提交 a1da1e49 编写于 作者: I Ilkka Seppälä

Cleanup factory

上级 9d21dff8
......@@ -15,35 +15,31 @@ tags:
## Intent
Providing a static method encapsulated in a class called factory, in order to hide the implementation logic and makes client code focus on usage rather then initialization new objects.
Providing a static method encapsulated in a class called factory, in order to hide the
implementation logic and makes client code focus on usage rather then initialization new objects.
## Explanation
Real world example
> Lets say we have a web application connected to SQLServer, but now we want to switch to Oracle. To do so without modifying existing source code, we need to implements Simple Factory pattern, in which a static method can be invoked to create connection to a given database.
> Lets say we have a web application connected to SQLServer, but now we want to switch to Oracle. To
> do so without modifying existing source code, we need to implements Simple Factory pattern, in
> which a static method can be invoked to create connection to a given database.
Wikipedia says
> Factory is an object for creating other objects – formally a factory is a function or method that returns objects of a varying prototype or class.
> Factory is an object for creating other objects – formally a factory is a function or method that
> returns objects of a varying prototype or class.
**Programmatic Example**
We have an interface 'Car' and tow implementations 'Ford' and 'Ferrari'.
We have an interface `Car` and two implementations `Ford` and `Ferrari`.
```java
/**
* Car interface.
*/
public interface Car {
public String getDescription();
String getDescription();
}
/**
* Ford implementation.
*/
public class Ford implements Car {
static final String DESCRIPTION = "This is Ford.";
......@@ -54,9 +50,6 @@ public class Ford implements Car {
}
}
/**
* Ferrari implementation.
*/
public class Ferrari implements Car {
static final String DESCRIPTION = "This is Ferrari.";
......@@ -68,14 +61,11 @@ public class Ferrari implements Car {
}
```
Enumeration above represents types of cars that we support (Ford and Ferrari).
Enumeration above represents types of cars that we support (`Ford` and `Ferrari`).
```java
public enum CarType {
/**
* Enumeration for different types of cars.
*/
FORD(Ford::new),
FERRARI(Ferrari::new);
......@@ -90,17 +80,12 @@ public enum CarType {
}
}
```
Then we have the static method 'getCar' to create car objects encapsulated in the factory class 'CarSimpleFactory'.
Then we have the static method `getCar` to create car objects encapsulated in the factory class
`CarSimpleFactory`.
```java
/**
* Factory of cars.
*/
public class CarsFactory {
/**
* Factory method takes as parameter a car type and initiate the appropriate class.
*/
public static Car getCar(CarType type) {
return type.getConstructor().get();
}
......@@ -122,17 +107,21 @@ Program output:
This is Ford.
This Ferrari.
```
## Class Diagram
![alt text](./etc/factory.urm.png "Factory pattern class diagram")
## Applicability
Use the Simple Factory pattern when you only care about the creation of a object, not how to create and manage it.
## Pros
Use the Simple Factory pattern when you only care about the creation of a object, not how to create
and manage it.
Pros
* Allows keeping all objects creation in one place and avoid of spreading 'new' key value across codebase.
* Allows to writs loosely coupled code. Some of its main advantages include better testability, easy-to-understand code, swappable components, scalability and isolated features.
## Cons
Cons
* The code becomes more complicated than it should be.
## Related patterns
......@@ -140,5 +129,3 @@ Use the Simple Factory pattern when you only care about the creation of a object
[Factory Method](https://java-design-patterns.com/patterns/factory-method/)
[Factory Kit](https://java-design-patterns.com/patterns/factory-kit/)
[Abstract Factory](https://java-design-patterns.com/patterns/abstract-factory/)
......@@ -5,6 +5,6 @@ package com.iluwatar.factory;
*/
public interface Car {
public String getDescription();
String getDescription();
}
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