CODEWITHSUNDEEP
javavariablesfieldpojo
User111
User111

Reputation: 95

how to get fields from a pojo dynamically

Below is my POJO class which has 50 fields with setters and getters.

Class Employee{
int m1;
int m2;
int m3;
.
.
int m50;
//setters and getters

From my another class I need to get all these 50 fields to get their sum

Employee e1 =new Emploee();
int total = e1.getM1()+e2.getM2()+........e2.getM50();

Instead of doing this manually for 50 records is there any way to do it dynamically(by any loop).

Thanks

Upvotes: 3

Views: 12545

Answers (4)

Razib
Razib

Reputation: 11173

You may use java reflection. For simplicity I assume your Employee calss only contains int field. But you can use the similar rules used here for getting float, double or long value. Here is a complete code - 

import java.lang.reflect.Field;
import java.util.List;

class Employee{

    private int m=10;
    private int n=20;
    private int o=25;
    private int p=30;
    private int q=40;
}

public class EmployeeTest{

 public static void main(String[] args) throws NoSuchFieldException, IllegalAccessException{

        int sum = 0;
        Employee employee = new Employee();
        Field[] allFields = employee.getClass().getDeclaredFields();

        for (Field each : allFields) {

            if(each.getType().toString().equals("int")){

                Field field = employee.getClass().getDeclaredField(each.getName());
                field.setAccessible(true);

                Object value = field.get(employee);
                Integer i = (Integer) value;
                sum = sum+i;
            }

        }

        System.out.println("Sum :" +sum);
 }

}

Upvotes: 5

Srini
Srini

Reputation: 1646

I can't possibly imagine a real life scenario where you'd have 1000 fields in a class. Having said that, you can invoke all your getters reflectively. Use Introspector to accomplish this task:

int getEmployeeSum(Employee employee)
{    
    int sum = 0;
    for(PropertyDescriptor propertyDescriptor : Introspector.getBeanInfo(Employee.class).getPropertyDescriptors())
    {
        sum += propertyDescriptor.getReadMethod().invoke(employee);
    }

    return sum;
}

Upvotes: 4

Lrrr
Lrrr

Reputation: 4805

Yes, dont use 1000 fields! use an array with 1000 elements, then fill array[i-1] with mi your class would be something like:

Class Employee{
    int[] empArr = new int[1000];
}

then use could find sum like this:

int sum = 0;

for(int i = 0; i<1000 ; i++)
    sum+= e1.empArr[i]

Upvotes: 2

Matt C
Matt C

Reputation: 4555

Yes, instead of having a separate variable for each m1, m2, m3, ... you can put them in one array like so:

Class Employee {
    public int[] m = new int[1000];
}

Employee e1 = new Employee();
int total = 0;

for(int i = 0; i < e1.m.length; i++) {
    total += e1.m[i];
}

Upvotes: 1

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