Contract field updates example 1

gistfile1.java

package com.evo.adm;

import com.opengrapes.common.widgets.util.Lists;
import org.junit.Test;

import java.util.List;

import static junit.framework.Assert.assertEquals;

/**
 * @author Mihail Lesikov ([email protected])
 */
public class TestContractUpdate {

  class Customer {

    private String name;

    public Customer(String name) {
      this.name = name;
    }

    public void updateFrom(Customer customer2) {
      for (Field field : customer2.getFields()) {
        field.applyUpdate(this);
      }
    }

    private Iterable<? extends Field> getFields() {
      return Lists.newArrayList(new CustomerNameField(this));
    }
  }

  class Contract {

    private String code;

    public int paymentDay;

    private Customer customer;

    public void updateFrom(Contract contract2) {
      for (Field field : contract2.getFields()) {
        field.applyUpdate(this);
      }
    }

    public List<Field<Contract>> getFields() {
      return Lists.newArrayList(new PaymentDayField(this), new CustomerField(this));
    }
  }


  private interface Field<T> {
    void applyUpdate(T t);
  }

  class PaymentDayField implements Field<Contract> {

    private Contract owner;

    PaymentDayField(Contract owner) {
      this.owner = owner;
    }

    public void applyUpdate(Contract contract) {
      contract.paymentDay = owner.paymentDay;
    }
  }



  class CustomerField implements Field<Contract> {

    private Contract owner;

    CustomerField(Contract owner) {
      this.owner = owner;
    }

    public void applyUpdate(Contract contract) {
      contract.customer.updateFrom(owner.customer);
    }
  }




  class CustomerNameField implements Field<Customer> {

    private Customer owner;

    CustomerNameField(Customer owner) {
      this.owner = owner;
    }

    public void applyUpdate(Customer customer) {
      customer.name = owner.name;
    }

  }


  @Test
  public void test() throws Exception {
    Contract contract = new Contract();
    contract.code = "1111";
    contract.paymentDay = 17;
    contract.customer = new Customer("lazo");


    Contract contract2 = new Contract();
    contract2.code = "2222";
    contract2.paymentDay = 7;
    contract2.customer = new Customer("mi6o");

    contract.updateFrom(contract2);


    assertEquals(7, contract.paymentDay);
    assertEquals("mi6o", contract.customer.name);

  }
}