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• Some sonatype nexus questions.

  - by smallufo

  I deployed a sonatype nexus server inside my LAN , mapping some remote repositories to my public repositories : First question is , why these repositories not sync with the "real" repositories ? For example , I mapped maven central (http://repo1.maven.org/maven2) to "central" , but when I browse http://smallufo:8081/nexus/content/repositories/central/org/springframework/ , the packages are not complete , in http://repo2.maven.org/maven2/org/springframework/ , there are tons of artifacts , but I only have some of them : And versions are old ... ex : spring-core is only 2.5.6.SEC01 , but the latest version is 3.0.2.RELEASE. And my maven client seems can only find the old artifacts ... "central" is a proxy directory , it should be the same with the remote server. I tried to "Expire Cache" , "ReIndex" , "Incremental ReIndex" the whole "central" : After a long time with almost 100% java process load , the situation seems not better , just add some artifacts ... not reflecting the real "Maven Central" data... Second question , what's difference with "Expire Cache" , "ReIndex" , "Incremental ReIndex" ? Even I can "search" spring-core.3.0.2.RELEASE , my m2eclipse still cannot find it : I can also see the spring-core-3.0.2.RELEASE in the "index" , (but not available in "storage") : But why m2eclipse cannot make use of it ? it seems m2eclipse can only install artifacts in the storage , if this is how nexus works , how do I "force" download spring-core-3.0.2.RELEASE to nexus's storage ? How do I solve these strange incompatibilities ? Thanks a lot !

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• In M-V-VM where does my code go?

  - by Nate Bross

  So, this is a pretty basic question I hope. I have a web service that I've added through Add Service Reference. It has some methods to get list and get detail of a perticular table in my database. What I'm trying to do is setup a UI as follows: App Load Load service proxy Call the GetList(); method display the results in a ListBox control User Double Clicks item in ListBox, display a modal dialog with a "detail" view I'm extremely new to using MVVM, so any help would be greatly appreciated. Additional information: // Service Interface (simplification): interface IService { IEnumerable<MyObject> GetList(); MyObject GetDetail(int id); } // Data object (simplification) class MyObject { public int ID { get; set; } public string Name { get; set; } } I'm thinking I should have something like this: MainWindow MyObjectViewUserControl Displays list Opens modal window on double click Specific Questions: What would my ViewModel class look like? Where does the code to handle the double click go? Inside the UserControl? Sorry for the long details, but I'm very new to the whole thing and I'm not educated enough to ask the right questions. I checked out the MVVM Sample from wpf.codeplex.com and something isn't quite clicking for me yet, because it seems very confusing.

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• Questions about the Backpropogation Algorithm

  - by Colemangrill

  I have a few questions concerning backpropogation. I'm trying to learn the fundamentals behind neural network theory and wanted to start small, building a simple XOR classifier. I've read a lot of articles and skimmed multiple textbooks - but I can't seem to teach this thing the pattern for XOR. Firstly, I am unclear about the learning model for backpropogation. Here is some pseudo-code to represent how I am trying to train the network. [Lets assume my network is setup properly (ie: multiple inputs connect to a hidden layer connect to an output layer and all wired up properly)]. SET guess = getNetworkOutput() // Note this is using a sigmoid activation function. SET error = desiredOutput - guess SET delta = learningConstant * error * sigmoidDerivative(guess) For Each Node in inputNodes For Each Weight in inputNodes[n] inputNodes[n].weight[j] += delta; // At this point, I am assuming the first layer has been trained. // Then I recurse a similar function over the hidden layer and output layer. // The prime difference being that it further divi's up the adjustment delta. I realize this is probably not enough to go off of, and I will gladly expound on any part of my implementation. Using the above algorithm, my neural network does get trained, kind of. But not properly. The output is always XOR 1 1 [smallest number] XOR 0 0 [largest number] XOR 1 0 [medium number] XOR 0 1 [medium number] I can never train the [1,1] [0,0] to be the same value. If you have any suggestions, additional resources, articles, blogs, etc for me to look at I am very interested in learning more about this topic. Thank you for your assistance, I appreciate it greatly!

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• Entity Framework POCO objects

  - by Dan

  I'm struggling with understanding Entity Framework and POCO objects. Here's what I'm trying to achieve. 1) Separate the DAL from the Business Layer by having my business layer use an interface to my DAL. Maybe use Unity to create my context. 2) Use Entity Framework inside my DAL. I have a Domain model with objects that reside in my business layer. I also have a database full of tables that doesn't really represent my domain model. I setup Entity Framework and generated POCO objects by using the ADO.NET POCO Generator extension. This gave me an object for each table in my database. Now I want to be able to say context.GetAll<User>(); and have it return a list of my User objects. The User object is in my business layer. Is that possible? Does that make sense or am I totally off and should start over? I'm guessing I need to use the repository pattern to achieve this, but I'm not sure. Can anyone help?

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• figuring out which field to look for a value in with SQL and perl

  - by Micah

  I'm not too good with SQL and I know there's probably a much more efficient way to accomplish what I'm doing here, so any help would be much appreciated. Thanks in advance for your input! I'm writing a short program for the local school high school. At this school, juniors and seniors who have driver's licenses and cars can opt to drive to school rather than ride the bus. Each driver is assigned exactly one space, and their DLN is used as the primary key of the driver's table. Makes, models, and colors of cars are stored in a separate cars table, related to the drivers table by the License plate number field. My idea is to have a single search box on the main GUI of the program where the school secretary can type in who/what she's looking for and pull up a list of results. Thing is, she could be typing a license plate number, a car color, make, and model, someone driver's name, some student driver's DLN, or a space number. As the programmer, I don't know what exactly she's looking for, so a couple of options come to mind for me to build to be certain I check everywhere for a match: 1) preform a couple of SELECT * FROM [tablename] SQL statements, one per table and cram the results into arrays in my program, then search across the arrays one element at a time with regex, looking for a matched pattern similar to the search term, and if I find one, add the entire record that had a match in it to a results array to display on screen at the end of the search. 2) take whatever she's looking for into the program as a scaler and prepare multiple select statements around it, such as SELECT * FROM DRIVERS WHERE DLN = $Search_Variable SELECT * FROM DRIVERS WHERE First_Name = $Search_Variable SELECT * FROM CARS WHERE LICENSE = $Search_Variable and so on for each attribute of each table, sticking the results into a results array to show on screen when the search is done. Is there a cleaner way to go about this lookup without having to make her specify exactly what she's looking for? Possibly some kind of SQL statement I've never seen before?

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• Why does this Haskell code produce the "infinite type" error?

  - by Charlie Flowers

  I am new to Haskell and facing a "cannot construct infinite type" error that I cannot make sense of. In fact, beyond that, I have not been able to find a good explanation of what this error even means, so if you could go beyond my basic question and explain the "infinite type" error, I'd really appreciate it. Here's the code: intersperse :: a -> [[a]] -> [a] -- intersperse '*' ["foo","bar","baz","quux"] -- should produce the following: -- "foo*bar*baz*quux" -- intersperse -99 [ [1,2,3],[4,5,6],[7,8,9]] -- should produce the following: -- [1,2,3,-99,4,5,6,-99,7,8,9] intersperse _ [] = [] intersperse _ [x] = x intersperse s (x:y:xs) = x:s:y:intersperse s xs And here's the error trying to load it into the interpreter: Prelude :load ./chapter.3.ending.real.world.haskell.exercises.hs [1 of 1] Compiling Main ( chapter.3.ending.real.world.haskell.exercises.hs, interpreted ) chapter.3.ending.real.world.haskell.exercises.hs:147:0: Occurs check: cannot construct the infinite type: a = [a] When generalising the type(s) for `intersperse' Failed, modules loaded: none. Thanks. EDIT: Thanks to the responses, I have corrected the code and I also have a general guideline for dealing with the "infinite type" error in Haskell: Corrected code intersperse _ [] = [] intersperse _ [x] = x intersperse s (x:xs) = x ++ s:intersperse s xs What the problem was: My type signature states that the second parameter to intersperse is a list of lists. Therefore, when I pattern matched against "s (x:y:xs)", x and y became lists. And yet I was treating x and y as elements, not lists. Guideline for dealing with the "infinite type" error: Most of the time, when you get this error, you have forgotten the types of the various variables you're dealing with, and you have attempted to use a variable as if it were some other type than what it is. Look carefully at what type everything is versus how you're using it, and this will usually uncover the problem.

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• Nginx , Apache , Mysql , Memcache with server 4G ram. How optimize to enoigh of memory?

  - by TomSawyer

  i have 1 dedicated server with Nginx proxy for Apache. Memcache, mysql, 4G Ram. These day, my visitor on my site wasn't increased, but my server get overload always in some specified time. (9AM - 15PM) Ram in use is increased second by second to full. that's moment, my server will get overload. i have to kill all apache , mysql service and reboot it to get free memory. and it'll full again. that's the terrible circle. here is my ram in use at the moment 160(nginx) 220(apache) 512(memcache) 924(mysql) here's process number 4(nginx) 14(apache) 5(memcache) 20(mysql) and here's my my.cnf config. someone can help me to optimize it? [mysqld] datadir=/var/lib/mysql socket=/var/lib/mysql/mysql.sock user=mysql skip-locking skip-networking skip-name-resolve # enable log-slow-queries log-slow-queries = /var/log/mysql-slow-queries.log long_query_time=3 max_connections=200 wait_timeout=64 connect_timeout = 10 interactive_timeout = 25 thread_stack = 512K max_allowed_packet=16M table_cache=1500 read_buffer_size=4M join_buffer_size=4M sort_buffer_size=4M read_rnd_buffer_size = 4M max_heap_table_size=256M tmp_table_size=256M thread_cache=256 query_cache_type=1 query_cache_limit=4M query_cache_size=16M thread_concurrency=8 myisam_sort_buffer_size=128M # Disabling symbolic-links is recommended to prevent assorted security risks symbolic-links=0 [mysqldump] quick max_allowed_packet=16M [mysql] no-auto-rehash [isamchk] key_buffer=256M sort_buffer=256M read_buffer=64M write_buffer=64M [myisamchk] key_buffer=256M sort_buffer=256M read_buffer=64M write_buffer=64M [mysqlhotcopy] interactive-timeout [mysql.server] user=mysql basedir=/var/lib [mysqld_safe] log-error=/var/log/mysqld.log pid-file=/var/run/mysqld/mysqld.pid

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• Is MarshalByRefObject special?

  - by Vilx-

  .NET has a thing called remoting where you can pass objects around between separate appdomains or even physical machines. I don't fully understand how the magic is done, hence this question. In remoting there are two base ways of passing objects around - either they can be serialized (converted to a bunch of bytes and the rebuilt at the other end) or they can inherit from MarshalByRefObject, in which case .NET makes some transparent proxies and all method calls are forwarded back to the original instance. This is pretty cool and works like magic. And I don't like magic in programming. Looking at the MarshalByRefObject with the Reflector I don't see anything that would set it apart from any other typical object. Not even a weird internal attribute or anything. So how is the whole transparent proxy thing organized? Can I make such a mechanism myself? Can I make an alternate MyMarshalByRefObject which would not inherit from MarshalByRefObject but would still act the same? Or is MarshalByRefObject receiving some special treatment by the .NET engine itself and the whole remoting feat is non-duplicatable by mere mortals?

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• Best way to implement plugin framework - are DLLs the only way (C/C++ project)?

  - by Microkernel

  Introduction: I am currently developing a document classifier software in C/C++ and I will be using Naive-Bayesian model for classification. But I wanted the users to use any algorithm that they want(or I want in the future), hence I went to separate the algorithm part in the architecture as a plugin that will be attached to the main app @ app start-up. Hence any user can write his own algorithm as a plugin and use it with my app. Problem Statement: The way I am intending to develop this is to have each of the algorithms that user wants to use to be made into a DLL file and put into a specific directory. And at the start, my app will search for all the DLLs in that directory and load them. My Questions: (1) What if a malicious code is made as a DLL (and that will have same functions mandated by plugin framework) and put into my plugins directory? In that case, my app will think that its a plugin and picks it and calls its functions, so the malicious code can easily bring down my entire app down (In the worst case could make my app as a malicious code launcher!!!). (2) Is using DLLs the only way available to implement plugin design pattern? (Not only for the fear of malicious plugin, but its a generic question out of curiosity :) ) (3) I think a lot of softwares are written with plugin model for extendability, if so, how do they defend against such attacks? (4) In general what do you think about my decision to use plugin model for extendability (do you think I should look at any other alternatives?) Thank you -MicroKernel :)

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• Refactoring an ASP.NET 2.0 app to be more "modern"

  - by Wayne M

  This is a hypothetical scenario. Let's say you've just been hired at a company with a small development team. The company uses an internal CRM/ERP type system written in .NET 2.0 to manage all of it's day to day things (let's simplify and say customer accounts and records). The app was written a couple of years ago when .NET 2.0 was just out and uses the following architectural designs: Webforms Data layer is a thin wrapper around SqlCommand that calls stored procedures Rudimentary DTO-style business objects that are populated via the sprocs A "business logic" layer that acts as a gateway between the webform and database (i.e. code behind calls that layer) Let's say that as there are more changes and requirements added to the application, you start to feel that the old architecture is showing its age, and changes are increasingly more difficult to make. How would you go about introducing refactoring steps to A) Modernize the app (i.e. proper separation of concerns) and B) Make sure that the app can readily adapt to change in the organization? IMO the changes would involve: Introduce an ORM like Linq to Sql and get rid of the sprocs for CRUD Assuming that you can't just throw out Webforms, introduce the M-V-P pattern to the forms Make sure the gateway classes conform to SRP and the other SOLID principles. Change the logic that is re-used to be web service methods instead of having to reuse code What are your thoughts? Again this is a totally hypothetical scenario that many of us have faced in the past, or may end up facing.

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• re.sub emptying list

  - by jmau5

  def process_dialect_translation_rules(): # Read in lines from the text file specified in sys.argv[1], stripping away # excess whitespace and discarding comments (lines that start with '##'). f_lines = [line.strip() for line in open(sys.argv[1], 'r').readlines()] f_lines = filter(lambda line: not re.match(r'##', line), f_lines) # Remove any occurances of the pattern '\s*<=>\s*'. This leaves us with a # list of lists. Each 2nd level list has two elements: the value to be # translated from and the value to be translated to. Use the sub function # from the re module to get rid of those pesky asterisks. f_lines = [re.split(r'\s*<=>\s*', line) for line in f_lines] f_lines = [re.sub(r'"', '', elem) for elem in line for line in f_lines] This function should take the lines from a file and perform some operations on the lines, such as removing any lines that begin with ##. Another operation that I wish to perform is to remove the quotation marks around the words in the line. However, when the final line of this script runs, f_lines becomes an empty lines. What happened? Requested lines of original file: ## English-Geek Reversible Translation File #1 ## (Moderate Geek) ## Created by Todd WAreham, October 2009 "TV show" <=> "STAR TREK" "food" <=> "pizza" "drink" <=> "Red Bull" "computer" <=> "TRS 80" "girlfriend" <=> "significant other"

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• How to maintain form state after Post-Redirect-Get in ASP.net?

  - by Ian Boyd

  Imagine a page with a form input: Search Criteria: crackers                   From: [email protected]           To: [email protected]       Subject: How to maintain form state with PRG? Message: Imagine a page with form input:                         Send After the user clicks Send, the server will instruct to client to Redirect, as part of the Post-Redirect-Get pattern. POST /mail/u/compose HTTP/1.1 303 See Other Location: http://stackoverflow.com/mail/u/compose And the client will issue a GET of the new page. The problem is that some elements of the existing form are lost: Search Criteria:                    It gets worse when there are a few drop-downs, and checkboxes. How can i maintain form state in using Post-Redirect-Get in ASP.net, given that the viewstate is then non-existent. Bonus Reading ASP.NET: How to redirect, prefilling form data?

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• On the search for my next great .Net Read

  - by user127954

  Just got done with "The art of unit testing". It was a great read and i think everyone should go buy a copy. With that said i think the next book I'm like to read would be a architecture / Design type book that would focus heavily on building your objects / software in such a way that it would be: Low Coupling High Cohesion Easily Maintainable / Extended Easy to test Easy to Navigate / Debug The above characteristcs are the most important ones but also maybe it would also include (but not necessary) designing for: Performance - Don't want to design a system at at the end find out its dog slow :) Scalability - Again don't want to design something at the end find out it won't scale. I'd also prefer (but not necessary again): Something newer - Architectural principles seem to gradually evolve / improve over time and id like something with current thinking. .Net as illustrating language - like i said above its not mandatory but since its what i use every day id prefer it to be in .net. Doesn't really matter if its in vb.net or c# Some of the topics that would be talked about its how to minimize dependencies and using interfaces throughout your solution rather than concrete classes. Maybe it would constract /compare some of the newest design principles like DDD, Repository Pattern, Ect... I already have "Clean Code" (don't know if its this type of book or not) and "Working effectively with legacy code" on my radar but id like to read a book based upon the topic i talked about above first. Is there such a book?

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• Testing When Correctness is Poorly Defined?

  - by dsimcha

  I generally try to use unit tests for any code that has easily defined correct behavior given some reasonably small, well-defined set of inputs. This works quite well for catching bugs, and I do it all the time in my personal library of generic functions. However, a lot of the code I write is data mining code that basically looks for significant patterns in large datasets. Correct behavior in this case is often not well defined and depends on a lot of different inputs in ways that are not easy for a human to predict (i.e. the math can't reasonably be done by hand, which is why I'm using a computer to solve the problem in the first place). These inputs can be very complex, to the point where coming up with a reasonable test case is near impossible. Identifying the edge cases that are worth testing is extremely difficult. Sometimes the algorithm isn't even deterministic. Usually, I do the best I can by using asserts for sanity checks and creating a small toy test case with a known pattern and informally seeing if the answer at least "looks reasonable", without it necessarily being objectively correct. Is there any better way to test these kinds of cases?

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• Are there good reasons not to use an ORM?

  - by hangy

  During my apprenticeship, I have used NHibernate for some smaller projects which I mostly coded and designed on my own. Now, before starting some bigger project, the discussion arose how to design data access and whether or not to use an ORM layer. As I am still in my apprenticeship and still consider myself a beginner in enterprise programming, I did not really try to push in my opinion, which is that using an object relational mapper to the database can ease development quite a lot. The other coders in the development team are much more experienced than me, so I think I will just do what they say. :-) However, I do not completely understand two of the main reasons for not using NHibernate or a similar project: One can just build one’s own data access objects with SQL queries and copy those queries out of Microsoft SQL Server Management Studio. Debugging an ORM can be hard. So, of course I could just build my data access layer with a lot of SELECTs etc, but here I miss the advantage of automatic joins, lazy-loading proxy classes and a lower maintenance effort if a table gets a new column or a column gets renamed. (Updating numerous SELECT, INSERT and UPDATE queries vs. updating the mapping config and possibly refactoring the business classes and DTOs.) Also, using NHibernate you can run into unforeseen problems if you do not know the framework very well. That could be, for example, trusting the Table.hbm.xml where you set a string’s length to be automatically validated. However, I can also imagine similar bugs in a “simple” SqlConnection query based data access layer. Finally, are those arguments mentioned above really a good reason not to utilise an ORM for a non-trivial database based enterprise application? Are there probably other arguments they/I might have missed? (I should probably add that I think this is like the first “big” .NET/C# based application which will require teamwork. Good practices, which are seen as pretty normal on Stack Overflow, such as unit testing or continuous integration, are non-existing here up to now.)

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• OOP design issue: Polymorphism

  - by Graham Phillips

  I'm trying to solve a design issue using inheritance based polymorphism and dynamic binding. I have an abstract superclass and two subclasses. The superclass contains common behaviour. SubClassA and SubClassB define some different methods: SubClassA defines a method performTransform(), but SubClassB does not. So the following example 1 var v:SuperClass; 2 var b:SubClassB = new SubClassB(); 3 v = b; 4 v.performTransform(); would cause a compile error on line 4 as performTransform() is not defined in the superclass. We can get it to compile by casting... (v as SubClassA).performTransform(); however, this will cause a runtime exception to be thrown as v is actually an instance of SubClassB, which also does not define performTransform() So we can get around that by testing the type of an object before casting it: if( typeof v == SubClassA) { (cast v to SubClassA).performTransform(); } That will ensure that we only call performTransform() on v's that are instances of SubClassA. That's a pretty inelegant solution to my eyes, but at least its safe. I have used interface based polymorphism (interface meaning a type that can't be instantiated and defines the API of classes that implement it) in the past, but that also feels clunky. For the above case, if SubClassA and SubClassB implemented ISuperClass that defined performTransform, then they would both have to implement performTransform(). If SubClassB had no real need for a performTransform() you would have to implement an empty function. There must be a design pattern out there that addresses the issue.

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• Regular Expression with Names and Emails

  - by Nina

  I am having a problem with regular expressions at the moment. What I'm trying to do is that for each line through the iteration, it checks for this type of pattern: Lastname, Firstname If it finds the name, then it will take the first letter of the first name, and the first six letters of the lastname and form it as an email. I have the following: $checklast = "[A-z],"; $checkfirst = "[A-z]"; if (ereg($checklast, $parts[1])||ereg($checkfirst, $parts[2])){ $first = preg_replace($checkfirst, $checkfirst{1,1}, $parts[2]); print "<a href='mailto:[email protected];'> $parts[$i] </a>"; } This one obviously broke the code. But I was initially attempting to find only the first letter of the firstname and then after that the first six letters of the lastname followed by the @email.com This didn't work out too well. I'm not sure what to do at this point. Any help is much appreciated.

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• ctrl+click or shift+click not always firing the onclick event

  - by Erik

  Hi, I recently discovered that different browsers handle the onclick event differently when the control of shift key is pressed. Same thing for following links with the middle mouse button. <a href="http://www.example.com/" onclick="alert('onclick');">go to example.com</a> Onclick browser support table Mouse Keyboard Chrome Firefox Safari Opera IE5.5 IE6 IE7 IE8 IE9 Left None yes yes yes yes yes yes yes yes yes Left Ctrl yes yes yes yes ? yes no no ? Left Shift yes yes yes yes ? yes yes yes ? Middle None yes no yes no ? N/A no no ? Can someone please fill in the question marks for me? Also; I'm wondering if the behaviour differs for each version of Chrome, Firefox, Safari and Opera. Finding a logical pattern in this behaviour would be even nicer, but I don't think there is :). Thanks a lot.

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• Help regarding database and logic layer for my ASP.NET MVC application

  - by Ismail S

  I'm going to start a new project which is going to be small initially but may grow to big over the years. I'm strongly convinced that I'm going to use ASP.NET MVC with jQuery for UI. I want to go for MySQL as database for some reasons but worried on few things. I've a good years of experience working on SQL Server databases and on one project I've had a bad experience creating and managing stored procedures on MySQL database. I'm totally new to Linq but I see that it is easier to use once you are familiar with it. First thing is that accessing data should be easy. So I thought I should use MySQL to Linq but somewhere I read that it is not directly supported but MySQL .NET connector adds support for EntityFramework. I don't know what are the pros and cons of it. I would love if I can implement repository pattern. Will it be possible if I use Entity Framework? I'm not clear on how I should go about all this or I should just forget every thing and directly use SQL to Linq on SQL Server. I'm also concerned about the performance. Someone told me that if we use Entity framework it fetches lot of data and then filter it. Is that right?

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• What's the use of writing tests matching configuration-like code line by line?

  - by Pascal Van Hecke

  Hi, I have been wondering about the usefulness of writing tests that match code one-by-one. Just an example: in Rails, you can define 7 restful routes in one line in routes.rb using: resources :products BDD/TDD proscribes you test first and then write code. In order to test the full effect of this line, devs come up with macros e.g. for shoulda: http://kconrails.com/2010/01/27/route-testing-with-shoulda-in-ruby-on-rails/ class RoutingTest < ActionController::TestCase # simple should_map_resources :products end I'm not trying to pick on the guy that wrote the macros, this is just an example of a pattern that I see all over Rails. I'm just wondering what the use of it is... in the end you're just duplicating code and the only thing you test is that Rails works. You could as well write a tool that transforms your test macros into actual code... When I ask around, people answer me that: "the tests should document your code, so yes it makes sense to write them, even if it's just one line corresponding to one line" What are your thoughts?

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• How strict should I be in the "do the simplest thing that could possible work" while doing TDD

  - by Support - multilanguage SO

  For TDD you have to Create a test that fail Do the simplest thing that could possible work to pass the test Add more variants of the test and repeat Refactor when a pattern emerge With this approach you're supposing to cover all the cases ( that comes to my mind at least) but I'm wonder if am I being too strict here and if it is possible to "think ahead" some scenarios instead of simple discover them. For instance, I'm processing a file and if it doesn't conform to a certain format I am to throw an InvalidFormatException So my first test was: @Test void testFormat(){ // empty doesn't do anything... processor.validate("empty.txt"); try { processor.validate("invalid.txt"); assert false: "Should have thrown InvalidFormatException"; } catch( InvalidFormatException ife ) { assert "Invalid format".equals( ife.getMessage() ); } } I run it and it fails because it doesn't throw an exception. So the next thing that comes to my mind is: "Do the simplest thing that could possible work", so I : public void validate( String fileName ) throws InvalidFormatException { if(fileName.equals("invalid.txt") { throw new InvalidFormatException("Invalid format"); } } Doh!! ( although the real code is a bit more complicated, I found my self doing something like this several times ) I know that I have to eventually add another file name and other test that would make this approach impractical and that would force me to refactor to something that makes sense ( which if I understood correctly is the point of TDD, to discover the patterns the usage unveils ) but: Q: am I taking too literal the "Do the simplest thing..." stuff?

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• How should I return different types in a method based on the value of a string in Java?

  - by Siracuse

  I'm new to Java and I have come to having the following problem: I have created several classes which all implement the interface "Parser". I have a JavaParser, PythonParser, CParser and finally a TextParser. I'm trying to write a method so it will take either a File or a String (representing a filename) and return the appropriate parser given the extension of the file. Here is some psuedo-code of what I'm basically attempting to do: public Parser getParser(String filename) { String extension = filename.substring(filename.lastIndexOf(".")); switch(extension) { case "py": return new PythonParser(); case "java": return new JavaParser(); case "c": return new CParser(); default: return new TextParser(); } } In general, is this the right way to handle this situation? Also, how should I handle the fact that Java doesn't allow switching on strings? Should I use the .hashcode() value of the strings? I feel like there is some design pattern or something for handling this but it eludes me. Is this how you would do it?

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• What Test Environment Setup do Top Project Committers Use in the Ruby Community?

  - by viatropos

  Today I am going to get as far as I can setting up my testing environment and workflow. I'm looking for practical advice on how to setup the test environment from you guys who are very passionate and versed in Ruby Testing. By the end of the day (6am PST?) I would like to be able to: Type one 1-command to run test suites for ANY project I find on Github. Run autotest for ANY Github project so I can fork and make TESTABLE contributions. Build gems from the ground up with Autotest and Shoulda. For one reason or another, I hardly ever run tests for projects I clone from Github. The major reason is because unless they're using RSpec and have a Rake task to run the tests, I don't see the common pattern behind it all. I have built 3 or 4 gems writing tests with RSpec, and while I find the DSL fun, it's less than ideal because it just adds another layer/language of methods I have to learn and remember. So I'm going with Shoulda. But this isn't a question about which testing framework to choose. So the questions are: What is your, the SO reader and Github project committer, test environment setup using autotest so that whenever you git clone a gem, you can run the tests and autotest-develop them if desired? What are the guys who are writing the Paperclip Tests and Authlogic Tests doing? What is their setup? Thanks for the insight. Looking for answers that will make me a more effective tester.

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• Bash PATH: How long is too long?

  - by ajwood

  Hi, I'm currently designing a software quarantine pattern to use on Ubuntu. I'm not sure how standard "quarantine" is in this context, so here is what I hope to accomplish... Inside a particular quarantine is all of the stuff one needs to run an application (bin, share, lib, etc.). Ideally, the quarantine has no leaks, which means it's not relying on any code outside of itself on the system. A quarantine can be defined as a set of executables (and some environment settings needed to make them run). I think it will be beneficial to separate the built packages enough such that upgrading to a newer version of the quarantine won't require rebuilding the whole thing. I'll be able to update just a few packages, and then the new quarantine can use some of old parts and some of the new parts. One issue I'm wondering about is the environment variables I'll be setting up to use a particular quarantines. Is there a hard limit on how big PATH can be? (either in number of characters, or in the number of directories it contains) Might a path be so long that it affects performance? Thanks very much, Andrew p.s. Any other wisdom that might help my design would be greatly appreciated :)

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• Do I need to write a trigger for such a simple constraint?

  - by Paul Hanbury

  I really had a hard time knowing what words to put into the title of my question, as I am not especially sure if there is a database pattern related to my problem. I will try to simplify matters as much as possible to get directly to the heart of the issue. Suppose I have some tables. The first one is a list of widget types: create table widget_types ( widget_type_id number(7,0) primary key, description varchar2(50) ); The next one contains icons: create table icons ( icon_id number(7,0) primary key, picture blob ); Even though the users get to select their preferred widget, there is a predefined subset of widgets that they can choose from for each widget type. create table icon_associations ( widget_type_id number(7,0) references widget_types, icon_id number(7,0) references icons, primary key (widget_type_id, icon_id) ); create table icon_prefs ( user_id number(7,0) references users, widget_type_id number(7,0), icon_id number(7,0), primary key (user_id, widget_type_id), foreign key (widget_type_id, icon_id) references icon_associations ); Pretty simple so far. Let us now assume that if we are displaying an icon to a user who has not set up his preferences, we choose one of the appropriate images associated with the current widget. I'd like to specify the preferred icon to display in such a case, and here's where I run into my problem: alter table icon_associations add ( is_preferred char(1) check( is_preferred in ('y','n') ) ) ; I do not see how I can enforce that for each widget_type there is one, and only one, row having is_preferred set to 'y'. I know that in MySQL, I am able to write a subquery in my check constraint to quickly resolve this issue. This is not possible with Oracle. Is my mistake that this column has no business being in the icon_associations table? If not where should it go? Is this a case where, in Oracle, the constraint can only be handled with a trigger? I ask only because I'd like to go the constraint route if at all possible. Thanks so much for your help, Paul

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