java-design-patterns/intercepting-filter/README.md

---
layout: pattern
title: Intercepting Filter
folder: intercepting-filter
permalink: /patterns/intercepting-filter/
categories: Behavioral
language: en
tags:
 - Decoupling
---

## Intent
Provide pluggable filters to conduct necessary pre-processing and
post-processing to requests from a client to a target

## Class diagram 
![alt text](./etc/intercepting-filter.png "Intercepting Filter")

## Applicability
Use the Intercepting Filter pattern when

* a system uses pre-processing or post-processing requests
* a system should do the authentication/ authorization/ logging or tracking of request and then pass the requests to corresponding handlers 
* you want a modular approach to configuring pre-processing and post-processing schemes

## Tutorials

* [Introduction to Intercepting Filter Pattern in Java](https://www.baeldung.com/intercepting-filter-pattern-in-java)

## Real world examples

* [javax.servlet.FilterChain](https://tomcat.apache.org/tomcat-8.0-doc/servletapi/javax/servlet/FilterChain.html) and [javax.servlet.Filter](https://tomcat.apache.org/tomcat-8.0-doc/servletapi/javax/servlet/Filter.html)
* [Struts 2 - Interceptors](https://struts.apache.org/core-developers/interceptors.html)

## Credits

* [TutorialsPoint - Intercepting Filter](http://www.tutorialspoint.com/design_pattern/intercepting_filter_pattern.htm)
Work towards #56: Splitting up the README I did the job and splitted up the readme, hopefully everything was splitted correctly... 2015-08-13 23:54:40 +02:00			`---`
			`layout: pattern`
			`title: Intercepting Filter`
			`folder: intercepting-filter`
Work towards #56: Add permalink to every pattern This makes cleaner URLs thanks to jekyll 2015-08-15 18:03:05 +02:00			`permalink: /patterns/intercepting-filter/`
Work on #213 - properly categorize all patterns - remove pattern list from readme - minor fixes to readme - removed "introduction" because its not a pattern and an error i committed some time ago 2015-08-20 21:40:07 +02:00			`categories: Behavioral`
fix: Fixed pages showing up in wrong language (#1752) * Fix languages * Missed change for version number * Add language field for presentation * Revert change in README for double buffer Co-authored-by: Jackie Nim <=> 2021-05-19 10:49:05 -06:00			`language: en`
Categorize and tag all patterns #213 2015-12-28 15:52:44 +02:00			`tags:`
https://github.com/iluwatar/java-design-patterns-web/issues/8 Update pattern categories and tags 2019-12-13 21:09:28 +02:00			`- Decoupling`
Work towards #56: Splitting up the README I did the job and splitted up the readme, hopefully everything was splitted correctly... 2015-08-13 23:54:40 +02:00			`---`

Use headings instead of bold text in index.md #238 2016-01-03 21:14:30 +01:00			`## Intent`
			`Provide pluggable filters to conduct necessary pre-processing and`
Work towards #56: Splitting up the README I did the job and splitted up the readme, hopefully everything was splitted correctly... 2015-08-13 23:54:40 +02:00			`post-processing to requests from a client to a target`
Update Readme.md (#815) Added a tutorial link for intercepting filter design pattern 2018-11-04 23:42:04 +05:30
#1113 Link uml-reverse-mapper created class diagrams to readme, where needed 2019-12-07 20:01:13 +02:00			`## Class diagram`
			`![alt text](./etc/intercepting-filter.png "Intercepting Filter")`
Update Readme.md (#815) Added a tutorial link for intercepting filter design pattern 2018-11-04 23:42:04 +05:30
Use headings instead of bold text in index.md #238 2016-01-03 21:14:30 +01:00			`## Applicability`
			`Use the Intercepting Filter pattern when`
Work towards #56: Splitting up the README I did the job and splitted up the readme, hopefully everything was splitted correctly... 2015-08-13 23:54:40 +02:00
			`* a system uses pre-processing or post-processing requests`
			`* a system should do the authentication/ authorization/ logging or tracking of request and then pass the requests to corresponding handlers`
Work towards #56: Add permalink to every pattern This makes cleaner URLs thanks to jekyll 2015-08-15 18:03:05 +02:00			`* you want a modular approach to configuring pre-processing and post-processing schemes`
Work on #226, moved pattern specific credits to respective pattern pages in website 2015-09-03 18:17:07 +05:30
Update Readme.md (#815) Added a tutorial link for intercepting filter design pattern 2018-11-04 23:42:04 +05:30			`## Tutorials`
https://github.com/iluwatar/java-design-patterns-web/issues/8 Update pattern categories and tags 2019-12-13 21:09:28 +02:00
Update Readme.md (#815) Added a tutorial link for intercepting filter design pattern 2018-11-04 23:42:04 +05:30			`* [Introduction to Intercepting Filter Pattern in Java](https://www.baeldung.com/intercepting-filter-pattern-in-java)`

Use headings instead of bold text in index.md #238 2016-01-03 21:14:30 +01:00			`## Real world examples`
Work on #226, moved POSA reference and some J2EE design pattern references 2015-09-24 12:23:02 +05:30
#463 Added javax.servlet.Filter to real world examples of intercepting filter 2016-07-17 21:24:12 +02:00			`* [javax.servlet.FilterChain](https://tomcat.apache.org/tomcat-8.0-doc/servletapi/javax/servlet/FilterChain.html) and [javax.servlet.Filter](https://tomcat.apache.org/tomcat-8.0-doc/servletapi/javax/servlet/Filter.html)`
Fix broken links #915 (#921) 2019-09-07 23:48:13 +05:30			`* [Struts 2 - Interceptors](https://struts.apache.org/core-developers/interceptors.html)`
Work on #226, moved POSA reference and some J2EE design pattern references 2015-09-24 12:23:02 +05:30
Use headings instead of bold text in index.md #238 2016-01-03 21:14:30 +01:00			`## Credits`
Work on #226, moved pattern specific credits to respective pattern pages in website 2015-09-03 18:17:07 +05:30
			`* [TutorialsPoint - Intercepting Filter](http://www.tutorialspoint.com/design_pattern/intercepting_filter_pattern.htm)`