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  • Python progression path - From apprentice to guru

    - by Morlock
    Hi all, I've been learning, working, and playing with Python for a year and a half now. As a biologist slowly making the turn to bio-informatics, this language has been a the very core of all the major contributions I have made in the lab. (bash and R scripts have helped some too. My C++ capabilities are very not functional yet). I more or less fell in love with the way Python permits me to express beautiful solutions and also with the semantics of the language that allows such a natural flow from thoughts to workable code. What I would like to know from you is your answer to a kind of question I have seldom seen in this or other forums. Let me sum up what I do NOT want to ask first ;) I don't want to know how to QUICKLY learn Python Nor do I want to find out the best way to get acquainted with the language Finally, I don't want to know a 'one trick that does it all' approach. What I do want to know your opinion about, is: What are the steps YOU would recommend to a Python journeyman, from apprenticeship to guru status (feel free to stop wherever your expertise dictates it), in order that one IMPROVES CONSTANTLY, becoming a better and better Python coder, one step at a time. The kind of answers I would enjoy (but feel free to surprise the readership :P ), is formatted more or less like this: Read this (eg: python tutorial), pay attention to that kind of details Code for so manytime/problems/lines of code Then, read this (eg: this or that book), but this time, pay attention to this Tackle a few real-life problems Then, proceed to reading Y. Be sure to grasp these concepts Code for X time Come back to such and such basics or move further to... (you get the point :) This process depicts an iterative Learn/Code cycle, and I really care about knowing your opinion on what exactly one should pay attention to, at various stages, in order to progress CONSTANTLY (with due efforts, of course). If you come from a specific field of expertise, discuss the path you see as appropriate in this field. Thanks a lot for sharing your opinions and good Python coding!

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  • code review: Is it subjective or objective(quantifiable) ?

    - by Ram
    I am putting together some guidelines for code reviews. We do not have one formal process yet, and trying to formalize it. And our team is geographically distributed We are using TFS for source control (used it for tasks/bug tracking/project management as well, but migrated that to JIRA) with VS2008 for development. What are the things you look for when doing a code review ? These are the things I came up with Enforce FXCop rules (we are a Microsoft shop) Check for performance (any tools ?) and security (thinking about using OWASP- code crawler) and thread safety Adhere to naming conventions The code should cover edge cases and boundaries conditions Should handle exceptions correctly (do not swallow exceptions) Check if the functionality is duplicated elsewhere method body should be small(20-30 lines) , and methods should do one thing and one thing only (no side effects/ avoid temporal coupling -) Do not pass/return nulls in methods Avoid dead code Document public and protected methods/properties/variables What other things do you generally look for ? I am trying to see if we can quantify the review process (it would produce identical output when reviewed by different persons) Example: Saying "the method body should be no longer than 20-30 lines of code" as opposed to saying "the method body should be small" Or is code review very subjective ( and would differ from one reviewer to another ) ? The objective is to have a marking system (say -1 point for each FXCop rule violation,-2 points for not following naming conventions,2 point for refactoring etc) so that developers would be more careful when they check in their code.This way, we can identify developers who are consistently writing good/bad code.The goal is to have the reviewer spend about 30 minutes max, to do a review (I know this is subjective, considering the fact that the changeset/revision might include multiple files/huge changes to the existing architecture etc , but you get the general idea, the reviewer should not spend days reviewing someone's code) What other objective/quantifiable system do you follow to identify good/bad code written by developers? Book reference: Clean Code: A handbook of agile software craftmanship by Robert Martin

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  • Amazon Web services - retrieving a wishlist

    - by izb
    I've been tinkering with Yahoo Pipes and the Amazon E-Commerce Service (ECS) SDK to retrieve my wishlist. The problem is that although I can get all the items on my wishlist just fine, it seems to include items that I've deleted too. Has anyone else used this API and noticed this? Is there a way around it? UPDATE: Requested additional information in comments... Here is the URL I use to fetch the wishlist XML: http://webservices.amazon.co.uk/onca/xml?SubscriptionId=[my subs id]&Service=AWSECommerceService&ResponseGroup=ListItems&ProductPage=1&ProductGroup=Book&Operation=ListLookup&ListType=WishList&ListId=[my list id] And here is the relevant part of the XML response: <ListId>[my list id]</ListId> <ListName>Wishlist</ListName> <TotalItems>132</TotalItems> <TotalPages>14</TotalPages> <ListItem> <ListItemId>EPIE5559HKT391</ListItemId> <DateAdded>2003-11-17</DateAdded> <QuantityDesired>1</QuantityDesired> <QuantityReceived>0</QuantityReceived> <Item> <ASIN>5557205521</ASIN> <ItemAttributes> <Title>Horton hears a who</Title> </ItemAttributes> </Item> </ListItem> ... The rest of the XML is just either more list items like that, or information about the request at the top of the response.

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  • Tab bar controller inside a navigation controller, or sharing a navigation root view

    - by Daniel Dickison
    I'm trying to implement a UI structured like in the Tweetie app, which behaves as so: the top-level view controller seems to be a navigation controller, whose root view is an "Accounts" table view. If you click on any account, it goes to the second level, which has a tab bar across the bottom. Each tab item shows a different list and lets you drill down further (the subsequent levels don't show the tab bar). So, this seems like the implementation hierarchy is: UINavigationController Accounts: UITableViewController UITabBarController Tweets: UITableViewController Detail view of a tweet/user/etc Replies: UITableViewController ... This seems to work[^1], but appears to be unsupported according to the SDK documentation for -pushViewController:animated: (emphasis added): viewController: The view controller that is pushed onto the stack. It cannot be an instance of tab bar controller. I would like to avoid private APIs and the like, but I'm not sure why this usage is explicitly prohibited even when it seems to work fine. Anyone know the reason? I've thought about putting the tab bar controller as the main controller, with each of the tabs containing separate navigation controllers. The problem with this is that each nav controller needs to share a single root view controller (namely the "Accounts" table in Tweetie) -- this doesn't seem to work: pushing the table controller to a second nav controller seems to remove it from the first. Not to mention all the book-keeping when selecting a different account would probably be a pain. How should I implement this the Right Way? [^1]: The tab bar controller needs to be subclassed so that the tab bar controller's navigation item at that level stays in sync with the selected tab's navigation item, and the individual tab's table controller's need to push their respective detail views to self.tabBarController.navigationController instead of self.navigationController.

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  • No flow definition found. Spring web flow

    - by user184794
    Hi, I am new to Spring webflow and now I am trying the example in Spring recipes book and I know this is a basic question. I am getting the error as follows, org.springframework.webflow.definition.registry.NoSuchFlowDefinitionException: No flow definition '${flowExecutionUrl}&_eventId=next' found at org.springframework.webflow.definition.registry.FlowDefinitionRegistryImpl.getFlowDefinitionHolder(FlowDefinitionRegistryImpl.java:126) at org.springframework.webflow.definition.registry.FlowDefinitionRegistryImpl.getFlowDefinition(FlowDefinitionRegistryImpl.java:61) at org.springframework.webflow.executor.FlowExecutorImpl.launchExecution(FlowExecutorImpl.java:138) at org.springframework.webflow.mvc.servlet.FlowHandlerAdapter.handle(FlowHandlerAdapter.java:193).... Shown below is my configurations, <bean name="flowController" class="org.springframework.webflow.mvc.servlet.FlowController"> <property name="flowExecutor" ref="flowExecutor"></property> </bean> <webflow:flow-executor id="flowExecutor" /> <webflow:flow-registry id="flowRegistry" > <webflow:flow-location path="/WEB-INF/flows/welcome/welcome.xml"></webflow:flow-location> </webflow:flow-registry> /WEB-INF/flows/welcome/welcome.xml, <view-state id="welcome"> <transition on="next" to="introduction" /> <transition on="skip" to="menu" /> </view-state> <view-state id="introduction"> <on-render> <evaluate expression="libraryService.getHolidays()" result="requestScope.holidays" /> </on-render> <transition on="next" to="menu" /> </view-state> <view-state id="menu"></view-state> In welcome.jsp, <a href="${flowExecutionUrl}&_eventId=next">Next</a> <a href="${flowExecutionUrl}&_eventId=skip">Skip</a> Please let me know what is going wrong. I am using 2.0.9 Release. Thanks in advance, SD

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  • How does the recursion here work?

    - by David
    code 1: public static int fibonacci (int n){ if (n == 0 || n == 1) { return 1; } else { return fibonacci (n-1) + fibonacci (n-2); } } how can you use fibonacci if you haven't gotten done explaining what it is yet? I've been able to understand using recursion in other cases like this: code two: class two { public static void two (int n) { if (n>0) { System.out.println (n) ; two (n-1) ; } else { return ; } } public static void main (String[] arg) { two (12) ; } } In the case of code 2 though n will eventualy reach a point at which it doesnt satisfy n0 and the method will stop calling itself recursivly. in the case of code 2 though i don't see how it would be able to get itself from 1 if n=1 was the starting point to 2 and 3 and 5 and so on. Also i don't see how the line `return fibonacci (n-1) + fibonacci (n-2) would work since fibbonacci n-2 has to contain in some sense fibonacci n-1 in order to wrok but it isn't there yet. I know my question is worded poorly but looking at this is making my mind explode. the book i'm looking at says it will work. how does it work? `

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  • seam page parameters not working as expected.

    - by rangalo
    Hi, I am learning seam and following a very famous book Seam In Action by Dan Allen. This is an example from this book. Seam 2.2.0.GA JBoss 5.1.0.GA Here the page parameter roundId is always null even after a round is serialized, it is never passed. Neither to Roud.xhtml nor to RoundEdit.xhtml after clicking save on RoundEdit.xhtml. The entity always stays unmanaged. RoundEdit.page.xml <?xml version="1.0" encoding="UTF-8"?> <page xmlns="http://jboss.com/products/seam/pages" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://jboss.com/products/seam/pages http://jboss.com/products/seam/pages-2.2.xsd" login-required="true"> <begin-conversation join="true" /> <param name="roundId" value="#{roundHome.id}" converterId="javax.faces.Long"/> <param name="teeSetId" value="#{teeSetHome.teeSetId}" /> <param name="roundFrom" /> <action execute="#{roundHome.wire}" /> <navigation from-action="#{roundHome.persist}"> <rule if-outcome="persisted"> <end-conversation/> <redirect view-id="#{null != roundFrom ? roundFrom : '/Round.xhtml'}" /> </rule> </navigation> </page> RoundEdit.xhtml <?xml version="1.0" encoding="UTF-8"?> <!DOCTYPE composition PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <ui:composition xmlns="http://www.w3.org/1999/xhtml" xmlns:s="http://jboss.com/products/seam/taglib" xmlns:ui="http://java.sun.com/jsf/facelets" xmlns:f="http://java.sun.com/jsf/core" xmlns:h="http://java.sun.com/jsf/html" xmlns:a="http://richfaces.org/a4j" xmlns:rich="http://richfaces.org/rich" template="layout/template.xhtml"> <ui:define name="body"> <h:form id="roundform"> <rich:panel> <f:facet name="header>"> #{roundHome.managed ? 'Edit' : 'Add' } Round </f:facet> <s:decorate id="dateField" template="layout/edit.xhtml"> <ui:define name="label">Date:</ui:define> <rich:calendar id="date" datePattern="dd/MM/yyyy" value="#{round.date}"/> </s:decorate> <s:decorate id="notesField" template="layout/edit.xhtml"> <ui:define name="label">Notes:</ui:define> <h:inputTextarea id="notes" cols="80" rows="3" value="#{round.notes}" /> </s:decorate> <s:decorate id="totalScoreField" template="layout/edit.xhtml"> <ui:define name="label">Total Score:</ui:define> <h:inputText id="totalScore" value="#{round.totalScore}" /> </s:decorate> <s:decorate id="weatherField" template="layout/edit.xhtml"> <ui:define name="label">Weather:</ui:define> <h:selectOneMenu id="weather" value="#{round.weather}"> <s:selectItems var="_weather" value="#{weatherCategories}" label="#{_weather.label}" noSelectionLabel=" Select " /> <s:convertEnum/> </h:selectOneMenu> </s:decorate> <h:messages/> <div style="clear: both;"> <span class="required">*</span> required fields </div> </rich:panel> <div class="actionButtons"> <h:commandButton id="save" value="Save" action="#{roundHome.persist}" rendered="#{!roundHome.managed}" disabled="#{!roundHome.wired}" /> <h:commandButton id="update" value="Update" action="#{roundHome.update}" rendered="#{roundHome.managed}" /> <h:commandButton id="delete" value="Delete" action="#{roundHome.remove}" rendered="#{roundHome.managed}" /> <s:button id="discard" value="Discard changes" propagation="end" view="/Round.xhtml" rendered="#{roundHome.managed}" /> <s:button id="cancel" value="Cancel" propagation="end" view="/#{empty roundFrom ? 'RoundList' : roundFrom}.xhtml" rendered="#{!roundHome.managed}" /> </div> <rich:tabPanel> <rich:tab label="Tee Set"> <div class="association"> <h:outputText value="Tee set not selected" rendered="#{round.teeSet == null}" /> <rich:dataTable var="_teeSet" value="#{round.teeSet}" rendered="#{round.teeSet != null}"> <h:column> <f:facet name="header">Course</f:facet>#{_teeSet.course.name} </h:column> <h:column> <f:facet name="header">Color</f:facet>#{_teeSet.color} </h:column> <h:column> <f:facet name="header">Position</f:facet>#{_teeSet.pos} </h:column> </rich:dataTable> </div> </rich:tab> </rich:tabPanel> </h:form> </ui:define> </ui:composition> Round.page.xml <?xml version="1.0" encoding="UTF-8"?> <page xmlns="http://jboss.com/products/seam/pages" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://jboss.com/products/seam/pages http://jboss.com/products/seam/pages-2.2.xsd"> <param name="roundId" value="#{roundHome.id}" converterId="javax.faces.Long"/> </page> Round.xhtml <?xml version="1.0" encoding="UTF-8"?> <!DOCTYPE composition PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <ui:composition xmlns="http://www.w3.org/1999/xhtml" xmlns:s="http://jboss.com/products/seam/taglib" xmlns:ui="http://java.sun.com/jsf/facelets" xmlns:f="http://java.sun.com/jsf/core" xmlns:h="http://java.sun.com/jsf/html" xmlns:a="http://richfaces.org/a4j" xmlns:rich="http://richfaces.org/rich" template="layout/template.xhtml"> <ui:define name="body"> <h:form id="roundform"> <rich:panel> <f:facet name="header>">Round</f:facet> <s:decorate id="id" template="layout/display.xhtml"> <ui:define name="label">Id:</ui:define> <h:outputText value="#{null == roundHome.id ? 'null' : roundHome.id}"> <s:convertDateTime type="date" /> </h:outputText> </s:decorate> <s:decorate id="date" template="layout/display.xhtml"> <ui:define name="label">Date:</ui:define> <h:outputText value="#{roundHome.instance.date}"> <s:convertDateTime type="date" /> </h:outputText> </s:decorate> <s:decorate id="golfer" template="layout/display.xhtml"> <ui:define name="label">Golfer:</ui:define> #{roundHome.instance.golfer.name} </s:decorate> <s:decorate id="totalScore" template="layout/display.xhtml"> <ui:define name="label">Total Score:</ui:define> #{roundHome.instance.totalScore} </s:decorate> <s:decorate id="weather" template="layout/display.xhtml"> <ui:define name="label">Weather:</ui:define> #{roundHome.instance.weather} </s:decorate> <s:decorate id="notes" template="layout/display.xhtml"> <ui:define name="label">Notes:</ui:define> #{roundHome.instance.notes} </s:decorate> <div style="clear:both"/> </rich:panel> <div class="actionButtons"> <s:button id="edit" view="/RoundEdit.xhtml" value="Edit" /> </div> <rich:tabPanel> <rich:tab label="Tee Set"> <div class="association"> <h:outputText value="Tee set not selected" rendered="#{roundHome.instance.teeSet == null}" /> <rich:dataTable var="_teeSet" value="#{roundHome.instance.teeSet}" rendered="#{roundHome.instance.teeSet != null}"> <h:column> <f:facet name="header">Course</f:facet>#{_teeSet.course.name} </h:column> <h:column> <f:facet name="header">Color</f:facet>#{_teeSet.color} </h:column> <h:column> <f:facet name="header">Position</f:facet>#{_teeSet.pos} </h:column> </rich:dataTable> </div> </rich:tab> </rich:tabPanel> </h:form> </ui:define> </ui:composition> The entityHome RoundHome.java @Name("roundHome") public class RoundHome extends EntityHome<Round>{ @In(required = false) private Golfer currentGolfer; @In(create = true) private TeeSetHome teeSetHome; @Logger private Log logger; public void wire() { logger.info("wire called"); TeeSet teeSet = teeSetHome.getDefinedInstance(); if (null != teeSet) { getInstance().setTeeSet(teeSet); logger.info("Successfully wired the teeSet instance with color: " + teeSet.getColor()); } } public boolean isWired() { logger.info("is wired called"); if(null == getInstance().getTeeSet()) { logger.info("wired teeSet instance is null, the button will be disabled !"); return false; } else { logger.info("wired teeSet instance is NOT null, the button will be enabled !"); logger.info("teeSet color: "+getInstance().getTeeSet().getColor()); return true; } } @RequestParameter public void setRoundId(Long id) { logger.info("in Setter RoundId is: " + id); super.setId(id); } public Long getRoundId() { Long id = (Long) getId(); logger.info("Setting RoundId : " + id); return id; } @Override protected Round createInstance() { Round round = super.createInstance(); round.setGolfer(currentGolfer); round.setDate(new java.sql.Date(System.currentTimeMillis())); logger.info("Created a Round with roundId: " + round.getId()); return round; } @Override protected Round loadInstance() { logger.info("loadInstance for id: " + getId()); return (Round) getEntityManager().createQuery( "select r from Round r " + "join fetch r.golfer g " + "join fetch r.teeSet ts " + "join fetch ts.course c " + "where r.id = :id ") .setParameter("id",getId()) .getSingleResult(); } }

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  • Remove file from git repository (history)

    - by Devenv
    (solved, see bottom of the question body) Looking for this for a long time now, what I have till now is: http://dound.com/2009/04/git-forever-remove-files-or-folders-from-history/ and http://progit.org/book/ch9-7.html Pretty much the same method, but both of them leave objects in pack files... Stuck. What I tried: git filter-branch --index-filter 'git rm --cached --ignore-unmatch file_name' rm -Rf .git/refs/original rm -Rf .git/logs/ git gc Still have files in the pack, and this is how I know it: git verify-pack -v .git/objects/pack/pack-3f8c0...bb.idx | sort -k 3 -n | tail -3 And this: git filter-branch --index-filter "git rm -rf --cached --ignore-unmatch file_name" HEAD rm -rf .git/refs/original/ && git reflog expire --all && git gc --aggressive --prune The same... Tried git clone trick, it removed some of the files (~3000 of them) but the largest files are still there... I have some large legacy files in the repository, ~200M, and I really don't want them there... And I don't want to reset the repository to 0 :( SOLUTION: This is the shortest way to get rid of the files: check .git/packed-refs - my problem was that I had there a refs/remotes/origin/master line for a remote repository, delete it, otherwise git won't remove those files (optional) git verify-pack -v .git/objects/pack/#{pack-name}.idx | sort -k 3 -n | tail -5 - to check for the largest files (optional) git rev-list --objects --all | grep a0d770a97ff0fac0be1d777b32cc67fe69eb9a98 - to check what files those are git filter-branch --index-filter 'git rm --cached --ignore-unmatch file_names' - to remove the file from all revisions rm -rf .git/refs/original/ - to remove git's backup git reflog expire --all --expire='0 days' - to expire all the loose objects (optional) git fsck --full --unreachable - to check if there are any loose objects git repack -A -d - repacking the pack git prune - to finally remove those objects

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  • Roadmap to Android development

    - by Matthew
    Hello, I've done a little research, and am interested in developing for Android. I've never programmed before, and have no idea how to go from zero experience to developing for a mobile device. My interest is in eventually making some sort of 2d game. Is there a lesson plan for starting from the ground up? I would think one would need to learn the Java language to start. Looking at the Sun website, it's a bit daunting. Is there a book, specifically, that would wrap up this knowledge in a bit of a directed lesson plan? I'm not sure if opengl-es is what would be required for 2d games. I've done a little research on this, and it's even far more daunting than Java itself. I can't even begin to figure out where to start with even just opengl, sans -es. My best guess would be that I need further knowledge in Java to continue with this, but even still, is it possible to learn concurrently with Java?

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  • Useful training courses that aren't specific to a single technology

    - by Dave Turvey
    I have possibly the best problem in the world. I have about £1600 left in a training budget and I need to find something to spend it on. I can spend it on anything that could be considered training. Books, courses, conferences, etc. I would like to find a course that would benifit a software developer but is not about learning a specific programming technology. I don't really want to spend it on a technical training course. These topics are usually best learned with a good book and some trial and error. I have also already been on a general business/management training course and a PRINCE2 project management course. I am currently working on a project on my own so am responsible for communicating with the client, requirements gathering, project management, etc., as well as the coding. What training have you found useful outside the usual technical stuff? Has anyone done any business analysis courses? What were they like? Are there any courses on some of the practicalities of working with software, e.g. automated test and deployment strategies, handling technical support? I would prefer a course in the UK but I can travel if necessary.

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  • Nested instances in C#

    - by user32848
    I'm trying to translate some C++ code for a neural net into C#. I first took the C++ code, from a 1993 book, and ran it. Then translated it using the STL and it ran again. Now I'm trying to get it into C# with Visual Web Developer 2008 Express. The original code used "friend" classes and I'm just trying to do the same making everything "public". The following code compiles but only gives null references when run: public class ineuron { public Double weight, activation; public ineuron(Double set_wt) { weight = set_wt; } ... public class netwrk { public oneuron onrn; public ineuron in1, in2, in3, in4; public netwrk( Double inp_1, Double inp_2, Double inp_3, Double inp_4 ) { ineuron in1 = new ineuron(inp_1); ineuron in2 = new ineuron(inp_2); ... and later, in some code called by a button push: netwrk ntw = new netwrk(i_n1, i_n2, i_n3, i_n4); Unfortunately, trying to use: ntw.in1.activation etc. leads to null reference runtime errors. What am I forgetting to do? Barney

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  • MSMQ first Message.Body in queue is OK, all following Message.Body in queue are empty

    - by Andrew A
    I send a handful of identical (except for Id#, obviously) messages to an MSMQ queue on my local machine. The body of the messages is a serialized XElement object. When I try to process the first message in the queue, I am able to successfully de-serialize the Message.Body object and save it to file. However, when trying to process the next (or any subsequent) message, the Message.Body is absent, and an exception is thrown. I have verified the Message ID's are correct for the message attempting to be processed. The XML being serialized is properly formed. Any ideas? I am basing my code on the Microsoft MSMQ Book order sample found here: http://msdn.microsoft.com/en-us/library/ms180970%28VS.80%29.aspx // Create Envelope XML object XElement envelope = new XElement(env + "Envelope", new XAttribute(XNamespace.Xmlns + "env", env.NamespaceName) <snip> //Send envelope as message body MessageQueue myQueue = new MessageQueue(String.Format(@"FORMATNAME:DIRECT=OS:localhost\private$\mqsample")); myQueue.DefaultPropertiesToSend.Recoverable = true; // Prepare message Message myMessage = new Message(); myMessage.ResponseQueue = new MessageQueue(String.Format(System.Globalization.CultureInfo.InvariantCulture, @"FORMATNAME:DIRECT=TCP:192.168.1.217\private$\mqdemoAck")); myMessage.Body = envelope; // Send the message into the queue. myQueue.Send(myMessage,"message label"); //Retrieve messages from queue LabelIdMapping labelID = (LabelIdMapping)mqlistBox3.SelectedItem; System.Messaging.Message message = mqOrderQueue.ReceiveById(labelID.Id); The Message.Body value I see on the 1st retrieve is as expected: <?xml version="1.0" encoding="utf-8"?> <string>Some String</string> However, the 2nd and subsequent retrieve operations Message.Body is: "Cannot deserialize the message passed as an argument. Cannot recognize the serialization format." How does this work fine the first time but not after that? I have tried message.Dispose() after retrieving it but it did not help. Thank you very much for any help on this!

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  • Static factory pattern with EJB3/JBoss

    - by purecharger
    I'm fairly new to EJBs and full blown application servers like JBoss, having written and worked with special purpose standalone Java applications for most of my career, with limited use of JEE. I'm wondering about the best way to adapt a commonly used design pattern to EJB3 and JBoss: the static factory pattern. In fact this is Item #1 in Joshua Bloch's Effective Java book (2nd edition) I'm currently working with the following factory: public class CredentialsProcessorFactory { private static final Log log = LogFactory.getLog(CredentialsProcessorFactory.class); private static Map<CredentialsType, CredentialsProcessor> PROCESSORS = new HashMap<CredentialsType, CredentialsProcessor>(); static { PROCESSORS.put(CredentialsType.CSV, new CSVCredentialsProcessor()); } private CredentialsProcessorFactory() {} public static CredentialsProcessor getProcessor(CredentialsType type) { CredentialsProcessor p = PROCESSORS.get(type); if(p == null) throw new IllegalArgumentException("No CredentialsProcessor registered for type " + type.toString()); return p; } However, in the implementation classes of CredentialsProcessor, I require injected resources such as a PersistenceContext, so I have made the CredentialsProcessor interface a @Local interface, and each of the impl's marked with @Stateless. Now I can look them up in JNDI and use the injected resources. But now I have a disconnect because I am not using the factory anymore. My first thought was to change the getProcessor(CredentialsType) method to do a JNDI lookup and return the SLSB instance that is required, but then I need to configure and pass the proper qualified JNDI name. Before I go down that path, I wanted to do more research on accepted practices. How is this design pattern treated in EJB3 / JEE?

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  • Debugging a working program on Mathematica 5 with Mathematica 7

    - by Neuschwanstein
    Hi everybody, I'm currently reading the Mathematica Guidebooks for Programming and I was trying to work out one of the very first program of the book. Basically, when I run the following program: Plot3D[{Re[Exp[1/(x + I y)]]}, {x, -0.02, 0.022}, {y, -0.04, 0.042}, PlotRange -> {-1, 8}, PlotPoints -> 120, Mesh -> False, ColorFunction -> Function[{x1, x2, x3}, Hue[Arg[Exp[1/(x1 + I x2)]]]]] either I get a 1/0 error and e^\infinity error or, if I lower the PlotPoints options to, say, 60, an overflow error. I have a working output though, but it's not what it's supposed to be. The hue seems to be diffusing off the left corner whereas it should be diffusing of the origin (as can be seen on the original output) Here is the original program which apparently runs on Mathematica 5 (Trott, Mathematica Guidebook for Programming): Off[Plot3D::gval]; Plot3D[{Re[Exp[1/(x + I y)]], Hue[Arg[Exp[1/(x + I y)]]]}, {x, -0.02, 0.022}, {y, -0.04, 0.042}, PlotRange -> {-1, 8}, PlotPoints -> 120, Mesh -> False] Off[Plot3D::gval]; However, ColorFunction used this way (first Plot3D argument) doesn't work and so I tried to simply adapt to its new way of using it. Well, thanks I guess!

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  • Good DB Migrations for CakePHP?

    - by Martin Westin
    Hi, I have been trying a few migration scripts for CakePHP but I ran into problems with all of the in some form or another. Please advice me on a migration option for Cake that you use live and know works. I'd like the following "features": -Support CakePHP 1.2(e.g. CakeDCs migrations will only be an option when 1.3 is stable and my app migrated to the new codebase) -Support for (or at least not halt on) Models with a different database config. -Support Models in sub-folders of app/models -Support Models in plugins -Support tables that do not conform to Cake conventions (I have a few special tables that do not have a single primary key field and need to keep them) -Plays well with automated deployment via Capistrano and Git. I do not need rails-style versioned files a git versioned schema file that is compared live to the existing schema will do. That is: I like the SchemaShell in Cake apart from it not being compatible with most of my requirements above. I have looked at and tested: CakePHP Schema Shell http://book.cakephp.org/view/734/Schema-management-and-migrations CakeDC migrations http://cakedc.com/downloads/view/cakephp_migrations_plugin YAML migrations http://github.com/georgious/cakephp-yaml-migrations-and-fixtures joelmoss migrations http://code.google.com/p/cakephp-migrations

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  • Publishing toolchain

    - by Marcelo de Moraes Serpa
    Hello all, I have a book project which I'd like to start sooner than later. This would follow an agile-like publishing workflow, i.e: publish early and often. It is meant to be self-publsihed by me and I'm not really looking to paper-publish it, even though we never know. If I weren't a geek, I'd probably have already started writting in Word or any other WYSIWYG tool and just export to PDF. However, we know it is not the best solution, and emacs rules my text-editing life, so, the output format should be as simple as possible and be text-based. I've thought about the following options: 1) Use orgmode and export to PDF; 2) Use markdown mode and export to PDF; 3) Use something similar to what the guys @ Pragmatic Progammers do: A XML + XSLT + LaTeX. More complex, but much more control over the style. Any other ideas / references ? I want to start writting as soon as possible. In fact, I already have a draft in an org-formatted file. However, I do want to have and use the full power of LaTex later on to format it the way I want and make it look fabulous :) Thanks in advance, Marcelo.

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  • Open Source Web Frameworks : Security

    - by trappedIntoCode
    How secure are popular open source web frameworks? I am particularly interested in popular frameworks like Rails and DJango. If I am building a site which is going to do heavy e-commerce, is it Ok to use frameworks like DJango and Satchmo? Is security compromised because their open architecture ? I know being OS does not mean being down right open to hackers, Linux uses superb authentication mechanism, but web is a different game. What can be done in this regard? UPDATE: Thanks for answers guys. I understand that I will have to find a suitable hosting service for a secure e-commerce application and that additional layers of security will be needed. I understand that Django and Rails have been designed keeping security aspects in mind, the most common form attacks like XSS, Injections etc. (Django book has a ch on Security) I was expecting comments from security Gurus. If you are a security Guru, would you recommend an important site, which is likely going to be popular, to be built on DJango or Rails?

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  • Invoice & Invoice lines: How do you store customer address information?

    - by elviejo
    Hi I'm developing an invoicing application. So the general idea is to have two tables: Invoice (ID, Date, CustomerAddress, CustomerState, CustomerCountry, VAT, Total); InvoiceLine (Invoice_ID, ID, Concept, Units, PricePerUnit, Total); As you can see this basic design leads to a lot of repetiton of records where the client will have the same addrres, state and country. So the alternative is to have an address table and then make a relationship Address<-Invoice. However I think that an invoice is immutable document and should be stored just the way it was first made. Sometimes customers change their addresses, or states and if it was coming from an Address catalog that will change all the previously made invoices. So What is your experience? How is the customer address stored in an invoice? In the Invoice table? an Address Table? or something else? Can you provide pointers to a book, article or document where this is discussed in further detail?

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  • UI design in flash games

    - by anon
    This question is more UI/Design-ish than hard-core programming is. Background: I've been coding in VIM/C++/OpenGL for a long time. I've come to realize that this (VIM/C++/OpenGL) isn't the way to learn about programming fancy/cool-looking/futuristic UIs; and that the design of such UIs belongs more so in the artistic/designer world of Flash. Anyway, I currently have a machine with MacOSX. What software should I install? What book should I read to learn about the artistic/design side of these futuristic UIs? [It's okay if the tools to design them are mouse clicking + graphical rather than coding based]. Question: what software packages + books to read to learn about creating fancy-looking / futuristic UIs in flash? Thanks! EDIT: PS these questions seem to get closed frequently. If you're going to vote to close for "duplicate question"; atleast provide a link to the question (with an answer).

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  • Custom Event - invokation list implementation considerations

    - by M.A. Hanin
    I'm looking for some pointers on implementing Custom Events in VB.NET (Visual Studio 2008, .NET 3.5). I know that "regular" (non-custom) Events are actually Delegates, so I was thinking of using Delegates when implementing a Custom Event. On the other hand, Andrew Troelsen's "Pro VB 2008 and the .NET 3.5 Platform" book uses Collection types in all his Custom Events examples, and Microsoft's sample codes match that line of thought. So my question is: what considerations should I have when choosing one design over the other? What are the pros and cons for each design? Which of these resembles the inner-implementation of "regular" events? Below is a sample code demonstrating the two designs. Public Class SomeClass Private _SomeEventListeners As EventHandler Public Custom Event SomeEvent As EventHandler AddHandler(ByVal value As EventHandler) _SomeEventListeners = [Delegate].Combine(_SomeEventListeners, value) End AddHandler RemoveHandler(ByVal value As EventHandler) _SomeEventListeners = [Delegate].Remove(_SomeEventListeners, value) End RemoveHandler RaiseEvent(ByVal sender As Object, ByVal e As System.EventArgs) _SomeEventListeners.Invoke(sender, e) End RaiseEvent End Event Private _OtherEventListeners As New List(Of EventHandler) Public Custom Event OtherEvent As EventHandler AddHandler(ByVal value As EventHandler) _OtherEventListeners.Add(value) End AddHandler RemoveHandler(ByVal value As EventHandler) _OtherEventListeners.Remove(value) End RemoveHandler RaiseEvent(ByVal sender As Object, ByVal e As System.EventArgs) For Each handler In _OtherEventListeners handler(sender, e) Next End RaiseEvent End Event End Class

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  • Books and resources for Java Performance tuning - when working with databases, huge lists

    - by Arvind
    Hi All, I am relatively new to working on huge applications in Java. I am working on a Java web service which is pretty heavily used by various clients. The service basically queries the database (hibernate) and then works with a lot of Lists (there are adapters to convert list returned from DB to the interface which the service publishes) and I am seeing lot of issues with the service like high CPU usage or high heap space. While I can troubleshoot the performance issues using a profiler, I want to actually learn about what all I need to take care when I actually write code. Like what kind of List to use or things like using StringBuilder instead of String, etc... Is there any book or blogs which I can refer which will help me while I write new services? Also my application is multithreaded - each service call from a client is a new thread, and I want to know some best practices around that area as well. I did search the web but I found many tips which are not relevant in the latest Java 6 releases, so wanted to know what kind of resources would help a developer starting out now on Java for heavily used applications. Arvind

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  • Implementing Naïve Bayes algorithm in Java - Need some guidance

    - by techventure
    hello stackflow people As a School assignment i'm required to implement Naïve Bayes algorithm which i am intending to do in Java. In trying to understand how its done, i've read the book "Data Mining - Practical Machine Learning Tools and Techniques" which has a section on this topic but am still unsure on some primary points that are blocking my progress. Since i'm seeking guidance not solution in here, i'll tell you guys what i thinking in my head, what i think is the correct approach and in return ask for correction/guidance which will very much be appreciated. please note that i am an absolute beginner on Naïve Bayes algorithm, Data mining and in general programming so you might see stupid comments/calculations below: The training data set i'm given has 4 attributes/features that are numeric and normalized(in range[0 1]) using Weka (no missing values)and one nominal class(yes/no) 1) The data coming from a csv file is numeric HENCE * Given the attributes are numeric i use PDF (probability density function) formula. + To calculate the PDF in java i first separate the attributes based on whether they're in class yes or class no and hold them into different array (array class yes and array class no) + Then calculate the mean(sum of the values in row / number of values in that row) and standard divination for each of the 4 attributes (columns) of each class + Now to find PDF of a given value(n) i do (n-mean)^2/(2*SD^2), + Then to find P( yes | E) and P( no | E) i multiply the PDF value of all 4 given attributes and compare which is larger, which indicates the class it belongs to In temrs of Java, i'm using ArrayList of ArrayList and Double to store the attribute values. lastly i'm unsure how to to get new data? Should i ask for input file (like csv) or command prompt and ask for 4 values? I'll stop here for now (do have more questions) but I'm worried this won't get any responses given how long its got. I will really appreciate for those that give their time reading my problems and comment.

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  • jQuery fn.extend ({bla: function(){}} vs. jQuery.fn.bla

    - by tixrus
    OK I think I get http://stackoverflow.com/questions/1991126/difference-jquery-extend-and-jquery-fn-extend in that the general extend can extend any object, and that fn.extend is for plugin functions that can be invoked straight off the jquery object with some internal jquery voodoo. So it appears one would invoke them differently. If you use general extend to extend object obj by adding function y, then the method would attach to that object, obj.y() but if you use fn.extend then they are attach straight to the jquery object $.y().... Have I got that correct yes or no and if no what do I have wrong in my understanding? Now MY question: The book I am reading advocates using jQuery.fn.extend ({a: function(){}, b: function(){}}); syntax but in the docs it says jQuery.fn.a (function(){}); and I guess if you wanted b as well it would be jQuery.fn.b (function(){}); Are these functionally and performance-wise equivalent and if not what is the difference? Thank you very much. I am digging jQuery!

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  • Beginner question - Loop invariants (Specifically Ch.3 of "Accelerated C++")

    - by Owen
    Hi - as I said, a complete beginner question here. I'm currently working my way through "Accelerated C++" and just came across this in chapter 3: // invariant: // we have read count grades so far, and // sum is the sum of the first count grades while (cin >> x) { ++count; sum += x; } The authors follow this by explaining that the invariant needs special attention paid to it because when the input is read into the variable x, we will have read count+1 grades and thus the invariant will be untrue. Similarly, when we have incremented the counter, the variable sum will no longer be the sum of the last count grades (in case you hadn't guessed, it's the traditional program for calculating student marks). What I don't understand is why this matters. Surely for just about any other loop, a similar statement would be true? For example, here is the book's first while loop (the output is filled in later): // invariant: we have written r rows so far while (r != rows) { // write a row of output std::cout << std::endl; ++r; } Once we have written the appropriate row of output, surely the invariant is false until we have incremented r, just as in the other example? It's probably something really obvious, anyone could enlighten me as to what makes these two cases different, that'd be great - and thanks in advance for taking the time to answer such a complete novice question. Owen

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  • What is the most important thing you weren't taught in school?

    - by Alexandre Brisebois
    What is the most important thing you weren't taught in school? What topics are missing from the CS/IS education? Posted so far How to sell an idea Principles: Often, good enough is better than perfect. Making mistakes is actually a Good Thing™ -- as long as they're new mistakes. If a user can break your code they will. In the Real World™ they're all open-book exams Self confidence is way more important in getting ahead than intelligence. Always prefer simplicity over complexity. The best code is the code that you don't write. You never know when you'll meet someone again ... or where. It's always worthwhile to treat people with respect and kindness. Be aware of what you don't know and don't be afraid to ask questions when you need to Missing knowledge: How to communicate effectively. Lack of source control Lack of Softskills experience How to productize code How to write secure code How to formulate problems How to self-measurement. To evaluate ones true competences and market worth. How to debug code How important is backup How to read code on a large scale (being able to adapt and build upon existing projects) Good Regular expressions comprehension How to teach others effectively TDD/Unit testing Critical thinking How to integrate different skills and languages in a single project

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