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• Is the design notion of layers contrived?

  - by Bruce

  Hi all I'm reading through Eric Evans' awesome work, Domain-Driven Design. However, I can't help feeling that the 'layers' model is contrived. To expand on that statement, it seems as if it tries to shoe-horn various concepts into a specific, neat model, that of layers talking to each other. It seems to me that the layers model is too simplified to actually capture the way that (good) software works. To expand further: Evans says: "Partition a complex program into layers. Develop a design within each layer that is cohesive and that depends only on the layers below. Follow standard architectural patterns to provide loose coupling to the layers above." Maybe I'm misunderstanding what 'depends' means, but as far as I can see, it can either mean a) Class X (in the UI for example) has a reference to a concrete class Y (in the main application) or b) Class X has a reference to a class Y-ish object providing class Y-ish services (ie a reference held as an interface). If it means (a), then this is clearly a bad thing, since it defeats re-using the UI as a front-end to some other application that provides Y-ish functionality. But if it means (b), then how is the UI any more dependent on the application, than the application is dependent on the UI? Both are decoupled from each other as much as they can be while still talking to each other. Evans' layer model of dependencies going one way seems too neat. First, isn't it more accurate to say that each area of the design provides a module that is pretty much an island to itself, and that ideally all communication is through interfaces, in a contract-driven/responsibility-driven paradigm? (ie, the 'dependency only on lower layers' is contrived). Likewise with the domain layer talking to the database - the domain layer is as decoupled (through DAO etc) from the database as the database is from the domain layer. Neither is dependent on the other, both can be swapped out. Second, the idea of a conceptual straight line (as in from one layer to the next) is artificial - isn't there more a network of intercommunicating but separate modules, including external services, utility services and so on, branching off at different angles? Thanks all - hoping that your responses can clarify my understanding on this..

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• Data access pattern, combining push and pull?

  - by andlju

  I need some advice on what kind of pattern(s) I should use for pushing/pulling data into my application. I'm writing a rule-engine that needs to hold quite a large amount of data in-memory in order to be efficient enough. I have some rather conflicting requirements; It is not acceptable for the engine to always have to wait for a full pre-load of all data before it is functional. Only fetching and caching data on-demand will lead to the engine taking too long before it is running quickly enough. An external event can trigger the need for specific parts of the data to be reloaded. Basically, I think I need a combination of pushing and pulling data into the application. A simplified version of my current "pattern" looks like this (in psuedo-C# written in notepad): // This interface is implemented by all classes that needs the data interface IDataSubscriber { void RegisterData(Entity data); } // This interface is implemented by the data access class interface IDataProvider { void EnsureLoaded(Key dataKey); void RegisterSubscriber(IDataSubscriber subscriber); } class MyClassThatNeedsData : IDataSubscriber { IDataProvider _provider; MyClassThatNeedsData(IDataProvider provider) { _provider = provider; _provider.RegisterSubscriber(this); } public void RegisterData(Entity data) { // Save data for later StoreDataInCache(data); } void UseData(Key key) { // Make sure that the data has been stored in cache _provider.EnsureLoaded(key); Entity data = GetDataFromCache(key); } } class MyDataProvider : IDataProvider { List<IDataSubscriber> _subscribers; // Make sure that the data for key has been loaded to all subscribers public void EnsureLoaded(Key key) { if (HasKeyBeenMarkedAsLoaded(key)) return; PublishDataToSubscribers(key); MarkKeyAsLoaded(key); } // Force all subscribers to get a new version of the data for key public void ForceReload(Key key) { PublishDataToSubscribers(key); MarkKeyAsLoaded(key); } void PublishDataToSubscribers(Key key) { Entity data = FetchDataFromStore(key); foreach(var subscriber in _subscribers) { subscriber.RegisterData(data); } } } // This class will be spun off on startup and should make sure that all data is // preloaded as quickly as possible class MyPreloadingThread { IDataProvider _provider; MyPreloadingThread(IDataProvider provider) { _provider = provider; } void RunInBackground() { IEnumerable<Key> allKeys = GetAllKeys(); foreach(var key in allKeys) { _provider.EnsureLoaded(key); } } } I have a feeling though that this is not necessarily the best way of doing this.. Just the fact that explaining it seems to take two pages feels like an indication.. Any ideas? Any patterns out there I should have a look at?

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• Observer pattern used with decorator pattern

  - by icelated

  I want to make a program that does an order entry system for beverages. ( i will probably do description, cost) I want to use the Decorator pattern and the observer pattern. I made a UML drawing and saved it as a pic for easy viewing. This site wont let me upload as a word doc so i have to upload a pic - i hope its easily viewable.... I need to know if i am doing the UML / design patterns correctly before moving on to the coding part. Beverage is my abstract component class. Espresso, houseblend, darkroast are my concrete subject classes.. I also have a condiment decorator class milk,mocha,soy,whip. would be my observer? because they would be interested in data changes to cost? Now, would the espresso,houseblend etc, be my SUBJECT and the condiments be my observer? My theory is that Cost is a changes and that the condiments need to know the changes? So, subject = esspresso,houseblend,darkroast,etc.. // they hold cost() Observer = milk,mocha,soy,whip? // they hold cost() would be the concrete components and the milk,mocha,soy,whip? would be the decorator! So, following good software engineering practices "design to an interface and not implementation" or "identify things that change from those that dont" would i need a costbehavior interface? If you look at the UML you will see where i am going with this and see if i am implementing observer + Decorator pattern correctly? I think the decorator is correct. since, the pic is not very viewable i will detail the classes here: Beverage class(register observer, remove observer, notify observer, description) these classes are the concrete beverage classes espresso, houseblend,darkroast, decaf(cost,getdescription,setcost,costchanged) interface observer class(update) // cost? interface costbehavior class(cost) // since this changes? condiment decorator class( getdescription) concrete classes that are linked to the 2 interface s and decorator are: milk,mocha,soy,whip(cost,getdescription,update) these are my decorator/ wrapper classes. Thank you.. Is there a way to make this picture bigger?

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• DB Design Pattern - Many to many classification / categorised tagging.

  - by Robin Day

  I have an existing database design that stores Job Vacancies. The "Vacancy" table has a number of fixed fields across all clients, such as "Title", "Description", "Salary range". There is an EAV design for "Custom" fields that the Clients can setup themselves, such as, "Manager Name", "Working Hours". The field names are stored in a "ClientText" table and the data stored in a "VacancyClientText" table with VacancyId, ClientTextId and Value. Lastly there is a many to many EAV design for custom tagging / categorising the vacancies with things such as Locations/Offices the vacancy is in, a list of skills required. This is stored as a "ClientCategory" table listing the types of tag, "Locations, Skills", a "ClientCategoryItem" table listing the valid values for each Category, e.g., "London,Paris,New York,Rome", "C#,VB,PHP,Python". Finally there is a "VacancyClientCategoryItem" table with VacancyId and ClientCategoryItemId for each of the selected items for the vacancy. There are no limits to the number of custom fields or custom categories that the client can add. I am now designing a new system that is very similar to the existing system, however, I have the ability to restrict the number of custom fields a Client can have and it's being built from scratch so I have no legacy issues to deal with. For the Custom Fields my solution is simple, I have 5 additional columns on the Vacancy Table called CustomField1-5. This removes one of the EAV designs. It is with the tagging / categorising design that I am struggling. If I limit a client to having 5 categories / types of tag. Should I create 5 tables listing the possible values "CustomCategoryItems1-5" and then an additional 5 many to many tables "VacancyCustomCategoryItem1-5" This would result in 10 tables performing the same storage as the three tables in the existing system. Also, should (heaven forbid) the requirements change in that I need 6 custom categories rather than 5 then this will result in a lot of code change. Therefore, can anyone suggest any DB Design Patterns that would be more suitable to storing such data. I'm happy to stick with the EAV approach, however, the existing system has come across all the usual performance issues and complex queries associated with such a design. Any advice / suggestions are much appreciated. The DBMS system used is SQL Server 2005, however, 2008 is an option if required for any particular pattern.

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• Guilty of unsound programming

  - by TelJanini

  I was reading Robert Rossney's entry on "What's the most unsound program you've had to maintain?" found at: (What's the most unsound program you've had to maintain?) when I realized that I had inadvertently developed a near-identical application! The app consists of an HTTPListener object that grabs incoming POST requests. Based on the information in the header, I pass the body of the request to SQL Server to perform the appropriate transaction. The requests look like: <InvoiceCreate Control="389> <Invoice> <CustomerNumber>5555</CustomerNumber> <Total>300.00</Total> <RushOrder>1</RushOrder> </Invoice> </InvoiceCreate> Once it's received by the HTTPListener object, I perform the required INSERT to the Invoice table using SQL Server's built-in XML handling functionality via a stored procedure: INSERT INTO Invoice (InvoiceNumber, CustomerNumber, Total, RushOrder) SELECT @NEW_INVOICE_NUMBER, @XML.value('(InvoiceCreate/Invoice/CustomerNumber)[1]', 'varchar(10)'), @XML.value('(InvoiceCreate/Invoice/Total)[1]', 'varchar(10)'), @XML.value('(InvoiceCreate/Invoice/Total)[1]', 'varchar(10)') I then use another SELECT statement in the same stored procedure to return the value of the new Invoice Number that was inserted into the Invoices table: SELECT @NEW_INVOICE_NUMBER FOR XML PATH 'InvoiceCreateAck' I then read the generated XML using a SQL data reader object in C# and use it as the response of the HTTPListener object. My issue is, I'm noticing that Robert is indeed correct. All of my application logic exists inside the stored procedure, so I find myself having to do a lot of error-checking (i.e. validating the customer number and invoicenumber values) inside the stored procedure. I'm still a midlevel developer, and as such, am looking to improve. Given the original post, and my current architecture, what could I have done differently to improve the application? Are there any patterns or best practices that I could refer to? What approach would you have taken? I'm open to any and all criticism, as I'd like to do my part to reduce the amount of "unsound programming" in the world.

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• Should a programmer take writing lessons to enhance code expressiveness?

  - by Jose Faeti

  Given that programmers are authors and write code to express abstract thoughts and concepts, and good code should be read by other programmers without difficulties and misunderstandings, should a programmer take writing lessons to write better code? Abstracting concepts and real world problems/entities is an important part of writing good code, and a good mastery of the language used for coding should allow the programmer to express his thoughts more easily, or in a better way. Besides, when trying to write or rewrite some code to make it better, much time can be spent in deciding the names for functions, variables or data structures. I think this could also help to avoid writing code with more than one meaning, often cause of misunderstanding between different programmers. Code should always express clearly its function unambiguously.

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• What are the pre-requisites for writing .NET web services?

  - by wackytacky99

  I am very new to web development. I have been a C,C++ programmer for 5 years and I'm starting to get into the web development, writing web services, etc. I understand that basic concepts of web services. I know .Net web services can be written in VB or C#. Working with C,C++ will help getting used to writing code in C#. I do not have experience in .Net framework. I'd like to quickly get into writing .Net web services and learning on the go, without extensively spending a lot of time learning .Net framework (if possible) Any suggestions? Update - I know my way around databases and sql express in Visual Studio

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• Writing a docx file to a BLOB using Java 1.4 inside Oracle 10g

  - by Jon Renaut

  I'm trying to generate a blank docx file using Java, add some text, then write it to a BLOB that I can return to our document processing engine (a custom mess of PL/SQL and Java). I have to use the 1.4 JVM inside Oracle 10g, so no Java 1.5 stuff. I don't have a problem writing the docx to a file on my local machine, but when I try to write to BLOB, I'm getting garbage. Am I doing something dumb? Any help is appreciated. Note in the code below, all the get[name]Xml() methods return an org.w3c.dom.Document. public void save(String fileName) throws Exception { ZipOutputStream zos = new ZipOutputStream(new FileOutputStream(fileName)); addEntry(zos, getDocumentXml(), "word/document.xml"); addEntry(zos, getContentTypesXml(), "[Content_Types].xml"); addEntry(zos, getRelsXml(), "_rels/.rels"); zos.flush(); zos.close(); } public java.sql.BLOB save() throws Exception { java.sql.Connection conn = DbUtilities.openConnection(); BLOB outBlob = BLOB.createTemporary(conn, true, BLOB.DURATION_SESSION); outBlob.open(BLOB.MODE_READWRITE); ZipOutputStream zos = new ZipOutputStream(outBlob.setBinaryStream(0L)); addEntry(zos, getDocumentXml(), "word/document.xml"); addEntry(zos, getContentTypesXml(), "[Content_Types].xml"); addEntry(zos, getRelsXml(), "_rels/.rels"); zos.flush(); zos.close(); return outBlob; } private void addEntry(ZipOutputStream zos, Document doc, String fileName) throws Exception { Transformer t = TransformerFactory.newInstance().newTransformer(); ByteArrayOutputStream baos = new ByteArrayOutputStream(); t.transform(new DOMSource(doc), new StreamResult(baos)); ZipEntry ze = new ZipEntry(fileName); byte[] data = baos.toByteArray(); ze.setSize(data.length); zos.putNextEntry(ze); zos.write(data); zos.flush(); zos.closeEntry(); }

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• Writing an efficient cron job script utilizing Zend_Mail_Storage_Imap.

  - by fireeyedboy

  I'm new to the IMAP protocol and Zend_Mail_Storage and I'm writing a small php script for a cron job that should regularly poll an IMAP account and check for new messages, and send an e-mail if new messages have arrived. As you can imagine, I want to only poll the IMAP account for relevant messages, and I only want to send a new e-mail if new messages have arrived since the last polled new message. So I thought of keeping track of the last message I polled with some unique identifier for a message. But I'm a bit uncertain about whether the methods I want to utilize for this do what I expect them to do though. So my questions are: Does the iterator position of Zend_Mail_Storage_Imap actually resemble some IMAP unique identifier for messages, or is it simply only and internal position of Zend_Mail_Storage_Abstract? For instance, if I tell it to seek() to message 5 (which I stored from an earlier session) will it indeed seek to the appropriate message on the IMAP server, even if for instance messages have been deleted since last session? Would keeping track of this latest polled message id in a file suffice for a cron job that, say, polls the account every 5 or 10 minutes? Or is this too naive, and should I be using a database for instance. Or is there maybe a much easier way to keep track of such state with Zend_Mail_Storage_Abstract? Also, do I need to poll every IMAP folder? Or is everything accumulated when I poll INBOX? If you could shed some light on any of these matters, I'ld appreciate it. Thanks in advance.

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• Writing files in App_Data causes tempdata to be null

  - by RAMX

  I have a small asp.net MVC 1 web app that can store files and create directories in the App_Data directory. When the write operation succeeds, I add a message to the tempdata and do a redirectToRoute. The problem is that the tempdata is null when the action is executed. If i write the files in a directory outside of the web applications root directory, the tempdata is not null and everything works correctly. Any ideas why writing in the app_data seems to clear the tempdata ? edit: if DRS.Logic.Repository.Manager.CreateFile(path, hpf, comment) writes in the App_Data, TempData will be null in the action being redirected to. if it is a directory out of the web app root it is fine. No exceptions are being thrown. [AcceptVerbs(HttpVerbs.Post)] public ActionResult Create(int id, string path, FormCollection form) { ViewData["path"] = path; ViewData["id"] = id; HttpPostedFileBase hpf; string comment = form["FileComment"]; hpf = Request.Files["File"] as HttpPostedFileBase; if (hpf.ContentLength != 0) { DRS.Logic.Repository.Manager.CreateFile(path, hpf, comment); TempData["notification"] = "file was created"; return RedirectToRoute(new { controller = "File", action ="ViewDetails", id = id, path = path + Path.GetFileName(hpf.FileName) }); } else { TempData["notification"] = "No file were selected."; return View(); } }

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• Access Violation When Writing Dynamic 2D Array... Sometimes

  - by Shraptnel

  This program is meant to generate a dynamic array, however it gives an access violation error when writing when given certain dimensions. Eg: R = 6, C = 5 crashes, but then R = 5, C = 6 doesn't. In case your wondering, it isn't my homework to "fix" this broken program, this is the method we were taught in class. Also part of my assessment is to use this method, so vectors are out. Thanks in advance! #include <iostream> using namespace std; int main(){ const int R = 6; const int C = 5; char **d; d = new char *[R]; for(int i=0; i<C; ++i){ d[i] = new char[C]; } //initialise for(int i=0; i<R; ++i){ for(int j=0; j<C; ++j){ d[i][j] = 'd'; cout<<d[i][j]; } cout<<endl; } cout<<endl; system("pause"); return 0; }

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• Writing PHP extension - Unable to load dynamic library

  - by Luke

  I'm writing a PHP extension similar to V8JS. The goal, like V8JS, is to embed the V8 engine into PHP so I can execute sandboxed JavaScript code in PHP. (The implementation is different.) The extension compiles fine, but when I attempt to run it I get: PHP Warning: PHP Startup: Unable to load dynamic library '/phpdev/lib/php/extensions/debug-zts-20090626/v8php.so' - dlopen(/phpdev/lib/php/extensions/debug-zts-20090626/v8php.so, 9): Symbol not found: __ZN2v88internal8Snapshot13context_size_E Referenced from: /phpdev/lib/php/extensions/debug-zts-20090626/v8php.so Expected in: flat namespace PHP is compiled with the prefix /phpdev (with debug and maintainer flags). v8 is compiled in /v8/ with gyp with the commands make dependencies and make x64 which produced /v8/out/x64.release and /v8/out/x64.debug. I soft-linked the header files from /v8/include to /phpdev/include and libv8_base.a from /v8/out/x64.release/libv8_base.a to /phpdev/lib/libv8.a. This is my config.m4 file: PHP_ARG_ENABLE(v8php, [V8PHP], [--enable-v8php Include V8 JavaScript Engine]) if test $PHP_V8PHP != "no"; then SEARCH_PATH="$prefix /usr/local /usr" SEARCH_FOR="/include/v8.h" if test -r $PHP_V8PHP/$SEARCH_FOR; then V8_DIR=$PHP_V8PHP else AC_MSG_CHECKING([for V8 files in default path]) for i in $SEARCH_PATH ; do if test -r $i/$SEARCH_FOR; then V8_DIR=$i AC_MSG_RESULT(found in $i) fi done fi if test -z "$V8_DIR"; then AC_MSG_RESULT([not found]) AC_MSG_ERROR([Unable to locate V8]) fi PHP_ADD_INCLUDE($V8_DIR/include) PHP_SUBST(V8PHP_SHARED_LIBADD) PHP_ADD_LIBRARY_WITH_PATH(v8, $V8_DIR/$PHP_LIBDIR, V8PHP_SHARED_LIBADD) PHP_REQUIRE_CXX() PHP_NEW_EXTENSION(v8php, v8php.cc v8_class.cc, $ext_shared) fi What am I doing wrong?

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• Reading,Writing, Editing BLOBS through DataTables and DataRows

  - by Soham

  Consider this piece of code: DataSet ds = new DataSet(); SQLiteDataAdapter Da = new SQLiteDataAdapter(Command); Da.Fill(ds); DataTable dt = ds.Tables[0]; bool PositionExists; if (dt.Rows.Count > 0) { PositionExists = true; } else { PositionExists = false; } if (PositionExists) { //dt.Rows[0].Field<>("Date") } Here the "Date" field is a BLOB. My question is, a. Will reading through the DataAdapter create any problems later on, when I am working with BLOBS? More, specifically, will it read the BLOB properly? b. This was the read part.Now when I am writing the BLOB to the DB,its a queue actually. I.e I am trying to store a queue in MySQLite using a BLOB. Will Conn.ExecuteNonQuery() serve my purpose? c. When I am reading the BLOB back from the DB, can I edit it as the original datatype, it used to be in C# environment i.e { Queue - BLOB - ? } {C# -MySQL - C# } So in this context, Date field was a queue, I wrote it back as a BLOB, when reading it back, can I access it(and edit) as a queue? Thank You. Soham

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• Is using a StringBuilder for writing XML ok?

  - by Jack Lawson

  It feels dirty. But maybe it isn't... is it ok to use a StringBuilder for writing XML? My gut instinct says "although this feels wrong, it's probably pretty darn performant because it's not loading extra libraries and overhead." Here's what it looks like. I'm building an OpenSearch XML doc based on the domain you come in from. public void ProcessRequest(HttpContext context) { context.Response.ContentType = "text/xml"; string domain = WebUtils.ReturnParsedSourceUrl(null); //returns something like www.sample.com string cachedChan = context.Cache[domain + "_opensearchdescription"] as String; if (cachedChan == null) { StringBuilder sb = new StringBuilder(); sb.Append("<?xml version=\"1.0\" encoding=\"UTF-8\"?>"); sb.Append("<OpenSearchDescription xmlns=\"http://a9.com/-/spec/opensearch/1.1/\" xmlns:moz=\"http://www.mozilla.org/2006/browser/search/\">"); sb.Append(" <ShortName>Search</ShortName>"); sb.Append(" <Description>Use " + domain + " to search.</Description>"); sb.Append(" <Contact>[email protected]</Contact>"); sb.Append(" <Url type=\"text/html\" method=\"get\" template=\"http://" + domain + "/Search.aspx?q={searchTerms}\" />"); sb.Append(" <moz:SearchForm>http://" + domain + "/Search.aspx</moz:SearchForm>"); sb.Append(" <Image height=\"16\" width=\"16\" type=\"image/x-icon\">http://" + domain + "/favicon.ico</Image>"); sb.Append("</OpenSearchDescription>"); cachedChan = sb.ToString(); context.Cache.Insert(domain + "_opensearchdescription", cachedChan, null, DateTime.Now.AddDays(14), TimeSpan.Zero); } context.Response.Write(cachedChan); }

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• Writing Russian in XML

  - by zavié

  Hi, I am writing a Xml Tag Renamer class with Java which reads in a XML, renames the tags and write them back into another XML file using DocumentBuilderFactory and TransformerFactory (text nodes are preserved). It worked fine before with German and English texts, until today, when I tried to rename a XML file with russian text. Instead of the source texts I got ????? in the newly created XML file. I've tried setting Encoding Any idea how to correct this? Thanks! PS. Strings were correct before entering TransformerFactory, as I checked in the debugger. I've tried setting OutputKeys.ENCODING to UTF-8 and ISO-8859-5. None of them helped. The Transformer part: // Output the XML // Set up a transformer TransformerFactory transFactory = TransformerFactory.newInstance(); Transformer transformer = transFactory.newTransformer(); transformer.setOutputProperty(OutputKeys.OMIT_XML_DECLARATION, "no"); // Fix to a bug about indent in transformer transformer.setOutputProperty ("{http://xml.apache.org/xslt}indent-amount", "4"); transformer.setOutputProperty(OutputKeys.INDENT, "yes"); // TODO encoding parameter transformer.setOutputProperty(OutputKeys.ENCODING, "UTF-8"); // Create string from xml tree StringWriter sw = new StringWriter(); StreamResult result = new StreamResult(sw); DOMSource source = new DOMSource(doc); transformer.transform(source, result); String xmlString = sw.toString(); xmlString.replaceAll("\n", System.getProperty("line.separator")); // Write to file BufferedWriter output = new BufferedWriter(new FileWriter(outputPath)); output.write(xmlString); output.close();

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• MSBuild - Writing Escape Characters to Files

  - by Richm7

  I've got a very similar scenario to the one described in this post. It describes how to load the contents of a file that contains properties & items, making sure they're resolved as part of the process. I'm doing the same thing except writing the contents away to another text file (generally .ini file). In short I'd start by importing a project / propertygroup which contains this text: ; ----------- [heading] setting1=$(FirstValue) setting2=$(SecondValue) setting3=list;of;values;delimited;by;semicolons setting4=bla bla bla ; ----------- & hopefully write it away to a new .ini file containing the following: ; ----------- [heading] setting1=value resolved by msbuild setting2=another value resolved by msbuild setting3=list;of;values;delimited;by;semicolons setting4=bla bla bla ; ----------- Only problem is that some files will contain semicolons. I can live without comments, but they're also used as part of values e.g. in lists. This is the result of using the WriteLinesToFile task. The semicolons are treated as escape characters & result in new lines, so the value of 'setting3' in the above example would be split over 6 lines. Is there a way around this without implementing my own task? Thanks in advance for the help!

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• python: how to design a container with elements that must reference their container

  - by Luke404

  (the title is admittedly not that great. Please forgive my English, this is the best I could think of) I'm writing a python script that will manage email domains and their accounts, and I'm also a newby at OOP design. My two (related?) issues are: the Domain class must do special work to add and remove accounts, like adding/removing them to the underlying implementation how to manage operations on accounts that must go through their container To solve the former issue I'd add a factory method to the Domain class that'll build an Account instance in that domain, and a 'remove' (anti-factory?) method to handle deletions. For the latter this seems to me "anti-oop" since what would logically be an operation on an Account (eg, change password) must always reference the containing Domain. Seems to me that I must add to the Account a reference back to the Domain and use that to get data (like the domain name) or call methods on the Domain class. Code example (element uses data from the container) that manages an underlying Vpopmail system: class Account: def __init__(self, name, password, domain): self.name = name self.password = password self.domain = domain def set_password(self, password): os.system('vpasswd %s@%s %s' % (self.name, self.domain.name, password) self.password = password class Domain: def __init__(self, domain_name): self.name = domain_name self.accounts = {} def create_account(self, name, password): os.system('vadduser %s@%s %s' % (name, self.name, password)) account = Account(name, password, self) self.accounts[name] = account def delete_account(self, name): os.system('vdeluser %s@%s' % (name, self.name)) del self.accounts[name] another option would be for Account.set_password to call a Domain method that would do the actual work - sounds equally ugly to me. Also note the duplication of data (account name also as dict key), it sounds logical (account names are "primary key" inside a domain) but accounts need to know their own name.

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• Writing a JMS Publisher without "public static void main"

  - by The Elite Gentleman

  Hi guys, Every example I've seen on the web, e.g. http://www.codeproject.com/KB/docview/jms_to_jms_bridge_activem.aspx, creates a publisher and subscriber with a public static void main method. I don't think that'll work for my web application. I'm learning JMS and I've setup Apache ActiveMQ to run on JBoss 5 and Tomcat 6 (with no glitches). I'm writing a messaging JMS service that needs to send email asynchronously. I've already written a JMS subscriber that receives the message (the class inherits MessageListener). My question is simple: How do I write a publisher that will so that my web applications can call it? Does it have to be published somewhere? My thought is to create a publisher with a no-attribute constructor (in there) and get the MessageQueue Factory, etc. from the JNDI pool (in the constructor). Is my idea correct? How do I subscribe my subscriber to the Queue Receiver? (So far, the subscriber has no constructor, and if I write a constructor, do I always subscribe myself to the Queue receiver?) Thanks for your help, sorry if my terminology is not up to scratch, there are too many java terminologies that I get lost sometimes (maybe a java GPS will do! :-) ) PS Is there a tutorial out there that explains how to write a "better" (better can mean anything, but in my case it's all about performance in high demand requests) JMS Publisher and Subscriber that I can run on Application Server such as JBoss or Glassfish? Don't forget that the JMS application will needs a "guarantee" uptime as many applications will use this.

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• Writing to a file in Python inserts null bytes

  - by Javier Badia

  I'm writing a todo list program. It keeps a file with a thing to do per line, and lets the user add or delete items. The problem is that for some reason, I end up with a lot of zero bytes at the start of the file, even though the item is correctly deleted. I'll show you a couple of screenshots to make sure I'm making myself clear. This is the file in Notepad++ before running the program: This is the file after deleting item 3 (counting from 1): This is the relevant code. The actual program is bigger, but running just this part triggers the error. import os TODO_FILE = r"E:\javi\code\Python\todo-list\src\todo.txt" def del_elems(f, delete): """Takes an open file and either a number or a list of numbers, and deletes the lines corresponding to those numbers (counting from 1).""" if isinstance(delete, int): delete = [delete] lines = f.readlines() f.truncate(0) counter = 1 for line in lines: if counter not in delete: f.write(line) counter += 1 f = open(TODO_FILE, "r+") del_elems(f, 3) f.close() Could you please point out where's the mistake?

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• Manually Writing the HTML in TWebBrowser Pt. 2

  - by nomad311

  As the name suggests this is a continuation (sort of) of http://stackoverflow.com/questions/2784679/manually-writing-the-html-in-twebbrowser This time around I'm trying to add some auto-refresh logic to the HTML I get. I have pieced together an approach from several sources (see below). In short, I am trying to locate the title node and add a meta node after it (in the HTML head node). But, I get an access violation. Here is the source: iHtmlDoc := IHTMLDocument3(WebBrowser1.Document); iHtmlEleTitle := IHTMLElement2(iHtmlDoc.getElementsByName('title').item(0, 0)); iHtmlEle := IHTMLElement2(IHTMLDocument2(iHtmlDoc).createElement(Format('<meta http-equiv="refresh" content="%d">', [1]))); iHtmlEleTitle.insertAdjacentElement('afterEnd', IHTMLElement(iHtmlEle)); And A (technically not functionally) different way of doing it ...casting is slightly different here: IHTMLElement2(IHtmlDocument3(WebBrowser1.Document).getElementsByName('title').item(0, 0)).insertAdjacentElement('afterEnd', IHTMLDocument2(WebBrowser1.Document).createElement(Format('<meta http-equiv="refresh" content="%d">', [VPI_ISSUANCE_AUTO_RELOAD]))); Again all I get from Delphi is a access exception, and I fished through MSDN documentation on it, but now I'm hoping someone out there has gone through the same and has some insight. Any help? Sources (I think this is all of them): http://webdesign.about.com/od/metataglibraries/a/aa080300a.htm (auto-reload) http://delphi.about.com/od/adptips2005/qt/webbrowserhtml.htm (web browser document as an HTML document) http://msdn.microsoft.com/en-us/library/system.windows.forms.htmlelement.insertadjacentelement(VS.80).aspx (GetElementsByName) http://www.experts-exchange.com/Web_Development/Components/ActiveX/Q_26131034.html (insertAdjacentElement) http://www.experts-exchange.com/Programming/Languages/Pascal/Delphi/Q_23407977.html (GetElementsByName)

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• Require help in Writing Query

  - by harigm

  The following image have been uploaded to show what I am trying to do and what I wanted out of it Can any one help me write the Query to get the results what I want Please check the following SELECT * FROM KPT WHERE PROPERTY_ID IN (SELECT PROPERTY_ID FROM khata_header WHERE DIV_ID = 3 and RECORD_STATUS = 0) and CHALLAN_NO > 42646 The above is the query I have written and I have got the following result set ID CHALLAN_NO PROPERTY_ID SITE_NO TOTAL_AMOUNT ----- ------------- -------------- ------------------- --------------- 1242 42757 3103010141 296 595 1243 63743 3204190257 483 594 1244 63743 3204190257 483 594 1334 43395 3217010223 1088 576 1421 524210 3320050416 (null) (null) 1422 524210 3320050416 (null) (null) 1560 564355 3320021408 (null) (null) 1870 516292 3320040420 (null) (null) 1940 68357 3217100104 139 1153 1941 68357 3217100104 139 1153 2002 56256 3320100733 511 4430 2003 56256 3320100733 511 4430 2004 66488 3217040869 293 3094 2005 66488 3217040869 293 3094 2016 64571 3217040374 (null) (null) 2036 523122 3320020352 (null) (null) 2039 65682 3217040021 273 919 In my resultset, I am getting the PropertyId repeated, since there are multilple entries, How Can I know How many have been repeated What are those Property Id which have repeated more than 2 times. Little Back ground about the tables are PROPERTY_ID is the FK in the KPT PROPERTY_ID is the PK in KH I am writing a subquery to get the Result, so I am stuck I dont know how to get my results Please help

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• how to use "tab space" while writing in text file

  - by Manu

  SimpleDateFormat formatter = new SimpleDateFormat("ddMMyyyy_HHmmSS"); String strCurrDate = formatter.format(new java.util.Date()); String strfileNm = "Cust_Advice_" + strCurrDate + ".txt"; String strFileGenLoc = strFileLocation + "/" + strfileNm; String strQuery="select name, age, data from basetable; try { stmt = conn.createStatement(); System.out.println("Query is -> " + strQuery); rs = stmt.executeQuery(strQuery); File f = new File(strFileGenLoc); OutputStream os = (OutputStream)new FileOutputStream(f); String encoding = "UTF8"; OutputStreamWriter osw = new OutputStreamWriter(os, encoding); BufferedWriter bw = new BufferedWriter(osw); while (rs.next() ) { bw.write(rs.getString(1)==null? "":rs.getString(1)); bw.write(" "); bw.write(rs.getString(2)==null? "":rs.getString(2)); bw.write(" "); } bw.flush(); bw.close(); } catch (Exception e) { System.out.println( "Exception occured while getting resultset by the query"); e.printStackTrace(); } finally { try { if (conn != null) { System.out.println("Closing the connection" + conn); conn.close(); } } catch (SQLException e) { System.out.println( "Exception occured while closing the connection"); e.printStackTrace(); } } return objArrayListValue; } i need "one tab space" in between each column(while writing to text file). like manu 25 data1 manc 35 data3 in my code i use bw.write(" ") for creating space between each column. how to use "one tab space" in that place instead of giving "space".

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• What is the best testing pattern for checking that parameters are being used properly?

  - by Joseph

  I'm using Rhino Mocks to try to verify that when I call a certain method, that the method in turn will properly group items and then call another method. Something like this: //Arrange var bucketsOfFun = new BucketGame(); var balls = new List<IBall> { new Ball { Color = Color.Red }, new Ball { Color = Color.Blue }, new Ball { Color = Color.Yellow }, new Ball { Color = Color.Orange }, new Ball { Color = Color.Orange } }; //Act bucketsOfFun.HaveFunWithBucketsAndBalls(balls); //Assert ??? Here is where the trouble begins for me. My method is doing something like this: public void HaveFunWithBucketsAndBalls(IList<IBall> balls) { //group all the balls together according to color var blueBalls = GetBlueBalls(balls); var redBalls = GetRedBalls(balls); // you get the idea HaveFunWithABucketOfBalls(blueBalls); HaveFunWithABucketOfBalls(redBalls); // etc etc with all the different colors } public void HaveFunWithABucketOfBalls(IList<IBall> colorSpecificBalls) { //doing some stuff here that i don't care about //for the test i'm writing right now } What I want to assert is that each time I call HaveFunWithABucketOfBalls that I'm calling it with a group of 1 red ball, then 1 blue ball, then 1 yellow ball, then 2 orange balls. If I can assert that behavior then I can verify that the method is doing what I want it to do, which is grouping the balls properly. Any ideas of what the best testing pattern for this would be?

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• Writing language converter in ANTLR

  - by Stefan

  I'm writing a converter between some dialects of the same programming language. I've found a grammar on the net - it's complex and handles all the cases. Now I'm trying to write the appropriate actions. Most of the input is just going to be rewritten to output. What I need to do is parse function calls, do my magic (rename function, reorder arguments, etc) and write it. I'm using AST as output. When I come across a function call, I build a custom object structure (from classes defined in my target language), call the appropriate function and I have a string that represents the transformed function that I want to get. The problem is, what I'm supposed to do with that string? I'd like to replace the .text attribute of the enclosing rule, but setText() is only available on lexer rules and the rule's .text attribute is read-only. How to solve this problem? program : statement_list { output = $statement_list.text; } ; //... statement : expression_statement // ... ; expression_statement : function_call // ... ; function_call : ID '(' { /* build the object, assign name */ Function function = new Function(); //... } ( arg1 = expression { /* add first parameter */ } ( ',' arg2 = expression { /* add the rest of parameters */ } )* )? ')' { /* convert the function call */ string converted = Tools.Convert(function); // $setText(converted); // doesn't work // $functionCall.text = converted; // doesn't work } ;

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• Disposing underlying object from finalizer in an immutable object

  - by Juan Luis Soldi

  I'm trying to wrap around Awesomium and make it look to the rest of my code as close as possible to NET's WebBrowser since this is for an existing application that already uses the WebBrowser. In this library, there is a class called JSObject which represents a javascript object. You can get one of this, for instance, by calling the ExecuteJavascriptWithResult method of the WebView class. If you'd call it like myWebView.ExecuteJavascriptWithResult("document", string.Empty).ToObject(), then you'd get a JSObject that represents the document. I'm writing an immutable class (it's only field is a readonly JSObject object) called JSObjectWrap that wraps around JSObject which I want to use as base class for other classes that would emulate .NET classes such as HtmlElement and HtmlDocument. Now, these classes don't implement Dispose, but JSObject does. What I first thought was to call the underlying JSObject's Dispose method in my JSObjectWrap's finalizer (instead of having JSObjectWrap implement Dispose) so that the rest of my code can stay the way it is (instead of having to add using's everywhere and make sure every JSObjectWrap is being properly disposed). But I just realized if more than two JSObjectWrap's have the same underlying JSObject and one of them gets finalized this will mess up the other JSObjectWrap. So now I'm thinking maybe I should keep a static Dictionary of JSObjects and keep count of how many of each of them are being referenced by a JSObjectWrap but this sounds messy and I think could cause major performance issues. Since this sounds to me like a common pattern I wonder if anyone else has a better idea.

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