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  • Where to store global variables like file paths in java ?

    - by Jules Olléon
    In my application I use some icons. Where should I store the path of the directory containing those icons ? The icons are used in different classes so it doesn't really make sense to store them in one of those classes in particular. I read that global variables are evil, but is it acceptable to use a class (eg Commons) containing only public static final fields to store this king of data ? What solution is used in professional applications ?

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  • Single-Page Web Apps: Client-side datastores & server persistence

    - by fig-gnuton
    How should client-side datastores & persistence be handled in a single-page web application? Global vars vs. DI/IoC: Should datastores be assigned to global variables so any part of the application can access them? Or should they be dependency injected where required? Server persistence: Assuming a datastore's data needn't always be persisted to the server immediately, should the datastore itself handle persistence? If not, then what class should handle persistence and how should the persistence class fit into the client-side architecture overall? Is the datastore considered the model in MVC, or is it something else since it just stores raw data?

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  • Pattern for version-specific implementations of a Java class

    - by Mike Monkiewicz
    So here's my conundrum. I am programming a tool that needs to work on old versions of our application. I have the code to the application, but can not alter any of the classes. To pull information out of our database, I have a DTO of sorts that is populated by Hibernate. It consumes a data object for version 1.0 of our app, cleverly named DataObject. Below is the DTO class. public class MyDTO { private MyWrapperClass wrapper; public MyDTO(DataObject data) { wrapper = new MyWrapperClass(data); } } The DTO is instantiated through a Hibernate query as follows: select new com.foo.bar.MyDTO(t1.data) from mytable t1 Now, a little logic is needed on top of the data object, so I made a wrapper class for it. Note the DTO stores an instance of the wrapper class, not the original data object. public class MyWrapperClass { private DataObject data; public MyWrapperClass(DataObject data) { this.data = data; } public String doSomethingImportant() { ... version-specific logic ... } } This works well until I need to work on version 2.0 of our application. Now DataObject in the two versions are very similar, but not the same. This resulted in different sub classes of MyWrapperClass, which implement their own version-specific doSomethingImportant(). Still doing okay. But how does myDTO instantiate the appropriate version-specific MyWrapperClass? Hibernate is in turn instantiating MyDTO, so it's not like I can @Autowire a dependency in Spring. I would love to reuse MyDTO (and my dozens of other DTOs) for both versions of the tool, without having to duplicate the class. Don't repeat yourself, and all that. I'm sure there's a very simple pattern I'm missing that would help this. Any suggestions?

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  • Writing a synchronized thread-safety wrapper for NavigableMap

    - by polygenelubricants
    java.util.Collections currently provide the following utility methods for creating synchronized wrapper for various collection interfaces: synchronizedCollection(Collection<T> c) synchronizedList(List<T> list) synchronizedMap(Map<K,V> m) synchronizedSet(Set<T> s) synchronizedSortedMap(SortedMap<K,V> m) synchronizedSortedSet(SortedSet<T> s) Analogously, it also has 6 unmodifiedXXX overloads. The glaring omission here are the utility methods for NavigableMap<K,V>. It's true that it extends SortedMap, but so does SortedSet extends Set, and Set extends Collection, and Collections have dedicated utility methods for SortedSet and Set. Presumably NavigableMap is a useful abstraction, or else it wouldn't have been there in the first place, and yet there are no utility methods for it. So the questions are: Is there a specific reason why Collections doesn't provide utility methods for NavigableMap? How would you write your own synchronized wrapper for NavigableMap? Glancing at the source code for OpenJDK version of Collections.java seems to suggest that this is just a "mechanical" process Is it true that in general you can add synchronized thread-safetiness feature like this? If it's such a mechanical process, can it be automated? (Eclipse plug-in, etc) Is this code repetition necessary, or could it have been avoided by a different OOP design pattern?

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  • How can I determine/use $(this) in js callback script

    - by Rabbott
    I am using Rails and jQuery, making an ajax call initiated by clicking a link. I setup my application.js file to look like the one proposed here and it works great. The problem I'm having is how can I use $(this) in my say.. update.js.erb file to represent the link I clicked? I don't want to have to assign an ID to every one, then recompile that id in the callback script.. EDIT To give a simple example of something similar to what I'm trying to do (and much easier to explain): If a user clicks on a link, that deletes that element from a list, the controller would handle the callback, and the callback (which is in question here) would delete the element I clicked on, so in the callback delete.js.erb would just say $(this).fadeOut(); This is why I want to use $(this) so that I dont have to assign an ID to every element (which would be the end of the world, just more verbose markup) application.js jQuery.ajaxSetup({ 'beforeSend': function(xhr) {xhr.setRequestHeader("Accept", "text/javascript,application/javascript,text/html")} }) function _ajax_request(url, data, callback, type, method) { if (jQuery.isFunction(data)) { callback = data; data = {}; } return jQuery.ajax({ type: method, url: url, data: data, success: callback, dataType: type }); } jQuery.extend({ put: function(url, data, callback, type) { return _ajax_request(url, data, callback, type, 'PUT'); }, delete_: function(url, data, callback, type) { return _ajax_request(url, data, callback, type, 'DELETE'); } }); jQuery.fn.submitWithAjax = function() { this.unbind('submit', false); this.submit(function() { $.post(this.action, $(this).serialize(), null, "script"); return false; }) return this; }; // Send data via get if <acronym title="JavaScript">JS</acronym> enabled jQuery.fn.getWithAjax = function() { this.unbind('click', false); this.click(function() { $.get($(this).attr("href"), $(this).serialize(), null, "script"); return false; }) return this; }; // Send data via Post if <acronym title="JavaScript">JS</acronym> enabled jQuery.fn.postWithAjax = function() { this.unbind('click', false); this.click(function() { $.post($(this).attr("href"), $(this).serialize(), null, "script"); return false; }) return this; }; jQuery.fn.putWithAjax = function() { this.unbind('click', false); this.click(function() { $.put($(this).attr("href"), $(this).serialize(), null, "script"); return false; }) return this; }; jQuery.fn.deleteWithAjax = function() { this.removeAttr('onclick'); this.unbind('click', false); this.click(function() { $.delete_($(this).attr("href"), $(this).serialize(), null, "script"); return false; }) return this; }; // This will "ajaxify" the links function ajaxLinks(){ $('.ajaxForm').submitWithAjax(); $('a.get').getWithAjax(); $('a.post').postWithAjax(); $('a.put').putWithAjax(); $('a.delete').deleteWithAjax(); } show.html.erb <%= link_to 'Link Title', article_path(a, :sentiment => Article::Sentiment['Neutral']), :class => 'put' %> The combination of the two things will call update.js.erb in rails, the code in that file is used as the callback of the ajax ($.put in this case) update.js.erb // user feedback $("#notice").html('<%= flash[:notice] %>'); // update the background color $(this OR e.target).attr("color", "red");

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  • Sending object C from class A to class B

    - by user278618
    Hi, I can't figure out how to design classes in my system. In classA I create object selenium (it simulates user actions at website). In this ClassA I create another objects like SearchScreen, Payment_Screen and Summary_Screen. # -*- coding: utf-8 -*- from selenium import selenium import unittest, time, re class OurSiteTestCases(unittest.TestCase): def setUp(self): self.verificationErrors = [] self.selenium = selenium("localhost", 5555, "*chrome", "http://www.someaddress.com/") time.sleep(5) self.selenium.start() def test_buy_coffee(self): sel = self.selenium sel.open('/') sel.window_maximize() search_screen=SearchScreen(self.selenium) search_screen.choose('lavazza') payment_screen=PaymentScreen(self.selenium) payment_screen.fill_test_data() summary_screen=SummaryScreen(selenium) summary_screen.accept() def tearDown(self): self.selenium.stop() self.assertEqual([], self.verificationErrors) if __name__ == "__main__": unittest.main() It's example SearchScreen module: class SearchScreen: def __init__(self,selenium): self.selenium=selenium def search(self): self.selenium.click('css=button.search') I want to know if there is anything ok with a design of those classes?

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  • Searching for the right pattern to handle login data

    - by stevebot
    Hi all, I'm working on a controller that handles logins for a Web app. These logins will come from multiple clients but will all contain the same data. However, depending on the client, this data will be interpreted into common entities for our webapp differently. For instance, we have a user code that gets sent in, and in one case we may use the first four digits of the code, and in another case 12 digits of the code to map to a field on a User entity. Instead of handling this all in the controller and having big nasty if blocks of logic, I would like to use a pattern to handle how this information gets ingested into our application. What are your opinions?

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  • Design pattern to separate messages from actual process.

    - by Manish Gupta
    I am having a C# application to sync data between PC and palm devices. There are codes written like below: showMessage("synchronizing Table1"); Sync(destTable1,sourceTable1); Sync(destTable2,sourceTable2); showMessage("synchronizing Table2"); // more code How do I separate the actual process of synchronizing from displaying message? Which design pattern to follow? Thanks in advance...

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  • How to use interfaces in exception handling

    - by vikp
    Hi, I'm working on the exception handling layer for my application. I have read few articles on interfaces and generics. I have used inheritance before quite a lot and I'm comfortable with in that area. I have a very brief design that I'm going to implement: public interface IMyExceptionLogger { public void LogException(); // Helper methods for writing into files,db, xml } I'm slightly confused what I should be doing next. public class FooClass: IMyExceptionLogger { // Fields // Constructors } Should I implement LogException() method within FooClass? If yes, than I'm struggling to see how I'm better of using an interface instead of the concrete class... I have a variety of classes that will make a use of that interface, but I don't want to write an implementation of that interface within each class. In the same time If I implement an interface in one class, and then use that class in different layers of the application I will be still using concrete classes instead of interfaces, which is a bad OO design... I hope this makes sense. Any feedback and suggestions are welcome. Please notice that I'm not interested in using net4log or its competitors because I'm doing this to learn. Thank you Edit: Wrote some more code. So I will implement variety of loggers with this interface, i.e. DBExceptionLogger, CSVExceptionLogger, XMLExceptionLogger etc. Than I will still end up with concrete classes that I will have to use in different layers of my application.

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  • how to tackle a new project

    - by stevo
    Hi, I have a question about best practice on how to tackle a new project, any project. When starting a new project how do you go about tackling the project, do you split it into sections, start writing code, draw up flow diagrams. I'm asking this question because I'm looking for advice on how I can start new projects so I can get going on them quicker. I can have it planned, designed and starting coding with everything worked out. Any advice? Thanks Stephen

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  • how should i create my own 'now' / DateTime.Now ?

    - by Michel
    Hi all, i'm starting to build a part of a system which will hold a lot of DateTime validations, and a lot of 'if it was done before now' or 'if it will start in an hour etc'. Usual way to go is to use DateTime.Now to get the actual time. I predict however, that during unit test that will give me a real headache because i will have to setup my testdata for the time when the test will run in stead of use a default set of test data. So i thought: why not use my own 'now' so i can set the current datetime to any moment in time. As i don't want to set the testservers internal clock i was thinking about this solution, and i was wondering what you think of it. Base thought is that i use my own DateTime class. That class gives you the current datetime, but you can also set your own time from outside. public static class MyDateTime { private static TimeSpan _TimeDifference = TimeSpan.Zero; public static DateTime Now { get { return DateTime.Now + _TimeDifference; } } public static void SetNewNow(DateTime newNow) { _TimeDifference = newNow - DateTime.Now; } public static void AddToRealTime(TimeSpan timeSpan ) { _TimeDifference = timeSpan; } public static void SubtractFromRealTime(TimeSpan timeSpan) { _TimeDifference = - timeSpan; } }

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  • database design - empty fields

    - by imanc
    Hey, I am currently debating an issue with a guy on my dev team. He believes that empty fields are bad news. For instance, if we have a customer details table that stores data for customers from different countries, and each country has a slightly different address configuration - plus 1-2 extra fields, e.g. French customer details may also store details for entry code, and floor/level plus title fields (madamme, etc.). South Africa would have a security number. And so on. Given that we're talking about minor variances my idea is to put all of the fields into the table and use what is needed on each form. My colleague believes we should have a separate table with extra data. E.g. customer_info_fr. But this seams to totally defeat the purpose of a combined table in the first place. His argument is that empty fields / columns is bad - but I'm struggling to find justification in terms of database design principles for or against this argument and preferred solutions. Another option is a separate mini EAV table that stores extra data with parent_id, key, val fields. Or to serialise extra data into an extra_data column in the main customer_data table. I think I am confused because what I'm discussing is not covered by 3NF which is what I would typically use as a reference for how to structure data. So my question specifically: - if you have slight variances in data for each record (1-2 different fields for instance) what is the best way to proceed?

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  • Why represent shopping carts and order invoices differently in a domain model?

    - by Todd
    I've built some shopping cart systems in the past, but I always designed them such that the final order invoice is just a shopping cart that has been marked as "purchased". All the logic for adding/removing/changing items in a cart is also the logic for the order. All data is stored in the same tables in the database. But it seems this is not the proper way to design an e-commerce site.. Can someone explain the benefit of separating the shopping cart from invoices in the domain model? It seems to me this would lead to a lot of duplicated code, an extra set of tables in the database, and make it harder to maintain in the event the system need to start accommodating more complicated orders (like specifying selected options for an item which may or may not change the price/availability/shipping time of the order). I'm assuming I just haven't seen the light, as every book and other example I see seems to separate these two seemingly similar concerns -- but I can't find any explanation as to the benefit of doing such! It's also the case in the systems that I design that changes are often made after the initial order is confirmed. It's not uncommon for items to be removed, replaced, or added afterwards (but prior to fulfillment).

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