Michelle, thanks, now I got it.
The problem I see with the approach you describe is that it forces all the data conversions inside the ActionForm EmployeeVO // the following must be "Date" to make the VO a "business object" +getDateOfBirth:Date +setDateOfBirth(Date in):void EmployeeForm public void setDateOfBirth(String in) { // CONVERT THE IN STRING TO A DATE String convertedDate = ... getVO().setDate(convertedDate) } public String getDateOfBirth() { // CONVERT THE OUT DATE TO A STRING Date outDate = getVO().getDate(); return (convertDateToString(outDate)); } Furthermore, the "less typing" advantage is relatively small. You still have to code all your get/set and still need both Form and VO. And you need to add the conversion code. Or not? I guess that keeping the two totally separate and dealing with the mapping via a separate entity is another possible approach. I have written two "PropertyMappers" that do the following automatically for all matching get/set: FORM -> VO vo.setProperty(convertFormProperty(form.getProperty())) VO -> FORM form.setProperty(convertVOProperty(vo.getProperty())) It doesn't deal with validations nor anything else. It just maps forms and VOs. I'll be ready to share it with anybody interested as soon as I have properly tested it and added more javadoc. Thanks to everybody, this is a great list! Andrej -----Original Message----- From: Michelle Popovits [mailto:[EMAIL PROTECTED]] Sent: Thursday, November 22, 2001 7:21 PM To: Dmitri Colebatch Cc: [EMAIL PROTECTED]; [EMAIL PROTECTED] Subject: Re: Design question - Action Form vs Business Delegates/Value Obj ects Hi Dim, Your example is similar to my approach with the exception that you are still duplicating methods of the value object inside of the action form. Instead of including the individual accessors in the form, just include the accessor for the value object (see my original example)...much less unnecessary typing this way. When you need to access the value object properties in java you just cal the employeeForm.getEmployeeVo().getName() method and when you are in a jsp and want to bind the value object property to a text field you refer to the property as "employeeVo.name". HTH, Michelle ----- Original Message ----- From: "Dmitri Colebatch" <[EMAIL PROTECTED]> To: "Struts Users Mailing List" <[EMAIL PROTECTED]> Cc: <[EMAIL PROTECTED]> Sent: Thursday, November 22, 2001 5:34 PM Subject: RE: Design question - Action Form vs Business Delegates/Value Obj ects > Hi, > > I also agree with Michelle... > > I think what you are thinking is maybe you could use the struts form _as_ > the value object? imho this would be bad design, as the whole idea of > putting the logic in a separate tier is to have it not bound to any one > form of presentation. What Michelle is suggesting though, is something > like: > > public class EmployeeForm extends ActionForm > { > private EmployeeVO vo = new EmployeeVO(); > > public String getName() > { > return vo.getName(); > } > > public void setName(String name) > { > vo.setName(name); > } > > // and so on.... > > // get the vo > public EmployeeVO getEmployeeVO() > { > return vo; > } > } > > so say you have an action class: > > public class AddEmployeeAction() > { > public void perform( ... ) > { > EmployeeForm eform = (EmployeeForm) form; > employeeManager.add(eform.getEmployeeVO()); > } > } > > etc... very simplified example, but hopefully this is a bit clearer... I > use this all the time, and would be interested to hear what other ppl > think as well... > > cheers > dim > > On Thu, 22 Nov 2001, Sobkowski, Andrej wrote: > > > Michelle, > > > > thanks for your reply... but I'm not sure I understand your answer. Probably > > my message wasn't clear. > > > > To use an example, I have: > > > > EmployeeForm extends ActionForm > > +getName():String > > +getAge():String > > +getDateOfBirth():String > > > > EmployeeVO > > +getName():String > > +getAge():Integer > > +getDateOfBirth():Date > > > > EmployeeForm is a simple Struts mapping of the data displayed on the HTML > > page. EmployeeVO is the intermediate value/business object where the fields > > have a "real" meaning (a Date is a Date). > > > > I don't see the reasons of making EmployeeVO an instance variable of > > EmployeeForm. And EmployeeVO can not be used directly inside Struts to map > > data from an HttpRequest because (I think) that only Strings (and int?) can > > be handled in ActionForms. > > > > My question was somehow: should I get rid of EmployeeVO? It certainly makes > > the application cleaner but it may just be a "picky thing" that will simply > > waste resources. > > > > Thanks. > > > > Andrej > > -----Original Message----- > > From: Michelle Popovits [mailto:[EMAIL PROTECTED]] > > Sent: Thursday, November 22, 2001 4:13 PM > > To: [EMAIL PROTECTED] > > Cc: [EMAIL PROTECTED] > > Subject: Re: Design question - Action Form vs Business Delegates/Value > > Objects > > > > > > Hi, > > > > I suggest to not duplicate variables that are in your Value Objects in your > > form object. Instead include the value object as a member of the the form > > object. > > > > ie. > > > > Form class - below the AccountVo is a value object within the form bean > > > > public class AddAccountForm extends ActionForm { > > .... > > > > public AccountVo getAccount() { > > return account; > > } > > > > public void setAccount(AccountVo aAccount) { > > account = aAccount; > > } > > > > .... > > } > > > > Then, in your jsp you reference the accountvo members like so using the dot > > notation -- the property "account.password" gets converted to > > getAccount().getPassword() or getAccount().setPassword(value). > > > > <strutshtml:password property="account.password" size="30" maxlength="10" /> > > <strutshtml:text property="account.accountName" testexpr="eMail" size="60" > > maxlength="100" /> > > > > > > This feature of struts/javabeans is a real time saver in terms of > > development. Once something is in a value object then that value object > > gets passed from the back-end all the way to the front end without needing > > to touch any of it's attributes. And if you're editing the data on a web > > page when you submit the page the new data automatically gets set into the > > value object which can then be passed to the back end (no unnecessary > > handling of the data). > > > > HTH, > > Michelle > > > > >From: "Sobkowski, Andrej" <[EMAIL PROTECTED]> > > >Reply-To: "Struts Users Mailing List" <[EMAIL PROTECTED]> > > >To: "'Struts Users Mailing List'" <[EMAIL PROTECTED]> > > >Subject: Design question - Action Form vs Business Delegates/Value Objects > > >Date: Thu, 22 Nov 2001 13:28:05 -0500 > > > > > >Hello, > > > > > >we're working on a quite large project with J2EE (including EJBs) and we're > > >using Struts (we're still in the early phases). To design a "clean" > > >application, I've defined different "object conversions": > > >* Request phase > > >- the ActionForm is converted to a Value Object > > >- the Value Object is passed to the EJBs > > >* Response phase > > >- the EJBs return one ore more Value Objects > > >- the Value Object(s) is (are) converted back to ActionForms. > > > > > >I think it's a good approach, but: > > >- my ActionForm and Value Objects have an almost identical interface. The > > >main difference is that the ActionForm instance variables are always of > > >type > > >String while for the Value Object have "final types" information (Date, > > >Integer, whatever) > > >- the conversion "ActionForm to VO" and back is slowing down the > > >performance > > >as my EJBs often return hundreds of VOs (each one to be converted to an > > >ActionForm). > > >I know this can be improved by using paging (Page-by-Page iterator) on both > > >the back-end and the front-end; furthermore, I've written a small "mapper" > > >that uses extensively the Reflection API to automatically perform the > > >mapping and this probably has an impact on the overall performance. > > > > > >My question is: what are the best practices for this type of issues? Does > > >anybody have the same problems? Should I reduce the level of abstraction > > >between the layers? > > > > > >Thank you! > > > > > >Andrej > > > > > >PS. if you're interested, I can share the simple mapper. It's a very small > > >mapper (less than 15k) that works fine with my app. It's waaaaaaay less > > >complete than the mapper on Ted Husted's site but... > > > > > >-----Original Message----- > > >From: Jon.Ridgway [mailto:[EMAIL PROTECTED]] > > >Sent: Thursday, November 22, 2001 12:10 PM > > >To: 'Struts Users Mailing List' > > >Subject: RE: design question > > > > > > > > > > > > > > >-----Original Message----- > > >From: M`ris Orbid`ns [mailto:[EMAIL PROTECTED]] > > >Sent: 22 November 2001 16:54 > > >To: Struts-list (E-mail) > > >Subject: design question > > > > > >Hello > > > > > >I have several questions about design, "best practises": > > > > > >1) Where to store client's profile information (like login name) ? > > >session or system state bean ? > > > > > >Use the HttpSession. But be aware that you should put as little as possible > > >into the session. Large sessions do not work well in a cluster. > > > > > >2) How to create and use a system state bean ? > > > > > >System state bean should be in scope "session", shouldnt it ? > > > > > >Again put as little as possible in the session and avoid statefull session > > >beans. If you must put a bean in the session, make it as small as possible, > > >ideally it would just hold key info that can be used to request beans at > > >request level when needed. This is a trade off between performance and > > >scalability. > > > > > >3) Where to put business logic (where I invoke JDBC) ? > > > Should business logic class be a bean ? > > > > > >If you have an app server business logic should go into a stateless session > > >bean (BusinessService), which is invoked (via a BusinessDelegate) from a > > >struts Action class. If you are not using EJBs then the Action class should > > >still invoke a business delegate, but the delegate would simply create a > > >normal Java bean to act as the Business Service. The business service > > >(Stateless EJB or Java Bean) should delegate to another class to access a > > >datasource. If your are using EJBs this should be a CMP or BMP+DAO > > >depending > > >on your app server (EJB 2 compliant consider CMP, else try CMP if supported > > >but be prepared to subclass to a BMP+DAO at a later date). > > > > > >thanx in advance > > >Maris Orbidans > > > > > > > > >Jon Ridgway. > > > > > >-- > > >To unsubscribe, e-mail: > > ><mailto:[EMAIL PROTECTED]> > > >For additional commands, e-mail: > > ><mailto:[EMAIL PROTECTED]> > > > > > > _________________________________________________________________ > > Get your FREE download of MSN Explorer at http://explorer.msn.com/intl.asp > > >