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  • hibernate: com.mysql.jdbc.exceptions.jdbc4.MySQLIntegrityConstraintViolationException

    - by user121196
    when saving an object to database using hibernate, sometimes it fails because certain fields of the object exceed the maximum varchar length defined in the database. There force I am using the following approach: 1. attempt to save 2. if getting an DataException, then I truncate the fields in the object to the max length specified in the db definition, then try to save again. However, in the second save after truncation. I'm getting the following exception: hibernate: com.mysql.jdbc.exceptions.jdbc4.MySQLIntegrityConstraintViolationException: Cannot add or update a child row: a foreign key constraint fails here's the relevant code, what's wrong? public static void saveLenientObject(Object obj){ try { save2(rec); } catch (org.hibernate.exception.DataException e) { // TODO Auto-generated catch block e.printStackTrace(); saveLenientObject(rec, e); } catch (Exception e) { // TODO Auto-generated catch block e.printStackTrace(); } } private static void saveLenientObject(Object rec, DataException e) { Util.truncateObject(rec); System.out.println("after truncation "); save2(rec); } public static void save2(Object obj) throws Exception{ try{ beginTransaction(); getSession().save(obj); commitTransaction(); }catch(Exception e){ e.printStackTrace(); rollbackTransaction(); //closeSession(); throw e; }finally{ closeSession(); } }

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  • Append data to same text file

    - by Manu
    SimpleDateFormat formatter = new SimpleDateFormat("ddMMyyyy_HHmmSS"); String strCurrDate = formatter.format(new java.util.Date()); String strfileNm = "Customer_" + strCurrDate + ".txt"; String strFileGenLoc = strFileLocation + "/" + strfileNm; String Query1="select '0'||to_char(sysdate,'YYYYMMDD')||'123456789' class_code from dual"; String Query2="select '0'||to_char(sysdate,'YYYYMMDD')||'123456789' class_code from dual"; try { Statement stmt = null; ResultSet rs = null; Statement stmt1 = null; ResultSet rs1 = null; stmt = conn.createStatement(); stmt1 = conn.createStatement(); rs = stmt.executeQuery(Query1); rs1 = stmt1.executeQuery(Query2); File f = new File(strFileGenLoc); OutputStream os = (OutputStream)new FileOutputStream(f,true); String encoding = "UTF8"; OutputStreamWriter osw = new OutputStreamWriter(os, encoding); BufferedWriter bw = new BufferedWriter(osw); while (rs.next() ) { bw.write(rs.getString(1)==null? "":rs.getString(1)); bw.write(" "); } bw.flush(); bw.close(); } catch (Exception e) { System.out.println( "Exception occured while getting resultset by the query"); e.printStackTrace(); } finally { try { if (conn != null) { System.out.println("Closing the connection" + conn); conn.close(); } } catch (SQLException e) { System.out.println( "Exception occured while closing the connection"); e.printStackTrace(); } } return objArrayListValue; } The above code is working fine. it writes the content of "rs" resultset data in text file Now what i want is ,i need to append the the content in "rs2" resultset to the "same text file"(ie . i need to append "rs2" content with "rs" content in the same text file)..

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  • Accurately and securely measure the time spent viewing a web page

    - by balpha
    Suppose the following: You have a web page that presents a simple game to a user (e.g. a quiz, a puzzle, etc). The user solves the puzzle, submits the result, and you want to measure as precisely as possible how long they took to solve it. Assume it's quite simple, so we're talking seconds, not hours. Also assume JavaScript is required anyway, so there's no need to think of JS-disabled browsers. Finally, assume we don't want to use anything like Flash, Silverlight, or the like. I can think of several techniques: Simply take the time between the points when the data was sent from the server and when the submission arrives. Since this is exclusively server-side, there's no chance for cheating. However, issues like network latency and page rendering time might make this unfair for users with slow computers / browsers / internet connections. On the first request, just send the page without the actual game data. When everything is loaded so far, retrieve the game data through an AJAX call and populate it into the page. This is similar to 1., but reduces some of the caveats introduced through time spent on overhead. Have the time measured on the client side using JavaScript and submitted alongside with the solution. This would theoretically be the most accurate, but it introduces the possibility of cheating, because you're relying on client data. Use the request time headers of a "ready to play" AJAX call and the result submission request. Same caveat as 3., as it is still client data. A combination of server side and client side measuring with some kind of plausibility analysis. I can't think of a good way, but maybe you can. Thoughts? Other ideas?

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  • When to use @Singleton in a Jersey resource

    - by dexter
    I have a Jersey resource that access the database. Basically it opens a database connection in the initialization of the resource. Performs queries on the resource's methods. I have observed that when I do not use @Singleton, the database is being open at each request. And we know opening a connection is really expensive right? So my question is, should I specify that the resource be singleton or is it really better to keep it at per request especially when the resource is connecting to the database? My resource code looks like this: //Use @Singleton here or not? @Path(/myservice/) public class MyResource { private ResponseGenerator responser; private Log logger = LogFactory.getLog(MyResource.class); public MyResource() { responser = new ResponseGenerator(); } @GET @Path("/clients") public String getClients() { logger.info("GETTING LIST OF CLIENTS"); return responser.returnClients(); } ... // some more methods ... } And I connect to the database using a code similar to this: public class ResponseGenerator { private Connection conn; private PreparedStatement prepStmt; private ResultSet rs; public ResponseGenerator(){ Class.forName("org.h2.Driver"); conn = DriverManager.getConnection("jdbc:h2:testdb"); } public String returnClients(){ String result; try{ prepStmt = conn.prepareStatement("SELECT * FROM hosts"); rs = prepStmt.executeQuery(); ... //do some processing here ... } catch (SQLException se){ logger.warn("Some message"); } finally { rs.close(); prepStmt.close(); // should I also close the connection here (in every method) if I stick to per request // and add getting of connection at the start of every method // conn.close(); } return result } ... // some more methods ... } Some comments on best practices for the code will also be helpful.

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  • Scalability 101: How can I design a scalable web application using PHP?

    - by Legend
    I am building a web-application and have a couple of quick questions. From what I learnt, one should not worry about scalability when initially building the app and should only start worrying when the traffic increases. However, this being my first web-application, I am not quite sure if I should take an approach where I design things in an ad-hoc manner and later "fix" them. I have been reading stories about how people start off with an app that gets millions of users in a week or two. Not that I will face the same situation but I can't help but wonder, how do these people do it? Currently, I bought a shared hosting account on Lunarpages and that got me started in building and testing the application. However, I am interested in learning how to build the same application in a scalable-manner using the cloud, for instance, Amazon's EC2. From my understanding, I can see a couple of components: There is a load balancer that first receives requests and then decides where to route each request This request is then handled by a server replica that then processes the request and updates (if required) the database and sends back the response to the client If a similar request comes in, then a caching mechanism like memcached kicks into picture and returns objects from the cache A blackbox that handles database replication Specifically, I am trying to do the following: Setting up a load balancer (my homework revealed that HAProxy is one such load balancer) Setting up replication so that databases can be synchronized Using memcached Configuring Apache to work with multiple web servers Partitioning application to use Amazon EC2 and Amazon S3 (my application is something that will need great deal of storage) Finally, how can I avoid burning myself when using Amazon services? Because this is just a learning phase, I can probably do with 2-3 servers with a simple load balancer and replication but until I want to avoid paying loads of money accidentally. I am able to find resources on individual topics but am unable to find something that starts off from the big picture. Can someone please help me get started?

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  • public class ImageHandler : IHttpHandler

    - by Ken
    cmd.Parameters.AddWithValue("@id", new system.Guid (imageid)); What using System reference would this require? Here is the handler: using System; using System.Collections.Specialized; using System.Web; using System.Web.Configuration; using System.Web.Security; using System.Globalization; using System.Configuration; using System.Data.SqlClient; using System.Data; using System.IO; using System.Web.Profile; using System.Drawing; public class ImageHandler : IHttpHandler { public void ProcessRequest(HttpContext context) { string imageid; if (context.Request.QueryString["id"] != null) imageid = (context.Request.QueryString["id"]); else throw new ArgumentException("No parameter specified"); context.Response.ContentType = "image/jpeg"; Stream strm = ShowProfileImage(imageid.ToString()); byte[] buffer = new byte[8192]; int byteSeq = strm.Read(buffer, 0, 8192); while (byteSeq > 0) { context.Response.OutputStream.Write(buffer, 0, byteSeq); byteSeq = strm.Read(buffer, 0, 8192); } //context.Response.BinaryWrite(buffer); } public Stream ShowProfileImage(String imageid) { string conn = ConfigurationManager.ConnectionStrings["MyConnectionString1"].ConnectionString; SqlConnection connection = new SqlConnection(conn); string sql = "SELECT image FROM Profile WHERE UserId = @id"; SqlCommand cmd = new SqlCommand(sql, connection); cmd.CommandType = CommandType.Text; cmd.Parameters.AddWithValue("@id", new system.Guid (imageid));//Failing Here!!!! connection.Open(); object img = cmd.ExecuteScalar(); try { return new MemoryStream((byte[])img); } catch { return null; } finally { connection.Close(); } } public bool IsReusable { get { return false; } } }

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  • CREATE VIEW called multiple times not creating all views

    - by theninepoundhammer
    Noticing strange behavior in SQL 2005, both Express and Enterprise Edition: In my code I need to loop through a series of values (about five in a row), and for each value, I need to insert the value into a table and dynamically create a new view using that value as part of the where clause and the name of the view. The code runs pretty quickly, but what I'm noticing is that all the values are inserted into the table correctly but only the LAST view is being created. Every time. For example, if the values I'm using are X1, X2, X3, X4, and X5, I'll run the process, open up Mgmt Studio, and see five rows in the table with the correct five values, but only one view named MyView_x5 that has the correct WHERE clause. At first, I had this loop in an SSIS package as part of a larger data flow. When I started noticing this behavior, I created a stored proc that would create the CREATE VIEW statement dynamically after the insert and called EXECUTE to create the view. Same result. Finally, I created some C# code using the Enterprise Library DAAB, and did the insert and CREATE VIEW statements from my DLL. Same result every time. Most recently, I turned on Profiler while running against the Enterprise Edition and was able to verify that the Batch Started and Batch Completed events were being fired off for each instance of the view. However, like I said, only the last view is actually being created. Does anyone have any idea why this might be happening? Or any suggestions about what else to check or profile? I've profiled for error messages, exceptions, etc. but don't see any in my trace file. My express edition is 9.00.1399.06. Not sure about the Enterprise edition but think it is SP2.

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  • MPI Odd/Even Compare-Split Deadlock

    - by erebel55
    I'm trying to write an MPI version of a program that runs an odd/even compare-split operation on n randomly generated elements. Process 0 should generated the elements and send nlocal of them to the other processes, (keeping the first nlocal for itself). From here, process 0 should print out it's results after running the CompareSplit algorithm. Then, receive the results from the other processes run of the algorithm. Finally, print out the results that it has just received. I have a large chunk of this already done, but I'm getting a deadlock that I can't seem to fix. I would greatly appreciate any hints that people could give me. Here is my code http://pastie.org/3742474 Right now I'm pretty sure that the deadlock is coming from the Send/Recv at lines 134 and 151. I've tried changing the Send to use "tag" instead of myrank for the tag parameter..but when I did that I just keep getting a "MPI_ERR_TAG: invalid tag" for some reason. Obviously I would also run the algorithm within the processors 0 but I took that part out for now, until I figure out what is going wrong. Any help is appreciated.

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  • CSV is actually .... Semicolon Separated Values ... (Excel export on AZERTY)

    - by Bugz R us
    I'm a bit confused here. When I use Excel 2003 to export a sheet to CSV, it actually uses semicolons ... Col1;Col2;Col3 shfdh;dfhdsfhd;fdhsdfh dgsgsd;hdfhd;hdsfhdfsh Now when I read the csv using Microsoft drivers, it expects comma's and sees the list as one big column ??? I suspect Excel is exporting with semicolons because I have a AZERTY keyboard. However, doesn't the CSV reader then also have to take in account the different delimiter ? How can I know the appropriate delimiter, and/or read the csv properly ?? public static DataSet ReadCsv(string fileName) { DataSet ds = new DataSet(); string pathName = System.IO.Path.GetDirectoryName(fileName); string file = System.IO.Path.GetFileName(fileName); OleDbConnection excelConnection = new OleDbConnection (@"Provider=Microsoft.Jet.OLEDB.4.0;Data Source=" + pathName + ";Extended Properties=Text;"); try { OleDbCommand excelCommand = new OleDbCommand(@"SELECT * FROM " + file, excelConnection); OleDbDataAdapter excelAdapter = new OleDbDataAdapter(excelCommand); excelConnection.Open(); excelAdapter.Fill(ds); } catch (Exception exc) { throw exc; } finally { if(excelConnection.State != ConnectionState.Closed ) excelConnection.Close(); } return ds; }

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  • [C#] how to do Exception Handling & Tracing

    - by shrimpy
    Hi all, i am reading some C# books, and got some exercise don't know how to do, or not sure what does the question mean. Problem: After working for a company for some time, your skills as a knowledgeable developer are recognized, and you are given the task of “policing” the implementation of exception handling and tracing in the source code (C#) for an enterprise application that is under constant incremental development. The two goals set by the product architect are: 100% of methods in the entire application must have at least a standard exception handler, using try/catch/finally blocks; more complex methods must also have additional exception handling for specific exceptions All control flow code can optionally write “tracing” information to assist in debugging and instrumentation of the application at run-time in situations where traditional debuggers are not available (eg. on staging and production servers). (i am not quite understand these criterias, i came from the java world, java has two kind of exception, check and unchecked exception. Developer must handle checked exception, and do logging. about unchecked exception, still do logging maybe, but most of the time we just throw it. however here comes to C#, what should i do????) Question for Problem: List rules you would create for the development team to follow, and the ways in which you would enforce rules, to achieve these goals. How would you go about ensuring that all existing code complies with the rules specified by the product architect; in particular, what considerations would impact your planning for the work to ensure all existing code complies?

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  • How might a C# programmer approach writing a solution in javascript?

    - by Ben McCormack
    UPDATE: Perhaps this wasn't clear from my original post, but I'm mainly interested in knowing a best practice for how to structure javascript code while building a solution, not simply learning how to use APIs (though that is certainly important). I need to add functionality to a web site and our team has decided to approach the solution using a web service that receives a call from a JSON-formatted AJAX request from within the web site. The web service has been created and works great. Now I have been tasked with writing the javascript/html side of the solution. If I were solving this problem in C#, I would create separate classes for formatting the request, handling the AJAX request/response, parsing the response, and finally inserting the response somehow into the DOM. I would build properties and methods appropriately into each class, doing my best to separate functionality and structure where appropriate. However, I have to solve this problem in javascript. Firstly, how could I approach my solution in javascript in the way I would approach it from C# as described above? Or more importantly, what's a better way to approach structuring code in javascript? Any advice or links to helpful material on the web would be greatly appreciated. NOTE: Though perhaps not immediately relevant to this question, it may be worth noting that we will be using jQuery in our solution.

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  • Silverlight 4 webclient authentication - anyone have this working yet?

    - by Toran Billups
    So one of the best parts about the new Silverlight 4 beta is that they finally implemented the big missing feature of the networking stack - Network Credentials! In the below I have a working request setup, but for some reason I get a "security error" when the request comes back - is this because twitter.com rejected my api call or something that I'm missing in code? It might be good to point out that when I watch this code execute via fiddler it shows that the xml file for cross domain is pulled down successfully, but that is the last request shown by fiddler ... public void RequestTimelineFromTwitterAPI() { WebRequest.RegisterPrefix("https://", System.Net.Browser.WebRequestCreator.ClientHttp); WebClient myService = new WebClient(); myService.AllowReadStreamBuffering = true; myService.UseDefaultCredentials = false; myService.Credentials = new NetworkCredential("username", "password"); myService.UseDefaultCredentials = false; myService.OpenReadCompleted += new OpenReadCompletedEventHandler(TimelineRequestCompleted); myService.OpenReadAsync(new Uri("https://twitter.com/statuses/friends_timeline.xml")); } public void TimelineRequestCompleted(object sender, System.Net.OpenReadCompletedEventArgs e) { //anytime I query for e.Result I get a security error }

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  • Pass arguments to a parameter class object

    - by David R
    This is undoubtedly a simple question. I used to do this before, but it's been around 10 years since I worked in C++ so I can't remember properly and I can't get a simple constructor call working. The idea is that instead of parsing the args in main, main would create an object specifically designed to parse the arguments and return them as required. So: Parameters params = new Parameters(argc, argv) then I can call things like params.getfile() Only problem is I'm getting a complier error in Visual Studio 2008 and I'm sure this is simple, but I think my mind is just too rusty. What I've got so far is really basic: In the main: #include "stdafx.h" #include "Parameters.h" int _tmain(int argc, _TCHAR* argv[]) { Parameters params = new Parameters(argc, argv); return 0; } Then in the Parameters header: #pragma once class Parameters { public: Parameters(int, _TCHAR*[]); ~Parameters(void); }; Finally in the Parameters class: include "Stdafx.h" #include "Parameters.h" Parameters::Parameters(int argc, _TCHAR* argv[]) { } Parameters::~Parameters(void) { } I would appreciate if anyone could see where my ageing mind has missed the really obvious. Thanks in advance.

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  • Getting functions of inherited functions to be called

    - by wrongusername
    Let's say I have a base class Animal from which a class Cow inherits, and a Barn class containing an Animal vector, and let's say the Animal class has a virtual function scream(), which Cow overrides. With the following code: Animal.h #ifndef _ANIMAL_H #define _ANIMAL_H #include <iostream> using namespace std; class Animal { public: Animal() {}; virtual void scream() {cout << "aaaAAAAAAAAAAGHHHHHHHHHH!!! ahhh..." << endl;} }; #endif /* _ANIMAL_H */ Cow.h #ifndef _COW_H #define _COW_H #include "Animal.h" class Cow: public Animal { public: Cow() {} void scream() {cout << "MOOooooOOOOOOOO!!!" << endl;} }; #endif /* _COW_H */ Barn.h #ifndef _BARN_H #define _BARN_H #include "Animal.h" #include <vector> class Barn { std::vector<Animal> animals; public: Barn() {} void insertAnimal(Animal animal) {animals.push_back(animal);} void tortureAnimals() { for(int a = 0; a < animals.size(); a++) animals[a].scream(); } }; #endif /* _BARN_H */ and finally main.cpp #include <stdlib.h> #include "Barn.h" #include "Cow.h" #include "Chicken.h" /* * */ int main(int argc, char** argv) { Barn barn; barn.insertAnimal(Cow()); barn.tortureAnimals(); return (EXIT_SUCCESS); } I get this output: aaaAAAAAAAAAAGHHHHHHHHHH!!! ahhh... How should I code this to get MOOooooOOOOOOOO!!! (and whatever other classes inheriting Animal wants scream() to be) instead?

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  • Member function overloading/template specialization issue

    - by Ferruccio
    I've been trying to call the overloaded table::scan_index(std::string, ...) member function without success. For the sake of clarity, I have stripped out all non-relevant code. I have a class called table which has an overloaded/templated member function named scan_index() in order to handle strings as a special case. class table : boost::noncopyable { public: template <typename T> void scan_index(T val, std::function<bool (uint recno, T val)> callback) { // code } void scan_index(std::string val, std::function<bool (uint recno, std::string val)> callback) { // code } }; Then there is a hitlist class which has a number of templated member functions which call table::scan_index(T, ...) class hitlist { public: template <typename T> void eq(uint fieldno, T value) { table* index_table = db.get_index_table(fieldno); // code index_table->scan_index<T>(value, [&](uint recno, T n)->bool { // code }); } }; And, finally, the code which kicks it all off: hitlist hl; // code hl.eq<std::string>(*fieldno, p1.to_string()); The problem is that instead of calling table::scan_index(std::string, ...), it calls the templated version. I have tried using both overloading (as shown above) and a specialized function template (below), but nothing seems to work. After staring at this code for a few hours, I feel like I'm missing something obvious. Any ideas? template <> void scan_index<std::string>(std::string val, std::function<bool (uint recno, std::string val)> callback) { // code }

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  • There is a Default instance of form in VB.Net but not in C#, WHY?

    - by Shekhar_Pro
    I'm just curious to know that there is The (Name) property, which represents the name of the Form class.This property is used within the namespace to uniquely identify the class that the Form is an instance of and, in the case of Visual Basic, is used to access the default instance of the form. Now where this Default Instance come from, why can't C# have a equivalent method to this. Also for example to show a form in C# we do something like this: //Only method Form1 frm = new Form1(); frm.Show(); But in VB.Net we have both ways to do it: //'First common method (used slash because editor wouldn't format it properly) Form1.Show(); //'Second method Dim frm as New Form1(); frm.Show(); My question comes from this first method. What is this Form1, is it an instance of Form1 or the Form1 class itself. Now as i mentioned above the Form name is the Default instance in VB.Net. But we also know that Form1 is a class defined in Designer so how can the names be same for both the Instance and class name. If Form1 is Class then there is no (Static\Shared) method named Show(). So where does this method come from. And finally why C# can't have an equivalent of this. If there some mistake in my question Please let me know *I've checked this on stackoverflow, but couldn't find an answer to this.If you do find then please give a link to it.*

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  • IE8 problems with .animate() of opacity property - descendant remains opaque throughout

    - by Fabian
    Basically I have something like this: <ul> <li> <a> <div class="trigger-layer"></div> <div class="title-layer">Text here</div> <div class="hover-layer"></div> </a> </li> </ul> I use jQuery to animate the <ul> as follow: $ul = xxx (where I assign the selector to var $ul) $ul.animate({opacity: 0}, 1000, function() {$ul.css("display", "none")}); However in IE8, as the <ul> fades off, the <div class="title-layer">Text here</div> remains clear and opaque. Finally the animation ends, the display: none; property is applied onto the <ul> and the text disappears aburptly.

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  • Approach for caching data from data logger

    - by filip-fku
    Greetings, I've been working on a C#.NET app that interacts with a data logger. The user can query and obtain logs for a specified time period, and view plots of the data. Typically a new data log is created every minute and stores a measurement for a few parameters. To get meaningful information out of the logger, a reasonable number of logs need to be acquired - data for at least a few days. The hardware interface is a UART to USB module on the device, which restricts transfers to a maximum of about 30 logs/second. This becomes quite slow when reading in the data acquired over a number of days/weeks. What I would like to do is improve the perceived performance for the user. I realize that with the hardware speed limitation the user will have to wait for the full download cycle at least the first time they acquire a larger set of data. My goal is to cache all data seen by the app, so that it can be obtained faster if ever requested again. The approach I have been considering is to use a light database, like SqlServerCe, that can store the data logs as they are received. I am then hoping to first search the cache prior to querying a device for logs. The cache would be updated with any logs obtained by the request that were not already cached. Finally my question - would you consider this to be a good approach? Are there any better alternatives you can think of? I've tried to search SO and Google for reinforcement of the idea, but I mostly run into discussions of web request/content caching. Thanks for any feedback!

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  • Android: Having trouble getting html from webpage

    - by Kyle
    Hi, I'm writing an android application that is supposed to get the html from a php page and use the parsed data from thepage. I've searched for this issue on here, and ended up using some code from an example another poster put up. Here is my code so far: HttpClient client = new DefaultHttpClient(); HttpGet request = new HttpGet(url); try { Log.d("first","first"); HttpResponse response = client.execute(request); String html = ""; Log.d("second","second"); InputStream in = response.getEntity().getContent(); Log.d("third","third"); BufferedReader reader = new BufferedReader(new InputStreamReader(in)); Log.d("fourth","fourth"); StringBuilder str = new StringBuilder(); String line = null; Log.d("fifth","fifth"); while((line = reader.readLine()) != null) { Log.d("request line",line); } in.close(); } catch (ClientProtocolException e) { } catch (IOException e) { // TODO Auto-generated catch block Log.d("error", "error"); } Log.d("end","end"); } Like I said before, the url is a php page. Whenever I run this code, it prints out the first first message, but then prints out the error error message and then finally the end end message. I've tried modifying the headers, but I've had no luck with it. Any help would be greatly appreciated as I don't know what I'm doing wrong. Thanks!

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  • Is is possible to do an end-run around generics covariance in C# < 4 in this hypothetical situation?

    - by John Feminella
    Suppose I have a small inheritance hierarchy of Animals: public interface IAnimal { string Speak(); } public class Animal : IAnimal { public Animal() {} public string Speak() { return "[Animal] Growl!"; } } public class Ape : IAnimal { public string Speak() { return "[Ape] Rawrrrrrrr!"; } } public class Bat : IAnimal { public string Speak() { return "[Bat] Screeeeeee!"; } } Next, here's an interface offering a way to turn strings into IAnimals. public interface ITransmogrifier<T> where T : IAnimal { T Transmogrify(string s); } And finally, here's one strategy for doing that: public class Transmogrifier<T> : ITransmogrifier<T> where T : IAnimal, new() { public T Transmogrify(string s) { T t = default(T); if (typeof(T).Name == s) t = new T(); return t; } } Now, the question. Is it possible to replace the sections marked [1], [2], and [3] such that this program will compile and run correctly? If you can't do it without touching parts other than [1], [2], and [3], can you still get an IAnimal out of each instance of a Transmogrifier in a collection containing arbitrary implementations of an IAnimal? Can you even form such a collection to begin with? static void Main(string[] args) { var t = new Transmogrifier<Ape>(); Ape a = t.Transmogrify("Ape"); Console.WriteLine(a.Speak()); // Works! // But can we make an arbitrary collection of such animals? var list = new List<Transmogrifier< [1] >>() { // [2] }; // And how about we call Transmogrify() on each one? foreach (/* [3] */ transmogrifier in list) { IAnimal ia = transmogrifier.Transmogrify("Bat"); } } }

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  • Matlab GUI: How to Save the Results of Functions (states of application)

    - by niko
    Hi, I would like to create an animation which enables the user to go backward and forward through the steps of simulation. An animation has to simulate the iterative process of channel decoding (a receiver receives a block of bits, performs an operation and then checks if the block corresponds to parity rules. If the block doesn't correspond the operation is performed again and the process finally ends when the code corresponds to a given rules). I have written the functions which perform the decoding process and return a m x n x i matrix where m x n is the block of data and i is the iteration index. So if it takes 3 iterations to decode the data the function returns a m x n x 3 matrix with each step is stired. In the GUI (.fig file) I put a "decode" button which runs the method for decoding and there are buttons "back" and "forward" which have to enable the user to switch between the data of recorded steps. I have stored the "decodedData" matrix and currentStep value as a global variable so by clicking "forward" and "next" buttons the indices have to change and point to appropriate step states. When I tried to debug the application the method returned the decoded data but when I tried to click "back" and "next" the decoded data appeared not to be declared. Does anyone know how is it possible to access (or store) the results of the functions in order to enable the described logic which I want to implement in Matlab GUI?

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  • How to make Spring load a JDBC Driver BEFORE initializing Hibernate's SessionFactory?

    - by Bill_BsB
    I'm developing a Spring(2.5.6)+Hibernate(3.2.6) web application to connect to a custom database. For that I have custom JDBC Driver and Hibernate Dialect. I know for sure that these custom classes work (hard coded stuff on my unit tests). The problem, I guess, is with the order on which things get loaded by Spring. Basically: Custom Database initializes Spring load beans from web.xml Spring loads ServletBeans(applicationContext.xml) Hibernate kicks in: shows version and all the properties correctly loaded. Hibernate's HbmBinder runs (maps all my classes) LocalSessionFactoryBean - Building new Hibernate SessionFactory DriverManagerConnectionProvider - using driver: MyCustomJDBCDriver at CustomDBURL I get a SQLException: No suitable driver found for CustomDBURL Hibernate loads the Custom Dialect My CustomJDBCDriver finally gets registered with DriverManager (log messages) SettingsFactory runs SchemaExport runs (hbm2ddl) I get a SQLException: No suitable driver found for CustomDBURL (again?!) Application get successfully deployed but there are no tables on my custom Database. Things that I tried so far: Different techniques for passing hibernate properties: embedded in the 'sessionFactory' bean, loaded from a hibernate.properties file. Nothing worked but I didn't try with hibernate.cfg.xml file neither with a dataSource bean yet. MyCustomJDBCDriver has a static initializer block that registers it self with the DriverManager. Tried different combinations of lazy initializing (lazy-init="true") of the Spring beans but nothing worked. My custom JDBC driver should be the first thing to be loaded - not sure if by Spring but...! Can anyone give me a solution for this or maybe a hint for what else I could try? I can provide more details (huge stack traces for instance) if that helps. Thanks in advance.

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  • Best way to run multiple queries per second on database, performance wise?

    - by Michael Joell
    I am currently using Java to insert and update data multiple times per second. Never having used databases with Java, I am not sure what is required, and how to get the best performance. I currently have a method for each type of query I need to do (for example, update a row in a database). I also have a method to create the database connection. Below is my simplified code. public static void addOneForUserInChannel(String channel, String username) throws SQLException { Connection dbConnection = null; PreparedStatement ps = null; String updateSQL = "UPDATE " + channel + "_count SET messages = messages + 1 WHERE username = ?"; try { dbConnection = getDBConnection(); ps = dbConnection.prepareStatement(updateSQL); ps.setString(1, username); ps.executeUpdate(); } catch(SQLException e) { System.out.println(e.getMessage()); } finally { if(ps != null) { ps.close(); } if(dbConnection != null) { dbConnection.close(); } } } And my DB connection private static Connection getDBConnection() { Connection dbConnection = null; try { Class.forName(DB_DRIVER); } catch (ClassNotFoundException e) { System.out.println(e.getMessage()); } try { dbConnection = DriverManager.getConnection(DB_CONNECTION, DB_USER,DB_PASSWORD); return dbConnection; } catch (SQLException e) { System.out.println(e.getMessage()); } return dbConnection; } This seems to be working fine for now, with about 1-2 queries per second, but I am worried that once I expand and it is running many more, I might have some issues. My questions: Is there a way to have a persistent database connection throughout the entire run time of the process? If so, should I do this? Are there any other optimizations that I should do to help with performance? Thanks

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  • What problem did MS solve by creating PowerShell? [closed]

    - by Fred
    I'm asking because PowerShell confuses me. I've been trying to write some deployment scripts using PowerShell and I've been less than enthused by the result. I have a co-worker who loves PowerShell and defends it at every turn. Said co-worker claims PowerShell was never written to be a strong shell, but instead was written to: a) Allow you to peek and poke at .NET assemblies on the command-line (why is this a reason for PowerShell to exist?) b) To be hosted in .NET applications for automation, similar to DCOP in KDE and how Gnome is using CORBA. c) to be treated as ".NET script" rather than as an actual shell (related to b). I've always felt like Windows was missing a decent way to bang out automation scripts. cmd is too simplistic in many cases, and WSH is too obtuse (although the combination can be used successfully, I'm not a fan). When I first heard about PowerShell I felt like Windows was finally getting a decent shell that would be able to help with automation of many tasks, but recent experiences, and my co-worker, tell me otherwise. To be clear, I don't take issue with the fact that it's built on .NET, or that it passes objects around rather than text (despite my Unix background :]), and I'm not arguing that PowerShell is useless, but from what I can see, it doesn't solve the problem I was hoping it would solve very well. As soon as you step outside of the .NET/Powershell world, things quit being nice and cozy for you. So with all that out of the way, what problem did MS solve by creating PowerShell, or is it some political bastard child as I suspect? I've googled and haven't hit upon anything that sufficiently answered that for me, but the more citations the better.

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  • Functioning Socket read no longer works when called in AsyncTask

    - by bibismcbryde
    I'm making an app that sends a string to a server over a socket and then reads the output after the server has processed that data. It worked perfectly when it was my foreground task, but I have since used AsyncTask to show a process dialog while the socket communication runs in the background, and things start breaking after I read the output from the server and then try to close the socket. private class Progressor extends AsyncTask<String, Void, Void> { ProgressDialog dialog; protected void onPreExecute() { dialog = ProgressDialog.show(ClearTalkInputActivity.this, "Loading..", "Analyzing Text", true, false); } protected Void doInBackground(String... strings) { String language = strings[0].toLowerCase(); String the_text = strings[1]; Socket socket = null; DataOutputStream dos = null; DataInputStream dis = null; try { socket = new Socket(my_ip, port); dos = new DataOutputStream(socket.getOutputStream()); dis = new DataInputStream(socket.getInputStream()); dos.writeUTF(language+"****"+the_text); String in = ""; while (in.indexOf("</content>") < 0) { in += dis.readUTF(); } socket.close(); save_str(OUTPUT_KEY, in); } catch (UnknownHostException e) { e.printStackTrace(); } catch (IOException e) { e.printStackTrace(); } finally { if (socket != null) { try { socket.close(); } catch (IOException e) { e.printStackTrace(); } } } if (dos != null) { try { dos.close(); } catch (IOException e) { e.printStackTrace(); } } if (dis != null) { try { dis.close(); } catch (IOException e) { e.printStackTrace(); } } return null; } protected void onPostExecute() { if (dialog.isShowing()) dialog.dismiss(); startActivity(new Intent (output_intent)); } }

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