[BEANUTILS-526] copyProperty should instantiate nested properties

• Type: Bug
• Status: Open
• Priority: Major
• Resolution: Unresolved
• Affects Version/s: 1.9.4
• Component/s: Bean / Property Utils
• Assignee: Unassigned
• Reporter: Marco Janc
• Created: 07/Oct/19 11:45
• Updated: 07/Oct/19 11:48

Description

The function BeanUtils.copyProperty(bean, name, value) shall instantiate nested properties before copying them.

 

Example:

 

class Foo
{
 Bar bar;
}

class Bar
{
 int id;
}

 

 

We now have an instance of Foo where bar property is null and call:

 

Foo foo = new Foo();
BeanUtils.copyProperty(foo, "bar.id", 3);

This will throw an exception currently.

 

Workaround

In my generic copy method, i instantiate all required nested properties before. Here my implementation. In BeanUtils this could be done more lazy when the target is null.

 

	/**
	 * Instantiates the nested properties of the given Object with proxy Objects
	 * with the given property fieldname.
	 *
	 * @param obj
	 * @param fieldName
	 *
	 * @throws NoSuchMethodException
	 * @throws InvocationTargetException
	 * @throws IllegalAccessException
	 * @throws InstantiationException
	 */
	public static void instantiateNestedProperties(final Object obj, final String fieldName)
		throws IllegalAccessException, InvocationTargetException, NoSuchMethodException, InstantiationException
	{
		final String[] fieldNames = fieldName.split("\\.");
		if (fieldNames.length == 1)
			return;		final StringBuffer nestedProperty = new StringBuffer();		// outsource temporary variables to optimize performance
		String fn = null;
		Object value = null;
		PropertyDescriptor propertyDescriptor = null;
		Class<?> propertyType = null;
		Object newInstance = null;		for (int i = 0; i < fieldNames.length - 1; i++)
		{
			fn = fieldNames[i];
			if (i != 0)
				nestedProperty.append(".");
			nestedProperty.append(fn);			value = PropertyUtils.getProperty(obj, nestedProperty.toString());			if (value == null)
			{
				propertyDescriptor = PropertyUtils.getPropertyDescriptor(obj, nestedProperty.toString());
				propertyType = propertyDescriptor.getPropertyType();
				newInstance = propertyType.newInstance();
				PropertyUtils.setProperty(obj, nestedProperty.toString(), newInstance);
			}
		}
	}