Update readme

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Petrutiu Mihai
2016-07-12 13:32:58 +03:00
parent a63c77153f
commit 814e5a093c

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@@ -12,23 +12,28 @@ Hierarchical in nature
More than one object can handle a command
The handler is not known in advance
The handler should be determined automatically
Its wished that the request is addressed to a group of objects without explicitly specifying its receiver
It<EFBFBD>s wished that the request is addressed to a group of objects without explicitly specifying its receiver
The group of objects that may handle the command must be specified in a dynamic way.
Examples in real life:
-java.util.logging.Logger.#log()
-javax.servlet.Filter#doFilter()
-Spring Security Filter Chain
### c. Pitfalls:
### c. Actors
* Client - creates the chain, and uses it
* Handler - defines an interface for handling the requests, optional to set the succesor
* Concrete Handler - handles requests it is responsible for, may request the successor to process the request if needed
### d. Pitfalls:
Handling/Handler guarantee - you won't be sure that someone can process the request
Runtime configuration risk - the order matters/and it might be that the chain is not configured correctly
Chain length/performance issues - in theory you could see a chain that is too big, and it would be a bottleneck in performance
### d. Flavors:
### e. Flavors:
* Flavor 1: Execute first that matches the condition and exit -> Get one to process the request, or get the type of object
* Flavor 2: Execute all elements of chain until the condition does not match -> Execute all validators until one invalidates the request
* Flavor 3: Always execute all handlers
* Flavor 4: Instead of each handler, having a successor, you could have each handler have a list of successors, and have it's policy what handlers to execute
### e. Examples described:
### f. Examples described:
* Purchase example:
Starting class: PurchaseExample.CheckAuthority
Problem that we are trying to solve:
@@ -53,6 +58,7 @@ For Create user: verify if the authenticated user is authorised to create a new
* Both the menu options and the validations for the operations are done using chain of responssibility
2. Command pattern
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3. Iterator pattern
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