建造者模式

最新推荐文章于 2025-04-11 20:42:48 发布

洋洋2018

最新推荐文章于 2025-04-11 20:42:48 发布

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分类专栏：设计模式

本文链接：https://blog.youkuaiyun.com/a20023930/article/details/79171088

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问：建造者模式要解决什么问题。什么时候使用此模式？

比如我们组装一台电脑主机。必要的硬件有CPU 、硬盘、电源、内存、主板。非必要的有独立网卡、散热器。独立显卡等等。

构造函数创建对象

主机

package com.lyy.pattern.builder;

/**
 * 电脑主机
 * @author ThinkPad
 *
 */
public class ComputerMain {


	//cpu 	必要
	private String cpu;
	
	//内存	 必要
	private String memory;
	
	//电源	 必要
	private String power;
	
	//硬盘 	必要
	private String disk;
	
	//主板       必要
	private String mainboard;
	
	//独立网卡 		非必要
	private String independentNetworkCar; 
	
	//散热风扇 	 	非必要
	private String coolingFan;

	/**
	 * 最基本构造函数
	 * @param cpu
	 * @param memory
	 * @param power
	 * @param disk
	 */
	public ComputerMain(String cpu, String memory, String power, String disk, String mainboard) {
		this(cpu,memory,power,disk, mainboard, null, null);
	}
	
	/**
	 * 增加一个网卡的构造函数
	 * @param cpu
	 * @param memory
	 * @param power
	 * @param disk
	 * @param independentNetworkCar
	 */
	public ComputerMain(String cpu, String memory, String power, String disk, 
				String mainboard,String independentNetworkCar) {
		this(cpu,memory,power,disk,mainboard,independentNetworkCar, null);
	}
	
	/**
	 * 增加一个网卡和散热器的造函数
	 * @param cpu
	 * @param memory
	 * @param power
	 * @param disk
	 * @param independentNetworkCar
	 * @param coolingFan
	 */
	public ComputerMain(String cpu, String memory, String power, String disk, 
				String mainboard, String independentNetworkCar, String coolingFan) {
		this.cpu = cpu;
		this.memory = memory;
		this.power = power;
		this.disk = disk;
		this.mainboard = mainboard;
		this.independentNetworkCar = independentNetworkCar;
		this.coolingFan = coolingFan;
}
	
	
	

	@Override
	public String toString() {
		return "ComputerMain [cpu=" + cpu + ", memory=" + memory + ", power=" + power + ", disk=" + disk
				+ ", mainboard=" + mainboard + ", independentNetworkCar=" + independentNetworkCar + ", coolingFan="
				+ coolingFan + "]";
	}

		
	
}

main:

package com.lyy.pattern.builder;

public class Main {
	
	
	public static void main(String[] args) {
		//基本电脑主机
		ComputerMain baseComputerMain = new ComputerMain("酷睿 i7", "金斯顿 ", "长城", "西部数据" ,"华硕");
		System.out.println(baseComputerMain);
		
		//有独立网上的电脑
		ComputerMain networkCarComputerMain = new ComputerMain("酷睿 i7", "金斯顿 ", "长城", "西部数据", "华硕", "inter");
		System.out.println(networkCarComputerMain);
		
		//有独立网卡和散热风扇的电脑
		ComputerMain advaComputerMain = new ComputerMain("酷睿 i7", "金斯顿 ", "长城", "西部数据","华硕" ,"inter","酷冷至尊");
		System.out.println(advaComputerMain);
		
		//有散热风扇的电脑
		ComputerMain fanComputerMain = new ComputerMain("酷睿 i7", "金斯顿 ", "长城", "西部数据","华硕" ,null,"酷冷至尊");
		System.out.println(fanComputerMain);
	}
}

上面我们用构造函数来创建对象有几个问题：

1.如果我们非必要的硬件增加独立显卡、固态硬盘、等；那么创建对象很麻烦。

2.如上面：想创建一个带散热器且不带独立网卡的主机时，我们就要在构造函数独立网卡对应位置填null

javaBean方式创建对象

用这种方式可解决上面第2个问题。

		//1.先创建一个基本主机
		ComputerMain baseComputerMain = new ComputerMain("酷睿 i7", "金斯顿 ", "长城", "西部数据" ,"华硕");
		//2.加个风扇
		baseComputerMain.setCoolingFan("酷冷至尊");

其他非必要硬件如上也可达到目的。

也有一个问题:

1.阻止了对象被创建完成后的不可变。比如说我们创建完主机，并开机运行，这时肯定是不能再换硬件或增加硬件。（对象创建完不想让改变状态）。但我们可随时调用set方法的。

解决方法：

package com.lyy.pattern.builder;

/**
 * 电脑主机
 * @author ThinkPad
 *
 */
public class ComputerMain2 {


	//cpu 	必要
	private String cpu;
	
	//内存	 必要
	private String memory;
	
	//电源	 必要
	private String power;
	
	//硬盘 	必要
	private String disk;
	
	//主板       必要
	private String mainboard;
	
	//独立网卡 		非必要
	private String independentNetworkCar; 
	
	//散热风扇 	 	非必要
	private String coolingFan;
	
	
	/**
	 * 构造函数
	 * @param builder
	 */
	public ComputerMain2(Builder builder) {
		this.coolingFan = builder.cpu;
		this.cpu = builder.cpu;
		this.disk = builder.disk;
		this.independentNetworkCar = builder.independentNetworkCar;
		this.mainboard = builder.mainboard;
		this.memory = builder.mainboard;
		this.power = builder.power;
	}
	

	/**
	 * 建造器
	 * @author ThinkPad
	 *
	 */
	public static class Builder{
		
		//cpu 	必要
		private String cpu;
		
		//内存	 必要
		private String memory;
		
		//电源	 必要
		private String power;
		
		//硬盘 	必要
		private String disk;
		
		//主板       必要
		private String mainboard;
		
		//独立网卡 		非必要
		private String independentNetworkCar; 
		
		//散热风扇 	 	非必要
		private String coolingFan;
		
		public Builder(String cpu, String memory, String power, String disk, String mainboard) {
			this.cpu = cpu;
			this.memory = memory;
			this.power = power;
			this.disk = disk;
			this.mainboard = mainboard;
		}


		public Builder setIndependentNetworkCar(String independentNetworkCar) {
			this.independentNetworkCar = independentNetworkCar;
			return this;
		}


		public Builder setCoolingFan(String coolingFan) {
			this.coolingFan = coolingFan;
			return this;
		}
		
		/**
		 * 创建主机对象
		 * @return
		 */
		public ComputerMain2 build() {
			return new ComputerMain2(this);
		}
		
		
	}

	@Override
	public String toString() {
		return "ComputerMain [cpu=" + cpu + ", memory=" + memory + ", power=" + power + ", disk=" + disk
				+ ", mainboard=" + mainboard + ", independentNetworkCar=" + independentNetworkCar + ", coolingFan="
				+ coolingFan + "]";
	}

	
	
		
	
}

		ComputerMain2 computerMain2 = new ComputerMain2.Builder("酷睿 i7", "金斯顿 ", "长城", "西部数据" ,"华硕")
				.setCoolingFan("酷冷至尊").build();
		System.out.println(computerMain2);

现在有这个一个场景：富士康有两个生产线。dell c20 、lenovo P50。既然是生产线那么生产本系列的电脑任何配置都是一样的。所以就没必要每次都set不同的硬件。但是还是以上的需求，开机运行不能修改硬件（创建的对象不能被修改某些参数，不提供set方法）。

上代码：

package com.lyy.pattern.builder;

/**
 * 富士康
 * @author ThinkPad
 *
 */
public class Fushikang {

	public Computer createComputer(Builder builder) {
		//builder.setCpu()   builder.setMemory()...各各部分的创建这里省略了
		return builder.createComputer();
	}
}

package com.lyy.pattern.builder;

/**
 * 建造器接口
 * @author ThinkPad
 *
 */
public interface Builder {

	public String getCpu();
	
	public String getMemory();
	
	public String getPower();
	
	public String getDisk();
	
	public String getMainboard();
	
	public String getIndependentNetworkCar();
	
	public String getCoolingFan();
	
	public Computer createComputer();

}

package com.lyy.pattern.builder;


public class Computer {

	//cpu 	必要
	private String cpu;
	
	//内存	 必要
	private String memory;
	
	//电源	 必要
	private String power;
	
	//硬盘 	必要
	private String disk;
	
	//主板       必要
	private String mainboard;
	
	//独立网卡 		非必要
	private String independentNetworkCar; 
	
	//散热风扇 	 	非必要
	private String coolingFan;
	
	/**
	 * 构造器
	 * @param builder
	 */
	public Computer(Builder builder) {
		this.coolingFan = builder.getCoolingFan();
		this.cpu = builder.getCpu();
		this.disk = builder.getDisk();
		this.independentNetworkCar = builder.getIndependentNetworkCar();
		this.mainboard = builder.getMainboard();
		this.memory = builder.getMemory();
		this.power = builder.getPower();
	}

	@Override
	public String toString() {
		return "Computer [cpu=" + cpu + ", memory=" + memory + ", power=" + power + ", disk=" + disk + ", mainboard="
				+ mainboard + ", independentNetworkCar=" + independentNetworkCar + ", coolingFan=" + coolingFan + "]";
	}
	
	
	
}

package com.lyy.pattern.builder;

/**
 *戴尔c20生产线
 * @author ThinkPad
 *
 */
public class ProductionLineDellBuilder implements Builder {

	public String getCpu() {
		// TODO Auto-generated method stub
		return "I5-5820";
	}

	public String getMemory() {
		// TODO Auto-generated method stub
		return "威刚";
	}

	public String getPower() {
		// TODO Auto-generated method stub
		return "戴尔";
	}

	public String getDisk() {
		// TODO Auto-generated method stub
		return "戴尔";
	}

	public String getMainboard() {
		// TODO Auto-generated method stub
		return "戴尔";
	}

	public String getIndependentNetworkCar() {
		// TODO Auto-generated method stub
		return "戴尔";
	}

	public String getCoolingFan() {
		// TODO Auto-generated method stub
		return "戴尔";
	}

	public Computer createComputer() {
		
		return new Computer(this);
	}

}

package com.lyy.pattern.builder;

/**
 * 联想 P50生产线
 * @author ThinkPad
 *
 */
public class ProductionLineLenovoBuilder implements Builder {

	public String getCpu() {
		// TODO Auto-generated method stub
		return "AMD X8500";
	}

	public String getMemory() {
		// TODO Auto-generated method stub
		return "威刚";
	}

	public String getPower() {
		// TODO Auto-generated method stub
		return "联想";
	}

	public String getDisk() {
		// TODO Auto-generated method stub
		return "联想";
	}

	public String getMainboard() {
		// TODO Auto-generated method stub
		return "联想";
	}

	public String getIndependentNetworkCar() {
		// TODO Auto-generated method stub
		return "联想";
	}

	public String getCoolingFan() {
		// TODO Auto-generated method stub
		return "联想";
	}

	public Computer createComputer() {
		
		return new Computer(this);
	}

}

main

		Fushikang fushikang = new Fushikang();
		Computer dellComputer = fushikang.createComputer(new ProductionLineDellBuilder());
		Computer lenovoComputer = fushikang.createComputer(new ProductionLineLenovoBuilder());
		System.out.println(dellComputer);
		System.out.println(lenovoComputer);

打印

Computer [cpu=I5-5820, memory=威刚, power=戴尔, disk=戴尔, mainboard=戴尔, independentNetworkCar=戴尔, coolingFan=戴尔]
Computer [cpu=AMD X8500, memory=威刚, power=联想, disk=联想, mainboard=联想, independentNetworkCar=联想, coolingFan=联想]

总结（个人结论，不一定对！~~）：

创建一个多属性或复杂对象、并且创建完的实例某些参数不想被修改（不提供set方法）时可考虑建造者模式。

最后给张类图：