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• Spring with Castor - Null Pointer Exception when initialising Application Context

  - by babyangel86

  Hi, I'm trying to register my castor mapping files with spring and I appear to be getting a null pointer exception. In my application context I have: <bean id="xmlContext" class="org.castor.spring.xml.XMLContextFactoryBean"> <property name="mappingLocations"> <list> <value>DistributionSamplerMappings.xml</value> </list> </property> <property name="castorProperties"> <props> <prop key="org.exolab.castor.xml.strictelements">false</prop> </props> </property> </bean> <bean id="marshaller" class="org.castor.spring.xml.CastorMarshallerFactoryBean"> <property name="xmlContext"><ref local="xmlContext"/></property> </bean> <bean id="unmarshaller" class="org.castor.spring.xml.CastorUnmarshallerFactoryBean"> <property name="xmlContext"> <ref local="xmlContext"/></property> <property name="ignoreExtraElements"><value>true</value></property> <property name="ignoreExtraAttributes"><value>true</value></property> </bean> Where DistributionSamplerMappings.xml lives in the same dir as the application context. I've tried using the spring-xml jar 1.2.1 and 1.5.3. but none of them seem to help. The exception being thrown back is: SEVERE: Context initialization failed org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'xmlContext' defined in ServletContext resource [/WEB-INF/applicationContext.xml]: Invocation of init method failed; nested exception is java.lang.NullPointerException at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.initializeBean(AbstractAutowireCapableBeanFactory.java:1338) at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:473) at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory$1.run(AbstractAutowireCapableBeanFactory.java:409) at java.security.AccessController.doPrivileged(Native Method) at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:380) at org.springframework.beans.factory.support.AbstractBeanFactory$1.getObject(AbstractBeanFactory.java:264) at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:222) at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:261) at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:185) at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:164) at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:423) at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:728) at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:380) at org.springframework.web.context.ContextLoader.createWebApplicationContext(ContextLoader.java:255) at org.springframework.web.context.ContextLoader.initWebApplicationContext(ContextLoader.java:199) at org.springframework.web.context.ContextLoaderListener.contextInitialized(ContextLoaderListener.java:45) at org.apache.catalina.core.StandardContext.listenerStart(StandardContext.java:3830) at org.apache.catalina.core.StandardContext.start(StandardContext.java:4337) at org.apache.catalina.core.ContainerBase.start(ContainerBase.java:1045) at org.apache.catalina.core.StandardHost.start(StandardHost.java:719) at org.apache.catalina.core.ContainerBase.start(ContainerBase.java:1045) at org.apache.catalina.core.StandardEngine.start(StandardEngine.java:443) at org.apache.catalina.core.StandardService.start(StandardService.java:516) at org.apache.catalina.core.StandardServer.start(StandardServer.java:710) at org.apache.catalina.startup.Catalina.start(Catalina.java:566) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source) at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source) at java.lang.reflect.Method.invoke(Unknown Source) at org.apache.catalina.startup.Bootstrap.start(Bootstrap.java:288) at org.apache.catalina.startup.Bootstrap.main(Bootstrap.java:413) Caused by: java.lang.NullPointerException at org.castor.spring.xml.XMLContextFactoryBean.afterPropertiesSet(XMLContextFactoryBean.java:118) at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.invokeInitMethods(AbstractAutowireCapableBeanFactory.java:1369) at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.initializeBean(AbstractAutowireCapableBeanFactory.java:1335) ... 30 more I'm using Spring 2.5.6 and Castor 1.3.1. Looking around I find I'm not the only one who has had this problem, but I don't seem to be able to find a solution. Any help would be much appreciated.

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• Searching over a templated tree

  - by floatingfrisbee

  So I have 2 interfaces: A node that can have children public interface INode { IEnumeration<INode> Children { get; } void AddChild(INode node); } And a derived "Data Node" that can have data associated with it public interface IDataNode<DataType> : INode { DataType Data; IDataNode<DataType> FindNode(DataType dt); } Keep in mind that each node in the tree could have a different data type associated with it as its Data (because the INode.AddChild function just takes the base INode) Here is the implementation of the IDataNode interface: internal class DataNode<DataType> : IDataNode<DataType> { List<INode> m_Children; DataNode(DataType dt) { Data = dt; } public IEnumerable<INode> Children { get { return m_Children; } } public void AddChild(INode node) { if (null == m_Children) m_Children = new List<INode>(); m_Children.Add(node); } public DataType Data { get; private set; } Question is how do I implement the FindNode function without knowing what kinds of DataType I will encounter in the tree? public IDataNode<DataType> FindNode(DataType dt) { throw new NotImplementedException(); } } As you can imagine something like this will not work out public IDataNode<DataType> FindNode(DataType dt) { IDataNode<DataType> result = null; foreach (var child in Children) { if (child is IDataNode<DataType>) { var datachild = child as IDataNode<DataType>; if (datachild.Data.Equals(dt)) { result = child as IDataNode<DataType>; break; } } else { // What?? } } return result; } Is my only option to do this when I know what kinds of DataType a particular tree I use will have? Maybe I am going about this in the wrong way, so any tips are appreciated. Thanks!

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• How to store wiki sites (vcs)

  - by Eugen

  Hello, as a personal project I am trying to write a wiki with the help of django. I'm a beginner when it comes to web development. I am at the (early) point where I need to decide how to store the wiki sites. I have three approaches in mind and would like to know your suggestion. Flat files I considered a flat file approach with a version control system like git or mercurial. Firstly, I would have some example wikis to look at like http://hatta.sheep.art.pl/. Secondly, the vcs would probably deal with editing conflicts and keeping the edit history, so I would not have to reinvent the wheel. And thirdly, I could probably easily clone the wiki repository, so I (or for that matter others) can have an offline copy of the wiki. On the other hand, as far as I know, I can not use django models with flat files. Then, if I wanted to add fields to a wiki site, like a category, I would need to somehow keep a reference to that flat file in order to associate the fields in the database with the flat file. Besides, I don't know if it is a good idea to have all the wiki sites in one repository. I imagine it is more natural to have kind of like a repository per wiki site resp. file. Last but not least, I'm not sure, but I think using flat files would limit my deploying capabilities because web hosts maybe don't allow creating files (I'm thinking, for example, of Google App Engine) Storing in a database By storing the wiki sites in the database I can utilize django models and associate arbitrary fields with the wiki site. I probably would also have an easier life deploying the wiki. But I would not get vcs features like history and conflict resolving per se. I searched for django-extensions to help me and I found django-reversion. However, I do not fully understand if it fit my needs. Does it track model changes like for example if I change the django model file, or does it track the content of the models (which would fit my need). Plus, I do not see if django reversion would help me with edit conflicts. Storing a vcs repository in a database field This would be my ideal solution. It would combine the advantages of both previous approaches without the disadvantages. That is; I would have vcs features but I would save the wiki sites in a database. The problem is: I have no idea how feasible that is. I just imagine saving a wiki site/source together with a git/mercurial repository in a database field. Yet, I somehow doubt database fields work like that. So, I'm open for any other approaches but this is what I came up with. Also, if you're interested, you can find the crappy early test I'm working on here http://github.com/eugenkiss/instantwiki-test

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• nhibernate sql Express connection issue - error: 26 - Error Locating Server/Instance Specified

  - by frosty

  I can connect fine with normal ado.net. However i get the following error when i tried to connect nHibernate. hibernate.cfg.xml <?xml version="1.0" encoding="utf-8" ?> <hibernate-configuration xmlns="urn:nhibernate-configuration-2.2"> <session-factory> <property name="dialect">NHibernate.Dialect.MsSql2005Dialect</property> <property name="connection.provider">NHibernate.Connection.DriverConnectionProvider</property> <property name="connection.driver_class">NHibernate.Driver.SqlClientDriver</property> <property name="connection.connection_string">Server=xxxxx\SQLEXPRESS; Database=xxxxx; User ID=xxxxx; Password=xxxxx; Trusted_Connection=True</property> <property name="proxyfactory.factory_class">NHibernate.ByteCode.Castle.ProxyFactoryFactory, NHibernate.ByteCode.Castle</property> <property name="show_sql">true</property> </session-factory> </hibernate-configuration> Server error A network-related or instance-specific error occurred while establishing a connection to SQL Server. The server was not found or was not accessible. Verify that the instance name is correct and that SQL Server is configured to allow remote connections. (provider: SQL Network Interfaces, error: 26 - Error Locating Server/Instance Specified) Full stack [SqlException (0x80131904): A network-related or instance-specific error occurred while establishing a connection to SQL Server. The server was not found or was not accessible. Verify that the instance name is correct and that SQL Server is configured to allow remote connections. (provider: SQL Network Interfaces, error: 26 - Error Locating Server/Instance Specified)] System.Data.SqlClient.SqlInternalConnection.OnError(SqlException exception, Boolean breakConnection) +4845255 System.Data.SqlClient.TdsParser.ThrowExceptionAndWarning(TdsParserStateObject stateObj) +194 System.Data.SqlClient.TdsParser.Connect(ServerInfo serverInfo, SqlInternalConnectionTds connHandler, Boolean ignoreSniOpenTimeout, Int64 timerExpire, Boolean encrypt, Boolean trustServerCert, Boolean integratedSecurity, SqlConnection owningObject) +4858557 System.Data.SqlClient.SqlInternalConnectionTds.AttemptOneLogin(ServerInfo serverInfo, String newPassword, Boolean ignoreSniOpenTimeout, Int64 timerExpire, SqlConnection owningObject) +90 System.Data.SqlClient.SqlInternalConnectionTds.LoginNoFailover(String host, String newPassword, Boolean redirectedUserInstance, SqlConnection owningObject, SqlConnectionString connectionOptions, Int64 timerStart) +342 System.Data.SqlClient.SqlInternalConnectionTds.OpenLoginEnlist(SqlConnection owningObject, SqlConnectionString connectionOptions, String newPassword, Boolean redirectedUserInstance) +221 System.Data.SqlClient.SqlInternalConnectionTds..ctor(DbConnectionPoolIdentity identity, SqlConnectionString connectionOptions, Object providerInfo, String newPassword, SqlConnection owningObject, Boolean redirectedUserInstance) +189 System.Data.SqlClient.SqlConnectionFactory.CreateConnection(DbConnectionOptions options, Object poolGroupProviderInfo, DbConnectionPool pool, DbConnection owningConnection) +185 System.Data.ProviderBase.DbConnectionFactory.CreatePooledConnection(DbConnection owningConnection, DbConnectionPool pool, DbConnectionOptions options) +31 System.Data.ProviderBase.DbConnectionPool.CreateObject(DbConnection owningObject) +433 System.Data.ProviderBase.DbConnectionPool.UserCreateRequest(DbConnection owningObject) +66 System.Data.ProviderBase.DbConnectionPool.GetConnection(DbConnection owningObject) +499 System.Data.ProviderBase.DbConnectionFactory.GetConnection(DbConnection owningConnection) +65 System.Data.ProviderBase.DbConnectionClosed.OpenConnection(DbConnection outerConnection, DbConnectionFactory connectionFactory) +117 System.Data.SqlClient.SqlConnection.Open() +122 NHibernate.Connection.DriverConnectionProvider.GetConnection() +102 NHibernate.Tool.hbm2ddl.SuppliedConnectionProviderConnectionHelper.Prepare() +15 NHibernate.Tool.hbm2ddl.SchemaMetadataUpdater.GetReservedWords(Dialect dialect, IConnectionHelper connectionHelper) +65 NHibernate.Tool.hbm2ddl.SchemaMetadataUpdater.Update(ISessionFactory sessionFactory) +80 NHibernate.Impl.SessionFactoryImpl..ctor(Configuration cfg, IMapping mapping, Settings settings, EventListeners listeners) +599 NHibernate.Cfg.Configuration.BuildSessionFactory() +87 XXX.Domain.Repositories.NHibernateHelper.get_SessionFactory() in D:\dev\MyProject\XXX\XXX.Domain\Repositories\NHibernateHelper.cs:23 XXX.Domain.Repositories.NHibernateHelper.OpenSession() in D:\dev\MyProject\XXX\XXX.Domain\Repositories\NHibernateHelper.cs:31 XXX.Domain.Repositories.EntryRepository.GetCountByGmapId(Int32 gmapId) in D:\dev\MyProject\XXX\XXX.Domain\Repositories\EntryRepository.cs:152 XXX.Controls.Activity.BindRepeater(Int32 id) in D:\dev\MyProject\XXX\XXX.Controls\Activity.ascx.cs:58 XXX.Controls.Activity.DropDownListMaps_SelectedIndexChanged(Object sender, EventArgs e) in D:\dev\MyProject\XXX\XXX.Controls\Activity.ascx.cs:75 System.Web.UI.WebControls.ListControl.OnSelectedIndexChanged(EventArgs e) +111 System.Web.UI.WebControls.DropDownList.RaisePostDataChangedEvent() +134 System.Web.UI.WebControls.DropDownList.System.Web.UI.IPostBackDataHandler.RaisePostDataChangedEvent() +10 System.Web.UI.Page.RaiseChangedEvents() +165 System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +1485

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• Xsd recursion of complexTypes

  - by Hatch

  I am just learning XML/XSD and am struggling with the implementation of an XML-schema which models a folder structure. What I had in mind was defining a complexType for the folder which can have additional folder instances that represent subfolders. Using the xsd schema validator here always returns that the schema is invalid. I tried defining the complexType up front and then using the ref keyword for subfolders: <xs:complexType name="tFolder"> <xs:sequence> <xs:element name="Path" type="tFolderType" msdata:Ordinal="0" /> <xs:element ref="Folder" minOccurs="0" maxOccurs="unbounded" /> <xs:element name="File" nillable="true" minOccurs="0" maxOccurs="unbounded"> <xs:complexType> <xs:simpleContent msdata:ColumnName="File_Text" msdata:Ordinal="0"> <xs:extension base="xs:string"> </xs:extension> </xs:simpleContent> </xs:complexType> </xs:element> </xs:sequence> <xs:attribute name="Type" type="tFolderType" /> As for the element itself: <xs:element name="Folder" type="tFolder" /> The error returned by the validator is: "Cannot resolve the name 'Folder' to a(n) 'element declaration' component." and the error occurs at the line <xs:element ref="Folder" minOccurs="0" maxOccurs="unbounded" /\> Defining the complexType within the element itself yields the exact same error: <xs:element name="Folder"> <xs:complexType> <xs:sequence> <xs:element name="Path" type="tFolderType" msdata:Ordinal="0" /> <xs:element ref="Folder" minOccurs="0" maxOccurs="unbounded" /> <xs:element name="File" nillable="true" minOccurs="0" maxOccurs="unbounded"> <xs:complexType> <xs:simpleContent msdata:ColumnName="File_Text" msdata:Ordinal="0"> <xs:extension base="xs:string"> </xs:extension> </xs:simpleContent> </xs:complexType> </xs:element> </xs:sequence> <xs:attribute name="Type" type="tFolderType" /> </xs:complexType> </xs:element> What I've read, this kind of recursion should work using ref. Can anyone tell me what I've done wrong? Maybe the xsd validator is just faulty? If so, does anyone know a better alternative? I've tried using the one from w3.org as well, but it seems to be taken offline...

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• Suggestions for designing large-scale Java webapp from the group up

  - by Chris Thompson

  Hi all, I'm about to start developing a large-scale system and I'm struggling with which direction to proceed. I've done plenty of Java web apps before and I have plenty of experience with servlet containers and GWT and some experience with Spring. The problem is most of my webapps have been thrown together just to be a proof of concept and what I'm struggling with is what set of frameworks to use. I need to have both a browser based application as well as a web service designed to support access from mobile devices (Android and iPhone for now). Ideally, I'd like to design this system in such a way that I don't end up rewriting all of my servlets for each client (browser and phone) although I don't mind having some small checks in there to properly format the data. In addition, although I'm the only developer now, that won't necessarily be the case down the road and I'd like to design something that scales well both with regards to traffic and number of developers (isn't just a nightmare to maintain). So where I am now is planning on using GWT to design the browser-based interface but I'm struggling with how to reuse that code with to present the interface (most likely xml) for the mobile devices. Using GWT RPC would, I think, make it relatively easy to do all of the AJAX in the browser, but might make generating xml for the mobile phones difficult. In addition, I like the idea of using something like Hibernate for persistence and Spring Security to secure the whole thing. Again, I'm not sure how well those will cooperate with GWT (I think Hibernate should be fine...) There's obviously a lot more to this than I've presented here, but I've tried to give you the 5-minute overview. I'm a bit stumped and was wondering if anybody in the community had any experience starting from this place. Does what I'm trying to do make sense? Is it realistic? I have no doubt I can make all of these frameworks speak the same language, I'm just wondering if it's worth my time to fight with them. Also, am I missing a framework that would be really beneficial? Thanks in advance and sorry for the relatively broad question... Chris

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• Armchair Linguists: 'code' vs. 'codes'--or why I write 'code' and my manager asks for 'codes'

  - by Ukko

  I wanted to tap into the collective wisdom here to see if I can get some insight into one of my pet peeves, people who thread "code" as a countable noun. Let me also preface this by saying that I am not talking about anyone who speaks english as a second language, this is a native phenomenon. For those of us who slept through grammar class there are two classes of nouns which basically refer to things that are countable and non-countable (sometimes referred to as count and noncount). For instance 'sand' is a non-count noun and 'apple' is count. You can talk about "two apples" but "two sands" does not parse. The bright students then would point out a word like "beer" where is looks like this is violated. Beer as a substance is certainly a non-count noun, but I can ask for "two beers" without offending the grammar police. The reason is that there are actually two words tied up in that one utterance, Definition #1 is a yummy golden substance and Definition #2 is a colloquial term for a container of said substance. #1 is non-count and #2 is countable. This gets to my problem with "codes" as a countable noun. In my mind the code that we programmers write is non-count, "I wrote some code today." When used in the plural like "Have you got the codes" I can only assume that you are asking if I have the cryptographically significant numbers for launching a missile or the like. Every time my peer in marketing asks about when we will have the new codes ready I have a vision of rooms of code breakers going over the latest Enigma coded message. I corrected the usage in all the documents I am asked to review, but then I noticed that our customer was also using the work "codes" when they meant "code". At this point I have realized that there is a significant sub-population that uses "codes" and they seem to be impervious to what I see as the dominant "correct" usage. This is the part I want some help on, has anyone else noticed this phenomenon? Do you know what group it is associated with, old Fortran programmer perhaps? Is it a regionalism? I have become quick to change my terms when I notice a customer's usage, but it would be nice to know if I am sending a proposal somewhere what style they expect. I would hate to get canned with a review of "Ha, these guy's must be morons they don't even know 'code' is plural!"

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• Shorter Rails routes

  - by Puru puru rin..

  Hello, I have a thing blog application, and I would like to shorten my routes. Here there are: Blog::Application.routes.draw do resources :categories do resources :articles do resources :comments end end A rake routes command build the following lines: GET /categories/:category_id/articles/:article_id/comments(.:format) {:controller=>"comments", :action=>"index"} category_article_comments POST /categories/:category_id/articles/:article_id/comments(.:format) {:controller=>"comments", :action=>"create"} new_category_article_comment GET /categories/:category_id/articles/:article_id/comments/new(.:format) {:controller=>"comments", :action=>"new"} GET /categories/:category_id/articles/:article_id/comments/:id(.:format) {:controller=>"comments", :action=>"show"} PUT /categories/:category_id/articles/:article_id/comments/:id(.:format) {:controller=>"comments", :action=>"update"} category_article_comment DELETE /categories/:category_id/articles/:article_id/comments/:id(.:format) {:controller=>"comments", :action=>"destroy"} edit_category_article_comment GET /categories/:category_id/articles/:article_id/comments/:id/edit(.:format) {:controller=>"comments", :action=>"edit"} GET /categories/:category_id/articles(.:format) {:controller=>"articles", :action=>"index"} category_articles POST /categories/:category_id/articles(.:format) {:controller=>"articles", :action=>"create"} new_category_article GET /categories/:category_id/articles/new(.:format) {:controller=>"articles", :action=>"new"} GET /categories/:category_id/articles/:id(.:format) {:controller=>"articles", :action=>"show"} PUT /categories/:category_id/articles/:id(.:format) {:controller=>"articles", :action=>"update"} category_article DELETE /categories/:category_id/articles/:id(.:format) {:controller=>"articles", :action=>"destroy"} edit_category_article GET /categories/:category_id/articles/:id/edit(.:format) {:controller=>"articles", :action=>"edit"} GET /categories(.:format) {:controller=>"categories", :action=>"index"} categories POST /categories(.:format) {:controller=>"categories", :action=>"create"} new_category GET /categories/new(.:format) {:controller=>"categories", :action=>"new"} GET /categories/:id(.:format) {:controller=>"categories", :action=>"show"} PUT /categories/:id(.:format) {:controller=>"categories", :action=>"update"} category DELETE /categories/:id(.:format) {:controller=>"categories", :action=>"destroy"} edit_category GET /categories/:id/edit(.:format) {:controller=>"categories", :action=>"edit"} As can be seen, each resource is ordered in a tree. So I believe that, it's could be interesting to simplify my routes such as for example: /categories/ => / /categories/:id => /:id /categories/:category_id/articles/ => /:category_id/articles /categories/:category_id/articles/:id => /:category_id/:id /categories/:category_id/articles/:article_id/comments/ => /:category_id/:article_id/comments /categories/:category_id/articles/:article_id/comments/:id => /:category_id/:article_id/:id It's more DRY, is't it? :) Does Rails 3 provides a easy way to do so, with an HTTP verbs mapping to controller actions automatically? Thanks anyone.

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• Oracle Coding Standards Feature Implementation

  - by Mike Hofer

  Okay, I have reached a sort of an impasse. In my open source project, a .NET-based Oracle database browser, I've implemented a bunch of refactoring tools. So far, so good. The one feature I was really hoping to implement was a big "Global Reformat" that would make the code (scripts, functions, procedures, packages, views, etc.) standards compliant. (I've always been saddened by the lack of decent SQL refactoring tools, and wanted to do something about it.) Unfortunatey, I am discovering, much to my chagrin, that there doesn't seem to be any one widely-used or even "generally accepted" standard for PL-SQL. That kind of puts a crimp on my implementation plans. My search has been fairly exhaustive. I've found lots of conflicting documents, threads and articles and the opinions are fairly diverse. (Comma placement, of all things, seems to generate quite a bit of debate.) So I'm faced with a couple of options: Add a feature that lets the user customize the standard and then reformat the code according to that standard. —OR— Add a feature that lets the user customize the standard and simply generate a violations list like StyleCop does, leaving the SQL untouched. In my mind, the first option saves the end-users a lot of work, but runs the risk of modifying SQL in potentially unwanted ways. The second option runs the risk of generating lots of warnings and doing no work whatsoever. (It'd just be generally annoying.) In either scenario, I still have no standard to go by. What I'd need to know from you guys is kind of poll-ish, but kind of not. If you were going to use a tool of this nature, what parts of your SQL code would you want it to warn you about or fix? Again, I'm just at a loss due to a lack of a cohesive standard. And given that there isn't anything out there that's officially published by Oracle, I think this is something the community could weigh in on. Also, given the way that voting works on SO, the votes would help to establish the popularity of a given "refactoring." P.S. The engine parses SQL into an expression tree so it can robustly analyze the SQL and reformat it. There should be quite a bit that we can do to correct the format of the SQL. But I am thinking that for the first release of the thing, layout is the primary concern. Though it is worth noting that the thing already has refactorings for converting keywords to upper case, and identifiers to lower case.

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• hand coding a parser

  - by John Leidegren

  For all you compiler gurus, I wanna write a recursive descent parser and I wanna do it with just code. No generating lexers and parsers from some other grammar and don't tell me to read the dragon book, i'll come around to that eventually. I wanna get into the gritty details about implementing a lexer and parser for a reasonable simple langauge, say CSS. And I wanna do this right. This will probably end up being a series of questions but right now I'm starting with a lexer. Tokenization rules for CSS can be found here. I find my self writing code like this (hopefully you can infer the rest from this snippet): public CssToken ReadNext() { int val; while ((val = _reader.Read()) != -1) { var c = (char)val; switch (_stack.Top) { case ParserState.Init: if (c == ' ') { continue; // ignore } else if (c == '.') { _stack.Transition(ParserState.SubIdent, ParserState.Init); } break; case ParserState.SubIdent: if (c == '-') { _token.Append(c); } _stack.Transition(ParserState.SubNMBegin); break; What is this called? and how far off am I from something reasonable well understood? I'm trying to balence something which is fair in terms of efficiency and easy to work with, using a stack to implement some kind of state machine is working quite well, but I'm unsure how to continue like this. What I have is an input stream, from which I can read 1 character at a time. I don't do any look a head right now, I just read the character then depending on the current state try to do something with that. I'd really like to get into the mind set of writing reusable snippets of code. This Transition method is currently means to do that, it will pop the current state of the stack and then push the arguments in reverse order. That way, when I write Transition(ParserState.SubIdent, ParserState.Init) it will "call" a sub routine SubIdent which will, when complete, return to the Init state. The parser will be implemented in much the same way, currently, having everyhing in a single big method like this allows me to easily return a token when I found one, but it also forces me to keep everything in one single big method. Is there a nice way to split these tokenization rules into seperate methods? Any input/advice on the matter would be greatly appriciated!

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• Am I "wasting" my time learning C and other low level stuff ?

  - by Andreas Grech

  I have just recently started learning C and the reason I did that was because frankly, I consider myself to be of a "less-developer" than the people who know and work with C. Thus I planned to start learning ASM, C, C++ and bought the K&R book and started pushing myself to learn the C Programming Language and up till now I'm doing great...learning about arrays the low level way (ie the pointer + offset thing), pointers and all that and obviously asking questions on stackoverflow for guidance. My problem is that sometimes I get thinking if instead of learning this low level stuff, maybe I should maybe spend more time learning newer, more widely used technologies...basically, more web stuff. Now I am well versed with both C# and ASP.Net and currently that's what I do for a living, but still there exists Microsoft technologies that I haven't quite touched upon...such as ASP.Net MVC, The Entity Framework etc... And those are only Microsoft Technologies...obviously there are other stuff that I would like to touch upon...stuff like Ruby, which would lead me to Ruby on Rails, or Python for Django or even Java and J2EE, or maybe even PHP; ie, basically mainly Web Stuff. Mind you, I did touch upon some of the stuff I mentioned earlier on, such as PHP and Java but I am still not quite versed in them as I am in C# and ASP.Net...but still, I think that by learning other languages that are used in the web environment will broaden my horizons...both as a developer who loves learning, and also Career wise. My point is, am I really using up my time correctly by learning older, lower level stuff? Stuff that for my current line of work, will most probably never use, but still is interesting to know ? To be frankly honest, I am also learning C so that I could, maybe someday, get into Electronics and Micro-controller programming but that is a whole new world for me and, if I choose to go there, will take some time to get adjusted to. And even then, I don't know if I can get a career in working in that line of work. ...but I still wonder about this question over and over...Am I doing the right thing by learning C instead of something (Web-stuff) that will most probably be more useful for me career-wise? I'm sorry for such asking such a long and most probably a boring question, but I feel as if this is the only place where I can ask such a question and get an honest answer from experts in the field. Thank you for your time.

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• Parse int to string with stringstream

  - by SoulBeaver

  Well! I feel really stupid for this question, and I wholly don't mind if I get downvoted for this, but I guess I wouldn't be posting this if I had not at least made an earnest attempt at looking for the solution. I'm currently working on Euler Problem 4, finding the largest palindromic number of two three-digit numbers [100..999]. As you might guess, I'm at the part where I have to work with the integer I made. I looked up a few sites and saw a few standards for converting an Int to a String, one of which included stringstream. So my code looked like this: // tempTotal is my int value I want converted. void toString( int tempTotal, string &str ) { ostringstream ss; // C++ Standard compliant method. ss << tempTotal; str = ss.str(); // Overwrite referenced value of given string. } and the function calling it was: else { toString( tempTotal, store ); cout << loop1 << " x " << loop2 << "= " << store << endl; } So far, so good. I can't really see an error in what I've written, but the output gives me the address to something. It stays constant, so I don't really know what the program is doing there. Secondly, I tried .ToString(), string.valueOf( tempTotal ), (string)tempTotal, or simply store = temptotal. All refused to work. When I simply tried doing an implicit cast with store = tempTotal, it didn't give me a value at all. When I tried checking output it literally printed nothing. I don't know if anything was copied into my string that simply isn't a printable character, or if the compiler just ignored it. I really don't know. So even though I feel this is a really, really lame question, I just have to ask: How do I convert that stupid integer to a string with the stringstream? The other tries are more or less irrelevant for me, I just really want to know why my stringstream solution isn't working.

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• iPhone SDK / Core Data usage scenario, similar to GAE data store?

  - by boliva

  Hi all, I am currently rewriting a map based App which I wrote in the past, specifically for 2.2.1 devices. Originally I wrote it to make use of SQLite databases but I would like to try and migrate it over Core Data, now that it's available on 3.X (for which I am rewriting to). I am fairly experienced in iPhone/Obj-C development, SQL and server backend technologies, but I have never had the chance to work with Core Data so IDK really if it's the appropiate tool for what I am trying to accomplish. The App works on a limited area in a map over which there are about 4000 placemarks, with different kinds of icons and sizes. Of course not all 4000 placemarks are shown at once but only those currently visible in the map viewport, and depending on the zoom level. What I am doing right now is, after the user moves the map in any way (panning or zooming) I am requesting from the backend server the required information for the placemarks that would be visible given the viewport coordinates boundaries and zoom level, however the process isn't as smooth as I'd like (the backend is sending its response in XML and I am compressing it using gzip), it takes anywhere from 1 to 3 seconds to update the display of the placemarks after the user ends moving the map. What I would like to do is to prefetch all the placemarks data at the App launch and use it all through the app life time - I don't mind storing it for later use because the data should be dynamic. The way I would do it right now is, after retrieving all the data, to store it on an SQLite db which I would query later, whenever the user moves the map, to return only the placemarks inside the viewport coordinate boundaries and specific to a given zoom level. Now, the question itself is, if is it possible to use some more 'native', object driven way to carry this queries process, which got me thinking about Core Data and if it is in any way similar to what Google App Engine offers through its datastore where you can fetch a number of objects from the backend given a certain query or criteria, without resorting to an SQL query itself. Like I said before I don't have any experience on Core Data but I have a pretty deep understanding of Obj-C and iPhone development, as well as SQL databases. Any guides on how to achieve what I'm trying (if possible at all) would be greatly appreciated.

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• Eager/Lazy loaded member always empty with JPA one-to-many relationship

  - by Kaleb Pederson

  I have two entities, a User and Role with a one-to-many relationship from user to role. Here's what the tables look like: mysql> select * from User; +----+-------+----------+ | id | name | password | +----+-------+----------+ | 1 | admin | admin | +----+-------+----------+ 1 row in set (0.00 sec) mysql> select * from Role; +----+----------------------+---------------+----------------+ | id | description | name | summary | +----+----------------------+---------------+----------------+ | 1 | administrator's role | administrator | Administration | | 2 | editor's role | editor | Editing | +----+----------------------+---------------+----------------+ 2 rows in set (0.00 sec) And here's the join table that was created: mysql> select * from User_Role; +---------+----------+ | User_id | roles_id | +---------+----------+ | 1 | 1 | | 1 | 2 | +---------+----------+ 2 rows in set (0.00 sec) And here's the subset of orm.xml that defines the tables and relationships: <entity class="User" name="User"> <table name="User" /> <attributes> <id name="id"> <generated-value strategy="AUTO" /> </id> <basic name="name"> <column name="name" length="100" unique="true" nullable="false"/> </basic> <basic name="password"> <column length="255" nullable="false" /> </basic> <one-to-many name="roles" fetch="EAGER" target-entity="Role" /> </attributes> </entity> <entity class="Role" name="Role"> <table name="Role" /> <attributes> <id name="id"> <generated-value strategy="AUTO"/> </id> <basic name="name"> <column name="name" length="40" unique="true" nullable="false"/> </basic> <basic name="summary"> <column name="summary" length="100" nullable="false"/> </basic> <basic name="description"> <column name="description" length="255"/> </basic> </attributes> </entity> Yet, despite that, when I retrieve the admin user, I get back an empty collection. I'm using Hibernate as my JPA provider and it shows the following debug SQL: select user0_.id as id8_, user0_.name as name8_, user0_.password as password8_ from User user0_ where user0_.name=? limit ? When the one-to-many mapping is lazy loaded, that's the only query that's made. This correctly retrieves the one admin user. I changed the relationship to use eager loading and then the following query is made in addition to the above: select roles0_.User_id as User1_1_, roles0_.roles_id as roles2_1_, role1_.id as id9_0_, role1_.description as descript2_9_0_, role1_.name as name9_0_, role1_.summary as summary9_0_ from User_Role roles0_ left outer join Role role1_ on roles0_.roles_id=role1_.id where roles0_.User_id=? Which results in the following results: +----------+-----------+--------+----------------------+---------------+----------------+ | User1_1_ | roles2_1_ | id9_0_ | descript2_9_0_ | name9_0_ | summary9_0_ | +----------+-----------+--------+----------------------+---------------+----------------+ | 1 | 1 | 1 | administrator's role | administrator | Administration | | 1 | 2 | 2 | editor's role | editor | Editing | +----------+-----------+--------+----------------------+---------------+----------------+ 2 rows in set (0.00 sec) Hibernate obviously knows about the roles, yet getRoles() still returns an empty collection. Hibernate also recognized the relationship sufficiently to put the data in the first place. What problems can cause these symptoms?

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• realtime diagnostics

  - by Ion Todirel

  I have an application which has a loop, part of a "Scheduler", which runs at all time and is the heart of the application. Pretty much like a game loop, just that my application is a WPF application and it's not a game. Naturally the application does logging at many points, but the Scheduler does some sensitive monitoring, and sometimes it's impossible just from the logs to tell what may have gotten wrong (and by wrong I don't mean exceptions) or the current status. Because Scheduler's inner loop runs at short intervals, you can't do file I/O-based logging (or using the Event Viewer) in there. First, you need to watch it in real-time, and secondly the log file would grow in size very fast. So I was thinking of ways to show this data to the user in the realtime, some things I considered: Display the data in realtime in the UI Use AllocConsole/WriteConsole to display this information in a console Use a different console application which would display this information, communicate between the Scheduler and the console app using pipes or other IPC techniques Use Windows' Performance Monitor and somehow feed it with this information ETW Displaying in the UI would have its issues. First it doesn't integrate with the UI I had in mind for my application, and I don't want to complicate the UI just for this. This diagnostics would only happen rarely. Secondly, there is going to be some non-trivial data protection, as the Scheduler has it's own thread. A separate console window would work probably, but I'm still worried if it's not too much threshold. Allocating my own console, as this is a windows app, would probably be better than a different console application (3), as I don't need to worry about IPC communication, and non-blocking communication. However a user could close the console I allocated, and it would be problematic in that case. With a separate process you don't have to worry about it. Assuming there is an API for Performance Monitor, it wouldn't be integrated too well with my app or apparent to the users. Using ETW also doesn't solve anything, just a random idea, I still need to display this information somehow. What others think, would there be other ways I missed?

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• Applying Domain Model on top of Linq2Sql entities

  - by Thomas

  I am trying to practice the model first approach and I am putting together a domain model. My requirement is pretty simple: UserSession can have multiple ShoppingCartItems. I should start off by saying that I am going to apply the domain model interfaces to Linq2Sql generated entities (using partial classes). My requirement translates into three database tables (UserSession, Product, ShoppingCartItem where ProductId and UserSessionId are foreign keys in the ShoppingCartItem table). Linq2Sql generates these entities for me. I know I shouldn't even be dealing with the database at this point but I think it is important to mention. The aggregate root is UserSession as a ShoppingCartItem can not exist without a UserSession but I am unclear on the rest. What about Product? It is defiently an entity but should it be associated to ShoppingCartItem? Here are a few suggestion (they might all be incorrect implementations): public interface IUserSession { public Guid Id { get; set; } public IList<IShoppingCartItem> ShoppingCartItems{ get; set; } } public interface IShoppingCartItem { public Guid UserSessionId { get; set; } public int ProductId { get; set; } } Another one would be: public interface IUserSession { public Guid Id { get; set; } public IList<IShoppingCartItem> ShoppingCartItems{ get; set; } } public interface IShoppingCartItem { public Guid UserSessionId { get; set; } public IProduct Product { get; set; } } A third one is: public interface IUserSession { public Guid Id { get; set; } public IList<IShoppingCartItemColletion> ShoppingCartItems{ get; set; } } public interface IShoppingCartItemColletion { public IUserSession UserSession { get; set; } public IProduct Product { get; set; } } public interface IProduct { public int ProductId { get; set; } } I have a feeling my mind is too tightly coupled with database models and tables which is making this hard to grasp. Anyone care to decouple?

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• ObjectDisposedException from core .NET code

  - by John

  I'm having this issue with a live app. (Unfortunately this is post-mortem debugging - I only have this stack trace. I've never seen this personally, nor am I able to reproduce). I get this Exception: message=Cannot access a disposed object. Object name: 'Button'. exceptionMessage=Cannot access a disposed object. Object name: 'Button'. exceptionDetails=System.ObjectDisposedException: Cannot access a disposed object. Object name: 'Button'. at System.Windows.Forms.Control.CreateHandle() at System.Windows.Forms.Control.get_Handle() at System.Windows.Forms.Control.PointToScreen(Point p) at System.Windows.Forms.Button.OnMouseUp(MouseEventArgs mevent) at System.Windows.Forms.Control.WmMouseUp(Message& m, MouseButtons button, Int32 clicks) at System.Windows.Forms.Control.WndProc(Message& m) at System.Windows.Forms.ButtonBase.WndProc(Message& m) at System.Windows.Forms.Button.WndProc(Message& m) at System.Windows.Forms.Control.ControlNativeWindow.OnMessage(Message& m) at System.Windows.Forms.Control.ControlNativeWindow.WndProc(Message& m) at System.Windows.Forms.NativeWindow.Callback(IntPtr hWnd, Int32 msg, IntPtr wparam, IntPtr lparam) exceptionSource=System.Windows.Forms exceptionTargetSite=Void CreateHandle() It looks like a mouse event is arriving at a form after the form has been disposed. Note there is none of my code in this stack trace. The only weird (?) thing I'm doing, is that I do tend to Dispose() Forms quite aggressively when I use them with ShowModal() (see "Aside" below). But I only do this after ShowModal() has returned (that should be safe right)? I think I read that events might be queued up in the event queue, but I can't believe this would be the problem. I mean surely the framework must be tolerant to old messages? I can well imagine that under stress messages might back-log and surely the window might go away at any time? Any ideas? If you could even suggest ways of reproducing, that might be useful. John Aside: TBH I've never quite understood whether calling Dispose() after Form.ShowDialog() is strictly necessary - the MSDN docs for ShowDialog() are to my mind a bit ambiguous.

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• Block element text overflow problem in IE7

  - by Adomas

  I'm making a "sort elements" web game using jQuery, HTML & CSS. While everything works fine in FF, IE8, Opera, Chrome, I'm having problem with IE7 wrapping words inside block elements. Here's how it looks in IE7 (wrong): Link (cannot post images as a new user) In IE8 the box with wrapped text would just expand to fit it whole in one line without any overflows. Sorry, can't give another link as a new user Don't mind the element order as it's random. Elements are dynamically generated by jQuery. HTML code: <div class="ui-sortable" id="area"> <span class="object">: </span> <span class="object">1998- </span> <span class="object">ISSN 1392-4087</span> <span class="object">, </span> <span class="object">. </span> <span class="object">nepriklausomas savaitraštis buhalteriams, finansininkams, auditoriams</span> <span class="object">. </span> <span class="object">. </span> <span class="object">. </span> <span class="object">Vilnius</span> <span class="object">1998- </span> <span class="object"><em>Apskaitos, audito ir mokesciu aktualijos</em></span> </div> CSS code (irrelevant info like fonts & colors removed): #area { min-height: 160px; width: 760px; } .object { display: block; float: left; text-align: center; width: auto; } Any comments on why does IE7 does that? How do I make these spans expand to fit the whole text in one line in IE7 and not wrap the text or make overflows?

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• Looking for a better design: A readonly in-memory cache mechanism

  - by Dylan Lin

  Hi all, I have a Category entity (class), which has zero or one parent Category and many child Categories -- it's a tree structure. The Category data is stored in a RDBMS, so for better performance, I want to load all categories and cache them in memory while launching the applicaiton. Our system can have plugins, and we allow the plugin authors to access the Category Tree, but they should not modify the cached items and the tree(I think a non-readonly design might cause some subtle bugs in this senario), only the system knows when and how to refresh the tree. Here are some demo codes: public interface ITreeNode<T> where T : ITreeNode<T> { // No setter T Parent { get; } IEnumerable<T> ChildNodes { get; } } // This class is generated by O/R Mapping tool (e.g. Entity Framework) public class Category : EntityObject { public string Name { get; set; } } // Because Category is not stateless, so I create a cleaner view class for Category. // And this class is the Node Type of the Category Tree public class CategoryView : ITreeNode<CategoryView> { public string Name { get; private set; } #region ITreeNode Memebers public CategoryView Parent { get; private set; } private List<CategoryView> _childNodes; public IEnumerable<CategoryView> ChildNodes { return _childNodes; } #endregion public static CategoryView CreateFrom(Category category) { // here I can set the CategoryView.Name property } } So far so good. However, I want to make ITreeNode interface reuseable, and for some other types, the tree should not be readonly. We are not able to do this with the above readonly ITreeNode, so I want the ITreeNode to be like this: public interface ITreeNode<T> { // has setter T Parent { get; set; } // use ICollection<T> instead of IEnumerable<T> ICollection<T> ChildNodes { get; } } But if we make the ITreeNode writable, then we cannot make the Category Tree readonly, it's not good. So I think if we can do like this: public interface ITreeNode<T> { T Parent { get; } IEnumerable<T> ChildNodes { get; } } public interface IWritableTreeNode<T> : ITreeNode<T> { new T Parent { get; set; } new ICollection<T> ChildNodes { get; } } Is this good or bad? Are there some better designs? Thanks a lot! :)

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• Oracle Schema Design: Seperate Schema with I/O Overhead?

  - by Guru

  We are designing database schema for a new system based on Oracle 11gR1. We have identified a main schema which would have close to 100 tables, these will be accessed from the front end Java application. We have a requirement to audit the values which got changed in close to 50 tables, this has to be done every row. Which means, it is possible that, for a single row in MYSYS.T1 there might be 50 (or more) rows in MYSYS_AUDIT.T1_AUD table. We might be having old values of every column entry and new values available from T1. DBA gave an observation, advising against this method, because he said, separate schema meant an extra I/O for every operation. Basically AUDIT schema would be used only to do some analyse and enter values (thus SELECT and INSERT). Is it true that, "a separate schema means an extra I/O" ? I could not find justification. It appears logical to me, as the AUDIT data should not be tampered with, so a separate schema. Also, we designed a separate schema for archiving some tables from MYSYS. From MYSYS_ARC the table might be backed up into tapes or deleted after sufficient time. Few stats: Few tables (close to 20, 30) in MYSYS schema could grow to around 50M rows. We have asked for a total disk space of 4 TB. MYSYS_AUDIT schema might be having 10 times that of MYSYS but we wont keep them more than 3 months. Questions Given all these, can you suggest me any improvements? Separate schema affects disc I/O? (one extra I/O for every schema ?) Any general suggestions? Figure: +-------------------+ +-------------------+ | MYSYS | | MYSYS_AUDIT | | | | | | 1. T1 | | 1. T1_AUD | | 2. T2 | | 2. T2_AUD | | 3. T3 |--------->| 3. T3_AUD | | 4. T4 |(SELECT, | 4. T4_AUD | | . | INSERT) | . | | . | | . | | . | | . | | 100. T100 | | 50. T50_AUD | +-------------------+ +-------------------+ | | | | |(INSERT) | | | * +-------------------+ | MYSYS_ARC | | | | 1. T1_ARC | | 2. T2_ARC | | 3. T3_ARC | | 4. T4_ARC | | . | | . | | . | | 100. T100_ARC | +-------------------+ Apart from this, we have two more schemas with only read only rights, but mainly they are for adhoc purpose and we dont mind the performance on them.

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• Swing: Scroll to bottom of JScrollPane, conditionally on current viewport location

  - by I82Much

  Hi all, I am attempting to mimic the functionality of Adium and most other chat clients I've seen, wherein the scrollbars advance to the bottom when new messages come in, but only if you're already there. In other words, if you've scrolled a few lines up and are reading, when a new message comes in it won't jump your position to the bottom of the screen; that would be annoying. But if you're scrolled to the bottom, the program rightly assumes that you want to see the most recent messages at all times, and so auto-scrolls accordingly. I have had a bear of a time trying to mimic this; the platform seems to fight this behavior at all costs. The best I can do is as follows: In constructor: JTextArea chatArea = new JTextArea(); JScrollPane chatAreaScrollPane = new JScrollPane(chatArea); // We will manually handle advancing chat window DefaultCaret caret = (DefaultCaret) chatArea.getCaret(); caret.setUpdatePolicy(DefaultCaret.NEVER_UPDATE); In method that handles new text coming in: boolean atBottom = isViewAtBottom(); // Append the text using styles etc to the chatArea if (atBottom) { scrollViewportToBottom(); } public boolean isAtBottom() { // Is the last line of text the last line of text visible? Adjustable sb = chatAreaScrollPane.getVerticalScrollBar(); int val = sb.getValue(); int lowest = val + sb.getVisibleAmount(); int maxVal = sb.getMaximum(); boolean atBottom = maxVal == lowest; return atBottom; } private void scrollToBottom() { chatArea.setCaretPosition(chatArea.getDocument().getLength()); } Now, this works, but it's janky and not ideal for two reasons. By setting the caret position, whatever selection the user may have in the chat area is erased. I can imagine this would be very irritating if he's attempting to copy/paste. Since the advancement of the scroll pane occurs after the text is inserted, there is a split second where the scrollbar is in the wrong position, and then it visually jumps towards the end. This is not ideal. Before you ask, yes I've read this blog post on Text Area Scrolling, but the default scroll to bottom behavior is not what I want. Other related (but to my mind, not completely helpful in this regard) questions: Setting scroll bar on a jscrollpane Making a JScrollPane automatically scroll all the way down. Any help in this regard would be very much appreciated.

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• Fairness: Where can it be better handled?

  - by Srinivas Nayak

  Hi, I would like to share one of my practical experience with multiprogramming here. Yesterday I had written a multiprogram. Modifications to sharable resources were put under critical sections protected by P(mutex) and V(mutex) and those critical section code were put in a common library. The library will be used by concurrent applications (of my own). I had three applications that will use the common code from library and do their stuff independently. my library --------- work_on_shared_resource { P(mutex) get_shared_resource work_with_it V(mutex) } --------- my application ----------- application1 { *[ work_on_shared_resource do_something_else_non_ctitical ] } application2 { *[ work_on_shared_resource do_something_else_non_ctitical ] } application3 { *[ work_on_shared_resource ] } *[...] denote a loop. ------------ I had to run the applications on Linux OS. I had a thought in my mind, hanging over years, that, OS shall schedule all the processes running under him with all fairness. In other words, it will give all the processes, their pie of resource-usage equally well. When first two applications were put to work, they run perfectly well without deadlock. But when the third application started running, always the third one got the resources, but since it is not doing anything in its non-critical region, it gets the shared resource more often when other tasks are doing something else. So the other two applications were found almost totally halted. When the third application got terminated forcefully, the previous two applications resumed their work as before. I think, this is a case of starvation, first two applications had to starve. Now how can we ensure fairness? Now I started believing that OS scheduler is innocent and blind. It depends upon who won the race; he got the largest pie of CPU and resource. Shall we attempt to ensure fairness of resource users in the critical-section code in library? Or shall we leave it up to the applications to ensure fairness by being liberal, not greedy? To my knowledge, adding code to ensure fairness to the common library shall be an overwhelming task. On the other hand, believing on the applications will also never ensure 100% fairness. The application which does a very little task after working with shared resources shall win the race where as the application which does heavy processing after their work with shared resources shall always starve. What is the best practice in this case? Where we ensure fairness and how? Sincerely, Srinivas Nayak

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• Query Results Not Expected

  - by E-Madd

  I've been a CF developer for 15 years and I've never run into anything this strange or frustrating. I've pulled my hair out for hours, googled, abstracted, simplified, prayed and done it all in reverse. Can you help me? A cffunction takes one string argument and from that string I build an array of "phrases" to run a query with, attempting to match a location name in my database. For example, the string "the republic of boulder" would produce the array: ["the","republic","of","boulder","the republic","the republic of","the republic of boulder","republic of","republic of boulder","of boulder"]. Another cffunction uses the aforementioned cffunction and runs a cfquery. A query based on the previously given example would be... select locationid, locationname, locationaliasname from vwLocationsWithAlias where LocationName in ('the','the republic','the republic of','republic','republic of','republic of boulder','of','of boulder','boulder') or LocationAliasName in ('the','the republic','the republic of','republic','republic of','republic of boulder','of','of boulder','boulder') This returns 2 records... locationid - locationname - locationalias 99 - 'Boulder' - 'the republic' 68 - 'Boulder' - NULL This is good. Works fine and dandy. HOWEVER... if the string is changed to "the republic", resulting in the phrases array ["the","republic","the republic"] which is then used to produce the query... select locationid, locationname, locationaliasname from vwLocationsWithAlias where LocationName in ('the','the republic','republic') or LocationAliasName in ('the','the republic','republic') This returns 0 records. Say what?! OK, just to make sure I'm not involuntarily HIGH I run that very same query in my SQL console against the same database in the cf datasource. 1 RECORD! locationid - locationname - locationalias 99 - 'Boulder' - 'the republic' I can even hard-code that sql within the same cffunction and get that one result, but never from the dynamically generated SQL. I can get my location phrases from another cffunction of a different name that returns hard-coded array values and those work, but never if the array is dynamically built. I've tried removing cfqueryparams, triple-checking my datatypes, datasource setups, etc., etc., etc. NO DICE WTF!? Is this an obscure bug? Am I losing my mind? I've tried everything I can think of and others (including Ray Camden) can think of. ColdFusion 8 (with all the latest hotfixes) SQL Server 2005 (with all the greatest service packs) Windows 2003 Server (with all the latest updates, service packs and nightly MS voodoo)

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• Trying to retrieve the contents of UITableView cell on selection by user.

  - by chubsta

  Hi, this is my first post here and as i am very new (2 weeks in...) to iPhone (or any!) development i am a little unsure as to how much detail is needed or relevant, so please forgive me if I dont provide enough to be useful at this stage... Anyway, on to my problem - I have set up a UITableView-based app, which has a .plist for holding the data. The .plist has a dictionary as its root, followed by a number of Arrays, each containing the data-strings that display in the table. Everything is working fine until the point where i select a row. I have set it up so i get an alert with the results of the button press and it is here that i want to see the contents of the cell being produced. Instead of the expected string eg. "data line 1", all i get is the number of the row within the section. I have gone backwards and forwards but dont seem to be getting anywhere although i am sure it is something simple. The code compiles fine, with no warnings or errors, and if i can just get the string of the selected cell i will be well on my way, so any help appreciated. I know that I need to do more following the 'NSUInteger row = [indexPath row]; part but thats where my mind dries up... here is the relevant 'selection' section, if i need to post more code please let me know, and i really appreciate any help with this...(please forgive my 'alert' message, i was just happy at that point that i get SOMETHING back from the row selection!) (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath { [tableView deselectRowAtIndexPath:indexPath animated:YES]; NSUInteger row = [indexPath row]; NSString *message = [[NSString alloc] initWithFormat: @"You selected Cell %d from this Section, "@"which is a very good choice indeed!" @"Unfortunately I can't work out how to get the info out of the cell so it's not much use at the moment!" @"Still, this is a good chance to see how much space I have in an alert box!", row]; UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"My God! It works..." message:message delegate:nil cancelButtonTitle:@"You are awesome Karl!!" otherButtonTitles:nil]; [alert show]; [message release]; [alert release]; }

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• May volatile be in user defined types to help writing thread-safe code

  - by David Rodríguez - dribeas

  I know, it has been made quite clear in a couple of questions/answers before, that volatile is related to the visible state of the c++ memory model and not to multithreading. On the other hand, this article by Alexandrescu uses the volatile keyword not as a runtime feature but rather as a compile time check to force the compiler into failing to accept code that could be not thread safe. In the article the keyword is used more like a required_thread_safety tag than the actual intended use of volatile. Is this (ab)use of volatile appropriate? What possible gotchas may be hidden in the approach? The first thing that comes to mind is added confusion: volatile is not related to thread safety, but by lack of a better tool I could accept it. Basic simplification of the article: If you declare a variable volatile, only volatile member methods can be called on it, so the compiler will block calling code to other methods. Declaring an std::vector instance as volatile will block all uses of the class. Adding a wrapper in the shape of a locking pointer that performs a const_cast to release the volatile requirement, any access through the locking pointer will be allowed. Stealing from the article: template <typename T> class LockingPtr { public: // Constructors/destructors LockingPtr(volatile T& obj, Mutex& mtx) : pObj_(const_cast<T*>(&obj)), pMtx_(&mtx) { mtx.Lock(); } ~LockingPtr() { pMtx_->Unlock(); } // Pointer behavior T& operator*() { return *pObj_; } T* operator->() { return pObj_; } private: T* pObj_; Mutex* pMtx_; LockingPtr(const LockingPtr&); LockingPtr& operator=(const LockingPtr&); }; class SyncBuf { public: void Thread1() { LockingPtr<BufT> lpBuf(buffer_, mtx_); BufT::iterator i = lpBuf->begin(); for (; i != lpBuf->end(); ++i) { // ... use *i ... } } void Thread2(); private: typedef vector<char> BufT; volatile BufT buffer_; Mutex mtx_; // controls access to buffer_ };

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