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  • What to do when ServerSocket throws IOException and keeping server running

    - by s5804
    Basically I want to create a rock solid server. while (keepRunning.get()) { try { Socket clientSocket = serverSocket.accept(); ... spawn a new thread to handle the client ... } catch (IOException e) { e.printStackTrace(); // NOW WHAT? } } In the IOException block, what to do? Is the Server socket at fault so it need to be recreated? For example wait a few seconds and then serverSocket = ServerSocketFactory.getDefault().createServerSocket(MY_PORT); However if the server socket is still OK, then it is a pity to close it and kill all previously accepted connections that are still communicating. EDIT: After some answers, here my attempt to deal with the IOException. Would the implementation be guaranteeing keeping the server up and only re-create server socket when only necessary? while (keepRunning.get()) { try { Socket clientSocket = serverSocket.accept(); ... spawn a new thread to handle the client ... bindExceptionCounter = 0; } catch (IOException e) { e.printStackTrace(); recreateServerSocket(); } } private void recreateServerSocket() { while (keepRunning) { try { logger.info("Try to re-create Server Socket"); ServerSocket socket = ServerSocketFactory.getDefault().createServerSocket(RateTableServer.RATE_EVENT_SERVER_PORT); // No exception thrown, then use the new socket. serverSocket = socket; break; } catch (BindException e) { logger.info("BindException indicates that the server socket is still good.", e); bindExceptionCounter++; if (bindExceptionCounter < 5) { break; } } catch (IOException e) { logger.warn("Problem to re-create Server Socket", e); e.printStackTrace(); try { Thread.sleep(30000); } catch (InterruptedException ie) { logger.warn(ie); } } } }

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  • Problems with rails and saving to the database.

    - by Grantismo
    I've been having some difficulty in understanding the source of a problem. Below is a listing of the model classes. Essentially the goal is to have the ability to add sentences to the end of the story, or to add stories to an existing sentence_block. Right now, I'm only attempting to allow users to add sentences, and automatically create a new sentence_block for the new sentence. class Story < ActiveRecord::Base has_many :sentence_blocks, :dependent => :destroy has_many :sentences, :through => :sentence_blocks accepts_nested_attributes_for :sentence_blocks end class SentenceBlock < ActiveRecord::Base belongs_to :story has_many :sentences, :dependent => :destroy end class Sentence < ActiveRecord::Base belongs_to :sentence_block def story @sentence_block = SentenceBlock.find(self.sentence_block_id) Story.find(@sentence_block.story_id) end end The problem is occurring when using the show method of the Story. The Story method is as follows, and the associated show method for a sentence is also included. Sentence.show def show @sentence = Sentence.find(params[:id]) respond_to do |format| format.html {redirect_to(@sentence.story)} format.xml { render :xml => @sentence } end end Story.show def show @story = Story.find(params[:id]) @sentence_block = @story.sentence_blocks.build @new_sentence = @sentence_block.sentences.build(params[:sentence]) respond_to do |format| if @new_sentence.content != nil and @new_sentence.sentence_block_id != nil and @sentence_block.save and @new_sentence.save flash[:notice] = 'Sentence was successfully added.' format.html # new.html.erb format.xml { render :xml => @story } else @sentence_block.destroy format.html format.xml { render :xml => @story } end end end I'm getting a "couldn't find Sentence_block without and id" error. So I'm assuming that for some reason the sentence_block isn't getting saved to the database. Can anyone help me with my understanding of the behavior and why I'm getting the error? I'm trying to ensure that every time the view depicts show for a story, an unnecessary sentence_block and sentence isn't created, unless someone submits the form, I'm not really sure how to accomplish this. Any help would be appreciated.

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  • How to make a php function contain mysql commands

    - by bob
    I want to create a simple menu function which can call it example get_menu() Here is my current code. <?php $select = 'SELECT * FROM pages'; $query = $db->rq($select); while ($page = $db->fetch($query)) { $id = $page['id']; $title = $page['title']; ?> <a href="page.php?id<?php echo $id; ?>" title="<?php echo $title; ?>"><?php echo $title; ?></a> <?php } ?> How to do that in? function get_menu() { } Let me know.

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  • User Management: Managing users in user-defined "groups", database schema and logistics

    - by Kevin Brown
    I'm a noob, development wise and logistically-wise. I'm developing a site that lets people take a test... My client wants the ability for a user with the roll/privledge "admin" (a step below a super-admin) to be allowed to create users and only see/edit the users that they create... The users created in that "category" or group need some information that their superior provides. For example, I log in as a "manager", I have the ability to invite people to take the test, and manage those people. Before adding those people, I will have filled out a short survey about myself... Right now, the users that are invited will be asked some of the same questions as the manager. I'd like to cut down the redundancy by using the information put into the database by the manager and apply it to the invited users. How do I set up my database to work with this criterion? I'm a little confused about how to do this! Let me know if I can add more details... (This is a mysql and php app)

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  • Python: needs more than 1 value to unpack

    - by Rosarch
    What am I doing wrong to get this error? replacements = {} replacements["**"] = ("<strong>", "</strong>") replacements["__"] = ("<em>", "</em>") replacements["--"] = ("<blink>", "</blink>") replacements["=="] = ("<marquee>", "</marquee>") replacements["@@"] = ("<code>", "</code>") for delimiter, (open_tag, close_tag) in replacements: # error here message = self.replaceFormatting(delimiter, message, open_tag, close_tag); The error: Traceback (most recent call last): File "", line 1, in for shit, (a, b) in replacements: ValueError: need more than 1 value to unpack All the values tuples have two values. Right?

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  • How to replace empty string with zero in comma-separated string?

    - by dsaccount1
    "8,5,,1,4,7,,,,7,,1,9,3,6,,,8,6,3,9,,2,5,4,,,,,3,2,,,7,4,1,1,,4,,6,9,,5,,,,5,,,1,,6,3,,,6,5,,,,7,4,,1,7,6,,,,8,,5,,,7,1,,3,9," I'm doing a programming challenge where i need to parse this sequence into my sudoku script. Need to get the above sequence into 8,5,0,1,4,7,0,0,0,7,0,1,9,3,6,0,0,8......... I tried re but without success, help is appreciated, thanks.

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  • linux tooling for starting as a net programmer

    - by alfredo dobrekk
    What are the linux developper tools to do the things i do with .NET in my windows environnement : I would like to port my client server application that runs under winform/nhibernate/sql server. Language c# Database SQL server ORM Nhibernate Source control SVN / Tortoise Unit testing Nunit Continuous integration Cruise Control Should i go java and eclipse ? Python and ??? Ruby and ??? Is there some IDE that allow me to manage all these processes under linux ?

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  • How do I implement multiple kinds of an object in OOP?

    - by Jeremy Rudd
    I have multiple kinds of an object, say Car for example. Do I have each kind in an inherited class/subclass of Car? Do I place these under a cartype namespace so as not to mess up the main namespace? Then later when I need an array of cars, should I declare it as var currentCars():Car or var currentCars():Object? Would the former support any subclass of Car?

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  • LaTex: how does the include-command work?

    - by HH
    I supposed the include-command copy-pastes code in the compilation, it is wrong because the code stopped working. Please, see the middle part in the code. I only copy-pasted the code to the file and added the include-command. $ cat results/frames.tex 10.31 & 8.50 & 7.40 \\ 10.34 & 8.53 & 7.81 \\ 8.22 & 8.62 & 7.78 \\ 10.16 & 8.53 & 7.44 \\ 10.41 & 8.38 & 7.63 \\ 10.38 & 8.57 & 8.03 \\ 10.13 & 8.66 & 7.41 \\ 8.50 & 8.60 & 7.15 \\ 10.41 & 8.63 & 7.21 \\ 8.53 & 8.53 & 7.12 \\ Latex code \begin{table} \begin{tabular}{ | l | m | r |} \hline $t$ / s & $d_{1}$ / s & $d_{2}$ / s \\ $\Delta h = 0,01 s$ & $\Delta d = 0,01 s$ & $\Delta d = 0,01 s$ \\ \hline % I JUST COPIED THE CODE from here to the file, included. % It stopped working, why? \include{results/frames.tex} \hline $\pi (\frac{d_{1}}{2} - \frac{d_{2}}{2})$ & $2 \pi R h$ & $2 \pi r h$ \\ \hline \end{tabular} \end{table}

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  • Beginning OS X & iPhone Development: Reference texts

    - by twinbornJoint
    My programming experience is limited to xhtml, css, php, sql and some javascript. The books I have are: Programming in Objective-C 2nd Edition Beginning iPhone Development Cocoa(R) Programming for Mac(R) OS X (Paperback) Is there anything else I will need to get started on my journey into iPhone/OS X development?

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  • Should I add try/catch around when casting on an attribute of JSP implicit object?

    - by Michael Mao
    Hi all: Basically what I mean is like this: List<String[]> routes = (List<String[]>)application.getAttribute("routes"); For the above code, it tries to get an attribute named "routes" from the JSP implicit object - application. But as everyone knows, after this line of code, routes may very well contains a null - which means this application hasn't got an attribute named "routes". Is this "casting on null" good programming practice in Java or not? Basically I try to avoid exceptions such as java.io.InvalidCastException I reckon things like this are more as "heritage" of Java 1.4 when generic types were not introduced to this language. So I guess everything stored in application attributes as Objects (Similar to traditional ArrayList). And when you do "downcast", there might be invalid casts. What would you do in this case? Update: Just found that although in the implicit object application I did store a List of String arrays, when I do this : List<double[]> routes = (List<double[]>)application.getAttribute("routes"); It doesn't produce any error... And I felt not comfortable already... And even with this code: out.print(routes.get(0)); It does print out something strange : [Ljava.lang.String;@18b352f Am I printing a "pointer to String"? I can finally get an exception like this: out.print(routes.get(0)[1]); with error : java.lang.ClassCastException: [Ljava.lang.String; Because it was me to add the application attribute, I know which type should it be cast to. I feel this is not "good enough", what if I forget the exact type? I know there are still some cases where this sort of thing would happen, such as in JSP/Servlet when you do casting on session attributes. Is there a better way to do this? Before you say:"OMG, why you don't use Servlets???", I should justify my reason as this: - because my uni sucks, its server can only work with Servlets generated by JSP, and I don't really want to learn how to fix issues like that. look at my previous question on this , and this is uni homework, so I've got no other choice, forget all about war, WEB-INF,etc, but "code everything directly into JSP" - because the professors do that too. :)

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  • How to extract only part of string in PHP?

    - by shin
    I have a following string and I want to extract image123.jpg. ..here_can_be_any_length "and_here_any_length/image123.jpg" and_here_also_any_length image123 can be any length (newimage123456 etc) and with extension of jpg, jpeg, gif or png. I assume I need to use preg_match, but I am not really sure how to code it. Any help will be appreciated. Thanks in advance.

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  • Loading attribute in XPATH, problem

    - by Nguyen Quoc Hung
    I've got a question about loading attribute in XPATH. I write short XML code to test: <?xml version="1.0" encoding="iso-8859-1"?> <?xml-stylesheet type="text/xsl" href="testDate.xsl"?> <element attribute="1/1/2100"> Hung </element> My XSL code: <?xml version="1.0" encoding="iso-8859-1"?> <xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform"> <!--Handle the document: set up HTML page--> <xsl:template match="/"> <html> <head> </head> <body> This is a test <xsl:value-of select="element@attribute"/> </body> </html> </xsl:template> </xsl:stylesheet> Why it produces an error when loading the stylesheet? Would you please help me explain this? Thank you

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  • Problem with Postgres FOR LOOP

    - by user341831
    Hi all, Ich have a problem in postgres function: CREATE OR REPLACE FUNCTION linkedRepoObjects(id bigint) RETURNS int AS $$ DECLARE catNumber int DEFAULT 0; DECLARE cat RECORD; BEGIN WITH RECURSIVE children(categoryid,category_fk) AS ( SELECT categoryid, category_fk FROM b2m.category_tab WHERE categoryid = 1 UNION ALL SELECT c1.categoryid,c1.category_fk FROM b2m.category_tab c1, children WHERE children.categoryid = c1.category_fk ) FOR cat IN SELECT * FROM children LOOP IF EXISTS (SELECT 1 FROM b2m.repoobject_tab WHERE category_fk = cat.categoryid) THEN catNumber = catNumber +1 END IF; END LOOP; RETURN catNumber; END; $$ LANGUAGE 'plpgsql'; I've got error: FEHLER: Syntaxfehler bei »FOR« LINE 1: ...dren WHERE children.categoryid = c1.category_fk ) FOR $2 I... I'm a newbee in Postgres. Please help. Thanx in advance

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  • Java - Console-like web applet.

    - by Dean
    Hey, I've been developing an application in the windows console with Java, and want to put it online in all of its console-graphics-glory. Is there a simple web applet API I can use to port my app over? I'm just using basic System.out and System.in functionality, but I'm happy to rebuild my I/O wrappers. I think something along these lines would be a great asset to any beginning Java developers who want to put their work online.

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  • Using XSL-FO and HTML?

    - by buggy1985
    Hi, I'm trying to transform some XML-data to HTML with XSLT for my bachelor thesis. My professor wants me to consider XSL-FO too, or at least to write some word about it. But I'm very noob to this. So my questions are: Can I combine FO with HTML? Can I use FO istead of HTML and CSS? If yes, how will my browser render this? Are there any examples/tutorials on how to transform xml into web pages with FO? Thank you very much.

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