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  • JavaEE: Question about design

    - by Harry Pham
    I have a JSF page that will create a new Comment. I have the managed bean of that page to be RequestScoped managed bean. @ManagedBean(name="PostComment") @RequestScoped public class PostComment { private Comment comment = null; @ManagedProperty(value="#{A}") private A a; //A is a ViewScoped Bean @ManagedProperty(value="#{B}") private B b; //B is a ViewScoped Bean @PostConstruct public void init(){ comment = new Comment(); } // setters and getters for comment and all the managed property variable public void postComment(String location){ //persist the new comment ... if(location.equals("A")){ //update the comment list on page A }else if(location.equals("B")){ //update the comment list on page B } } } As you can see from the code above, 2 ViewScoped bean A and B will both use method postComment(), and getter getComment() from bean PostComment. The problem I am having right now is that, if I am on A, constructor of A will load, but it will also load constructor of bean B. This make my page load twice as slow. What would be the best way to solve this problem?

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  • SQL Databases and table design/organization

    - by John McMullen
    (NOOB disclaimer) I'm working on a system (a type of map), that is accessed mostly via 3 fields: ID (auto incremented), X coordinate, and Y coordinate. As it is right now, i have all data on the map, stored in 1 table. Whenever the map display is loaded it simply queries the database for contents in x and y, and the DB gives the data (other fields in the same entry). If an item on the map is doing something, it has a flag saying its doing something, and then has an ID of the action in another table holding that type of 'actions'. Essentially, for all map data, its stored in 1 table. All actions of a certain type are stored in their own table. I'm a noob, and i'm wondering what the most effective/efficient structure for such a design? (a map that has items, and each item has stats/actions). I'm using PHP atm, using standard SQL queries to get my data. Should i split up the tables so that there are only x number of entries on a table? (coord range limits)? Should it just keep growing and growing? There's a lot of queries to the table... so just tryin to see what is best :/

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  • C# Virtual method call in constructor - how to refactor?

    - by Cristi Diaconescu
    I have an abstract class for database-agnostic cursor actions. Derived from that, there are classes that implement the abstract methods for handling database-specific stuff. The problem is, the base class ctor needs to call an abstract method - when the ctor is called, it needs to initialize the database-specific cursor. I know why this shouldn't be done, I don't need that explanation! This is my first implementation, that obviously doesn't work - it's the textbook "wrong way" of doing it. The overridden method accesses a field from the derived class, which is not yet instantiated: public abstract class CursorReader { private readonly int m_rowCount; protected CursorReader() { m_rowCount = CreateCursor(sqlCmd); //virtual call ! } protected abstract int CreateCursor(string sqlCmd); } public class SqlCursorReader : CursorReader { private SqlConnection m_sqlConnection; public SqlCursorReader(string sqlCmd, SqlConnection sqlConnection) { m_sqlConnection = sqlConnection; //field initialized here } protected override int CreateCursor(string sqlCmd) { //uses not-yet-initialized member *m_sqlConnection* //so this throws a NullReferenceException var cursor = new CustomCursor(sqlCmd, m_sqlConnection); return cursor.Count(); } } I will follow up with an answer on my attempts to fix this...

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  • OptimisticLockException in inner transaction ruins outer transaction

    - by Pace
    I have the following code (OLE = OptimisticLockException)... public void outer() { try { middle() } catch (OLE) { updateEntities(); outer(); } } @Transactional public void middle() { try { inner() } catch (OLE) { updateEntities(); middle(); } @Transactional public void inner() { //Do DB operation } inner() is called by other non-transactional methods which is why both middle() and inner() are transactional. As you can see, I deal with OLEs by updating the entities and retrying the operation. The problem I'm having is that when I designed things this way I was assuming that the only time one could get an OLE was when a transaction closed. This is apparently not the case as the call to inner() is throwing an OLE even when the stack is outer()->middle()->inner(). Now, middle() is properly handling the OLE and the retry succeeds but when it comes time to close the transaction it has been marked rollbackOnly by Spring. When the middle() method call finally returns the closing aspect throws an exception because it can't commit a transaction marked rollbackOnly. I'm uncertain what to do here. I can't clear the rollbackOnly state. I don't want to force create a transaction on every call to inner because that kills my performance. Am I missing something or can anyone see a way I can structure this differently? EDIT: To clarify what I'm asking, let me explain my main question. Is it possible to catch and handle OLE if you are inside of an @Transactional method? FYI: The transaction manager is a JpaTransactionManager and the JPA provider is Hibernate.

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  • Java HashMap containsKey always false

    - by Dennis
    I have the funny situation, that I store a Coordinate into a HashMap<Coordinate, GUIGameField>. Now, the strange thing about it is, that I have a fragment of code, which should guard, that no coordinate should be used twice. But if I debug this code: if (mapForLevel.containsKey(coord)) { throw new IllegalStateException("This coordinate is already used!"); } else { ...do stuff... } ... the containsKey always returns false, although I stored a coordinate with a hashcode of 9731 into the map and the current coord also has the hashcode 9731. After that, the mapForLevel.entrySet() looks like: (java.util.HashMap$EntrySet) [(270,90)=gui.GUIGameField@29e357, (270,90)=gui.GUIGameField@ca470] What could I have possibly done wrong? I ran out of ideas. Thanks for any help! public class Coordinate { int xCoord; int yCoord; public Coordinate(int x, int y) { ...store params in attributes... } ...getters & setters... @Override public int hashCode() { int hash = 1; hash = hash * 41 + this.xCoord; hash = hash * 31 + this.yCoord; return hash; } }

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  • Cakephp Search Plugin: DateTime Range

    - by Chris
    I am trying to search a model by dates using the CakePHP Search plugin The idea is: The user enters a date of a flight and the engine returns all flights within +- one day of that. My form: <?php echo $form->create('Flight', array( 'url' => array_merge(array('action' => 'find'), $this->params['pass']) )); echo $form->input('departure', array('div' => false, 'dateFormat' => 'DMY','timeFormat' => 'NONE')); echo $form->submit(__('Search', true), array('div' => false)); echo $form->end(); ?> My flight model: public $filterArgs = array( array('name' => 'departure', 'type' => 'expression', 'method' => 'makeRangeCondition', 'field' => 'ABS((TO_Days(Flight.departure))-( TO_Days(?))) < 2') ); The controller: public $presetVars = array( array('field' => 'departure', 'type' => 'expression') ); public function find() { $this->Prg->commonProcess(); $this->paginate['conditions'] = $this->Flight->parseCriteria($this->passedArgs); $this->set('flights', $this->paginate()); } When I try to search, the values for departure are packed in an array; Array ([departure] => Array ) And the filterArgs(...) function doesn't seem to understand this. What is the correct way to do this?

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  • Relative path in JLabel HTML

    - by kroiz
    Hi, I am trying to make JLabel show an html which is referencing an image using a relative path. But I cannot make JLabel locate the image. It works fine when I am using absolute path. I have tried running the program from the command line or from eclipse and add dialog to show me where is the current working directory but for avail. I have therefor came to the conclusion that the image is not searched in the current directory - which brings me to the point. where is the image looked for? here is a test code that show what I am doing: import javax.swing.*; public class HTMLLabel extends JFrame { public HTMLLabel() { setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); JOptionPane.showMessageDialog( this, System.getProperty("user.dir")); String html = "<html>\n" + " <body>\n" + " <div style=\"text-align: center;\">\n" + " <img src=\"file://s.png\">\n"+ " </div>\n"+ " </body>\n"+ "</html>"; JLabel label = new JLabel(html); add(label); pack(); setVisible(true); } public static void main(String[] args) { new HTMLLabel(); } }

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  • Visual Studio 2008 Installer, Custom Action. Breakpoint not firing.

    - by Snake
    Hi, I've got an installer with a custom action project. I want the action to fire at install. The action fires, when I write something to the event log, it works perfectly. But I really need to debug the file since the action is quite complicated. So I've got the following installer class: namespace InstallerActions { using System; using System.Collections; using System.Collections.Generic; using System.ComponentModel; using System.Configuration.Install; using System.Diagnostics; using System.IO; [RunInstaller(true)] // ReSharper disable UnusedMember.Global public partial class DatabaseInstallerAction : Installer // ReSharper restore UnusedMember.Global { public DatabaseInstallerAction() { InitializeComponent(); } public override void Install(IDictionary stateSaver) { base.Install(stateSaver); System.Diagnostics.Debugger.Launch(); System.Diagnostics.Debugger.Break(); // none of these work Foo(); } private static void Foo() { } } } The installer just finalizes without warning me, it doesn't break, it doesn't ask me to attach a debugger. I've tried debug and release mode. Am I missing something? Thanks -Snake

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  • android view web pictures in gallery

    - by bitma
    I am new to android, I just finished Hello gallery tutorial, and a web pciture tutorial. Now I want to know how can I show some web images in gallery? the hello gallery code is from andorid tutor this is Web gallery code, I want to load some pictures from web and then show them in gallery, how can I write it? public class WebGallery extends Activity { String imageUrl = "http://i.pbase.com/o6/92/229792/1/80199697.uAs58yHk.50pxCross_of_the_Knights_Templar_svg.png"; Bitmap bmImg; ImageView imView; public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main); imView = (ImageView) findViewById(R.id.imview); imView.setImageBitmap(getRemoteImage(imageUrl)); } public Bitmap getRemoteImage(String imageUrl) { try { URL aURL = new URL(imageUrl); final URLConnection conn = aURL.openConnection(); conn.connect(); final BufferedInputStream bis = new BufferedInputStream(conn.getInputStream()); final Bitmap bm = BitmapFactory.decodeStream(bis); bis.close(); return bm; } catch (IOException e) { Log.d("DEBUGTAG", "Oh noooz an error..."); } return null; } }

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  • Delete only reference to child object

    - by Al
    I'm running in to a bit of a problem where any attempt to delete just the reference to a child also deletes the child record. My schema looks like this Person Organisation OrganisationContacts : Person OrgId PersonId Role When removing an Organisation i want to only delete the record in OrgnaisationContacts, but not touch the Person record. My Mapping looks like this Code: public OrganisationMap() { Table("Organsations"); .... HasMany<OrganisationContact>(x => x.Contacts) .Table("OrganisationContacts ") .KeyColumn("OrgId") .Not.Inverse() .Cascade.AllDeleteOrphan(); } public class OrganisationContactMap : SubclassMap<OrganisationContact> { public OrganisationContactMap() { Table("OrganisationContacts"); Map(x => x.Role, "PersonRole"); Map(x => x.IsPrimary); } } At the moment just removing a contact from the IList either doesn't reflect in the database at all, or it issues two delete statements DELETE FROM OrganisationContact & DELETE FROM Person, or tries to set PersonId to null in the OrganisationContacts table. All of which are not desirable. Any help would be great appreciated.

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  • Constructor Overload Problem in C++ Inheritance

    - by metdos
    Here my code snippet: class Request { public: Request(void); ……….. } Request::Request(void) { qDebug()<<"Request: "<<"Hello World"; } class LoginRequest :public Request { public: LoginRequest(void); LoginRequest(QDomDocument); …………… } LoginRequest::LoginRequest(void) { qDebug()<<"LoginRequest: "<<"Hello World"; requestType=LOGIN; requestId=-1; } LoginRequest::LoginRequest(QDomDocument doc){ qDebug()<<"LoginRequest: "<<"Hello World with QDomDocument"; LoginRequest::LoginRequest(); xmlDoc_=doc; } When call constructor of Overrided LoginRequest LoginRequest *test=new LoginRequest(doc); I came up with this result: Request: Hello World LoginRequest: Hello World with QDomDocument Request: Hello World LoginRequest: Hello World Obviously both constructor of LoginRequest called REquest constructor. Is there any way to cape with this situation? I can construct another function that does the job I want to do and have both constructors call that function. But I wonder is there any solution?

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  • Multi-Column Join in Hibernate/JPA Annotations

    - by bowsie
    I have two entities which I would like to join through multiple columns. These columns are shared by an @Embeddable object that is shared by both entities. In the example below, Foo can have only one Bar but Bar can have multiple Foos (where AnEmbeddableObject is a unique key for Bar). Here is an example: @Entity @Table(name = "foo") public class Foo { @Id @Column(name = "id") @GeneratedValue(generator = "seqGen") @SequenceGenerator(name = "seqGen", sequenceName = "FOO_ID_SEQ", allocationSize = 1) private Long id; @Embedded private AnEmbeddableObject anEmbeddableObject; @ManyToOne(targetEntity = Bar.class, fetch = FetchType.LAZY) @JoinColumns( { @JoinColumn(name = "column_1", referencedColumnName = "column_1"), @JoinColumn(name = "column_2", referencedColumnName = "column_2"), @JoinColumn(name = "column_3", referencedColumnName = "column_3"), @JoinColumn(name = "column_4", referencedColumnName = "column_4") }) private Bar bar; // ... rest of class } And the Bar class: @Entity @Table(name = "bar") public class Bar { @Id @Column(name = "id") @GeneratedValue(generator = "seqGen") @SequenceGenerator(name = "seqGen", sequenceName = "BAR_ID_SEQ", allocationSize = 1) private Long id; @Embedded private AnEmbeddableObject anEmbeddableObject; // ... rest of class } Finally the AnEmbeddedObject class: @Embeddable public class AnEmbeddedObject { @Column(name = "column_1") private Long column1; @Column(name = "column_2") private Long column2; @Column(name = "column_3") private Long column3; @Column(name = "column_4") private Long column4; // ... rest of class } Obviously the schema is poorly normalised, it is a restriction that AnEmbeddedObject's fields are repeated in each table. The problem I have is that I receive this error when I try to start up Hibernate: org.hibernate.AnnotationException: referencedColumnNames(column_1, column_2, column_3, column_4) of Foo.bar referencing Bar not mapped to a single property I have tried marking the JoinColumns are not insertable and updatable, but with no luck. Is there a way to express this with Hibernate/JPA annotations? Thank you.

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  • how to merge ecommerce transaction data between two databases

    - by yamspog
    We currently run an ecommerce solution for a leisure and travel company. Everytime we have a release, we must bring the ecommerce site down as we update database schema and the data access code. We are using a custom built ORM where each data entity is responsible for their own CRUD operations. This is accomplished by dynamically generating the SQL based on attributes in the data entity. For example, the data entity for an address would be... [tableName="address"] public class address : dataEntity { [column="address1"] public string address1; [column="city"] public string city; } So, if we add a new column to the database, we must update the schema of the database and also update the data entity. As you can expect, the business people are not too happy about this outage as it puts a crimp in their cash-flow. The operations people are not happy as they have to deal with a high-pressure time when database and applications are upgraded. The programmers are upset as they are constantly getting in trouble for the legacy system that they inherited. Do any of you smart people out there have some suggestions?

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  • Google App Engine django model form does not pick up BlobProperty

    - by Wes
    I have the following model: class Image(db.Model): auction = db.ReferenceProperty(Auction) image = db.BlobProperty() thumb = db.BlobProperty() caption = db.StringProperty() item_to_tag = db.StringProperty() And the following form: class ImageForm(djangoforms.ModelForm): class Meta: model = Image When I call ImageForm(), only the non-Blob fields are created, like this: <tr><th><label for="id_auction">Auction:</label></th><td><select name="auction" id="id_auction"> <option value="" selected="selected">---------</option> <option value="ahRoYXJ0bWFuYXVjdGlvbmVlcmluZ3INCxIHQXVjdGlvbhgKDA">2010-06-19 11:00:00</option> </select></td></tr> <tr><th><label for="id_caption">Caption:</label></th><td><input type="text" name="caption" id="id_caption" /></td></tr> <tr><th><label for="id_item_to_tag">Item to tag:</label></th><td><input type="text" name="item_to_tag" id="id_item_to_tag" /></td></tr> I want the Blob fields to be included in the form as well (as file inputs). What am I doing wrong?

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  • C++: Efficiently adding integers to strings

    - by Shinka
    I know how to add integers to strings, but I'm not sure I'm doing it in an efficient matters. I have a class where I often have to return a string plus an integer (a different integer each time), in Java I would do something like public class MyClass { final static String S = "MYSTRING"; private int id = 0; public String getString() { return S + (id++); } } But in C++ I have to do; class MyClass { private: std::string S; // For some reason I can't do const std::string S = "MYSTRING"; int id; public: MyClass() { S = "MYSTRING"; id = 0; } std::string getString() { std::ostringstream oss; oss << S << id++; return oss.str(); } } An additional constraint: I don't want (in fact, in can't) use Boost or any other librairies, I'll have to work with the standard library. So the thing is; the code works, but in C++ I have to create a bunch of ostringstream objects, so it seems inefficient. To be fair, perhaps Java do the same and I just don't notice it, I say it's inefficient mostly because I know very little about strings. Is there a more efficient way to do this ?

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  • Getting an exception when trying to use extension method with SortedDictionary... why?

    - by Polaris878
    I'm trying to place custom objects into a sorted dictionary... I am then trying to use an extension method (Max()) on this sorted dictionary. However, I'm getting the exception: "At least one object must implement IComparable". I don't understand why I'm getting that, as my custom object obviously implements IComparable. Here is my code: public class MyDate : IComparable<MyDate> { int IComparable<MyDate>.CompareTo(MyDate obj) { if (obj != null) { if (this.Value.Ticks < obj.Value.Ticks) { return 1; } else if (this.Value.Ticks == obj.Value.Ticks) { return 0; } else { return -1; } } } public MyDate(DateTime date) { this.Value = date; } public DateTime Value; } class Program { static void Main(string[] args) { SortedDictionary<MyDate, int> sd = new SortedDictionary<MyDate,int>(); sd.Add(new MyDate(new DateTime(1)), 1); sd.Add(new MyDate(new DateTime(2)), 2); Console.WriteLine(sd.Max().Value); // Throws exception!! } } What on earth am I doing wrong???

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  • Deserialize xml which uses attribute name/value pairs

    - by Bodyloss
    My application receives a constant stream of xml files which are more or less a direct copy of the database record <record type="update"> <field name="id">987654321</field> <field name="user_id">4321</field> <field name="updated">2011-11-24 13:43:23</field> </record> And I need to deserialize this into a class which provides nullable property's for all columns class Record { public long? Id { get; set; } public long? UserId { get; set; } public DateTime? Updated { get; set; } } I just cant seem to work out a method of doing this without having to parse the xml file manually and switch on the field's name attribute to store the values. Is their a way this can be achieved quickly using an XmlSerializer? And if not is their a more efficient way of parsing it manually? Regards and thanks My main problem is that the attribute name needs to have its value set to a property name and its value as the contents of a <field>..</field> element

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  • Efficient way to store order in mySQL for list of items

    - by ninumedia
    I want to code cleaner and more efficiently and I wanted to know any other suggestions for the following problem: I have a mySQL database that holds data about a set of photograph names. Oh, say 100 photograph names Table 1: (photos) has the following fields: photo_id, photo_name Ex data: 1 | sunshine.jpg 2 | cloudy.jpg 3 | rainy.jpg 4 | hazy.jpg ... Table 2: (categories) has the following fields: category_id, category_name, category_order Ex data: 1 | Summer Shots | 1,2,4 2 | Winter Shots | 2,3 3 | All Seasons | 1,2,3,4 ... Is it efficient to store the order of the photos in this manner per entry via comma delimited values? It's one approach I have seen used before but I wanted to know if something else is faster in run time. Using this way I don't think it is possible to do a direct INNER JOIN on the category table and photo table to get a single matched list of all the photographs per category. Ex: Summer shots - sunshine.jpg, cloudy.jpg, hazy.jpg because it was matched against 1,2,4 The iteration through all the categories and then the photos will have a O(n^2) and there has to be a better/faster way. Please educate me :)

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  • Static Vs Non-Static Method Performance C#

    - by dotnetguts
    Hello All, I have few global methods declared in public class in my asp.net web application. I have habbit of declaring all global methods in public class in following format public static string MethodName(parameters) { } I want to know how it would impact on performance point of view? 1) Which one is Better? Static Method or Non-Static Method? 2) Reason why it is better? Following link shows Non-Static methods are good because, static methods are using locks to be Thread-safe. The always do internally a Monitor.Enter() and Monitor.exit() to ensure Thread-safety. http://bytes.com/topic/c-sharp/answers/231701-static-vs-non-static-function-performance And Following link shows Static Methods are good static methods are normally faster to invoke on the call stack than instance methods. There are several reasons for this in the C# programming language. Instance methods actually use the 'this' instance pointer as the first parameter, so an instance method will always have that overhead. Instance methods are also implemented with the callvirt instruction in the intermediate language, which imposes a slight overhead. Please note that changing your methods to static methods is unlikely to help much on ambitious performance goals, but it can help a tiny bit and possibly lead to further reductions. http://dotnetperls.com/static-method I am little confuse which one to use? Thanks

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  • Help with Java Generics: Cannot use "Object" as argument for "? extends Object"

    - by AniDev
    Hello, I have the following code: import java.util.*; public class SellTransaction extends Transaction { private Map<String,? extends Object> origValueMap; public SellTransaction(Map<String,? extends Object> valueMap) { super(Transaction.Type.Sell); assignValues(valueMap); this.origValueMap=valueMap; } public SellTransaction[] splitTransaction(double splitAtQuantity) { Map<String,? extends Object> valueMapPart1=origValueMap; valueMapPart1.put(nameMappings[3],(Object)new Double(splitAtQuantity)); Map<String,? extends Object> valueMapPart2=origValueMap; valueMapPart2.put(nameMappings[3],((Double)origValueMap.get(nameMappings[3]))-splitAtQuantity); return new SellTransaction[] {new SellTransaction(valueMapPart1),new SellTransaction(valueMapPart2)}; } } The code fails to compile when I call valueMapPart1.put and valueMapPart2.put, with the error: The method put(String, capture#5-of ? extends Object) in the type Map is not applicable for the arguments (String, Object) I have read on the Internet about generics and wildcards and captures, but I still don't understand what is going wrong. My understanding is that the value of the Map's can be any class that extends Object, which I think might be redundant, because all classes extend Object. And I cannot change the generics to something like ? super Object, because the Map is supplied by some library. So why is this not compiling? Also, if I try to cast valueMap to Map<String,Object>, the compiler gives me that 'Unchecked conversion' warning. Thanks!

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  • How can I shared controller logic in ASP.NET MVC for 2 controllers, where they are overriden

    - by AbeP
    Hello, I am trying to implement user-friendly URLS, while keeping the existing routes, and was able to do so using the ActionName tag on top of my controller (http://stackoverflow.com/questions/436866/can-you-overload-controller-methods-in-asp-net-mvc) I have 2 controllers: ActionName("UserFriendlyProjectIndex")] public ActionResult Index(string projectName) { ... } public ActionResult Index(long id) { ... } Basically, what I am trying to do is I store the user-friendly URL in the database for each project. If the user enters the URL /Project/TopSecretProject/, the action UserFriendlyProjectIndex gets called. I do a database lookup and if everything checks out, I want to apply the exact same logic that is used in the Index action. I am basically trying to avoid writing duplicate code. I know I can separate the common logic into another method, but I wanted to see if there is a built-in way of doing this in ASP.NET MVC. Any suggestions? I tried the following and I go the View could not be found error message: [ActionName("UserFriendlyProjectIndex")] public ActionResult Index(string projectName) { var filteredProjectName = projectName.EscapeString().Trim(); if (string.IsNullOrEmpty(filteredProjectName)) return RedirectToAction("PageNotFound", "Error"); using (var db = new PIMPEntities()) { var project = db.Project.Where(p => p.UserFriendlyUrl == filteredProjectName).FirstOrDefault(); if (project == null) return RedirectToAction("PageNotFound", "Error"); return View(Index(project.ProjectId)); } } Here's the error message: The view 'UserFriendlyProjectIndex' or its master could not be found. The following locations were searched: ~/Views/Project/UserFriendlyProjectIndex.aspx ~/Views/Project/UserFriendlyProjectIndex.ascx ~/Views/Shared/UserFriendlyProjectIndex.aspx ~/Views/Shared/UserFriendlyProjectIndex.ascx Project\UserFriendlyProjectIndex.spark Shared\UserFriendlyProjectIndex.spark I am using the SparkViewEngine as the view engine and LINQ-to-Entities, if that helps. thank you!

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  • JPA/Hibernate Parent/Child relationship

    - by NubieJ
    Hi I am quite new to JPA/Hibernate (Java in general) so my question is as follows (note, I have searched far and wide and have not come across an answer to this): I have two entities: Parent and Child (naming changed). Parent contains a list of Children and Children refers back to parent. e.g. @Entity public class Parent { @Id @Basic @GeneratedValue(strategy = GenerationType.IDENTITY) @Column(name = "PARENT_ID", insertable = false, updatable = false) private int id; /* ..... */ @OneToMany(cascade = { CascadeType.ALL }, fetch = FetchType.LAZY) @JoinColumn(name = "PARENT_ID", referencedColumnName = "PARENT_ID", nullable = true) private Set<child> children; /* ..... */ } @Entity public class Child { @Id @Basic @GeneratedValue(strategy = GenerationType.IDENTITY) @Column(name = "CHILD_ID", insertable = false, updatable = false) private int id; /* ..... */ @ManyToOne(cascade = { CascadeType.REFRESH }, fetch = FetchType.EAGER, optional = false) @JoinColumn(name = "PARENT_ID", referencedColumnName = "PARENT_ID") private Parent parent; /* ..... */ } I want to be able to do the following: Retrieve a Parent entity which would contain a list of all its children (List), however, when listing Parent (getting List, it of course should omit the children from the results, therefore setting FetchType.LAZY. Retrieve a Child entity which would contain an instance of the Parent entity. Using the code above (or similar) results in two exceptions: Retrieving Parent: A cycle is detected in the object graph. This will cause infinitely deep XML... Retrieving Child: org.hibernate.LazyInitializationException: failed to lazily initialize a collection of role: xxxxxxxxxxx, no session or session was closed When retrieving the Parent entity, I am using a named query (i.e. calling it specifically) @NamedQuery(name = "Parent.findByParentId", query = "SELECT p FROM Parent AS p LEFT JOIN FETCH p.children where p.id = :id") Code to get Parent (i.e. service layer): public Parent findByParentId(int parentId) { Query query = em.createNamedQuery("Parent.findByParentId"); query.setParameter("id", parentId); return (Parent) query.getSingleResult(); } Why am I getting a LazyInitializationException event though the List property on the Parent entity is set as Lazy (when retrieving the Child entity)?

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  • Alternatives to static methods on interfaces for enforcing consistency

    - by jayshao
    In Java, I'd like to be able to define marker interfaces, that forced implementations to provide static methods. For example, for simple text-serialization/deserialization I'd like to be able to define an interface that looked something like this: public interface TextTransformable<T>{ public static T fromText(String text); public String toText(); Since interfaces in Java can't contain static methods though (as noted in a number of other posts/threads: here, here, and here this code doesn't work. What I'm looking for however is some reasonable paradigm to express the same intent, namely symmetric methods, one of which is static, and enforced by the compiler. Right now the best we can come up with is some kind of static factory object or generic factory, neither of which is really satisfactory. Note: in our case our primary use-case is we have many, many "value-object" types - enums, or other objects that have a limited number of values, typically carry no state beyond their value, and which we parse/de-parse thousands of time a second, so actually do care about reusing instances (like Float, Integer, etc.) and its impact on memory consumption/g.c. Any thoughts?

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  • Keeping updated with the latest technologies.

    - by Prashanth
    I am a software developer and I have been programming since the past six years. I simply love the mental challenge involved in trying to come up with solutions to hard problems, reading up programming literature, blogs by prominent developers and so on. I work on Microsoft platform and I have trouble keeping up with the pace at which various frameworks are rolled out. Remoting,WCF,ASP.NET,ASP.NET MVC, LINQ, WPF, WWF, OSLO, ADO.NET data services, DSL tools etc etc. Even understanding all these frameworks at an abstract level and see how they are all tied up with MS vision itself is a major hurdle. Now when you add other non microsoft technologies, programming languages etc to the equation, I wonder how do people manage? Given that there are only 24 hours in a day, how does one keep himself updated about so many technology changes that happen everyday? My question is , is it even worth doing that? The thing is, I am also interested in other fields such as literature, science. I try my best to at least gain a superficial understanding of what is happening in other fields of my interest and don't want to give up on that :)

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  • Jquery Append() and remove() element

    - by BandonRandon
    Hi, I have a form where I'm dynamically adding the ability to upload files with the append function but I would also like to be able to remove unused fields. Here is the html markup <span class="inputname">Project Images: <a href="#" class="add_project_file"><img src="images/add_small.gif" border="0"></a></span> <span class="project_images"> <input name="upload_project_images[]" type="file" /><br/> </span> Right now if they click on the "add" gif a new row is added with this jquery $('a.add_project_file').click(function() { $(".project_images").append('<input name="upload_project_images[]" type="file" class="new_project_image" /> <a href="#" class="remove_project_file" border="2"><img src="images/delete.gif"></a><br/>'); return false; }); To remove the input box i've tried to add the class "remove_project_file" then add this function. $('a.remove_project_file').click(function() { $('.project_images').remove(); return false;}); I think there should be a much easier way to do this. Maybe i need to use the $(this) function for the remove. Another possible solution would be to expand the "add project file" to do both adding and removing fields. Any of you JQuery wizards have any ideas that would be great

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