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• How to keep historic details of modification in a database (Audit trail)?

  - by mada

  I'm a J2EE developer & we are using hibernate mapping with a PostgreSQL database. We have to keep track of any changes occurs in the database, in others words all previous & current values of any field should be saved. Each field can be any type (bytea, int, char...) With a simple table it is easy but we a graph of objects things are more difficult. So we have, speaking in a UML point of view, a graph of objects to store in the database with every changes & the user. Any idea or pattern how to do that?

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• How can I match at the beginning of any line, including the first, with a Perl regex?

  - by JoelFan

  According the the Perl documentation on regexes: By default, the "^" character is guaranteed to match only the beginning of the string ... Embedded newlines will not be matched by "^" ... You may, however, wish to treat a string as a multi-line buffer, such that the "^" will match after any newline within the string ... you can do this by using the /m modifier on the pattern match operator. The "after any newline" part means that it will only match at the beginning of the 2nd and subsequent lines. What if I want to match at the beginning of any line (1st, 2nd, etc.)? EDIT: OK, it seems that the file has BOM information (3 chars) at the beginning and that's what's messing me up. Any way to get ^ to match anyway? EDIT: So in the end it works (as long as there's no BOM), but now it seems that the Perl documentation is wrong, since it says "after any newline"

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• Twitter date unparseable?

  - by Andreas

  Hi, I want to convert the date string in a Twitter response to a Date object, but I always get a ParseException and I cannot see the error!?! Input string: Thu Dec 23 18:26:07 +0000 2010 SimpleDateFormat Pattern: EEE MMM dd HH:mm:ss ZZZZZ yyyy Method: public static Date getTwitterDate(String date) { SimpleDateFormat sf = new SimpleDateFormat(TWITTER); sf.setLenient(true); Date twitterDate = null; try { twitterDate = sf.parse(date); } catch (Exception e) {} return twitterDate; } I also tried this: http://friendpaste.com/2IaKdlT3Zat4ANwdAhxAmZ but that gives the same result. I use Java 1.6 on Mac OS X. Cheers, Andi

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• Scraping paginated items from a website using scrapy

  - by Mridang Agarwalla

  I'm using scrapy to scrape items from a site. I'm not being able to implement this scraping pattern. The site I'm trying to scrape is a forum and I scrape the site once a day. Each page has a table containing posts. New posts are added to the top of the table and as more and more posts are posted to the site, the older posts go further into the pages due to pagination. This is a very simple scenario and we will assume that the order of the posts never change. I would like to scrape this site and scrape all the "new" records until the last scraped post from yesterday is encountered. I have configured my spider to paginate endlessly and when it encounters yesterday's last scraped post, it should stop. How can implement this? (My Scrapy installation works with my Django installation using django-dynamic-scraper )

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• Assigning an @Annotation enum a value

  - by h2g2java

  I created enum Restrictions{ none, enumeration, fractionDigits, length, maxExclusive, maxInclusive, maxLength, minExclusive, minInclusive, minLength, pattern, totalDigits, whiteSpace; public Restrictions setValue(int value){ this.value = value; return this; } public int value; } So that I could happily do something like this, which is perfectly legal syntax. Restrictions r1 = Restrictions.maxLength.setValue(64); The reason being is, I am using enum to restrict the type of restriction that could be used, and be able to assign a value to that restriction. However, my actual motivation is to use that restriction in an @annotation. @Retention(RetentionPolicy.RUNTIME) @Target({ElementType.TYPE, ElementType.FIELD, ElementType.METHOD}) public @interface Presentable { Restrictions[] restrictions() default Restrictions.none; } So that, I intended to do this: @Presentable(restrictions=Restrictions.maxLength.setValue(64)) public String userName; to which, the compiler croaks The value for annotation enum attribute must be an enum constant expression. Is there a way to accomplish what I wish to accomplish

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• Immutability of big objects

  - by Malax

  Hi StackOverflow! I have some big (more than 3 fields) Objects which can and should be immutable. Every time I run into that case i tend to create constructor abominations with long parameter lists. It doesn't feel right, is hard to use and readability suffers. It is even worse if the fields are some sort of collection type like lists. A simple addSibling(S s) would ease the object creation so much but renders the object mutable. What do you guys use in such cases? I'm on Scala and Java, but i think the problem is language agnostic as long as the language is object oriented. Solutions I can think of: "Constructor abominations with long parameter lists" The Builder Pattern Thanks for your input!

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• How to transfer binary data through multiple http server?

  - by solotim

  Well, the question is not intended to be that big. Let me explain the scenario: I have two http servers. server A is accessible to end user by web browser, while server B is internal server which can only be accessed by server A. If server B generate some big jpeg image in local disk, obviously we can't just delivery those path to image to server A and eventually to end user. Then, how to let end user see those image without firstly storing those image data in server A temporarily? I run PHP on server A and perl on server B, but this should not matter. I need a general pattern for implementing this.

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• How to create new account using servlets

  - by Alvin

  I want to know how can I create new account using servlets in post method? I'm currently following MVC design pattern, and I want to know if I pass the required data to register new account from JSP page, then how can I get that data in post method? As request.getParameter() method returning me null. How can I know that post method is calling to create new account? How can I pass all the relevant user information from servlets to model class for registering data to the database table?

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• Linq to SQL EntitySet Records causing duplicate insertion

  - by Savvas Sopiadis

  In a WPF application i'm using Linq to SQL in a multi tier application. (This is an archailogy photo filing application), so every excavation has its corresponding Pictures, thus a one-to-many relationship. This relationship is correctly created by SQLMetal (which i'm using to create the POCOs). So here is the situation i 'm having trouble with: Saving changes (either of new or altered objects) is done through UnitOfWork() pattern this way: using (IUnitOfWork unitOfWork = UnitOfWork.Begin()) { //if this is a new record if (SelectedExcavation.excavation.ExcavationId == 0) { IsNewRecord = true; excavService.Add(SelectedExcavation.excavation); } //send the actual changes to the dbms unitOfWork.Commit(); } Everything works fine! BUTTTT!!! Whenever a record gets updated which has (already at least one ) corresponding Picture Record: 1) a new Excavation Record is inserted 2) the current Excavation Record gets updated 3) the previous Picture Record gets its Id changed to the newly created ExcavationId What is going on under the hood? Does Linq to SQL not handle such simple update scenarios? Thanks in advance

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• Is there any benefit to declaring a private property with a getter and setter?

  - by AmoebaMan17

  I am reviewing another developer's code and he has written a lot of code for class level variables that is similar to the following: /// <summary> /// how often to check for messages /// </summary> private int CheckForMessagesMilliSeconds { get; set; } /// <summary> /// application path /// </summary> private string AppPath { get; set; } Doesn't coding this way add unnecessary overhead since the variable is private? Am I not considering a situation where this pattern of coding is required for private variables?

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• How can I see what capybara found in a failing cucumber step?

  - by ajmurmann

  I started migrating from cucumber + webrat to cucumber + capybara. Now the behavior of "I should see " seems to be somewhat different. Most of these fail now, although I didn't change anything on the page. I replaced the snippet that should be found with some stuff that is on every page and for some text it works and for other text it doesn't. I can't find any pattern in what is found in the page's content and what is not. Webrat used to print what the page content is that it found, in case it did not contain the required phrase. Is there anyway to have capybara show what text it got from the page in which it tried to find the text?

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• Rails Full Engine using a Full Engine

  - by SirLenz0rlot

  I've got this full rails engine Foo with functionality X. I want to make another engine, engine Bar, that is pretty much the same, but override funcitonality x with y. (it basically does the same, but a few controller actions and views are differently implemented). (I might split this later in several mountable engines, but for now, this will be the setup: project Baz, using engine Bar, which uses engine Foo) I would like to know if there are any pitfalls. It doesn't seem like a pattern that is often used? Anybody else using this 'some sort of engine inheritance'?

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• creative way for implementing Data object with it's corespanding buisness logic class in java

  - by ekeren

  I have a class that need to be serialized (for both persistentcy and client-server communication) for simplicity reasons lets call the classes Business a BusinessData and I prefix for their Interfaces. All the getter and setter are delegated from Business class to BusinessData class. I thought about implementing IBusinessData interface that will contain all the getter and setters and IBusiness interface that will extend it. I can either make Business extend BuisnessData so I will not need to implement all getter and setter delegates, or make some abstract class ForwardingBusinessData that will only delegate getter and setters. Any of the above option I loose my hierarchy freedom, does any of you have any creative solution for this problem... I also reviewed DAO pattern: http://java.sun.com/blueprints/patterns/DAO.html

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• Problem with assigning elements of a class array to individual variables in MATLAB

  - by Marc

  This is a bit of a duplicate of this question, this question, and this question, however those solutions don't work, so I'm asking mine. I've got an array of locally defined classes and I'd like to assign it to multiple, individual variables. This pattern doesn't work: %a is 2x1 of MyClass temp = mat2cell(a); [x,y] = temp{:}; %throws: ??? Insufficient number of outputs from right hand side of equal sign to satisfy assignment. Because temp is a single cell, with my 2x1 array in one cell, rather than a 2x1 cell array with one element of each of my original array in one cell. Any ideas?

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• modrewrite RewriteRule problem

  - by timpone

  I am using Apache 2.2 and mod_rewrite. I would like to take the following urls and map them to another url. The pattern is simple and like this: http://domain/test/ex1.html - http://domain/app/index.php/content/?name=ex1 I tried the following in an .htaccess file: RewriteEngine On RewriteBase /app/ RewriteRule (.*)\.html index.php/content/?name=$1 and RewriteEngine On RewriteRule (.*)\.html /app/index.php/content/?name=$1 I wasn't sure if the backreference was correct so set to $0 and $2 but never seemed to help. I also tried setting the RewriteLogLevel to 9. There is a step where it is almost there: rewrite 'ex1.html' - 'index.php/content/?name=ex1' The last line of the rewrite log is as follows: [perdir /var/www/domain/htdocs/test/] internal redirect with /app/index.php/content/ [INTERNAL REDIRECT] How can I get this to rewrite to /app/index.php/content/?name=ex1 ? thanks

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• javascript: execute a bunch of asynchronous method with one callback

  - by Samuel Michelot

  I need to execute a bunch of asynchronous methods (client SQLite database), and call only one final callback. Of course, the ugly way is: execAll : function(callBack) { asynch1(function() { asynch2(function() { ... asynchN(function() { callBack(); }) }) }); } But I know there are better ways to do it. Intuitively I would detect when all call back has been called with a counter to call the final callback. I think this is a common design-pattern, so if someone could point me in the right direction... Thanks in advance !

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• Loading textures in an Android OpenGL ES App.

  - by Omega

  I was wondering if anyone could advise on a good pattern for loading textures in an Android Java & OpenGL ES app. My first concern is determining how many texture names to allocate and how I can efficiently go about doing this prior to rendering my vertices. My second concern is in loading the textures, I have to infer the texture to be loaded based on my game data. This means I'll be playing around with strings, which I understand is something I really shouldn't be doing in my GL thread. Overall I understand what's happening when loading textures, I just want to get the best lifecycle out of it. Are there any other things I should be considering?

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• ASP.NET 4.0 webforms routing

  - by Ethan

  I have an existing site that I'd like to convert to use routing, and after reading Scott Guthrie's post here, I built a working sample that works for most circumstances. However, since not all of the pages on the existing site match a particular pattern, I'll need to check against a database to determine which route (destination .aspx page) to use. For example, most pages are like this: http://www.mysite.com/people/person.html This is fine - I can easily route these to the view_person.aspx page because of the 'people' directory. But some pages are like this: http://www.mysite.com/category_page.html http://www.mysite.com/product_page.html This necessitates checking the database to see whether to route to the view_category.aspx page or the view_product.aspx page. And this is where I'm stuck. Do I create an IRouteHandler that checks the database and returns the route? Or is there a better way? The only code I've found that kind of fits is the answer to this question. Thanks in advance.

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• Can you use data binding with the Content property of a WPF Frame?

  - by dthrasher

  I can use data binding to set the initial Content of a WPF Frame, but subsequent changes to the the bound property (implemented using INotifyPropertyChange) do not seem to change the content. Also, does anyone know if binding directly to the Content property in this way will cause the bound item to appear in the Frame or NavigationWindow's journal? Some context: I realize that I should probably be using the NavigationService to interact with the Frame, but I'm attempting to follow the MVVM pattern. It seems like it would be much simpler to databind to the Content property...

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• How to access File over the Network

  - by Polo

  Hi! I am having a hard time on this one, I have a folder over the network with public access (no credential restriction). I am trying to do a File.Exist or Directory.Exist and I keep on having a exception. Can someone tell me the good way to do IO over the network. EDIT 1 FOR DETAILS: if i do execture = \agoodip\Public\test.txt I get the file etc etc In my code it look like a basic Directory.Exist(@"\\agoodip\Public") or File.exist(@"\\agoodip\Public\test.txt") The exception I get is Path not found. EDIT 2 : I am using Silverlight 3, Is there any security pattern to be aware of to lookup file on the network? Thanks!

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• Image reflection in Silverlight 4

  - by Phani Kumar PV

  I am developing a product scrolling feature where products info( product image, Name, price)will be shown side by side horizontally. i need to show the image of the product and also its reflection. under the reflected image i need to show the Prod Name and its price. The problem here is i dont want to show the complete reflected image. the oputput should be something like this Image Height-100% Reflected Image Height-20% Product name Product Price The above pattern will repeat horizontally. I am able to get the desired output with some problem. The reflected image is shown up with hieght 100% and the sapce between the actual image and product name is very high. My reflected image should be a rotated image of the actual image and only half part of the actual image should be shown. Any pointers even is highly appreciated

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• which regular expression will capture this sequence?

  - by John Smith

  The text follows this pattern <tr class="text" (any sequence of characters here, except ABC)ABC(any sequence of characters here, except ABC) <tr class="text" (any sequence of characters here, except ABC)ABC(any sequence of characters here, except ABC) <tr class="text" (any sequence of characters here, except ABC)ABC(any sequence of characters here, except ABC) <tr class="text" (any sequence of characters here, except ABC)ABC(any sequence of characters here, except ABC) so basically the above line might repeat itself multiple times, and the idea is to retrieve the first 3 characters immediately after ABC. I have tried regular expressions along the lines of \<tr class="text" [.]+ABC(?<capture>[.]{3}) but they all fail. Can someone give me a hint?

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• Customizing UISlider look

  - by tcurdt

  To customize the visual look of a UISlider you can set the thumb and track images. Part of the track images gets stretched to the appropriate with. From the documentation: A stretchable region sits between two end cap regions. The end caps define the portions of the image that remain as is and are not stretched. The stretchable region is a 1-point wide area between the end caps that can be replicated to make the image appear longer. Now the problem I have is that my stretchable region needs to be more than 1-point wide. (It's a pattern) Unfortunately the 1-point width seems to be hard coded in the SDK. Anyone having an idea how to work around this? Or will I have to write my own slider from scratch for this?

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• what happens to running/blocked runnables when executorservice is shutdown()

  - by prmatta

  I posted a question about a thread pattern today, and almost everyone suggested that I look into the ExecutorService. While I was looking into the ExecutorService, I think I am missing something. What happens if the service has a running or blocked threads, and someone calls ExecutorService.shutdown(). What happens to threads that are running or blocked? Does the ExecutorService wait for those threads to complete before it terminates? The reason I ask this is because a long time ago when I used to dabble in Java, they deprecated Thread.stop(), and I remember the right way of stopping a thread was to use sempahores and extend Thread when necessary: public void run () { while (!this.exit) { try { block(); //do something } catch (InterruptedException ie) { } } } public void stop () { this.exit = true; if (this.thread != null) { this.thread.interrupt(); this.thread = null; } } How does ExecutorService handle running threads?

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• GUI system architecture?

  - by topright

  I'm designing GUI (graphical user interface) system for a game engine (C++). Idea is to create a heirarchy of GUI controllers like Focusable, Hoverable, Dragable etc. Every GUI component can attach multiple controllers, they modify component's behaviour. I think it gives flexible system and protects from code duplication. Different instances of the same GUI class can have different complex behaviours (may be, even change it dynamically), so this approach looks practical. The other choice is to add focused, hovered, dragged etc. flags in the base GUI component class. It looks like overhead and not that flexible. Another solution is to use Decorator pattern and wrap objects with FocusDecorator, HoverDecorator etc. Maintaining such system looks a bit harder. Question: What are pitfalls in my solution? May be you have seen a better approaches in GUI systems? What are the best ways of implementing such flexible complex system?

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