Visitor Pattern - Customers Report - Java Sourcecode

Main.java - The Main class is the client object. It has a reference tot the Object structure. In our case the objects Structure is the Customers objects

package com.oodesign.designpatterns.behavioral.visitor.impl;
package com.oodesign.designpatterns.behavioral.visitor.customers;

public class Main {

	/**
	 * @param args
	 */
	public static void main(String[] args) {
		// TODO Auto-generated method stub

		Customer c = new Customer("customer1");
		c.addOrder(new Order(".order1", "..item1"));
		c.addOrder(new Order(".order2", "..item1"));
		c.addOrder(new Order(".order3", "..item1"));
		
		Customer c2 = new Customer("customer2");
		Order o = new Order(".order_a");
		o.addItem(new Item("..item_a1"));
		o.addItem(new Item("..item_a2"));
		o.addItem(new Item("..item_a3"));
		c2.addOrder(o);
		c2.addOrder(new Order(".order_b", "..item_b1"));
		
		
		CustomerGroup customers = new CustomerGroup();
		customers.addCustomer(c);
		customers.addCustomer(c2);
		
		GeneralReport visitor = new GeneralReport(); 
		
		customers.accept(visitor);
		
		visitor.displayResults();
	}
}

IVisitor and IVisitable interfaces

package com.oodesign.designpatterns.behavioral.visitor.customers;

public interface IVisitable {
	  public void accept(IVisitor visitor);
}

package com.oodesign.designpatterns.behavioral.visitor.customers;

public interface IVisitor {
	   public void visit(Customer customer);
	   public void visit(Order order);
	   public void visit(Item item); 
}

GeneralReport is a visitor class and implements the IVisitor interface. Other Visitors (other reports or other types of visitors) can be added by implementing the IVisitor interface

package com.oodesign.designpatterns.behavioral.visitor.customers;

public class GeneralReport implements IVisitor{

	private int customersNo;
	private int ordersNo;
	private int itemsNo;

	public void visit(Customer customer)
	{
		System.out.println(customer.getName());
		customersNo ++;
	}
	public void visit(Order order)
	{
		System.out.println(order.getName());
		ordersNo++;
	}
	public void visit(Item item)
	{
		System.out.println(item.getName());
		itemsNo++;
	}

	public void displayResults()
	{
		System.out.println("Nr of customers:" + customersNo);
		System.out.println("Nr of orders:   " + ordersNo);
		System.out.println("Nr of itemss:   " + itemsNo);
	}
}

CustomerGroup, Customer, Order and Item are all visitable classes. A CustomerGroup represents a group of customers, each Customer can have one or more orders and each order can have one ore more Items.

package com.oodesign.designpatterns.behavioral.visitor.customers;

import java.util.ArrayList;
import java.util.Iterator;

public class CustomerGroup {
	
	private ArrayList customers = new ArrayList();

	public void accept(IVisitor visitor)
	{
		for (Iterator it=customers.iterator(); it.hasNext();)
		{
			((Customer)it.next()).accept(visitor);
		}		
	}

	public void addCustomer(Customer customer)
	{
		customers.add(customer);
	}	
	
}

package com.oodesign.designpatterns.behavioral.visitor.customers;

import java.util.ArrayList;
import java.util.Iterator;

public class Customer implements IVisitable{
	
	private String name;
	
	private ArrayList orders = new ArrayList();
	
	public void accept(IVisitor visitor)
	{
		visitor.visit(this);

		for (Iterator it=orders.iterator(); it.hasNext();)
		{
			((IVisitable)it.next()).accept(visitor);
		}		
	}


	public String getName() {
		return name;
	}


	public void setName(String name) {
		this.name = name;
	}
	
	public void addOrder(Order order)
	{
		orders.add(order);
	}
	
	
	public Customer(String name)
	{
		this.name = name;
	}
}

package com.oodesign.designpatterns.behavioral.visitor.customers;

import java.util.ArrayList;
import java.util.Iterator;

public class Order implements IVisitable {

	private String name;
	
	private ArrayList items = new ArrayList();
	
	public Order(String name)
	{
		this.name = name;
	}
	
	public Order(String name, String itemName)
	{
		this.name = name;
		this.addItem(new Item(itemName));
	}	
	
	public String getName() {
		return name;
	}

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

	public void accept(IVisitor visitor)
	{
		visitor.visit(this);
		
		for (Iterator it=items.iterator(); it.hasNext();)
		{
			((Item)it.next()).accept(visitor);
		}
	}
	
	
	public void addItem(Item item)
	{
		items.add(item);
	}
}

package com.oodesign.designpatterns.behavioral.visitor.customers;

public class Item implements IVisitable{
	
	private String name;
	
	public void accept(IVisitor visitor)
	{
		visitor.visit(this);
	}

	
	public Item(String name)
	{
		this.name = name;
	}
	
	public String getName() {
		return name;
	}

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