Best practice for JSF 2.0 composite component?

Following the various tutorials and blog entries I have found, I have managed to implement a few composite components. I want to do a more complex one, but haven't found and example yet to follow and my own proficiency in programming model isn't sufficient for me to determine the best way to do it.
What I would want to implement is something like the following example.
.. xmlns:mc="http://java.syn.com/jsf/composite/myComponent" ..
<mc:addTwo value="#{SomeBean.someProperty}" />The included component has two fields, which when the user inputs those the someProperty is set to some calculation of those two (for example adding them together). What I think I need to do is implement a backing bean for the "addTwo" component and do the calculation there. Then when that is done the composite backing bean needs to access the using page's SomeBean.someProperty setter. How is this done?
My actual intent is to make a component that looks up an entity in a data base based on a number of user inputs, then set the "someProperty" property to that value. If I could do the above example then I think I can apply the same principle, which is to have the composite component's backing bean access the someProperty property in the using page's bean via a #{cc.attrs.xxx} type reference. Am I on the right track?

this certainly seems like the place for JSF 2.0 discussions, yes.
It seems so obvious, was this forum called something else when this was posted perhaps?

Similar Messages

JSF - Best Practice For Using Managed Bean

I want to discuss what is the best practice for managed bean usage, especially using session scope or request scope to build database driven pages
---- Session Bean ----
- In the book Core Java Server Faces, the author mentioned that most of the cases session bean should be used, unless the processing is passed on to other handler. Since JSF can store the state on client side, i think storing everything in session is not a big memory concern. (can some expert confirm this is true?) Session objects are easy to manage and states can be shared across the pages. It can make programming easy.
In the case of a page binded to a resultset, the bean usually helds a java.util.List object for the result, which is intialized in the constructor by query the database first. However, this approach has a problem: when user navigates to other page and comes back, the data is not refreshed. You can of course solve the problem by issuing query everytime in your getXXX method. But you need to be very careful that you don't bind this XXX property too many times. In the case of querying in getXXX, setXXX is also tricky as you don't have a member to set. You usually don't want to persist the resultset changes in the setXXX as the changes may not be final, in stead, you want to handle in the actionlistener (like a save(actionevent)).
I would glad to see your thought on this.
--- Request Bean ---
request bean is initialized everytime a reuqest is made. It sometimes drove me nuts because JSF seems not to be every consistent in updating model values. Suppose you have a page showing parent-children a list of records from database, and you also allow user to change directly on the children. if I hbind the parent to a bean called #{Parent} and you bind the children to ADF table (value="#{Parent.children}" var="rowValue". If I set Parent as a request scope, the setChildren method is never called when I submit the form. Not sure if this is just for ADF or it is JSF problem. But if you change the bean to session scope, everything works fine.
I believe JSF doesn't update the bindings for all component attributes. It only update the input component value binding. Some one please verify this is true.
In many cases, i found request bean is very hard to work with if there are lots of updates. (I have lots of trouble with update the binding value for rendered attributes).
However, request bean is working fine for read only pages and simple binded forms. It definitely frees up memory quicker than session bean.
----- any comments or opinions are welcome!!! ------

I think it should be either Option 2 or Option 3.
Option 2 would be necessary if the bean data depends on some request parameters.
(Example: Getting customer bean for a particular customer id)
Otherwise Option 3 seems the reasonable approach.
But, I am also pondering on this issue. The above are just my initial thoughts.

Best Practice For Working on Composite In Team

Hello,
I would like to know what is the best practice for working on a single composite by mutiple members in a team.
We have a core services module wherein a single composite contains many services. So, to complete in time, we would like many members to work on it simultaneously.
In such scenarios, if some one adds a new adapter or some other services, composite.xml changes.
Saving it would override other member's changes. Also, it is not possible to apply lock simultaneously on the same file through some version control mechanism.
Please let us know what should be the best practice in such scenarios.
Thanks-
Ashish

You can very well use a version control software with JDev. You may refer -
http://www.oracle.com/technetwork/articles/soa/jimerson-config-soa-355383.html
I think without version control mechanism (like subversion) it won't be easy to work in a multi-developer environment. If you really don't have a source and version control mechanism then manual merging will be required which may be error prone and time & effort consuming.
Regards,
Anuj

Best practice for initializing objects in a JSF backing bean?

Hi,
What is the best practice for initializing some objects in the JSF to-page backing bean before the to-page is displayed for the first time? The initialization would vary and depend upon a command link in the from-page.
Regards,
Al Malin

f:view has two new attributes in 1.2: beforePhase and afterPhase
which allows you to specify a phase listener method
which will be called before and after the view is processed.

Best practice for multi-language content in common areas

I've got a site with some text in header/footer/nav that needs to be translated between an English and Spanish site, which use the same design. My intention was to set up all the text as content to facilitate. However, if I use a standard dialog with the component's path set to a child of the current page node, I would need to re-enter the text on every page. If I use a design dialog, or a standard dialog with the component's path set absolutely, the Engilsh and Spanish sites will share the same text. If I use a standard dialog with the component's path set relatively (eg path="../../jcr:content/myPath"), the pages using the component would all need to be at the same level of the hierarchy.
It appears that the Geometrixx demo doesn't address this situation, and leaves copy in English. Is there a best practice for this scenario?

I'm finding that something to the effect of <cq:include path="<%= strCommonContentPath + "codeEntry" %>" resourceType ...
works fine for most components, but not for parsys, or a component containing a parsys. When I attempt that, I get a JS error that says "design.path is null or not an object". Is there a way around this?

Best Practice for utility in Sol Man 4.0

We have software component ST-ICO of release 150_700 with Patch level 5
We want a Template Selection for Utility industry. I checked in
the service market place and found that 'Baseline Package United
Kingdom V1.50, Template: BP_BLKU150' is available in the above software
component.
But we are not getting any templates other than 'BP_UTUS147 - Best Practices for Water Utility' in the 'SOLAR_PROJECT_ADMIN'
transaction.
Kindly suggest any patch needs to be applied or some configuration need to be done.
Regards
Mani

Hi Mani,
Colud u plz give me the link of "where u find the template BP_BLKU150"?
It will be helpful for me.
Thanks
Senthil

Best Practices for Defining NDS Java Projects...

We are doing a Proof of Concept on using NDS to develop non-SAP Java applications. We are attempting to determine if we can replace our current Java development tools with NDS/WAS.
We are struggling with SAP's terminology and "plumbing" for setting up/defining Java projects. For example, what is and when do you define Tracks, Software Components, Development Components, etc. All of these terms are totally foreign to us and do not relate to our current Java environment (at least not that we can see). We are also struggling with how the DTR and activities tie in to those components.
If any one has defined best practices for setting up Java projects or has struggled with and overcome these same issues, please provide us with some guidance. This is a very frustrating and time-consuming issue for us.
Thank you!!

Hi Peggy,
In Component Model we divide software projects into small components.Components can use other components in well defined manner.
A development object is a part of a component that can be changed or developed in some way; it provides the component with a certain part of its functionality. A development object may be a Java class, a Web Dynpro view, a table definition, a JSP page, and so on. Development objects are always stored as sources in a repository.
A development component can be defined as a frame shared by a number of objects, which are part of the software.
Software components combine components (DCs) to larger units for delivery and deployment.
A track comprises configurations and runtime systems required for developing software component versions.It ensures stable states of deliverables used by subsequent tracks.
The Design Time Repository is for versioning source code management. Distributed development of software in teams. Transport and replication of sources.
You can also find lot of support in SDN for the above concepts with tutorials.
Refer this Link for a overview on Java development Infrastructure(JDI)
https://www.sdn.sap.com/irj/servlet/prt/portal/prtroot/com.sap.km.cm.docs/library/webas/java/java development infrastructure jdi overview.pdf
To understand further
Working with Net Weaver Development Infrastructure :
http://help.sap.com/saphelp_nw04/helpdata/en/03/f6bc3d42f46c33e10000000a11405a/content.htm
In the above link you can find all the concepts clearly explained.You can also find the required tutorials for development.
Regards,
Vijith

What is the best practice for changing view states?

I have a component with two Pie Charts that display
percentages at two specific dates (think start and end values).
But, I have three views: Start Value only, End Value only, or show
Both. I am using a ToggleButtonBar to control the display. What is
the best practice for changing this kind of view state? Right now
(since this code was inherited), the view states are changed in an
ActionScript function which sets the visible and includeInLayout
properties on each Pie Chart based on the selectedIndex of the
ToggleButtonBar, but, this just doesn't seem like the best way to
do this - not very dynamic. I'd like to be able to change the state
based on the name of the selectedItem, in case the order of the
ToggleButtons changes, and since I am storing the name of the
selectedItem for future reference.
Would using States be better? If so, what would be the best
way to implement this?
Thanks.

I would stick with non-states, as I have always heard that
states are more for smaller components that need to change under
certain conditions, like a login screen that changes if the user
needs to register.
That said, if the UI of what you are dealing with is not
overly complex, and if it will not become overly complex, maybe
states is the way to go.
Looking at your code, I don't think you'll save much in terms
of lines of code.

Best practice for integrating oracle atg with external web service

Hi All
What is the best practice for integrating oracle atg with external web service? Is it using integration repository or calling the web service directly from the java class using a WS client?
With Thanks & Regards
Abhishek

Using Integration Repository might cause performance overhead based on the operation you are doing, I have never used Integration Repository for 3rd Party integration therefore I am not able to make any comment on this.
Calling directly as a Java Client is an easy approach and you can use ATG component framework to support that by making the endpoint, security credentials etc as configurable properties.
Cheers
R
Edited by: Rajeev_R on Apr 29, 2013 3:49 AM

Best Practice for External Libraries Shared Libraries and Web Dynrpo

Two blogs have been written on sharing libraries with Web Dynpro DC, but I would
like to know the best practice for doing this.
External libraries seem to work great at compile time, but when deploying there is often an error related to the external library not being a deployed component.
Is there a workaround for this besides creating a shared J2EE library which I have been able to get working? I am not interested in something that works, but really
what are the best practice for this. What is the best way to limit the number of jars that need to be kept in a shared library/ext library. When is sharing ref service/etc a valid approach vs. hunting down the jars in the portal libraries etc and storing in an external library.

Security is mainly about mitigation rather than 100% secure, "We have unknown unknowns". The component needs to talk to SQL Server. You could continue to use http to talk to SQL Server, perhaps even get SOAP Transactions working but personally
I'd have more worries about using such a 'less trodden' path since that is exactly the areas where more security problems are discovered. I don't know about your specific design issues so there might be even more ways to mitigate the risk but in general you're
using a DMZ as a decent way to mitigate risk. I would recommend asking your security team what they'd deem acceptable.
http://pauliom.wordpress.com

Best practice for external but secure access to internal data?

We need external customers/vendors/partners to access some of our company data (view/add/edit). It’s not so easy as to segment out those databases/tables/records from other existing (and put separate database(s) in the DMZ where our server is). Our
current solution is to have a 1433 hole from web server into our database server. The user credentials are not in any sort of web.config but rather compiled in our DLLs, and that SQL login has read/write access to a very limited number of databases.
Our security group says this is still not secure, but how else are we to do it? Even if a web service, there still has to be a hole in somewhere. Any standard best practice for this?
Thanks.

Security is mainly about mitigation rather than 100% secure, "We have unknown unknowns". The component needs to talk to SQL Server. You could continue to use http to talk to SQL Server, perhaps even get SOAP Transactions working but personally
I'd have more worries about using such a 'less trodden' path since that is exactly the areas where more security problems are discovered. I don't know about your specific design issues so there might be even more ways to mitigate the risk but in general you're
using a DMZ as a decent way to mitigate risk. I would recommend asking your security team what they'd deem acceptable.
http://pauliom.wordpress.com

Best Practice for using multiple models

Hi Buddies,
     Can u tell me the best practices for using multiple models in single WD application?
    Means --> I am using 3 RFCs on single application for my function. Each time i am importing that RFC model under
    WD --->Models and i did model binding seperately to Component Controller. Is this is the right way to impliment multiple            models in single application ?

It very much depends on your design, but One RFC per model is definitely a no no.
Refer to this document to understand how should you use the model in most efficient way.
http://www.sdn.sap.com/irj/scn/go/portal/prtroot/docs/library/uuid/705f2b2e-e77d-2b10-de8a-95f37f4c7022?quicklink=events&overridelayout=true
Thanks
Prashant

What is best practice for conditional rendering?

i have a set of radio buttons that conditionally render another set, which in turn conditionally render a 3rd set.
i am doing this by using a valueChangeListener on an h:selectOneRadio
when i click yes on the 1st set it renders the 2nd set.
when i click yes on the 2nd set it renders the 3rd set.
when i click no on the 1st set now it correctly removes the 2nd & 3rd sets, the method also nulls the values.
when i click yes on the 1st set, it renders the 2nd set with the old values even though they were nulled. and i can see in the debugger they are still null.
so there seems to be an issue updating the model, but i dont know what that issue is. im sure it just has something to do with the way i am trying this conditional render. please see below for my first field and my valueChangeListener method.
any help with what is a best practice for this scenario would be greatly appreciated.
<h:panelGrid id="grid20a" columns="1">
                         <h:outputText value="Does this consult pertain to a specific "/>
                         <h:outputText value="planned or ongoing research project?: *"/>
                    </h:panelGrid>
                    <h:selectOneRadio id="specificResearch1" value="#{ethicsConsultBacking.bean.specificResearch}"
                         layout="lineDirection" required="true"
                         valueChangeListener="#{ethicsConsultBacking.processValueChangeSpecificResearch}">
                              <f:selectItems value="#{ethicsConsultBacking.yesNoMap}" />
                              <a4j:support event="onclick" reRender="form"/>
                    </h:selectOneRadio>
                    <h:message for="specificResearch1" styleClass="redText" />
public void processValueChangeSpecificResearch(ValueChangeEvent e) throws AbortProcessingException
          String newValue = e.getNewValue().toString();
          //reinitialize
          this.setRenderHumanSubjectResearch(false);
          this.setRenderIrbSection(false);
          this.setRenderIrbProtocolNumber(false);
          this.getBean().setHumanSubjectResearch(null);
          this.getBean().setPrimaryIrb(null);
          this.getBean().setIrbStatus(null);
          this.getBean().setIrbProtocolNumber(null);
          //check condition
          if (newValue.equalsIgnoreCase(this.YES))
               this.setRenderHumanSubjectResearch(true);
           * Clearing validation messages.
           * This will get around the issue with having a field
           * on the form that is both required & immediate.
          Iterator it = this.getFacesContext().getMessages();
          while (it.hasNext())
               it.next();
               it.remove();
          this.getFacesContext().renderResponse();
     }i also tried doing this another way by just using an action method attached to the a4j:support tag, but that introduced a different set of issue. so ill leave that out for now unless that is the direction someone would like to direct my issue in.
Thanks in advance

Similar issue is covered and explained here: [http://balusc.blogspot.com/2007/10/populate-child-menus.html]. Not sure if it solves your problem as you're using ajax4jsf whereas I don't, but it might give new insights. To the point you might need to bind the component(s) and use setValue(null) or setSubmittedValue(null).

Best practice for mouseless ADF applications

I am developing an ADF application where the users do not want to use the mouse.
So I would like to know if there are a best practice for this?
I am already using the accessKey functionality and subforms defaultCommand
But I have had problems setting focus to objects on a page like tables. I would like a button to return the focus to the table after it has made the command like delete.
I have implemented a solution where I have found inspiration several threads and other webpages (see below).
Is this solution okay?
Are there any problems with it?
I would also like to know if there are better pathways to go like
out of the box solutions,
http://www.oracle.com/technetwork/developer-tools/adf/learnmore/79-global-template-button-strategy-360139.pdf (are there an example implementation?), or
http://one-size-doesnt-fit-all.blogspot.dk/2010/11/adf-ui-shell-supporting-global-hotkeys.html
in advance thanks
Inspiration webpages
https://blogs.oracle.com/jdevotnharvest/entry/how_to_programmatically_set_focus
http://technology.amis.nl/2008/01/04/adf-11g-rich-faces-focus-on-field-after-button-press-or-ppr-including-javascript-in-ppr-response-and-clientlisteners-client-side-programming-in-adf-faces-rich-client-components-part-2/
how to Commit table by writting Java code in Managed Bean?
Table does not refresh and getting error as UIComponent is Null
A short description of the solution:
(jdeveloper version 11.1.1.2.0)
--- Example where I use onSetFocus in jsff page
<af:commandButton text="#{hrsusuiBundle.FOCUS}" id="cb10"
partialSubmit="true" accessKey="f"
shortDesc="Alt+Shift+F"
actionListener="#{managedBean_clientUtils.onSetFocus}">
<af:clientAttribute name="focusField" value="t1"/>
</af:commandButton>
--- Examples where I use doTableActionAndSetFocus in jsff page
--- There have to be a binding in the jsff page to delete, commit and rollback
<af:commandButton text="#{hrsusuiBundle.DELETE}" id="cb4"
accessKey="x"
shortDesc="Alt+Shift+X"
partialSubmit="true"
actionListener="#{managedBean_clientUtils.doTableActionAndSetFocus}">
<af:clientAttribute name="focusField" value="t1"/>
<af:clientAttribute name="actionField" value="Delete"/>
</af:commandButton>
<af:commandButton text="#{hrsusuiBundle.COMMIT}" id="cb5"
accessKey="s" shortDesc="Alt+Shift+S"
partialSubmit="true"
actionListener="#{managedBean_clientUtils.doTableActionAndSetFocus}">
<af:clientAttribute name="focusField" value="t1"/>
<af:clientAttribute name="actionField" value="Commit"/>
</af:commandButton>
<af:commandButton text="#{hrsusuiBundle.ROLLBACK}" id="cb6"
accessKey="z" shortDesc="Alt+Shift+Z"
partialSubmit="true"
actionListener="#{managedBean_clientUtils.doTableActionAndSetFocus}"
immediate="true">
<af:resetActionListener/>
<af:clientAttribute name="focusField" value="t1"/>
<af:clientAttribute name="actionField" value="Rollback"/>
</af:commandButton>
--- This is the java class I use
--- It is published in adfc-config.xml as a request scope managedbean
public class ClientUtils {
public ClientUtils() {
public void doTableActionAndSetFocus(ActionEvent event) {
RichCommandButton rcb = (RichCommandButton)event.getSource();
String focusOn = (String)rcb.getAttributes().get("focusField");
String actionToDo = (String)rcb.getAttributes().get("actionField");
UIComponent component = null;
String clientId = null;
component = JSFUtils.findComponentInRoot(focusOn);
clientId = component.getClientId(JSFUtils.getFacesContext());
if ( "Delete".equals(actionToDo) || "Commit".equals(actionToDo) || "Rollback".equals(actionToDo) ){
BindingContainer bindings = BindingContext.getCurrent().getCurrentBindingsEntry();
OperationBinding operationBinding = bindings.getOperationBinding(actionToDo);
Object result = operationBinding.execute();
AdfFacesContext.getCurrentInstance().addPartialTarget(component);
if (clientId != null) {
makeSetFocusJavaScript(clientId);
public static String onSetFocus(ActionEvent event) {
RichCommandButton rcb = (RichCommandButton)event.getSource();
String focusOn = (String)rcb.getAttributes().get("focusField");
String clientId = null;
if (focusOn.contains(":")) {
clientId = focusOn;
} else {
clientId = findComponentsClientIdInRoot(focusOn);
if (clientId != null) {
makeSetFocusJavaScript(clientId);
return null;
private static void writeJavaScriptToClient(String script) {
FacesContext fctx = FacesContext.getCurrentInstance();
ExtendedRenderKitService erks = null;
erks = Service.getRenderKitService(fctx, ExtendedRenderKitService.class);
erks.addScript(fctx, script);
public static void makeSetFocusJavaScript(String clientId) {
if (clientId != null) {
StringBuilder script = new StringBuilder();
//use client id to ensure component is found if located in
//naming container
script.append("var textInput = ");
script.append("AdfPage.PAGE.findComponentByAbsoluteId");
script.append ("('"+clientId+"');");
script.append("if(textInput != null){");
script.append("textInput.focus();");
script.append("}");
writeJavaScriptToClient(script.toString());
public static String findComponentsClientIdInRoot(String id) {
UIComponent component = null;
String clientId = null;
component = JSFUtils.findComponentInRoot(id);
clientId = component.getClientId(JSFUtils.getFacesContext());
return clientId;
}

Hi,
I am developing an ADF application where the users do not want to use the mouse. So I would like to know if there are a best practice for this?
Well HTML (and this is the user interface you see) follows a tab index navigation that you follow with "tab" and "shift+tab". Anything else is a short cut for which you use mnemonics (as you already do) or shortcuts (explained in http://one-size-doesnt-fit-all.blogspot.dk/2010/11/adf-ui-shell-supporting-global-hotkeys.html). There is a distinction to make between non-web environments (which I think you and your users have abackground in) and client desktop environments. Browsers block some keyboard functionality for their own purpose. So you may have to find a list of keys first that work across browsers. Unlike desktop clients, which allow you to "press a button" without the button to take focus, this cannot be done on the web. So you need to be clever here, avoiding buttons at all.
The following paper is about JavaScript in ADF and explains the basics for what Chris Muir explains in : http://one-size-doesnt-fit-all.blogspot.dk/2010/11/adf-ui-shell-supporting-global-hotkeys.html
http://www.oracle.com/technetwork/developer-tools/jdev/1-2011-javascript-302460.pdf
It has the outline for how to register short cut keys that perform a specific action (e.g. register ctrl+d to delete the current row you are on, or press F11 to execute a query (similar to Oracle Forms frmres files)). However, be aware that this includes some code you have to write (actually quite some code to be honest).
http://www.oracle.com/technetwork/developer-tools/adf/learnmore/79-global-template-button-strategy-360139.pdf (are there an example implementation?), or
http://one-size-doesnt-fit-all.blogspot.dk/2010/11/adf-ui-shell-supporting-global-hotkeys.html
Actually these are implementations as they come with example code for you to use and customize, do they? So what is this question asking for more ? Also note that global buttons don't quite have anything in common with the question you asked. I assume you want to see it as an implementation of the Forms toolbar that operates on the form or table the focus is in. This however does not work for the web as there is nothing that keeps track of which component has a focus and to what iterator (data block) it belongs. This would involve even more coding (though possibly doable)
Frank

"Best practice" for components calling components on different panels.

I'm very new to Swing. I have been learning from tutorials, but these are always relatively simple interfaces , in which every component and container is initialised and added in the constructor of a main JFrame (extension) object.
I would assume that more complex, real-world examples would have JPanels initialise themselves. For example, I am working on a project in which the JFrame holds multiple JPanels. One of these Panels holds a group of JToggleButtons (grouped in a ButtonGroup). The action event for each button involves calling the repaint method of one of the other Panels.
Obviously, if you initialise everything in the JFrame, you can simply have the ActionListener refer to the other JPanel directly, by making the ActionListener a nested class within the JFrame class. However, I would like the JPanels to initialise their own components, including setting the button actions, by using an extension of class JPanel which includes the ActionListeners as nested classes. Therefore the ActionListener has no direct access to JPanel it needs to repaint.
What, then, is considered "best practice" for allowing these components to interact (not simply in this situation, but more generally)? Should I pass a reference to the JPanel that needs to be repainted to the JPanel that contains the ActionListeners? Should I notify the main JFrame that the Action event has fired, and then have that call "repaint"? Or is there a more common or more correct way of doing this?
Similarly, one of the JPanels needs to use a field belonging to the JFrame that holds it. Should I pass a reference to this object to the JPanel, or should I have the JPanel use "getParent()", or some other method?
I realise there are no concrete answers to this query, but I am wondering whether there are accepted practices for achieving this. My instinct is to simply pass a JPanel reference to the JPanel that needs to call repaint, but I am unsure how extensible this would be, how tightly coupled these classes would become.
Any advice anybody could give me would be much appreciated. Sorry the question is so long-winded. :)

Hello,
nice to get feedback.
I've been looking at a few resources on this issue from my last post. In my application I have been using the Observer and Observable classes to implement the MVC pattern suggested by T.PD.(...)
Two issues (not fatal, but annoying) with this are:
-Observable is a class, not an interface; since most of my Observers already extend JPanel (or some such), I have had to create inner classes.
-If an Observer is observing multiple Observables, it will have to determine which Observer called its update() method (by using reference equality or class comparison or whatever). Again, a very minor issue, but something to keep in mind.I don't deem those issues are minor. The second one in particular, is rather annoying in terms of maintenance ("Err, remind me, which widget is calling this "update()" method?").
In addition to that, the Observable/Observer are legacy non-generified classes, that incurr a loosely-typed approach (the subject and context arguments to the update(Observable subject, Object context) methods give hardly any info in themselves, and they generally have to be cast to provide app-specific information.
Note that the "notification model" from AWT and Swing widgets is not Observer-Observable, but merely EventListener . Although we can only guess what reasons made them develop a specific notification model, I deem this essentially stems from those reasons.
The contrasting appraoches are discussed in this article from Bill Venners: The Event Generator Idiom (http://www.artima.com/designtechniques/eventgenP.html).
N.B.: this article is from a previous-millenary series of "Design Techniques" articles that I found very useful when I learned OO design (GUI or not).
One last nail against the Observer/Observable model: these are general classes that can be used regardless of the context (GUI/non-GUI code), so this makes it easier to forget about Swing threading rules when using them (essentially: is the update method called in the EDT or not).
If anybody has any information on the performance or efficiency of using Observable/ObserverI would be very surprised if this had any performance impact. If it had, that would mean that you have either:
- a lot of widgets that are listening to one another (and then the Mediator pattern is almost a must to structure such entangled dependencies). And even then I don't think there could be any impact below a few thousands widgets.
- expensive or long-running computation in the update methods. That's unrelated to the notification model itself.
- a lot of non-GUI components that use the Observer/Observable to communicate among themselves - all the more risk then, to have a GUI update() called outside the EDT, see remark above.
(or whether there are inbuilt equivalents for Swing components)See discussion above.
As far as your remark 2 goes (if one observer observes more than one subjects, the update() method contains branching logic) : this also occurs with the Event Delegation model indeed: for example, it is quite common that people complain that their actionPerformed() method becomes unwieldy when the same class listens for several JButtons.
The usual advice for this is, use anonymous listeners, each of which handles the event from only one source (and generally very close in code to the definition of that source), and that simply translates the "generic" event notification method into a specific method call of a Controller or Mediator .
Best regards.
J.
Edited by: jduprez on May 9, 2011 10:10 AM

Best practice for JSF 2.0 composite component?

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