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• Regular expressions - finding and comparing the first instance of a word

  - by Dan

  Hi there, I am currently trying to write a regular expression to pull links out of a page I have. The problem is the links need to be pulled out only if the links have 'stock' for example. This is an outline of what I have code wise: <td class="prd-details"> <a href="somepage"> ... <span class="collect unavailable"> </td> <td class="prd-details"> <a href="somepage"> ... <span class="collect available"> </td> What I would like to do is pull out the links only if 'collect available' is in the tag. I have tried to do this with the regular expression: (?s)prd-details[^=]+="([^"]+)" .+?collect{1}[^\s]+ available However on running it, it will find the first 'prd-details' class and keep going until it finds 'collect available', thereby taking the incorrect results. I thought by specifying the {1} after the word collect it would only use the first instance of the word it finds, but apparently I'm wrong. I've been trying to use different things such as positive and negative lookaheads but I cant seem to get anything to work. Might anyone be able to help me with this issue? Thanks, Dan

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• Selecting first instance of class but not nested instances via jQuery

  - by DA

  Given the following hypothetical markup: <ul class="monkey"> <li> <p class="horse"></p> <p class="cow"></p> </li> </ul> <dl class="monkey"> <dt class="horse"></dt> <dd class="cow"> <dl> <dt></dt> <dd></dd> </dl> <dl class="monkey"> <dt class="horse"></dt> <dd class="cow"></dd> </dl> </dd> </dl> I want to be able to grab the 'first level' of horse and cow classes within each monkey class. But I don't want the NESTED horse and cow classes. I started with .children, but that won't work with the UL example as they aren't direct children of .monkey. I can use find: $('.monkey').find('.horse, .cow') but that returns all instances, including the nested ones. I can filter the find: $('.monkey').find('.horse, .cow').not('.cow .horse, .cow .cow') but that prevents me from selecting nested instances on a second function call. So...I guess what I'm looking for is 'find first "level" of this descendant'. I could likely do this with some looping logic, but was wondering if there is a selector and/or some combo of selectors that would achieve that logic.

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• WPF data-bound ComboBox only shows first item of ItemsSource list

  - by Mark

  Hi all, I'm sure I'm doing something stupid but for the life of me I can't think of right now. I have a ComboBox that is data-bound to a list of Layout objects. The list is initially empty but things are added over time. When the list is updated by the model the first time, this update reflects properly in the ComboBox. However, subsequent updates never show up in the ComboBox even though I can see that the list itself contains these items. Since the first update works, I know the data-binding is OK - so what am I doing wrong here? Here's the XAML (abridged): <Grid HorizontalAlignment="Stretch"> <ComboBox ItemsSource="{Binding Path=SavedLayouts, diagnostics:PresentationTraceSources.TraceLevel=High}" DisplayMemberPath="Name" SelectedValuePath="Name" SelectedItem="{Binding LoadLayout}" Height="25" Grid.Row="1" Grid.Column="0"></ComboBox> </Grid> And the related part of the model: public IList<Layout> SavedLayouts { get { return _layouts; } } public Layout SaveLayout( String data_ ) { Layout theLayout = new Layout( SaveLayoutName ); _layouts.Add( theLayout ); try { return theLayout; } finally { PropertyChangedEventHandler handler = PropertyChanged; if( handler != null ) { handler( this, new PropertyChangedEventArgs( "SavedLayouts" ) ); } } } And finally, the layout class (abridged): public class Layout { public String Name { get; private set; } } In the output window, I can see the update occurring: System.Windows.Data Warning: 91 : BindingExpression (hash=64564967): Got PropertyChanged event from TickerzModel (hash=43624632) System.Windows.Data Warning: 97 : BindingExpression (hash=64564967): GetValue at level 0 from TickerzModel (hash=43624632) using RuntimePropertyInfo(SavedLayouts): List`1 (hash=16951421 Count=11) System.Windows.Data Warning: 76 : BindingExpression (hash=64564967): TransferValue - got raw value List`1 (hash=16951421 Count=11) System.Windows.Data Warning: 85 : BindingExpression (hash=64564967): TransferValue - using final value List`1 (hash=16951421 Count=11) But I get do not get this 11th item in the ComboBox. Any ideas?

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• Is C++ (one of) the best language to learn at first

  - by AlexV

  C++ is one of the most used programming language in the world since like 25+ years. My first job as programmer was in C++ and I coded in C++ everyday for nearly 4 years. Now I do mostly PHP, but I will forever cherish this C++ background. C++ has helped me understand many "under the hood" features/behaviors/restrictions of many other (and different) programming languages like PHP and Delphi. I'm a full time programmer for 6+ years now and since I have a quite varied programming background I often get questions by "newbies" as where to start to become a "good" programmer. I think C++ is one of the best language to start with because it gives you a real usefull experience that will last and will teach you how things work under the hood. It's not the easier one to learn for a newbie, but in my opinion it's one that will reward in the long term. I would like to know your opinion on this matter to add to my arguments when I guide "newbies". After this introduction, here's my question : Is C++ (one of) the best language to learn at first for you. Since it's subjective, I've marked this question as community wiki. EDIT: This question is not about why Java (or C# or any other language) is better than C++ to start with, it's about what's make C++ a good choice or not a good choice to learn as one of your firsts languages. For example, for me C++ made me understand how the memory works. Now today in many languages everything is managed by the garbadge collector and some people don't even know that. I'm glad I know how it works underneath and I think it can help you to write better code.

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• first data global gateway API - invalid XML problem

  - by B.Georg

  Hello, i am implementing the First Data Global Gateway API into a Java E-Commerce Web application. The problem that i have is that I get an error message SGS-020003: Invalid XML returned from the staging.linkpt.net server. By switching the optional entities off, I managed to locate the problematic entity. It is the Shipping entity. I have the following data inside it: <shipping> <zip>10105</zip> <phone>123456789</phone> <email>[email protected]</email> <name>DJBla</name> <state>NY</state> <address1>some city</address1> <address2>suite 6</address2> <city>New York</city> <country>US</country> </shipping> According to the First Data Global Gateway User Manual Version 1.1 everything is correct with my XML. Would anyone have an idea where the error could be? Kind Regards, B.Georg

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• Horizontal histogram won't accept input after the first input

  - by vincentbelkin

  So I'm making a program which is supposed to print a horizontal histogram of the lengths of words in its input. I don't know if most of it is OK since the main problem is it won't accept any input after the first one. Oh I also put comments on the parts I'm having some trouble with, like how to print "-" multiple times in order to represent histogram. I've tried making other versions of the code but I couldn't check if I'm close to getting it because again it won't accept another input after the first input. /*Write a program to print a histogram of the lengths of words in its input. It is easy to draw the histogram with the bars horizontal*/ #include <stdio.h> #define MAX 30 #define IN 1 #define OUT 0 int main() { int a,c,i,k,state,word[MAX]; a=0; k=0; state=OUT; for(i=0;i<MAX;i++) word[i]=0; while((c=getchar())!=EOF) { if(c==' '||c=='\t'||c=='\n') state=OUT; else state=IN; while(state==IN) a++; if(state==OUT) { word[i]=a; i++; } /*This part is hard for me, I don't know how to print X multiple times!*/ if((c==getchar())&&c==EOF) { for(i=0;i<MAX;i++) { for(i=0;i<=word[i];i++) putchar('-'); putchar('\n'); } } } }

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• Trying to override onbeforeunload in first step of form wizard

  - by Dirty Bird Design

  This pertains to a form wizard with 5 steps, I don't want the user to hit back and lose form data in any step 2-4. I have added a flag for the submit function and need to add this one for the first step. If they get there by accident and try and leave I dont want the cofirm dialog popping up. <script type="text/javascript"> $(document).ready(function(){ var action_is_post = false; $("form").submit(function () { action_is_post = true; }); //this is the trouble spot. on the first step the "navigation" of the form has a class of current (on step one = current) $(this).ready(function () { if ($("#stepDesc0").is(".current")) { action_is_post = true; } ); window.onbeforeunload = confirmExit; function confirmExit() { if (!action_is_post) return 'Using the browsers back, refresh or close button will cause you to lose all form data. Please use the Next and Back buttons on the form.'; } }); </script>

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• Style first 2 TextViews in Android ListView differently

  - by Kurtis Nusbaum

  I have a ListView and I want the first two entries in it to be displayed differently than the rest. Nothing fancy, I want them all to just be text views. But the first two entries need to have different sizes and weights than the rest. I tried modifying the ArrayAdapter class like so: private class BusStopAdapter<T> extends ArrayAdapter<T>{ public BusStopAdapter( Context context, int textViewResourceId, List<T> objects) { super(context, textViewResourceId, objects); } public View getView(int position, View convertView, ViewGroup parent) { TextView toReturn = (TextView)super.getView(position, convertView, parent); if(position == 0){ toReturn.setTextSize(12); toReturn.setText("Previous Bus: " + toReturn.getText()); toReturn.setPadding(0,0,0,0); } else if(position == 1){ toReturn.setTextSize(20); toReturn.setPadding( toReturn.getPaddingLeft(), 0, toReturn.getPaddingRight(), 0 ); toReturn.setText("Next Bus: " + toReturn.getText()); toReturn.setGravity(Gravity.CENTER_HORIZONTAL|Gravity.TOP); } return toReturn; } } But this inadvertantly causes some of the other textviews to take on these special attributes. I think it's because cause textviews get "recycled" in the AbsListAdapter class.

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• PowerShell function arguments: Can the first one be optional first?

  - by Johannes Rössel

  I have an advanced function in PowerShell, which roughly looks like this: function Foo { [CmdletBinding] param ( [int] $a = 42, [int] $b ) } The idea is that it can be run with either two, one or no arguments. However, the first argument to become optional is the first one. So the following scenarios are possible to run the function: Foo a b # the normal case, both a and b are defined Foo b # a is omitted Foo # both a and b are omitted However, normally PowerShell tries to fit the single argument into a. So I thought about specifying the argument positions explicitly, where a would have position 0 and b position 1. However, to allow for only b specified I tried putting a into a parameter set. But then b would need a different position depending on the currently-used parameter set. Any ideas how to solve this properly? I'd like to retain the parameter names (which aren't a and b actually), so using $args is probably a last resort. I probably could define two parameter sets, one with two mandatory parameters and one with a single optional one, but I guess the parameter names have to be different in that case, then, right?

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• jQuery ajax only works first time

  - by Michael Itzoe

  I have a table of data that on a button click certain values are saved to the database, while other values are retrieved. I need the process to be continuous, but I can only get it to work the first time. At first I was using .ajax() and .replaceWith() to rewrite the entire table, but because this overwrites the DOM it was losing events associated with the table. I cannot use .live() because I'm using stopPropagation() and .live() doesn't support it due to event bubbling. I was able to essentially re-bind the click event onto the table within the .ajax() callback, but a second call to the button click event did nothing. I changed the code to use .get() for the ajax and .html() to put the results in the table (the server-side code now returns the complete table sans the <table> tags). I no longer have to rebind the click event to the table, but subsequent clicks to the button still do nothing. Finally, I changed it to .load(), but with the same (non-) results. By "do nothing" I mean while the ajax call is returning the new HTML as expected, it's not being applied to the table. I'm sure it has something to do with altering the DOM, but I thought since I'm only overwriting the table contents and not the table object itself, it should work. Obviously I'm missing something; what is it? Edit: HTML: <table id="table1" class="mytable"> <tr> <td><span id="item1" class="myitem"></span> <td><span id="item2" class="myitem"></span> </tr> </table> <input id="Button1" type="button" value="Submit" /> jQuery: $( "Button1" ).click( function() { $( "table1" ).load( "data.aspx", function( data ) { //... } ); } );

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• breadth-first traversal of directory tree is not lazy

  - by user855443

  I try to traverse the diretory tree. A naive depth-first traversal seems not to produce the data in a lazy fashion and runs out of memory. I next tried a breadth first approach, which shows the same problem - it uses all the memory available and then crashes. the code i have is: getFilePathBreadtFirst :: FilePath -> IO [FilePath] getFilePathBreadtFirst fp = do fileinfo <- getInfo fp res :: [FilePath] <- if isReadableDirectory fileinfo then do children <- getChildren fp lower <- mapM getFilePathBreadtFirst children return (children ++ concat lower) return (children ++ concat () else return [fp] -- should only return the files? return res getChildren :: FilePath -> IO [FilePath] getChildren path = do names <- getUsefulContents path let namesfull = map (path </>) names return namesfull testBF fn = do -- crashes for /home/frank, does not go to swap fps <- getFilePathBreadtFirst fn putStrLn $ unlines fps I think all the code is either linear or tail recursive, and I would expect that the listing of filenames starts immediately, but in fact it does not. Where is the error in my code and my thinking? where have I lost lazy evaluation?

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• Why C++ is (one of) the best language to learn at first [closed]

  - by AlexV

  C++ is one of the most used programming language in the world since like 25+ years. My first job as programmer was in C++ and I coded in C++ everyday for nearly 4 years. Now I do mostly PHP, but I will forever cherish this C++ background. C++ has helped me understand many "under the hood" features/behaviors/restrictions of many other (and different) programming languages like PHP and Delphi. I'm a full time programmer for 6+ years now and since I have a quite varied programming background I often get questions by "newbies" as where to start to become a "good" programmer. I think C++ is one of the best language to start with because it gives you a real usefull experience that will last and will teach you how things work under the hood. It's not the easier one to learn for a newbie, but in my opinion it's the one who will reward the most in long term. I would like to know your opinion on this matter to add to my arguments when I guide "newbies". After this introduction, here's my question : Why C++ is for you (one of) the best language to learn at first. Since it's subjective, I've marked this question as community wiki.

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• Specific template for the first element.

  - by Kalinin

  I have a template: <xsl:template match="paragraph"> ... </xsl:template> I call it: <xsl:apply-templates select="paragraph"/> For the first element I need to do: <xsl:template match="paragraph[1]"> ... <xsl:apply-templates select="."/><!-- I understand that this does not work --> ... </xsl:template> How to call <xsl:apply-templates select="paragraph"/> (for the first element paragraph) from the template <xsl:template match="paragraph[1]">? So far that I have something like a loop. I solve this problem so (but I do not like it): <xsl:for-each select="paragraph"> <xsl:choose> <xsl:when test="position() = 1"> ... <xsl:apply-templates select="."/> ... </xsl:when> <xsl:otherwise> <xsl:apply-templates select="."/> </xsl:otherwise> </xsl:choose> </xsl:for-each>

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• Adding a first and last class to Wordpress' widget contents

  - by user571188

  In Wordpress, I'm looking for some way to add a "last" and a "first" class to list items inside Wordpress widgets. The HTML could look like this: <div class="widget-area"> <ul > <li class="widget_recent_comments"> <h3 class="widget-title">Recent comments</h3> <ul id="recentcomments"> <li class="recentcomments">Comment 1</li> <li class="recentcomments">Comment 2</li> <li class="recentcomments">Comment 3</li> <li class="recentcomments">Comment 4</li> </ul> </li> <li class="widget_my_links"> <h3 class="widget-title">My links</h3> <ul id="my-links"> <li class="item">Link 1</li> <li class="item">Link 2</li> <li class="item">Link 3</li> <li class="item">Link 4</li> <li class="item">Link 5</li> </ul> </li> </ul></div> In this example above i'd like to have first/last classes added to the li with "Comment 1", "Comment 4", "Link 1" and "Link 5". Is there an easy workaround for this? (I don't want to do this with javascript) Thank you.

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• Navigation Controller with Tab Bar only on first view

  - by dinoc

  I am seeking advice on how to start my project. I need to use a combination of the navigation controller and tabbar controller but on the second screen, I need the tabbar controller not to be there. Here is a brief description of the two main screens Screen 1 will have a tabbar controller with two tabs. The first tab is a tableview and when you tap on a table cell, it drills down to Screen 2. The second tab is just a filter view that updates the table in the first tab of Screen 1. Screen two is just a details screen from the cells of Screen 1. The catch is that I don't want the TabBar on Screen 2. I am struggling with how to get started. Do I start with a Navigation-based application since I need to be able to drill down? How do I just add a tab bar to the main screen of the navigation based app? I can't start with a Tab Bar application because if I load a navigation controller inside one of the views of the tab controller, then when I drill down inside the nav controller, the tab bar still stays on the next screen when I need it to go away. Any help would be appreciated.

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• what is the most elegant way of showing first week in a month

  - by ooo

  In C#, i want to show the first week in a calendar (in a html table) and i am trying to figure out the most elegant algorithm to generate the right days. If the first day of the week is not Sunday, i want to show the days of preceding month (like you would see on a regular calendar). So, as an input you have a current month. In this case May. I want to generate this: Month: May <table> <tr> <th>S</th> <th>M</th> <th>T</th> <th>W</th> <th>TH</th> <th>F</th> <th>Sa</th> </tr> <tr> <td>25</td> <td>26</td> <td>27</td> <td>28</td> <td>29</td> <td>30</td> <td>1</td> </tr></table> so it should display something like this (ignore the alignment) S | M | T | W | Th | F | Sa | 25 - 26 - 27 - 28 - 29 - 30 - 1 given that each month would have the start of day be a different day of the week, i am trying to figure out an elegant way to get the values of this data using the DateTime object. I see it has a dayofweek property on a date. i am generating this table in C# on my server to pass down to a html page.

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• First Time Working With Others?

  - by cam

  I've been at my very first programming job for about 8 months now and I've learned incredible amounts so far. Unfortunately, I'm the sole developer for a small startup company for internal applications. For the first time ever though, I'll be handing off some of my projects to someone else when I leave this job. I've documented all my projects thoroughly (at least I think so), but I still feel nervous about someone else reading my code. For example, I've always done this sort of thing. for (int i = 0; i < blah.length; i++) { //Do stuff } Should I name 'i' something descriptive? It's only a temporary variable, and will only exist within that loop, and it seems that it's pretty obvious what the loop does with 'i'. This is just one example. Another one is that I name variables differently... I don't really conform to a standard of naming besides starting all private members with an underscore. Are there any resources that could show me how to make it easier for the next developer? Are there standards for this type of thing?

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• Retrieving the first picture with a HTML parser

  - by justin01

  Hey guys, (Not a native english speaker) I'm doing a personal project in PHP in which I use the Simple HTML Parser to parse the HTML of a given URL and retrieve the first image in a DIV that have a specific ID or class (maincontent, content, main, wrapper, etc. - it's all in an array) and ignore ads. The goal is to take this image and make a thumbnail with it, pretty much like on Digg and others. I thought everything was working fine until I tried my script with the website Snopes ("http://www.snopes.com/photos/animals/luckycoyote.asp" <- this page more exactly). The source of the first image it gets is: " graphics/luckycoyote1.jpg ". So far, to correct this problem I created a little function that gets the domain name of the given URL and insert it before the IMG's source attribute. So for sites like Snopes.com, it gives me: "http://www.snopes.com/graphics/luckycoyote1.jpg" ... while the real URL for this image is "http://www.snopes.com*/photos/animals/graphics/luckycoyote1.jpg*" (or, more precisely: " http://graphics1.snopes.com/photos/animals/graphics/luckycoyote1.jpg " - note the subdomain here). So my main question is: how can I externally/dynamically retrieve the full URL address of an image ("absolute path") when I am only given the "relative path"? I'm pretty sure this is possible, since when I paste the link in Facebook's "What are you doing?" field for example, it gives me the correct path to the image while on the website, the source of the image is only (example) "image/photo/example.jpg". Thank you for your time.

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• php:: apply backticks to first word in sentence

  - by Hailwood

  Hi guys, basically what I am trying to do is, I have an array that looks something like this: array( array( 'select' =>'first string', 'escape' => true ), array( 'select' =>'second', 'escape' => true ), array( 'select' =>'the third string', 'escape' => true ), array( 'select' =>'fourth string', 'escape' => false ), ) I am looping over it and I want to end up with this output array( array( 'select' =>'`first` string', 'escape' => true ), array( 'select' =>'`second`', 'escape' => true ), array( 'select' =>'`the` third string', 'escape' => true ), array( 'select' =>'fourth string', 'escape' => false ), ) so basic rules are backticks are only applied if escape is true backticks are only applied to the first word in a sentence if there is only one word backticks are applied to the word My plan was to use if($item['escape']) { $pos = (strpos($item['select'], ' ') === false ? strlen($item['select']) : strpos($item['select'], ' ')); $item['select'] = '`' . substr($item['select'], 0, $pos) . '`' . substr($item['select'], $pos, strlen($item['select'])); } but the $item['select'] = line seems rather long winded, is there a better way to write it?

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• c# logic to get the first non-repeating(distinct) character from the string

  - by NoviceToDotNet

  In c# i want to create logic that if i a string like abcabda is passed to a method then it should return first non repeative character from string like in above it should return c. i am unable to convert a string to array of character then how to make comparison of each array character to the string and return the first non repeative character. CanI make it like this? class A { static void main() { A a=new A(); char ch=a.m1(abcabd); } } class B { char m1(string s) { string s1=s; char[] ch1=new char[s.length]; for(int x=0; x<s.length;x++) { ch1[x]=s[x]; } for(int x=0; x<s.length; x++) { for(int y=0; y<s.lenth; y++) { if(s[x]=ch1[y]) { /// here i am confused how to create logic for comparison please let me know // and how to return the character } } } } }

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• JPA - insert and retrieve clob and blob types

  - by pachunoori.vinay.kumar(at)oracle.com

  This article describes about the JPA feature for handling clob and blob data types.You will learn the following in this article. @Lob annotation Client code to insert and retrieve the clob/blob types End to End ADFaces application to retrieve the image from database table and display it in web page. Use Case Description Persisting and reading the image from database using JPA clob/blob type. @Lob annotation By default, TopLink JPA assumes that all persistent data can be represented as typical database data types. Use the @Lob annotation with a basic mapping to specify that a persistent property or field should be persisted as a large object to a database-supported large object type. A Lob may be either a binary or character type. TopLink JPA infers the Lob type from the type of the persistent field or property. For string and character-based types, the default is Clob. In all other cases, the default is Blob. Example Below code shows how to use this annotation to specify that persistent field picture should be persisted as a Blob. public class Person implements Serializable {    @Id    @Column(nullable = false, length = 20)    private String name;    @Column(nullable = false)    @Lob    private byte[] picture;    @Column(nullable = false, length = 20) } Client code to insert and retrieve the clob/blob types Reading a image file and inserting to Database table Below client code will read the image from a file and persist to Person table in database.                       Person p=new Person();                      p.setName("Tom");                      p.setSex("male");                      p.setPicture(writtingImage("Image location"));// - c:\images\test.jpg                       sessionEJB.persistPerson(p); //Retrieving the image from Database table and writing to a file                       List<Person> plist=sessionEJB.getPersonFindAll();//                      Person person=(Person)plist.get(0);//get a person object                      retrieveImage(person.getPicture());   //get picture retrieved from Table //Private method to create byte[] from image file  private static byte[] writtingImage(String fileLocation) {      System.out.println("file lication is"+fileLocation);     IOManager manager=new IOManager();        try {           return manager.getBytesFromFile(fileLocation);                    } catch (IOException e) {        }        return null;    } //Private method to read byte[] from database and write to a image file    private static void retrieveImage(byte[] b) {    IOManager manager=new IOManager();        try {            manager.putBytesInFile("c:\\webtest.jpg",b);        } catch (IOException e) {        }    } End to End ADFaces application to retrieve the image from database table and display it in web page. Please find the application in this link. Following are the j2ee components used in the sample application. ADFFaces(jspx page) HttpServlet Class - Will make a call to EJB and retrieve the person object from person table.Read the byte[] and write to response using Outputstream. SessionEJBBean - This is a session facade to make a local call to JPA entities JPA Entity(Person.java) - Person java class with setter and getter method annotated with @Lob representing the clob/blob types for picture field.

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• JavaScript Class Patterns

  - by Liam McLennan

  To write object-oriented programs we need objects, and likely lots of them. JavaScript makes it easy to create objects: var liam = { name: "Liam", age: Number.MAX_VALUE }; But JavaScript does not provide an easy way to create similar objects. Most object-oriented languages include the idea of a class, which is a template for creating objects of the same type. From one class many similar objects can be instantiated. Many patterns have been proposed to address the absence of a class concept in JavaScript. This post will compare and contrast the most significant of them. Simple Constructor Functions Classes may be missing but JavaScript does support special constructor functions. By prefixing a call to a constructor function with the ‘new’ keyword we can tell the JavaScript runtime that we want the function to behave like a constructor and instantiate a new object containing the members defined by that function. Within a constructor function the ‘this’ keyword references the new object being created -  so a basic constructor function might be: function Person(name, age) { this.name = name; this.age = age; this.toString = function() { return this.name + " is " + age + " years old."; }; } var john = new Person("John Galt", 50); console.log(john.toString()); Note that by convention the name of a constructor function is always written in Pascal Case (the first letter of each word is capital). This is to distinguish between constructor functions and other functions. It is important that constructor functions be called with the ‘new’ keyword and that not constructor functions are not. There are two problems with the pattern constructor function pattern shown above: It makes inheritance difficult The toString() function is redefined for each new object created by the Person constructor. This is sub-optimal because the function should be shared between all of the instances of the Person type. Constructor Functions with a Prototype JavaScript functions have a special property called prototype. When an object is created by calling a JavaScript constructor all of the properties of the constructor’s prototype become available to the new object. In this way many Person objects can be created that can access the same prototype. An improved version of the above example can be written: function Person(name, age) { this.name = name; this.age = age; } Person.prototype = { toString: function() { return this.name + " is " + this.age + " years old."; } }; var john = new Person("John Galt", 50); console.log(john.toString()); In this version a single instance of the toString() function will now be shared between all Person objects. Private Members The short version is: there aren’t any. If a variable is defined, with the var keyword, within the constructor function then its scope is that function. Other functions defined within the constructor function will be able to access the private variable, but anything defined outside the constructor (such as functions on the prototype property) won’t have access to the private variable. Any variables defined on the constructor are automatically public. Some people solve this problem by prefixing properties with an underscore and then not calling those properties by convention. function Person(name, age) { this.name = name; this.age = age; } Person.prototype = { _getName: function() { return this.name; }, toString: function() { return this._getName() + " is " + this.age + " years old."; } }; var john = new Person("John Galt", 50); console.log(john.toString()); Note that the _getName() function is only private by convention – it is in fact a public function. Functional Object Construction Because of the weirdness involved in using constructor functions some JavaScript developers prefer to eschew them completely. They theorize that it is better to work with JavaScript’s functional nature than to try and force it to behave like a traditional class-oriented language. When using the functional approach objects are created by returning them from a factory function. An excellent side effect of this pattern is that variables defined with the factory function are accessible to the new object (due to closure) but are inaccessible from anywhere else. The Person example implemented using the functional object construction pattern is: var john = new Person("John Galt", 50); console.log(john.toString()); var personFactory = function(name, age) { var privateVar = 7; return { toString: function() { return name + " is " + age * privateVar / privateVar + " years old."; } }; }; var john2 = personFactory("John Lennon", 40); console.log(john2.toString()); Note that the ‘new’ keyword is not used for this pattern, and that the toString() function has access to the name, age and privateVar variables because of closure. This pattern can be extended to provide inheritance and, unlike the constructor function pattern, it supports private variables. However, when working with JavaScript code bases you will find that the constructor function is more common – probably because it is a better approximation of mainstream class oriented languages like C# and Java. Inheritance Both of the above patterns can support inheritance but for now, favour composition over inheritance. Summary When JavaScript code exceeds simple browser automation object orientation can provide a powerful paradigm for controlling complexity. Both of the patterns presented in this article work – the choice is a matter of style. Only one question still remains; who is John Galt?

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• Display exception information and Debug.Print() messages in Immediate Window

  - by Timwi

  A friend of mine claims that calls to Debug.Print() as well as first-chance exception notifications appear in the Immediate Window for him. I found this surprising; for me they only appear in the Output Window. MSDN claims (here) that you can implicitly enable them in the Immediate Window by explicitly disabling them in the Output Window. But that doesn't work for me; the messages are not shown in either window if I disable this. The Immediate Window remains empty. How do I get the Immediate Window to display this information?

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• How can I store data in a table as a trie? (SQL Server)

  - by Matt

  Hi, To make things easier, the table contains all the words in the English dictionary. What I would like to do is be able to store the data as a trie. This way I can traverse the different branches of the trie and return the most relevant result. First, how do I store the data in the table as a trie? Second, how do I traverse the tree? If it helps at all, the suggestion in this previous question is where this question was sparked from. Please make sure it's SQL we're talking about. I understood the Mike Dunlavey's C implementation because of pointers but can't see how this part (The trie itself) works in SQL. Thanks, Matt

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• Can you pass by reference in Java?

  - by dbones

  Hi. Sorry if this sounds like a newbie question, but the other day a Java developer mentioned about passing a paramter by reference (by which it was ment just pass a Reference object) From a C# perspective I can pass a reference type by value or by reference, this is also true to value types I have written a noddie console application to show what i mean.. can i do this in Java? namespace ByRefByVal { class Program { static void Main(string[] args) { //Creating of the object Person p1 = new Person(); p1.Name = "Dave"; PrintIfObjectIsNull(p1); //should not be null //A copy of the Reference is made and sent to the method PrintUserNameByValue(p1); PrintIfObjectIsNull(p1); //the actual reference is passed to the method PrintUserNameByRef(ref p1); //<-- I know im passing the Reference PrintIfObjectIsNull(p1); Console.ReadLine(); } private static void PrintIfObjectIsNull(Object o) { if (o == null) { Console.WriteLine("object is null"); } else { Console.WriteLine("object still references something"); } } /// <summary> /// this takes in a Reference type of Person, by value /// </summary> /// <param name="person"></param> private static void PrintUserNameByValue(Person person) { Console.WriteLine(person.Name); person = null; //<- this cannot affect the orginal reference, as it was passed in by value. } /// <summary> /// this takes in a Reference type of Person, by reference /// </summary> /// <param name="person"></param> private static void PrintUserNameByRef(ref Person person) { Console.WriteLine(person.Name); person = null; //this has access to the orginonal reference, allowing us to alter it, either make it point to a different object or to nothing. } } class Person { public string Name { get; set; } } } If it java cannot do this, then its just passing a reference type by value? (is that fair to say) Many thanks Bones

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