merging one object into another object

Question

I have two Objects of same type.I want to create a method which can merge the properties of two object and can return a single object.

For Example: Consider a class ABC having 4 fields

Class ABC{
String name;
String id;
String salary;
String status;
}

Suppose the first object is

ABC[name=ZEE,id=2,salary=null,status=1]

and the second object is

ABC[name=john,id=null,salary=12200,status=null]

I want to make a generic method which can merge these two objects and can give result output as:

ABC[name=ZEE,id=2,salary=12200,status=1]

The method Should take two parameters of Object type:

Object  mergeObject(Object Obj1, Object Obj2){
}

Note: It will take the first object property if both the objects have non-null value for that property.

How will you handle collisions? e.g. `Obj1` has a field and so does `Obj2`. Depending on that logic, just setup some accessor/mutator (getter/setter) methods for the class variables and in your `mergeObject` method, create a new object and set fields as you go by checking `Obj1` vs. `Obj2` — Avantol13, Jun 11 '15 at 13:26
Generic as "will work for all objects"? This is not going to be possible. Consider enums, for example. Even getting close will require some serious reflection stunts. — RealSkeptic, Jun 11 '15 at 13:27
And what have you done so far yourself? Besides writing up this question? You understand you don't just drop your requirements here; and other people do your work? — GhostCat, Jun 11 '15 at 13:27
Seriously, **what happened to** `john` as a name on collision? The second object's value was overridden.... is this intended behavior? — EpicPandaForce, Jun 11 '15 at 13:31
It will take the first object property if both the objects have non-null value for that property. — Deepak Kumar, Jun 11 '15 at 13:31

score 19 · Accepted Answer · edited May 23 '17 at 12:33

You're going to have to go the reflection route. I'm assuming you have a default constructor, otherwise the following won't work. Also, it needs two same types. It won't copy inherited fields, for that, you also need to add some code from here.

@SuppressWarnings("unchecked")
public static <T> T mergeObjects(T first, T second) throws IllegalAccessException, InstantiationException {
    Class<?> clazz = first.getClass();
    Field[] fields = clazz.getDeclaredFields();
    Object returnValue = clazz.newInstance();
    for (Field field : fields) {
        field.setAccessible(true);
        Object value1 = field.get(first);
        Object value2 = field.get(second);
        Object value = (value1 != null) ? value1 : value2;
        field.set(returnValue, value);
    }
    return (T) returnValue;
}

Here's an example

public static class ABC {
    private int id;
    private String name;
    private int[] numbers;

    public ABC() {
    }


    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public int[] getNumbers() {
        return numbers;
    }

    public void setNumbers(int[] numbers) {
        this.numbers = numbers;
    }
}

public static void main(String[] args) throws InstantiationException, IllegalAccessException {
    ABC abc = new ABC();
    abc.setId(1);
    abc.setName("Hello");
    int[] newnumbers = new int[5];
    for(int i = 0; i < newnumbers.length; i++) {
        newnumbers[i] = i;
    }
    abc.setNumbers(newnumbers);
    ABC abc2 = new ABC();
    abc2.setName("World");

    ABC abcFinal = mergeObjects(abc, abc2);
    System.out.println("Properties of ABC Final:");
    System.out.println("ID: " + abcFinal.getId());
    System.out.println("Name: " + abcFinal.getName());
    System.out.println("Numbers: " + Arrays.toString(abcFinal.getNumbers()));
}

Output:

Properties of ABC Final:
ID: 1
Name: Hello
Numbers: [0, 1, 2, 3, 4]

This is perfect I was writing program to give answer, but you have posted first @Epic :) Good Job — Vishal Zanzrukia, Jun 11 '15 at 14:04

score 4 · Answer 2 · edited Jun 11 '15 at 13:32

4

In case you want to create a new Object use:

public ABC mergeABC(ABC obj1, ABC obj2){
    ABC retVal = new ABC();
    retVal.name   = ((obj1.name   != null) ? obj1.name   : obj2.name   );
    retVal.id     = ((obj1.id     != null) ? obj1.id     : obj2.id     );
    retVal.salary = ((obj1.salary != null) ? obj1.salary : obj2.salary );
    retVal.status = ((obj1.status != null) ? obj1.status : obj2.status );
    return retVal;
}

If you want to "reuse" obj1 or obj2, simply use this as return value.

edited Jun 11 '15 at 13:32

EpicPandaForce

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answered Jun 11 '15 at 13:32

dosw

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This is the most sensible answer so far, however it does not answer the question. You should clearly start saying why what the OP wants is hard and bad, and then present this more sensible (and different) solution – Dici Jun 11 '15 at 13:35

Othya · Answer 3 · 2015-06-11T13:58:09.413

0

If you want to prioritize the values in Object 1 (in case both objects have values), then follow something like this..

private CustomObject mergeObject(CustomObject Obj1, CustomObject Obj2) {
    CustomObject tempObject = new CustomObject();
     If (Obj1.getName() == null) {
      tempObject.setName(Obj2.getName());
     } else {
         tempObject.setName(Obj1.getName());
     }
     return tempObject;
}

Iterate over the if statement for each parameter within the object.

edited Jun 11 '15 at 13:58

answered Jun 11 '15 at 13:31

Othya

390
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Is this a new language ? It seems pretty cool, unfortunately the qustion is for Java – Dici Jun 11 '15 at 13:32
I don't get it.. it's probably not the best solution but it does work - in java. Obviously "Object" would be a custom object, and not the word "object" – Othya Jun 11 '15 at 13:34
"obviously" if you just say `Object`, people will say it's a compile time error. – EpicPandaForce Jun 11 '15 at 13:36
@Dici EpicPandaForce I changed my answer... hopefully it's a bit better. – Othya Jun 11 '15 at 13:36
Oh yeah obviously, so don't use the name of the most famous class of Java to name another custom class – Dici Jun 11 '15 at 13:36
Sorry - I fixed my answer. – Othya Jun 11 '15 at 13:37
@Othya You are still missing several brackets and you are still using `Object` for one of your parameters. – Dici Jun 11 '15 at 13:47
@Dici thanks, I edited again. – Othya Jun 11 '15 at 13:59

score -2 · Answer 4 · edited Jun 11 '15 at 14:48

-2

If you want to do it generically, your only option is going to be reflection.

edited Jun 11 '15 at 14:48

EpicPandaForce

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answered Jun 11 '15 at 13:29

Karrde

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That's more suitable as a comment rather than an answer. – EpicPandaForce Jun 11 '15 at 13:52
'Use reflection' is a reasonable answer...not every answer has to be spoon fed code? – Karrde Jun 11 '15 at 13:54

merging one object into another object

4 Answers4