Apache BeanUtils behavioral conflict while copying List items from different classes

Question

I am developing an application that copy data of one class to another class.

I am trying to test getter-setter method works fine or not. To improve test coverage I am making some class and methods that will use podamfactory to fill up data inside given class's members.

Then I am copying data of that object to other object using apache BeanUtils.

Then I am asserting both objects to check that both have same data or not !

The problem I am facing that: I have create 3 classes:

1. Starter.java [have main method to run application]
2. ChildClass.java [have only 1 member i.e. Collection of String and it's getter method and add method to add data inside that member]
3. ParentClass.java [inside this class ChildClass's instance have been created and instantiated and related getter and setter method. Also have hashcode and equals method]

Code:

public class Starter {

    static final PodamFactory factory = new PodamFactoryImpl();

    public static void main(String[] args) throws Exception {
        System.out.println("Start");
        testClasses(ParentClass.class);
        System.out.println("End");
    }

    public static void testClasses(final Class<?> klass) throws Exception {
        final Object source = factory.manufacturePojo(klass);
        final Object destination = klass.newInstance();
        BeanUtils.copyProperties(destination, source);
        Assert.assertEquals(source, destination);
        Assert.assertNotEquals(source, new Object());
        Assert.assertEquals(source.hashCode(), destination.hashCode());
    }
}

In Main method I am passing ParentClass to check it's getter setter. testClasses method do the main work of copy and assertion.

When I am debugging I found that after copying properties of class, child class's instance have list and that have 5 members. In both object there's 5 members in List element.

But When I am passing ChildClass in Main then try to debug I am getting 5 element in source and in destination class it have 0 element after copying properties.

So I don't understand this behavior of BeanUtils, what need to do If I want same work when I am passing ChildClass in Main ?

When I am passing ParentClass it's have different behavior and when I am passing ChildClass it have different behavior in Copying properties.

I have created GitHub Repository to show my code. You can access and check code of my application.

I have created simple gradle project for dependency management.

If anyone knows more about it then let me know.

Thanks.

Answer 1

BeanUtils follows strict definition of properties in Java Bean sense, i.e. each property must have getter with name get + name of a field and setter with name set + name of a field. While your child class contains no setFields() setter. In other words you could change it like this

public class ChildClass {

    private final List<String> fields = new ArrayList<>();

    public List<String> getFields() {
        return this.fields;
    }

    public List<String> setFields(List<String> fields) {
        this.fields = fields;
    }
}

or alternatively

public class ChildClass {

    private final List<String> fields = new ArrayList<>();

    public List<String> getFields() {
        return this.fields;
    }

    public List<String> setFields(List<String> fields) {
        this.fields.clear();
        this.fields.addAll(fields);
    }
}