Design mode (8)-----Factory Method mode

Factory method Mode (Factory) definition

Defines an interface for creating objects, letting subclasses decide which class to instantiate. The factory method defers a class to its subclasses.

UML Class Diagram

Composition

1) Abstract Factory Role (Creator): This is the core of the factory method pattern, which is not related to the application. is the interface that the specific factory role must implement or the parent class that must inherit. In Java it is implemented by an abstract class or interface.

2) Specific factory role (Concretecreator): It contains code related to the specific business logic. Called by the application to create an object that corresponds to a specific product.

3) Abstract Product role: It is the parent of a specific product inheritance or an implemented interface. In Java, there are generally abstract classes or interfaces to implement.

4) Specific product roles (CONCRETEPRODUCT): The object created by the specific factory role is an instance of this role. Implemented in Java by a specific class.

Example

A BMW manufacturing plant that can manufacture various models of BMW.

 package   com.csdhsm.designpattem.factory ; /**   * @Title: Bmw.java * @Description: Creator All BMW inherits from the class *   @author  : Han * @date: June 20, 2016 PM 5:46:56  */ abstract  public  class   BMW { public   BMW () {}}  

 package   com.csdhsm.designpattem.factory ; /**   * @Title: Bmw320.java * @Description: Model 320 BMW *   @author  : Han * @date: June 20, 2016 PM 5:48:05  */ public  class  BMW320 extends   BMW { public   BMW320 () {System.out.println ( Manufacturing--"BMW320" 

 Package com.csdhsm.designpattem.factory; /**    * @Title:  bmw523.java    @author: Han    * @date:   June 20, 2016 PM 5:48:35     */public  classextends  BMW        {public  BMW523 () {        System.out.println ("Manufacturing--" BMW523 ");}    }

Abstract product

 Package com.csdhsm.designpattem.factory; /**    * @Title:  factorybmw.java    @author: Han    * @date:   June 20, 2016 5:49:24     */   Public Interface FACTORYBMW {    BMW createbmw ();}

Concreteproduct

 package   com.csdhsm.designpattem.factory ; /**   * @Title: Factorybmw320.java * @Description: Factory of BMW320 *   @author  : Han * @date: June 20, 2016 PM 5:50:29  */ public  class  FactoryBMW320 Span style= "color: #0000ff;" >implements   FACTORYBMW {@Override    BMW CREATEBMW () { return  new   BMW320 (); }}

 Package com.csdhsm.designpattem.factory; /**    * @Title:  factorybmw523.java    @author: Han    * @date:   June 20, 2016 PM 5 : 50:12    */public  classimplements  FACTORYBMW {    @Override      Public BMW createbmw () {        returnnew  BMW523 ();    }}

Client

 Package com.csdhsm.designpattem.factory;  Public class Solution {    publicstaticvoid  main (string[] args) {        new  FactoryBMW320 ();        FACBMW.CREATEBMW ();         New FactoryBMW523 ();        FACBMW.CREATEBMW ();    }}

Results

Disadvantages

The addition of factory methods has multiplied the number of objects.

Design mode (8)-----Factory Method mode