Re: [EJB] Design Patterns (was JavaReport ...)
I was on this track in another thread where I was saying... What if ActionForm was an inner class to a Value object. Or, what if a Value object had a reference to an ActionForm which when filling with parameters we did ActionFormValue.getActionForm(), filled it, complete does it exist checking and non-business object validation checking, and then do a ActionFormValue.setActionForm(ActionForm myform) to set it back, which would fill the ActionFormValue object with the values in the ActionForm. An ActionValue could hold 1 or more ActionsForm(s) , or could take ActionForm as a parameter, with which it would copy and nativeize the data in the ActionForm. In this case an ActionValue would hold specific fileds for the beans it uses. My point here,though I hope it is apparent, is that we need to send value ojects through the system in a way in which it can complement/work with Struts. - Original Message - From: Ted Husted [EMAIL PROTECTED] To: [EMAIL PROTECTED] Sent: Thursday, June 21, 2001 8:03 AM Subject: Re: [EJB] Design Patterns (was JavaReport ...) What I'm working on now are patterns for Struts development that can be used with or without Enterprise Beans. As mentioned, the J2EE blueprints are mostly about development patterns, and Enterprise Beans are one part of implementating those patterns. This work is the second part of the Strut by Strut series (Stepping out). I had a long discussion with a BEA Weblogic employee the other day about this very thing. I think we need to more strongly seperate the J2EE patterns from the Enterprise Bean implementation. The idea being we should introduce people to the pattern first (presentation beans / data access beans / value object beans / helper beans), and then show where Enterprise Beans plug into that. Or, where you would roll your own. On the Struts front, while it is often the case that the ActionForm beans end up looking like many of your internal beans, there are important differences. For example, ActionForm beans should be immutable except by the actor, meanwhile many of your internal beans should be immutable except by the model. ActionForm beans need to use Strings as the primary type, but your internal beans may need native types to commune with the business logic beans. You really only need ActionForm beans to get input from the actor. When sending read-only views back, you can use any kind of bean you want (with the bean tags), so long as it has a reasonable toString(). It seems wasteful at first, but in the big picture, it seems like treating ActionForm beans as HTTPD throw-aways is the only way to keep the application loosely coupled, and able to attach to other environments later. Of course, data transfer becomes a big issue when you have to ferry things from ActinForm beans to data-access beans (and then back again in the case of an update). What I'm looking at now is using hashmaps as a standard data transfer agent. If the ActionForm can return a hashmap that matches the data access bean you can use BeanUtil.populate() to make the switch. Coming back later, if the value object bean returns a hashmap, you can use BeanUitl.populate() to fill your ActionForm bean (for an update). This would mean that your ActionForm bean design knows about your value object bean design, but I think that's OK (though the inverse would not be OK). -- Ted Husted, Husted dot Com, Fairport NY USA. -- Custom Software ~ Technical Services. -- Tel 716 737-3463. -- http://www.husted.com/about/struts/ SCHACHTER,MICHAEL (HP-NewJersey,ex2) wrote: To Anyone It Concerns, Although I'm relatively new to EJB's, I'm listed on the 1.1 TODO list to add better EJB support/design patterns. Ideas that anyone has about things that they'd like Struts to do with EJB's will definately help me along with this and help Struts quiet this EJB fud. I'm looking to get started on this soon, and anyone who wants to is more than welcome to help me out. - Mike
Re: [EJB] Design Patterns (was JavaReport ...)
What you have here is: 1) an immutable from the web tier 2) an immutable from the enterprise tier 3) a need to update each other Maybe they are immutable as far as standard get/set methods. However, they can also implement an interface which uses separate secondary fileds which start with the original values, and CAN be updated. In this way the 2 original models (the web tier ActionForm and the EJB model) can have the original values untouched, and the new secondary fields will hold and provide the updated state. - Original Message - From: Ted Husted [EMAIL PROTECTED] To: [EMAIL PROTECTED] Sent: Thursday, June 21, 2001 8:03 AM Subject: Re: [EJB] Design Patterns (was JavaReport ...) What I'm working on now are patterns for Struts development that can be used with or without Enterprise Beans. As mentioned, the J2EE blueprints are mostly about development patterns, and Enterprise Beans are one part of implementating those patterns. This work is the second part of the Strut by Strut series (Stepping out). I had a long discussion with a BEA Weblogic employee the other day about this very thing. I think we need to more strongly seperate the J2EE patterns from the Enterprise Bean implementation. The idea being we should introduce people to the pattern first (presentation beans / data access beans / value object beans / helper beans), and then show where Enterprise Beans plug into that. Or, where you would roll your own. On the Struts front, while it is often the case that the ActionForm beans end up looking like many of your internal beans, there are important differences. For example, ActionForm beans should be immutable except by the actor, meanwhile many of your internal beans should be immutable except by the model. ActionForm beans need to use Strings as the primary type, but your internal beans may need native types to commune with the business logic beans. You really only need ActionForm beans to get input from the actor. When sending read-only views back, you can use any kind of bean you want (with the bean tags), so long as it has a reasonable toString(). It seems wasteful at first, but in the big picture, it seems like treating ActionForm beans as HTTPD throw-aways is the only way to keep the application loosely coupled, and able to attach to other environments later. Of course, data transfer becomes a big issue when you have to ferry things from ActinForm beans to data-access beans (and then back again in the case of an update). What I'm looking at now is using hashmaps as a standard data transfer agent. If the ActionForm can return a hashmap that matches the data access bean you can use BeanUtil.populate() to make the switch. Coming back later, if the value object bean returns a hashmap, you can use BeanUitl.populate() to fill your ActionForm bean (for an update). This would mean that your ActionForm bean design knows about your value object bean design, but I think that's OK (though the inverse would not be OK). -- Ted Husted, Husted dot Com, Fairport NY USA. -- Custom Software ~ Technical Services. -- Tel 716 737-3463. -- http://www.husted.com/about/struts/ SCHACHTER,MICHAEL (HP-NewJersey,ex2) wrote: To Anyone It Concerns, Although I'm relatively new to EJB's, I'm listed on the 1.1 TODO list to add better EJB support/design patterns. Ideas that anyone has about things that they'd like Struts to do with EJB's will definately help me along with this and help Struts quiet this EJB fud. I'm looking to get started on this soon, and anyone who wants to is more than welcome to help me out. - Mike
Re: [EJB] Design Patterns (was JavaReport ...)
The ActionForm beans can contain nested references, so you could just set some other bean to it, then refer to myBean.propertyThis and myBean.propertyThat. Of course, the other bean would have to have standard String accessor and mutators, which is where it starts to fall down. The other beans may need to use native types, and would want to reject or transform an incoming String value being set to type. So if you need two storage locations, joining the two classes loses its edge. In general, I would say that ActionForms can be coupled to other beans, but other beans should not be coupled to ActionForm bean (import the Struts class). Because, in another environment, the ActionForm beans might be replaced with another class that hooked up to non-HTTP user interface (say, Swing), and we would want to be able to drop those in. Of course, the other beans could be designed to accept values from any given JavaBean via reflection, which would include an ActionForm bean. It's my feeling that proper MVC/J2EE design implies that we are going to be stuck with a set of ActionForm beans and a set of other beans, and need to find the best way to transfer data between the two. Jonathan Asbell wrote: I was on this track in another thread where I was saying... What if ActionForm was an inner class to a Value object. Or, what if a Value object had a reference to an ActionForm which when filling with parameters we did ActionFormValue.getActionForm(), filled it, complete does it exist checking and non-business object validation checking, and then do a ActionFormValue.setActionForm(ActionForm myform) to set it back, which would fill the ActionFormValue object with the values in the ActionForm. An ActionValue could hold 1 or more ActionsForm(s) , or could take ActionForm as a parameter, with which it would copy and nativeize the data in the ActionForm. In this case an ActionValue would hold specific fileds for the beans it uses. My point here,though I hope it is apparent, is that we need to send value ojects through the system in a way in which it can complement/work with Struts.
RE: [EJB] Design Patterns (was JavaReport ...)
I would suggest using interfaces to talk to the Actions / Action Forms. This way there would be no confusion about importing the struts libraries when the users want to change the front end framework to say Cocoon (or) Velocity. Just my 0.02$ cheers, Amar.. -Original Message- From: Ted Husted [mailto:[EMAIL PROTECTED]] Sent: Thursday, June 21, 2001 9:04 AM To: [EMAIL PROTECTED] Subject: Re: [EJB] Design Patterns (was JavaReport ...) The ActionForm beans can contain nested references, so you could just set some other bean to it, then refer to myBean.propertyThis and myBean.propertyThat. Of course, the other bean would have to have standard String accessor and mutators, which is where it starts to fall down. The other beans may need to use native types, and would want to reject or transform an incoming String value being set to type. So if you need two storage locations, joining the two classes loses its edge. In general, I would say that ActionForms can be coupled to other beans, but other beans should not be coupled to ActionForm bean (import the Struts class). Because, in another environment, the ActionForm beans might be replaced with another class that hooked up to non-HTTP user interface (say, Swing), and we would want to be able to drop those in. Of course, the other beans could be designed to accept values from any given JavaBean via reflection, which would include an ActionForm bean. It's my feeling that proper MVC/J2EE design implies that we are going to be stuck with a set of ActionForm beans and a set of other beans, and need to find the best way to transfer data between the two. Jonathan Asbell wrote: I was on this track in another thread where I was saying... What if ActionForm was an inner class to a Value object. Or, what if a Value object had a reference to an ActionForm which when filling with parameters we did ActionFormValue.getActionForm(), filled it, complete does it exist checking and non-business object validation checking, and then do a ActionFormValue.setActionForm(ActionForm myform) to set it back, which would fill the ActionFormValue object with the values in the ActionForm. An ActionValue could hold 1 or more ActionsForm(s) , or could take ActionForm as a parameter, with which it would copy and nativeize the data in the ActionForm. In this case an ActionValue would hold specific fileds for the beans it uses. My point here,though I hope it is apparent, is that we need to send value ojects through the system in a way in which it can complement/work with Struts.
Re: [EJB] Design Patterns (was JavaReport ...)
Why is it that each bean (includeing the containing bean) could not have BOTH String get/set and also native type get/set? - Original Message - From: Ted Husted [EMAIL PROTECTED] To: [EMAIL PROTECTED] Sent: Thursday, June 21, 2001 9:03 AM Subject: Re: [EJB] Design Patterns (was JavaReport ...) The ActionForm beans can contain nested references, so you could just set some other bean to it, then refer to myBean.propertyThis and myBean.propertyThat. Of course, the other bean would have to have standard String accessor and mutators, which is where it starts to fall down. The other beans may need to use native types, and would want to reject or transform an incoming String value being set to type. So if you need two storage locations, joining the two classes loses its edge. In general, I would say that ActionForms can be coupled to other beans, but other beans should not be coupled to ActionForm bean (import the Struts class). Because, in another environment, the ActionForm beans might be replaced with another class that hooked up to non-HTTP user interface (say, Swing), and we would want to be able to drop those in. Of course, the other beans could be designed to accept values from any given JavaBean via reflection, which would include an ActionForm bean. It's my feeling that proper MVC/J2EE design implies that we are going to be stuck with a set of ActionForm beans and a set of other beans, and need to find the best way to transfer data between the two. Jonathan Asbell wrote: I was on this track in another thread where I was saying... What if ActionForm was an inner class to a Value object. Or, what if a Value object had a reference to an ActionForm which when filling with parameters we did ActionFormValue.getActionForm(), filled it, complete does it exist checking and non-business object validation checking, and then do a ActionFormValue.setActionForm(ActionForm myform) to set it back, which would fill the ActionFormValue object with the values in the ActionForm. An ActionValue could hold 1 or more ActionsForm(s) , or could take ActionForm as a parameter, with which it would copy and nativeize the data in the ActionForm. In this case an ActionValue would hold specific fileds for the beans it uses. My point here,though I hope it is apparent, is that we need to send value ojects through the system in a way in which it can complement/work with Struts.
Re: [EJB] Design Patterns (was JavaReport ...)
They could. This is especially convenient when your value object bean
contains a RowSet, since the *String versions are already built in. So,
you end up with something like
thisForm.set(
thisValue.getItemString(),
thisValue.getDonorString(),
thisValue.getDonorAnonString(),
thisValue.getCategoryString(),
thisValue.getPricelessString(),
thisValue.getScriptString(),
thisValue.getHasImageString(),
thisValue.getShippingString(),
thisValue.getItemTypeString(),
thisValue.getNameString(),
thisValue.getMarketString(),
thisValue.getMinimumString(),
thisValue.getIncrementString(),
thisValue.getSaleTypeString(),
thisValue.getQtyReceivedString(),
thisValue.getShippableString(),
thisValue.getWeightString(),
thisValue.getLocationString()
);
where thisValue.getItemString() does something like
/**
* Return the item as String
*
* @return the item as String
*/
public String getItemString() throws SQLException {
return values.getString(item);
}
// ... and
thisValue.setString(
thisForm.getItem(),
thisForm.getDonor(),
thisForm.getDonorAnon(),
thisForm.getCategory(),
thisForm.getPriceless(),
thisForm.getScript(),
thisForm.getHasImage(),
thisForm.getShipping(),
thisForm.getItemType(),
thisForm.getName(),
thisForm.getMarket(),
thisForm.getMinimum(),
thisForm.getIncrement(),
thisForm.getSaleType(),
thisForm.getQtyReceived(),
thisForm.getShippable(),
thisForm.getWeight(),
thisForm.getLocation()
);
where setString does something like
values.updateString(item,item);
I'm just looking for the least intrusive, most flexible pattern.
The nice part about a map is that it works well as part of an interface,
encapsulates the accessors within a toMap() method, and that mutators
can be called through reflection (e.g. BeanUtil.populate()).
Jonathan wrote:
Why is it that each bean (includeing the containing bean) could not have
BOTH String get/set and also native type get/set?
Re: [EJB] Design Patterns (was JavaReport ...)
On Thu, 21 Jun 2001, Jonathan wrote:
Why is it that each bean (includeing the containing bean) could not have
BOTH String get/set and also native type get/set?
You can only do this if you use different property names for the same
property. Otherwise, you'll get compile errors on something like this:
public Date getStartDate() { ... }
public String getStartDate() { ... }
or you will violate the naming conventions in the JavaBeans Specification:
public void setStartDate(Date startDate) { ... }
public void setStartDate(String startDate) { ... }
and your startDate property will not be recognized by the introspection
logic.
Craig
