Chain of Responsibility
In object-oriented design, the chain-of-responsibility pattern is a design pattern consisting of a source of command objects and a series of processing objects.
Overview
- define a chain of receiver having a responsibility, handle a request or if it's not able to handle a request, forward it the next receiver on the chain.
- not need to be conscious of a role of controller like which object handle which request.
- user only throw a request to one object on the chain.
implementation
This is an application to judge your character by color you like.
Color.java is a Handler class.
Green.java is a receiver class.
Main.java is a sender class.
Color.java
public abstract class Color {
private Color next;
private ColorEnum color;
public Color(ColorEnum color) {
this.color = color;
}
public Color setNext(Color next) {
this.next = next;
return next;
}
public void selectColor (ColorEnum color) {
if (beAbleToJudge(color)) {
showCharacter(color);
} else if (next != null) {
next.selectColor(color);
} else {
System.out.println("The color you selected is invalid. Please select other color!");
}
}
protected boolean beAbleToJudge (ColorEnum color) {
if (this.color.equalWithColor(color)) {
return true;
} else {
return false;
}
}
protected abstract void showCharacter (ColorEnum color);
}
Green.java
public class Green extends Color {
public Green (ColorEnum color) {
super(color);
}
protected void showCharacter (ColorEnum color) {
System.out.println("You selected Green.");
System.out.println("Your character is below");
System.out.println("#1.conservative");
System.out.println("#2.judicious and delicate");
System.out.println("#3.talkative");
}
}
ColorEnum.java
public enum ColorEnum {
GREEN
, YELLOW
, PINK
, RED
, ORANGE
, BLACK
, BROWN
, GREY
, BLUE
, WHITE
, PURPLE;
public boolean equalWithColor (ColorEnum color) {
if (this.equals(color)) {
return true;
} else {
return false;
}
}
}
Person.java
public class Person {
private String name;
private ColorEnum color;
public Person (String name, ColorEnum color) {
this.name = name;
this.color = color;
}
public String getName() {
return name;
}
public ColorEnum getColor() {
return color;
}
}
Main.java
public class Main {
public static void main(String[] args) {
List<Person> list = new ArrayList<Person>();
setPerson(list);
Color green = new Green(ColorEnum.GREEN);
Color yellow = new Yellow(ColorEnum.YELLOW);
Color pink = new Pink(ColorEnum.PINK);
Color red = new Red(ColorEnum.RED);
Color orange = new Orange(ColorEnum.ORANGE);
Color black = new Black(ColorEnum.BLACK);
green.setNext(yellow).setNext(pink).setNext(red).setNext(orange).setNext(black);
for (Person person: list) {
System.out.println("Hi " + person.getName() + "!");
green.selectColor(person.getColor());
}
}
// each person select their favorite color
public static void setPerson(List<Person> list) {
list.add(new Person("satoshi", ColorEnum.ORANGE));
list.add(new Person("miwa", ColorEnum.RED));
list.add(new Person("taro", ColorEnum.GREEN));
list.add(new Person("hitoshi", ColorEnum.YELLOW));
list.add(new Person("eri", ColorEnum.BLACK));
list.add(new Person("richard", ColorEnum.BROWN));
list.add(new Person("rio", ColorEnum.PINK));
}
}
result.md
Hi satoshi!
You selected Orange.
Your character is below
#1.active
#2.like wide and shallow human relations
Hi miwa!
You selected Red.
Your character is below
#1.positive and very active
#2.your emotional ups and downs are erratic
Hi taro!
You selected Green.
Your character is below
#1.conservative
#2.judicious and delicate
#3.talkative
Hi hitoshi!
You selected Yellow.
Your character is below
#1.curious and a strong upward mobility
#2.thinking that hierarchical relationship is important
#3.getting bored easily
Hi eri!
You selected Black.
Your character is below
#1.sensitive
#2.tend not to like to follow someone
Hi richard!
The color you selected is invalid. Please select other color!
Hi rio!
You selected Pink.
Your character is below
#1.gentle and stable
#2.strong dependence