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• jsf, richfaces, popup window

  - by Hubidubi

  Hi I would like to make a list-detail view with richfaces. There will be a link for every record in the list that should open a new window containing record details. I tried to implement the link this way: <a4j:commandLink oncomplete="window.open('/pages/serviceDetail.jsf','popupWindow', 'dependent=yes, menubar=no, toolbar=no, height=500, width=400')" actionListener="#{monitoringBean.recordDetail}" value="details" /> I use <a4j:keepAlive beanName="monitoringBean" ajaxOnly="false" /> for both the list and the detail page. recordDetail method fills the data of the selected record to a variable of the bean that I would like to display on the detail page. The problem is that keepalive doesn't work, so I get new bean instance on the detail page every time. So the the previously selected record from the other bean is not accessible here. Is there a way to pass parameter (id) to the detail page to handle record selection. Or is there any way to make keepalive work? (I this this would be the easiest). Thanks

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• Android Camera intent creating two files

  - by Kyle Ramstad

  I am making a program that takes a picture and then shows it's thumbnail. When using the emulator all goes well and the discard button deletes the photo. But on a real device the camera intent saves the image at the imageUri variable and a second one that is named like if I had just opened up the camera and took a picture by itself. private static final int CAMERA_PIC_REQUEST = 1337; /** Called when the activity is first created. */ @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.camera); //start camera values = new ContentValues(); values.put(MediaStore.Images.Media.TITLE, "New Picture"); values.put(MediaStore.Images.Media.DESCRIPTION,"From your Camera"); imageUri = getContentResolver().insert(MediaStore.Images.Media.EXTERNAL_CONTENT_URI, values); image = (ImageView) findViewById(R.id.ImageView01); Intent intent = new Intent(MediaStore.ACTION_IMAGE_CAPTURE); intent.putExtra(MediaStore.EXTRA_OUTPUT, imageUri); startActivityForResult(intent, CAMERA_PIC_REQUEST); //save the image buttons Button save = (Button) findViewById(R.id.Button01); Button close = (Button) findViewById(R.id.Button02); } @Override protected void onActivityResult(int requestCode, int resultCode, Intent data) { if (requestCode == CAMERA_PIC_REQUEST && resultCode == RESULT_OK) { try{ thumbnail = MediaStore.Images.Media.getBitmap(getContentResolver(), imageUri); image.setImageBitmap(thumbnail); } catch(Exception e){ e.printStackTrace(); } } else{ finish(); } } public void myClickHandler(View view) { switch (view.getId()) { case R.id.Button01: finish(); break; case R.id.Button02: dicard(); } } private void dicard(){ getContentResolver().delete(imageUri, null, null); finish(); }

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• map operator [] operands

  - by Jamie Cook

  Hi all I have the following in a member function int tt = 6; vector<set<int>>& temp = m_egressCandidatesByDestAndOtMode[tt]; set<int>& egressCandidateStops = temp.at(dest); and the following declaration of a member variable map<int, vector<set<int>>> m_egressCandidatesByDestAndOtMode; However I get an error when compiling (Intel Compiler 11.0) 1>C:\projects\svn\bdk\Source\ZenithAssignment\src\Iteration\PtBranchAndBoundIterationOriginRunner.cpp(85): error: no operator "[]" matches these operands 1> operand types are: const std::map<int, std::vector<std::set<int, std::less<int>, std::allocator<int>>, std::allocator<std::set<int, std::less<int>, std::allocator<int>>>>, std::less<int>, std::allocator<std::pair<const int, std::vector<std::set<int, std::less<int>, std::allocator<int>>, std::allocator<std::set<int, std::less<int>, std::allocator<int>>>>>>> [ const int ] 1> vector<set<int>>& temp = m_egressCandidatesByDestAndOtMode[tt]; 1> ^ I know it's got to be something silly but I can't see what I've done wrong.

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• How stop mp3 playing started with audioplayer

  - by bucche

  Hi, My application consists of a table view. row1, row2, row3.... When a cell is touched a different mp3 starts to play (row1.mp3, row2.mp3, row3.mp3....). it works! but i have a problem: i am not able to stop previous mp3, so if i touch a second cell i have 2 mp3s playing... if i touch a third cell i have 3 mp3s and so on... i want to stop mp3 that started before and play mp3 that is related to touched cell... during my tries, i created a variable to show some alerts if the player plays or not and when i am "inside the if" i used [myAudioPlayer stop].. i see the correct alert but mp3 doesn't stop. here is my code - (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath { NSArray *elementi = [[array objectAtIndex:indexPath.row] componentsSeparatedByString:@"|"]; NSURL *url = [NSURL fileURLWithPath:[NSString stringWithFormat:@"%@/%@.mp3", [[NSBundle mainBundle] resourcePath],[elementi objectAtIndex:1]]]; NSError *error; myAudioPlayer = [[AVAudioPlayer alloc] initWithContentsOfURL:url error:&error]; myAudioPlayer.numberOfLoops = -1; if (inEsecuzione == 0) { UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"1" message:@"1" delegate:nil cancelButtonTitle:@"OK"otherButtonTitles:nil]; [alert show]; [alert release]; [myAudioPlayer play]; inEsecuzione = 1; } else { UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"2" message:@"2" delegate:nil cancelButtonTitle:@"OK"otherButtonTitles:nil]; [alert show]; [alert release]; [myAudioPlayer stop]; inEsecuzione = 0; } } as i wrote before, i am not able to stop previous mp3

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• using 'or' operator not working for menu

  - by John Wilkes

  In my code here, I have a CSS class called "active" which I use if the $_GET['page'] == tutorials, php, mysql, etc... The problem is, even if the 'page' variable is not equal to any of these values, the Tutorials button in this case is still active for some reason. Any ideas why this would be happening? Am I using the 'or' (||) operand incorrectly? <?php if($_GET['page'] == 'tutorials' || 'php' || 'mysql' || 'html' || 'css' || 'js') { ?> <li class="active"> <?php } else { ?> <li> <?php } ?> <a href="index.php?page=tutorials">Tutorials</a> <ul> <li><a href="index.php?page=php">PHP</a></li> <li><a href="index.php?page=mysql">MySQL</a></li> <li><a href="index.php?page=html">HTML</a></li> <li><a href="index.php?page=css">CSS</a></li> <li><a href="index.php?page=js">JS</a></li> </ul> </li>

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• Self referencing userdata and garbage collection

  - by drtwox

  Because my userdata objects reference themselves, I need to delete and nil a variable for the garbage collector to work. Lua code: obj = object:new() -- -- Some time later obj:delete() -- Removes the self reference obj = nil -- Ready for collection C Code: typedef struct { int self; // Reference to the object // Other members and function references removed } Object; // Called from Lua to create a new object static int object_new( lua_State *L ) { Object *obj = lua_newuserdata( L, sizeof( Object ) ); // Create the 'self' reference, userdata is on the stack top obj->self = luaL_ref( L, LUA_REGISTRYINDEX ); // Put the userdata back on the stack before returning lua_rawgeti( L, LUA_REGISTRYINDEX, obj->self ); // The object pointer is also stored outside of Lua for processing in C return 1; } // Called by Lua to delete an object static int object_delete( lua_State *L ) { Object *obj = lua_touserdata( L, 1 ); // Remove the objects self reference luaL_unref( L, LUA_REGISTRYINDEX, obj->self ); return 0; } Is there some way I can set the object to nil in Lua, and have the delete() method called automatically? Alternatively, can the delete method nil all variables that reference the object? Can the self reference be made 'weak'?

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• XPath expression exception

  - by fftoolbar

  Hi I am not really sure if i am doing this right with XPath expression. I am trying to locate a text on DOM and this text is assingned to a variable. I have text stored in SQLite and i have retrievd the text and i am trying to locate it on the webpage which actually contains the text. so i ahve the following code: var searchText = dataset[x]['selectedText']; alert(dataset[x]['selectedText']); var res = googbar_frames[0].contentDocument.evaluate("//*[.=searchText]",googbar_frames[0].contentDocument.body,null,XPathResult.ANY_TYPE,null); alert(res.snapshotLength); And i get the following error. Error: Permission denied for <http://en.wikipedia.org> to call method XPathException.toString on <>. Error: Permission denied for <http://en.wikipedia.org> to call method XPathException.toString on <>. Have got the expression correct. I am trying to look for the text on DOM. Or am i going wrong somwehere? cheers

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• jquery checkbox and array help

  - by sea_1987

  Hi There I need to get the names and values of checkboxes that have been checked into an array name selected, I cannot for life of me get it working, below is my attempt, if someone could clrify what I am doing wrong that would be brilliant. //Location AJAX //var dataObject = new Object(); var selected = new Array(); $('#areas input.radio').change(function(){ // will trigger when the checked status changes var checked = $(this).attr("checked"); // will return "checked" or false I think. // Do whatever request you like with the checked status if(checked == true) { /*$("input:checked").each(function() { selected.push($(this).attr('name')+"="+$(this).val(); }); alert(selected)*/ getQuery = $(this).attr('name')+"="+$(this).val()+"&location_submit=Next"; $.ajax({ type:"POST", url:"/search/location", data: getQuery, success:function(data){ alert(getQuery); console.log(data); // $('body.secEmp').html(data); } }); } else { //do something to remove the content here alert("Remove"); } });

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• In mysql, is "explain ..." always safe?

  - by tye

  If I allow a group of users to submit "explain $whatever" to mysql (via Perl's DBI using DBD::mysql), is there anything that a user could put into $whatever that would make any database changes, leak non-trivial information, or even cause significant database load? If so, how? I know that via "explain $whatever" one can figure out what tables / columns exist (you have to guess names, though) and roughly how many records are in a table or how many records have a particular value for an indexed field. I don't expect one to be able to get any information about the contents of unindexed fields. DBD::mysql should not allow multiple statements so I don't expect it to be possible to run any query (just explain one query). Even subqueries should not be executed, just explained. But I'm not a mysql expert and there are surely features of mysql that I'm not even aware of. In trying to come up with a query plan, might the optimizer actual execute an expression in order to come up with the value that an indexed field is going to be compared against? explain select * from atable where class = somefunction(...) where atable.class is indexed and not unique and class='unused' would find no records but class='common' would find a million records. Might 'explain' evaluate somefunction(...)? And then could somefunction(...) be written such that it modifies data?

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• Semi-generic function

  - by Fredrik Ullner

  I have a bunch of overloaded functions that operate on certain data types such as int, double and strings. Most of these functions perform the same action, where only a specific set of data types are allowed. That means I cannot create a simple generic template function as I lose type safety (and potentially incurring a run-time problem for validation within the function). Is it possible to create a "semi-generic compile time type safe function"? If so, how? If not, is this something that will come up in C++0x? An (non-valid) idea; template <typename T, restrict: int, std::string > void foo(T bar); ... foo((int)0); // OK foo((std::string)"foobar"); // OK foo((double)0.0); // Compile Error Note: I realize I could create a class that has overloaded constructors and assignment operators and pass a variable of that class instead to the function.

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• How should I define a JavaScript 'namespace' to satisfy JSLint?

  - by Matthew Murdoch

  I want to be able to package my JavaScript code into a 'namespace' to prevent name clashes with other libraries. Since the declaration of a namespace should be a simple piece of code I don't want to depend on any external libraries to provide me with this functionality. I've found various pieces of advice on how to do this simply but none seem to be free of errors when run through JSLint (using 'The Good Parts' options). As an example, I tried this from Advanced JavaScript (section Namespaces without YUI): "use strict"; if (typeof(MyNamespace) === 'undefined') { MyNamespace = {}; } Running this through JSLint gives the following errors: Problem at line 2 character 12: 'MyNamespace' is not defined. Problem at line 3 character 5: 'MyNamespace' is not defined. Implied global: MyNamespace 2,3 The 'Implied global' error can be fixed by explicitly declaring MyNamespace... "use strict"; if (typeof(MyNamespace) === 'undefined') { var MyNamespace = {}; } ...and the other two errors can be fixed by declaring the variable outside the if block. "use strict"; var MyNamespace; if (typeof(MyNamespace) === 'undefined') { MyNamespace = {}; } So that works, but it seems to me that (since MyNamespace will always be undefined at the point it is checked?) it is equivalent to the much simpler: "use strict"; var MyNamespace = {}; JSLint is content with this but I'm concerned that I've simplified the code to such an extent that it will no longer function correctly as a namespace. Is this final formulation sensible?

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• Are there equivalents to Ruby's method_missing in other languages?

  - by Justin Ethier

  In Ruby, objects have a handy method called method_missing which allows one to handle method calls for methods that have not even been (explicitly) defined: Invoked by Ruby when obj is sent a message it cannot handle. symbol is the symbol for the method called, and args are any arguments that were passed to it. By default, the interpreter raises an error when this method is called. However, it is possible to override the method to provide more dynamic behavior. The example below creates a class Roman, which responds to methods with names consisting of roman numerals, returning the corresponding integer values. class Roman def romanToInt(str) # ... end def method_missing(methId) str = methId.id2name romanToInt(str) end end r = Roman.new r.iv #=> 4 r.xxiii #=> 23 r.mm #=> 2000 For example, Ruby on Rails uses this to allow calls to methods such as find_by_my_column_name. My question is, what other languages support an equivalent to method_missing, and how do you implement the equivalent in your code?

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• Path String Concatenation Question.

  - by Nano HE

  Hi. Please see my code below. ifstream myLibFile ("libs//%s" , line); // Compile failed here ??? I want to combine the path string and open the related file again. #include <iostream> #include <fstream> #include <string> using namespace std; int main () { string line; ifstream myfile ("libs//Config.txt"); // There are several file names listed in the COnfig.txt file line by line. if (myfile.is_open()) { while (! myfile.eof() ) { getline (myfile,line); cout << line << endl; // Read details lib files based on the each line file name. string libFileLine; ifstream myLibFile ("libs//%s" , line); // Compile failed here ??? if (myLibFile.is_open()) { while (! myLibFile.eof() ) { cout<< "success\n"; } myLibFile.close(); } } myfile.close(); } else cout << "Unable to open file"; return 0; } Assume my [Config.txt] include the content below. And all the *.txt files located in libs folder. file1.txt file2.txt file3.txt

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• How to provide a temporary URL for custom domain in Wordpress multisite install?

  - by Milan Babuškov

  I have a website with Wordpress 3.0.4 installation, set up as multisite install. Some users register their blogs as something.mydomain.com and that works automatically. However, some users prefer to use their own domain names like something.com. This also works fine once they set up the CNAME record to point to my server. However, it takes 24-48 hours for that change to take effect. I'd like to be able to offer the user a temporary URL that would work out-of-the-box until the DNS changes are propagated, but I have not idea how to do it? For example: something.com should also be accessible as: something.tempdomain.com I have control over "tempdomain" DNS setup. I thought about replacing $_SERVER variables in index.php or .htaccess file when temporary domain is accessed, and this works for the first page load. However, all the links in generated page point to original domain which is not yet ready. UPDATE: I managed to get it working for the site itself by manipulating $_SERVER variables so Wordpress thinks it's creating a page for different site. I did this in index.php, so before any WP code is run I'm using ob_start and ob_get_contents later to get the page generated by Wordpress and then str_replace the links back to temporary domain. The problem I still have is the admin page. Even though the link says: http://site1.tempdomain.com/wp-admin when opened in browser it redirects to maindomain.com/wp-signup.php?new=site1.tempdomain I don't understand how WP detects that I supplied "fake" domain when $_SERVER vars are changed?

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• User will input some filter criteria -- how can I turn it into a regular expression for String.match

  - by envinyater

  I have a program where the user will enter a string such as PropertyA = "abc_*" and I need to have the asterisk match any character. In my code, I'm grabbing the property value and replacing PropertyA with the actual value. For instance, it could be abc_123. I also pull out the equality symbol into a variable. It should be able to cover this type of criteria PropertyB = 'cba' PropertyC != '*-this' valueFromHeader is the lefthand side and value is the righthand side. if (equality.equals("=")) { result = valueFromHeader.matches(value); } else if (equality.equals("!=")) { result = !valueFromHeader.matches(value); } EDIT: The existing code had this type of replacement for regular expressions final String ESC = "\\$1"; final String NON_ALPHA = "([^A-Za-z0-9@])"; final String WILD = "*"; final String WILD_RE_TEMP = "@"; final String WILD_RE = ".*"; value = value.replace(WILD, WILD_RE_TEMP); value = value.replaceAll(NON_ALPHA,ESC); value = value.replace(WILD_RE_TEMP, WILD_RE); It doesn't like the underscore here... abcSite_123 != abcSite_123 (evaluates to true) abcSite_123$1.matches("abcSite$1123") It doesn't like the underscore...

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• problem with phpMyAdmin advanced features

  - by typoknig

  Hi all, I am having trouble putting the final touches on my MySQL/Apache/phpMyAdmin install on a Windows XP system. I am trying to get rid of all the error message in phpMyAdmin and I have gotten rid of all of them except the ones related to "advanced features." The exact error message I have is : The additional features for working with linked tables have been deactivated. To find out why click here. I have read up on the cause of the errors but I must be missing something because I still cannot get the warning to go away. Here is what I have done: Created a linked-tables infrastructure (default name "phpmyadmin") per the phpMyAdmin instructions and enabled "pmadb" in my "config.inc.php" file. Specified (enabled) the table names in my "config.inc.php" file (there are 9 tables total). Created a "controluser" and granted only Select privilages per phpMyAdmin instructions Adjusted "controluser" pma and "controlpass" pmapass in "config.inc.php" file From what I can see these are all the instruction phpMyAdmin gives on this subject, and I am unable to locate any tutorials on the specifics of "advanced features" in phpMyAdmin. Any help would be appreciated, and be gentle, this is my first go with MySQL/phpMyAdmin

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• Bad idea to have the same object, have a different side effect after method call.

  - by Nathan W

  Hi all, I'm having a bit of a gesign issue(again). Say I have this Buttonpad object: now this object is a wrapper object over one in a com object. At the moment it has a method on it called CreateInto(IComObject). Now to make a new button pad in the Com Object. You do: ButtonPad pad = new ButtonPad(); pad.Title = "Hello"; // Set some more properties. pad.CreateInto(Cominstance); The createinfo method will excute the right commands to buid the button pad in the com object. After it has been created it any calls against it are foward to the underlying object for change so: pad.Title = "New title"; will call the com object to set the title and also set the internal title variable. Basically any calls before the CreateInfo method only affect the .NET object anything after has the side effect of calling the com object also. I'm not very good at sequence diagrams but here is my attempt to explain whats going on: This doesn't feel good to me, it feels like I'm lying to the user about what the button pad does. I was going to have a object called WrappedButtonPad, which is returned from CreateInto and the user could make calls against that to make changes to the Com Object, but I feel having two objects that almost do the same thing but only differ by names might be even worse. Are these valid designs, or am I right to be worried? How else would you handle a object the can create and query a com object?

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• PHP hashing function not working properly

  - by Jordan Foreman

  So I read a quick PHP login system securing article, and was trying to sort of duplicate their hashing method, and during testing, am not getting the proper output. Here is my code: function decryptPassword($pw, $salt){ $hash = hash('sha256', $salt . hash('sha256', $pw)); return $hash; } function encryptPassword($pw){ $hash = hash('sha256', $pw); $salt = substr(md5(uniqid(rand(), true)), 0, 3); $hash = hash('sha265', $salt . $hash); return array( 'salt' => $salt, 'hash' => $hash ); } And here is my testing code: $pw = $_GET['pw']; $enc = encryptPassword($pw); $hash = $enc['hash']; $salt = $enc['salt']; echo 'Pass: ' . $pw . '<br />'; echo 'Hash: ' . $hash . '<br />'; echo 'Salt: ' . $salt . '<br />'; echo 'Decrypt: ' . decryptPassword($hash, $salt); Now, the output of this should be pretty obvious, but unfortunately, the $hash variable always comes out empty! I'm trying to figure out what the problem could be, and my only guess would be the second $hash assignment line in the encryptPassword(..) function. After a little testing, I've determined that the first assignment works smoothly, but the second does not. Any suggestions? Thanks SO!

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• Python: problem with tiny script to delete files

  - by Rosarch

  I have a project that used to be under SVN, but now I'm moving it to Mercurial, so I want to clear out all the .svn files. It's a little too big to do it by hand, so I decided to write a python script to do it. But it isn't working. def cleandir(dir_path): print "Cleaning %s\n" % dir_path toDelete = [] files = os.listdir(dir_path) for filedir in files: print "considering %s" % filedir # continue if filedir == '.' or filedir == '..': print "skipping %s" % filedir continue path = dir_path + os.sep + filedir if os.path.isdir(path): cleandir(path) else: print "not dir: %s" % path if 'svn' in filedir: toDelete.append(path) print "Files to be deleted:" for candidate in toDelete: print candidate print "Delete all? [y|n]" choice = raw_input() if choice == 'y': for filedir in toDelete: if os.path.isdir(filedir): os.rmdir(filedir) else: os.unlink(filedir) exit() if __name__ == "__main__": cleandir(dir) The print statements show that it's only "considering" the filedirs whose names start with ".". However, if I uncomment the continue statement, all the filedirs are "considered". Why is this? Or is there some other utility that already exists to recursively de-SVN-ify a directory tree?

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• How to use a rewrite rule to force calls for "domain.tld/subdir/file.html" to show as "subdir.domain.tld/file.html"?

  - by Wion

  Hi! First time poster. Very new to mod_rewrite. I'm on a shared server and the context of this problem is with a virtual directory under my root account. The domain (domain.tld) will have subdirectories representing annual mini-sites of static .html files. Subdirectory names (yyyy) will be the 4-digit year (e.g., "2010"). I want any call to domain.tld/yyyy/file.html to appear as yyyy.domain.tld/file.html in the browser address bar, and (of course) for the page to load properly. I already force dropping “www” by using… RewriteCond %{HTTP_HOST} ^www\.domain\.tld [NC] RewriteRule (.*) http://domain.tld/$1 [R=301,L] So far so good. But no matter what I try after that, I can’t get the subdomain to force to the front of the domain. Here’s one of the more complicated examples I’ve tried (no doubt wrong)… RewriteCond %{HTTP_HOST} ^domain\.tld/([0-9]+)/([a-z-]+)\.html [NC] RewriteRule (.*) %1.domain.tld/%2.html [NC] This doesn’t break anything (that I can tell), but it doesn’t do what I want either. I.e., if I type yyyy.domain.tld, I’ll see yyyy.domain.tld in the address bar, and navigating around will give me yyyy.domain.tld/file.html, etc. Fine. But if also type domain.tld/yyyy I’ll see domain.tld/yyyy, etc, which is not how I want people to see it. It doesn’t redirect or mask or alias or whatever you call it. Is it even possible to force one look over the other like that? Should I be handling this with DNS instead? Thanks in advance!

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• Hibernate: fetching multiple bags efficiently

  - by Jens Jansson

  Hi! I'm developing a multilingual application. For this reason many objects have in their name and description fields collections of something I call LocalizedStrings instead of plain strings. Every LocalizedString is basically a pair of a locale and a string localized to that locale. Let's take an example an entity, let's say a book -object. public class Book{ @OneToMany private List<LocalizedString> names; @OneToMany private List<LocalizedString> description; //and so on... } When a user asks for a list of books, it does a query to get all the books, fetches the name and description of every book in the locale the user has selected to run the app in, and displays it back to the user. This works but it is a major performance issue. For the moment hibernate makes one query to fetch all the books, and after that it goes through every single object and asks hibernate for the localized strings for that specific object, resulting in a "n+1 select problem". Fetching a list of 50 entities produces about 6000 rows of sql commands in my server log. I tried making the collections eager but that lead me to the "cannot simultaneously fetch multiple bags"-issue. Then I tried setting the fetch strategy on the collections to subselect, hoping that it would do one query for all books, and after that do one query that fetches all LocalizedStrings for all the books. Subselects didn't work in this case how i would have hoped and it basically just did exactly the same as my first case. I'm starting to run out of ideas on how to optimize this. So in short, what fetching strategy alternatives are there when you are fetching a collection and every element in that collection has one or multiple collections in itself, which has to be fetch simultaneously.

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• Element Content Versus Attribute for Simple XML Value

  - by MB

  I know the elements versus attributes debate has come up many times here and elsewhere (e.g. here, here, here, here, and here) but I haven't seen much discussion of elements versus attributes for simple property values. So which of the following approaches do you think is better for storing a simple value? A: Value in Element Content: <TotalCount>553</TotalCount> <CelsiusTemperature>23.5</CelsiusTemperature> <SingleDayPeriod>2010-05-29</SingleDayPeriod> <ZipCodeLocation>12203</ZipCodeLocation> or B: Value in Attribute: <TotalCount value="553"/> <CelsiusTemperature value="23.5"/> <SingleDayPeriod day="2010-05-29"/> <ZipCodeLocation code="12203"/> I suspect that putting the value in the element content (A) might look a little more familiar to most folks (though I'm not sure about that). Putting the value in an attribute (B) might use less characters, but that depends on the length of the element and attribute names. Putting the value in an attribute (B) might be more extensible, because you could potentially include all sorts of extra information as nested elements. Whereas, by putting the value inside the element content (A), you're restricting extensibility to adding more attributes. But then extensibility often isn't a concern for really simple properties - sometimes you know that you'll never need to add additional data. Bottom line might be that it simply doesn't matter, but it would still be great to hear some thoughts and see some votes for the two options.

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• Why does this Haskell code produce the "infinite type" error?

  - by Charlie Flowers

  I am new to Haskell and facing a "cannot construct infinite type" error that I cannot make sense of. In fact, beyond that, I have not been able to find a good explanation of what this error even means, so if you could go beyond my basic question and explain the "infinite type" error, I'd really appreciate it. Here's the code: intersperse :: a -> [[a]] -> [a] -- intersperse '*' ["foo","bar","baz","quux"] -- should produce the following: -- "foo*bar*baz*quux" -- intersperse -99 [ [1,2,3],[4,5,6],[7,8,9]] -- should produce the following: -- [1,2,3,-99,4,5,6,-99,7,8,9] intersperse _ [] = [] intersperse _ [x] = x intersperse s (x:y:xs) = x:s:y:intersperse s xs And here's the error trying to load it into the interpreter: Prelude :load ./chapter.3.ending.real.world.haskell.exercises.hs [1 of 1] Compiling Main ( chapter.3.ending.real.world.haskell.exercises.hs, interpreted ) chapter.3.ending.real.world.haskell.exercises.hs:147:0: Occurs check: cannot construct the infinite type: a = [a] When generalising the type(s) for `intersperse' Failed, modules loaded: none. Thanks. EDIT: Thanks to the responses, I have corrected the code and I also have a general guideline for dealing with the "infinite type" error in Haskell: Corrected code intersperse _ [] = [] intersperse _ [x] = x intersperse s (x:xs) = x ++ s:intersperse s xs What the problem was: My type signature states that the second parameter to intersperse is a list of lists. Therefore, when I pattern matched against "s (x:y:xs)", x and y became lists. And yet I was treating x and y as elements, not lists. Guideline for dealing with the "infinite type" error: Most of the time, when you get this error, you have forgotten the types of the various variables you're dealing with, and you have attempted to use a variable as if it were some other type than what it is. Look carefully at what type everything is versus how you're using it, and this will usually uncover the problem.

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• When should we use private variables and when should we use properties.

  - by Shantanu Gupta

  In most of the cases we usually creates a private variable and its corresponding public properties and uses them for performing our functionalities. Everyone has different approach like some ppl uses properties every where and some uses private variables within a same class as they are private and opens it to be used by external environment by using properties. Suppose I takes a scenario say insertion in a database. I creates some parameters that need to be initialized. I creates 10 private variables and their corresp public properties which are given as private string name; public string Name { get{return name;} set{name=value;} } and so on. In these cases what should be used internally variables or properties. And in those cases like public string Name { get{return name;} set{name=value>5?5:0;} //or any action can be done. this is just an eg. } In such cases what should be done.

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• How to keep track of call statistics? C++

  - by tf.rz

  I'm working on a project that delivers statistics to the user. I created a class called Dog, And it has several functions. Speak, woof, run, fetch, etc. I want to have a function that spits out how many times each function has been called. I'm also interested in the constructor calls and destructor calls as well. I have a header file which defines all the functions, then a separate .cc file that implements them. My question is, is there a way to keep track of how many times each function is called? I have a function called print that will fetch the "statistics" and then output them to standard output. I was considering using static integers as part of the class itself, declaring several integers to keep track of those things. I know the compiler will create a copy of the integer and initialize it to a minimum value, and then I'll increment the integers in the .cc functions. I also thought about having static integers as a global variable in the .cc. Which way is easier? Or is there a better way to do this? Any help is greatly appreciated!

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