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• MySQL - Calculating fields on the fly vs storing calculated data

  - by Christian Varga

  Hi Everyone, I apologise if this has been asked before, but I can't seem to find an answer to a question that I have about calculating on the fly vs storing fields in a database. I read a few articles that suggested it was preferable to calculate when you can, but I would just like to know if that still applies to the following 2 examples. Example 1. Say you are storing data relating to a car. You store the fuel tank size in litres, and how many litres it uses per 100km. You also want to know how many KMs it can travel, which can be calculated from the tank size and economy. I see 2 ways of doing this: When a car is added or updated, calculate the amount of KMs and store this as a static field in the database. Every time a car is accessed, calculate the amount of KMs on the fly. Because the cars economy/tank size doesn't change (although it could be edited), the KMs is a pretty static value. I don't see why we would calculate it every single time the car is accessed. Wouldn't this waste cpu time as opposed to simply storing it in a separate field in the database and calculating only when a car is added or updated? My next example, which is almost an entirely different question (but on the same topic), relates to counting children. Let's say we have a app which has categories and items. We have a view where we display all the categories, and a count of all the items inside each category. Again, I'm wondering what's better. To perform a MySQL query to count all the items in each category every single time the page is accessed? Or store the count in a field in the categories table and update when an item is added / deleted? I know it is redundant to store anything that can be calculated, but I worry that calculating fields or counting records might be slow as opposed to storing the data in a field. If it's not then please let me know, I just want to learn about when to use either method. On a small scale I guess it wouldn't matter either way, but apps like Facebook, would they really count the amount of friends you have every time someone views your profile or would they just store it as a field? I'd appreciate any responses to both of these scenarios, and any resource that might explain the benefits of calculating vs storing. Thanks in advance, Christian

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• .NET Reflection: How to call method of interface without creating instance?

  - by jitm

  I have situation where I have to call method of interface using reflection, like this object x = null; MethodInfo method = interfaceExists.GetMethod("ShutDown"); method.Invoke(x, new object[] { 4 }) As you can see I do not create instance of object! And, as I can supposed, I receive exception Non-static method requires a target And Question, Can I call method of interface using reflection without creating instance of interface and if YES, How I can do it ?

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• Solving a cyclical dependency in Ninject (Compact Framework)

  - by Alex

  I'm trying to use Ninject for dependency injection in my MVP application. However, I have a problem because I have two types that depend on each other, thus creating a cyclic dependency. At first, I understand that it was a problem, because I had both types require each other in their constructors. Therefore, I moved one of the dependencies to a property injection instead, but I'm still getting the error message. What am I doing wrong? This is the presenter: public class LoginPresenter : Presenter<ILoginView>, ILoginPresenter { public LoginPresenter( ILoginView view ) : base( view ) { } } and this is the view: public partial class LoginForm : Form, ILoginView { [Inject] public ILoginPresenter Presenter { private get; set; } public LoginForm() { InitializeComponent(); } } And here's the code that causes the exception: static class Program { /// <summary> /// The main entry point for the application. /// </summary> [MTAThread] static void Main() { // Show the login form Views.LoginForm loginForm = Kernel.Get<Views.Interfaces.ILoginView>() as Views.LoginForm; Application.Run( loginForm ); } } The exception happens on the line with the Kernel.Get<>() call. Here it is: Error activating ILoginPresenter using binding from ILoginPresenter to LoginPresenter A cyclical dependency was detected between the constructors of two services. Activation path: 4) Injection of dependency ILoginPresenter into property Presenter of type LoginForm 3) Injection of dependency ILoginView into parameter view of constructor of type LoginPresenter 2) Injection of dependency ILoginPresenter into property Presenter of type LoginForm 1) Request for ILoginView Suggestions: 1) Ensure that you have not declared a dependency for ILoginPresenter on any implementations of the service. 2) Consider combining the services into a single one to remove the cycle. 3) Use property injection instead of constructor injection, and implement IInitializable if you need initialization logic to be run after property values have been injected. Why doesn't Ninject understand that since one is constructor injection and the other is property injection, this can work just fine? I even read somewhere looking for the solution to this problem that Ninject supposedly gets this right as long as the cyclic dependency isn't both in the constructors. Apparently not, though. Any help resolving this would be much appreciated.

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• How to discover classes with [Authorize] attributes using Reflection in C#? (or How to build Dynamic

  - by Pretzel

  Maybe I should back-up and widen the scope before diving into the title question... I'm currently writing a web app in ASP.NET MVC 1.0 (although I do have MVC 2.0 installed on my PC, so I'm not exactly restricted to 1.0) -- I've started with the standard MVC project which has your basic "Welcome to ASP.NET MVC" and shows both the [Home] tab and [About] tab in the upper-right corner. Pretty standard, right? I've added 4 new Controller classes, let's call them "Astronomer", "Biologist", "Chemist", and "Physicist". Attached to each new controller class is the [Authorize] attribute. For example, for the BiologistController.cs [Authorize(Roles = "Biologist,Admin")] public class BiologistController : Controller { public ActionResult Index() { return View(); } } These [Authorize] tags naturally limit which user can access different controllers depending on Roles, but I want to dynamically build a Menu at the top of my website in the Site.Master Page based on the Roles the user is a part of. So for example, if JoeUser was a member of Roles "Astronomer" and "Physicist", the navigation menu would say: [Home] [Astronomer] [Physicist] [About] And naturally, it would not list links to "Biologist" or "Chemist" controller Index page. Or if "JohnAdmin" was a member of Role "Admin", links to all 4 controllers would show up in the navigation bar. Ok, you prolly get the idea... Starting with the answer from this StackOverflow topic about Dynamic Menu building in ASP.NET, I'm trying to understand how I would fully implement this. (I'm a newbie and need a little more guidance, so please bare with me.) The answer proposes Extending the Controller class (call it "ExtController") and then have each new WhateverController inherit from ExtController. My conclusion is that I would need to use Reflection in this ExtController Constructor to determine which Classes and Methods have [Authorize] attributes attached to them to determine the Roles. Then using a Static Dictionary, store the Roles and Controllers/Methods in key-value pairs. I imagine it something like this: public class ExtController : Controller { protected static Dictionary<Type,List<string>> ControllerRolesDictionary; protected override void OnActionExecuted(ActionExecutedContext filterContext) { // build list of menu items based on user's permissions, and add it to ViewData IEnumerable<MenuItem> menu = BuildMenu(); ViewData["Menu"] = menu; } private IEnumerable<MenuItem> BuildMenu() { // Code to build a menu SomeRoleProvider rp = new SomeRoleProvider(); foreach (var role in rp.GetRolesForUser(HttpContext.User.Identity.Name)) { } } public ExtController() { // Use this.GetType() to determine if this Controller is already in the Dictionary if (!ControllerRolesDictionary.ContainsKey(this.GetType())) { // If not, use Reflection to add List of Roles to Dictionary // associating with Controller } } } Is this doable? If so, how do I perform Reflection in the ExtController constructor to discover the [Authorize] attribute and related Roles (if any) ALSO! Feel free to go out-of-scope on this question and suggest an alternate way of solving this "Dynamic Site.Master Menu based on Roles" problem. I'm the first to admit that this may not be the best approach.

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• WPF ControlTemplate and Binding

  - by Vinjamuri

  In the below code, MousePressImage is a dependency property of class ButtonControl. The following Binding doesn't work.. Appreciate your help in solving this issue.. Value="{Binding RelativeSource={x:Static RelativeSource.Self}, Path=MousePressImage}"/> -- I create the ButtonControl like this. <local:ButtonControl Height="48" Width="160" MouseOverImage="pack://application:,,,/Recipe_06_13;component/Resources/Over.bmp" MousePressImage="pack://application:,,,/Recipe_06_13;component/Resources/Press.bmp" DisableImage=" "> </local:ButtonControl>

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• using a Singleton to pass credentials in a multi-tenant application a code smell?

  - by Hans Gruber

  Currently working on a multi-tenant application that employs Shared DB/Shared Schema approach. IOW, we enforce tenant data segregation by defining a TenantID column on all tables. By convention, all SQL reads/writes must include a Where TenantID = '?' clause. Not an ideal solution, but hindsight is 20/20. Anyway, since virtually every page/workflow in our app must display tenant specific data, I made the (poor) decision at the project's outset to employ a Singleton to encapsulate the current user credentials (i.e. TenantID and UserID). My thinking at the time was that I didn't want to add a TenantID parameter to each and every method signature in my Data layer. Here's what the basic pseudo-code looks like: public class UserIdentity { public UserIdentity(int tenantID, int userID) { TenantID = tenantID; UserID = userID; } public int TenantID { get; private set; } public int UserID { get; private set; } } public class AuthenticationModule : IHttpModule { public void Init(HttpApplication context) { context.AuthenticateRequest += new EventHandler(context_AuthenticateRequest); } private void context_AuthenticateRequest(object sender, EventArgs e) { var userIdentity = _authenticationService.AuthenticateUser(sender); if (userIdentity == null) { //authentication failed, so redirect to login page, etc } else { //put the userIdentity into the HttpContext object so that //its only valid for the lifetime of a single request HttpContext.Current.Items["UserIdentity"] = userIdentity; } } } public static class CurrentUser { public static UserIdentity Instance { get { return HttpContext.Current.Items["UserIdentity"]; } } } public class WidgetRepository: IWidgetRepository{ public IEnumerable<Widget> ListWidgets(){ var tenantId = CurrentUser.Instance.TenantID; //call sproc with tenantId parameter } } As you can see, there are several code smells here. This is a singleton, so it's already not unit test friendly. On top of that you have a very tight-coupling between CurrentUser and the HttpContext object. By extension, this also means that I have a reference to System.Web in my Data layer (shudder). I want to pay down some technical debt this sprint by getting rid of this singleton for the reasons mentioned above. I have a few thoughts on what an better implementation might be, but if anyone has any guidance or lessons learned they could share, I would be much obliged.

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• Java converting to Jython-Getting a class object within itself

  - by Bggreen

  I am attempting to convert Java code to Jython and am using the apache Log and LogFactory imports. I am attempting to emulate Foo.class in Jython The chunk of code is as follows: in Java import org.apache.commons.logging.Log; import org.apache.commons.logging.LogFactory; public class MyClass { private static final Log log = LogFactory.getLog(MyClass.class); public MyClass(Document dom) { //code } How can I emulate this same behavior of MyClass.class in Jython/Python?

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• j2me bluetooth client. Function startInquiry nothing found.

  - by Hugi

  I develop simple j2me bluetooth client and have problem with bluetooth device search. Function startInquiry nothing found. Client : nokia 5220 Server : my pc with bluetooth adapter All bluetooth devices is on. /* * To change this template, choose Tools | Templates * and open the template in the editor. */ import javax.microedition.midlet.*; import javax.bluetooth.*; import java.util.Vector; import javax.microedition.lcdui.*; /** * @author ????????????? */ public class Midlet extends MIDlet implements DiscoveryListener { private static Vector vecDevices=new Vector(); private static String connectionURL=null; private LocalDevice localDevice; private DiscoveryAgent agent; private RemoteDevice remoteDevice; private RemoteDevice[] devList; private Display display; private Form form; public void startApp() { display = Display.getDisplay(this); form = new Form( "Client" ); try { localDevice = LocalDevice.getLocalDevice(); } catch( BluetoothStateException e ) { e.printStackTrace(); } form.append("Address: "+localDevice.getBluetoothAddress()+"\n\n"); form.append("Name: "+localDevice.getFriendlyName()+"\n\n"); try { agent = localDevice.getLocalDevice().getDiscoveryAgent(); form.append("Starting device inquiry... \n\n"); boolean si = agent.startInquiry(DiscoveryAgent.GIAC, this); if ( si ) { form.append("true"); } else { form.append("false"); } } catch( BluetoothStateException e ) { } int deviceCount = vecDevices.size(); if(deviceCount <= 0){ form.append("No Devices Found ."); } else{ //print bluetooth device addresses and names in the format [ No. address (name) ] form.append("Bluetooth Devices: "); for (int i = 0; i < deviceCount; i++) { remoteDevice=(RemoteDevice)vecDevices.elementAt(i); form.append( remoteDevice.getBluetoothAddress() ); } } display.setCurrent(form); } public void pauseApp() { } public void destroyApp(boolean unconditional) { } public void deviceDiscovered(RemoteDevice btDevice, DeviceClass cod) { //add the device to the vector if(!vecDevices.contains(btDevice)){ vecDevices.addElement(btDevice); } } public void inquiryCompleted(int discType) { } //implement this method since services are not being discovered public void servicesDiscovered(int transID, ServiceRecord[] servRecord) { if(servRecord!=null && servRecord.length>0){ connectionURL=servRecord[0].getConnectionURL(0,false); } } //implement this method since services are not being discovered public void serviceSearchCompleted(int transID, int respCode) { } }

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• Your creative PHP Obfuscation - Dynamic Variables

  - by Email

  Hi No thread about use or unuse of obfuscusion please ^^ Just share creative approaches how to obfuscate in php the really smart way plz. plain md5 and base64_decode is too static .. what you think regarding hash, salt what about dynamic Variables (even for the same $var). Thx for any creative input

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• Find the closest palindrome number C#

  - by user294837

  Hi All, I am trying to create a console application that reads number from a file all underneath each other like so: 101 9 and then outputs into another file the closest palindrome number. So far what I have is not quite rightm i.e. I don't think I can put the class inside a method which is a bit more Java I was wandering if anyone could help at all? Thanks :) namespace PalidromeC { class Program { static public void Main(string[] args) { #region WriteAnswers try { StreamWriter sw = new StreamWriter("C://Temp/PalindromeAnswers.txt"); sw.WriteLine("Answers"); sw.Close(); }//try catch (Exception e) { Console.WriteLine("Exception: " + e.Message); }//catch #endregion #region ReadFile try { string numbers; StreamReader sr = new StreamReader("C://Temp/Palindrome.txt"); numbers = sr.ReadLine(); while (numbers != null) { Console.WriteLine(numbers); numbers = sr.ReadLine(); }//while sr.Close(); Console.ReadLine(); }//try catch (Exception e) { Console.WriteLine("Exception: " + e.Message); }//catch #endregion NearPalindromeFinder f = new NearPalindromeFinder(); int palindrome = f.findNearPalindrome(n); Console.WriteLine("Nearest Palindrome = " + palindrome); }//main public static void testFindNearestPalindrome(int n) { class NearPalindromeFinder { int findNearPalindrome(int start) { if (testPalindrome(start)) return start; else { int neg = start; int pos = start; for (int i = 0; i < start; i++) { if (testPalindrome(start-i)) { neg = start-i; break; }//if if (testPalindrome(start+i)) { pos = start+i; break; }//if }//for return (start == neg) ? pos : neg; }//else }//findNearPalindrome bool testPalindrome(int start) { if (start == 0 || start == 1) return true; String str = String.valueOf(start); String rev = new if (str.equals(rev)) return true; else return false; }//testPalindrome }//NearPalindromeFinder class }//testFindNearestPalindrome }//Program Class

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• controlling the class names generated by JAXB for xsd:attributeGroup?

  - by Stephen Winnall

  I am using JAXB to bind XML to Java for an application that I am writing. I have an element called measure which contains two amount elements called amount and maxAmount, with which I want to model a lower and an upper limiting value. amount and maxAmount are otherwise identical and I would like them to be implemented with the same class when unmarshalled into Java. The following is an extract from the XML schema which I feed to JAXB: <xsd:attributeGroup name="AmountAttributes"> <xsd:attribute name="quantity" type="xsd:decimal"/> <xsd:attribute name="numerator" type="xsd:nonNegativeInteger"/> <xsd:attribute name="denominator" type="xsd:positiveInteger"/> </xsd:attributeGroup> <xsd:element name="measure"> <xsd:complexType> <xsd:sequence> <xsd:element minOccurs="0" name="amount"> <xsd:complexType> <xsd:attributeGroup ref="mpr:AmountAttributes"/> </xsd:complexType> </xsd:element> <xsd:element minOccurs="0" name="maxAmount"> <xsd:complexType> <xsd:attributeGroup ref="mpr:AmountAttributes"/> </xsd:complexType> </xsd:element> </xsd:sequence> </xsd:complexType> </xsd:element> JAXB creates from this a more elaborate version of the following: public class Measure { protected Measure.Amount amount; protected Measure.MaxAmount maxAmount; public static class Measure.Amount {} public static class Measure.MaxAmount {} } Measure.Amount and Measure.MaxAmount are identical except for their names, but - of course - as far as Java is concerned they have little to do with each other. Is there a way of making JAXB use the same class for both amount and maxAmount? Just to come completely clean ;-) I should mention that I generate the XML schema from RNC using Trang. If the answer to the question is "change the XML schema", I have the supplementary question "how do I change the RNC to produce that XML schema?". My RNC looks like this: AmountAttributes = QuantityAttribute? & attribute numerator { xsd:nonNegativeInteger }? & attribute denominator { xsd:positiveInteger }? QuantityAttribute = attribute quantity { xsd:decimal } Measure = element measure { element amount { AmountAttributes }?, element maxAmount { AmountAttributes }? }+ I use RNC because I find it simpler to understand, but if the solution to my problem means just using XML Schema, so be it. Steve

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• Expand Drupal menu by default

  - by Dan G

  For the menu system, is there a way to set one of the menu items to be expanded by default? I can't get my home menu item to be expanded on the homepage (at the least), and I'd like it to be expanded whenever one of the other ones isn't. I'm using Drupal 5, and the Taxonomy Menu module. Taxonomy Menu is pretty good with 95% of my pages, but some are static "About Us" type pages, which I'd like to have the home menu as default for, and then there's the homepage.

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• Java: Interface vs Abstract Class (regarding fields)

  - by lifeR00t

  From what I have gathered, I want to force a class to use particular private fields (and methods) I need an abstract class because an interface only declares public/static/final fields and methods. Correct?? I just started my first big java project and want to make sure I'm not going to hurt myself later :)

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• JBoss 4.2.3 - how to find path to jar file

  - by Gribbler

  I'm getting an error in a JBOSS application: Static Method [addHeader] not found on JavaBean [class com.ppnet.webservice.WebserviceHeaderWriter] I have checked the WebserviceHeaderWriter.jar that gets deployed into JBOSS and checked it in eclipse. It looks as if it should have this method on it. I think that the JBoss application might be loading a different version of the WebserviceHeaderWriter.jar without this method on it, is there a way to check the location of the file that is getting loaded?

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• How to use global caching in php?

  - by user63898

  ello all im new to php and server scripting ( coming from the java/cpp background ) my question is , if i like to be able to build some kind of single tone cache that will hold me data in memory in all the web application life , something that when i start the web server it will start main cache that will server the web application not inside sessions static cache like singletone map in c++/java that that leaves all the time what are my options ?

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• quick java question

  - by j-unit-122

  private static char[] quicksort (char[] array , int left , int right) { if (left < right) { int p = partition(array , left, right); quicksort(array, left, p - 1 ); quicksort(array, p + 1 , right); } for (char i : array) System.out.print(i + ” ”); System.out.println(); return array; } private static int partition(char[] a, int left, int right) { char p = a[left]; int l = left + 1, r = right; while (l < r) { while (l < right && a[l] < p) l++; while (r > left && a[r] >= p) r--; if (l < r) { char temp = a[l]; a[l] = a[r]; a[r] = temp; } } a[left] = a[r]; a[r] = p; return r; } } hi guys just a quick question regarding the above coding, i know that the above coding returns the following B I G C O M P U T E R B C E G I M P U T O R B C E G I M P U T O R B C E G I M P U T O R B C E G I M P U T O R B C E G I M O P T U R B C E G I M O P R T U B C E G I M O P R T U B C E G I M O P R T U B C E G I M O P R T U B C E G I M O P R T U B C E G I M O P R T U B C E G I M O P R T U when the sequence BIGCOMPUTER is used but my question is can someone explain to me what is happening in the code and how? i know abit about the quick-sort algorithm but it doesnt seem to be the same in the above example.

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• How do I get the current Cmdlet from another object?

  - by John Vottero

  What's the best way to get the current PowerShell Cmdlet from another object? If I create a helper object that is not a Cmdlet but will be called by Cmdlets, the helper methods may want to call WriteVerbose, WriteDebug etc. What's the best way to get access to that? Is there a static PowerShell method that will return the current Cmdlet or do I need to have the Cmdlet pass itself to the helper?

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• Unable to decode hex values in javascript tooltip

  - by staudk27

  Hi all, I have quite the process that we go through in order to display some e-mail communications in our application. Trying to keep it as general as possible... -We make a request to a service via XML -Get the XML reply string, send the string to a method to encode any invalid characters as follows: public static String convertUTF8(String value) { char[] chars = value.toCharArray(); StringBuffer retVal = new StringBuffer(chars.length); for (int i = 0; i < chars.length; i++) { char c = chars[i]; int chVal = (int)c; if (chVal > Byte.MAX_VALUE) { retVal.append("&#x").append(Integer.toHexString(chVal)).append(";"); } else { retVal.append(c); } } return retVal.toString(); } We then send that result of a string to another method to remove any other invalid characters: public static String removeInvalidCharacters(String inString) { if (inString == null){ return null; } StringBuffer newString = new StringBuffer(); char ch; char c[] = inString.toCharArray(); for (int i = 0; i < c.length; i++) { ch = c[i]; // remove any characters outside the valid UTF-8 range as well as all control characters // except tabs and new lines if ((ch < 0x00FD && ch > 0x001F) || ch == '\t' || ch == '\n' || ch == '\r') { newString.append(ch); } } return newString.toString(); } This string is then "unmarshal'ed" via the SaxParser The object is then sent back to our Display action which generated the response to the calling jsp/javascript to create the page. The issue is some text can contain characters which can't be processed correctly. The following is eventually rendered on the JSP just fine: <PrvwCommTxt>This is a new test. Have a*&amp;#xc7;&amp;#xb4;)&amp;#xa1;.&amp;#xf1;&amp;#xc7;&amp;#xa1;.&amp;#xf1;*&amp;#xc7;&amp;#xb4;)...</PrvwCommTxt> Which shows up as "This is a new test. Have a*Ç´)¡.ñÇ¡." in the browser. -The following shows up in a tooltip while hovering over the above text: <CommDetails>This is a new test. Have a*Ç´)¡.ñÇ¡.ñ*Ç´)¡.ñ*´)(¡.ñÇ(¡.ñÇ* Wonderful Day!</CommDetails> This then shows up incorrectly when rendered in the tooltip javascript with all the HEX values and not being rendered correctly. Any suggestions on how to make the unknown characters show correctly in javascript?

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• compiling a linq to sql query

  - by frenchie

  Hi, I have queries that are built like this: public static List<MyObjectModel> GetData (int MyParam) { using (DataModel MyModelDC = new DataModel()) { var MyQuery = from.... select MyObjectModel { ...} } return new List<MyObjectModel> (MyQuery) } } It seems that using compiled linq-to-sql queries are about as fast as stored procedures and so the goal is to convert these queries into compiled queries. What's the syntax for this? Thanks.

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• Problem persisting inheritance tree

  - by alaiseca

  I have a problem trying to map an inheritance tree. A simplified version of my model is like this: @MappedSuperclass @Embeddable public class BaseEmbedded implements Serializable { @Column(name="BE_FIELD") private String beField; // Getters and setters follow } @MappedSuperclass @Embeddable public class DerivedEmbedded extends BaseEmbedded { @Column(name="DE_FIELD") private String deField; // Getters and setters follow } @MappedSuperclass public abstract class BaseClass implements Serializable { @Embedded protected BaseEmbedded embedded; public BaseClass() { this.embedded = new BaseEmbedded(); } // Getters and setters follow } @Entity @Table(name="MYTABLE") @Inheritance(strategy=InheritanceType.SINGLE_TABLE) @DiscriminatorColumn(name="TYPE", discriminatorType=DiscriminatorType.STRING) public class DerivedClass extends BaseClass { @Id @Column(name="ID", nullable=false) private Long id; @Column(name="TYPE", nullable=false, insertable=false, updatable=false) private String type; public DerivedClass() { this.embedded = new DerivedClass(); } // Getters and setters follow } @Entity @DiscriminatorValue("A") public class DerivedClassA extends DerivedClass { @Embeddable public static NestedClassA extends DerivedEmbedded { @Column(name="FIELD_CLASS_A") private String fieldClassA; } public DerivedClassA() { this.embedded = new NestedClassA(); } // Getters and setters follow } @Entity @DiscriminatorValue("B") public class DerivedClassB extends DerivedClass { @Embeddable public static NestedClassB extends DerivedEmbedded { @Column(name="FIELD_CLASS_B") private String fieldClassB; } public DerivedClassB() { this.embedded = new NestedClassB(); } // Getters and setters follow } At Java level, this model is working fine, and I believe is the appropriate one. My problem comes up when it's time to persist an object. At runtime, I can create an object which could be an instance of DerivedClass, DerivedClassA or DerivedClassB. As you can see, each one of the derived classes introduces a new field which only makes sense for that specific derived class. All the classes share the same physical table in the database. If I persist an object of type DerivedClass, I expect fields BE_FIELD, DE_FIELD, ID and TYPE to be persisted with their values and the remaining fields to be null. If I persist an object of type DerivedClass A, I expect those same fields plus the FIELD_CLASS_A field to be persisted with their values and field FIELD_CLASS_B to be null. Something equivalent for an object of type DerivedClassB. Since the @Embedded annotation is at the BaseClass only, Hibernate is only persisting the fields up to that level in the tree. I don't know how to tell Hibernate that I want to persist up to the appropriate level in the tree, depending on the actual type of the embedded property. I cannot have another @Embedded property in the subclasses since this would duplicate data that is already present in the superclass and would also break the Java model. I cannot declare the embedded property to be of a more specific type either, since it's only at runtime when the actual object is created and I don't have a single branch in the hierarchy. Is it possible to solve my problem? Or should I resignate myself to accept that there is no way to persist the Java model as it is? Any help will be greatly appreciated.

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• Qt send signal to main application window

  - by dumbquestion

  I need a QDialog to send a signal to redraw the main window. But connect needs an object to connect to. So I must create each dialog with new and explicitly put a connect() every time. What I really need is a way of just sending MainWindow::Redraw() from inside any function and having a single connect() inside Mainwindow to receive them. But you can't make a signal static and dialogs obviously don't inherit from MainWindow.

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• Dynamically find other hosts in a LAN in Java

  - by Federico Cristina

  A while ago I developed a little LAN chat app. in Java which allows chatting with other hosts, send images, etc. Although it was created just for fun, now it's being used where I work. Currently, there is no "chat server" on the app. where each client registers, updates it's status, etc. (I liked the idea of symmetric design and not depending on a server running on some other machine). Instead, each host is a client/server which has a hosts.properties file with the hostname of the other hosts, and - for instance - broadcasts to each one of them when sending a massive message/image/whatever. In the beginning there were just a couple of hosts, so this hosts.properties file wasn't an issue. But as the amount of users increased, the need of updating that file was a bit daunting. So now I've decided to get rid of it, and each time the app. starts, dynammically find the other active hosts. However, I cannot find the correct way of implement this. I've tried starting different threads, each one of them searching for other hosts in a known range of IP addresses. Something like this (simplified for the sake of readability): /** HostsLocator */ public static void searchForHosts(boolean waitToEnd) { for (int i=0; i < MAX_IP; i+= MAX_IP / threads) { HostsLocator detector = new HostsLocator(i, i+(MAX_IP / threads - 1)); // range: from - to new Thread(detector).start(); } } public void run() { for (int i=from; i<=to; i++) findHosts( maskAddress + Integer.toString(i) ); } public static boolean findHosts(String IP) { InetAddress address = InetAddress.getByName(IP); if ( address.isReachable(CONNECTION_TIME_OUT) ) // host found! } However: With a single thread and a low value in CONNECTION_TIME_OUT (500ms) I get wrong Host Not Found status for for hosts actually active. With a high value in CONNECTION_TIME_OUT (5000ms) and only one single thread takes forever to end With several threads I've also found problems similar like the first one, due to collisions. So... I guess there's a better way of solving this problem but I couldn't find it. Any advice? Thanks!

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• Call .net function from PHP page.

  - by stacker

  I have this function in .net code: public class StringGenerator { public static string GenerateString(string hash) { return hash.GetHashCode(); } } I want to be able to call this from PHP page. Any idea how?

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• How do I determine if a property was overriden?

  - by Benjamin

  Hello I am doing a project that where I need to register all the properties, because of the system being so huge it would require a lot of work to register all the properties that i want to be dependent for the purpose of Xaml. The goal is to find all properties that are on the top of the tree. so basically public class A{ public int Property1 { get; set; } } public class B : A{ public int Property2 { get; set; } public virtual int Property3 { get; set; } } public class C : B{ public override int Property3 { get; set; } public int Property4 { get; set; } public int Property5 { get; set; } } The end result would be something like this A.Prorperty1 B.Property2 B.Property3 C.Property4 C.Property5 If you notice I don't want to accept overridden properties because of the way I search for the properties if I do something like this C.Property3 for example and it cannot find it it will check C's basetype and there it will find it. This is what I have so far. public static void RegisterType( Type type ) { PropertyInfo[] properties = type.GetProperties( BindingFlags.Public | BindingFlags.Instance | BindingFlags.DeclaredOnly | BindingFlags.GetProperty | BindingFlags.SetProperty ); if ( properties != null && properties.Length > 0 ) { foreach ( PropertyInfo property in properties ) { // if the property is an indexers then we ignore them if ( property.Name == "Item" && property.GetIndexParameters().Length > 0 ) continue; // We don't want Arrays or Generic Property Types if ( (property.PropertyType.IsArray || property.PropertyType.IsGenericType) ) continue; // Register Property } } } What I want are the following: Public properties, that are not overridden, not static, not private Either get and set properties are allowed They are not an array or a generic type They are the top of the tree ie C class in the example is the highest (The property list example is exactly what I am looking for) They are not an indexer property ( this[index] ) Any help will be much appreciated =).

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• Java program grading

  - by pasito15

  I've been working on this program for hours and I can't figure out how to get the program to actually print the grades from the scores Text file public class Assign7{ private double finalScore; private double private_quiz1; private double private_quiz2; private double private_midTerm; private double private_final; private final char grade; public Assign7(double finalScore){ private_quiz1 = 1.25; private_quiz2 = 1.25; private_midTerm = 0.25; private_final = 0.50; if (finalScore >= 90) { grade = 'A'; } else if (finalScore >= 80) { grade = 'B'; } else if (finalScore >= 70) { grade = 'C'; } else if (finalScore>= 60) { grade = 'D'; } else { grade = 'F'; } } public String toString(){ return finalScore+":"+private_quiz1+":"+private_quiz2+":"+private_midTerm+":"+private_final; } } this code compiles as well as this one import java.util.*; import java.io.*; public class Assign7Test{ public static void main(String[] args)throws Exception{ int q1,q2; int m = 0; int f = 0; int Record ; String name; Scanner myIn = new Scanner( new File("scores.txt") ); System.out.println( myIn.nextLine() +" avg "+"letter"); while( myIn.hasNext() ){ name = myIn.next(); q1 = myIn.nextInt(); q2 = myIn.nextInt(); m = myIn.nextInt(); f = myIn.nextInt(); Record myR = new Record( name, q1,q2,m,f); System.out.println(myR); } } public static class Record { public Record() { } public Record(String name, int q1, int q2, int m, int f) { } } } once a compile the code i get this which dosent exactly compute the numbers I have in the scores.txt Name quiz1 quiz2 midterm final avg letter Assign7Test$Record@4bcc946b Assign7Test$Record@642423 Exception in thread "main" java.until.InputMismatchException at java.until.Scanner.throwFor(Unknown Source) at java.until.Scanner.next(Unknown Source) at java.until.Scanner.nextInt(Unknown Source) at java.until.Scanner.nextInt(Unknown Source) at Assign7Test.main(Assign7Test.java:25)

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