建造者模式

介绍

建造者模式是创建型模式之一，使用多个简单的对象创建一个复杂的对象，定义不同的构造类使得相同的构建过程可以创建不同的对象。同工厂模式不同，工厂模式重点关注的是对象的创建过程，建造者模式重点关注的是对象的组装过程。

模块

Builder：构造者接口
ConcreteBuilder：具体构造者，实现构造器接口，定义复杂对象的创建流程
Product：被创建的对象
Director：指导者，调用具体构造者创建对象的各个部分

在这里插入图片描述

场景

在需求开发中，当需要创建一个复杂对象时，需要对这个对象的各个子部件创建并组合。例如苹果电脑，我们不能自己组装电脑，而是在官网上下单，由专门的技术人员根据我们选择的配置进行组装。电脑里面的部件是固定数量的，但是各个部件的配置是不一样的。面临剧烈的需求变化，复杂对象的各个部件是会经常变化的，但是对象的各个结构是不变的

结构代码演示

接下来我们就以我手中 M1Pro 32G 1T 10核的MacBook Pro举例，嘿嘿。按照苹果官网有高中低三档配置，我使用高中低三个建造者进行电脑的各个组件的创建，然后让指导者进行组装

# 产品 macBook
public class MacBook {
    private String memory;
    private String slug;
    private String cpu;
    private String disk;

    // 省略get set
}
# 建造者接口
import com.hello.designPattern.BuilderPattern.model.MacBook;

public interface MacBookBuilder {

     MacBookBuilder buildMemory();
     MacBookBuilder buildSlug();
     MacBookBuilder buildCpu();
     MacBookBuilder buildDisk();


      MacBook build();
}
# 高中低 三个建造者
import com.hello.designPattern.BuilderPattern.interfaces.MacBookBuilder;
import com.hello.designPattern.BuilderPattern.model.MacBook;

public class HighMacBookBuilder implements MacBookBuilder {

    private MacBook macBook = new MacBook();
    
    @Override
    public MacBookBuilder buildMemory() {
        macBook.setMemory("安装32G运行内存");
        return this;
    }

    @Override
    public MacBookBuilder buildSlug() {
        macBook.setSlug("安装M1X芯片");
        return this;
    }

    @Override
    public MacBookBuilder buildCpu() {
        macBook.setCpu("安装10核中央处理器");
        return this;
    }

    @Override
    public MacBookBuilder buildDisk() {
        macBook.setDisk("安装1TB固态硬盘");
        return this;
    }

    public MacBook build(){
        return macBook;
    }
}

import com.hello.designPattern.BuilderPattern.interfaces.MacBookBuilder;
import com.hello.designPattern.BuilderPattern.model.MacBook;

public class MiddleMacBookBuilder implements MacBookBuilder {
    private MacBook macBook;

    @Override
    public MacBookBuilder buildMemory() {
        macBook.setMemory("安装16G运行内存");
        return this;
    }

    @Override
    public MacBookBuilder buildSlug() {
        macBook.setSlug("安装M1Pro芯片");
        return this;
    }

    @Override
    public MacBookBuilder buildCpu() {
        macBook.setCpu("安装10核中央处理器");
        return this;
    }

    @Override
    public MacBookBuilder buildDisk() {
        macBook.setDisk("安装1TB固态硬盘");
        return this;
    }

    public MacBook build(){
        return macBook;
    }
}

import com.hello.designPattern.BuilderPattern.interfaces.MacBookBuilder;
import com.hello.designPattern.BuilderPattern.model.MacBook;

public class LowMacBookBuilder implements MacBookBuilder {

    private MacBook macBook = new MacBook();

    @Override
    public MacBookBuilder buildMemory() {
        macBook.setMemory("安装16G运行内存");
        return this;
    }

    @Override
    public MacBookBuilder buildSlug() {
        macBook.setSlug("安装M1Pro芯片");
        return this;
    }

    @Override
    public MacBookBuilder buildCpu() {
        macBook.setCpu("安装10核中央处理器");
        return this;
    }

    @Override
    public MacBookBuilder buildDisk() {
        macBook.setDisk("安装512G固态硬盘");
        return this;
    }

    public MacBook build(){
        return macBook;
    }
}
# 指导者
import com.hello.designPattern.BuilderPattern.interfaces.MacBookBuilder;
import com.hello.designPattern.BuilderPattern.model.MacBook;

public class Director {
    private MacBookBuilder macBookBuilder;

    public Director(MacBookBuilder macBookBuilder) {
        this.macBookBuilder = macBookBuilder;
    }

    public MacBook construct(){
        return macBookBuilder.buildMemory().buildDisk().buildCpu().buildSlug().build();
    }
}

测试方法

package com.hello.designPattern.singletonPattern;

import com.hello.designPattern.BuilderPattern.builder.HighMacBookBuilder;
import com.hello.designPattern.BuilderPattern.director.Director;
import com.hello.designPattern.BuilderPattern.model.MacBook;
import org.junit.Test;

public class BuilderPatternTest {

    @Test
    public void builderPatternTest(){
        Director director = new Director(new HighMacBookBuilder());
        MacBook macBook = director.construct();
        System.out.println(macBook.toString());
    }
}