创建型模式：建造者

骑猪看日落 2023-02-20 10:42 14阅读 0赞

建造者（Builder）模式也被称为生成器模式，创建型模式是主要是为了解决对象的创建的方式，相较于单态则是为了保证创建的对象的唯一性问题，建造者模式是为了解决复杂对象的创建，尤其是子对象的构建过程存在顺序和逻辑关系的时候。

# 模式场景与说明 #

比如对象由多个复杂的子对象组成的情况，多个对象组成的方式一般较为稳定，但是子对象的创建过程可能会发生变化，根据OCP原则，可以考虑对子对象的创建过程进行封装。

# 实现方式 #

一个通用创建型模式的使用可能会有如下部分组成：

<table> 
 <thead> 
  <tr> 
   <th>组成部分</th> 
   <th>类型</th> 
   <th>作用</th> 
  </tr> 
 </thead> 
 <tbody> 
  <tr> 
   <td>Product</td> 
   <td>类</td> 
   <td>创建的内容</td> 
  </tr> 
  <tr> 
   <td>Builder</td> 
   <td>接口</td> 
   <td>包含返回Product的build或者composite方法</td> 
  </tr> 
  <tr> 
   <td>ConcreteBuilder</td> 
   <td>具体建造类</td> 
   <td>实现了Builder接口的具体建造类，此类在加载时会创建一个Product对象</td> 
  </tr> 
  <tr> 
   <td>Director</td> 
   <td>调配类</td> 
   <td>一般此类的构建函数包含Builder类型的参数，通过此类提供统一的调配，包括顺序和逻辑，简单场景下可以不需要此类的存在</td> 
  </tr> 
 </tbody> 
</table>

# 示例概要 #

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2xpdW1pYW9jbg_size_16_color_FFFFFF_t_70]

# 代码示例 #

// Product
    class Computer { 
        private String cpu;
        private String memory;
        private String graphics;
        private String motherboard;
    
        public void setCpu(String cpu) { 
            this.cpu = cpu;
        }
    
        public void setMemory(String memory) { 
            this.memory = memory;
        }
    
        public void setGraphics(String graphics) { 
            this.graphics = graphics;
        }
    
        public void setMotherboard(String motherboard) { 
            this.motherboard = motherboard;
        }
    
        @Override
        public String toString(){ 
            return "Computer information: \n"
                    + "CPU: " + this.cpu + "\n"
                    + "Memory: " + this.memory + "\n"
                    + "Graphics: " + this.graphics + "\n"
                    + "Motherboard: " + this.motherboard;
        }
    }
    
    interface Builder { 
        void buildMotherboard(String motherboard);
        void buildGraphics(String graphics);
        void buildCpu(String cpu);
        void buildMemory(String memory);
        Computer build();
    }
    
    class ConcreteBuilder implements Builder { 
        private Computer computer = new Computer();
    
        @Override
        public void buildMotherboard(String motherboard){ 
            this.computer.setMotherboard(motherboard);
        }
        @Override
        public void buildGraphics(String graphics){ 
            this.computer.setGraphics(graphics);
        }
        @Override
        public void buildCpu(String cpu) { 
            this.computer.setCpu(cpu);
        }
        @Override
        public void buildMemory(String memory){ 
            this.computer.setMemory(memory);
        }
        @Override
        public Computer build(){ 
            return this.computer;
        }
    }
    
    class Director { 
        private Builder builder = null;
        Director(Builder builder) {  this.builder = builder; }
        Computer buildComputer(String motherboard, String graphics, String cpu,String memory) { 
            this.builder.buildMotherboard(motherboard);
            this.builder.buildGraphics(graphics);
            this.builder.buildCpu(cpu);
            this.builder.buildMemory(memory);
    
            return this.builder.build();
        }
    }
    
    public class BuilderTest { 
        public static void main(String[] args) { 
            Builder builder = new ConcreteBuilder();
            Director director = new Director(builder);
    
            Computer computer =  director.buildComputer("820-00xxx", "Intel Iris Pro 1536 MB","2.5 GHz Quad-Core Intel Core i7","16 GB 1600 MHz DDR3");
            System.out.print(computer);
        }
    }

执行结果为：

Computer information: 
    CPU: 2.5 GHz Quad-Core Intel Core i7
    Memory: 16 GB 1600 MHz DDR3
    Graphics: Intel Iris Pro 1536 MB
    Motherboard: 820-00xxx

但是需要注意此模式解决的问题和Factory不同，因此它是在具体建造类的加载期间就生成了Product的实例，可结合如下示例代码进行进一步的思考

Builder builder = new ConcreteBuilder();
            Director director = new Director(builder);
    
            Computer computer =  director.buildComputer("820-00xxx", "Intel Iris Pro 1536 MB","2.5 GHz Quad-Core Intel Core i7","16 GB 1600 MHz DDR3");
            System.out.println(computer);
    
            Computer computer2 =  director.buildComputer("830-00xxx", "Intel Iris Pro 3032 MB","2.5 GHz Quad-Core Intel Core i7","32 GB 1600 MHz DDR3");
            System.out.println(computer2);
            System.out.println(computer);

执行结果如下所示

Computer information: 
    CPU: 2.5 GHz Quad-Core Intel Core i7
    Memory: 16 GB 1600 MHz DDR3
    Graphics: Intel Iris Pro 1536 MB
    Motherboard: 820-00xxx
    Computer information: 
    CPU: 2.5 GHz Quad-Core Intel Core i7
    Memory: 32 GB 1600 MHz DDR3
    Graphics: Intel Iris Pro 3032 MB
    Motherboard: 830-00xxx
    Computer information: 
    CPU: 2.5 GHz Quad-Core Intel Core i7
    Memory: 32 GB 1600 MHz DDR3
    Graphics: Intel Iris Pro 3032 MB
    Motherboard: 830-00xxx

# 其他设计模式 #

*  [https://liumiaocn.blog.csdn.net/article/details/106954154][https_liumiaocn.blog.csdn.net_article_details_106954154]

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[https_liumiaocn.blog.csdn.net_article_details_106954154]: https://liumiaocn.blog.csdn.net/article/details/106954154