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  • How to reserve a set of primary key identifiers for preloading bootstrap data

    - by Joshua
    We would like to reserve a set of primary key identifiers for all tables (e.g. 1-1000) so that we can bootstrap the system with pre-loaded system data. All our JPA entity classes have the following definition for the primary key. @Id @GeneratedValue(strategy = IDENTITY) @Column(name = "id", unique = true, nullable = false, insertable = false, updatable = false) private Integer id; is there a way to tell the database that increments should start happening from 1000 (i.e. customer specific data will start from 1000 onwards). We support (h2, mysql, postgres) in our environment and I would prefer a solution which can be driven via JPA and reverse engineering DDL tools from Hibernate. Let me know if this is the correct approach

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  • n elements in singly linked list

    - by Codenotguru
    The following function is trying to find the nth to last element of a singly linked list. for ex: if the elements are 8-10-5-7-2-1-5-4-10-10 then the result is 7th to last node is 7. Can anybody help me on how this code is working or is there a better and simpler approach? LinkedListNode nthToLast(LinkedListNode head, int n) { if (head == null || n < 1) { return null; } LinkedListNode p1 = head; LinkedListNode p2 = head; for (int j = 0; j < n - 1; ++j) { // skip n-1 steps ahead if (p2 == null) { return null; // not found since list size < n } p2 = p2.next; } while (p2.next != null) { p1 = p1.next; p2 = p2.next; } return p1; }

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  • Clear all class variables between instances

    - by ensnare
    This is probably a stupid question, but what's the best way to clear class variables between instances? I know I could reset each variable individually in the constructor; but is there a way to do this in bulk? Or am I doing something totally wrong that requires a different approach? Thanks for helping ... class User(): def __init__(self): #RESET ALL CLASS VARIABLES def commit(self): #Commit variables to database >>u = User() >>u.name = 'Jason' >>u.email = '[email protected]' >>u.commit() So that each time User is called the variables are fresh. Thanks.

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  • How to setup a webserver in common lisp?

    - by Serpico
    Several months ago, I was inspired by the magnificent book ANSI Common Lisp written by Paul Graham, and the statement that Lisp could be used as a secret weapon in your web development, published by the same author on his blog. Wow, that is amazing. That is something that I have been looking for long time. The author really developed a successful web applcation and sold it to Yahoo. With those encouraging images, I determined to spend some time (1 year or 2 year, who knows) on learning Common Lisp. Maybe someday I will development my web application and turn into a great Lisp expert. In fact, this is the second time for me to get to study Lisp. The first time was a couple of years ago when I was fascinated by the famous book SICP but found later Scheme was so unbelievably immature for real life application. After reading some chapters of ANSI Common Lisp, I was pretty sure that is a great book full of detailed exploration of Common Lisp. Then I began to set up a web server in Common Lisp. After all, this should be the best way if you want to learn something. Demonstrations are always better than definations. As suggested by the book Practical Common Lisp (by the way, this is also a great book), I chose to install AllegroServe on some Common Lisp implementation. Then, from somewhere else, I learned that Hunchentoot seems to be better than AllegroServe. (I don't remember where and whom this word is from. So don't argue with me.) Ironically, you know what, I never could installed the two packages on any Common Lisp implementation. More annoyingly, I even don't know why. The machine always spit up a lot of jargon and lead me into a chaos. I've tried searching the internet and have not found anything. Could anybody who has successfully installed these packages in Linux tell me how you did it? Have you run into any trouble? How did you figured out what is wrong and fixed it? The more detailed, the more helpful.

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  • Mapping A Sphere To A Cube

    - by petrocket
    There is a special way of mapping a cube to a sphere described here: http://mathproofs.blogspot.com/2005/07/mapping-cube-to-sphere.html It is not your basic "normalize the point and your done" approach and gives a much more evenly spaced mapping. I've tried to do the inverse of the mapping going from sphere coords to cube coords and have been unable to come up the working equations. It's a rather complex system of equations with lots of square roots. Any math geniuses want to take a crack at it? Here's the equations in c++ code: sx = x * sqrtf(1.0f - y * y * 0.5f - z * z * 0.5f + y * y * z * z / 3.0f); sy = y * sqrtf(1.0f - z * z * 0.5f - x * x * 0.5f + z * z * x * x / 3.0f); sz = z * sqrtf(1.0f - x * x * 0.5f - y * y * 0.5f + x * x * y * y / 3.0f); sx,sy,sz are the sphere coords and x,y,z are the cube coords.

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  • Unique Key in MySql

    - by Vinodtiru
    I have a table with four Columns. Col1, Col2, Col3, and Col4. Col1, Col2, Col3 is string and Col4 is a integer primary key with Auto Increment. Now my requirement is to have unique combination of Col2 and Col3. I mean to say like. Insert into table(Col1,Col2,Col3) Values('val1','val2','val3'); Insert into table(Col1,Col2,Col3) Values('val4','val2','val3'); the second statement has to throw error as the same combination of 'val2','val3' is present in the table. But i cant make it as a primary key as i need a auto increment column and for that matter the col4 has to be primary. Please let me know a approach by which i can have both in my table. Any kind of help is appreciated. Thanks.

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  • MonoRail - Select parent category from one dropdown, show child category dropdown

    - by Justin
    Hey, I'm new to MonoRail and am trying to figure out how to have it so that I can select a parent category in a dropdown then have it show a second dropdown with the categories that are children of the parent. If I were using what I'm used to, ASP.NET MVC, I would have a javascript function that would be called onchange of the first dropdown and would make an ajax call to a controller method (passing in the selected parent category id) that would grab all child categories of that parent category and return them in JSON. Then in the callback javascript function I would eval the JSON and populate the second dropdown with the child categories. How would I do this using MonoRail/jQuery? Here's the code I have so far: $FormHelper.Select("business.category.id", $categories, "%{value='id', text='name', firstoption='Select a Category'}") $FormHelper.Select("business.category.id", $childCategories, "%{value='id', text='name', firstoption='Select a Sub-Category'}") Then in BusinessController.cs: private void AddDataToModels() { PropertyBag["categories"] = CategoryRepository.GetParentCategories(); PropertyBag["childCategories"] = CategoryRepository.GetChildCategories(1); } Thanks for any input on how to approach this! Justin

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  • Anyone has implemented SMA* search algorithm?

    - by Endy
    I find the algorithm description in AIMA (Artificial Intelligence: A Modern Approach) is not correct at all. What does 'necessary' mean? What is the memory limit? The queue size or processed nodes? What if the current node has no children at all? I am wondering if this algorithm itself is correct or not. Because I searched the Internet and nobody has implemented it yet. Thanks.

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  • Silverlight layout Best Practices

    - by JustSmith
    I'm writing a fairly big interface using Silverlight. As I progress, the xaml file is getting fairly big and is becoming proportionally uglier. Questions Are there any resources out there to make the xaml more readable? For example, how would I display the order of attributes (e.g. height and Width first) so that it looks the most tidy? Another issue is that there are multiple ways to implement an interface with grids and stack panels. Is there a preferred approach when using one or the other? I am looking for advice and links to other resources that can be used as examples.

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  • How to create empty folders with maven archetype?

    - by chrsk
    There is an existing issue for this approach, located on Codehaus JIRA #ARCHETYPE-57, but all instructions listed in this ticket failed for me. Also the blog post of marekdec How to get maven archetype to generate empty directories fails for me. The trick within the archetype.xml with the trailing / doesnt works for me: <resources> <resource>src/main/webapp/</resource> Unable to find resource 'archetype-resources/src/main/webapp/' Also the fileSet directory in archetype-metadata.xml does not work for me: <fileSet filtered="true" encoding="UTF-8"> <directory>src/main/webapp/</directory> </fileSet> Is there any other solution? Or did i miss something? Thanks

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  • How to keep views free of authorization logic in mvc?

    - by David Lay
    I have a view to display a list of items. The user can edit, delete or create new items, but according to their authorizations they may or may not be allowed to do some of this actions. I have the requirement to display only the actions which the current user is allowed to do, but I don't want to clutter the views with authorization if-else's Despise of being a very common requirement, I can't find a real satisfactory way of doing it. My best approach so far is to provide an overload to the Html.ActionLink extension method that takes the permission to ask for, but there are going to be more complex scenarios, like hiding entire blocks of html or switching a textbox for a label+hidden. Is there a better way to do this?

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  • e-shop implementation: Status for Orders?

    - by Guillermo
    Hello Again my fellow programmers out there, I'm designing and programming from scratch a online shop. It has a Module to manage "Orders" that are recieved via the frontend. I'm needing to have a status to know whats happening with an order in s certain moment, let's say the statuses are: Pending Payment Confirmed - Awaiting shipment Shipped Cancelled My question is a simple one, but is very important to decide on the store design, and is: What would you do so store this status: Would you create a column for it in the Orders table or would you just "calculate" the status of each order depending if payments has been recieved or shipments has been made for every order? (except I suppose for a is_cancelled column) What would be the best approach to model this kind of problem? PD: I even wish in the future to have these statuses configurable buy other clientes using the same software..

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  • GpsSatellite.getSnr() - What is the value range?

    - by rflexor
    I'm building a Sat-View that draws a small bar-chart for available satellites and their signal strength (or better: their signal-to-noise-ratio / SNR). The javadoc doesn't say what value-range to expect for the SNR. The NMEA-Standard says 0-99, but even in best conditions my G1 doesn't reach that value. I also read that different manufacturers use different value-ranges for the SNR, so is that true for android-devices, too? Or is there a unified value range on that plattform and if so, what is it? The lack of information in the docs leads me to suspect I just get the "raw" SNR from the driver, in which case I'd like to know: What do you think is the best approach to visualize that unknown value-range in a bar-chart?

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  • Ruby email_veracity_checker getting Recipient OK for invalid emails

    - by digger69
    I was testing out email_veracity_checker from rails console and found that when I tested a google apps domain (w/ catchall), yahoo and another company domain, the smtp server always returned 250 recipient ok for invalid emails (wellformed, but bogus). It seems that these servers are always returning OK perhaps to prevent email harvesting. But it does seem to raise the question 'why even validate up-front', is this approach even valid in today's environment? Note: gmail did return 550 email account doesn't exist for invalid. related to How check if an email exist without send in Ruby? Use of email_veracity_checker send-in-ruby-use-of-email-veracity-checker I appreciate your thoughts.

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  • Objective-C assigning variables question for iphone.

    - by coder net
    The following piece of code can be written in two ways. I would like to know what are the pros and cons of each. If possible I would like to stick with the one liner. 1) UIColor *background = [[UIColor alloc] initWithPatternImage:[UIImage imageNamed:@"Background.png"]]; self.view.backgroundColor = background; [background release]; 2) self.view.backgroundColor = [[UIColor alloc] initWithPatternImage:[UIImage imageNamed:@"Background.png"]]; Any issues with releasing memory etc. with #2? I'm new to Objective-C and would like to follow the best approach.

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  • How to secure Java webservices with login and session handling

    - by hubertg
    I'd like to secure my (Java metro) webservice with a login. Here's how I'm planning to do that: Steps required when calling a webservice method are: call login(user,pwd), receive a session token 1.1 remember the token call servicemethod (token, arg1, arg2...) webservice checks if the token is known, if not throw exception otherwise proceed logout or timeout after x time periods of inactivity my questions: 1. what's your opinion on this approach? does it make sense? 2. are there any libraries which take the burden of writing a session handling (maybe with database persistence to survive app restarts) (the solution should be simple and easily usable with Java and .NET clients) thanks!

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  • Normalize or Denormalize in high traffic websites

    - by Inam Jameel
    what is the best practice for database design for high traffic websites like this one stackoverflow? should one must use normalize database for record keeping or normalized technique or combination of both? is it sensible to design normalize database as main database for record keeping to reduce redundancy and at the same time maintain another denormalized form of database for fast searching? or main database should be denormalize and one can make normalized views in the application level for fast database operations? or beside above mentioned approach? what is the best practice of designing high traffic websites???

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  • Current ways to do data binding in .NET 3.5 with C# 3.0 and WinForms

    - by kryptic
    Hello Everyone, I have an existing C# 3.0 WinForms project with .NET 3.5 that talks to a MySQL database. I would like to use data binding (I'm new to this, so I've been doing all of the UI updates manually) to simplify things. I followed a link from this question to this article which mentions using a DataSet but also follows up with "my view on this topic is strongly in favor of Business Objects." Also that was with .NET 2.0. What are the current methods to use data binding with a WinForms application? What are their advantages in terms of simplicity, how much additional code is necessary, etc. For reference, I use an ORM approach to build objects with public properties from a database. I want to map these properties for each object onto UI elements like TextBoxes. There could be many properties for an object so I want to simplify the code to do this.

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  • How would you go about tackling this problem?

    - by incrediman
    I have a programming contest coming up in about half a week, and I've been prepping :) I found a bunch of questions from this canadian competition, they're great practice: http://cemc.math.uwaterloo.ca/contests/computing/2009/stage2/day1.pdf I'm looking at problem B ("Dinner"). Any idea where to start? I can't really think of anything besides the naive approach (ie. trying all permutations) which would take too long to be a valid answer. Btw, the language there says c++ and pascal I think, but i don't care what language you use - I mean really all I want is a brief description of how to tackle the problem. Like "use X technique treating each programmer as a Y" or something :)

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  • How to find the longest continuous subsequence whose reverse is also a subsequence

    - by iecut
    Suppose I have a sequence x1,x2,x3.....xn, and I want to find the longest continuous subsequence xi,xi+1,xi+2......xi+k, whose reverse is also a subsequence of the given sequence. And if there are multiple such subsequences, then I also have to find the first. ex:- consider the sequences: abcdefgedcg here i=3 and k=2 aabcdddd here i=5, k=3 I tried looking at the original longest common subsequence problem, but that is used to compare the two sequences to find the longest common subsequence.... but here is only one sequence from which we have to find the subsequences. Please let me know what is the best way to approach this problem, to find the optimal solution.

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  • Strategy Design Pattern -- *dynamic* !!!

    - by alexeypro
    My application will have different strategies for my objects. What's the best way of implementing that? I would really love the case when we can make strategy classes implementation dynamically loaded from, say, some relational database. Not sure how do that better, though. What's the best approach? Idea is that say we want to apply to object MyObj strategy Strategy123 then we just load from database by ID 123 the object, deserialize it, get the Strategy class, and use it with MyObj. The maintenance while sounds easier from the first look can be a pain in the long run if Strategy interfaces changes, etc. What can I do also? I want to find solution when I should be keeping Strategy classes in codebase -- just for the sake that I don't need code change and re-deployment of the application if my Strategy changes, or I add new strategy. Please advise!

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  • effective retrieve for a voting system in PHP and MySQL

    - by Adnan
    Hello, I have a system where registered users can vote up/vote down comment for a picture. Something very similar to SO's voting system. I store the votes in a table with values as such; vote_id | vote_comment_id | vote_user_id | vote_date | vote_type Now I have few a question concerned the speed and efficiency for the following; PROB: Once a user opens the picture page with comments I need, if that user has already voted UP/DOWN a comment to show it like; "you voted up" or "you voted down" next to the comment (in SO it the vote image is highlighted) MY POSSIBLE SOL: Right now when I open a picture page for each comment I loop thru, I loop thru my table of votes as well and check if a user has voted and show the status (I compare the vote_user_id with the user's session). How efficient is this? Anyone have a better approach to tackle this kind of problem?

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  • TDD and encapsulation priority conflict

    - by Hanseh
    Hi, I just started practicing TDD in my projects. I'm developing a project now using php/zend/mysql and phpunit/dbunit for testing. I'm just a bit distracted on the idea of encapsulation and the test driven approach. My idea behind encapsulation is to hide access to several object functionalities. To make it more clear, private and protected functions are not directly testable(unless you will create a public function to call it). So I end up converting some private and protected functions to public functions just to be able to test them. I'm really violating the principles of encapsulation to give way to micro function testability. Is this the correct way of doing it?

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  • Strategies to use Database Sequences?

    - by Bruno Brant
    Hello all, I have a high-end architecture which receives many requests every second (in fact, it can receive many requests every millisecond). The architecture is designed so that some controls rely on a certain unique id assigned to each request. To create such UID we use a DB2 Sequence. Right now I already understand that this approach is flawed, since using the database is costly, but it makes sense to do so because this value will also be used to log information on the database. My team has just found out an increase of almost 1000% in elapsed time for each transaction, which we are assuming happened because of the sequence. Now I wonder, using sequences will serialize access to my application? Since they have to guarantee that increments works the way they should, they have to, right? So, are there better strategies when using sequences? Please assume that I have no other way of obtaining a unique id other than relying on the database.

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  • how to display a dialog if user can't download file

    - by tom smith
    hi. dealing with php/html/javascript. i'm trying to figure out a good/best approach to allowing a user to download a file. i can have the traditional href link, that interfaces with the back end php app to download the file. however, i want to have the app display some sort of dialog/alert if the user isn't able (basedon acl/permissions) to download the file... does this have to ba an ajax thing, as i don't want to do a page refresh... thoughts/comments/pointers to code samples are appreciated. thanks. -tom

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