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• Some sonatype nexus questions.

  - by smallufo

  I deployed a sonatype nexus server inside my LAN , mapping some remote repositories to my public repositories : First question is , why these repositories not sync with the "real" repositories ? For example , I mapped maven central (http://repo1.maven.org/maven2) to "central" , but when I browse http://smallufo:8081/nexus/content/repositories/central/org/springframework/ , the packages are not complete , in http://repo2.maven.org/maven2/org/springframework/ , there are tons of artifacts , but I only have some of them : And versions are old ... ex : spring-core is only 2.5.6.SEC01 , but the latest version is 3.0.2.RELEASE. And my maven client seems can only find the old artifacts ... "central" is a proxy directory , it should be the same with the remote server. I tried to "Expire Cache" , "ReIndex" , "Incremental ReIndex" the whole "central" : After a long time with almost 100% java process load , the situation seems not better , just add some artifacts ... not reflecting the real "Maven Central" data... Second question , what's difference with "Expire Cache" , "ReIndex" , "Incremental ReIndex" ? Even I can "search" spring-core.3.0.2.RELEASE , my m2eclipse still cannot find it : I can also see the spring-core-3.0.2.RELEASE in the "index" , (but not available in "storage") : But why m2eclipse cannot make use of it ? it seems m2eclipse can only install artifacts in the storage , if this is how nexus works , how do I "force" download spring-core-3.0.2.RELEASE to nexus's storage ? How do I solve these strange incompatibilities ? Thanks a lot !

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• I want a insert query for a temp table

  - by John Stephen

  Hi..I am using C#.Net and Sql Server ( Windows Application ). I had created a temporary table. When a button is clicked, temporary table (#tmp_emp_answer) is created. I am having another button called "insert Values" and also 5 textboxes. The values that are entered in the textbox are used and whenever com.ExecuteNonQuery(); line comes, it throws an error message Invalid object name '#tbl_emp_answer'.. Below is the set of code.. Please give me a solution. Code for insert (in insert value button): private void btninsertvalues_Click(object sender, EventArgs e) { username = txtusername.Text; examloginid = txtexamloginid.Text; question = txtquestion.Text; answer = txtanswer.Text; useranswer = txtanswer.Text; SqlConnection con = new SqlConnection("Data Source=.;Initial Catalog=tempdb;Integrated Security=True;"); SqlCommand com = new SqlCommand("Insert into #tbl_emp_answer values('"+username+"','"+examloginid+"','"+question+"','"+answer+"','"+useranswer+"')", con); con.Open(); com.ExecuteNonQuery(); con.Close(); }

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• iPhone Development - calling external JSON API (will Apple reject?)

  - by RPM1984

  Ok guys, so im new to iPhone development, so apologies if this is a silly question, but before i actually create my app i want to know if this is possible, and if Apple will reject this. (Note this is all theoretical) So i'd have a API (.NET) that runs on a cloud server somewhere and can return HTML/JSON/XML. I'll have a website that can access this API and allow customers to do some stuff (but this is not important for this question). I would then like my iPhone app to make a call to this API which would return JSON data. So my iPhone app might make a call to http://myapp/Foos which would return a JSON string of Foo objects. The iPhone app would then parse this JSON and do some funky stuff with it. So, that's the background, now the questions: Is this possible? (that is, call an external cloud API over HTTP, parse JSON response?) What are the chances of Apple rejecting this application (because it would be calling a non-Apple API) Are there any limitations (security, libraries, etc) on the iPhone/Objective-C/Cocoa that might hinder this solution? On this website, they seem to be doing exactly what im asking. Thoughts, suggestions, links would be greatly appreciated...

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• DDD: Enum like entities

  - by Chris

  Hi all, I have the following DB model: **Person table** ID | Name | StateId ------------------------------ 1 Joe 1 2 Peter 1 3 John 2 **State table** ID | Desc ------------------------------ 1 Working 2 Vacation and domain model would be (simplified): public class Person { public int Id { get; } public string Name { get; set; } public State State { get; set; } } public class State { private int id; public string Name { get; set; } } The state might be used in the domain logic e.g.: if(person.State == State.Working) // some logic So from my understanding, the State acts like a value object which is used for domain logic checks. But it also needs to be present in the DB model to represent a clean ERM. So state might be extended to: public class State { private int id; public string Name { get; set; } public static State New {get {return new State([hardCodedIdHere?], [hardCodeNameHere?]);}} } But using this approach the name of the state would be hardcoded into the domain. Do you know what I mean? Is there a standard approach for such a thing? From my point of view what I am trying to do is using an object (which is persisted from the ERM design perspective) as a sort of value object within my domain. What do you think? Question update: Probably my question wasn't clear enough. What I need to know is, how I would use an entity (like the State example) that is stored in a database within my domain logic. To avoid things like: if(person.State.Id == State.Working.Id) // some logic or if(person.State.Id == WORKING_ID) // some logic

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• Can we run two simultaneous non-nested loops in Perl?

  - by Mike

  Part of my code goes like this: while(1){ my $winmm = new Win32::MediaPlayer; $winmm->load('1.mp3'); $winmm->play; $winmm->volume(100); Do Some Stuff; last if some condition is met; } Problem is: I want the music to be always on when I'm in the Do Some Stuff stage in the while loop. But the length of the music is so short that it will come to a full stop before I go to the next stage, so I want the music to repeat itself, but the Win32::Mediaplayer module does not seem to have a repeat mode, so I'm thinking of doing an infinite loop for the music playing part. Like this: while(1){ my $winmm = new Win32::MediaPlayer; $winmm->load('1.mp3'); $winmm->play; $winmm->volume(100); } while(2){ Do some stuff; last if some condition is met } But based on my current Perl knowledge if I'm in the while(1) part, I can never go to the while(2) part. Even if it comes to a nested loop, I have to do something to break out of the inside loop before going to the other part of the outside loop. The answer to my question "Can we run two simultaneous non-nested loops in Perl?" may be a NO, but I assume there is some way of handling such situation. Correct me if I'm wrong. Thanks as always for any comments/suggestions :) UPDATE I really appreciate the help from everyone. Thanks :) So the answer to my question is a YES, not a NO. I'm happy that I've learned how to use fork() and threads to solve a real problem :)

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• How can I create global context variables in JBOSS?

  - by NobodyMan

  This is a follow-up to a question I posted a while back: "Can I use a single WAR in multiple environments?". I was able to create a single-war solution in Tomcat, but now we are migrating our app to JBoss 4.2 and I can't figure out how to set up global environment variables. In Tomcat 6 this was pretty straightforward: I simply put the following snippet in tomcat/conf/Catalina/myappname.xml: <Context ...> <Environment name="TARGET_ENV" value="DEV" type="java.lang.String" override="false"/> </Context> Then in my app I was able to resolve the environment name with the following: Context context = (Context) InitialContext().lookup("java:comp/env"); String targetEnvironment = (String) context.lookup("TARGET_ENV"); The problem is that I can't find out where/how to place global variables in JBoss. I've tried putting the <Environment> tag in the following files to no avail: server/all/deploy/jboss-web.deployer/context.xml server/default/deploy/jboss-web.deployer/context.xml I know that I can put environment variables in my app's web.xml but that defeats the purpose of having a unified war - I'd still need custom .war's for dev, qa and prod. I'm a JBoss newbie so if there's any additional information that would help just let me know and I'll append to this question. Many thanks! --N

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• I don't like Python functions that take two or more iterables. Is it a good idea?

  - by Xavier Ho

  This question came from looking at this question on Stackoverflow. def fringe8((px, py), (x1, y1, x2, y2)): Personally, it's been one of my pet peeves to see a function that takes two arguments with fixed-number iterables (like a tuple) or two or more dictionaries (Like in the Shotgun API). It's just hard to use, because of all the verbosity and double-bracketed enclosures. Wouldn't this be better: >>> class Point(object): ... def __init__(self, x, y): ... self.x = x ... self.y = y ... >>> class Rect(object): ... def __init__(self, x1, y1, x2, y2): ... self.x1 = x1 ... self.y1 = y1 ... self.x2 = x2 ... self.y2 = y2 ... >>> def fringe8(point, rect): ... # ... ... >>> >>> point = Point(2, 2) >>> rect = Rect(1, 1, 3, 3) >>> >>> fringe8(point, rect) Is there a situation where taking two or more iterable arguments is justified? Obviously the standard itertools Python library needs that, but I can't see it being pretty in maintainable, flexible code design.

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• Selecting a form which is in an iframe using jQuery

  - by Khnle

  I have a form inside an iframe which is inside a jQuery UI dialog box. The form contains a file input type. The jQuery UI dialog contains an Upload button. When this button is clicked, I would like to programmatically call the submit method. My question is how I could select the form which is in a iframe using jQuery. The following code should clarify the picture: <div id="upload_file_picker_dlg" title="Upload file"> <iframe id="upload_file_iframe" src="/frame_src_url" frameborder=0 width=100% scrolling=no></iframe> </div> frame_src_url contains: <form action="/UploadTaxTable" enctype="multipart/form-data" method="post" id="upload-form"> <p>Select a file to be uploaded:</p> <p> <input type="file" name="datafile" size="60"> </p> The jQueryUI dialog box javascript code: $('#upload_file_picker_dlg').dialog({ ... buttons: { 'Close': function() { $(this).dialog('close'); }, 'Upload': function() { $('#upload-form').submit(); //question is related to this line $(this).dialog('close'); } }, .... }); From the javascript code snippet above, how can I select the form with id upload-form that is in the iframe whose id is upload_file_iframe ?

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• How do I use an index in an array reference as a method reference in Perl?

  - by Robert P

  Similar to this question about iterating over subroutine references, and as a result of answering this question about a OO dispatch table, I was wondering how to call a method reference inside a reference, without removing it first, or if it was even possible. For example: package Class::Foo; use 5.012; #Yay autostrict! use warnings; # a basic constructor for illustration purposes.... sub new { my $class = shift; return bless {}, $class; } # some subroutines for flavor... sub sub1 { say 'in sub 1' } sub sub2 { say 'in sub 2' } sub sub3 { say 'in sub 3' } # and a way to dynamically load the tests we're running... sub sublist { my $self = shift; return [ $self->can('sub1'); $self->can('sub3'}; $self->can('sub2'); ]; } package main; my $instance = Class::Foo->new(a => 1, b => 2, c => 3); my $tests = $instance->sublist(); my $index = int(rand($#{$tests})); # <-- HERE So, at HERE, we could do: my $ref = $tests->{$index}; $instance->$ref(); but how would we do this, without removing the reference first?

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• Updating an image's ImageUrl within a Repeater

  - by Django Reinhardt

  I hope someone can help me. It's a pretty newbie question, I'm afraid. I have an image inside a repeater, and I would like to change its IMAGEURL based on parameter that's being passed to it. <asp:Repeater ID="Repeater" runat="server"> <HeaderTemplate> <asp:Image ID="imgType" runat="server" /> </HeaderTemplate> <ItemTemplate> <%# Eval("DisplayName")%> </ItemTemplate> <SeparatorTemplate> <hr /> </SeparatorTemplate> </asp:Repeater> There is a SWITCH statement in the code behind that is altering the IMAGEURL depending on what's being passed to it. Inevitably, however, the images ID ("imgType") is not visible to the SWITCH statement (presumably because it's inside a REPEATER). Any suggestions on the best way to implement this would be greatly appreciated. Sorry for such a newbie question.

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• php convert european datetime to mysql datetime

  - by Mathlight

  I'm really stuck with this problem. I've got an datetime string like this: 28-06-14 11:01:00 I'm trying to convert it to 2014-06-28 11:01:00 so that i can insert it into the database ( with field type datetime. I've tryed multiple things like this: $datumHolder = new DateTime($data['datum'], new DateTimeZone('Europe/Amsterdam')); $datum1 = $datumHolder -> format("Y-m-d H:i:s"); $datum2 = date( 'Y-m-d', strtotime(str_replace('-', '/', $data['datum']) ) ); $datum3 = DateTime::createFromFormat( 'Y-m-d-:Hi:s', $data['datum']); This is the output i get: datum1: 2028-06-14 11:01:00 datum2: 1970-01-01 And i get an error for datum3: echo "datum3: " . $datum3->format( 'Y-m-d H:i:s'); . '<br />'; Call to a member function format() on a non-object So my question is very clear... What am I doing wrong / how to get this working? Thanks in advantage guys! I know that this question is asked many, many times... But whatever i try, i can't get it working...

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• How can variadic char template arguments from user defined literals be converted back into numeric types?

  - by Pubby

  This question is being asked because of this one. C++11 allows you to define literals like this for numeric literals: template<char...> OutputType operator "" _suffix(); Which means that 503_suffix would become <'5','0','3'> This is nice, although it isn't very useful in the form it's in. How can I transform this back into a numeric type? This would turn <'5','0','3'> into a constexpr 503. Additionally, it must also work on floating point literals. <'5','.','3> would turn into int 5 or float 5.3 A partial solution was found in the previous question, but it doesn't work on non-integers: template <typename t> constexpr t pow(t base, int exp) { return (exp > 0) ? base * pow(base, exp-1) : 1; }; template <char...> struct literal; template <> struct literal<> { static const unsigned int to_int = 0; }; template <char c, char ...cv> struct literal<c, cv...> { static const unsigned int to_int = (c - '0') * pow(10, sizeof...(cv)) + literal<cv...>::to_int; }; // use: literal<...>::to_int // literal<'1','.','5'>::to_int doesn't work // literal<'1','.','5'>::to_float not implemented

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• fix needed for bug in TextField/Text

  - by Mark

  Sort of a complicated scenario - just curious if anyone else could come up with something: I have a Text control and when I scroll it and stop the scroll with the cursor over some text that has a url, the cursor doesn't revert to a hand, and also flash player starts acting as if a selection is being made from the last cursor position. So IOW a bonafide bug in flash as far as I can determine. The above probably wasn't completely clear so let me elaborate. If you grab a scrollbar thumb and start moving it up and down, you don't actually have to keep the mouse pointer on the thumb while doing so. When you stop the scroll, the mouse pointer could be outside the browser window, inside your flash application, but not currently on the scroll bar thumb, or wherever. The previously mentioned bug occurs when you stop the scroll with the mouse pointer positioned over text with an html anchor (a hyperlink). At that point the cursor enters into some state of limbo, and doesn't show the url hand pointer, and furthermore acts as if some text selection is taking place from the last cursor position prior to the scroll. So the question would be, what sort of event could I simulate in code to jolt flash out of this erroneous state it is in. And furthermore in what event could I perform this simulated event (given that for example there is no AS3 event to signal the end of a scroll.) To be clear, the Text control in question is on a canvas, and that canvas (call it A) is on another canvas which actually owns the scrollbar, and scrolling takes place by changing the scrollRect of canvas A.

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• Is boost shared_ptr <XXX> thread safe?

  - by sxingfeng

  I have a question about boost :: shared_ptr. There are lots of thread. class CResource { xxxxxx } class CResourceBase { public: void SetResource(shared_ptr<CResource> res) { m_Res = res; } shared_ptr<CResource> GetResource() { return m_Res; } private: shared_ptr<CResource> m_Res; } CResourceBase base; //---------------------------------------------- Thread A: while (true) { ...... shared_ptr<CResource> nowResource = base.GetResource(); nowResource.doSomeThing(); ... } Thread B: shared_ptr<CResource> nowResource; base.SetResource(nowResource); ... //----------------------------------------------------------- If thread A do not care the nowResource is the newest . Will this part of code have problem? I mean when ThreadB do not SetResource completely, Thread A get a wrong smart point by GetResource? Another question : what does thread-safe mean? If I do not care about whether the resource is newest, will the shared_ptr nowResource crash the program when the nowResource is released or will the problem destroy the shared_point?

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• Convert charset in mysql query

  - by Yousf

  Hi, I have a question about converting charset from inside mysql query. I have a 2 databases. One for the website (joomla), the other for forum (IPB). I am doing query from inside joomla, which by default have "SET NAMES UTF8". I want to query a table inside the forum databases. A table called "ibf_topics". This table has latin1 encoding. I do the following to select anything from the not-utf8 table. //convert connection to handle latin1. $query = "SET NAMES latin1"; $db->setQuery($query); $db->query(); $query = "select id, title from other_database.ibf_topics"; $db->setQuery($query); $db->query(); //read result into an array. //return connection to handle UTF8. $query = "SET NAMES UTF8"; $db->setQuery($query); $db->query(); After that, when I want to use the selected tile, I use the following: echo iconv("CP1256", "UTF-8", $topic['title']) The question is, is there anyway to avoid all this hassle? For now, I can't change forum database to UTF8 and I can't change joomla database to latin1 :S

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• In which year was the date the same as the original year?

  - by Marta

  It's my first question on this site, but I always found this site really useful. What I mean with my question is: you ask the person to give a date (eg. Fill in a date [dd-mm-yyyy]: 16-10-2013) you than have to ask an interval between 2 years (eg. Give an interval [yyyy-yyyy]:1800-2000) When the program runs, it has to show what day of the week the given date is. In this case it was a Wednesday. Than the program has to look in which year, in between the interval, the date 16 October also fell on a Wednesday. So in the end it has to look something like this: Fill in a date: [dd-mm-yyyy]: 16-10-2013 Give an interval [yyyy-yyyy]: 1900-2000 16 October was a wednesday in the following years: 1905 1911 1916 1922 1933 1939 1944 1950 1961 1967 1972 1978 1989 1995 2000 The full date is Wednesday 16 October, 2013 The small (or biggest) problem is, I am not allowed to use the DATE.function in java. If someone can help me with the second part I would be really really happy, cause I have no idea how I am supposed to do this To find out what day of the week the given date falls, I use the Zeller Congruence class Day { Date date; //To grab the month and year form the Date class int day; final static String[] DAYS_OF_WEEK = { "Saturday", "Sunday", "Monday", "Tuesday", "Wednesday", "Thursday", "Friday" }; public void dayWeekInterval{ //code to grab the interval from interval Class, and doing stuff here } public void dayOfTheWeek { int m = date.getMonth(); int y = date.getYear(); if (m < 3) { m += 12; y -= 1; } int k = y % 100; int j = y / 100; int day = ((q + (((m + 1) * 26) / 10) + k + (k / 4) + (j / 4)) + (5 * j)) % 7; return day; } public string ToString(){ return "" + DAYS_OF_WEEK[day] + day; } }

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• Unable to save data in database manually and get latest auto increment id, cakePHP

  - by shabby

  I have checked this question as well and this one as well. I am trying to implement the model described in this question. What I want to do is, on the add function of message controller, create a record in thread table(this table only has 1 field which is primary key and auto increment), then take its id and insert it in the message table along with the user id which i already have, and then save it in message_read_state and thread_participant table. This is what I am trying to do in Thread Model: function saveThreadAndGetId(){ //$data= array('Thread' => array()); $data= array('id' => ' '); //Debugger::dump(print_r($data)); $this->save($data); debug('id: '.$this->id); $threadId = $this->getInsertID(); debug($threadId); $threadId = $this->getLastInsertId(); debug($threadId); die(); return $threadId; } $data= array('id' => ' '); This line from the above function adds a row in the thread table, but i am unable to retrieve the id. Is there any way I can get the id, or am I saving it wrongly? Initially I was doing the query thing in the message controller: $this->Thread->query('INSERT INTO threads VALUES();'); but then i found out that lastId function doesnt work on manual queries so i reverted.

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• Heroku: Postgres type operator error after migrating DB from MySQL

  - by sevennineteen

  This is a follow-up to a question I'd asked earlier which phrased this as more of a programming problem than a database problem. http://stackoverflow.com/questions/2935985/postgres-error-with-sinatra-haml-datamapper-on-heroku I believe the problem has been isolated to the storage of the ID column in Heroku's Postgres database after running db:push. In short, my app runs properly on my original MySQL database, but throws Postgres errors on Heroku when executing any query on the ID column, which seems to have been stored in Postgres as TEXT even though it is stored as INT in MySQL. My question is why the ID column is being created as INT in Postgres on the data transfer to Heroku, and whether there's any way for me to prevent this. Here's the output from a heroku console session which demonstrates the issue: Ruby console for myapp.heroku.com >> Post.first.title => "Welcome to First!" >> Post.first.title.class => String >> Post.first.id => 1 >> Post.first.id.class => Fixnum >> Post[1] PostgresError: ERROR: operator does not exist: text = integer LINE 1: ...", "title", "created_at" FROM "posts" WHERE ("id" = 1) ORDER... ^ HINT: No operator matches the given name and argument type(s). You might need to add explicit type casts. Query: SELECT "id", "name", "email", "url", "title", "created_at" FROM "posts" WHERE ("id" = 1) ORDER BY "id" LIMIT 1 Thanks!

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• Does the pointer to free() have to point to beginning of the memory block, or can it point to the interior?

  - by Lambert

  The question is in the title... I searched but couldn't find anything. Edit: I don't really see any need to explain this, but because people think that what I'm saying makes no sense (and that I'm asking the wrong questions), here's the problem: Since people seem to be very interested in the "root" cause of all the problem rather than the actual question asked (since that apparently helps things get solved better, let's see if it does), here's the problem: I'm trying to make a D runtime library based on NTDLL.dll, so that I can use that library for subsystems other than the Win32 subsystem. So that forces me to only link with NTDLL.dll. Yes, I'm aware that the functions are "undocumented" and could change at any time (even though I'd bet a hundred dollars that wcstombs will still do the same exact thing 20 years from now, if it still exists). Yes, I know people (especially Microsoft) don't like developers linking to that library, and that I'll probably get criticized for the right here. And yes, those two points above mean that programs like chkdsk and defragmenters that run before the Win32 subsystem aren't even supposed to be created in the first place, because it's literally impossible to link with anything like kernel32.dll or msvcrt.dll and still have NT-native executables, so we developers should just pretend that those stages are meant to be forever out of our reaches. But no, I doubt that anyone here would like me to paste a few thousand lines of code and help me look through them and try to figure out why memory allocations that aren't failing are being rejected by the source code I'm modifying. So that's why I asked about a different problem than the "root" cause, even though that's supposedly known to be the best practice by the community. If things still don't make sense, feel free to post comments below! :)

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• Accessing program information that gdb sees in C++

  - by anon

  I have a program written in C++, on Linux, compiled with -g. When I run it under gdb, I can 1) set breakpoints 2) at those breakpoints, print out variables 3) see the stackframe 4) given a variable that's a structure, print out parts of the structure (i.e. how ddd displays information). Now, given that my program is compiled with "-g" -- is there anyway that I can access this power within my program itself? I.e. given that my program is compiled with "-g", is there some std::vector<string> getStackFrame(); function I can call to get the current stackframe at the current point of execution? Given a pointer to an object and it's type ... can I do std::vector getClassMember(class_name); ? I realize the default answer is "no, C++ doesn't support that level of introspection" -- however, recall I'm on linux, my program is compiled with "-g", and gdb can do it, so clearly the inforamtion is there. Question is: is there some API for accessing it? EDIT: PS Naysers, I'd love to see a reason for closing this question.

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• Is it possible to spoof or reuse VIEWSTATE or detect if it is protected from modification?

  - by Peter Jaric

  Question ASP and ASP.NET web applications use a value called VIEWSTATE in forms. From what I understand, this is used to persist some kind of state on the client between requests to the web server. I have never worked with ASP or ASP.NET and need some help with two questions (and some sub-questions): 1) Is it possible to programmatically spoof/construct a VIEWSTATE for a form? Clarification: can a program look at a form and from that construct the contents of the base64-encoded VIEWSTATE value? 1 a) Or can it always just be left out? 1 b) Can an old VIEWSTATE for a particular form be reused in a later invocation of the same form, or would it just be luck if that worked? 2) I gather from http://msdn.microsoft.com/en-us/library/ms972976.aspx#viewstate_topic12 that it is possible to turn on security so that the VIEWSTATE becomes secure from spoofing. Is it possible for a program to detect that a VIEWSTATE is safeguarded in such a way? 2 a) Is there a one-to-one mapping between the occurrence of EVENTVALIDATION values and secure VIEWSTATEs? Regarding 1) and 2), if yes, can I have a hint about how I would do that? For 2) I am thinking I could base64-decode the value and search for a string that always is found in unencrypted VIEWSTATEs. "First:"? Something else? Background I have made a small tool for detecting and exploiting so called CSRF vulnerabilities. I use it to quickly make proof of concepts of such vulnerabilities that I send to the affected site owners. Quite often I encounter these forms with a VIEWSTATE, and these I don't know if they are secure or not. Edit 1: Clarified question 1 somewhat. Edit 2: Added text in italics.

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• Message Handlers and the WeakReference issue

  - by user1058647

  The following message Handler works fine receiving messages from my service... private Handler handler = new Handler() { public void handleMessage(Message message) { Object path = message.obj; if (message.arg1 == 5 && path != null) //5 means its a single mapleg to plot on the map { String myString = (String) message.obj; Gson gson = new Gson(); MapPlot mapleg = gson.fromJson(myString, MapPlot.class); myMapView.getOverlays().add(new DirectionPathOverlay(mapleg.fromPoint, mapleg.toPoint)); mc.animateTo(mapleg.toPoint); } else { if (message.arg1 == RESULT_OK && path != null) { Toast.makeText(PSActivity.this, "Service Started" + path.toString(), Toast.LENGTH_LONG).show(); } else { Toast.makeText(PSActivity.this,"Service error" + String.valueOf(message.arg1), Toast.LENGTH_LONG).show(); } } }; }; However, even though it tests out alright in the AVD (I'm feeding it a large KML file via DDMS) the "object path = message.obj;" line has a WARNING saying "this Handler class should be static else leaks might occur". But if I say "static Handler handler = new Handler()" it won't compile complaining that I "cannot make a static reference to a non-static field myMapView. If I can't make such references, I can't do anything useful. This led me into several hours of googling around on this issue and learning more about weakReferences than I ever wanted to know. The often found reccomendation I find is that I should replace... private Handler handler = new Handler() with static class handler extends Handler { private final WeakReference<PSActivity> mTarget; handler(PSActivity target) { mTarget = new WeakReference<PSActivity>(target); } But this won't compile still complaining that I can't make a static reference to a non-dtatic field. So, my question a week or to ago was "how can I write a message handler for android so my service can send data to my activity. Even though I have working code, the question still stands with the suffix "without leaking memory". Thanks, Gary

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• Appropriate uses of Monad `fail` vs. MonadPlus `mzero`

  - by jberryman

  This is a question that has come up several times for me in the design code, especially libraries. There seems to be some interest in it so I thought it might make a good community wiki. The fail method in Monad is considered by some to be a wart; a somewhat arbitrary addition to the class that does not come from the original category theory. But of course in the current state of things, many Monad types have logical and useful fail instances. The MonadPlus class is a sub-class of Monad that provides an mzero method which logically encapsulates the idea of failure in a monad. So a library designer who wants to write some monadic code that does some sort of failure handling can choose to make his code use the fail method in Monad or restrict his code to the MonadPlus class, just so that he can feel good about using mzero, even though he doesn't care about the monoidal combining mplus operation at all. Some discussions on this subject are in this wiki page about proposals to reform the MonadPlus class. So I guess I have one specific question: What monad instances, if any, have a natural fail method, but cannot be instances of MonadPlus because they have no logical implementation for mplus? But I'm mostly interested in a discussion about this subject. Thanks! EDIT: One final thought occured to me. I recently learned (even though it's right there in the docs for fail) that monadic "do" notation is desugared in such a way that pattern match failures, as in (x:xs) <- return [] call the monad's fail. It seems like the language designers must have been strongly influenced by the prospect of some automatic failure handling built in to haskell's syntax in their inclusion of fail in Monad.

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• GUID or int entity key with SQL Compact/EF4?

  - by David Veeneman

  This is a follow-up to an earlier question I posted on EF4 entity keys with SQL Compact. SQL Compact doesn't allow server-generated identity keys, so I am left with creating my own keys as objects are added to the ObjectContext. My first choice would be an integer key, and the previous answer linked to a blog post that shows an extension method that uses the Max operator with a selector expression to find the next available key: public static TResult NextId<TSource, TResult>(this ObjectSet<TSource> table, Expression<Func<TSource, TResult>> selector) where TSource : class { TResult lastId = table.Any() ? table.Max(selector) : default(TResult); if (lastId is int) { lastId = (TResult)(object)(((int)(object)lastId) + 1); } return lastId; } Here's my take on the extension method: It will work fine if the ObjectContext that I am working with has an unfiltered entity set. In that case, the ObjectContext will contain all rows from the data table, and I will get an accurate result. But if the entity set is the result of a query filter, the method will return the last entity key in the filtered entity set, which will not necessarily be the last key in the data table. So I think the extension method won't really work. At this point, the obvious solution seems to be to simply use a GUID as the entity key. That way, I only need to call Guid.NewGuid() method to set the ID property before I add a new entity to my ObjectContext. Here is my question: Is there a simple way of getting the last primary key in the data store from EF4 (without having to create a second ObjectContext for that purpose)? Any other reason not to take the easy way out and simply use a GUID? Thanks for your help.

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• Different programming languages possibilities

  - by b-gen-jack-o-neill

  Hello. This should be very simple question. There are many programming languages out there, compiled into machine code or managed code. I first started with ASM back in high school. Assembler is very nice, since you know what exactly CPU does. Next, (as you can see from my other questions here) I decided to learn C and C++. I choosed C becouse from what I read it is the language with output most close to assembler-written programs. But, what I want to know is, can any other Windows programming language out there call win32 API? To be exact, like C has its special header and functions for win32 api interactions, is this assumed to be some important part of programming language? Or are there any languages that have no support for calling win32 API, or just use console to IO and some functions for basic file IO? Becouse, for Windows programming with graphic output, it is essential to have acess to win32 API. I know this question might seem silly, but still please, help me, I ask for study porposes. Thanks.

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