layout:pattern

title:Chain of responsibility

folder:chain

permalink:/patterns/chain/

folder:chain-of-responsibility

permalink:/patterns/chain-of-responsibility/

categories:Behavioral

language:en

tags:

-Gang of Four

Avoid coupling the sender of a request to its receiver by giving more than one object a chance to

handle the request. Chain the receiving objects and pass the request along the chain until an object

handles it.

Realworld example

Real-world example

In plain words

**Programmatic Example**

Translating our example with the orcs from above. First we have the`Request` class:

Translating our example with the orcs from above. First, we have the`Request` class:

publicclassRequest {

}

Thenthe request handler hierarchy

Next, we showthe request handler hierarchy.

Then we have theOrc Kingwhogives the orders and forms the chain

ThOrc King gives the orders and forms the chain.

publicclassOrcKing {

}

var king=newOrcKing();

king.makeRequest(newRequest(RequestType.DEFEND_CASTLE,"defend castle"));// Orc commander handling request "defend castle"

king.makeRequest(newRequest(RequestType.TORTURE_PRISONER,"torture prisoner"));// Orc officer handling request "torture prisoner"

king.makeRequest(newRequest(RequestType.COLLECT_TAX,"collect tax"));// Orc soldier handling request "collect tax"

king.makeRequest(newRequest(RequestType.DEFEND_CASTLE,"defend castle"));

king.makeRequest(newRequest(RequestType.TORTURE_PRISONER,"torture prisoner"));

king.makeRequest(newRequest(RequestType.COLLECT_TAX,"collect tax"));

The console output.

![alt text](./etc/chain.urm.png"Chain of Responsibility class diagram")

![alt text](./etc/chain-of-responsibility.urm.png"Chain of Responsibility class diagram")

* You want to issue a request to one of several objects without specifying the receiver explicitly.

* The set of objects that can handle a request should be specified dynamically.

*[java.util.logging.Logger#log()](http://docs.oracle.com/javase/8/docs/api/java/util/logging/Logger.html#log%28java.util.logging.Level,%20java.lang.String%29)

*[Apache Commons Chain](https://commons.apache.org/proper/commons-chain/index.html)

<artifactId>java-design-patterns</artifactId>

<version>1.25.0-SNAPSHOT</version>

</parent>

<artifactId>chain</artifactId>

<artifactId>chain-of-responsibility</artifactId>

<dependencies>

<dependency>

<groupId>org.junit.jupiter</groupId>

<module>facade</module>

<module>flyweight</module>

<module>proxy</module>

<module>chain</module>

<module>chain-of-responsibility</module>

<module>command</module>

<module>interpreter</module>

<module>iterator</module>