Re: [Springframework-developer] Proposition for "controlled" copy of java bean properties

[Juergen H. <ju...@in...>]

Thanks for the suggestion, Adelino!

I've added such a "copyProperties(Object source, Object target, Class
editable)" variant to BeanUtils, although adapted into the existing
BeanUtils copyProperties implementation.

By coincidence, I have already reworked the BeanUtils copyProperties
implementation for Spring 1.2.6 already, to properly ignore properties not
found in the target class (but found in the source class), even if not
explicitly specified as "ignoreProperties".

This will be part of the next nighly 1.2.6 snapshot. Please give it a try
and let me know whether it works for you!

Juergen
 

-----Original Message-----
From: spr...@li...
[mailto:spr...@li...] On Behalf Of
Rodrigues Adelino
Sent: Tuesday, November 08, 2005 11:12 AM
To: spr...@li...
Subject: [Springframework-developer] Proposition for "controlled" copy of
java bean properties

Hi,

PROBLEM DESCRIPTION

Today BeanUtils in Spring offers the possibility to copy properties between
2 java beans:

static void copyProperties(Object source, Object target) static void
copyProperties(Object source, Object target, String[] ignoreProperties) 
 
As the instrospection does not
care about how the target variable was declared, calling such a method will
copy more properties that one wants.

To illustrate this point, let's consider the following types:

interface EditablePriceableItem {
	public int getPrice();
	public void setPrice(int val);
}


class PurchaseItem implements EditablePriceableItem {
	//... attributes
	public String getPurchaseNr() { ... }
	public void setPurchaseNr(String nr) { ... }
	public int getPrice() { ... } ;
	public void setPrice(int val) { ... };
}

class Project implements EditablePriceableItem {
	//... attributes
	public String getDescription() { ... }
	public void setDescription(String desc) { ... }
	public int getPrice() { ... } ;
	public void setPrice(int val) { ... };
}

Somewhere in a class, we have:

	EditablePriceableItem priceableSrc;
	EditablePriceableItem priceableTarget;

	//(1)
	// ...
	// priceableSrc is set by some method
	// ...
	//
	//(2)
	// priceableTarget gets instanciated
	// ...

	//(3)
	//Now I want to copy Priceable properties (and only priceable
properties !)
	//from priceableSrc to priceableTarget
	BeanUtils.copyProperties(priceableSrc,priceableTarget);

Although variables are declared as EditablePriceableItem, what gets copied
in (3) depends on the concrete type of priceableSrc and priceableTarget.

a) When priceableSrc and priceableTarget are instances of PurchaseItem,
	price and purchaseNr are copied
b) When priceableSrc and priceableTarget are instances of Project,
	price and description are copied
c) When priceableSrc is an instance of PurchaseItem and priceableTarget
    is an instance of Project (or the opposite) only price gets copied

As a conclusion the behaviour in (3) is not uniform.


PROPOSITION
To control the scope of properties that are copied, it would be very useful
to have a method such as:

static void copyProperties(Object source, Object target, Class
editableScope)

where editableScope is an interface or class that declares the properties.
Writing (3) as:

	BeanUtils.copyProperties(priceableSrc,priceableTarget,
	                         EditablePriceableItem.class);

would provide a consistent behaviour.

What do you think of this?



Regards, Adelino.

P.S.: Here attached a simple implementation of such method.


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