Question

I noticed that BeanUtils.copyProperties(dest, src) has a strange side effect. All null Integers (probably Long, Date etc. too) convert to 0 in both objects: source (sic!) and destination. Version: commons-beanutils-1.7.0

javadoc:

Copy property values from the origin bean to the destination bean for
all cases where the property names are the same.

For example:

class User {
   Integer age = null;
   // getters & setters
}
...
User userDest = new User();
User userSrc = new User();
BeanUtils.copyProperties(userDest, userSrc);
System.out.println(userDest.getAge()); // 0
System.out.println(userSrc.getAge()); // 0

It can be very buggy that source object is actually modified. What is the best solution to make “real” copy of object with null value.

Answer 1

Ok I’ve found this post

There is however a big difference between these two classes which I
came across while using these classes: BeanUtils does an automatic
type conversion and PropertyUtils does not.

For example: with BeanUtils you can set a double valued property by
providing a String. BeanUtils will check the type of the property and
convert the String into a double. With PropertyUtils you always have
to provide a value object of the same type as the property, so in this
example a double.

Automatic conversion is not necessary in this case, so better choice is PropertyUtils class