设计模式--生成器模式

概述

　　将复杂对象的构建与表示分离，使得同样的构建过程可以创建不同的表示。

 

适用场景

　　1）构建一个复杂对象，该复杂对象内部往往有许多部件（域）待初始化；

　　2）通过不同的生成器，就可生成相应的复杂对象；

 

结构

　　

　　1）Product：即产品类。该类很复杂，它包含的域待初始化；

　　2）Builder：抽象Builder类。它需要指定Product对象中各部件的生成方法：buildPart()；

　　3）ConcreteBuilder：Builder类的一个实现。它包含一个待初始化的Product对象，通过对其组件进行初始化，并提供一个成型对象的方法；

　　4）Director：建造者。它包含一个抽象Builder对象，通过不同的Builder实现类，可生成不同的Product对象；在此过程中，也可选择性初始化部分组件，很灵活。

 

实例：

　　Product有2个组件：component1和component2; Builder有2个实现类，生成含有不同组件组合的Product。

Product:

 1 package org.wgx.pattern.builder;

 2 

 3 public class Product {

 4     private String name = "";

 5     private String component1 = "";

 6     private String component2 = "";

 7     

 8     public Product(String name) {

 9         this.name = name;

10     }

11     

12     public void setName(String name) {

13         this.name = name;

14     }

15     

16     public void setComponent1(String c1) {

17         this.component1 = c1;

18     }

19     

20     public void setComponent2(String c2) {

21         this.component2 = c2;

22     }

23     

24     public String toString() {

25         String result = "This is Product: " + name + ", component1 is " + component1 + ", component2 is " + component2 + "\r\n";

26         return result;

27     }

28 }

 

Builder：

1 package org.wgx.pattern.builder;

2 

3 public interface Builder {

4     public void buildComponent1();

5     public void buildComponent2();

6     public Product getProduct();

7 }

 

ConcreteBuilderOne：

 1 package org.wgx.pattern.builder;

 2 

 3 public class ConcreteBuilderOne implements Builder {

 4     

 5     private Product product;

 6     

 7     public ConcreteBuilderOne() {

 8         product = new Product("first product");

 9     }

10     

11     @Override

12     public void buildComponent1() {

13         // TODO Auto-generated method stub

14         this.product.setComponent1("1a");

15     }

16 

17     @Override

18     public void buildComponent2() {

19         // TODO Auto-generated method stub

20         this.product.setComponent2("2a");

21     }

22 

23     @Override

24     public Product getProduct() {

25         // TODO Auto-generated method stub

26         return this.product;

27     }

28 

29 }

 

ConcreteBuilderTwo：

 1 package org.wgx.pattern.builder;

 2 

 3 public class ConcreteBuilderTwo implements Builder {

 4 

 5     private Product product;

 6     

 7     public ConcreteBuilderTwo() {

 8         product = new Product("second product");

 9     }

10         

11     @Override

12     public void buildComponent1() {

13         // TODO Auto-generated method stub

14         this.product.setComponent1("1b");

15     }

16 

17     @Override

18     public void buildComponent2() {

19         // TODO Auto-generated method stub

20         this.product.setComponent2("2b");

21     }

22 

23     @Override

24     public Product getProduct() {

25         // TODO Auto-generated method stub

26         return this.product;

27     }

28 

29 }

 

Director：

 1 package org.wgx.pattern.builder;

 2 

 3 public class Director {

 4     private Builder builder;

 5     

 6     public Director(Builder builder) {

 7         this.builder = builder;

 8     }

 9     

10     public Product constructProduct() {

11         builder.buildComponent1();

12         builder.buildComponent2();

13         return builder.getProduct();

14     }

15     

16 }

 

Client：

 1 package org.wgx.pattern.builder;

 2 

 3 public class Client {

 4 

 5     /**

 6      * @param args

 7      */

 8     public static void main(String[] args) {

 9         // TODO Auto-generated method stub

10         Builder builder1 = new ConcreteBuilderOne();

11         Director director1 = new Director(builder1);

12         System.out.println(director1.constructProduct());

13             

14         Builder builder2 = new ConcreteBuilderTwo();

15         Director director2 = new Director(builder2);

16         System.out.println(director2.constructProduct());

17     }

18 

19 }

 

结果：

This is Product: first product, component1 is 1a, component2 is 2a

This is Product: second product, component1 is 1b, component2 is 2b