Shulou(Shulou.com)06/03 Report--

Factory Pattern of Design Patterns-Factory Method Pattern

Hello, everyone. Welcome to Dirty Bomb Company. Today, our company has received a new pizza project.

Source: KaigeJava (kaigejava)

Requirements:

Pizza items:

Easy to expand pizza varieties, easy to maintain, easy to expand during operation

Take a look at pizza design:

After analysis, the company found that pizza needs baking (bake), cutting (cut), packaging (box) and pizza raw materials preparation (prepare). Among them, the raw materials prepared are changed. Different pizza ingredients are different, but they all need to be baked, cut and packaged. Therefore, we do abstract raw material methods here, not concrete implementation. After analysis, the following class diagram is obtained:

The first design: using simple factory mode (can refer to the previous article of the company noodle shop project) found that it does not work. Why is that?

As pizza grows in popularity, many places are asking for JM. If JM's words, each place has to create a simple factory pattern, the same code, we have to create many copies, in the maintenance time, it is very troublesome.

Select the second design: the factory approach pattern.

Let's look at the project structure:

Description:

1: domain: is a specific pojo object. inherited from the PizzaAbstract class.

Among them, those that start with BeiJin are all Beijing chain stores. The ones that start with Shan Hai are all Shanghai chain stores.

2 and 3 are abstract classes for pizza and pizza orders

4: Order type of specific chain point. inherited from PiazzOrderAbstract class.

5: Test class

Let's look at two abstract classes first.

PizzaAbstract class:

PizzaOrderAbstract class:

Here's a greekpizza in Beijing:

Take a look at BeiJinOrderPizza:

Test Category:

View the results of the run:

From the above code demonstration, we can get the following:

Factory Method Pattern Design Scheme:

The instantiation function of pizza object in pizza project is abstracted into abstract method, and the function is realized in different JM stores.

Factory Method Mode:

Defines an abstract method for creating an object, and the subclass determines which class to instantiate. From this statement, we can see that the factory method pattern deferring instantiation (creation) of objects to subclasses.

Factory Method vs. Simple Factory:

Simple Factory Mode:

According to the class identifier, the factory object can be used to obtain the instance object of the specific class. Within the factory object, the instantiation of the class object is as follows:

Object instantiation is inside the factory object.

Factory Method Mode:

is to extract the creation of objects. It's a way of creating pizza, abstracting it into a concrete class.

Let's take a look at the pizza order object:

When specifically called:

PizzaOrderAbstract bjOder = new BeiJinOrderPizza(); Calls the concrete subclass.

The instantiation of objects is done in subclasses.

Contact KaigeJava (kaigejava)

Kaigejava.com-Kaigejava.com Personal blog can be private letter Kai Ge oh ~

Factory method pattern through an abstract factory class to create a factory, and then by the factory through a certain method to create a certain object, so that if there is a new product C does not need to modify the existing code as long as a new product from the subclass and factory subclass can it.

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