简介

        本文用示例介绍Java的建造者模式的用法。

有序的建造者模式

简介

​场景​

假设的场景：建一座房子。需要如下步骤：打地基、建墙体、铺电线、粉刷。这些步骤的顺序是不可颠倒的，而且任意一步不可缺少。

​所有的类​

Java设计模式--建造者模式--使用/详解/实例_java

代码

房屋产品

package org.example.builder.product;

public class House {
    private String base;
    private String wall;
    private String wire;
    private String paint;

    public String getBase() {
        return base;
    }

    public void setBase(String base) {
        this.base = base;
    }

    public String getWall() {
        return wall;
    }

    public void setWall(String wall) {
        this.wall = wall;
    }

    public String getWire() {
        return wire;
    }

    public void setWire(String wire) {
        this.wire = wire;
    }

    public String getPaint() {
        return paint;
    }

    public void setPaint(String paint) {
        this.paint = paint;
    }

    @Override
    public String toString() {
        return "House{" +
                "base='" + base + '\'' +
                ", wall='" + wall + '\'' +
                ", wire='" + wire + '\'' +
                ", paint='" + paint + '\'' +
                '}';
    }
}

建造者

​抽象类 ​

package org.example.builder.product;

public abstract class Builder {
    public abstract Builder buildBase(String base);

    public abstract Builder buildWall(String wall);

    public abstract Builder buildWire(String wire);

    public abstract Builder buildPaint(String paint);

    public abstract House build();
}

​实现类​

重点：在构造函数中，创建一个产品。

package org.example.builder.product;

public class Woker extends Builder {
    private House house;

    public Woker() {
        this.house = new House();
    }

    @Override
    public Builder buildBase(String base) {
        System.out.println("建造地基");
        house.setBase(base);
        return this;
    }

    @Override
    public Builder buildWall(String wall) {
        System.out.println("建造墙壁");
        house.setWall(wall);
        return this;
    }

    @Override
    public Builder buildWire(String wire) {
        System.out.println("铺设电线");
        house.setWire(wire);
        return this;
    }

    @Override
    public Builder buildPaint(String paint) {
        System.out.println("粉刷");
        house.setPaint(paint);
        return this;
    }

    @Override
    public House build() {
        return this.house;
    }
}

指挥者

​简介​

指挥者决定建造房子的顺序

指挥者决定具体每一步做什么样的建造。这样，可以造出简约、有大电流的电线、有隔音墙、地基为平房地基的平房，也可以造出其他配置的房子，比如：豪华粉刷、大电流、隔音墙、地基为高楼地基的高楼等。

​代码​

package org.example.builder;

import org.example.builder.product.Builder;
import org.example.builder.product.House;

public class Director {
    public static House build(Builder builder) {
        return builder
                .buildBase("平房地基")
                .buildWall("隔音墙")
                .buildWire("大电流的电线")
                .buildPaint("简约粉刷")
                .build();
    }
}

测试类

​简介​

指挥者（包工头）去指挥具体的工人去按照自己的步骤建造房子。

​代码​

package org.example.builder;

import org.example.builder.product.House;
import org.example.builder.product.Woker;

public class Consumer {
    public static void main(String[] args) {
        House build = Director.build(new Woker());
        System.out.println(build);
    }
}

​执行结果​

建造地基
建造墙壁
铺设电线
粉刷
House{base='平房地基', wall='隔音墙', wire='大电流的电线', paint='简约粉刷'}

无序的建造者模式

​简介​

​场景​

假设的场景：你去买一款手机，这款手机有多种可选的配置：颜色、运行内存、机身存储。

  • 如你果不指定，则给一个默认项，比如：黑色，6G，128G。
  • 如果你指定某些项，则给你你指定的配置，其他没指定的依然采用默认的配置。

​所有的类​

Java设计模式--建造者模式--使用/详解/实例_ide_02

​对比有序的建造者模式​

 无序，且每个字段有默认项，由用户来直接设置。

​代码​

​手机产品​

重点：提供静态的创建builder的方法；字段要设置默认值。

package org.example.builder.product;

public class Phone {
    private String color = "黑色（默认）";
    private String runningStorage = "6G（默认）";
    private String phoneStorage = "128G（默认）";

    public static DefaultBuilder builder() {
        return new DefaultBuilder();
    }

    public String getColor() {
        return color;
    }

    public void setColor(String color) {
        this.color = color;
    }

    public String getRunningStorage() {
        return runningStorage;
    }

    public void setRunningStorage(String runningStorage) {
        this.runningStorage = runningStorage;
    }

    public String getPhoneStorage() {
        return phoneStorage;
    }

    public void setPhoneStorage(String phoneStorage) {
        this.phoneStorage = phoneStorage;
    }

    @Override
    public String toString() {
        return "Phone{" +
                "color='" + color + '\'' +
                ", runningStorage='" + runningStorage + '\'' +
                ", phoneStorage='" + phoneStorage + '\'' +
                '}';
    }
}

​建造者​

​建造者抽象类​

package org.example.builder.product;

public abstract class Builder {
    public abstract Builder buildColor(String color);

    public abstract Builder buildRunningStorage(String runningStorage);

    public abstract Builder buildPhoneStorage(String phoneStorage);

    public abstract Phone build();
}

​建造者实现类​

重点：构造函数里边，要去构造一个产品。 

package org.example.builder.product;

public class DefaultBuilder extends Builder {
    private Phone phone;

    public DefaultBuilder() {
        this.phone = new Phone();
    }

    @Override
    public Builder buildColor(String color) {
        phone.setColor(color);
        return this;
    }

    @Override
    public Builder buildRunningStorage(String runningStorage) {
        phone.setRunningStorage(runningStorage);
        return this;
    }

    @Override
    public Builder buildPhoneStorage(String phoneStorage) {
        phone.setPhoneStorage(phoneStorage);
        return this;
    }

    @Override
    public Phone build() {
        return phone;
    }
}

​测试类​

package org.example.builder;

import org.example.builder.product.Phone;

public class Consumer {
    public static void main(String[] args) {
        Phone phone = Phone.builder()
                .buildColor("红色")
                .buildRunningStorage("8G")
                .build();
        System.out.println(phone);
    }
}

​执行结果​

Phone{color='红色', runningStorage='8G', phoneStorage='128G（默认）'}

其他网址

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