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  • Is this kind of design - a class for Operations On Object - correct?

    - by Mithir
    In our system we have many complex operations which involve many validations and DB activities. One of the main Business functionality could have been designed better. In short, there were no separation of layers, and the code would only work from the scenario in which it was first designed at, and now there were more scenarios (like requests from an API or from other devices) So I had to redesign. I found myself moving all the DB code to objects which acts like Business to DB objects, and I've put all the business logic in an Operator kind of a class, which I've implemented like this: First, I created an object which will hold all the information needed for the operation let's call it InformationObject. Then I created an OperatorObject which will take the InformationObject as a parameter and act on it. The OperatorObject should activate different objects and validate or check for existence or any scenario in which the business logic is compromised and then make the operation according to the information on the InformationObject. So my question is - Is this kind of implementation correct? PS, this Operator only works on a single Business-wise Operation.

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  • class hierarchy design for small java project

    - by user523956
    I have written a java code which does following:- Main goal is to fetch emails from (inbox, spam) folders and store them in database. It fetches emails from gmail,gmx,web.de,yahoo and Hotmail. Following attributes are stored in mysql database. Slno, messagedigest, messageid, foldername, dateandtime, receiver, sender, subject, cc, size and emlfile. For gmail,gmy and web.de, I have used javamail API, because email form it can be fetched with IMAP. For yahoo and hotmail, I have used html parser and httpclient to fetch emails form spam folder and for inbox folder, I have used pop3 javamail API. I want to have proper class hierarchy which makes my code efficient and easily reusable. As of now I have designed class hierarchy as below: I am sure it can still be improved. So I would like to have different opinions on it. I have following classes and methods as of now. MainController:- Here I pass emailid, password and foldername from which emails have to be fetched. Abstract Class :-EmailProtocol Abstract Methods of it (All methods except executeParser contains method definition):- connectImap() // used by gmx,gmail and web.de email ids connectPop3() // used by hotmail and yahoo to fetch emails of inbox folder createMessageDigest // used by every email provider(gmx, gmail,web.de,yahoo,hotmail) establishDBConnection // used by every email emailAlreadyExists // used by every email which checks whether email already exists in db or not, if not then store it. storeemailproperties // used by every email to store emails properties to mysql database executeParser // nothing written in it. Overwridden and used by just hotmail and yahoo to fetch emails form spam folder. Imap extends EmailProtocol (nothing in it. But I have to have it to access methods of EmailProtocol. This is used to fetch emails from gmail,gmx and web.de) I know this is really a bad way but don't know how to do it other way. Hotmsil extends EmailProtocol Methods:- executeParser() :- This is used by just hotmail email id. fetchjunkemails() :- This is also very specific for only hotmail email id. Yahoo extends EmailProtocol Methods:- executeParser() storeEmailtotemptable() MoveEmailtoInbox() getFoldername() nullorEquals() All above methods are specific for yahoo email id. public DateTimeFormat(class) format() //this formats datetime of gmax,gmail and web.de emails. formatYahoodate //this formats datetime of yahoo email. formatHotmaildate // this formats datetime of hotmail email. public StringFormat ConvertStreamToString() // Accessed by every class except DateTimeFormat class. formatFromTo() // Accessed by every class except DateTimeFormat class. public Class CheckDatabaseExistance public static void checkForDatabaseTablesAvailability() (This method checks at the beginnning whether database and required tables exist in mysql or not. if not it creates them) Please see code of my MainController class so that You can have an idea about how I use different classes. public class MainController { public static void main(String[] args) throws Exception { ArrayList<String> web_de_folders = new ArrayList<String>(); web_de_folders.add("INBOX"); web_de_folders.add("Unbekannt"); web_de_folders.add("Spam"); web_de_folders.add("OUTBOX"); web_de_folders.add("SENT"); web_de_folders.add("DRAFTS"); web_de_folders.add("TRASH"); web_de_folders.add("Trash"); ArrayList<String> gmx_folders = new ArrayList<String>(); gmx_folders.add("INBOX"); gmx_folders.add("Archiv"); gmx_folders.add("Entwürfe"); gmx_folders.add("Gelöscht"); gmx_folders.add("Gesendet"); gmx_folders.add("Spamverdacht"); gmx_folders.add("Trash"); ArrayList<String> gmail_folders = new ArrayList<String>(); gmail_folders.add("Inbox"); gmail_folders.add("[Google Mail]/Spam"); gmail_folders.add("[Google Mail]/Trash"); gmail_folders.add("[Google Mail]/Sent Mail"); ArrayList<String> pop3_folders = new ArrayList<String>(); pop3_folders.add("INBOX"); CheckDatabaseExistance.checkForDatabaseTablesAvailability(); EmailProtocol imap = new Imap(); System.out.println("CHECKING FOR NEW EMAILS IN WEB.DE...(IMAP)"); System.out.println("*********************************************************************************"); imap.connectImap("[email protected]", "pwd", web_de_folders); System.out.println("\nCHECKING FOR NEW EMAILS IN GMX.DE...(IMAP)"); System.out.println("*********************************************************************************"); imap.connectImap("[email protected]", "pwd", gmx_folders); System.out.println("\nCHECKING FOR NEW EMAILS IN GMAIL...(IMAP)"); System.out.println("*********************************************************************************"); imap.connectImap("[email protected]", "pwd", gmail_folders); EmailProtocol yahoo = new Yahoo(); Yahoo y=new Yahoo(); System.out.println("\nEXECUTING YAHOO PARSER"); System.out.println("*********************************************************************************"); y.executeParser("http://de.mc1321.mail.yahoo.com/mc/welcome?ymv=0","[email protected]","pwd"); System.out.println("\nCHECKING FOR NEW EMAILS IN INBOX OF YAHOO (POP3)"); System.out.println("*********************************************************************************"); yahoo.connectPop3("[email protected]","pwd",pop3_folders); System.out.println("\nCHECKING FOR NEW EMAILS IN INBOX OF HOTMAIL (POP3)"); System.out.println("*********************************************************************************"); yahoo.connectPop3("[email protected]","pwd",pop3_folders); EmailProtocol hotmail = new Hotmail(); Hotmail h=new Hotmail(); System.out.println("\nEXECUTING HOTMAIL PARSER"); System.out.println("*********************************************************************************"); h.executeParser("https://login.live.com/ppsecure/post.srf","[email protected]","pwd"); } } I have kept DatetimeFormat and StringFormat class public so that I can access its public methods by just (DatetimeFormat.formatYahoodate for e.g. from different methods). This is the first time I have developed something in java. It serves its purpose but of course code is still not so efficient I think. I need your suggestions on this project.

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  • Design Pattern for Social Game Mission Mechanics

    - by Furkan ÇALISKAN
    When we want to design a mission sub-system like in the The Ville or Sims Social, what kind of design pattern / idea would fit the best? There may be relation between missions (first do this then this etc...) or not. What do you think sims social or the ville or any other social games is using for this? I'm looking for a best-practise method to contruct a mission framework for tha game. How the well-known game firms do this stuff for their large scale social facebook games? Giving missions to the players and wait players to complete them. when they finished the missions, providing a method to catch this mission complete events considering large user database by not using server-side not so much to prevent high-traffic / resource consumption. how should i design the database and server-client communication to achive this design condidering this trade-off.

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  • Design patterns: when to use and when to stop doing everything using patterns

    - by honeybadger
    This question arises due to comment of FredOverflow in my previous post. Design pattern used in projects I am quite confused by the comment. I know design pattern help in making code reusable and readable (may lack in efficiency a bit). But when to use design patterns and most importantly when to stop doing everything using patterns or carried away by it ? Any comments from you will be helpful. tagging programing languages too to cover broader audience.

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  • So, "Are Design Patterns Missing Language Features"?

    - by Eduard Florinescu
    I saw the answer to this question: How does thinking on design patterns and OOP practices change in dynamic and weakly-typed languages? There it is a link to an article with an outspoken title: Are Design Patterns Missing Language Features. But where you can get snippets that seem very objective and factual and that can be verified from experience like: PaulGraham said "Peter Norvig found that 16 of the 23 patterns in Design Patterns were 'invisible or simpler' in Lisp." and a thing that confirms what I recently seen with people trying to simulate classes in javascript: Of course, nobody ever speaks of the "function" pattern, or the "class" pattern, or numerous other things that we take for granted because most languages provide them as built-in features. OTOH, programmers in a purely PrototypeOrientedLanguage? might well find it convenient to simulate classes with prototypes... I am taking into consideration also that design patterns are a communcation tool and because even with my limited experience participating in building applications I can see as an anti-pattern(ineffective and/or counterproductive) for example forcing a small PHP team to learn GoF patterns for small to medium intranet app, I am aware that scale, scope and purpose can determine what is effective and/or productive. I saw small commercial applications that mixed functional with OOP and still be maintainable, and I don't know if many would need for example in python to write a singleton but for me a simple module does the thing. patterns So are there studies or hands on experience shared that takes into consideration, all this, scale and scope of project, dynamics and size of the team, languages and technologies, so that you don't feel that a (difficult for some)design pattern is there just because there isn't a simpler way to do it or that it cannot be done by a language feature?

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  • New book in the style of Advanced Programming Language Design by R. A. Finkel [closed]

    - by mfellner
    I am currently researching visual programming language design for a university paper and came across Advanced Programming Language Design by Raphael A. Finkel from 1996. Other, older discussions in the same vein on Stackoverflow have mentioned Language Implementation Patterns by Terence Parr and Programming Language Pragmatics* by Michael L. Scott. I was wondering if there is even more (and especially up-to-date) literature on the general topic of programming language design. *) http://www.cs.rochester.edu/~scott/pragmatics/

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  • Does TDD lead to the good design?

    - by Eugen Martynov
    I'm in transition from "writing unit tests" state to TDD. I saw as Johannes Brodwall creates quite acceptable design from avoiding any of architecture phase before. I'll ask him soon if it was real improvisation or he had some thoughts upfront. I also clearly understand that everyone has experience that prevents to write explicit design bad patterns. But after participating in code retreat I hardly believe that writing test first could save us from mistakes. But I also believe that tests after code will lead to mistakes much faster. So this night question is asking for people who is using TDD for a long time share their experience about results of design without upfront thinking. If they really practice it and get mostly suitable design. Or it's my small understanding about TDD and probably agile.

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  • Good resources for language design

    - by Aaron Digulla
    There are lots of books about good web design, UI design, etc. With the advent of Xtext, it's very simple to write your own language. What are good books and resources about language design? I'm not looking for a book about compiler building (like the dragon book) but something that answers: How to create a grammar that is forgiving (like adding optional trailing commas)? Which grammar patterns cause problems for users of a language? How create a compact grammar without introducing ambiguities

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  • Design Patterns and their most common uses for them [closed]

    - by cable729
    Possible Duplicate: What are some programming design patterns that are useful in game development? As I'm returning to game dev, I've realized that I've lost a lot of the knowledge I had before. So now I'm looking at design patterns that I can use for my next project. One design pattern that I've seen a lot is the 'composition method,' which uses actors and components. Is that the right name for it? I'd like to look more at this and see what the advantages/pitfalls are. So what design patterns are out there, and what are the advantages/disadvantages to them?

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  • How to explain why design choices are good?

    - by Telastyn
    As I've become a better developer, I find that much of my design skill comes more from intuition than mechanical analysis. This is great. It lets me read code and get a feel for it quicker. It lets me translate designs between languages and abstractions much easier. And it let's me get stuff done faster. The downside is that I find it harder to explain to teammates (and worse, management) why a particular design is advantageous; especially teammates that are behind the times on best practices. "This design is more testable!" or "You should favor composition over inheritance." go right over their heads, and lead into the rabbit hole of me trying to clue everyone in to the last decade of software engineering advances. I'll get better at it with practice of course, but in the mean time it involves a lot of wasted time and/or bad design (that will lead to wasted time fixing it later). How can I better explain why a certain design is superior, when the benefits aren't completely obvious to the audience?

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  • Help with MVC design pattern?

    - by user3681240
    I am trying to build a java program for user login but I am not sure if my MVC design is accurate. I have the following classes: LoginControl - servlet LoginBean - data holder java class with private variables getters and setters LoginDAO - concrete java class where I am running my SQL queries and doing rest of the logical work. Connection class - java class just to connect to the database view - jsp to display the results html - used for form Is this how you design a java program based on MVC design pattern? Please provide some suggestions?

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  • New to Java and Spring. What are some good design principles for an inexperienced java developer like me?

    - by Imtiaz Ahmad
    I am learning Java and have written a few small useful programs. I am new to spring but have managed to understand the concept of dependency injection for decoupling. I'm trying to applying that in my development work in an enterprise setting. What are the 3 most important design patterns I should master (not for interview purposes but ones that I will use every day in as a good java developer)? Also what are some good java design considerations and practices in coding specifically in Java? My goal is write good decoupled and coherent programs that are easy to maintain that don't make me standout as a java rookie. Stuff like not beginning my package names with com. have already made me precariously visible in my team. But they know I have 2 years of coding experience and its not in java.

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  • Recommended design pattern for object with optional and modifiable attributtes? [on hold]

    - by Ikuzen
    I've been using the Builder pattern to create objects with a large number of attributes, where most of them are optional. But up until now, I've defined them as final, as recommended by Joshua Block and other authors, and haven't needed to change their values. I am wondering what should I do though if I need a class with a substantial number of optional but non-final (mutable) attributes? My Builder pattern code looks like this: public class Example { //All possible parameters (optional or not) private final int param1; private final int param2; //Builder class public static class Builder { private final int param1; //Required parameters private int param2 = 0; //Optional parameters - initialized to default //Builder constructor public Builder (int param1) { this.param1 = param1; } //Setter-like methods for optional parameters public Builder param2(int value) { param2 = value; return this; } //build() method public Example build() { return new Example(this); } } //Private constructor private Example(Builder builder) { param1 = builder.param1; param2 = builder.param2; } } Can I just remove the final keyword from the declaration to be able to access the attributes externally (through normal setters, for example)? Or is there a creational pattern that allows optional but non-final attributes that would be better suited in this case?

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  • Why can't we capture the design of software more effectively?

    - by Ira Baxter
    As engineers, we all "design" artifacts (buildings, programs, circuits, molecules...). That's an activity (design-the-verb) that produces some kind of result (design-the-noun). I think we all agree that design-the-noun is a different entity than the artifact itself. A key activity in the software business (indeed, in any business where the resulting product artifact needs to be enhanced) is to understand the "design (the-noun)". Yet we seem, as a community, to be pretty much complete failures at recording it, as evidenced by the amount of effort people put into rediscovering facts about their code base. Ask somebody to show you the design of their code and see what you get. I think of a design for software as having: An explicit specification for what the software is supposed to do and how well it does it An explicit version of the code (this part is easy, everybody has it) An explanation for how each part of the code serves to achieve the specification A rationale as to why the code is the way it is (e.g., why a particualr choice rather than another) What is NOT a design is a particular perspective on the code. For example [not to pick specifically on] UML diagrams are not designs. Rather, they are properties you can derive from the code, or arguably, properties you wish you could derive from the code. But as a general rule, you can't derive the code from UML. Why is it that after 50+ years of building software, why don't we have regular ways to express this? My personal opinion is that we don't have good ways to express this. Even if we do, most of the community seems so focused on getting "code" that design-the-noun gets lost anyway. (IMHO, until design becomes the purpose of engineering, with the artifact extracted from the design, we're not going to get around this). What have you seen as means for recording designs (in the sense I have described it)? Explicit references to papers would be good. Why do you think specific and general means have not been succesful? How can we change this?

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  • (Database Design - products attributes): What is better option for product attribute database design

    - by meyosef
    Hi, I new in database design. What is better option for product attribute database design for cms?(Please suggest other options also). option 1: 1 table products{ id product_name color price attribute_name1 attribute_value1 attribute_name2 attribute_value2 attribute_name3 attribute_value3 } option 2: 3 tables products{ id product_name color price } attribute{ id name value } products_attribute{ products_id attribute_id } Thanks, Yosef

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  • What are the software design essentials? [closed]

    - by Craig Schwarze
    I've decided to create a 1 page "cheat sheet" of essential software design principles for my programmers. It doesn't explain the principles in any great depth, but is simply there as a reference and a reminder. Here's what I've come up with - I would welcome your comments. What have I left out? What have I explained poorly? What is there that shouldn't be? Basic Design Principles The Principle of Least Surprise – your solution should be obvious, predictable and consistent. Keep It Simple Stupid (KISS) - the simplest solution is usually the best one. You Ain’t Gonna Need It (YAGNI) - create a solution for the current problem rather than what might happen in the future. Don’t Repeat Yourself (DRY) - rigorously remove duplication from your design and code. Advanced Design Principles Program to an interface, not an implementation – Don’t declare variables to be of a particular concrete class. Rather, declare them to an interface, and instantiate them using a creational pattern. Favour composition over inheritance – Don’t overuse inheritance. In most cases, rich behaviour is best added by instantiating objects, rather than inheriting from classes. Strive for loosely coupled designs – Minimise the interdependencies between objects. They should be able to interact with minimal knowledge of each other via small, tightly defined interfaces. Principle of Least Knowledge – Also called the “Law of Demeter”, and is colloquially summarised as “Only talk to your friends”. Specifically, a method in an object should only invoke methods on the object itself, objects passed as a parameter to the method, any object the method creates, any components of the object. SOLID Design Principles Single Responsibility Principle – Each class should have one well defined purpose, and only one reason to change. This reduces the fragility of your code, and makes it much more maintainable. Open/Close Principle – A class should be open to extension, but closed to modification. In practice, this means extracting the code that is most likely to change to another class, and then injecting it as required via an appropriate pattern. Liskov Substitution Principle – Subtypes must be substitutable for their base types. Essentially, get your inheritance right. In the classic example, type square should not inherit from type rectangle, as they have different properties (you can independently set the sides of a rectangle). Instead, both should inherit from type shape. Interface Segregation Principle – Clients should not be forced to depend upon methods they do not use. Don’t have fat interfaces, rather split them up into smaller, behaviour centric interfaces. Dependency Inversion Principle – There are two parts to this principle: High-level modules should not depend on low-level modules. Both should depend on abstractions. Abstractions should not depend on details. Details should depend on abstractions. In modern development, this is often handled by an IoC (Inversion of Control) container.

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  • NullReferenceException when changing skin/theme via Application.Current.Resources

    - by CoolCat
    I am writing an wpf application with multiple skins. The code to switch theme is as below: try { Application.Current.Resources.MergedDictionaries.Add( resource ); } catch( Exception ex ) { } The first time the code is called (to switch to a new theme), it is executed successfully; however, any subsequent calls to the same code would throw System.NullReferenceException. The way I set up my themes are similar to what described here: http://www.codewrecks.com/blog/index.php/2008/05/22/simple-skinnable-and-theme-management-in-wpf-user-interface/. Has anyone seen this error before? How do I go about debugging this since the exception is thrown else where? Any help is greatly appreciated. StackTrace: at System.Windows.EffectiveValueEntry.GetFlattenedEntry(RequestFlags requests) at System.Windows.DependencyObject.EvaluateEffectiveValue(EntryIndex entryIndex, DependencyProperty dp, PropertyMetadata metadata, EffectiveValueEntry oldEntry, EffectiveValueEntry newEntry, OperationType operationType) at System.Windows.DependencyObject.UpdateEffectiveValue(EntryIndex entryIndex, DependencyProperty dp, PropertyMetadata metadata, EffectiveValueEntry oldEntry, EffectiveValueEntry& newEntry, Boolean coerceWithDeferredReference, OperationType operationType) at System.Windows.StyleHelper.ApplyStyleOrTemplateValue(FrameworkObject fo, DependencyProperty dp) at System.Windows.StyleHelper.InvalidateContainerDependents(DependencyObject container, FrugalStructList`1& exclusionContainerDependents, FrugalStructList`1& oldContainerDependents, FrugalStructList`1& newContainerDependents) at System.Windows.StyleHelper.DoStyleInvalidations(FrameworkElement fe, FrameworkContentElement fce, Style oldStyle, Style newStyle) at System.Windows.StyleHelper.UpdateStyleCache(FrameworkElement fe, FrameworkContentElement fce, Style oldStyle, Style newStyle, Style& styleCache) at System.Windows.FrameworkElement.OnStyleChanged(DependencyObject d, DependencyPropertyChangedEventArgs e) at System.Windows.DependencyObject.OnPropertyChanged(DependencyPropertyChangedEventArgs e) at System.Windows.FrameworkElement.OnPropertyChanged(DependencyPropertyChangedEventArgs e) at System.Windows.DependencyObject.NotifyPropertyChange(DependencyPropertyChangedEventArgs args) at System.Windows.DependencyObject.UpdateEffectiveValue(EntryIndex entryIndex, DependencyProperty dp, PropertyMetadata metadata, EffectiveValueEntry oldEntry, EffectiveValueEntry& newEntry, Boolean coerceWithDeferredReference, OperationType operationType) at System.Windows.DependencyObject.InvalidateProperty(DependencyProperty dp) at System.Windows.FrameworkElement.UpdateStyleProperty() at System.Windows.TreeWalkHelper.InvalidateStyleAndReferences(DependencyObject d, ResourcesChangeInfo info, Boolean containsTypeOfKey) at System.Windows.TreeWalkHelper.OnResourcesChanged(DependencyObject d, ResourcesChangeInfo info, Boolean raiseResourceChangedEvent) at System.Windows.TreeWalkHelper.OnResourcesChangedCallback(DependencyObject d, ResourcesChangeInfo info) at System.Windows.DescendentsWalker`1._VisitNode(DependencyObject d) at System.Windows.DescendentsWalker`1.VisitNode(FrameworkElement fe) at System.Windows.DescendentsWalker`1.VisitNode(DependencyObject d) at System.Windows.DescendentsWalker`1.WalkLogicalChildren(FrameworkElement feParent, FrameworkContentElement fceParent, IEnumerator logicalChildren) at System.Windows.DescendentsWalker`1.WalkFrameworkElementLogicalThenVisualChildren(FrameworkElement feParent, Boolean hasLogicalChildren) at System.Windows.DescendentsWalker`1.IterateChildren(DependencyObject d) at System.Windows.DescendentsWalker`1._VisitNode(DependencyObject d) at System.Windows.DescendentsWalker`1.VisitNode(FrameworkElement fe) at System.Windows.DescendentsWalker`1.VisitNode(DependencyObject d) at System.Windows.DescendentsWalker`1.WalkLogicalChildren(FrameworkElement feParent, FrameworkContentElement fceParent, IEnumerator logicalChildren) at System.Windows.DescendentsWalker`1.WalkFrameworkElementLogicalThenVisualChildren(FrameworkElement feParent, Boolean hasLogicalChildren) at System.Windows.DescendentsWalker`1.IterateChildren(DependencyObject d) at System.Windows.DescendentsWalker`1._VisitNode(DependencyObject d) at System.Windows.DescendentsWalker`1.VisitNode(FrameworkElement fe) at System.Windows.DescendentsWalker`1.VisitNode(DependencyObject d) at System.Windows.DescendentsWalker`1.WalkLogicalChildren(FrameworkElement feParent, FrameworkContentElement fceParent, IEnumerator logicalChildren) at System.Windows.DescendentsWalker`1.WalkFrameworkElementLogicalThenVisualChildren(FrameworkElement feParent, Boolean hasLogicalChildren) at System.Windows.DescendentsWalker`1.IterateChildren(DependencyObject d) at System.Windows.DescendentsWalker`1._VisitNode(DependencyObject d) at System.Windows.DescendentsWalker`1.VisitNode(FrameworkElement fe) at System.Windows.DescendentsWalker`1.VisitNode(DependencyObject d) at System.Windows.DescendentsWalker`1.WalkLogicalChildren(FrameworkElement feParent, FrameworkContentElement fceParent, IEnumerator logicalChildren) at System.Windows.DescendentsWalker`1.WalkFrameworkElementLogicalThenVisualChildren(FrameworkElement feParent, Boolean hasLogicalChildren) at System.Windows.DescendentsWalker`1.IterateChildren(DependencyObject d) at System.Windows.DescendentsWalker`1._VisitNode(DependencyObject d) at System.Windows.DescendentsWalker`1.VisitNode(FrameworkElement fe) at System.Windows.DescendentsWalker`1.VisitNode(DependencyObject d) at System.Windows.DescendentsWalker`1.WalkFrameworkElementLogicalThenVisualChildren(FrameworkElement feParent, Boolean hasLogicalChildren) at System.Windows.DescendentsWalker`1.IterateChildren(DependencyObject d) at System.Windows.DescendentsWalker`1._VisitNode(DependencyObject d) at System.Windows.DescendentsWalker`1.VisitNode(FrameworkElement fe) at System.Windows.DescendentsWalker`1.VisitNode(DependencyObject d) at System.Windows.DescendentsWalker`1.WalkLogicalChildren(FrameworkElement feParent, FrameworkContentElement fceParent, IEnumerator logicalChildren) at System.Windows.DescendentsWalker`1.WalkFrameworkElementLogicalThenVisualChildren(FrameworkElement feParent, Boolean hasLogicalChildren) at System.Windows.DescendentsWalker`1.IterateChildren(DependencyObject d) at System.Windows.DescendentsWalker`1._VisitNode(DependencyObject d) at System.Windows.DescendentsWalker`1.VisitNode(FrameworkElement fe) at System.Windows.DescendentsWalker`1.VisitNode(DependencyObject d) at System.Windows.DescendentsWalker`1.WalkLogicalChildren(FrameworkElement feParent, FrameworkContentElement fceParent, IEnumerator logicalChildren) at System.Windows.DescendentsWalker`1.WalkFrameworkElementLogicalThenVisualChildren(FrameworkElement feParent, Boolean hasLogicalChildren) at System.Windows.DescendentsWalker`1.IterateChildren(DependencyObject d) at System.Windows.DescendentsWalker`1._VisitNode(DependencyObject d) at System.Windows.DescendentsWalker`1.VisitNode(FrameworkElement fe) at System.Windows.DescendentsWalker`1.VisitNode(DependencyObject d) at System.Windows.DescendentsWalker`1.WalkLogicalChildren(FrameworkElement feParent, FrameworkContentElement fceParent, IEnumerator logicalChildren) at System.Windows.DescendentsWalker`1.WalkFrameworkElementLogicalThenVisualChildren(FrameworkElement feParent, Boolean hasLogicalChildren) at System.Windows.DescendentsWalker`1.IterateChildren(DependencyObject d) at System.Windows.DescendentsWalker`1._VisitNode(DependencyObject d) at System.Windows.DescendentsWalker`1.VisitNode(FrameworkElement fe) at System.Windows.DescendentsWalker`1.VisitNode(DependencyObject d) at System.Windows.DescendentsWalker`1.WalkLogicalChildren(FrameworkElement feParent, FrameworkContentElement fceParent, IEnumerator logicalChildren) at System.Windows.DescendentsWalker`1.WalkFrameworkElementLogicalThenVisualChildren(FrameworkElement feParent, Boolean hasLogicalChildren) at System.Windows.DescendentsWalker`1.IterateChildren(DependencyObject d) at System.Windows.DescendentsWalker`1._VisitNode(DependencyObject d) at System.Windows.DescendentsWalker`1.VisitNode(FrameworkElement fe) at System.Windows.DescendentsWalker`1.VisitNode(DependencyObject d) at System.Windows.DescendentsWalker`1.WalkLogicalChildren(FrameworkElement feParent, FrameworkContentElement fceParent, IEnumerator logicalChildren) at System.Windows.DescendentsWalker`1.WalkFrameworkElementLogicalThenVisualChildren(FrameworkElement feParent, Boolean hasLogicalChildren) at System.Windows.DescendentsWalker`1.IterateChildren(DependencyObject d) at System.Windows.DescendentsWalker`1.StartWalk(DependencyObject startNode, Boolean skipStartNode) at System.Windows.TreeWalkHelper.InvalidateOnResourcesChange(FrameworkElement fe, FrameworkContentElement fce, ResourcesChangeInfo info) at System.Windows.Application.InvalidateResourceReferenceOnWindowCollection(WindowCollection wc, ResourcesChangeInfo info) at System.Windows.ResourceDictionary.NotifyOwners(ResourcesChangeInfo info) at System.Windows.ResourceDictionary.OnMergedDictionariesChanged(Object sender, NotifyCollectionChangedEventArgs e) at System.Collections.ObjectModel.ObservableCollection`1.OnCollectionChanged(NotifyCollectionChangedEventArgs e) at System.Collections.ObjectModel.ObservableCollection`1.InsertItem(Int32 index, T item) at System.Windows.ResourceDictionaryCollection.InsertItem(Int32 index, ResourceDictionary item) at System.Collections.ObjectModel.Collection`1.Add(T item)

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  • Design patterns for Agent / Actor based concurrent design.

    - by nso1
    Recently i have been getting into alternative languages that support an actor/agent/shared nothing architecture - ie. scala, clojure etc (clojure also supports shared state). So far most of the documentation that I have read focus around the intro level. What I am looking for is more advanced documentation along the gang of four but instead shared nothing based. Why ? It helps to grok the change in design thinking. Simple examples are easy, but in a real world java application (single threaded) you can have object graphs with 1000's of members with complex relationships. But with agent based concurrency development it introduces a whole new set of ideas to comprehend when designing large systems. ie. Agent granularity - how much state should one agent manage - implications on performance etc or are their good patterns for mapping shared state object graphs to agent based system. tips on mapping domain models to design. Discussions not on the technology but more on how to BEST use the technology in design (real world "complex" examples would be great).

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  • N-Tiered application design tool

    - by Ben V
    I'm beginning the design of a medium-sized web application. I usually like to design from the top down, i.e., start at the highest level and design my way down. I am planning to have the following layers: Presentation (PHP/Ajax) Business Logic Data Access Database Now I'd like to start sketching out the major objects in each layer and the interaction between layers. Is there a tool more specific to this purpose than just using a graphics/diagramming tool like Visio?

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  • Good design of mapping Java Domain objects to Tables (using Hibernate)

    - by M. McKenzie
    Hey guys, I have a question that is more in the realm of design, than implementation. I'm also happy for anyone to point out resources for the answer and I'll gladly, research for myself. Highly simplified Java and SQL: Say I have a business domain POJO called 'Picture' with three attributes. class Picture int idPicture String fileName long size Say I have another business domain POJO called "Item" with 3 attributes Class Item int idItem String itemName ArrayList itemPictures These would be a normal simple relationship. You could say that 'Picture' object, will never exist outside an 'Item' object. Assume a picture belongs only to a specific item, but that an item can have multiple pictures Now - using good database design (3rd Normal Form), we know that we should put items and pictures in their own tables. Here is what I assume would be correct. table Item int idItem (primary key) String itemName table Picture int idPicture (primary key) varchar(45) fileName long size int idItem (foreign key) Here is my question: If you are making Hibernate mapping files for these objects. In the data design, your Picture table needs a column to refer to the Item, so that a foreign key relation can be maintained. However,in your business domain objects - your Picture does not hold a reference/attribute to the idItem - and does not need to know it. A java Picture instance is always instantiated inside an Item instance. If you want to know the Item that the Picture belongs to you are already in the correct scope. Call myItem.getIdItem() and myItem.getItemPictures(),and you have the two pieces of information you need. I know that Hibernate tools have a generator that can auto make your POJO's from looking at your database. My problem stems from the fact that I planned out the data design for this experiment/project first. Then when I went to make the domain java objects, I realized that good design dictated that the objects hold other objects in a nested way. This is obviously different from the way that a database schema is - where all objects(tables) are flat and hold no other complex types within them. What is a good way to reconcile this? Would you: (A) Make the hibernate mapping files so that Picture.hbm.xml has a mapping to the POJO parent's idItem Field (if it's even possible) (B) Add an int attribute in the Picture class to refer to the idItem and set it at instantiation, thus simplifying the hbm.xml mapping file by having all table fields as local attributes in the class (C) Fix the database design because it is wrong, dork. I'd truly appreciate any feedback

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  • C# MultiThread Safe Class Design

    - by Robert
    I'm trying to designing a class and I'm having issues with accessing some of the nested fields and I have some concerns with how multithread safe the whole design is. I would like to know if anyone has a better idea of how this should be designed or if any changes that should be made? using System; using System.Collections; namespace SystemClass { public class Program { static void Main(string[] args) { System system = new System(); //Seems like an awkward way to access all the members dynamic deviceInstance = (((DeviceType)((DeviceGroup)system.deviceGroups[0]).deviceTypes[0]).deviceInstances[0]); Boolean checkLocked = deviceInstance.locked; //Seems like this method for accessing fields might have problems with multithreading foreach (DeviceGroup dg in system.deviceGroups) { foreach (DeviceType dt in dg.deviceTypes) { foreach (dynamic di in dt.deviceInstances) { checkLocked = di.locked; } } } } } public class System { public ArrayList deviceGroups = new ArrayList(); public System() { //API called to get names of all the DeviceGroups deviceGroups.Add(new DeviceGroup("Motherboard")); } } public class DeviceGroup { public ArrayList deviceTypes = new ArrayList(); public DeviceGroup() {} public DeviceGroup(string deviceGroupName) { //API called to get names of all the Devicetypes deviceTypes.Add(new DeviceType("Keyboard")); deviceTypes.Add(new DeviceType("Mouse")); } } public class DeviceType { public ArrayList deviceInstances = new ArrayList(); public bool deviceConnected; public DeviceType() {} public DeviceType(string DeviceType) { //API called to get hardwareIDs of all the device instances deviceInstances.Add(new Mouse("0001")); deviceInstances.Add(new Keyboard("0003")); deviceInstances.Add(new Keyboard("0004")); //Start thread CheckConnection that updates deviceConnected periodically } public void CheckConnection() { //API call to check connection and returns true this.deviceConnected = true; } } public class Keyboard { public string hardwareAddress; public bool keypress; public bool deviceConnected; public Keyboard() {} public Keyboard(string hardwareAddress) { this.hardwareAddress = hardwareAddress; //Start thread to update deviceConnected periodically } public void CheckKeyPress() { //if API returns true this.keypress = true; } } public class Mouse { public string hardwareAddress; public bool click; public Mouse() {} public Mouse(string hardwareAddress) { this.hardwareAddress = hardwareAddress; } public void CheckClick() { //if API returns true this.click = true; } } }

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  • General Overview of Design Pattern Types

    Typically most software engineering design patterns fall into one of three categories in regards to types. Three types of software design patterns include: Creational Type Patterns Structural Type Patterns Behavioral Type Patterns The Creational Pattern type is geared toward defining the preferred methods for creating new instances of objects. An example of this type is the Singleton Pattern. The Singleton Pattern can be used if an application only needs one instance of a class. In addition, this singular instance also needs to be accessible across an application. The benefit of the Singleton Pattern is that you control both instantiation and access using this pattern. The Structural Pattern type is a way to describe the hierarchy of objects and classes so that they can be consolidated into a larger structure. An example of this type is the Façade Pattern.  The Façade Pattern is used to define a base interface so that all other interfaces inherit from the parent interface. This can be used to simplify a number of similar object interactions into one single standard interface. The Behavioral Pattern Type deals with communication between objects. An example of this type is the State Design Pattern. The State Design Pattern enables objects to alter functionality and processing based on the internal state of the object at a given time.

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  • CIC 2010 - Ghost Stories and Model Based Design

    - by warren.baird
    I was lucky enough to attend the collaboration and interoperability congress recently. The location was very beautiful and interesting, it was held in the mountains about two hours outside Denver, at the Stanley hotel, famous both for inspiring Steven King's novel "The Shining" and for attracting a lot of attention from the "Ghost Hunters" TV show. My visit was prosaic - I didn't get to experience the ghosts the locals promised - but interesting, with some very informative sessions. I noticed one main theme - a lot of people were talking about Model Based Design (MBD), which is moving design and manufacturing away from 2d drawings and towards 3d models. 2d has some pretty deep roots in industrial manufacturing and there have been a lot of challenges encountered in making the leap to 3d. One of the challenges discussed in several sessions was how to get model information out to the non-engineers in the company, which is a topic near and dear to my heart. In the 2D space, people without access to CAD software (for example, people assembling a product on the shop floor) can be given printouts of the design - it's not particularly efficient, and it definitely isn't very green, but it tends to work. There's no direct equivalent in the 3D space. One of the ways that AutoVue is used in industrial manufacturing is to provide non-CAD users with an easy to use, interactive 3D view of their products - in some cases it's directly used by people on the shop floor, but in cases where paper is really ingrained in the process, AutoVue can be used by a technical publications person to create illustrative 2D views that can be printed that show all of the details necessary to complete the work. Are you making the move to model based design? Is AutoVue helping you with your challenges? Let us know in the comments below.

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