I have some questions on GUI design. I'm making an Instant Messenger and, having finished the server, I am now working on the client. I've made many GUIs before -- I'm familiar with swing, awt, and swt --but I feel like my design of GUIs is bad. For this particular project I am using ...

Hi all,I am a PhD student at the University of Auckland, New Zealand. As part of my research I have performed an empirical study on a large corpus of Java software (which includes applications like Ant, Tomcat, Eclipse, Netbeans, Azureus). You can see how the structure (design) of the classes ...

Hi all,I need to use a UML modeling tool for my java projects desin and implementation.for the time bein i use a good tool called umbrello ; but only on linux OS.I prefer to use an Eclipse UML plugin that has most capabilities as umbrello ; so I can use it on windows also.I tied some free ...

is it bad oop practice to keep all your global constants in main() and have your other classes access them from there?also, would anyone happen to know of a good online resource that addresses proper oop practices and goes beyond explaining the foundation stuff like inheritence, encapsulation, ...

I am working on a project in which I am going to need to reuse a lot of the functionality of some existing singletons in the code base of my company's application.There are ligitimate reasons for these objects to be singletons (i.e. they store data that I only want stored once, etc). But, in ...

I'm trying to use MVC for the first time, and I'm trying to follow the example given in http://java.sun.com/developer/onlineTraining/GUI/Swing2/shortcourse.htmlThe main part of my model (the equivalent of IntVectorModel) is capable of creating message generators. It keeps a list of which ...

I've heard that using the instanceof operator isn't such a great code technique, and since I'm in the design phase, I feel like I should be able to avoid this. Right now, part of my design requires use of the instanceof operator as well as casting.Let's say you have a common notifier ...

Two questions:1) Let's say you have an instant messenging server. (I am using the conditional because I have already made the server and am really curious about the client, yet this is the same problem with an easier example to explain.) The server has to validate the user's registration, ...

I work for a bank where we sell various financial products. For example credit products. Let's say the name of a credit product is BicycleLoan with which you can buy bicycles. Buying a bicycle on loan can be done only if you fullfill the requirements of the Bank. If it is ok, you can get that ...

I have a class that implements two interfaces. ONe is a management interface and the other is a usage interface. Users should only know about the user interface. But I wanted to prevent the ability to cast to the management interface. Since the clas simplemented both there was no way to prevent ...

Hi,I have a JSP page which displays attributes of an object in view-only mode. The user might click 'Edit' or click cancel and move on to some other page.Currently I am storing the object id as hidden value in the view jsp and when the user clicks edit I make an explicit db call, retrieve the ...

I have two model classes. System and Component. And two views, SystemView and ComponentView. When the SystemView is closed the ComponentView needs to be closed. However, the ComponentView does not know anything about the SystemView. The only way I have found to connect the ComponentView with ...

Somebody at work has just made an interesting observation and its bugging me, comments please.When I started Java I just used classes (and abstract classes), and didnt bother with Interfaces I understood them to be a way of getting round the lack of MultipleInheritance and it wasnt a problem ...

I am trying to learn more about creating enterprise applications and I am looking for a easy to understand explanation of using DAO's as well as how to create them within a JSP/struts application. Any suggestions would be greatly appreciated.

I'm currently reading Core J2EE Patterns to try and improve my design skills. It's my first real introduction to patterns, and the first 150 or so pages were an okay read. When it gets into the pattern section there are a lot of references to other patterns, not covered in the book, which are ...

Hello,I work for a bank as a java programmer. We have products like loans and systems that help the office clerks to sell that loans. Now we use self made RMI client-"server" architecture. The client is a Swing GUI connecting to the RMI server object. We are planning to have more kind of ...

I am very new to hibernate and this question might seem a little elementary, but here it goes:I have a classpublic List<PurchaseOrder> getPurchaseOrders with a method that creates the query in question:public Object doInHibernate(Session session)throws HibernateException, SQLException ...

I have a situation here and I havent been able to conceptualize a good solution.BackgroundI have an object that processes changes in things that contribute to changes. And then I have this system of objects.ArchitectureSystemComponentComponentInstanceThe architecture does not really change, its ...

Hi,What is the best place to check security constraints. Is it the front controller of web app or a session facade.Thanking You,Chamal.

could someone please explain in detail the difference between a parameter and an argument.Thank you.

Hi,I did read the singleton topic. But it stays confuse to me.How to garantee that only one instance of Class per VM ?I am building a component to stay running forever doing some tasks... From command line this can be started and stopped..I am trying to implement a class, a singleton. Some ...

As it turns out, a quick search in google reveals that the issue of return type vs. exception is somewhat hotly contested, but I thought I'd check to see what people here thought, based on a particular example that I'm dealing with.In an interface I've developed, I have the method:public ...

I hope this is the right forum to ask this question since it deals with a design decision.I'm writting an implementation for a new type of file format called "NAP" (Network cAPture) which stores captured network packets in a file. Similar to PCAP and SNOOP file formats.I'm designing the ...

hi everybodyI guess this is not a java-specific question, but this is the best forum I know ;-)recently I posted a topic asking for nice plugin frameworks to include into my projects, and I decided to go with JPF... also because I haven't found any other option =Pshortly I'll begin a ...

What are the recommended approaches for dealing with errors that arise in the Model (observable/subject/publisher) piece of an MVC architecture? For example, if an error occurs in the Model during a database update that resulted from a database access initiated from View to Controller to Model, ...

In the J2EE patterns catalog it is stated that there is typically a one to one mapping between a Business Delegate and a Session Facade. I have been, for sometime, been under the impression that the Business Delegate can be a singleton. Does it make sense to have a singleton Business Delegate ...

Hi,I understood the structure of DAO pattern like : The business Object uses Data AccessObject which encapsulates the DataSource. The DAO creates/uses the Transfer Object and the BusinessObject obtains/modifies the Transfer Object. Can i get the sample code for this pattern and any links for ...

I'm relatively new to "real" object-oriented design/development (i.e. patterns/refactoring etc.) although I've been working with OOP languages for quite some time. I've been doing a lot of reading/research in order to take it to the next level and am incorporating it into a new project I'm ...

Hi all.I have an application that I think needs to use the strategy pattern but I'm not sure. I'm fairly new to design patterns but I would like to be able to use the right one and as yet I can't see which one to use and where.My first instance of the application places a listener on a file ...

I've found a common source of memory leaks is when objects that add themselves to listener lists forget to remove themselves when they are done.It would be nice to generalize and say that listener lists should contain weak references, but there are probably valid cases where a listener's only ...

Hello,I am in a dilemma of making a design decision . We are developing a business tier component. This is going to talk to webservices on the backend. Right now it is going to integrate with 2 different backend systems through web services. In future it might support more of such backend ...

Hi I am trying to verify that you could have multiple instances of singleton if you use different class loader. Could somebody tell how I can verify . Here is the sample filespublic class SingletonTest {private static SingletonTest mSingleton ;public SingletonTest(){}private int x = 0;public ...

In my application, business delegate is calling Session Facade through business interface. Session Facade is implementing business interface which includes my application business processes.In my class diagram, I am showing business delegate, business interface and Session Facade. What kind of ...

Hi all,Tell me the diff b/w DTO,BOThanx

hai Friends, I know basics of struts. I have done basic examples.I have to know , how to get dynamic values in "view".Instead of writing like this..<html:select property="color1" size="4" ><html:option value="red">red</html:option><html:option ...

I have a class A that uses class B. Class B uses class C. When I am in class A I want to retrieve data from class C. Currently, when I am in class A, I am using a method call on class B to ask class C for the data. The effect is that I am passing the data item from C to B and then from B to A. ...

Car > VW > Golf > ....Suppose we got that hierarchy where all cars provide services as startEngine(), stopEngine(), etc. On the other side a VW Golf can be automatic, can be convertible, etc. and should provice services as openRoof in case of convertible or should startEngine different ...

My people in the, I really appreciate your contribution to my questions.can someone explain AWT and Applet in details, and their difference?Thank you.

My people in the house, I really appreciate your contributions to my questions.In addition, can someone explain AWT and Applet in details, and their difference?Thank you.

HiAre the following design principles correct in the case of designing enterprise application with java interfaces:1. create interfaces to all the application boundaries and controlls and entities.2. the method parameters must be specific objects instead of interfaces. If so, will this pose a ...

Hi all,I need some help to solve a design problem ( I suppose !).I磛e created an Interface declaring methods that throws an Exception and created an Adapter implementing my Interface. I thought that when I write a class that extends my Adapter it would force to write the method signature with ...

Hai friends, I am going to do sun certification(SCJP) in this month. But, don't have any sun certification materials.I can't even download files from my company also.so, ifyou have any materials regarding this please send to awm_riaz@yahoo.comIt will be very useful for me.Thanks in ...

This is the first time I used DAO design.I have a machine class and each machine has a few parts.How should I design the DAO? Especially regarding the inner parts.Should I create a DAO for machine and for part and put the PartDAO as an atribute of MachineDAO so that I can populate the ...

Anyone know best ideas/sites for the proper modelling of accounts using ejbsI would like to record and query transactions for up to 30 000 clients + 10 000 agentsEach client can have more than one accountAny advice is greatly appreciated

will it be better if i use creational pattern (Abstract Factory pattern) to implement DAO?DuffyMo ?

Is there a good article / book with real examples of how to arrive at a system design / architecture from requirements ?Also, is there a defined way to organize the requirements captured so that it would be easy to translate it into design ?We have captured our requirements from a data and ...

Hey,Could any one help me understanding the below query? 1. Heard that Middleware should play a role of get and put or tranforming messages between various applications?2. Bussiness logics can be added to a middleware application? If so, is it not a Architechtural flaw to have a such design?any ...

I have a Visitor interface and I want to have 2 implementations. The only problem is one Visitor does database things so it throws SQLException and the other does IO things so it throws IOException.What are my options when declaring the visitor methods?Declare them to throw ExceptionDeclare ...

Dear Forum,I am facing design problem...here it goes...I have a class that contains several method having name pattern like "createXXX()".All of these methods contains similar logic except data.This class is examined bythe another class for the"createXXX" methods for futher processing.Suppose ...

I'm trying to improve the Genericity of my code by setting the return type of methods that return classes that implement the List interface to List. In other words, rather than force the class user to work with, let's say, an ArrayList returned by one of my methods, I'd like the user to be ...