I have an object A that contains for example:
class A{
String elem1;
Int elem2;
...get and set
}
and i have a class B that contains same element and name of field:
class B{
String elem1;
Int elem2;
...get and set
}
i want copy class A value into class B value without modify the class. How can solve? thanks.
There's no "clean" way to do this; you will need to manually copy every entry.
A a = ...;
B copy = new B();
copy.elem1 = a.elem1;
copy.elem2 = a.elem2;
Alternatively, you could use reflection, but it's performance costly and somewhat unclear, and will fail if there is any inconsistencies between the classes' field definitions.
A a = ...;
B copy = new B();
for (Field field : a.getClass().getDeclaredFields()) {
Field copyField = copy.getClass().getDeclaredField(field.getName());
field.setAccessible(true);
copyField.setAccessible(true);
if (!field.getType().isPrimitive()) {
Object value = field.get(a);
field.set(copy, value);
} else if (field.getType().equals(int.class)) {
int value = field.getInt(a);
field.setInt(copy, value);
} else if { ... } // and so forth
}
try this simple way
firstObj.setElem1 (secObj.getElem1());
You can create a third class which would act as a factory, with a method taking an instance of A as a parameter, and returning an instance of B.
public final class MyFactory
{
public static B createBFromA (A instance)
{
B newInstance = new B ();
newInstance.setXXX (instance.getXXX ());
return newInstance;
}
}
The advantage of using an external factory is to isolate the code that creates your B instances from the rest of your code.
Better late than never but here is the answer I have found. You can use GSON to serialize the Object to String and then deserialize to the class B. Here is the tested example:
package JSON.test.obj_copy;
public class TestClassA {
private String field1 = "pikachu";
private Integer field2 = 1;
private List<String> field3 = new ArrayList<String>(Arrays.asList("A", "B", "C"));
private Obj field4 = new Obj();
@Override
public String toString(){
return new StringBuilder("field1: " + field1 + "\n")
.append("field2: " + field2 + "\n")
.append("field3: " + field3 + "\n")
.append("field4: " + field4)
.toString();
}
}
public class TestClassB {
private String field1;
private Integer field2;
private List<String> field3;
private Obj field4;
@Override
public String toString(){
return new StringBuilder("field1: " + field1 + "\n")
.append("field2: " + field2 + "\n")
.append("field3: " + field3 + "\n")
.append("field4: " + field4)
.toString();
}
}
public class Obj {
}
public class MainObjCopy {
public static void main(String[] args){
TestClassA a = new TestClassA();
TestClassB b;
Gson g = new Gson();
String s1 = g.toJson(a);
b = g.fromJson(s1, TestClassB.class);
System.out.println(b);
}
}
Output:
field1: pikachu
field2: 1
field3: [A, B, C]
field4: JSON.test.obj_copy.Obj@22d8cfe0
