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  • OOP Design Question - Where/When do you Validate properties?

    - by JW
    I have read a few books on OOP DDD/PoEAA/Gang of Four and none of them seem to cover the topic of validation - it seems to be always assumed that data is valid. I gather from the answers to this post (http://stackoverflow.com/questions/1651964/oop-design-question-validating-properties) that a client should only attempt to set a valid property value on a domain object. This person has asked a similar question that remains unanswered: http://bytes.com/topic/php/answers/789086-php-oop-setters-getters-data-validation#post3136182 So how do you ensure it is valid? Do you have a 'validator method' alongside every getter and setter? isValidName() setName() getName() I seem to be missing some key basic knowledge about OOP data validation - can you point me to a book that covers this topic in detail? - ie. covering different types of validation / invariants/ handling feedback / to use Exceptions or not etc

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  • Spring @Autowired and WebApplicationContext in Tomcat

    - by EugeneP
    @Autowired works only once. What to do to make it wire the bean every time the Servlet is recreated? My web-app (Tomcat6 container) consists of 2 Servlets. Every servlet has private fields. Their setters are marked with @Autowired In the init method I use WebApplicationContextUtils ... autowireBean(this); It autowires the properties marked with @Autowired once - during the initialization of the Servlet. Any other session will see these fields values, they will not be rewired after the previous session is destroyed. What to do to make them rewire them each time a Servlet constructor is called? a) Put the autowiring into the constructor? Or better 2) get a web app context and extract a bean from there?

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  • Jackson - suppressing serialization(write) of properties dynamically

    - by kapil.israni
    I am trying to convert java object to JSON object in Tomcat/jersey using Jackson. And want to suppress serialization(write) of certain properties dynamically. I can use JsonIgnore, but I want to make the ignore decision at runtime. Any ideas?? So as an example below, I want to suppress "id" field when i serialize the User object to JSON.. new ObjectMapper.writeValueAsString(user); class User { private String id = null; private String firstName = null; private String lastName = null; //getters //setters }//end class

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  • Approaches for generic, compile-time safe lazy-load methods

    - by Aaronaught
    Suppose I have created a wrapper class like the following: public class Foo : IFoo { private readonly IFoo innerFoo; public Foo(IFoo innerFoo) { this.innerFoo = innerFoo; } public int? Bar { get; set; } public int? Baz { get; set; } } The idea here is that the innerFoo might wrap data-access methods or something similarly expensive, and I only want its GetBar and GetBaz methods to be invoked once. So I want to create another wrapper around it, which will save the values obtained on the first run. It's simple enough to do this, of course: int IFoo.GetBar() { if ((Bar == null) && (innerFoo != null)) Bar = innerFoo.GetBar(); return Bar ?? 0; } int IFoo.GetBaz() { if ((Baz == null) && (innerFoo != null)) Baz = innerFoo.GetBaz(); return Baz ?? 0; } But it gets pretty repetitive if I'm doing this with 10 different properties and 30 different wrappers. So I figured, hey, let's make this generic: T LazyLoad<T>(ref T prop, Func<IFoo, T> loader) { if ((prop == null) && (innerFoo != null)) prop = loader(innerFoo); return prop; } Which almost gets me where I want, but not quite, because you can't ref an auto-property (or any property at all). In other words, I can't write this: int IFoo.GetBar() { return LazyLoad(ref Bar, f => f.GetBar()); // <--- Won't compile } Instead, I'd have to change Bar to have an explicit backing field and write explicit getters and setters. Which is fine, except for the fact that I end up writing even more redundant code than I was writing in the first place. Then I considered the possibility of using expression trees: T LazyLoad<T>(Expression<Func<T>> propExpr, Func<IFoo, T> loader) { var memberExpression = propExpr.Body as MemberExpression; if (memberExpression != null) { // Use Reflection to inspect/set the property } } This plays nice with refactoring - it'll work great if I do this: return LazyLoad(f => f.Bar, f => f.GetBar()); But it's not actually safe, because someone less clever (i.e. myself in 3 days from now when I inevitably forget how this is implemented internally) could decide to write this instead: return LazyLoad(f => 3, f => f.GetBar()); Which is either going to crash or result in unexpected/undefined behaviour, depending on how defensively I write the LazyLoad method. So I don't really like this approach either, because it leads to the possibility of runtime errors which would have been prevented in the first attempt. It also relies on Reflection, which feels a little dirty here, even though this code is admittedly not performance-sensitive. Now I could also decide to go all-out and use DynamicProxy to do method interception and not have to write any code, and in fact I already do this in some applications. But this code is residing in a core library which many other assemblies depend on, and it seems horribly wrong to be introducing this kind of complexity at such a low level. Separating the interceptor-based implementation from the IFoo interface by putting it into its own assembly doesn't really help; the fact is that this very class is still going to be used all over the place, must be used, so this isn't one of those problems that could be trivially solved with a little DI magic. The last option I've already thought of would be to have a method like: T LazyLoad<T>(Func<T> getter, Action<T> setter, Func<IFoo, T> loader) { ... } This option is very "meh" as well - it avoids Reflection but is still error-prone, and it doesn't really reduce the repetition that much. It's almost as bad as having to write explicit getters and setters for each property. Maybe I'm just being incredibly nit-picky, but this application is still in its early stages, and it's going to grow substantially over time, and I really want to keep the code squeaky-clean. Bottom line: I'm at an impasse, looking for other ideas. Question: Is there any way to clean up the lazy-loading code at the top, such that the implementation will: Guarantee compile-time safety, like the ref version; Actually reduce the amount of code repetition, like the Expression version; and Not take on any significant additional dependencies? In other words, is there a way to do this just using regular C# language features and possibly a few small helper classes? Or am I just going to have to accept that there's a trade-off here and strike one of the above requirements from the list?

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  • Can I get an example please?

    - by Doug
    $starcraft = array( "drone" => array( "cost" => "6_0-", "gas" => "192", "minerals" => "33", "attack" => "123", ) "zealot" => array( "cost" => "5_0-", "gas" => "112", "minerals" => "21", "attack" => "321", ) ) I'm playing with oop and I want to display the information in this array using a class, but I don't know how to construct the class to display it. This is what I have so far, and I don't know where to go from here. Am I supposed to use setters and getters? class gamesInfo($game) { $unitname; $cost; $gas; $minerals; $attack; }

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  • When to release the model(representedObject) of the corresponding UIViewController.

    - by user313786
    Hi, In AppKit we have "representedObject" available through NSViewController, this representedObject is generally set to ModelController or the model which the NSViewController displays, this works great with bindings as you just set the new representedObject and model details are updated in the view, BUT in case of iPhone (UIKit, with NO Cocoa bindings available), there is no such representedObject in UIViewController so here are few things I am interested in knowing:- What is the best/recommended way of binding the model to the UIViewController?, preferably dont want to maintain lot of IBOutlets and calls setters to updated the changed model data for display in view. How/When should the related model of the UIViewController be released? When is the -[UIViewController dealloc] called, in the typical iPhone application. Am looking for architecting some classes so that the UIViewController coordinates between the view and the model, but at the same time, deallocs the model when ever not necessary. TIA.

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  • DataContext Refresh and PropertyChanging & PropertyChanged Events

    - by Scott
    I'm in a situation where I am being informed from an outside source that a particular entity has been altered outside my current datacontext. I'm able to find the entity and call refresh like so MyDataContext.Refresh(RefreshMode.OverwriteCurrentValues, myEntity); and the properties which have been altered on the entity are updated correctly. However neither of the INotifyPropertyChanging INotifyPropertyChanged appear to be raised when the refresh occurs and this leaves my UI displaying incorrect information. I'm aware that Refresh() fails to use the correct property getters and setters on the entity to raise the change notification events, but perhaps there is another way to accomplish the same thing? Am I doing something wrong? Is there a better method than Refresh? If Refresh is the only option, does anyone have a work around?

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  • WCF DataContract with readonly properties

    - by Asaf R
    I'm trying to return a complex type from a service method in WCF. I'm using C# and .NET 4. This complex type is meant to be invariant (the same way .net strings are). Furthermore, the service only returns it and never recieves it as an argument. If I try to define only getters on properties I get a run time error. I guess this is because no setters causes serialization to fail. Still, I think this type should be invariant. Example: [DataContract] class A { [DataMember] int ReadOnlyProperty {get; private set;} } The service fails to load due to a problem with serialization. Is there a way to make readonly properties on a WCF DataContract? Perhaps by replacing the serializer? If so, how? If not, what would you suggest for this problem? Thanks, Asaf

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  • How to write a Custom DesignerSerializer for an class used by a Activity (WF)

    - by Stefan Steinegger
    I have a type which is used in a WF activity. It should be serialized. It doesn't work out of the box, most probably because of the private setters in that type. I'm not sure if this is the correct way, but I tried to write my own serializer and declared it on my class. [DesignerSerializer( typeof(FooDesignerSerializer), // my custom serializer typeof(WorkflowMarkupSerializer))] public class Foo { public Foo(int value, string name { // ... } public int Value { get; private set; } public string Name { get; private set; } } Is this the easiest way to get it serialized? How do I write this serializer? That's what I got so far: public class FooDesignerSerializer : WorkflowMarkupSerializer { protected override string SerializeToString( WorkflowMarkupSerializationManager serializationManager, object value) { // how to create a valid / XOML-like string? } }

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  • Javax Swing Timer Help

    - by kap
    Hello Guys, I am having some problems concerning starting javax.swing.Timer after a mouse click. I want to start the timer to perform some animation after the user clicks on a button but it is not working. Here are the code snippets: public class ShowMe extends JPanel{ private javax.swing.Timer timer; public ShowMe(){ timer = new javax.swing.Timer(20, new MoveListener()); } // getters and setters here private class MoveListener implements ActionListener { public void actionPerformed(ActionEvent e) { // some code here to perform the animation } } } This is the class which contains a button so that when the user clicks on the button the timer starts to begin the animation public class Test{ // button declarations go here and registering listeners also here public void actionPerformed(ActionEvent e) { if(e.getSource() == this.btnConnect){ ShowMe vis = new ShowMe(); vis.getTimer().start(); } } } I want to start the timer to begin the animation but it is not working. Need help how to make a timer start after button click. Thanks.

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  • Problem updating blog with hibernate?

    - by johnsmith51
    hi, i am having problem updating a blob with hibernate. my model have these getters/setters for hibernate, i.e. internally i deal with byte[] so any getter/setter convert the byte[] to blog. I can create an initial object without problem, but if I try to change the content of the blob, the database column is not updated. I do not get any error message, everything looks fine, except that the database is not updated. /** do not use, for hibernate only */ public Blob getLogoBinaryBlob() { if(logoBinary == null){ return null; } return Hibernate.createBlob(logoBinary); } /** do not use, for hibernate only */ public void setLogoBinaryBlob(Blob logoBinaryBlob) { ByteArrayOutputStream baos = new ByteArrayOutputStream(); try { logoBinary = toByteArrayImpl(logoBinaryBlob, baos); } catch (Exception e) { } }

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  • Spring: Inject static member (System.in) via constructor

    - by Julian Lettner
    I wrote some sort of console client for a simple application. To be more flexible, I thought it would be nice to only depend on java.io.Input-/OutputStream, instead of accessing System.in/out directly. I renamed the class ConsoleClient to StreamClient, added setters and made sure that the instance fields are used instead of System.in/out. At the moment my client code looks like this: ApplicationContext appCtx = new ClassPathXmlApplicationContext("..."); StreamClient cc = (StreamClient) appCtx.getBean("streamClient"); cc.setInputStream(System.in); cc.setOutputStream(System.out); cc.run(); // start client Question: Is there a way to move lines 3 and 4 into the Spring configuration (preferably constructor injection)? Thanks for your time.

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  • Core Data => Adding a related object always nil

    - by mongeta
    Hello, I have two tables related: DataEntered and Model DataEntered -currentModel Model One DataEntered can have only ONE Model, but a Model can stay into many DataEntered. The relationship is from DataEntered to Model (No To Many-relathionship) and no inverse relation. XCode generates the setters for DataEnteredModel: @property (nonatomic, retain) NSSet * current_model; - (void)addCurrent_modelObject:(CarModel *)value; - (void)addCurrent_model:(NSSet *)value; I have a Table and when I select a model, I want to store it to DataEntered: Model *model = [fetchedResultsController objectAtIndexPath:indexPath]; NSLog(@"Model %@",model.name); // ==> gives me the correct model name [dataEntered addCurrent_modelObject:model]; // ==> always nil [dataEntered setCurrent_model:[fetchedResultsController objectAtIndexPath:indexPath]]; // the same, always nil what I'm doing wrong ????? thanks, r.

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  • Accessing E4X nodes having special characters in name without breaking binding chain in flex.

    - by Jonas
    I am using E4X to bind some values from xml in flex 3. There is a problem when xml tag's (or attribute's) name has special character in it: having xml content var xml:XML = <tag> <special-name att="val" /> </tag> special-name could not be accessed using xml.special-name.@att because it is interpreted as subtraction, on the other hand using square bracket notation xml['special-name'].@att breaks binding chain. Is there an elegant way to solve this (like special language syntax) without writing custom binding setters and listeners?

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  • Java: Best practices for turning foreign horror-code into clean API...?

    - by java.is.for.desktop
    Hello, everyone! I have a project (related to graph algorithms). It is written by someone else. The code is horrible: public fields, no getters/setters huge methods, all public some classes have over 20 fields some classes have over 5 constructors (which are also huge) some of those constructors just left many fields null (so I can't make some fields final, because then every second constructor signals errors) methods and classes rely on each other in both directions I have to rewrite this into a clean and understandable API. Problem is: I myself don't understand anything in this code. Please give me hints on analyzing and understanding such code. I was thinking, perhaps, there are tools which perform static code analysis and give me call graphs and things like this.

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  • Adding WCF service reference adds DataContract types too

    - by Avi Shilon
    Hi everybody, I've used Visual Studio's Add Service Reference feature to add a service (actually it is a workflow service, created in WF4 RC1, but I don't think this makes any difference), and it also added the DataContracts that the service uses. At first this seemed fine, because All I've had in the DataContracts was simply properties, with no implementations. But now I've added code in the constructor of one data contracts that initializes creates an instance of one of the properties that exposes a list of other DCs, and when I've updated the service reference via VS (2010 RC1), the implementation was not updated. What should I do? Should I use my DCs instead of the ones created by VS or should I use the ones VS created? I've noticed that the properties in the VS-generated DCs contain some additional logic for checking equality in the setters and they also implement some interfaces too (like IExtensibleDataObject and INotifyPropertyChanged) which might get handy I guess in the future (I'm not knowledgeable at WCF). Thank you for your time folks, Avi

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  • richfaces keepAlive not working

    - by Jurgen H
    I have a mediaOutput tag which, in its createContent attribute, requires the backing bean to be in a certain state. A list of values, which is filled in an init method, must be available. I therefore added a keepAlive tag for the whole backing bean. I now indeed see the backingBean in stead of some (richfaces) proxy bean, but the filled list is null again. How to make this possible? I checked that the init method was called and that the list is filled in in the init method. <a4j:keepAlive beanName="myBean" /> <a4j:mediaOutput createContent="#{myBean.writeChart}" ... /> The backing bean public class MyBean implements Serializable { public List list; public void init(ActionEvent event) { // call some resource to fill the list list = service.getItems(); } public void writeChart(final OutputStream out, final Object data) throws IOException { // list is null } // getters & setters }

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  • Should I use DTOs as my data models in MVVM?

    - by JonC
    I'm currently working on what will be my first real foray into using MVVM and have been reading various articles on how best to implement it. My current thoughts are to use my data models effectively as data transfer objects, make them serializable and have them exist on both the client and server sides. It seems like a logical step given that both object types are really just collections of property getters and setters and another layer in between seems like complete overkill. Obviously there would be issues with INotifyPropertyChanged not working correctly on the server side as there is no ViewModel to which to communicate, but as long as we are careful about constructing our proper domain model objects from data models in the service layer and not dealing the the data models on the server side I don't think it should be a big issue. I haven't found too much info about this approach in my reading, so I would like to know if this is a pretty standard thing, is this just assumed to be the de facto way of doing MVVM in a multi-tier environment? If I've got completely the wrong idea about things then thoughts on other approaches would be appreciated too.

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  • Display values inside a JList -

    - by sharon Hwk
    I have a method that returns a HashMap, and is defined as follows; public HashMap<Integer, Animal> allAnimal(){ return returnsAHashMap; } Animal will have the following values in its class: public Animal{ int animalID; String animalName; // i have declared getters/setters } I have a GUI screen which has a JList and it's defined as: l = new JList(); l.setModel(new AbstractListModel() { String[] v = new String[] {"animal id 1", "2", "3"}; public int getSize() { return v.length; } public Object getElementAt(int index) { return v[index]; } }); What I want to do is to display the AnimalID's in the JList. I need to find a way to call the allAnimal() method and display all its Animal Id's in the JList. How can i do this ?

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  • When exactly does a method have side effects?

    - by Kim
    As I always understood it, any change to the programs state (or anything to do with IO) is a side effect. It does not matter, whether the change occurs in a global variable or in a private field of the object the method is called on. It follows that all methods which do not return anything either do nothing at all or have a side effect. My confusion comes from one of our university's instructors (who is still a student and thus not omniscient yet;) ) telling me setters don't have side effects.

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  • A pragmatic view on private vs public

    - by Denis Gorbachev
    Hello everybody! I've always wondered on the topic of public, protected and private properties. My memory can easily recall times when I had to hack somebody's code, and having the hacked-upon class variables declared as private was always upsetting. Also, there were (more) times I've written a class myself, and had never recognized any potential gain of privatizing the property. I should note here that using public vars is not in my habit: I adhere to the principles of OOP by utilizing getters and setters. So, what's the whole point in these restrictions?

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  • Entity Framework 4: C# !(ReferenceEquals()) vs !=

    - by Eric J.
    Unless a class specifically overrides the behavior defined for Object, ReferenceEquals and == do the same thing... compare references. In property setters, I have commonly used the pattern private MyType myProperty; public MyType MyProperty { set { if (myProperty != value) { myProperty = value; // Do stuff like NotifyPropertyChanged } } } However, in code generated by Entity Framework, the if statement is replaced by if (!ReferenceEquals(myProperty, value)) Using ReferenceEquals is more explicit (as I guess not all C# programmers know that == does the same thing if not overridden). Is there any difference that's escaping me between the two if-variants? Are they perhaps accounting for the possibility that POCO designers may have overridden ==? In short, if I have not overridden ==, am I save using != instead of ReferencEquals()?

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  • save managed bean to notes document

    - by Ove Stoerholt
    In a managed bean you have fields, and the fields have getters and setters. But I also need to save values back to, in this case, a Notes profile document. So I have a loadProfileDocument and a saveProfileDocument method. I was thinking of using the bean in the application scope. How do I make sure the profile document is saved? Do I have to call the saveProfileDocument from the setter? Do I call the saveProfileDocument() explisitly? Could I use a destructor (finalize)? Or what...???...

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  • Spring security and Struts 2

    - by Thanksforfish
    I have a struts2 action with an @Secured({"ROLE_ADMIN"}) to secure the execute method. In the execute method i assign a message to a member variable of the action, then return SUCCESS and end up on the jsp page. On the page I retrieve the actions member variable with <sroperty. private String greeting; public String execute() throws Exception { this.greeting="Hello"; return SUCCESS; } // getters and setters for greeting ... <s:property value="greeting" /> The problem is when the secured annotation is present the jsp shows nothing for the member variable but when @Secured is removed the whole thing behaves properly and shows the message that was set into the member variable. It appears that the actual security is working ok but when enabled via the annotation the member variable (or maybe the instance of the action) is not making its way onto the value stack. I cant see any error messages.

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  • OO and Writing Drupal Modules

    - by Aaron
    Preface: Yes, I've read: http://drupal.org/node/547518 I am writing 'foo' module for Drupal6, where I am organizing the code in an OO fashion. There's a class called Foo that has a bunch of setters and accessors, and it is working quite well at abstracting some pretty nasty code and SQL. The question is is it common practice to expose a class for other modules, or is it better to wrap things in the more typical foo_myfnname()? For example, if I am writing the module's docs, should I tell people to do this: $foo = new Foo(); $something = $foo->get_something(); or tell them to call: foo_get_something(); which under the hood does: function foo_get_something() { $foo = new Foo(); return $foo->get_something(); }

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