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  • Algorithm to make groups of units

    - by M28
    In Age of Mythology and some other strategy games, when you select multiple units and order them to move to some place, they make a "group" when they reach the desired location: I have a Vector with several sprites, which are the selected units, the variables tarX and tarY are the target x and y. I just want an example, so you can just set the x and y position and I can adapt it to my code. Also, I would like to ask that the algorithm calls "isWalkable" for the x and y position, to determine if it's a valid position for each unit.

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  • Serverside memory efficiency and threading for a turn based game

    - by SkeletorFromEterenia
    Im programming on a turn based war-game for some years now (along with the engine) and Im having quite a hard time at figuring out what the games server architecture should look like, since most game server architecture articles I found focus either on FPS oder MMOGs, which doesn't really fit since I want many matches with 1- 16 players on my server, with each match being played in turn based mode. My chief concern is memory usage, since the most basic approach of loading every game that is being played completely into RAM should be quite inefficient, so is there a suitable strategy for selecting only the needed bits and loading them? Another question I got is how to design the threading on the server, since I think using only a single thread could be a problem due to the fact that the game or part of it might have to be loaded from the database. I would be very happy if you could share your knowledge or point me to material on this topic.

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  • How do I share common classes between windows forms and web applications using C#?

    - by earthdog
    In our environment we have multiple ERP servers plus data that are coming from multiple sources. I need to create a development roadmap for the coming years as it is obvious that side applications will be needed for many things. The choice is that the development will occur with Microsoft technologies. This means that I will be building either web apps (MVC, web forms e.t.c) or standard windows forms applications. The thing here is that I will be creating classes that will encapsulate the business logic that I want to apply to the different projects. What I thought so far: 1) Create class libraries dlls containing the required logic 2) Reuse these libs in my apps. But what about the web apps? Should I use the dlls directly or I should encapsulate them in web services and consume the web services in web apps? In general I would like to find out how should I build my strategy.

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  • Your home backup strategy

    - by David Pokluda
    What is your recommended backup strategy for home computers? I have two computers - desktop and notebook. All the important data is store on the desktop computer. I am currently using Mozy to backup my data from desktop computer to Mozy servers. What do you use?

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  • IT Optimization Plan Pays Off For UK Retailer

    - by Brian Dayton
    I caught this article in ComputerworldUK yesterday. The headline talks about UK-based supermarket chain Morrisons is increasing their IT spend...OK, sounds good. Even nicer that Oracle is a big part of that. But what caught my eye were three things: 1) Morrison's truly has a long term strategy for IT. In this case, modernizing and optimizing how they use IT for business advantage.   2) Even in a tough economic climate, Morrison's views IT investments as contributing to and improving the bottom line. Specifically, "The investment in IT contributed to a 21 percent increase in Morrison's underlying profit.."   3) The phased, 3-year "Optimization Plan" took a holistic approach to their business--from CRM and Supply Chain systems to the underlying application infrastructure. On the infrastructure front, adopting a more flexible Service-Oriented Architecture enabled them to be more agile and adapt their business and Identity Management helped with sometimes mundane (but costly) issues like lost passwords and being able to document who has access to what.   Things don't always turn out so rosy. And I know it was a long and difficult process...but it's nice to see a happy ending every once in a while.  

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  • The spork/platypus average: shameless self promotion

    - by Roger Hart
    This is the video of presentation I gave at UA Europe and TCUK this year. The actual sub-title was "Content strategy at Red Gate Software", but this heading feels more honest. For anybody who missed it, or is just vaguely interested, here's a link to me talking about de-suckifying the web. You can find the slideshare deck here, too* Watching it back is more than a little embarrassing, and makes me really, really want to do a follow up, so I can do three things: explain the rest of the big web project, now we've done it give some data on the outcome of the content review make a grovelling apology to our marketing guys, who I've been unfairly mean to in a childish effort to look cool There are a whole bunch of other TCUK presentations online, too. You can find them all here: http://tiny.cc/tcuk10_videos I'd particularly recommend Chris Atherton's: "Everything you always wanted to know about psychology and technical communication" - it's full of cool stuff. You should probably also watch David Black's opening keynote, which managed to make my hour of precocious grandstanding look measured, meek, and helpful. He actually makes some interesting points, but you'd basically have to ship Richard Dawkins off to Utah, if you wanted to go further out of your way to aggravate your audience. It does give an engaging account of running a large tech comms project, and raise some questions about how we propose to understand a world where increasing amounts of our stuff gets done by increasingly many increasingly complicated tissues of APIs. Well, sort of. That's what all the notes I made were about, anyway.   *Slideshare ate my fonts. Just so we're clear on this: I'd never use badly-kerned Arial in a presentation. Don't worry.

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  • IT Optimization Plan Pays Off For UK Retailer

    - by [email protected]
    I caught this article in ComputerworldUK yesterday. The headline talks about UK-based supermarket chain Morrisons is increasing their IT spend...OK, sounds good. Even nicer that Oracle is a big part of that. But what caught my eye were three things: 1) Morrison's truly has a long term strategy for IT. In this case, modernizing and optimizing how they use IT for business advantage. 2) Even in a tough economic climate, Morrison's views IT investments as contributing to and improving the bottom line. Specifically, "The investment in IT contributed to a 21 percent increase in Morrison's underlying profit.." 3) The phased, 3-year "Optimization Plan" took a holistic approach to their business--from CRM and Supply Chain systems to the underlying application infrastructure. On the infrastructure front, adopting a more flexible Service-Oriented Architecture enabled them to be more agile and adapt their business and Identity Management helped with sometimes mundane (but costly) issues like lost passwords and being able to document who has access to what. Things don't always turn out so rosy. And I know it was a long and difficult process...but it's nice to see a happy ending every once in a while.

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  • Combining pathfinding with global AI objectives

    - by V_Programmer
    I'm making a turn-based strategy game using Java and LibGDX. Now I want to code the AI. I haven't written the AI code yet. I've simply designed it. The AI will have two components, one focused in tactics and resource management (create troops, determine who have strategical advantage, detect important objectives, etc) and a individual component, focused in assign the work to each unit, examine its possibilites and move the unit. Now I'm facing an important problem. The map where the action take place is a grid-based map. Each terrain has different movement cost. I read about pathfinding and I think A* is a very good option to determine a good route between two points. However, imagine I have an unit with movement = 5 (i.e, it can move 5 tiles of movement cost = 1). My tactical AI has found an objective at a distance d = 20 tiles (Manhattan distance) from my unit. My problem is the following: the unit won't be able to reach the objective in one turn. So the AI will have to store a list of position and execute them in various turns. I don't know how to solve this. PS. In my unit code, I have a list called "selectionMarks" which stores all the possible places where the unit can go in this turn. This places are calculed recursively using a "getSelectionMarks" function. Any help is appreciated :D

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  • Ad-hoc taxonomy: owning the chess set doesn't mean you decide how the little horsey moves

    - by Roger Hart
    There was one of those little laugh-or-cry moments recently when I heard an anecdote about content strategy failings at a major online retailer. The story goes a bit like this: successful company in a highly commoditized marketplace succeeds on price and largely ignores its content team. Being relatively entrepreneurial, the founders are still knocking around, and occasionally like to "take an interest". One day, they decree that clothing sold on the site can no longer be described as "unisex", because this sounds old fashioned. Sad now. Let me just reiterate for the folks at the back: large retailer, commoditized market place, differentiating on price. That's inherently unstable. Sooner or later, they're going to need one or both of competitive differentiation and significant optimization. I can't speak for the latter, since I'm hypothesizing off a raft of rumour, but one of the simpler paths to the former is to become - or rather acknowledge that they are - a content business. Regardless, they need highly-searchable terminology. Even in the face of tooth and claw resistance to noticing the fundamental position content occupies in driving sales (and SEO) on the web, there's a clear information problem here. Dilettante taxonomy is a disaster. Ok, so this is a small example, but that kind of makes it a good one. Unisex probably is the best way of describing clothing designed to suit either men or women interchangeably. It certainly takes less time to type (and read). It's established terminology, and as a single word, it's significantly better for web readability than a phrasal workaround. Something like "fits men or women" is short, by could fall foul of clause-level discard in web scanning. It's not an adjective, so for intuitive reading it's never going to be near the start of a title or description. It would also clutter up search results, and impose cognitive load in list scanning. Sorry kids, it's just worse. Even if "unisex" were an archaism (which it isn't), the only thing that would weigh against its being more usable and concise terminology would be evidence that this archaism were hurting conversions. Good luck with that. We once - briefly - called one of our products a "Can of worms". It was a bundle in a bug-tracking suite, and we thought it sounded terribly cool. Guess how well that sold. We have information and content professionals for a reason: to make sure that whatever we put in front of users is optimised to meet user and business goals. If that thinking doesn't inform style guides, taxonomy, messaging, title structure, and so forth, you might as well be finger painting.

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  • Strategy to allow emergency access to colocation crew

    - by itsadok
    I'm setting up a server at a new colocation center half way around the world. They installed the OS for me and sent me the root password, so there's obviously a great amount of trust in them. However, I'm pretty sure I don't want them to have my root password on a regular basis. And anyway, I intend to only allow key-based login. On some cases, though, it might be useful to let their technical support log in through a physical terminal. For example, if I somehow mess up the firewall settings. Should I even bother worrying about that? Should I set up a sudoer account with a one-time password that will change if I ever use it? Is there a common strategy for handling something like this?

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  • Online Backup strategy for family individuals

    - by marlon brando
    The majority of my family, including myself, uses Dropbox and Syncplicity free accounts for our syncing needs. However our backup strategy is pretty non-existent, we all have access (via webDav) to our qnap nas located at home, however we copy files accross when we can remember to do so, terrible I know. Is there tools like CrashPlan or Spideroak that allows each the accomodation of each family members syncing and back-up needs under one main account? I'm not sure how this would work, as each family member would need a seperate sub-account or would I manage each computer's syncing and backup lists from a single account? Any thoughts?

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  • Datacenter Backup Strategy

    - by EasyEcho
    What are common approaches to backup solutions in remote data centers? I am already familiar with general backup principals and have a very good backup strategy for our local data center but am having great difficulty extending it to a remote data center. We currently do a full backup on Friday, differential Mon - Thu, rotate offsite Friday morning ...rinse and repeat week after week. BTW, we use disks and have been very happy with this approach. We could buy a large storage server and backup everything to it, but this solution doesn't give you offsite. We could encrypt and upload to Amazon or some other online storage but that would take a large amount of time given the data and would be rather expensive paying for the bandwidth leaving the data center and receiving at amazon. We could drive to the data center every Friday and continue to rotate disks as we do now. But that just seems old fashion. What am I missing, are there better options?

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  • Advice for an EC2 Architecture and Deployment Strategy

    - by Mark
    My company is currently migrating several websites and PHP web applications (standard LAMP stack) from three in-house servers to Amazon EC2. Because we had only three servers, we clustered several low-traffic websites with perhaps one high-traffic web application, and served them from the same server. The server admin has pretty much copied the previous architecture wholesale onto the EC2 instances, simply upping the instance size to account for the highest traffic client that occupies that particular instance. This architecture might be okay if it wasn't for deployment. Any time one of these sites/apps changes, it means redeploying the entire instance, along with the 30 sites/apps it hosts, instead of just updating one. How can we architect our cloud in a more modular fashion? Should each app get its own appropriately-sized instance? What is the best strategy for deployment in this type of situation?

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  • AI to move custom-shaped spaceships (shape affecting movement behaviour)

    - by kaoD
    I'm designing a networked turn based 3D-6DOF space fleet combat strategy game which relies heavily on ship customization. Let me explain the game a bit, since you need to know a bit about it to set the question. What I aim for is the ability to create your own fleet of ships with custom shapes and attached modules (propellers, tractor beams...) which would give advantages and disadvantages to each ship, so you have lots of different fleet distributions. E.g., long ship with two propellers at the side would let the ship spin around that plane easily, bigger ships would move slowly unless you place lots of propellers at the back (therefore spending more "construction" points and energy when moving, and it will only move fast towards that direction.) I plan to balance all the game around this feature. The game would revolve around two phases: orders and combat phase. During the orders phase, you command the different ships. When all players finish the order phase, the combat phase begins and the ship orders get resolved in real-time for some time, then the action pauses and there's a new orders phase. The problem comes when I think about player input. To move a ship, you need to turn on or off different propellers if you want to steer, travel forward, brake, rotate in place... These propellers don't have to work at their whole power, so you can achieve more movement combinations with less propellers. I think this approach is a bit boring. The player doesn't want to fiddle with motors or anything, you just want to MOVE and KILL. The way I intend the player to give orders to these ships is by a destination and a rotation, and then the AI would calculate the correct propeller power to achive that movement and rotation. Propulsion doesn't have to be the same throught the entire turn calculation (after the orders have been given) so it would be cool if the ships reacted as they move, adjusting the power of the propellers for their needs dynamically, but it may be too hard to implement and it's not really needed for the game to work. In both cases, how would that AI decide which propellers to activate for the best (or at least not worst) trajectory to be achieved? I though about some approaches: Learning AI: The ship types would learn about their movement by trial and error, adjusting their behaviour with more uses, and finally becoming "smart". I don't want to get involved THAT far in AI coding, and I think it can be frustrating for the player (even if you can let it learn without playing.) Pre-calculated timestep movement: Upon ship creation, ALL possible movements are calculated for each propeller configuration and power for a given delta-time. Memory intensive, ugly, bad. Pre-calculated trajectories: The same as above but not for each delta-time but the whole trajectory, which would then be fitted as much as possible. Requires a fixed propeller configuration for the whole combat phase and is still memory intensive, ugly and bad. Continuous brute forcing: The AI continously checks ALL possible propeller configurations throughout the entire combat phase, precalculates a few time steps and decides which is the best one based on that. Con: what's good now might not be that good later, and it's too CPU intensive, ugly, and bad too. Single brute forcing: Same as above, but only brute forcing at the beginning of the simulation, so it needs constant propeller configuration throughout the entire combat phase. Coninuous angle check: This is not a full movement method, but maybe a way to discard "stupid" propeller configurations. Given the current propeller's normal vector and the final one, you can approximate the power needed for the propeller based on the angle. You must do this continuously throughout the whole combat phase. I figured this one out recently so I didn't put in too much thought. A priori, it has the "what's good now might not be that good later" drawback too, and it doesn't care about the other propellers which may act together to make a better propelling configuration. I'm really stuck here. Any ideas?

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  • Recommendation for a Strategy Game Engine for .NET?

    - by Fred F.
    Can anyone recommend a strategy game engine for the .net framework. I downloaded XNA, but it is way beyond my needs. I just want to create a turn based strategy game. I have searched and searched, but all I cannnot find any examples. I have asked for something similiar before, but have not gotten any good answers.

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  • iphone cache strategy

    - by venkat
    hi all i am new to cache strategy....i would like to know how to increase the loading speed of web pages in iphone application... using cache strategy...its fine to have a response with sample code.... advance thanks. with kind regards venkat

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  • Supporting users if they're not on your site

    - by Roger Hart
    Have a look at this Read Write Web article, specifically the paragraph in bold and the comments. Have a wry chuckle, or maybe weep for the future of humanity - your call. Then pause, and worry about information architecture. The short story: Read Write Web bumps up the Google rankings for "Facebook login" at the same time as Facebook makes UI changes, and a few hundred users get confused and leave comments on Read Write Web complaining about not being able to log in to their Facebook accounts.* Blindly clicking the first Google result is not a navigation behaviour I'd anticipated for folks visiting big names sites like Facebook. But then, I use Launchy and don't know where any of my files are, depend on Firefox auto-complete, view Facebook through my IM client, and don't need a map to find my backside with both hands. Not all our users behave in the same way, which means not all of our architecture is within our control, and people can get to your content in all sorts of ways. Even if the Read Write Web episode is a prank of some kind (there are, after all, plenty of folks who enjoy orchestrated trolling) it's still a useful reminder. Your users may take paths through and to your content you cannot control, and they are unlikely to deconstruct their assumptions along the way. I guess the meaningful question is: can you still support those users? If they get to you from Google instead of your front door, does what they find still make sense? Does your information architecture still work if your guests come in through the bathroom window? Ok, so here they broke into the house next door - you can't be expected to deal with that. But the rest is well worth thinking about. Other off-site interaction It's rarely going to be as funny as the comments at Read Write Web, but your users are going to do, say, and read things they think of as being about you and your products, in places you don't control. That's good. If you pay attention to it, you get data. Your users get a better experience. There are easy wins, too. Blogs, forums, social media &c. People may look for and find help with your product on blogs and forums, on Twitter, and what have you. They may learn about your brand in the same way. That's fine, it's an interaction you can be part of. It's time-consuming, certainly, but you have the option. You won't get a blogger to incorporate your site navigation just in case your users end up there, but you can be there when they do. Again, Anne Gentle, Gordon McLean and others have covered this in more depth than I could. Direct contact Sales people, customer care, support, they all talk to people. Are they sending links to your content? if so, which bits? Do they know about all of it? Do they have the content they need to support them - messaging that funnels sales, FAQ that are realistically frequent, detailed examples of things people want to do, that kind of thing. Are they sending links because users can't find the good stuff? Are they sending précis of your content, or re-writes, or brand new stuff? If so, does that mean your content isn't up to scratch, or that you've got content missing? Direct sales/care/support interactions are enormously valuable, and can help you know what content your users find useful. You can't have a table of contents or a "See also" in a phonecall, but your content strategy can support more interactions than browsing. *Passing observation about Facebook. For plenty if folks, it is  the internet. Its services are simple versions of what a lot of people use the internet for, and they're aggregated into one stop. Flickr, Vimeo, Wordpress, Twitter, LinkedIn, and all sorts of games, have Facebook doppelgangers that are not only friendlier to entry-level users, they're right there, behind only one layer of authentication. As such, it could own a lot of interaction convention. Heavy users may well not be tech-savvy, and be quite change averse. That doesn't make this episode not dumb, but I'm happy to go easy on 'em.

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  • techniques for an AI for a highly cramped turn-based tactics game

    - by Adam M.
    I'm trying to write an AI for a tactics game in the vein of Final Fantasy Tactics or Vandal Hearts. I can't change the game rules in any way, only upgrade the AI. I have experience programming AI for classic board games (basically minimax and its variants), but I think the branching factor is too great for the approach to be reasonable here. I'll describe the game and some current AI flaws that I'd like to fix. I'd like to hear ideas for applicable techniques. I'm a decent enough programmer, so I only need the ideas, not an implementation (though that's always appreciated). I'd rather not expend effort chasing (too many) dead ends, so although speculation and brainstorming are good and probably helpful, I'd prefer to hear from somebody with actual experience solving this kind of problem. For those who know it, the game is the land battle mini-game in Sid Meier's Pirates! (2004) and you can skim/skip the next two paragraphs. For those who don't, here's briefly how it works. The battle is turn-based and takes place on a 16x16 grid. There are three terrain types: clear (no hindrance), forest (hinders movement, ranged attacks, and sight), and rock (impassible, but does not hinder attacks or sight). The map is randomly generated with roughly equal amounts of each type of terrain. Because there are many rock and forest tiles, movement is typically very cramped. This is tactically important. The terrain is not flat; higher terrain gives minor bonuses. The terrain is known to both sides. The player is always the attacker and the AI is always the defender, so it's perfectly valid for the AI to set up a defensive position and just wait. The player wins by killing all defenders or by getting a unit to the city gates (a tile on the other side of the map). There are very few units on each side, usually 4-8. Because of this, it's crucial not to take damage without gaining some advantage from it. Units can take multiple actions per turn. All units on one side move before any units on the other side. Order of execution is important, and interleaving of actions between units is often useful. Units have melee and ranged attacks. Melee attacks vary widely in strength; ranged attacks have the same strength but vary in range. The main challenges I face are these: Lots of useful move combinations start with a "useless" move that gains no immediate advantage, or even loses advantage, in order to set up a powerful flank attack in the future. And, since the player units are stronger and have longer range, the AI pretty much always has to take some losses before they can start to gain kills. The AI must be able to look ahead to distinguish between sacrificial actions that provide a future benefit and those that don't. Because the terrain is so cramped, most of the tactics come down to achieving good positioning with multiple units that work together to defend an area. For instance, two defenders can often dominate a narrow pass by positioning themselves so an enemy unit attempting to pass must expose itself to a flank attack. But one defender in the same pass would be useless, and three units can defend a slightly larger pass. Etc. The AI should be able to figure out where the player must go to reach the city gates and how to best position its few units to cover the approaches, shifting, splitting, or combining them appropriately as the player moves. Because flank attacks are extremely deadly (and engineering flank attacks is key to the player strategy), the AI should be competent at moving its units so that they cover each other's flanks unless the sacrifice of a unit would give a substantial benefit. They should also be able to force flank attacks on players, for instance by threatening a unit from two different directions such that responding to one threat exposes the flank to the other. The AI should attack if possible, but sometimes there are no good ways to approach the player's position. In that case, the AI should be able to recognize this and set up a defensive position of its own. But the AI shouldn't be vulnerable to a trivial exploit where the player repeatedly opens and closes a hole in his defense and shoots at the AI as it approaches and retreats. That is, the AI should ideally be able to recognize that the player is capable of establishing a solid defense of an area, even if the defense is not currently in place. (I suppose if a good unit allocation algorithm existed, as needed for the second bullet point, the AI could run it on the player units to see where they could defend.) Because it's important to choose a good order of action and interleave actions between units, it's not as simple as just finding the best move for each unit in turn. All of these can be accomplished with a minimax search in theory, but the search space is too large, so specialized techniques are needed. I thought about techniques such as influence mapping, but I don't see how to use the technique to great effect. I thought about assigning goals to the units. This can help them work together in some limited way, and the problem of "how do I accomplish this goal?" is easier to solve than "how do I win this battle?", but assigning good goals is a hard problem in itself, because it requires knowing whether the goal is achievable and whether it's a good use of resources. So, does anyone have specific ideas for techniques that can help cleverize this AI? Update: I found a related question on Stackoverflow: http://stackoverflow.com/questions/3133273/ai-for-a-final-fantasy-tactics-like-game The selected answer gives a decent approach to choosing between alternative actions, but it doesn't seem to have much ability to look into the future and discern beneficial sacrifices from wasteful ones. It also focuses on a single unit at a time and it's not clear how it could be extended to support cooperation between units in defending or attacking.

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  • Effective backup and archive strategy for database and linked files

    - by busyspin
    I am using Postgres to store a variety of application data for a webapp. Part of the application involves storing and retrieving user uploaded files. I am storing the files in the filesystem with some associated metadata in the database. I am trying to come up with a backup and archive strategy so that I can effectively backup and archive/restore the database and the linked files. Here are the things I want to accomplish. Perform routine backups that can be used for recovery from failures and which include all DB data and the linked files. Ideally, this backup would be done while the app is running. Live backup is certainly possible with a DB but I am not sure how to keep the linked files consistent with the database during the backup process Archive chunks of data as they become "old". These chunks must includes the database data plus any linked files. It should be possible to put the archived data back into production again. It would be ideal if it were easy to determine which ranges of objects were stored in each chunk. Do you have any advice for how to accomplish these goals? If the files were in the database as BLOBS these tasks would be much easier since normal database backup and restore functionality would handle this. I am not sure how to accomplish the same thing when file data is linked to database rows.

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  • Strategy for Incremental Datasource fetchings in Excel

    - by user1352530
    I am in an scenario with a table that is refresh by a third app every week. I need to keep accumulating all data in Excel, using an ODBC connection to the database. I am wondering Approach 1: Is there a way to force Excel to append results for every update (this update would be triggered according to a parameter that indicates week)? I tried to define the table for which the connection loads using a dynamic reference but once is anchored first time, table position is never redefined Approach 2: Use an ETL to accumulate all weekly results into a staging table and then connect Excel to it in real time. But, I would need a mechanism for caching old data, as I cannot grow exponentially the time Excel opens. Imagine after 10 years, Excel would need to update at opening 10 years fo data before showing it. Is there a way to store already fetched data and increment it at real time (when book is opened) by selecting new data (with a query/filter of something) Thanks EDIT: Maybe it's better to ask it that way: What is the optimal strategy for a table that keeps growing and needs to be read in real time by Excel? I just don't want to fetch absolutely all data after some months...

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  • The type of field isn't supported by declared persistence strategy "OneToMany"

    - by Robert
    We are new to JPA and trying to setup a very simple one to many relationship where a pojo called Message can have a list of integer group id's defined by a join table called GROUP_ASSOC. Here is the DDL: CREATE TABLE "APP"."MESSAGE" ( "MESSAGE_ID" INTEGER NOT NULL GENERATED ALWAYS AS IDENTITY (START WITH 1, INCREMENT BY 1) ); ALTER TABLE "APP"."MESSAGE" ADD CONSTRAINT "MESSAGE_PK" PRIMARY KEY ("MESSAGE_ID"); CREATE TABLE "APP"."GROUP_ASSOC" ( "GROUP_ID" INTEGER NOT NULL, "MESSAGE_ID" INTEGER NOT NULL ); ALTER TABLE "APP"."GROUP_ASSOC" ADD CONSTRAINT "GROUP_ASSOC_PK" PRIMARY KEY ("MESSAGE_ID", "GROUP_ID"); ALTER TABLE "APP"."GROUP_ASSOC" ADD CONSTRAINT "GROUP_ASSOC_FK" FOREIGN KEY ("MESSAGE_ID") REFERENCES "APP"."MESSAGE" ("MESSAGE_ID"); Here is the pojo: @Entity @Table(name = "MESSAGE") public class Message { @Id @Column(name = "MESSAGE_ID") @GeneratedValue(strategy = GenerationType.IDENTITY) private int messageId; @OneToMany(fetch=FetchType.LAZY, cascade=CascadeType.PERSIST) private List groupIds; public int getMessageId() { return messageId; } public void setMessageId(int messageId) { this.messageId = messageId; } public List getGroupIds() { return groupIds; } public void setGroupIds(List groupIds) { this.groupIds = groupIds; } } When we try to execute the following test code we get <openjpa-1.2.3-SNAPSHOT-r422266:907835 fatal user error> org.apache.openjpa.util.MetaDataException: The type of field "pojo.Message.groupIds" isn't supported by declared persistence strategy "OneToMany". Please choose a different strategy. Message msg = new Message(); List groups = new ArrayList(); groups.add(101); groups.add(102); EntityManager em = Persistence.createEntityManagerFactory("TestDBWeb").createEntityManager(); em.getTransaction().begin(); em.persist(msg); em.getTransaction().commit(); Help!

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  • Strategy Pattern with Type Reflection affecting Performances ?

    - by Aurélien Ribon
    Hello ! I am building graphs. A graph consists of nodes linked each other with links (indeed my dear). In order to assign a given behavior to each node, I implemented the strategy pattern. class Node { public BaseNodeBehavior Behavior {get; set;} } As a result, in many parts of the application, I am extensively using type reflection to know which behavior a node is. if (node.Behavior is NodeDataOutputBehavior) workOnOutputNode(node) .... My graph can get thousands of nodes. Is type reflection greatly affecting performances ? Should I use something else than the strategy pattern ? I'm using strategy because I need behavior inheritance. For example, basically, a behavior can be Data or Operator, a Data behavior can IO, Const or Intermediate and finally an IO behavior can be Input or Output. So if I use an enumeration, I wont be able to test for a node behavior to be of data kind, I will need to test it to be [Input, Output, Const or Intermediate]. And if later I want to add another behavior of Data kind, I'm screwed, every data-testing method will need to be changed.

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  • Communication with different social networks, strategy pattern?

    - by bclaessens
    Hi For the last few days I've been thinking how I can solve the following programming problem and find the ideal, flexible programming structure. (note: I'm using Flash as my platform technology but that shouldn't matter since I'm just looking for the ideal design pattern). Our Flash website has multiple situations in which it has to communicate with different social networks (Facebook, Netlog and Skyrock). Now, the communication strategy doesn't have to change multiple times over one "run". The strategy should be picked once (at launch time) for that session. The real problem is the way the communication works between each social network and our website. Some networks force us to ask for a token, others force us to use a webservice, yet another forces us to set up its communication through javascript. The problem becomes more complicated when our website has to run in each network's canvas. Which results in even more (different) ways of communicating. To sum up, our website has to work in the following cases: standalone on the campaign website url (user chooses their favourite network) communicate with netlog OR communicate with facebook OR communicate with skyrock run in a netlog canvas and log in automatically (website checks for netlog parameters) run in a facebook canvas and log in automatically (website checks for facebook params) run in a skyrock canvas and log in automatically (website checks for skyrock params) As you can see, our website needs 6 different ways to communicate with a social network. To be honest, the actual significant difference between all communication strategies is the way they have to connect to their individual network (as stated above in my example). Posting an image, make a comment, ... is the same whether it runs standalone or in the canvas url. WARNING: posting an image, posting a comment DOES differ from network to network. Should I use the strategy pattern and make 6 different communication strategies or is there a better way? An example would be great but isn't required ;) Thanks in advance

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  • Simple Backup Strategy for Amazon EC2 instances / volumes?

    - by minerj
    You have entered Introductory Backups for Amazon EC2 EBS-backed Windows Images 010... I have been browsing my brains out to find a simple backup strategy for our single windows 2008 server running SharePoint Services. This is an EBS-backed image of one server with one data volume. I don’t need anything exotic. I only need a “daily” backup (losing a day’s worth of data is not catastrophic). We have created and saved an EBS backed AMI image (Windows 2008) we are comfortable using. We started off making backups by simply creating a new EBS AMI image. This is really simple, but the running server is put offline during the first 10 – 15 minutes of creating the image – not ideal. The standard way of creating backups would seem to be creating snapshots of volumes attached to a running instance. Again it’s pretty simple and the server remains usable during the snapshot generation. The apparent Catch-22 is that you can’t simply launch a new instance directly from a snapshot. I know how to bundle a running instance to S3 storage and then register the AMI from the S3 bucket. This does allow me to capture a backup of a running instance and, if the running instance is lost, register the AMI from the S3 bucket and launch the new AMI to recover the instance, but this seems really convoluted and it seems ridiculous to have to juggle back and forth between the AWS Console and the S3 Organizer plug-in for Firefox to get this accomplished. (Please don't mention the command line approach, this is an 010 level course). From playing around with EBS-backed images, the following approach appears to work for me (all done within the AWS Console): 1.For your backups, simply snapshot the system volume (/dev/sda1) as needed. 2.If you lose your running instance, do the following: a.Create a new volume from your last snapshot backup b.Launch another instance of your starting AMI (must be EBS-backed) c.Stop this instance. d.Detach the existing system volume from the new stopped instance and discard. e.Attach the newly created volume as system volume (/dev/sda1) to the stopped instance. f.Re-start the new instance. I have tested this out a couple of times and it seems to work for me. Question: Is there anything wrong with this approach?

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