37 lines
1.5 KiB
Markdown
37 lines
1.5 KiB
Markdown
---
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layout: pattern
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title: Chain of responsibility
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folder: chain
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permalink: /patterns/chain/
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pumlid: 9SR13SCm20NGLTe1OkxTXX0KKzd4Wa-pVYlrdTxJN4OTMZ4U7LZv8Wg-ssdejLTgoELGHvDhaesw6HpqvWzlXwQTlYq6D3nfSlv2qjcS5F9VgvXjrHnV
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categories: Behavioral
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tags:
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- Java
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- Gang Of Four
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- Difficulty-Intermediate
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---
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## Intent
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Avoid coupling the sender of a request to its receiver by giving
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more than one object a chance to handle the request. Chain the receiving
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objects and pass the request along the chain until an object handles it.
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## Applicability
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Use Chain of Responsibility when
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* more than one object may handle a request, and the handler isn't known a priori. The handler should be ascertained automatically
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* you want to issue a request to one of several objects without specifying the receiver explicitly
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* the set of objects that can handle a request should be specified dynamically
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## Real world examples
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* [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)
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* [Apache Commons Chain](https://commons.apache.org/proper/commons-chain/index.html)
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* [javax.servlet.Filter#doFilter()](http://docs.oracle.com/javaee/7/api/javax/servlet/Filter.html#doFilter-javax.servlet.ServletRequest-javax.servlet.ServletResponse-javax.servlet.FilterChain-)
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## Credits
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* [Design Patterns: Elements of Reusable Object-Oriented Software](http://www.amazon.com/Design-Patterns-Elements-Reusable-Object-Oriented/dp/0201633612)
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