Please do not double post to dev and user.
-- James Mitchell Web Developer/Struts Evangelist http://jakarta.apache.org/struts/ "People demand freedom of speech to make up for the freedom of thought which they avoid." - Soren Aabye Kierkegaard (1813-1855) ----- Original Message ----- From: "Jose Gonzalez Gomez" <[EMAIL PROTECTED]> To: <[EMAIL PROTECTED]>; <[EMAIL PROTECTED]> Sent: Monday, March 03, 2003 3:32 PM Subject: DynaActionForm and array types without size or initial > > Hello, > > I've been searching the list for this, but I haven't find any > solution. Whenever you use an indexed property in a DynaActionForm or > DynaValidatorActionForm you always must specify size or initial, as > failing to do so will cause Struts to give a null value to the property, > and this will cause a NPE when submitting a form with this bean. > > I think that one of the common scenarios for using an indexed > property is when you have a dynamic form, so you don't know the size of > the form in compile time. Think, for example, in a shopping cart where > you want to edit quantities of products, or details of a purchase order > where you want to select single details with checkboxes to remove them > in a single step. The only solution I have found in this kind of > scenarios is to create and prepopulate the bean, store it in session, > and retrieve it after submitting the form. Anyway, this has the problem > of resetting the values. > > Anybody of you has faced these problems? > > I've taken a look at the Struts code, and it seems it wouldn't be > difficult to change this behaviour and provide "dynamic" lists that > would back this indexed properties in DynaActionForms. Basically, the > change should be done in the initial method of FormPropertyConfig. A > lazy list from commons-collections (ListUtils) could be used only if the > implementation would provide not only on-the-fly creation of objects > when getting them, but also when setting them. I mean, if you, for > example, set the object in position 5, and the list is empty, create > default objects for positions 0-4 and add object in position 5. > Currently the lazy list only provides this behaviour when getting > objects. What do you think about this? Any committer that could comment > on this? > > Another problem for this is to create default objects for java > wrapper classes of primitive types, as they don't provide default > construtctors, but I guess this could be controlled and create objects > with default values (0 for numbers, false for booleans...). This makes > me think of the posibility of adding a new attribute to the > form-property tag, that specifies the initial value for newly created > objects inside the list, instead of specifying the initial value of the > whole list. What do you think? > > I include a possible implementation of inital using ListUtils.lazyList: > > public Object initial() { > > Object initialValue = null; > try { > final Class clazz = getTypeClass(); > if (clazz.isArray()) { > if (initial != null) { > initialValue = > ConvertUtils.convert(initial, clazz); > } else { > if( size > 0 ) { > initialValue = > Array.newInstance(clazz.getComponentType(), > size); > for (int i = 0; i < size; i++) { > try { > Array.set(initialValue, i, > > clazz.getComponentType().newInstance()); > } catch (Throwable t) { > ; // Probably does not have a zero-args > constructor > } > } > } else { > initialValue = > ListUtils.lazyList( new ArrayList( ), new > Factory() { > public Object create() { > try { > return > clazz.getComponentType().newInstance(); > } catch (Throwable t) { > return null; // Probably does > not have a zero-args constructor > } > } > } ); > } > } > } else { > if (initial != null) { > initialValue = ConvertUtils.convert(initial, clazz); > } else { > initialValue = clazz.newInstance(); > } > } > } catch (Throwable t) { > initialValue = null; > } > return (initialValue); > > } > > Regards > Jose > > > --------------------------------------------------------------------- > To unsubscribe, e-mail: [EMAIL PROTECTED] > For additional commands, e-mail: [EMAIL PROTECTED] --------------------------------------------------------------------- To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED]
