Which Pattern

I have a class called Classifier that takes in a list of Classification Objects and aggregates them to the highest classification. What I am running into is picking the best pattern to write this class with.
My Classifier Object is basically a filter, it takes in a Collection of Classification Objects and then returns a single Classification object representing the highest classification from that Collection. Its business logic is determined by a web service call, so this class contains no business rules. Its basically a facade to the web service.
ie:
Highest Importance -------- \
Important -------------------- \ __ Classifier __ ------- Highest Importance
Not Important ---------------- /          ^
General Use ---------------- /            |
                                          |
                                          v
                                      Web serviceI am wondering what is the best Pattern to use when creating this Classifier class as it has the potential to be used on every page ( right now, its only used in two modules ). As I have it coded at the moment, it is a singleton, but think that this could cause a bottleneck if we use it on every page.
Any suggestions would be greatly appreciated.
Thanks!

deeeeeean0hhh wrote:
endasil wrote:
deeeeeean0hhh wrote:
Already written... just looking to optimizeI hope you meant "refactor." In which case, only refactor if the current code smells.No, I meant optimize. It works, I just want to use a well known and tested structure if/when it scales up. I dont want to create code that works only to find out it is the cause of a bottleneck when we scale itWell, that's pretty low down on the list of priorities for a successful design pattern. Higher priorities are maintainability, standardization, correctness, low coupling, high cohesion, no duplication, etc, etc. Performance almost always takes a back seat when it comes to design patterns. In other words, there's almost always a faster way to do something than a pattern suggests, as they are generalizations. With generalization comes a lack of specialization (by definition) and therefore a lack of being able to precisely design a solution for a given problem. And that's all fine, because usually one approaches using a pattern from a position of wanting one of the above qualities, not performance.

Similar Messages

Which pattern for this scenario ?

Hi all,
I have an EJB which connects to an external system (written in Perl) using plain HttpConnections and posting HTML content.
I would like to centralize this access using a design pattern.
Which pattern is would fit this scenario ?
I wonder if I should use the Adapter pattern or the Bridge Pattern.
What do you say to it ?
Thanks
Francesco

I'd kind-of guessed it was uni work :-)
in all honesty, I wouldn't even approach the problem from a patterns perspective. all I see is a subsystem I don't want to deal with directly, so I define an interface to hide it behind. could argue that it's an Adapter, since it's taking the Http interface and abstracting away from it, to a java one. on the other hand, since mucking around with Http in java isn't exactly straight-forward, you're defining a more simple interface, so it could be considered a facade. which do you think is closer?
most people, once au fait with design patterns, think less in terms of those patterns, and more in terms of what OO principles to apply. score some extra credit by writing a passage about how design patterns are not prescriptive, and that many coders lift ideas about encapsulation and separation from patterns, rather than use the pattern exactly as described.

Which Pattern to apply ? Can Pattern can be applied .. ?

Hi All,
I have base class "BaseClassA" which do all my basic validation of a function. There are approx 10 validations are there.
Now my issue is that I need to add New Validation to the BaseClassA, how ever, I dont want to touch the "BaseClassA" code, as it my new validations is case-by-case, not mandatory like what 10 validations of current BasicClass.
My BasicClass constructor currently calls the all 10 validations now ..
Can I apply any particular pattern for the case ? Or just a subclass strategy will done ?
Can any one comment/suggest on the same
Thanks n Advance
Abhilash

Hi,
Thanks for that quick response.
My BasicClass has got all validations calls in single method, .i,e it cheques for Zero amount , max limit etc ..
if(amount >0 ) {return false;}
if(amount >Limit ) {return false;}
Now in between these 10 validations, as case need my validation to be done as 3rd or 4th .. so it is a Insert one more validation as required.. so a small catch here ..
Else as you have suggested was the simplest approach ..
Regards
Abhi

Cannot decide which pattern reflects on my application

I have a video-club management application implemented in Java, in which i followed the relatively general MVC architectural pattern.
1. my model consists of java classes mapped to database tables via Hibernate
2. my view consists of various frames in which the only logic directly implemented has to do with button listeners; database operations are called from the Controller.
3. my controller consists of a class in which various database operations for my objects as well as other functions are defined ( save(Customer cust), delete(Customer cust), List <Customer> getCustomers() and so on ).
I was told that it is not necessary to follow only one design pattern and that since MVC deals with the overall structure of the application in a more wide/general way, i can find other design patterns that deal with more specific parts of the application.
I have been looking for quite some time.
My confusion starts with the use of Hibernate; i found some patterns that deal with similar situations such as Active Record or DAO but i cannot tell for sure that my design follows the same rules.
I cannot understand why active record pattern is related and compared with hibernate (http://www.javalobby.org/articles/activeobjects/). Supposedly you can use more than one design patterns, how is it possible to have MVC and active record, when in AR you have to define database operations in the model (http://www.martinfowler.com/eaaCatalog/activeRecord.html) while with MVC and hibernate the model has nothing to do with the database directly.
I know that design patterns are meant to be used as solutions to problems and should be selected and followed before you actually start implementing the application, but any suggestion regarding which design pattern might fit in order to search for more information would be really appreciated.
Since i am not a developer and this application is my BSc's Final year project, in order to avoid any misunderstanding, the suggestions i am looking for, are meant to be a simple guide in terms of "check for this" or "no you got it wrong" rather than the actual solution.
thanks in advance

stathisoeo wrote:
I have a video-club management application implemented in Java, in which i followed the relatively general MVC architectural pattern.
1. my model consists of java classes mapped to database tables via HibernateSo, is the tail wagging the dog or the other way around? By that, I mean you will either end up creating your tables to resemble your objects or vice versa. Relational and object oriented are different concepts. Many times, you can map one-to-one, but there are enough differences to make it a headache.
2. my view consists of various frames in which the only logic directly implemented has to do with button listeners; database operations are called from the Controller.Seems ok. Swing, I presume?
3. my controller consists of a class in which various database operations for my objects as well as other functions are defined ( save(Customer cust), delete(Customer cust), List <Customer> getCustomers() and so on ).
These operations are typically done in a data access object. Your controller will typically only need a single piece of information, such as the primary key of the record, to pass to the DAO. (Of course for something like an update or create operation, you need to also supply these values or pass in a fully assembled Customer object, like you are doing above, but for a simple select or delete, you don't need the whole object per se).
>
I was told that it is not necessary to follow only one design pattern and that since MVC deals with the overall structure of the application in a more wide/general way, i can find other design patterns that deal with more specific parts of the application.The terms are a bit fuzzy here, generally. I personally view MVC as an architecture rather than a design pattern. It suffuses the entire application. You will use many other actual design patterns alongside MVC. Typically, a pattern is employed for a specific task.
I have been looking for quite some time.
My confusion starts with the use of Hibernate; i found some patterns that deal with similar situations such as Active Record or DAO but i cannot tell for sure that my design follows the same rules.
Don't simply use a pattern for its own sake. A DAO is straightforward enough that I would be surprised not to find it in a non-trivial application. Simply place all persistence logic for a given domain object in a separate object. Hibernate (or any ORM tool generally) allows your regular domain object to become an active record.
I cannot understand why active record pattern is related and compared with hibernate (http://www.javalobby.org/articles/activeobjects/). Supposedly you can use more than one design patterns, how is it possible to have MVC and active record, when in AR you have to define database operations in the model (http://www.martinfowler.com/eaaCatalog/activeRecord.html) while with MVC and hibernate the model has nothing to do with the database directly.
MVC is your architecture. Hibernate allows a POJO (plain ole java object) to be an active record. Typically, you still want a DAO. But if all your object does is crud (create read update delete), then you can either have one generic DAO to handle such objects, write a DAO for each, or dispense with the DAO entirely. You can still have any number of other patterns being used (visitor, strategy and memento are very common in code).
I know that design patterns are meant to be used as solutions to problems and should be selected and followed before you actually start implementing the application, but any suggestion regarding which design pattern might fit in order to search for more information would be really appreciated.
See above. Don't start by saying, "I want to use this pattern, where will it fit?" Rather, start by sketching out your solution at a high level, without consulting any patterns. Then look at what you have and see if any patterns show themselves. Pattern-fever is a disease that afflicts many when they first start using design patterns.
Since i am not a developer and this application is my BSc's Final year project, in order to avoid any misunderstanding, the suggestions i am looking for, are meant to be a simple guide in terms of "check for this" or "no you got it wrong" rather than the actual solution.
See above.
thanks in advanceYou are welcome.
- Saish

Return which pattern was matched in a regular expression

Given the following code;
Pattern pattern = Pattern.compile("\\d{1,3}\\.\\d{1,3}\\.\\d{1,3}\\.\\d{1,3}" + "|" + "\\btest\\b");
Matcher matcher = pattern.matcher("255.255.255.255");
while (matcher.find()) {
     System.out.println(matcher.group());
}This prints out 255.255.255.255.
Can anyone tell me how I obtain the actual pattern ("\\d{1,3}\\.\\d{1,3}\\.\\d{1,3}\\.\\d{1,3}") that was used to find the result?
I only want to loop through my search context once, so I am concatenating a number of expressions into one large regex. However, for each result I need to know which portion of the large regex triggered the match.
Any help would be appreciated.

You can keep the regexes separate without having to do many passes by using some lesser-known features of the Java regex package. Check this out: import java.util.regex.*;
public class Scannit
static Pattern pWord    = Pattern.compile("\\w+");
static Pattern pComment = Pattern.compile("/\\*(?:[^*]++|\\*(?!/))*+\\*/");
static Pattern pString = Pattern.compile("\"(?:[^\"\\\\]++|\\\\.)*+\"");
static Pattern pWS      = Pattern.compile("\\s+");
static Pattern sample = Pattern.compile("(?s).{1,12}");
static String str = "bork \"bork\" /*bork \"bork\" bork*/ bork";
public static void main(String... args)
    int start = 0;
    int end = str.length();
    Matcher m = pWS.matcher(str);
    while ( start < end )
      m.region(start, end);
      if ( m.usePattern(pWord).lookingAt() )
        System.out.printf("%3d word: %s%n", start, m.group());
      else if ( m.usePattern(pString).lookingAt() )
        System.out.printf("%3d string: %s%n", start, m.group());
      else if ( m.usePattern(pComment).lookingAt() )
        System.out.printf("%3d comment: %s%n", start, m.group());
      else if ( m.usePattern(pWS).lookingAt() )
        System.out.printf("%3d whitespace%n", start);
      else
        m.usePattern(sample).lookingAt();
        System.out.printf("Bad data: '%s'%n", m.group());
        System.exit(1);
      start = m.end();
}{code} Instead of using find() and letting the Matcher scan ahead for a match, you control where the match attempts start by using the region() and lookingAt() methods. Cycling through the regexes with the usePattern() method is very quick because the Matcher and the Patterns are all pre-instantiated. Just make sure the regexes are reasonably efficient and this should be plenty fast enough--at least, I've found it so.

Re: Which pattern for RMI scenario

Two different UIs talking to the same RMI service?
How does the service tell the difference between the
two?Basically the same way any other server distinguishes between its clients. It sends the response back to wherever the request came from.

I'd kind-of guessed it was uni work :-)
in all honesty, I wouldn't even approach the problem from a patterns perspective. all I see is a subsystem I don't want to deal with directly, so I define an interface to hide it behind. could argue that it's an Adapter, since it's taking the Http interface and abstracting away from it, to a java one. on the other hand, since mucking around with Http in java isn't exactly straight-forward, you're defining a more simple interface, so it could be considered a facade. which do you think is closer?
most people, once au fait with design patterns, think less in terms of those patterns, and more in terms of what OO principles to apply. score some extra credit by writing a passage about how design patterns are not prescriptive, and that many coders lift ideas about encapsulation and separation from patterns, rather than use the pattern exactly as described.

Which pattern best suites a diagram application?

Hi all,
I need to implement an application such as Rational Rose or Visio.
I am intending to use the mvc pattern as all the info i have points in this direction.
I think MVC, Decorator, mediator, builder, etc are all possible candidates but susspect that MVC is the best.
Can someone please either confirm this or point me in the right direction
Thanks in advance for any constructive criticism
Graham

Please explain what you mean by the application
scope?Asking, "Should I use Mediator or Director for this application I'm creating?" is like asking, "Should I use 2x4s or plywood for this house I'm building?"
You'll quite likely use more than one, and you don't use Mediator or Decroator or whatever for an application. You use them for smaller pieces of your app.
The application is quite simple as i see it and may
possibly be done without a pattern i only sugested a
pattern as a means of teaching myself (using a
pattern may possibly be incorrect).Whether you know it or not, you probably will end up using at least one pattern somewhere in your app. If you don't, there's a statistically good chance you've botched your design.
I say this not because I think your app needs a pattern, but rather because patterns were created to codify recurring solutions that people used. Those patterns tend to pop up naturally all over the place in well-designed apps, so there's a good chance you'd have done the same thing.
It's like asking "should I use a for loop for this app"? It's not at the app level that you need a for loop, but it's highly likely that you'll use one somewhere.

A web service design issue with patterns

Hello,
I�d like to ask for your help in the following design issue:
I need to create an email sending web service (with Axis). Only just one method which returns with an integer return code. This handles the following:
- based on the given parameters gets the email addresses from an
LDAP server (with netscape ldap for java)
-     makes a cache from them (only after a timeout period will be the cache
refreshed) (don�t know what tool to use for this)
-     selects html templates which to be sent based on the given parameters
-     sends emails with the appropriate templates (with Velocity)
-     the whole process is logged (with log4j)
I have to write the code as generic as possible. I know that some design pattern should be used for this. (some from GoF , and I know there exists design patterns specially created for web services as well).
Could you enumerate me which patterns (and for what part of the program) would be the best choice to solve this problem? I have read through some books about patterns, but don�t have the knowledge to pick up the right one for a concrete problem like this..
Thank you in advance,
nagybaly

Hello,
I�d like to ask for your help in the following design
issue:
I need to create an email sending web service (with
Axis). Only just one method which returns with an
integer return code. This handles the following:Lots of responsibilities here. You would do well to break this up into several classes that you can test separately.
I would also advise that you not embed all this in a servlet. Make a service that collaborates with several objects to accomplish the task and let the serlvet just call it.
.> - based on the given parameters gets the email
addresses from an
LDAP server (with netscape ldap for java)I'd recommend Spring's LDAP module. Pretty terrific stuff.
cache from them (only after a timeout period will be
the cache
refreshed) (don�t know what tool to use for
this)Maybe EhCache or OsCache or something like that.
-     selects html templates which to be sent based on
the given parametersWhere does this come from? Certainly not the LDAP. A relational database? Write a DAO for the document template.
-     sends emails with the appropriate templates (with
Velocity)Have an e-mail sender service using Java Mail.
-     the whole process is logged (with log4j)Easily done.
I have to write the code as generic as possible. I
know that some design pattern should be used for
this. No pattern. There might be patterns, if you say that the DAOs to access the LDAP and RDB are patterns.
Stop thinking patterns and start thinking objects.
(some from GoF , and I know there exists design
patterns specially created for web services as
well).Nope.
Could you enumerate me which patterns (and for what
part of the program) would be the best choice to
solve this problem? I have read through some books
about patterns, but don�t have the knowledge to pick
up the right one for a concrete problem like this..
Thank you in advance,
nagybalyYou haven't read them because they aren't there. Your problem is pretty specific, even if it's common.
%

How to apply patterns in Java desktop system

Dear experts,
I have developed a System which now only can be use through Browser, in other words,a WEB application for the System has developed which I use MVC pattern in it
now,I should develop a client software for some local customers to use system,but I have not any experiences in developing client desktop software,the main problem now is that I don't know which patterns to use?
Can you help me ? thanks!!!

Hi,
Implement the same MVC arch, but the client side which I suppose you are going to develope in Java AWT/Swing should call the controller (Servlet) using the java.net packages. This works very fine but needs some small hardships....
jHeaven

Design Patterns in OO-ABAP

Hi Everyone ,
What are design pattern in Object Oriented ABAP.
How will we know that which pattern suits the particular scenario.
Thanks
Sandeep

Hi,
yes its not free, but its really worth the money.
Other abap specific sources:
http://wiki.sdn.sap.com/wiki/display/ABAP/ABAPObjectsDesignPatterns-ModelViewController%28MVC%29
http://www.sdn.sap.com/irj/scn/weblogs;jsessionid=%28J2EE3417200%29ID0796789650DB21029243082976783901End?blog=/pub/wlg/606
/people/marcelo.ramos/blog/2008/04/30/sapmvc-a-new-mvc-for-classical-abap-dynpro
Greetings,
DSP

Pattern b/w Remote interface & Container implementation class

Which pattern is followed by EJB Remote interface & Container implementation class of that interface?Is there anyting mentioned in specs?
This questoin was asked to me by many people.I think it is Command design pattern as it hides away all the details of actual business implementation.but at same time I doubt if it is Facade?
Anyone who knows about this?
Thanx in advance
Sidhu

Rarely is software represent a single pattern, it typically represents multiple patterns.
Which pattern is followed by EJB Remote interfaceThe remote interface is an example of a facade pattern. This presents a public interface which is an abstraction of the real interface.
Container implementation class of that interface? The implementation is an example of what I think of as a double proxy pattern. That is acting as two distinct proxies. The first being the the remote callingof EJB standard functions via the Skelton implementation. I.E. The underlying EJB/RMI interface. The Second being a application level proxying of the business logic seen in most RL implementation.
The use of an UID ID beans is an example of a memento.
I think it is Command design pattern as it hides away all the
details of actual business implementation.Not directly, though an AppServer programmer may use the Command Pattern to resolve the remote connections. The User Application Programmer may also use this pattern. The key element of Command Pattern is the Invoker executing an concrete class via abstraction or interface of a polymorphic class. You can think of this as a specialisation of the
Martin

What kind of design pattern is this?

Hi ,
I am just learning the designpattern. So when I went through different kinds of design pattern, I got some doubts as it looks same some design patterns. could anybody please tell what kind of design pattern is the following one?
public interface IExporter{
void export();
public class ExcelExporter implements IExporter{
public void export(){
//TODO implementation
public class CVSExporter implements IExporter{
public void export(){
//TODO implementation
}thanks in advance..

Well - in structure, it is nearest to the Command pattern as far as I can tellOr Strategy. Or Builder. Several design pattenrs may share the same class structure, the difference is in the context, forces, and the parts one want to be flexible. And if someone wants to make it explicit which pattern is applied, they should name things accordingly.
As Saish said this example shows little more that inheritance at work. Not a pattern in itself, but a core element of the language. Trying to "identify" a pattern that is not obvious from the context is either:
- a sign that the original coder completely missed the point of using a pattern (which is, as Saish said too, assentially about communication)
- a sign that the maintenance coder is looking for patterns where there aren't
- an exercise question
but it differs in so much as its motivation is to polymorphically allow the use of different exporters rather than provide a set of action commands.That shouldn't count as a difference, merely as an "application" (it's perfectly valid to have a hierarchy of commands all devoted to exporting, although, as stated, if the original coder applied the Command pattern, he should have made it explicit, by renaming the interface, e.g. to ExportCommand).

ZCM Agent Inventory Scan - Patterns for Software Recognition

Hey Everyone,
Is is possible to find out which patterns the Inventory Scan uses to determine the installed Software products? (are there any local files on the agent-side with information what to look for?)
For some reason the Microsoft Office 2010 Professional Plus Installations wont be found any longer and I so far I cant figure out why this is happening (actually a few Office 2003 Products are shown, even on freshly installed Win7 Devices which have never seen any office Installation besides 2010)
Perhabs this might be related to the Office 2003 Compatibility Pack. This one was installed accidentally and I removed it via an uninstall bundle. Seemed to work fine, but ever since then Office 2010 wont be found within the inventory.
To test this behaviour I installed a clean win7 + Office 2010 + ZCM Agent. In this case Office 2010 is found.
(ZCM 10.3.1, PRU August 2011, Client OS: Win7 Enterprise 32 Bit)

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Examples for all service patterns and communication patterns.

Hi Friends,
Can anyone of you give me some real life examples for follwoing service/communication patterns?
1)Synchronous
2)Asynchronous
3)Request Confirmation
4)ReadQuery
5)Notification
6)Information
And also if any guidelined on when to use which patter etc...
Thanks in advance,
Best Regards,
Ujwal

Hi,
Suggestion is to refer SAP help for details:
1)Synchronous: when you need realtime response, i.e. you accept order and want to give order number to customer then you will call Sync service.
2)Asynchronous: when you dont need realtime response, i.e. you want to replicate all orders from one system to another system.
3)Request Confirmation: you made a request and system confirm your request. i.e. Order data is supplied and order number is confirmation. Database will be updated.
4)ReadQuery: I guess you are refering to Query/Response pattern, You just want some information. No database will be updated.
5)Notification: It is another form of "QueryResponse" but user action required.
6)Information: It is another form of "QueryRespone" but NO user action required.
Answer following questions to determine which pattern you need.
Q1. Do you need response?
Ans: Yes: Sync pattern
        Q1.1: Does any update required?
        Ans: Yes: RequestConfirmation pattern.
        Ans: No: QueryResponse pattern.
Ans: No
        Q1.2 Does user required to take notice of response?
        Ans: Yes:Notification pattern
        Ans: No: Information pattern.
Regards,
Gourav
Edited by: Gourav Khare on Jul 27, 2009 2:18 PM

My Factory Pattern

Here is the factory pattern I have implemented. I want to know, exactly which pattern this belongs to. I liked this. Comments and suggestions are welcome.
// ViewFactory.java
// Implementation of the Class ViewFactory
// Generated by Enterprise Architect
// Created on: 9/28/02
// Original author: Vijendra Kotian
// Modification history:
public class ViewFactory implements ViewFactoryInterface {
     private ViewFactoryInterface vf;
     protected ViewFactory(){
     public ViewFactory(String type){
          System.out.println("ViewFactory created");
          vf=createNewView(type);
     public void finalize() throws Throwable {
          super.finalize();
     private ViewFactoryInterface createNewView(String type){
          char c=(char)type.charAt(0);
          switch(c){
          case 'a':
          case 'A':
               return new AWTViewFactory();
          case 'm':
          case 'M':
               return new MotifViewFactory();
          return null;
     public void openView(ViewFactoryInterface param){
          vf=param;
     public void print(){
          if(vf!=null) vf.print();
          else System.out.println("Vf is null!!!");
     public static void main(String[] s){
          ViewFactoryInterface vf=new ViewFactory("MOTIF");
          vf.print();
          ViewFactoryInterface vf1=new ViewFactory("Awt");
          vf1.print();
          vf1.openView(vf);
          vf1.print();
          ViewFactoryInterface vf2=new ViewFactory();
          vf2.print();
public interface ViewFactoryInterface {
     public void print();
     public void openView(ViewFactoryInterface vfi);
import ViewFactory;
public class MotifViewFactory extends ViewFactory{
     public MotifViewFactory(){
          //super("Motif");
          System.out.println("New Motif view factory created");
     public void finalize() throws Throwable {
          super.finalize();
     public void print(){
          System.out.println("Motif print");
import ViewFactory;
public class AWTViewFactory extends ViewFactory{
     public AWTViewFactory(){
          //super("AWT");
          System.out.println("Awt View Factory created");
     public void finalize() throws Throwable {
          super.finalize();
     public void print(){
          System.out.println("AWT Print");
-Vijendra K

http://forum.java.sun.com/faq.jsp#messageformat

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