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docs: update proxy

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Ilkka Seppälä
2024-05-27 08:45:45 +03:00
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proxy/README.md
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@@ -14,7 +14,7 @@ tag:
## Also known as
Surrogate
* Surrogate
## Intent
@@ -24,7 +24,7 @@ Provide a surrogate or placeholder for another object to control access to it.
Real-world example
> Imagine a tower where the local wizards go to study their spells. The ivory tower can only be accessed through a proxy which ensures that only the first three wizards can enter. Here the proxy represents the functionality of the tower and adds access control to it.
> In a real-world scenario, consider a security guard at a gated community. The security guard acts as a proxy for the residents. When a visitor arrives, the guard checks the visitor's credentials and permissions before allowing them access to the community. If the visitor is authorized, the guard grants entry; if not, entry is denied. This ensures that only authorized individuals can access the community, much like a Proxy design pattern controls access to a specific object.
In plain words
@@ -36,13 +36,17 @@ Wikipedia says
**Programmatic Example**
Taking our wizard tower example from above. Firstly we have the `WizardTower` interface and the `IvoryTower` class.
Imagine a tower where the local wizards go to study their spells. The ivory tower can only be accessed through a proxy which ensures that only the first three wizards can enter. Here the proxy represents the functionality of the tower and adds access control to it.
First, we have the `WizardTower` interface and the `IvoryTower` class.
```java
public interface WizardTower {
void enter(Wizard wizard);
}
```
```java
@Slf4j
public class IvoryTower implements WizardTower {
public void enter(Wizard wizard) {
@@ -76,9 +80,7 @@ Then we have the `WizardTowerProxy` to add access control to `WizardTower`.
public class WizardTowerProxy implements WizardTower {
private static final int NUM_WIZARDS_ALLOWED = 3;
private int numWizards;
private final WizardTower tower;
public WizardTowerProxy(WizardTower tower) {
@@ -100,28 +102,27 @@ public class WizardTowerProxy implements WizardTower {
And here is the tower entering scenario.
```java
var proxy = new WizardTowerProxy(new IvoryTower());
proxy.enter(new Wizard("Red wizard"));
proxy.enter(new Wizard("White wizard"));
proxy.enter(new Wizard("Black wizard"));
proxy.enter(new Wizard("Green wizard"));
proxy.enter(new Wizard("Brown wizard"));
public static void main(String[] args) {
var proxy = new WizardTowerProxy(new IvoryTower());
proxy.enter(new Wizard("Red wizard"));
proxy.enter(new Wizard("White wizard"));
proxy.enter(new Wizard("Black wizard"));
proxy.enter(new Wizard("Green wizard"));
proxy.enter(new Wizard("Brown wizard"));
}
```
Program output:
```
Red wizard enters the tower.
White wizard enters the tower.
Black wizard enters the tower.
Green wizard is not allowed to enter!
Brown wizard is not allowed to enter!
08:42:06.183 [main] INFO com.iluwatar.proxy.IvoryTower -- Red wizard enters the tower.
08:42:06.186 [main] INFO com.iluwatar.proxy.IvoryTower -- White wizard enters the tower.
08:42:06.186 [main] INFO com.iluwatar.proxy.IvoryTower -- Black wizard enters the tower.
08:42:06.186 [main] INFO com.iluwatar.proxy.WizardTowerProxy -- Green wizard is not allowed to enter!
08:42:06.186 [main] INFO com.iluwatar.proxy.WizardTowerProxy -- Brown wizard is not allowed to enter!
```
## Class diagram
![Proxy](./etc/proxy.urm.png "Proxy pattern class diagram")
## Applicability
Proxy is applicable whenever there is a need for a more versatile or sophisticated reference to an object than a simple pointer. Here are several common situations in which the Proxy pattern is applicable. Typically, the proxy pattern is used to
@@ -165,6 +166,6 @@ Trade-offs:
## Credits
* [Design Patterns: Elements of Reusable Object-Oriented Software](https://www.amazon.com/gp/product/0201633612/ref=as_li_tl?ie=UTF8&camp=1789&creative=9325&creativeASIN=0201633612&linkCode=as2&tag=javadesignpat-20&linkId=675d49790ce11db99d90bde47f1aeb59)
* [Head First Design Patterns: A Brain-Friendly Guide](https://www.amazon.com/gp/product/0596007124/ref=as_li_tl?ie=UTF8&camp=1789&creative=9325&creativeASIN=0596007124&linkCode=as2&tag=javadesignpat-20&linkId=6b8b6eea86021af6c8e3cd3fc382cb5b)
* [Design Patterns: Elements of Reusable Object-Oriented Software](https://amzn.to/3w0pvKI)
* [Head First Design Patterns: Building Extensible and Maintainable Object-Oriented Software](https://amzn.to/49NGldq)
* [Java Design Patterns: A Hands-On Experience with Real-World Examples](https://amzn.to/3yhh525)