Java设计模式—— 建造者模式（Builder Pattern）

r囧r小猫 2022-05-10 12:48 248阅读 0赞

**建造者模式**：使用多个简单的对象一步一步构建成一个复杂的对象。

**建造者模式****UML类图如下：**

![70][]

从UML类图可以看出，建造者模式包含4个元素：

**抽象建造者（Builder）：**一个抽象接口，规范了产品对象的各个组成成分的建造。

**具体建造者（ConcreteBuilder）：**与应用程序紧密相关的一些类，它们在应用程序调用下创建产品的实例。

**导演者（Director）：**调用具体建造者角色来创建产品对象。

**产品（Product）：**一般是一个较为复杂的对象。

**具体代码：**

**1.抽象建造者类**

package com.szcatic.builder;
    
    public interface Builder {
    	
    	public void buildWheel();
        public void buildSkeleton();
        public void buildEngine();
    
        Product buildProduct();
    }

**2.****具体建造者类**

package com.szcatic.builder;
    
    public class ConcreteBuilder implements Builder {
    	
    	private Product product;
    
    	public ConcreteBuilder() {
    		this.product = new Product();
    	}
    
    	@Override
    	public void buildWheel() {
    		product.setWheel("轮子");
    	}
    
    	@Override
    	public void buildSkeleton() {
    		product.setSkeleton("架构");
    	}
    
    	@Override
    	public void buildEngine() {
    		product.setEngine("发动机");
    	}
    
    	@Override
    	public Product buildProduct() {
    		return product;
    	}
    	
    }

**3.导演者类**

package com.szcatic.builder;
    
    public class Director {
    
    	private Builder builder;
    	
    	public Director(Builder builder) {
    		this.builder = builder;
    	}
    
    	public Builder getBuilder() {
    		return builder;
    	}
    
    	public void setBuilder(Builder builder) {
    		this.builder = builder;
    	}
    
    	public Product buildProduct() {
    		builder.buildEngine();
    		builder.buildSkeleton();
    		builder.buildWheel();
    		return builder.buildProduct();
    	}
    }

**4.产品类**

package com.szcatic.builder;
    
    public class Product {
    	
    	private String wheel;
        private String skeleton;
        private String engine;
        
    	public String getWheel() {
    		return wheel;
    	}
    
    	public void setWheel(String wheel) {
    		this.wheel = wheel;
    	}
    
    	public String getSkeleton() {
    		return skeleton;
    	}
    
    	public void setSkeleton(String skeleton) {
    		this.skeleton = skeleton;
    	}
    
    	public String getEngine() {
    		return engine;
    	}
    
    	public void setEngine(String engine) {
    		this.engine = engine;
    	}
    
    	@Override
    	public String toString() {
    		return "Product [wheel=" + wheel + ", skeleton=" + skeleton + ", engine=" + engine + "]";
    	}
    	
    }

**5.测试类**

package com.szcatic.builder.test;
    
    import org.junit.jupiter.api.Test;
    
    import com.szcatic.builder.ConcreteBuilder;
    import com.szcatic.builder.Director;
    
    public class BuilderTest {
    	
    	@Test
    	void testBuildProduct() {
    		System.out.println(new Director(new ConcreteBuilder()).buildProduct());
    	}
    }

**运行结果：**

Product [wheel=轮子, skeleton=架构, engine=发动机]

**总结**

**优点：**

1、建造者独立，易扩展。

2、便于控制细节风险。

**缺点：**

1、产品必须有共同点，范围有限制。

2、如内部变化复杂，会有很多的建造类。

**构造器模式的另一种应用场景**

package com.hegret.builder;
    
    import java.io.Serializable;
    
    public class User implements Serializable {
    
    	private static final long serialVersionUID = 1L;
    
    	private String id;
    	private String name;
    	private String password;
    	private String eamil;
    	private String phone;
    
    	public String getId() {
    		return id;
    	}
    
    	public String getName() {
    		return name;
    	}
    
    	public String getPassword() {
    		return password;
    	}
    
    	public String getEamil() {
    		return eamil;
    	}
    
    	public String getPhone() {
    		return phone;
    	}
    
    	private User(Builder builder) {
    		this.id = builder.id;
    		this.name = builder.name;
    		this.password = builder.password;
    		this.eamil = builder.eamil;
    		this.phone = builder.phone;
    	}
    
    	@Override
    	public String toString() {
    		return "User [id=" + id + ", name=" + name + ", password=" + password + ", eamil=" + eamil + ", phone=" + phone
    				+ "]";
    	}
    
    	public static class Builder {
    		private String id;
    		private String name;
    		private String password;
    		private String eamil;
    		private String phone;
    
    		public Builder id(String id) {
    			this.id = id;
    			return this;
    		}
    
    		public Builder name(String name) {
    			this.name = name;
    			return this;
    		}
    
    		public Builder password(String password) {
    			this.password = password;
    			return this;
    		}
    
    		public Builder eamil(String eamil) {
    			this.eamil = eamil;
    			return this;
    		}
    
    		public Builder phone(String phone) {
    			this.phone = phone;
    			return this;
    		}
    
    		public User build() {
    			return new User(this);
    		}
    
    	}
    
    }

[70]: /images/20220505/51e7d42148174e93b1da3fe7f6536f30.png