[S2] Proposal: Povide an integrated reference link feature for UI tags
In many (but not only) CRUD applications you have to deal with referencing model objects, which have an associated view as well. For example, if you have an editContact view, you have a company select box in place referencing the company model entity, which has it's own editCompany view. A IMO common pattern in this case is to provide a direct link to the view for the referenced model object. For example, you could provide a small link symbol behind the select box, representing an a href=... / to the view for the referenced entity object. Another common usecase could be to provide a complex selection popup with sorting / filtering, if a simple select box would not be suitable. This could happen with a not editable textbox, being filled from the popup window you access from the link symbol beside the textbox. Due to the structure of out templates, it might get quite complicated to render such a link symbol outside the tag. If you use a table based template for example, you would want to render the symbol within the td encapsulating the select element. I would propose the following extension to our UI tags: 1. provide a referenceLink attribute 2. provide a referenceSymbol attribute 3. provide a referenceText attribute The rendering of a reference link would be triggered by the existence of a referenceLink attribute. The refernceSymbol attribute could have a common default pointing to a provided image, similar to tooltip. You could optionally provide another symbol or the keyword none if you dont like to have an image rendered. If the referenceText attribute is given, it render as the alt tag of the image, if not symbol attribute is set to none. In this case, it would be the text presented by an alternatively rendered a href= Our themes would provide a default view implementation of this feature, leaving it open to users to easily customize it their own need with simple template editing, since the needed attributes are provided in the tag model. Comments highly appreciated. Regards, Rene - To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED]
Re: Exception thrown in OGNL evaluation.
Rane, 2007/8/17, Rene Gielen [EMAIL PROTECTED]: Ruimo, see below Ruimo Uno schrieb: Hi, thanks for your comment. 2007/8/17, Rene Gielen [EMAIL PROTECTED]: It's no bug, it's a feature... The policy for model access (e.g. property calls) via expression evaluation is fail silent. It would cause tons of exceptions if ognl expression evaluation / property access would not swallow them. I feel it is overkill. The property getters in action classes may throw RuntimeException because of programming bugs. Even in this case, the current implementation just ignore the exception and the shown page will be just corrupted. We cannot show user friendly 'sorry page' because the Struts exception handler cannot get exception. You would not be able to use the most common use patterns without having to do exepction handling on the JSP page then! Think of a model object foo with a getter getFoo() in your a FooCrudAction. You have an editFoo.jsp. If you want to create a new foo entry, the sequence would be - invoke edit/create action, triggering execute() in FooCrudAction - render editFoo.jsp - submit form - invoke save action, triggering save() in FooCrudAction - on success, render editFoo.jsp if ognl would not swallow the exceptions, then placing simple tag like s:textfield label='Name' name=foo.name / would fail with NPE in first rendering if you did not provide a (unnecessary) this.foo=new Foo() in your execute() method, or a lazy getter. Just a simple example. But if you would change this behaviour, the showcase app code would need approximately an additional 10-15% more code just for doing unneeded initializations and exception handling. You won't get NPE in this scenario. Ognl automatically create instance for you. I believe you know about this feature. What if the execption is thrown? It will be thrown within JSP page handling, and swallowed there! Your OpenSessionInView Interceptor or any higher level layer would take no notice of the exception. Instead you would have to use the anti-pattern of exception handliing with in JSP code to present useful information. In the API specification for PageContext.handleException() states the following: --- If no error page is defined in the page, the exception should be rethrown so that the standard servlet error handling takes over. --- If my understanding is correct, the exception should be rethrown and the servlet layer can handle it. Most likely, you are doing business logic calls in your model access domain and you should think of moving any call with the possibility to get service relevant exceptions to the described business logic domain access methods. No, it is not 'business logc'. In 'open session in view' pattern, the db transaction is kept open until the view rendering finishies. If you call the property access method of the acction class, it calls the getter method of tne entity class. It triggers O/R mapping layer invocation and lazily accesses the database. As a result, some kind of system exception (such as SQLException) may be thrown while view rendering. This pattern is widely used, I'm using it myself in many applications. But where do you expect the exception? If you make sure that you have a foo object loaded from persistence layer, the the foo.getBars() call to a a lazy initialized collection of referenced objects should never fail due to _runtime_ problems you have to deal with. If, for example, for some reason your session is closed, you have to look for a design time problem - most commonly people forget about holding the session open (luckily we have OpenSessionInView). Closing the session should be fixed as a design bug. I agree with you at this point. But in this case, the system should show an user friendly 'sorry page' so that the user can perform appropriate action. As we cannot take all bugs out of our system, need a sfety net. If there is a network problem between ap server and db server, lazy loading will fail by system error. The best practice pattern for a displaying a foo object looks like this: - invoke showFoo.action?id=1 - prepare() method of your action: this.foo = fooService.getById(this.id) - handle any exception you like, or let it pop to the upper layers - on success, render showFoo.jsp - iterate over foo.bars in view - will be lazy initialized, but should not throw any exception is your design was proper My previous example may be poor to explain this issue. Sorry for that. But as I stated above, you still need to care about system exception and RuntimeException (thrown by programming bug). I am not talking about application exception. You can hardly avoid system error and programming bug by implementing logics in your code. but if there was an exception, and OGNL would pop it, you still would _never_ get it in your Interceptor - your container will swallow it when rendering the JSP. it's the same for saving etc as
Re: Exception thrown in OGNL evaluation.
Am Fr, 17.08.2007, 11:28, schrieb Ruimo Uno: Rane, 2007/8/17, Rene Gielen [EMAIL PROTECTED]: Ruimo, see below Ruimo Uno schrieb: Hi, thanks for your comment. 2007/8/17, Rene Gielen [EMAIL PROTECTED]: It's no bug, it's a feature... The policy for model access (e.g. property calls) via expression evaluation is fail silent. It would cause tons of exceptions if ognl expression evaluation / property access would not swallow them. I feel it is overkill. The property getters in action classes may throw RuntimeException because of programming bugs. Even in this case, the current implementation just ignore the exception and the shown page will be just corrupted. We cannot show user friendly 'sorry page' because the Struts exception handler cannot get exception. You would not be able to use the most common use patterns without having to do exepction handling on the JSP page then! Think of a model object foo with a getter getFoo() in your a FooCrudAction. You have an editFoo.jsp. If you want to create a new foo entry, the sequence would be - invoke edit/create action, triggering execute() in FooCrudAction - render editFoo.jsp - submit form - invoke save action, triggering save() in FooCrudAction - on success, render editFoo.jsp if ognl would not swallow the exceptions, then placing simple tag like s:textfield label='Name' name=foo.name / would fail with NPE in first rendering if you did not provide a (unnecessary) this.foo=new Foo() in your execute() method, or a lazy getter. Just a simple example. But if you would change this behaviour, the showcase app code would need approximately an additional 10-15% more code just for doing unneeded initializations and exception handling. You won't get NPE in this scenario. Ognl automatically create instance for you. I believe you know about this feature. Not when trying to read the property, only when applying values. The first invocation with null foo object will cause OGNL to try to read the property of the foo.name property and fail silently - no object will be created. This will happen when then parameters interceptor tries to apply values to the model (when invoking the save view) What if the execption is thrown? It will be thrown within JSP page handling, and swallowed there! Your OpenSessionInView Interceptor or any higher level layer would take no notice of the exception. Instead you would have to use the anti-pattern of exception handliing with in JSP code to present useful information. In the API specification for PageContext.handleException() states the following: --- If no error page is defined in the page, the exception should be rethrown so that the standard servlet error handling takes over. --- If my understanding is correct, the exception should be rethrown and the servlet layer can handle it. good point, my fault. But nevertheless, your controller should be responsible for deciding what to present, and where to dispatch to. This is commonly done with either having your action method return results other than success (eg. error then) or having your interceptor change the result after dealing with the exception. Most likely, you are doing business logic calls in your model access domain and you should think of moving any call with the possibility to get service relevant exceptions to the described business logic domain access methods. No, it is not 'business logc'. In 'open session in view' pattern, the db transaction is kept open until the view rendering finishies. If you call the property access method of the acction class, it calls the getter method of tne entity class. It triggers O/R mapping layer invocation and lazily accesses the database. As a result, some kind of system exception (such as SQLException) may be thrown while view rendering. This pattern is widely used, I'm using it myself in many applications. But where do you expect the exception? If you make sure that you have a foo object loaded from persistence layer, the the foo.getBars() call to a a lazy initialized collection of referenced objects should never fail due to _runtime_ problems you have to deal with. If, for example, for some reason your session is closed, you have to look for a design time problem - most commonly people forget about holding the session open (luckily we have OpenSessionInView). Closing the session should be fixed as a design bug. I agree with you at this point. But in this case, the system should show an user friendly 'sorry page' so that the user can perform appropriate action. As we cannot take all bugs out of our system, need a sfety net. If there is a network problem between ap server and db server, lazy loading will fail by system error. but how could the fooService.getById(this.id), executed by the prepare or action method succeed and the lazy reference getter fail just a few millies later, when the session is still open??? The best
DO NOT REPLY [Bug 20854] - Error with nesting tags in separate pages
DO NOT REPLY TO THIS EMAIL, BUT PLEASE POST YOUR BUG· RELATED COMMENTS THROUGH THE WEB INTERFACE AVAILABLE AT http://issues.apache.org/bugzilla/show_bug.cgi?id=20854. ANY REPLY MADE TO THIS MESSAGE WILL NOT BE COLLECTED AND· INSERTED IN THE BUG DATABASE. http://issues.apache.org/bugzilla/show_bug.cgi?id=20854 --- Additional Comments From [EMAIL PROTECTED] 2007-08-17 09:04 --- I think I have just hit the same problem i.e. cannot find bean with name in any scope when using two nested:iterates in the same tile. I am using struts 1.3.5 In which version has this bug been fixed? Is there a patch or workaround I can apply? I see in JIRA that a similar bug STR-1530 has just been reopened so i was wondering what the status was -- Configure bugmail: http://issues.apache.org/bugzilla/userprefs.cgi?tab=email --- You are receiving this mail because: --- You are the assignee for the bug, or are watching the assignee. - To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED]
Re: Ajax Theme
I haven't dived into this part of the source code, but I've beent taking The ajax validation depends on DWR to mean that we use DWR to call the usual server-side validators from client-side ajax code. Is that correct? Is the use of DWR changing from 2.0.x to 2.1.x? Does the YUI Ajax plugin support validation? Has anyone tried the YUI plugin against the head? (And just to make our question day complete:) Do we want to bundle the Dojo plugin with Struts 2.1.x, or do we want to consider moving it to a Google Code site (perhpas with YUI), while it is still experimental: -Ted. On 8/15/07, Musachy Barroso [EMAIL PROTECTED] wrote: The ajax validation depends on DWR musachy On 8/15/07, Ian Roughley [EMAIL PROTECTED] wrote: Is the ajax theme in the 2.0.x branch completely Dojo driven now? If so, there seems to be a lot of DWR code that could be removed (i.e. from the web.xml and form.ftl). I can open a ticket if this is the case. /Ian - To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED] -- Hey you! Would you help me to carry the stone? Pink Floyd - To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED] -- HTH, Ted http://www.husted.com/ted/blog/ - To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED]
Re: [S2] Proposal: Povide an integrated reference link feature for UI tags
If I understand the use case, in my own applications, we done things like add a separate button to the page to do things like edit or add a company. (Are we distinguishing between insert and update?) It is a common UI need. In the case of select controls, some applications handle this sort of thing with a meta-item, like add new item that is part of the list. I can remember elder versions of Quicken doing this, though I note later versions have moved to buttons and menu bar items for adding or editing items. I can see how adding the feature to the template might be useful. Though, in the case of editing items in an enterprise application, the notion of user roles can come into play. Some users might be authorized to add items, and others might not. -Ted. On 8/17/07, Rene Gielen [EMAIL PROTECTED] wrote: In many (but not only) CRUD applications you have to deal with referencing model objects, which have an associated view as well. For example, if you have an editContact view, you have a company select box in place referencing the company model entity, which has it's own editCompany view. A IMO common pattern in this case is to provide a direct link to the view for the referenced model object. For example, you could provide a small link symbol behind the select box, representing an a href=... / to the view for the referenced entity object. Another common usecase could be to provide a complex selection popup with sorting / filtering, if a simple select box would not be suitable. This could happen with a not editable textbox, being filled from the popup window you access from the link symbol beside the textbox. Due to the structure of out templates, it might get quite complicated to render such a link symbol outside the tag. If you use a table based template for example, you would want to render the symbol within the td encapsulating the select element. I would propose the following extension to our UI tags: 1. provide a referenceLink attribute 2. provide a referenceSymbol attribute 3. provide a referenceText attribute The rendering of a reference link would be triggered by the existence of a referenceLink attribute. The refernceSymbol attribute could have a common default pointing to a provided image, similar to tooltip. You could optionally provide another symbol or the keyword none if you dont like to have an image rendered. If the referenceText attribute is given, it render as the alt tag of the image, if not symbol attribute is set to none. In this case, it would be the text presented by an alternatively rendered a href= Our themes would provide a default view implementation of this feature, leaving it open to users to easily customize it their own need with simple template editing, since the needed attributes are provided in the tag model. Comments highly appreciated. Regards, Rene - To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED]
Re: Ajax Theme
On 2.1 ajax validation will be provided by Dojo by default, but other libraries can be used easily, (with prototype example): http://struts.apache.org/2.x/docs/ajax-validation.html musachy On 8/17/07, Ted Husted [EMAIL PROTECTED] wrote: I haven't dived into this part of the source code, but I've beent taking The ajax validation depends on DWR to mean that we use DWR to call the usual server-side validators from client-side ajax code. Is that correct? Is the use of DWR changing from 2.0.x to 2.1.x? Does the YUI Ajax plugin support validation? Has anyone tried the YUI plugin against the head? (And just to make our question day complete:) Do we want to bundle the Dojo plugin with Struts 2.1.x, or do we want to consider moving it to a Google Code site (perhpas with YUI), while it is still experimental: -Ted. On 8/15/07, Musachy Barroso [EMAIL PROTECTED] wrote: The ajax validation depends on DWR musachy On 8/15/07, Ian Roughley [EMAIL PROTECTED] wrote: Is the ajax theme in the 2.0.x branch completely Dojo driven now? If so, there seems to be a lot of DWR code that could be removed (i.e. from the web.xml and form.ftl). I can open a ticket if this is the case. /Ian - To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED] -- Hey you! Would you help me to carry the stone? Pink Floyd - To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED] -- HTH, Ted http://www.husted.com/ted/blog/ - To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED] -- Hey you! Would you help me to carry the stone? Pink Floyd - To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED]
