

  I have an entity "Group" with an assigned ID which is added to an aggregate in order to persist it. This causes an issue because NHibernate can't tell if it is new or existing. To remedy this issue, I changed the mapping to make the Group entity use optimistic locking on a sql timestamp version column. This caused a new issue. Group has a bag of sub objects. So when NHibernate flushes a new group to the database, it first creates the Group record in the Groups table, then inserts each of the sub objects, then does an update of the Group records to update the timestamp value. However, the sql that is generated to complete the update is invalid when the mapping is both dynamic-update="true" and optimistic-lock="version". Here is the mapping: <class xmlns="urn:nhibernate-mapping-2.2" dynamic-update="true" mutable="true" optimistic-lock="version" name="Group" table="Groups"> <id name="GroupNumber" type="System.String, mscorlib, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089"> <column name="GroupNumber" length="5" /> <generator class="assigned" /> </id> <version generated="always" name="Timestamp" type="BinaryBlob" unsaved-value="null"> <column name="TS" not-null="false" sql-type="timestamp" /> </version> <property name="UID" update="false" type="System.Guid, mscorlib, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089"> <column name="GroupUID" unique="true" /> </property> <property name="Description" type="AnsiString"> <column name="GroupDescription" length="25" not-null="true" /> </property> <bag access="field.camelcase-underscore" cascade="all" inverse="true" lazy="true" name="Assignments" mutable="true" order-by="GroupAssignAssignment"> <key foreign-key="fk_Group_Assignments"> <column name="GroupNumber" /> </key> <one-to-many class="Assignment" /> </bag> <many-to-one class="Aggregate" name="Aggregate"> <column name="GroupParentID" not-null="true" /> </many-to-one> </class> </hibernate-mapping> When the mapping includes both the dynamic update and the optimistic lock, the sql generated is: UPDATE groups SET WHERE GroupNumber = 11111 AND TS=0x00000007877 This is obviously invalid as there are no SET statements. If I remove the dynamic update part, everything gets updated during this update statement instead. This makes the statement valid, but rather unnecessary. Has anyone seen this issue before? Am I missing something? Thanks, Steve

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• GWT Javascript Exception in Hosted Mode: Result of expression 'doc.getBoxObjectFor' [undefined] is

  - by holmes

  Anyone ever seen this exception? I'm running in hosted mode on GWT 1.6.4 on a mac. I'm using the AutoSuggest and it's throwing this exception trying to show the popup. It works fine in compiled mode, but obviously hosted mode is rather important. [ERROR] Uncaught exception escaped com.google.gwt.core.client.JavaScriptException: (TypeError): Result of expression 'doc.getBoxObjectFor' [undefined] is not a function. line: 71 sourceId: 1152617088 sourceURL: jar:file:/Users/holmes/.m2/repository/com/google/gwt/gwt-user/1.6.4/gwt-user-1.6.4.jar!/com/google/gwt/dom/client/DOMImplMozillaOld.java expressionBeginOffset: 288 expressionCaretOffset: 307 expressionEndOffset: 313 at com.google.gwt.dom.client.DOMImplMozillaOld.getAbsoluteLeftImpl(Native Method) at com.google.gwt.dom.client.DOMImplMozillaOld.getAbsoluteLeft(DOMImplMozillaOld.java:29) at com.google.gwt.dom.client.Element$.getAbsoluteLeft$(Element.java:86) at com.google.gwt.user.client.DOM.getAbsoluteLeft(DOM.java:646) at com.google.gwt.user.client.ui.UIObject.getAbsoluteLeft(UIObject.java:487) at com.google.gwt.user.client.ui.PopupPanel.position(PopupPanel.java:1015) at com.google.gwt.user.client.ui.PopupPanel.access$5(PopupPanel.java:958) at com.google.gwt.user.client.ui.PopupPanel$1.setPosition(PopupPanel.java:811) at com.google.gwt.user.client.ui.PopupPanel.setPopupPositionAndShow(PopupPanel.java:700) at com.google.gwt.user.client.ui.PopupPanel.showRelativeTo(PopupPanel.java:809) at com.google.gwt.user.client.ui.SuggestBox.showSuggestions(SuggestBox.java:768) at com.google.gwt.user.client.ui.SuggestBox.access$3(SuggestBox.java:738) at com.google.gwt.user.client.ui.SuggestBox$1.onSuggestionsReady(SuggestBox.java:281) at com.google.gwt.user.client.ui.MultiWordSuggestOracle.requestSuggestions(MultiWordSuggestOracle.java:225) at com.google.gwt.user.client.ui.SuggestBox.showSuggestions(SuggestBox.java:640) at com.google.gwt.user.client.ui.SuggestBox.refreshSuggestions(SuggestBox.java:713) at com.google.gwt.user.client.ui.SuggestBox.access$6(SuggestBox.java:705) at com.google.gwt.user.client.ui.SuggestBox$1TextBoxEvents.onKeyUp(SuggestBox.java:678) at com.google.gwt.event.dom.client.KeyUpEvent.dispatch(KeyUpEvent.java:54) at com.google.gwt.event.dom.client.KeyUpEvent.dispatch(KeyUpEvent.java:1) at com.google.gwt.event.shared.HandlerManager$HandlerRegistry.fireEvent(HandlerManager.java:65) at com.google.gwt.event.shared.HandlerManager$HandlerRegistry.access$1(HandlerManager.java:53) at com.google.gwt.event.shared.HandlerManager.fireEvent(HandlerManager.java:178) at com.google.gwt.user.client.ui.Widget.fireEvent(Widget.java:52) at com.google.gwt.event.dom.client.DomEvent.fireNativeEvent(DomEvent.java:116) at com.google.gwt.user.client.ui.Widget.onBrowserEvent(Widget.java:90) at com.google.gwt.user.client.ui.TextBoxBase.onBrowserEvent(TextBoxBase.java:193) at com.google.gwt.user.client.ui.Composite.onBrowserEvent(Composite.java:54) at com.google.gwt.user.client.DOM.dispatchEventImpl(DOM.java:1320) at com.google.gwt.user.client.DOM.dispatchEventAndCatch(DOM.java:1299) at com.google.gwt.user.client.DOM.dispatchEvent(DOM.java:1262)

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• Validating an XML document fragment against XML schema

  - by shylent

  Terribly sorry if I've failed to find a duplicate of this question. I have a certain document with a well-defined document structure. I am expressing that structure through an XML schema. That data structure is operated upon by a RESTful service, so various nodes and combinations of nodes (not the whole document, but fragments of it) are exposed as "resources". Naturally, I am doing my own validation of the actual data, but it makes sense to validate the incoming/outgoing data against the schema as well (before the fine-grained validation of the data). What I don't quite grasp is how to validate document fragments given the schema definition. Let me illustrate: Imagine, the example document structure is: <doc-root> <el name="foo"/> <el name="bar"/> </doc-root> Rather a trivial data structure. The schema goes something like this: <xsd:schema xmlns:xsd="http://www.w3.org/2001/XMLSchema"> <xsd:element name="doc-root"> <xsd:complexType> <xsd:sequence> <xsd:element name="el" type="myCustomType" /> </xsd:sequence> </xsd:complexType> </xsd:element> <xsd:complexType name="myCustomType"> <xsd:attribute name="name" use="required" /> </xsd:complexType> </xsd:schema> Now, imagine, I've just received a PUT request to update an 'el' object. Naturally, I would receive not the full document or not any xml, starting with 'doc-root' at its root, but the 'el' element itself. I would very much like to validate it against the existing schema then, but just running it through a validating parser wouldn't work, since it will expect a 'doc-root' at the root. So, again, the question is, - how can one validate a document fragment against an existing schema, or, perhaps, how can a schema be written to allow such an approach. Hope it made sense.

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• Runge-Kutta (RK4) integration for game physics

  - by Kai

  Gaffer on Games has a great article about using RK4 integration for better game physics. The implementation is straightforward but the math behind it confuses me. I understand derivatives and integrals on a conceptual level but I haven't manipulated equations in a long time. Here's the brunt of Gaffer's implementation: void integrate(State &state, float t, float dt) { Derivative a = evaluate(state, t, 0.0f, Derivative()); Derivative b = evaluate(state, t+dt*0.5f, dt*0.5f, a); Derivative c = evaluate(state, t+dt*0.5f, dt*0.5f, b); Derivative d = evaluate(state, t+dt, dt, c); const float dxdt = 1.0f/6.0f * (a.dx + 2.0f*(b.dx + c.dx) + d.dx); const float dvdt = 1.0f/6.0f * (a.dv + 2.0f*(b.dv + c.dv) + d.dv) state.x = state.x + dxdt * dt; state.v = state.v + dvdt * dt; } Can anybody explain in simple terms how RK4 works? Specifically, why are we averaging the derivatives at 0.0f, 0.5f, 0.5f, and 1.0f? How is averaging derivatives up to the 4th order different from doing a simple euler integration with a smaller timestep? After reading the accepted answer below, and several other articles, I have a grasp on how RK4 works. To answer my own questions: Can anybody explain in simple terms how RK4 works? RK4 takes advantage of the fact that we can get a much better approximation of a function if we use its higher-order derivatives rather than just the first or second derivative. That's why the Taylor series converges much faster than Euler approximations. (take a look at the animation on the right side of that page) Specifically, why are we averaging the derivatives at 0.0f, 0.5f, 0.5f, and 1.0f? The Runge-Kutta method is an approximation of a function that samples derivatives of several points within a timestep, unlike the Taylor series which only samples derivatives of a single point. After sampling these derivatives we need to know how to weigh each sample to get the closest approximation possible. An easy way to do this is to pick constants that coincide with the Taylor series, which is how the constants of a Runge-Kutta equation are determined. This article made it clearer for me: http://web.mit.edu/10.001/Web/Course%5FNotes/Differential%5FEquations%5FNotes/node5.html. Notice how (15) is the Taylor series expansion while (17) is the Runge-Kutta derivation. How is averaging derivatives up to the 4th order different from doing a simple euler integration with a smaller timestep? Mathematically it converges much faster than doing many Euler approximations. Of course, with enough Euler approximations we can gain equal accuracy to RK4, but the computational power needed doesn't justify using Euler.

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• Creating an Objective-C++ Static Library in Xcode

  - by helixed

  So I've developed an engine for the iPhone with which I'd like to build a couple different games. Rather than copy and paste the files for the engine inside of each game's project directory, I'd a way to link to the engine from each game, so if I need to make a change to it I only have to do so once. After reeding around a little bit, it seems like static libraries are the best way to do this on the iPhone. I created a new project called Skeleton and copied all of my engine files over to it. I used this guide to create a static library, and I imported the library into a project called Chooser. However, when I tried to compile the project, Xcode started complaining about some C++ data structures I included in a file called ControlScene.mm. Here's my build errors: "operator delete(void*)", referenced from: -[ControlScene dealloc] in libSkeleton.a(ControlScene.o) -[ControlScene init] in libSkeleton.a(ControlScene.o) __gnu_cxx::new_allocator<operation_t>::deallocate(operation_t*, unsigned long)in libSkeleton.a(ControlScene.o) __gnu_cxx::new_allocator<operation_t*>::deallocate(operation_t**, unsigned long)in libSkeleton.a(ControlScene.o) "operator new(unsigned long)", referenced from: -[ControlScene init] in libSkeleton.a(ControlScene.o) __gnu_cxx::new_allocator<operation_t*>::allocate(unsigned long, void const*)in libSkeleton.a(ControlScene.o) __gnu_cxx::new_allocator<operation_t>::allocate(unsigned long, void const*)in libSkeleton.a(ControlScene.o) "std::__throw_bad_alloc()", referenced from: __gnu_cxx::new_allocator<operation_t*>::allocate(unsigned long, void const*)in libSkeleton.a(ControlScene.o) __gnu_cxx::new_allocator<operation_t>::allocate(unsigned long, void const*)in libSkeleton.a(ControlScene.o) "___cxa_rethrow", referenced from: std::_Deque_base<operation_t, std::allocator<operation_t> >::_M_create_nodes(operation_t**, operation_t**)in libSkeleton.a(ControlScene.o) std::_Deque_base<operation_t, std::allocator<operation_t> >::_M_initialize_map(unsigned long)in libSkeleton.a(ControlScene.o) "___cxa_end_catch", referenced from: std::_Deque_base<operation_t, std::allocator<operation_t> >::_M_create_nodes(operation_t**, operation_t**)in libSkeleton.a(ControlScene.o) std::_Deque_base<operation_t, std::allocator<operation_t> >::_M_initialize_map(unsigned long)in libSkeleton.a(ControlScene.o) "___gxx_personality_v0", referenced from: ___gxx_personality_v0$non_lazy_ptr in libSkeleton.a(ControlScene.o) ___gxx_personality_v0$non_lazy_ptr in libSkeleton.a(MenuLayer.o) "___cxa_begin_catch", referenced from: std::_Deque_base<operation_t, std::allocator<operation_t> >::_M_create_nodes(operation_t**, operation_t**)in libSkeleton.a(ControlScene.o) std::_Deque_base<operation_t, std::allocator<operation_t> >::_M_initialize_map(unsigned long)in libSkeleton.a(ControlScene.o) ld: symbol(s) not found collect2: ld returned 1 exit status If anybody could offer some insight as to why these problems are occuring, I'd appreciate it. Thanks, helixed

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• Dissertation about website and database security - in need of some pointers

  - by ClarkeyBoy

  Hi, I am on my dissertation in my final year at university at the moment. One of the areas I need to research is security - for both websites and for databases. I currently have sections on the following: Website Form security - such as data validation. This section is more about preventing errors made by legitimate users as much as possible rather than stopping hackers, for example comparing a field to a regular expression and giving them meaningful feedback on any errors which did occur so as to stop it happening again. Constraints. For example if a value must be true or false then use a checkbox. If it is likely to be one of several values then use a dropdown or a set of radio boxes, and so on. If the value is unpredictable then use regular expressions to limit what characters they are allowed to enter, and to restrict the length of the string, and sometimes to limit the format (such as for dates / times, post codes and so on). Sometimes you can limit permissions to the form. This is on the occasion that you know exactly who (whether it be peoples names or a group of people - such as administrators or employees) is going to need access to the form. Restricting permissions will stop members of the public from being able to access the form. Symbols or strings which could be used maliciously or cause the website to act incorrectly (such as the script tag) should be filtered out or html encoded. Captcha images can be used to prevent automated systems from filling in and submitting the form. There are some hacks for file uploads - such as using double extensions - which can allow hackers to upload malicious files. Databases (this is nowhere near done yet but the sections I have planned are listed below) SQL statements vs stored procedures Throwing an error when one of the variables contains particular characters or groups of characters (I cant remember what characters they are, but I have seen a message thrown back at me before where I have tried to enter html or something into a text area). SQL Injection - and ways around it, with some examples. Does anyone have any hints and tips on where I could go for some decent, reliable information either about these areas or about other areas of security that I could cover? Thanks in advance. Regards, Richard PS I am a complete newbie when it comes to security, so please be patient with me. If any of the information I have put down is wrong or could be sub-sectioned then please feel free to say so.

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• WPF: TextBox expanding with surrounding Grid but not with text

  - by haagel

  I have a problem with a TextBox in an application... A window has a Grid with two columns. The left column contains a control with a constant width but with a height that adapts. The right column contains a TextBox that takes up all remaining space in the Grid (and thereby in the Window). The Grid is given a minimal width and height and is wrapped within a ScrollViewer. If the user resizes the window to be smaller than the minimal widht/height of the Grid, scrollbars are displayed. This is exactly how I want it to be. However, a problem occurs when the user starts typing text. If the text is to long to fit in one line in the TextBox, I want the text to wrap. Therefore I set TextWrapping="Wrap" on the TextBox. But since the TextBox has an automatic width and is wrapped in a ScrollViewer (its actually the whole Grid that is wrapped), the TextBox just keeps expanding to the right. I do want the TextBox to expand if the window is expanded, but I don't want the TextBox to expand by the text. Rather the text should wrap inside the available TextBox. If the text don't fit within the TextBox height, a scrollbar should be displayed within the TextBox. Is there a way to accomplish this? Below is some code that shows my problem. <Window x:Class="AdaptingTextBoxes.MainWindow" xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" Title="MainWindow" Height="300" Width="400" Background="DarkCyan"> <Grid Margin="10" Name="LayoutRoot"> <ScrollViewer HorizontalScrollBarVisibility="Auto" VerticalScrollBarVisibility="Auto"> <Grid MinWidth="300" MinHeight="200"> <Grid.ColumnDefinitions> <ColumnDefinition Width="auto" /> <ColumnDefinition Width="*" /> </Grid.ColumnDefinitions> <Button Grid.Column="0" Margin="0,0,10,0" Content="Button" Width="100" /> <TextBox Grid.Column="1" AcceptsReturn="True" TextWrapping="Wrap" ScrollViewer.HorizontalScrollBarVisibility="Disabled" ScrollViewer.VerticalScrollBarVisibility="Auto" /> </Grid> </ScrollViewer> </Grid> </Window>

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• Using Joda DateTime as a Jersey parameter?

  - by HolySamosa

  I'd like to use Joda's DateTime for query parameters in Jersey, but this isn't supported by Jersey out-of-the-box. I'm assuming that implementing an InjectableProvider is the proper way to add DateTime support. Can someone point me to a good implementation of an InjectableProvider for DateTime? Or is there an alternative approach worth recommending? (I'm aware I can convert from Date or String in my code, but this seems like a lesser solution). Thanks. Solution: I modified Gili's answer below to use the @Context injection mechanism in JAX-RS rather than Guice. import com.sun.jersey.core.spi.component.ComponentContext; import com.sun.jersey.spi.inject.Injectable; import com.sun.jersey.spi.inject.PerRequestTypeInjectableProvider; import java.util.List; import javax.ws.rs.QueryParam; import javax.ws.rs.WebApplicationException; import javax.ws.rs.core.Context; import javax.ws.rs.core.Response; import javax.ws.rs.core.Response.Status; import javax.ws.rs.core.UriInfo; import javax.ws.rs.ext.Provider; import org.joda.time.DateTime; /** * Enables DateTime to be used as a QueryParam. * <p/> * @author Gili Tzabari */ @Provider public class DateTimeInjector extends PerRequestTypeInjectableProvider<QueryParam, DateTime> { private final UriInfo uriInfo; /** * Creates a new DateTimeInjector. * <p/> * @param uriInfo an instance of {@link UriInfo} */ public DateTimeInjector( @Context UriInfo uriInfo) { super(DateTime.class); this.uriInfo = uriInfo; } @Override public Injectable<DateTime> getInjectable(final ComponentContext cc, final QueryParam a) { return new Injectable<DateTime>() { @Override public DateTime getValue() { final List<String> values = uriInfo.getQueryParameters().get(a.value()); if( values == null || values.isEmpty()) return null; if (values.size() > 1) { throw new WebApplicationException(Response.status(Status.BAD_REQUEST). entity(a.value() + " may only contain a single value").build()); } return new DateTime(values.get(0)); } }; } }

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• ActiveDirectoryMembershipProvider and ADAM (or AD LDS) and SetPassword

  - by Iulian

  By the subject line it seems to be a rather broad subject and I need some help here. Basically what I want is to use ActiveDirectoryMembershipProvider with an ADAM instance to authenticate users in an ASP.NET web application. My development environment is a windows 7 machine with an AD LDS instance on it whilst the QA server is a Windows 2003 server with an ADAM instance on it. I have all the required users on both instances plus one with adminsitrator role (CN=Admin,CN=xxx,DC=xxx,C=xx) which I want to use as the connection user. Using connectonProtecton="None" connectionUsername="CN=Admin,CN=xxx,DC=xxx,C=xx" connectionPassword="xxx" I am able to authenticate on both environments (dev & qa). If I change to the connectionProtection to "Secure" I am not able to authenticate anymore; the error I get is "Parser Error Message: Unable to establish secure connection with the server" To me it sounds wrong to use connectionProtection="None" although I found on the net a lot of samples using this setting. Can I use connectionProtection="Secure" to connect to an ADAM instance using an account defined on that instance having Administrator role? What other choices do I have (like using an domain account)? What if my machine where I am to deploy the application is not a part of the domain, will this affect in any way the behavior? I am novice in the respect so I would really appreciate some clear answers or some directions as where to look? Now beside the "signing in" feature of the ActiveDirectoryMembershipProvider I also want to add an extra one, which is setting the password without knowing the old one (something that will be used by a "reset password" feature). So I added a couple of extension methods to the provider, and used System.DirectoryServices classes like DirectoryEntry and the like. When creating a directory entry I use the same credentials provided in web.config for the provider minus the AuthenticationType as I don't know what is right combination of the flags that corresponds to None/Secure. I am able to use Invoke "SetPassword" with ADS_OPTION_PASSWORD_METHOD option as ADS_PASSWORD_ENCODE_CLEAR on my dev machine (w/ AD LDS instance); nevertheless on qa environment (w/ ADAM instance) I am getting an error like "Exception Details: System.DirectoryServices.DirectoryServicesCOMException: An operations error occurred. (Exception from HRESULT: 0x80072020)" I am quite sure it is not about AD LDS vs ADAM but probably another configuration / permission issue. So can anyone help me with some hints on how to use this SetPassword feature? And as a general question what are the best practices when it comes to using ADAM regarding security, programming etc? Thanks in advance Iulian

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• Best ASP.NET E-Commerce Framework (aspDotNetStoreFront, AbleCommerce, BVCommerce, MediaChase,...)

  - by EfficionDave

  I need a full-featured asp.net E-Commerce solution for a project. It needs to be easily extensible as I need to extend it to integrate with a custom Flash based personalization engine. It should also have a great administrative back-end that handles inventory tracking, report, labels, shipping, ... so that the client can really use it as the basis for their business. I've used quite a few different E-Commerce systems including OSCommerce, Zen Cart, Catalook, and eTailer. While I was impressed with Zen Cart and eTailer, this project is big enough that I want to try a more serious, commercial offering. I'm particularly interested in thoughts on aspdotnetstorefront, BVCommerce, AbleCommerce, and MediaChase. [UPDATE] I've done quite a bit of evaluation since I posted this question and will give some of my findings below: BVCommerce - The price point is nice, the product seems fairly well regarded, and I've heard good things about customizing/extending it, it just doesn't seem like it's going to meet my needs as an Top Tier ECommerce solution. After viewing the tutorial videos, the Admin interface just seems too basic and outdated. aspDotNetStorefront - The integration with DotNetNuke was it's biggest selling point for me but after reading peoples opinions, it's integration seems quite weak. It's sounds like there's a significant learning curve and the architecture just doesn't sound like it's as clean as it should be. AbleCommerce - After a rather thorough evaluation, I have selected AbleCommerce for at least my next project. The Admin interface is beautiful and has a nice list of features. The E-Commerce portion of the user side is very well done, highly skin-able (using Master Pages and a couple other techniques), and the checkout workflow has all the features I need while still being very clean. Source to the API can be bought for $500 but you generally won't need it. There are some 3rd party modules available but there's not currently a large market for these. The biggest glaring weakness of AbleCommerce I've found is their CMS capabilities are very limited and not at all well suited for a non-technical user to make most site content updates. But I have a good solution for that that I plan adapting into AbleCommerce. They will automatically generate a site for you to play with to your heart's content for 30 days. It is defniitely worth checking out.

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• Why does Sharepoint 2010 Web Reference work, but Service Reference does not

  - by Darien Ford

  Sharepoint is setup to use NTLM authentication. When I reference http://myserver/Sites/Ops/_vti_bin/Lists.asmx?WSDL as a Web Reference, I can call the methods and get valid responses. When I reference the same url as a Service Reference, the server throws an exception when calling methods. My account is admin on the Sharepoint Farm. This is the app.config for the service reference (mostly auto generated): <?xml version="1.0" encoding="utf-8" ?> <configuration> <configSections> </configSections> <system.serviceModel> <bindings> <basicHttpBinding> <binding name="ListsSoap" closeTimeout="00:01:00" openTimeout="00:01:00" receiveTimeout="00:10:00" sendTimeout="00:01:00" allowCookies="false" bypassProxyOnLocal="false" hostNameComparisonMode="StrongWildcard" maxBufferSize="65536" maxBufferPoolSize="524288" maxReceivedMessageSize="65536" messageEncoding="Text" textEncoding="utf-8" transferMode="Buffered" useDefaultWebProxy="true"> <readerQuotas maxDepth="32" maxStringContentLength="8192" maxArrayLength="16384" maxBytesPerRead="4096" maxNameTableCharCount="16384" /> <security mode="TransportCredentialOnly"> <transport clientCredentialType="Ntlm" /> </security> </binding> </basicHttpBinding> </bindings> <client> <endpoint address="http://myserver/Sites/Ops/_vti_bin/Lists.asmx" binding="basicHttpBinding" bindingConfiguration="ListsSoap" contract="SharepointLists.ListsSoap" name="ListsSoap" /> </client> </system.serviceModel> </configuration> Saddly, the only information the exception provides is this: "Exception of type 'Microsoft.SharePoint.SoapServer.SoapServerException' was thrown." No other details. The code that I'm using is: public ListClass() { _Client = new SharepointLists.ListsSoapClient(); } public System.Xml.Linq.XElement GetTaskList() { return _Client.GetList("Tasks"); } Any thoughts? I would like to use the Service Reference rather than the Web Reference. UPDATE: I tried Rob's suggestion and got this error: HTTP GET Error URI: http://myserver/Sites/Ops/_vti_bin/Lists.asmx The document at the url http://myserver/Sites/Ops/_vti_bin/Lists.asmx was not recognized as a known document type. The error message from each known type may help you fix the problem: - Report from 'http://myserver/Sites/Ops/_vti_bin/Lists.asmx' is 'The document format is not recognized (the content type is 'text/html; charset=utf-8').'. - Report from 'DISCO Document' is 'There was an error downloading 'http://myserver/_vti_bin/Lists.asmx?disco'.'. - The request failed with HTTP status 404: Not Found. - Report from 'WSDL Document' is 'The document format is not recognized (the con tent type is 'text/html; charset=utf-8').'. - Report from 'XML Schema' is 'The document format is not recognized (the conten t type is 'text/html; charset=utf-8').'.

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• How to get dropdown value using jsp:useBean and jsp:setProperty?

  - by littlevahn

  I have a rather simple form in JSP that looks like this: <form action="response.jsp" method="POST"> <label>First Name:</label><input type="text" name="firstName" /><br> <label>Last Name:</label><input type="text" name="lastName" /><br> <label>Email:</label><input type="text" name="email" /><br> <label>Re-enter Email:</label><input type="text" name="emailRe" /><br> <label>Address:</label><input type="text" name="address" /><br> <label>Address 2:</label><input type="text" name="address2" /><br> <label>City:</label><input type="text" name="city" /><br> <label>Country:</label> <select name="country"> <option value="0">--Country--</option> <option value="1">United States</option> <option value="2">Canada</option> <option value="3">Mexico</option> </select><br> <label>Phone:</label><input type="text" name="phone" /><br> <label>Alt Phone:</label><input type="text" name="phoneAlt" /><br> <input type="submit" value="submit" /> </form> But when I try and access the value of the select box in my Java class I get null. Ive tried reading it in as a String and an Array of strings neither though seems to be grabbing the right value. The response.jsp looks like this: <%@ page language="java" %> <%@ page import="java.util.*" %> <%@page contentType="text/html" pageEncoding="UTF-8"%> <%! %> <jsp:useBean id="formHandler" class="validation.RegHandler" scope="request"> <jsp:setProperty name="formHandler" property="*" /> </jsp:useBean> <% if (formHandler.validate()) { %> <jsp:forward page="success.jsp"/> <% } else { %> <jsp:forward page="retryReg.jsp"/> <% } %> I already have Java script validation in place but I wanted to make sure I covered validation and checking for non-JS users. The RegHandler just uses the name field to refer to the value in the form. Any Idea how I could access the select box's value?

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• How to change Jquery UI Slider handle

  - by Tom

  I want to modify the stock JQuery UI slider so that the handle has a arrow on it rather than being a square. i.e. I want to use a custom image as the handle. There are a few tutorials that do it: http://jqueryfordesigners.com/slider-gallery/ http://www.ryancoughlin.com/2008/11/04/using-the-jquery-ui-slider/ http://www.keepthewebweird.com/creating-a-nice-slider-with-jquery-ui/ But I can't get it to work. The following code results in a stationary handle image: <!DOCTYPE html> <html> <head> <link type="text/css" href="http://jqueryui.com/latest/themes/base/ui.all.css" rel="stylesheet" /> <script type="text/javascript" src="http://jqueryui.com/latest/jquery-1.3.2.js"></script> <script type="text/javascript" src="http://jqueryui.com/latest/ui/ui.core.js"></script> <script type="text/javascript" src="http://jqueryui.com/latest/ui/ui.slider.js"></script> <style type="text/css"> #myhandle {position: absolute;z-index: 100;height: 25px;width: 35px;top: auto;background: url(http://stackoverflow.com/content/img/so/vote-arrow-down.png) no-repeat;} </style> <script type="text/javascript"> $(document).ready(function(){ $("#slider").slider({handle: '#myhandle'}); }); </script> </head> <body> <div id="slider"><div id="myhandle"></div></div> </body> </html> It is as if JQuery doesn't pick up that I want to use the myhandle id for the handle. I'm wondering: Do I need a plugin for JQuery to recognise the handle option? (it is not documented in http://docs.jquery.com/UI/Slider). Or perhaps it only worked in an old version of JQuery? Any ideas?

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