Work on Proxy blog post

Author: iluwatar

_posts/2016-12-13-controlling-access-with-proxy-pattern.md

@@ -12,35 +12,52 @@ One of the most useful and versatile design patterns is the classic Proxy.
 
 ## Proxy concept
 
-Basically it wraps an object and acts as a proxy between calls to the object. At first thought it might not sound so useful but this simple concept is a great solution to many problems.
+Basically it wraps an object and acts as a proxy between the calls to the object. At first thought it might not sound so useful but this simple concept is a great solution to many problems.
+
+## Types of proxies
+
+Protection proxy limits access to the object. Protection proxies can also be used to implement more fine grained access control.
+
+Another type is virtual proxy. Virtual proxies are used when an object is expensive to instantiate. We let the proxy manage the lifetime of the object, namely when the instance creation is needed and when it can be reused.
+
+Cache proxy can be used to cache expensive calls to the object improving performance.
+
+Remote proxies are used in distributed object communication. Invoking a local object method causes execution on the remote object.
+
+Smart proxies are used to implement reference counting and log calls to the object.
 
 ## Proxy example
 
-To elaborate let's think of a simple example. In a fantasy land far away inhabited by creatures from hobbits to dragons the mystic profession of wizard also exists. Wizards are known from their great magic but this power comes with a price. To upkeep and gain spell power the wizards must spend their time studying spellbooks and practising their spells. The best place in the neighborhood to study is the famous Ivory Tower built by the archmage Ivorious and it has become very popular among the wizards. However, to keep his tower tidy and not too crowded Ivorious decided to limit the amount of wizards that are allowed to enter simultaneously. He cast a protection spell on the tower that allows only the three first wizards to enter.
+To elaborate how Proxy design pattern works in practise let's think of a simple example. In a fantasy land far away inhabited by creatures from hobbits to dragons the mystic profession of wizard also exists. Wizards are known from their great magic but this power comes with a price. To upkeep and gain spell power the wizards must spend their time studying spellbooks and practising their spells. The best place in the neighborhood to study is the famous Ivory Tower built by the archmage Ivorious and it has become very popular among the wizards. However, to keep his tower tidy and not too crowded Ivorious decided to limit the amount of wizards that are allowed to enter the tower simultaneously. He cast a protection spell on the tower that allows only the three first wizards to enter.
 
 ![Proxy class diagram]({{ site.baseurl }}/assets/proxy-class-diagram.png)
 
-The class diagram shows the structure used to implement the Proxy pattern. WizardTower is the interface for all the towers and IvoryTower implements it. The plain IvoryTower allows everyone to enter but Ivorius has specifically cast a protection spell on it to limit the number of simultaneous visitors. The protection spell WizardTowerProxy also implements WizardTower but then it wraps IvoryTower. Now everyone wanting to access IvoryTower needs to go through WizardTowerProxy.
+The class diagram shows the structure used to implement the Proxy pattern. `WizardTower` is the interface for all the towers and `IvoryTower` implements it. The plain `IvoryTower` allows everyone to enter but Ivorius has specifically cast a protection spell on it to limit the number of simultaneous visitors. The protection spell enhanced `IvoryTower` is called `WizardTowerProxy`. It implements `WizardTower` and wraps `IvoryTower`. Now everyone wanting to access `IvoryTower` needs to go through the `WizardTowerProxy`.
 
 <script src="http://gist-it.appspot.com/http://github.com/iluwatar/java-design-patterns/raw/master/proxy/src/main/java/com/iluwatar/proxy/WizardTower.java?slice=27:"></script>
 
-<script src="http://gist-it.appspot.com/http://github.com/iluwatar/java-design-patterns/raw/master/proxy/src/main/java/com/iluwatar/proxy/IvoryTower.java?slice=32:"></script>
+`WizardTower` is the interface for all towers. It contains one simple method for entering the tower.
 
-<script src="http://gist-it.appspot.com/http://github.com/iluwatar/java-design-patterns/raw/master/proxy/src/main/java/com/iluwatar/proxy/Wizard.java?slice=29:"></script>
-
-<script src="http://gist-it.appspot.com/http://github.com/iluwatar/java-design-patterns/raw/master/proxy/src/main/java/com/iluwatar/proxy/WizardTowerProxy.java?slice=32:"></script>
+<script src="http://gist-it.appspot.com/http://github.com/iluwatar/java-design-patterns/raw/master/proxy/src/main/java/com/iluwatar/proxy/IvoryTower.java?slice=32:"></script>
 
-<script src="http://gist-it.appspot.com/http://github.com/iluwatar/java-design-patterns/raw/master/proxy/src/main/java/com/iluwatar/proxy/App.java?slice=40:"></script>
+`IvoryTower` is a simple implementation of `WizardTower`. It prints the entering wizard's name.
 
-## Types of proxies
+<script src="http://gist-it.appspot.com/http://github.com/iluwatar/java-design-patterns/raw/master/proxy/src/main/java/com/iluwatar/proxy/Wizard.java?slice=29:"></script>
 
-What we have seen in the previous tutorial is an example of protection proxy that limits access to the object. Protection proxies can also be used to implement more fine grained access control.
+`Wizard` is a simple immutable object with name.
 
-Another type is virtual proxy. Virtual proxies are used when an object is expensive to instantiate. We let the proxy manage the lifetime of the object, namely when the instance creation is needed and when it can be reused. 
+<script src="http://gist-it.appspot.com/http://github.com/iluwatar/java-design-patterns/raw/master/proxy/src/main/java/com/iluwatar/proxy/WizardTowerProxy.java?slice=32:"></script>
 
-Cache proxy can be used to cache expensive calls to the object improving performance.
+`WizardTowerProxy` is the proxy class that wraps any kind of `WizardTower` while implementing its interface. It keeps count how many wizards have entered the wrapped `WizardTower` and when the number reaches three it refuses to let any more wizards in.
 
-Remote proxies are used in distributed object communication. Invoking a local object method causes execution on the remote object.
+<script src="http://gist-it.appspot.com/http://github.com/iluwatar/java-design-patterns/raw/master/proxy/src/main/java/com/iluwatar/proxy/App.java?slice=40:"></script>
 
-Smart proxies are used to implement reference counting and log calls to the object.
+Running the application produces the following output.
 
+```
+22:01:56.571 [main] INFO com.iluwatar.proxy.IvoryTower - Red wizard enters the tower.
+22:01:56.576 [main] INFO com.iluwatar.proxy.IvoryTower - White wizard enters the tower.
+22:01:56.576 [main] INFO com.iluwatar.proxy.IvoryTower - Black wizard enters the tower.
+22:01:56.576 [main] INFO com.iluwatar.proxy.WizardTowerProxy - Green wizard is not allowed to enter!
+22:01:56.576 [main] INFO com.iluwatar.proxy.WizardTowerProxy - Brown wizard is not allowed to enter!
+```