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• Contexts and Dependency Injection(CDI)??

  - by Masa Sasaki

  WebLogic Server?????????????WebLogic Server????????6?20?????????37?WebLogic Server???@????????Contexts and Dependency Injection(CDI)?(?????????? Fusion Middleware?????? ?? ?)?????????????????Java EE 6????????CDI???????DI(Dependency Injection)?Java EE 5????????????????????CDI??DI????????????????????????????????????????????????????????CDI????????????????????(?????? Fusion Middleware?????? ??? ??) CDI?? ???????CDI???Java EE 6???????JSR299: Contexts Dependency Injection????? ?????Dependency Injection (??????)?Aspect-Oriented Programming (AOP)?Interception ??????????????????????????? CDI?????????????????????????????????????????????? ?????????????????????????????????????????? ?????????????????????????????????????????????? ???????????????????????????CDI?????????????? CDI?????????????2? ??1???CDI??????????Oracle WebLogic Server 12c????Java EE 6????????? ?????????????????2???beans.xml???????Web??????????WEB-INF/beans.xml? EJB??META-INF/beans.xml????????????CDI????????????????beans.xml???? ?????????????????????? Java EE 5?DI(Dependency Injection) Java EE 5??DI????????????????????????????????????? ?????????????????????????????????????????(@EJB? @Resource?@WebServiceRef)??? Java EE 6?CDI Java EE 6?CDI?????????????????@Inject???????????????? ???????????????????????????????????????????????????? @Qualifier????????????????? ?????????????????????????????????????????@Qualifier? ????????????·??????????????????????@JPN??????????? @Produce???????? ???????????????????? ????????·?????????????? CDI?????????????????????????????????·??????? ????????????????????????????????????????????? ???????????????? EL(Expression Language) ???????? EL????????????JSF?ManagedBean?????????????·?????????????? ??? Java EE 6?????????CDI???????????Java EE 5?DI????AOP??? ???????????????????DI, AOP???????????????? ?????????????CDI?????????????????????????????? ?????CDI?????????????????????????????????? ?????? WebLogic Server??? WebLogic Server?????????WebLogic Server?????! WebLogic Server??????(???????????) WebLogic Server???????? WebLogic Server??????

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• Refactor to Dependency Injection

  Further refine our Template Method example to use Dependency Injection

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• Passing List of Strings or Array of strings into Unity Injection Constructor (Config-Based)

  - by miguel

  I cannot seem to get unity working when attempting to pass in an array of strings into a constructor parameter list, while using XML configuration. When I try the following: <typeConfig ...> <constructor ...> <param ... parameterType="System.String[]"> <array> <value.../> <value.../> </array> </param> </constructor> </typeConfig> for a c'tor which looks like this: void Foo(string[] inputParams_){ ... } It always fails in Unity's FindConstructor(...) method stating that it cannot find a c'tor mathcing the parameter type of String.String Does anyone know how to pass an array of stings successfully into this type of c'tor? If not, how can I do so with a list of strings, if the c'tor were to accept an IList? Thanks!

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• Dependency Injection: Jetty 7

  - by Malax

  Hi StackOverflow! My application requires several interface implementations which require a Jetty server to do their job. This is, however, not necessarily the case in every implementations of those interfaces so the Jetty server is only a dependency. Since it would be a huge amount of pain to wrap the entire jetty server with all its logging, connector and Handler configurations, I want to inject the server to those implementations with Spring. I decided that injecting the Server class is not a good idea because an implementation could stop the server even if its required at another location. Currently I inject empty HandlerList classes to those implementations and they register their handlers to avoid those problems. The Problem: Those handlers might interfere with other handlers for example: implementation one might register a handler for /foo and implementation two too... problem. Has anyone used Jetty in such an environment? And how could this problem be solved? My XML to clarify my problem: <bean id="jetty" class="org.eclipse.jetty.server.Server" destroy-method="stop"> <property name="connectors"> <list> <bean class="org.eclipse.jetty.server.bio.SocketConnector"> <property name="host" value="10.8.0.46" /> <property name="port" value="9999" /> </bean> </list> </property> <property name="handler"> <bean class="org.eclipse.jetty.server.handler.HandlerCollection"> <property name="handlers"> <list> <ref bean="jetty.handlerList" /> <bean class="org.eclipse.jetty.server.handler.RequestLogHandler"> <property name="requestLog"> <bean class="org.eclipse.jetty.server.NCSARequestLog"> <constructor-arg value="${jetty.logfile}" /> <property name="extended" value="false"/> </bean> </property> </bean> </list> </property> </bean> </property> <property name="sendServerVersion" value="false" /> </bean> <bean id="jetty.handlerList" class="org.eclipse.jetty.server.handler.HandlerList" /> If I require an empty HandlerList I use something like this where com.example.myapp.util.ioc.CreateHandlerListFactory is a org.springframework.beans.factory.FactoryBean which creates a new HandlerList within the given HandlerList. <constructor-arg> <bean class="com.example.myapp.util.ioc.CreateHandlerListFactory"> <constructor-arg ref="jetty.handlerList"/> </bean> </constructor-arg>

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• How do I use constructor dependency injection to supply Models from a collection to their ViewModels

  - by GraemeF

  I'm using constructor dependency injection in my WPF application and I keep running into the following pattern, so would like to get other people's opinion on it and hear about alternative solutions. The goal is to wire up a hierarchy of ViewModels to a similar hierarchy of Models, so that the responsibility for presenting the information in each model lies with its own ViewModel implementation. (The pattern also crops up under other circumstances but MVVM should make for a good example.) Here's a simplified example. Given that I have a model that has a collection of further models: public interface IPerson { IEnumerable<IAddress> Addresses { get; } } public interface IAddress { } I would like to mirror this hierarchy in the ViewModels so that I can bind a ListBox (or whatever) to a collection in the Person ViewModel: public interface IPersonViewModel { ObservableCollection<IAddressViewModel> Addresses { get; } void Initialize(); } public interface IAddressViewModel { } The child ViewModel needs to present the information from the child Model, so it's injected via the constructor: public class AddressViewModel : IAddressViewModel { private readonly IAddress _address; public AddressViewModel(IAddress address) { _address = address; } } The question is, what is the best way to supply the child Model to the corresponding child ViewModel? The example is trivial, but in a typical real case the ViewModels have more dependencies - each of which has its own dependencies (and so on). I'm using Unity 1.2 (although I think the question is relevant across the other IoC containers), and I am using Caliburn's view strategies to automatically find and wire up the appropriate View to a ViewModel. Here is my current solution: The parent ViewModel needs to create a child ViewModel for each child Model, so it has a factory method added to its constructor which it uses during initialization: public class PersonViewModel : IPersonViewModel { private readonly Func<IAddress, IAddressViewModel> _addressViewModelFactory; private readonly IPerson _person; public PersonViewModel(IPerson person, Func<IAddress, IAddressViewModel> addressViewModelFactory) { _addressViewModelFactory = addressViewModelFactory; _person = person; Addresses = new ObservableCollection<IAddressViewModel>(); } public ObservableCollection<IAddressViewModel> Addresses { get; private set; } public void Initialize() { foreach (IAddress address in _person.Addresses) Addresses.Add(_addressViewModelFactory(address)); } } A factory method that satisfies the Func<IAddress, IAddressViewModel> interface is registered with the main UnityContainer. The factory method uses a child container to register the IAddress dependency that is required by the ViewModel and then resolves the child ViewModel: public class Factory { private readonly IUnityContainer _container; public Factory(IUnityContainer container) { _container = container; } public void RegisterStuff() { _container.RegisterInstance<Func<IAddress, IAddressViewModel>>(CreateAddressViewModel); } private IAddressViewModel CreateAddressViewModel(IAddress model) { IUnityContainer childContainer = _container.CreateChildContainer(); childContainer.RegisterInstance(model); return childContainer.Resolve<IAddressViewModel>(); } } Now, when the PersonViewModel is initialized, it loops through each Address in the Model and calls CreateAddressViewModel() (which was injected via the Func<IAddress, IAddressViewModel> argument). CreateAddressViewModel() creates a temporary child container and registers the IAddress model so that when it resolves the IAddressViewModel from the child container the AddressViewModel gets the correct instance injected via its constructor. This seems to be a good solution to me as the dependencies of the ViewModels are very clear and they are easily testable and unaware of the IoC container. On the other hand, performance is OK but not great as a lot of temporary child containers can be created. Also I end up with a lot of very similar factory methods. Is this the best way to inject the child Models into the child ViewModels with Unity? Is there a better (or faster) way to do it in other IoC containers, e.g. Autofac? How would this problem be tackled with MEF, given that it is not a traditional IoC container but is still used to compose objects?

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• Simple Constructor With Initializer List? - C++

  - by Alex

  Hi all, below I've included my h file, and my problem is that the compiler is not liking my simple exception class's constructor's with initializer lists. It also is saying that string is undeclared identifier, even though I have #include <string> at the top of the h file. Do you see something I am doing wrong? For further explanation, this is one of my domain classes that I'm integrating into a wxWidgets GUI application on Windows. Thanks! Time.h #pragma once #include <string> #include <iostream> // global constants for use in calculation const int HOURS_TO_MINUTES = 60; const int MINUTES_TO_HOURS = 100; class Time { public: // default Time class constructor // initializes all vars to default values Time(void); // ComputeEndTime computes the new delivery end time // params - none // preconditions - vars will be error-free // postconditions - the correct end time will be returned as an int // returns an int int ComputeEndTime(); // GetStartTime is the getter for var startTime // params - none // returns an int int GetStartTime() { return startTime; } // GetEndTime is the getter for var endTime // params - none // returns an int int GetEndTime() { return endTime; } // GetTimeDiff is the getter for var timeDifference // params - none // returns a double double GetTimeDiff() { return timeDifference; } // SetStartTime is the setter for var startTime // params - an int // returns void void SetStartTime(int s) { startTime = s; } // SetEndTime is the setter for var endTime // params - an int // returns void void SetEndTime(int e) { endTime = e; } // SetTimeDiff is the setter for var timeDifference // params - a double // returns void void SetTimeDiff(double t) { timeDifference = t; } // destructor for Time class ~Time(void); private: int startTime; int endTime; double timeDifference; }; class HourOutOfRangeException { public: // param constructor // initializes message to passed paramater // preconditions - param will be a string // postconditions - message will be initialized // params a string // no return type HourOutOfRangeException(string pMessage) : message(pMessage) {} // GetMessage is getter for var message // params none // preconditions - none // postconditions - none // returns string string GetMessage() { return message; } // destructor ~HourOutOfRangeException() {} private: string message; }; class MinuteOutOfRangeException { public: // param constructor // initializes message to passed paramater // preconditions - param will be a string // postconditions - message will be initialized // params a string // no return type MinuteOutOfRangeException(string pMessage) : message(pMessage) {} // GetMessage is getter for var message // params none // preconditions - none // postconditions - none // returns string string GetMessage() { return message; } // destructor ~MinuteOutOfRangeException() {} private: string message; }; class PercentageOutOfRangeException { public: // param constructor // initializes message to passed paramater // preconditions - param will be a string // postconditions - message will be initialized // params a string // no return type PercentageOutOfRangeException(string pMessage) : message(pMessage) {} // GetMessage is getter for var message // params none // preconditions - none // postconditions - none // returns string string GetMessage() { return message; } // destructor ~PercentageOutOfRangeException() {} private: string message; }; class StartEndException { public: // param constructor // initializes message to passed paramater // preconditions - param will be a string // postconditions - message will be initialized // params a string // no return type StartEndException(string pMessage) : message(pMessage) {} // GetMessage is getter for var message // params none // preconditions - none // postconditions - none // returns string string GetMessage() { return message; } // destructor ~StartEndException() {} private: string message; };

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• Are injectable classes allowed to have constructor parameters in DI?

  - by Songo

  Given the following code: class ClientClass{ public function print(){ //some code to calculate $inputString $parser= new Parser($inputString); $result= $parser->parse(); } } class Parser{ private $inputString; public __construct($inputString){ $this->inputString=$inputString; } public function parse(){ //some code } } Now the ClientClass has dependency on class Parser. However, if I wanted to use Dependency Injection for unit testing it would cause a problem because now I can't send the input string to the parser constructor like before as its calculated inside ClientCalss itself: class ClientClass{ private $parser; public __construct(Parser $parser){ $this->parser=$parser; } public function print(){ //some code to calculate $inputString $result= $this->parser->parse(); //--> will throw an exception since no string was provided } } The only solution I found was to modify all my classes that took parameters in their constructors to utilize Setters instead (example: setInputString()). However, I think there might be a better solution than this because sometimes modifying existing classes can cause much harm than benefit. So, Are injectable classes not allowed to have input parameters? If a class must take input parameters in its constructor, what would be the way to inject it properly? UPDATE Just for clarification, the problem happens when in my production code I decide to do this: $clientClass= new ClientClass(new Parser($inputString));//--->I have no way to predict $inputString as it is calculated inside `ClientClass` itself. UPDATE 2 Again for clarification, I'm trying to find a general solution to the problem not for this example code only because some of my classes have 2, 3 or 4 parameters in their constructors not only one.

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• Dependency injection: At what point am I allowed to create a new object?

  - by Gaz_Edge

  I am refactoring a PHP application, and I am trying to do has much dependency injection (DI) as possible. I feel like I've got a good grasp of how it works, and I can certainly see my classes becoming a lot leaner and more robust. I'm refactoring so that I can inject a dependency rather than create a new object within the class, but at some point I am going to have to create some objects, that is, use the dreaded new keyword. The problem I have now run into is at what point can I actually create new objects? It's looking like I'll end up at a top level class, creating loads of new objects as there is no where else to go. This feels wrong. I've read some blogs that use factory classes to create all the objects, and then you inject the factory into other classes. You can then call the factory methods, and the factory creates the new object for you. My concern with doing this is now my factory classes are going to be a new free-for-all! I guess this may be OK as they are factory classes, but are there some rules to stick to when using a factory pattern and DI, or am I going way off the mark here?

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• Dependency Injection: where to store dependencies used by only one method?

  - by simoneL

  I developing a project integrated with Dependency Injection (just for reference, I'm using Unity). The problem is that I have some Manager classes with several methods and in many cases I have dependencies used only in one method. public class UserManager : IUserManager { private UserRepository UserRepository {get;set;} private TeamRepository TeamRepository {get;set;} private CacheRepository CacheRepository {get;set;} private WorkgroupRepository WorkgroupRepository {get;set;} public UserManager(UserRepository userRepository, TeamRepository teamRepository, CacheRepository cacheRepository , WorkgroupRepository workgroupRepository, ... // Many other dependencies ) { UserRepository = userRepository; TeamRepository = teamRepository; CacheRepository = cacheRepository ; WorkgroupRepository = workgroupRepository; ... // Setting the remaining dependencies } public void GetLatestUser(){ // Uses only UserRepository } public void GetUsersByTeam(int teamID){ // Uses only TeamRepository } public void GetUserHistory(){ // Uses only CacheRepository } public void GetUsersByWorkgroup(int workgroupID){ // Uses only workgroupRepository } } The UserManager is instantiated in this way: DependencyFactory<IUserManager>(); Note: DependencyFactory is just a wrapper to simplify the access to the UnityContainer Is it OK to have classes like that in the example? Is there a better way to implement avoiding to instantiate all the unnecessary dependencies?

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• Dependency Injection: What point am I allowed to create a new object?

  - by Gaz_Edge

  I am refactoring a php application and I am trying to do has much dependency injection as possible. I feel like I've got a good grasp of how it works, and I can certainly see my classes becoming a lot leaner and more robust. Im refactoring so that I can inject a dependency rather than create a new object within the class, but at some point I am going to have to create some objects i.e. use the dreaded new keyword. The problem I have now run into is at what point can I actually create new objects? Its looking like I'll end up at a top level class, creating loads of new objects as there is no where else to go. This feels wrong. I've read some blogs that use factory classes to create all the objects, and then you inject the factory into other classes. You can then call the factory methods, and the factory creates the new object for you. My concern with doing this is now my factory classes are going to be a new free-for-all! I guess this may be ok as they are factory classes, but are there some rules to stick to when using factory pattern and DI, or am I going way off the mark here.

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• Passing array into constructor to use on JList

  - by OVERTONE

  I know the title sound confusing and thats because it is. its a bit long so try too stay with me. this is the layout i have my code designed variables constructor methods. im trying too fill a Jlist full on names. i want too get those names using a method. so here goes. in my variables i have my JList. its called contactNames; i also have an array which stores 5 strings which are the contacts names; heres the code for that anyway String contact1; String contact2; String contact3; String contact4; String contact5; String[] contactListNames; JList contactList; simple enough. then in my constructor i have the Jlist defined to fill itself with the contents of the array fillContactList(); JList contactList = new JList(contactListNames); that method fillContactList() is coming up shortly. notice i dont have the array defined in the constructor. so heres my first question. can i do that? define the array to contain something in te constructor rather than filling it fromt the array. now heres where stuff gets balls up. ive created three different methods all of which havent worked. basically im trying to fill the array with all of them. this is the simplest one. it doesnt set the Jlist, it doesnt do anything compilicated. all it trys too do is fill the array one bit at a time public void fillContactList() { for(int i = 0;i<3;i++) { try { String contact; System.out.println(" please fill the list at index "+ i); Scanner in = new Scanner(System.in); contact = in.next(); contactListNames[i] = contact; in.nextLine(); } catch(Exception e) { e.printStackTrace(); } } } unfortunately this doesnt qwork. i get the print out to fill it at index 0; i input something and i get a nice big stack trace starting at contactListNames[i] = contact; so my two questions in short are how i define an array in a constructor. and why cant i fill the array from that method. ************************888 **************************888 stack trace by request please fill the list at index 0 overtone java.lang.NullPointerException please fill the list at index 1 at project.AdminMessages.fillContactList(AdminMessages.java:408) at project.AdminMessages.<init>(AdminMessages.java:88) at project.AdminUser.createAdminMessages(AdminUser.java:32) at project.AdminUser.<init>(AdminUser.java:18) at project.AdminUser.main(AdminUser.java:47) it was a null poiinter exception

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• Conversion constructor vs. conversion operator: precedence

  - by GRB

  Reading some questions here on SO about conversion operators and constructors got me thinking about the interaction between them, namely when there is an 'ambiguous' call. Consider the following code: class A; class B { public: B(){} B(const A&) //conversion constructor { cout << "called B's conversion constructor" << endl; } }; class A { public: operator B() //conversion operator { cout << "called A's conversion operator" << endl; return B(); } }; int main() { B b = A(); //what should be called here? apparently, A::operator B() return 0; } The above code displays "called A's conversion operator", meaning that the conversion operator is called as opposed to the constructor. If you remove/comment out the operator B() code from A, the compiler will happily switch over to using the constructor instead (with no other changes to the code). My questions are: Since the compiler doesn't consider B b = A(); to be an ambiguous call, there must be some type of precedence at work here. Where exactly is this precedence established? (a reference/quote from the C++ standard would be appreciated) From an object-oriented philosophical standpoint, is this the way the code should behave? Who knows more about how an A object should become a B object, A or B? According to C++, the answer is A -- is there anything in object-oriented practice that suggests this should be the case? To me personally, it would make sense either way, so I'm interested to know how the choice was made. Thanks in advance

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• Dependency Injection and decoupling of software layers

  - by cs31415

  I am trying to implement Dependency Injection to make my app tester friendly. I have a rather basic doubt. Data layer uses SqlConnection object to connect to a SQL server database. SqlConnection object is a dependency for data access layer. In accordance with the laws of dependency injection, we must not new() dependent objects, but rather accept them through constructor arguments. Not wanting to upset the DI gods, I dutifully create a constructor in my DAL that takes in SqlConnection. Business layer calls DAL. Business layer must therefore, pass in SqlConnection. Presentation layer calls Business layer. Hence it too, must pass in SqlConnection to business layer. This is great for class isolation and testability. But didn't we just couple the UI and Business layers to a specific implementation of the data layer which happens to use a relational database? Why do the Presentation and Business layers need to know that the underlying data store is SQL? What if the app needs to support multiple data sources other than SQL server (such as XML files, Comma delimited files etc.) Furthermore, what if I add another object upon which my data layer is dependent on (say, a second database). Now, I have to modify the upper layers to pass in this new object. How can I avoid this merry-go-round and reap all the benefits of DI without the pain?

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• LINQtoSQL Custom Constructor off Partial Class?

  - by sah302

  Hi all, I read this question here: http://stackoverflow.com/questions/82409/is-there-a-way-to-override-the-empty-constructor-in-a-class-generated-by-linqtosq Typically my constructor would look like: public User(String username, String password, String email, DateTime birthday, Char gender) { this.Id = Guid.NewGuid(); this.DateCreated = this.DateModified = DateTime.Now; this.Username = username; this.Password = password; this.Email = email; this.Birthday = birthday; this.Gender = gender; } However, as read in that question, you want to use partial method OnCreated() instead to assign values and not overwrite the default constructor. Okay so I got this : partial void OnCreated() { this.Id = Guid.NewGuid(); this.DateCreated = this.DateModified = DateTime.Now; this.Username = username; this.Password = password; this.Email = email; this.Birthday = birthday; this.Gender = gender; } However, this gives me two errors: Partial Methods must be declared private. Partial Methods must have empty method bodies. Alright I change it to Private Sub OnCreated() to remove both of those errors. However I am still stuck with...how can I pass it values as I would with a normal custom constructor? Also I am doing this in VB (converted it since I know most know/prefer C#), so would that have an affect on this?

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• Simplifying Testing through design considerations while utilizing dependency injection

  - by Adam Driscoll

  We are a few months into a green-field project to rework the Logic and Business layers of our product. By utilizing MEF (dependency injection) we have achieved high levels of code coverage and I believe that we have a pretty solid product. As we have been working through some of the more complex logic I have found it increasingly difficult to unit test. We are utilizing the CompositionContainer to query for types required by these complex algorithms. My unit tests are sometimes difficult to follow due to the lengthy mock object setup process that must take place, just right, to allow for certain circumstances to be verified. My unit tests often take me longer to write than the code that I'm trying to test. I realize this is not only an issue with dependency injection but with design as a whole. Is poor method design or lack of composition to blame for my overly complex tests? I've tried base classing tests, creating commonly used mock objects and ensuring that I utilize the container as much as possible to ease this issue but my tests always end up quite complex and hard to debug. What are some tips that you've seen to keep such tests concise, readable, and effective?

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• Constructor or Assignment Operator

  - by ju

  Can you help me is there definition in C++ standard that describes which one will be called constructor or assignment operator in this case: #include <iostream> using namespace std; class CTest { public: CTest() : m_nTest(0) { cout << "Default constructor" << endl; } CTest(int a) : m_nTest(a) { cout << "Int constructor" << endl; } CTest(const CTest& obj) { m_nTest = obj.m_nTest; cout << "Copy constructor" << endl; } CTest& operatorint rhs) { m_nTest = rhs; cout << "Assignment" << endl; return *this; } protected: int m_nTest; }; int _tmain(int argc, _TCHAR* argv[]) { CTest b = 5; return 0; } Or is it just a matter of compiler optimization?

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• Constructor being called again?

  - by Halo

  I have this constructor; public UmlDiagramEntity(ReportElement reportElement, int pageIndex, Controller controller) { super(reportElement.getX1(), reportElement.getY1(), reportElement.getX2(), reportElement.getY2()); setLayout(null); this.pageIndex = pageIndex; this.controller = controller; reportElements = reportElement.getInternalReportElements(); components = new ArrayList<AbstractEntity>(); changedComponentIndex = -1; PageListener p = new PageListener(); this.addMouseMotionListener(p); this.addMouseListener(p); setPage(); } And I have an update method in the same class; @Override public void update(ReportElement reportElement) { if (changedComponentIndex == -1) { super.update(reportElement); } else { reportElements = reportElement.getInternalReportElements(); if (components.size() == reportElements.size()) { if (!isCommitted) { if (reportElement.getType() == ReportElementType.UmlRelation) { if (checkInvolvementAndSet(changedComponentIndex)) { anchorEntity(changedComponentIndex); } else { resistChanges(changedComponentIndex); } return; } } ..................goes on When I follow the flow from the debugger, I see that when update is called, somewhere in the method, the program goes into the constructor and executes it all over again (super, pageIndex, etc.). Why does it go to the constructor :D I didn't tell it to go there. I can make a deeper analysis and see where it goes to the constructor if you want. By the way, changedComponentIndex is a static variable.

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• Java Constructor Style (Check parameters aren't null)

  - by Peter

  What are the best practices if you have a class which accepts some parameters but none of them are allowed to be null? The following is obvious but the exception is a little unspecific: public class SomeClass { public SomeClass(Object one, Object two) { if (one == null || two == null) { throw new IllegalArgumentException("Parameters can't be null"); } //... } } Here the exceptions let you know which parameter is null, but the constructor is now pretty ugly: public class SomeClass { public SomeClass(Object one, Object two) { if (one == null) { throw new IllegalArgumentException("one can't be null"); } if (two == null) { throw new IllegalArgumentException("two can't be null"); } //... } Here the constructor is neater, but now the constructor code isn't really in the constructor: public class SomeClass { public SomeClass(Object one, Object two) { setOne(one); setTwo(two); } public void setOne(Object one) { if (one == null) { throw new IllegalArgumentException("one can't be null"); } //... } public void setTwo(Object two) { if (two == null) { throw new IllegalArgumentException("two can't be null"); } //... } } Which of these styles is best? Or is there an alternative which is more widely accepted? Cheers, Pete

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• Serializing Configurations for a Dependency Injection / Inversion of Control

  - by Joshua Starner

  I've been researching Dependency Injection and Inversion of Control practices lately in an effort to improve the architecture of our application framework and I can't seem to find a good answer to this question. It's very likely that I have my terminology confused, mixed up, or that I'm just naive to the concept right now, so any links or clarification would be appreciated. Many examples of DI and IoC containers don't illustrate how the container will connect things together when you have a "library" of possible "plugins", or how to "serialize" a given configuration. (From what I've read about MEF, having multiple declarations of [Export] for the same type will not work if your object only requires 1 [Import]). Maybe that's a different pattern or I'm blinded by my current way of thinking. Here's some code for an example reference: public abstract class Engine { } public class FastEngine : Engine { } public class MediumEngine : Engine { } public class SlowEngine : Engine { } public class Car { public Car(Engine e) { engine = e; } private Engine engine; } This post talks about "Fine-grained context" where 2 instances of the same object need different implementations of the "Engine" class: http://stackoverflow.com/questions/2176833/ioc-resolve-vs-constructor-injection Is there a good framework that helps you configure or serialize a configuration to achieve something like this without hard coding it or hand-rolling the code to do this? public class Application { public void Go() { Car c1 = new Car(new FastEngine()); Car c2 = new Car(new SlowEngine()); } } Sample XML: <XML> <Cars> <Car name="c1" engine="FastEngine" /> <Car name="c2" engine="SlowEngine" /> </Cars> </XML>

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• PHP -- automatic SQL injection protection?

  - by ashgromnies

  I took over maintenance of a PHP app recently and I'm not super familiar with PHP but some of the things I've been seeing on the site are making me nervous that it could be vulnerable to a SQL injection attack. For example, see how this code for logging into the administrative section works: $password = md5(HASH_SALT . $_POST['loginPass']); $query = "SELECT * FROM `administrators` WHERE `active`='1' AND `email`='{$_POST['loginEmail']}' AND `password`='{$password}'"; $userInfo = db_fetch_array(db_query($query)); if($userInfo['id']) { $_SESSION['adminLoggedIn'] = true; // user is logged in, other junk happens here, not important The creators of the site made a special db_query method and db_fetch_array method, shown here: function db_query($qstring,$print=0) { return @mysql(DB_NAME,$qstring); } function db_fetch_array($qhandle) { return @mysql_fetch_array($qhandle); } Now, this makes me think I should be able to do some sort of SQL injection attack with an email address like: ' OR 'x'='x' LIMIT 1; and some random password. When I use that on the command line, I get an administrative user back, but when I try it in the application, I get an invalid username/password error, like I should. Could there be some sort of global PHP configuration they have enabled to block these attacks? Where would that be configured? Here is the PHP --version information: # php --version PHP 5.2.12 (cli) (built: Feb 28 2010 15:59:21) Copyright (c) 1997-2009 The PHP Group Zend Engine v2.2.0, Copyright (c) 1998-2009 Zend Technologies with the ionCube PHP Loader v3.3.14, Copyright (c) 2002-2010, by ionCube Ltd., and with Zend Optimizer v3.3.9, Copyright (c) 1998-2009, by Zend Technologies

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• Calling base class constructor

  - by The Void

  In the program below, is the line Derived(double y): Base(), y_(y) correct/allowed? That is, does it follow ANSI rules? #include <iostream> class Base { public: Base(): x_(0) { std::cout << "Base default constructor called" << std::endl; } Base(int x): x_(x) { std::cout << "Base constructor called with x = " << x << std::endl; } void display() const { std::cout << x_ << std::endl; } protected: int x_; }; class Derived: public Base { public: Derived(): Base(1), y_(1.2) { std::cout << "Derived default constructor called" << std::endl; } Derived(double y): Base(), y_(y) { std::cout << "Derived constructor called with y = " << y << std::endl; } void display() const { std::cout << Base::x_ << ", " << y_ << std::endl; } private: double y_; }; int main() { Base b1; b1.display(); Derived d1; d1.display(); std::cout << std::endl; Base b2(-9); b2.display(); Derived d2(-8.7); d2.display(); return 0; }

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• C++: Constructor/destructor unresolved when not inline?

  - by Anamon

  In a plugin-based C++ project, I have a TmpClass that is used to exchange data between the main application and the plugins. Therefore the respective TmpClass.h is included in the abstract plugin interface class that is included by the main application project, and implemented by each plugin. As the plugins work on STL vectors of TmpClass instances, there needs to be a default constructor and destructor for the TmpClass. I had declared these in TmpClass.h: class TmpClass { TmpClass(); ~TmpClass(); } and implemented them in TmpClass.cpp. TmpClass::~TmpClass() {} TmpClass::TmpClass() {} However, when compiling plugins this leads to the linker complaining about two unresolved externals - the default constructor and destructor of TmpClass as required by the std::vector<TmpClass> template instantiation - even though all other functions I declare in TmpClass.h and implement in TmpClass.cpp work. As soon as I remove the (empty) default constructor and destructor from the .cpp file and inline them into the class declaration in the .h file, the plugins compile and work. Why is it that the default constructor and destructor have to be inline for this code to compile? Why does it even maatter? (I'm using MSVC++8).

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• Java: design problem with final-value and empty constructor

  - by HH

  $ javac InitInt.java InitInt.java:7: variable right might not have been initialized InitInt(){} ^ 1 error $ cat InitInt.java import java.util.*; import java.io.*; public class InitInt { private final int right; // Design Problem? // I feel the initialization problem is just due to bad style. InitInt(){} InitInt{ // Still the error, "may not be initialized" // How to initialise it? if(snippetBuilder.length()>(charwisePos+25)){ right=charwisePos+25; }else{ right=snippetBuilder.length()-1; } } public static void main(String[] args) { InitInt test = new InitInt(); System.out.println(test.getRight()); } public int getRight(){return right;} } Partial Solutions and Suggestions use "this" to access methods in the class, instead of creating empty constructor change final to non-final with final field value: initialize all final values in every constructor remove the empty constructor, keep your code simple and clean

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• C# ArrayList calling on a constructor class

  - by EvanRyan

  I'm aware that an ArrayList is probably not the way to go with this particular situation, but humor me and help me lose this headache. I have a constructor class like follows: class Peoples { public string LastName; public string FirstName; public Peoples(string lastName, string firstName) { LastName = lastName; FirstName = firstName; } } And I'm trying to build an ArrayList to build a collection by calling on this constructor. However, I can't seem to find a way to build the ArrayList properly when I use this constructor. I have figured it out with an Array, but not an ArrayList. I have been messing with this to try to build my ArrayList: ArrayList people = new ArrayList(); people[0] = new Peoples("Bar", "Foo"); people[1] = new Peoples("Quirk", "Baz"); people[2] = new Peopls("Get", "Gad"); My indexing is apparently out of range according to the exception I get.

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• c++ Using const in a copy constructor?

  - by Anton

  I have never written copy constructor, so in order to avoid pain i wanted to know if what i have coded is legit. It compiles but i am not sure that it works as a copy constructor should. Also do i have to use const in the copy constructor or i can simply drop it. (What i dont like about const is that the compiler cries if i use some non const functions). //EditNode.h class EditNode { explicit EditNode(QString elementName); EditNode(const EditNode &src); } //EditNodeContainer.h class EditNodeContainer : public EditNode { explicit EditNodeContainer(QString elementName); EditNodeContainer(const EditNodeContainer &src); } //EditNodeContainer.cpp EditNodeContainer::EditNodeContainer(QString elementName):EditNode(elementName) { } //This seems to compile but not sure if it works EditNodeContainer::EditNodeContainer(const EditNodeContainer &src):EditNode(src) { } //the idea whould be to do something like this EditNodeContainer *container1 = new EditNodeContainer("c1"); EditNodeContainer *copyContainer = new EditNodeContainer(container1);

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