Builder概述

Builder - 图1

玩具代码案例 - 汽车车间

抽象Builder角色

ICarBuilder

package online.javabook.gof.creational.patterns4.builder.car.builder.api;
import online.javabook.gof.creational.patterns4.builder.car.product.main.Car;
public interface ICarBuilder {
    public void buildFrame();
    public void buildEngine();
    public void buildWheel();
    public void buildNavigation();
    public void buildComputer();
    public Car getCar();
}

具体Builder角色

CityCarBuilder

package online.javabook.gof.creational.patterns4.builder.car.builder.impl;
import online.javabook.gof.creational.patterns4.builder.car.builder.api.ICarBuilder;
import online.javabook.gof.creational.patterns4.builder.car.product.part.Frame;
import online.javabook.gof.creational.patterns4.builder.car.product.part.*;
import online.javabook.gof.creational.patterns4.builder.car.product.main.Car;
import java.awt.*;
public class CityCarBuilder implements ICarBuilder {
    private Car car = new Car();
    @Override
    public void buildFrame() {
        car.setFrame(new Frame(Color.BLACK));
    }
    @Override
    public void buildEngine() {
        car.setEngine(new Engine("oil"));
    }
    @Override
    public void buildWheel() {
        car.setWheel(new Wheel(10));
    }
    @Override
    public void buildNavigation() {
        car.setNavigation(new Navigation("gps"));
    }
    @Override
    public void buildComputer() {
        car.setComputer(new Computer("android"));
    }
    @Override
    public Car getCar() {
        return car;
    }
}

SportCarBuilder

package online.javabook.gof.creational.patterns4.builder.car.builder.impl;
import online.javabook.gof.creational.patterns4.builder.car.builder.api.ICarBuilder;
import online.javabook.gof.creational.patterns4.builder.car.product.part.Frame;
import online.javabook.gof.creational.patterns4.builder.car.product.part.*;
import online.javabook.gof.creational.patterns4.builder.car.product.main.Car;
import java.awt.*;
public class SportCarBuilder implements ICarBuilder {
    private Car car = new Car();
    @Override
    public void buildFrame() {
        car.setFrame(new Frame(Color.CYAN));
    }
    @Override
    public void buildEngine() {
        car.setEngine(new Engine("oil"));
    }
    @Override
    public void buildWheel() {
        car.setWheel(new Wheel(20));
    }
    @Override
    public void buildNavigation() {
        car.setNavigation(new Navigation("gps"));
    }
    @Override
    public void buildComputer() {
        car.setComputer(new Computer("windows"));
    }
    @Override
    public Car getCar() {
        return car;
    }
}

SuvCarBuilder

package online.javabook.gof.creational.patterns4.builder.car.builder.impl;
import online.javabook.gof.creational.patterns4.builder.car.builder.api.ICarBuilder;
import online.javabook.gof.creational.patterns4.builder.car.product.part.Frame;
import online.javabook.gof.creational.patterns4.builder.car.product.part.*;
import online.javabook.gof.creational.patterns4.builder.car.product.main.Car;
import java.awt.*;
public class SuvCarBuilder implements ICarBuilder {
    private Car car = new Car();
    @Override
    public void buildFrame() {
        car.setFrame(new Frame(Color.RED));
    }
    @Override
    public void buildEngine() {
        car.setEngine(new Engine("oil"));
    }
    @Override
    public void buildWheel() {
        car.setWheel(new Wheel(30));
    }
    @Override
    public void buildNavigation() {
        car.setNavigation(new Navigation("beidou"));
    }
    @Override
    public void buildComputer() {
        car.setComputer(new Computer("ios"));
    }
    @Override
    public Car getCar() {
        return car;
    }
}

主体产品角色

汽车和零件之间是主体和局部的关系

Car

package online.javabook.gof.creational.patterns4.builder.car.product.main;
import online.javabook.gof.creational.patterns4.builder.car.product.part.*;
public class Car {
    private Frame frame;
    private Engine engine;
    private Wheel wheel;
    private Navigation navigation;
    private Computer computer;
    public Frame getFrame() {
        return frame;
    }
    public void setFrame(Frame frame) {
        this.frame = frame;
    }
    public Engine getEngine() {
        return engine;
    }
    public void setEngine(Engine engine) {
        this.engine = engine;
    }
    public Wheel getWheel() {
        return wheel;
    }
    public void setWheel(Wheel wheel) {
        this.wheel = wheel;
    }
    public Navigation getNavigation() {
        return navigation;
    }
    public void setNavigation(Navigation navigation) {
        this.navigation = navigation;
    }
    public Computer getComputer() {
        return computer;
    }
    public void setComputer(Computer computer) {
        this.computer = computer;
    }
    @Override
    public String toString() {
        return "Car{" +
                "frame=" + frame +
                ", engine=" + engine +
                ", wheel=" + wheel +
                ", navigation=" + navigation +
                ", computer=" + computer +
                '}';
    }
}

局部产品角色

Computer

package online.javabook.gof.creational.patterns4.builder.car.product.part;
public class Computer {
    private String os;
    public Computer(String os) {
        this.os = os;
    }
    public String getOs() {
        return os;
    }
    @Override
    public String toString() {
        return "Computer{" +
                "os='" + os + '\'' +
                '}';
    }
}

Engine

package online.javabook.gof.creational.patterns4.builder.car.product.part;
public class Engine {
    private String type;
    public Engine(String type) {
        this.type = type;
    }
    public String getType() {
        return type;
    }
    @Override
    public String toString() {
        return "Engine{" +
                "type='" + type + '\'' +
                '}';
    }
}

Frame

package online.javabook.gof.creational.patterns4.builder.car.product.part;

import java.awt.*;

public class Frame {

    private Color color;

    public Frame(Color color) {
        this.color = color;
    }

    public Color getColor() {
        return color;
    }

    @Override
    public String toString() {
        return "Frame{" +
                "color=" + color +
                '}';
    }
}

Navigation

package online.javabook.gof.creational.patterns4.builder.car.product.part;

public class Navigation {

    private String gps;

    public Navigation(String gps) {
        this.gps = gps;
    }

    public String getGps() {
        return gps;
    }

    @Override
    public String toString() {
        return "Navigation{" +
                "gps='" + gps + '\'' +
                '}';
    }
}

Wheel

package online.javabook.gof.creational.patterns4.builder.car.product.part;

public class Wheel {

    private int size;

    public Wheel(int size) {
        this.size = size;
    }

    public int getSize() {
        return size;
    }

    @Override
    public String toString() {
        return "Wheel{" +
                "size=" + size +
                '}';
    }
}

Director角色

Director负责指挥建造者完成生产，Director无需关心建造者是如何工作的，只需在更高的层次组织建造者工作即可，也就是说建造者的主体逻辑会非常简洁，调整建造者会非常容易

package online.javabook.gof.creational.patterns4.builder.car.director.api;

import online.javabook.gof.creational.patterns4.builder.car.builder.api.ICarBuilder;

public class CarDirector {

    private ICarBuilder carBuilder;

    public CarDirector(ICarBuilder carBuilder) {
        this.carBuilder = carBuilder;
    }

    public void construct() {
        carBuilder.buildFrame();
        carBuilder.buildEngine();
        carBuilder.buildWheel();
        carBuilder.buildComputer();
        carBuilder.buildNavigation();
    }
}

不基于Builder模式的实现

Main

package online.javabook.gof.creational.patterns4.builder.car.app.bad;

import online.javabook.gof.creational.patterns4.builder.car.product.part.Frame;
import online.javabook.gof.creational.patterns4.builder.car.product.part.*;
import online.javabook.gof.creational.patterns4.builder.car.product.main.Car;

import java.awt.*;

public class Main {
    public static void main(String[] args) {

        Frame frame = null;
        Engine engine = null;
        Wheel wheel = null;
        Computer computer = null;
        Navigation navigation = null;

        String type = "city";
        if(type.equals("city")) {
            frame = new Frame(Color.BLACK);
            engine = new Engine("oil");
            wheel = new Wheel(30);
            computer = new Computer("android");
            navigation = new Navigation("gps");

        }else if(type.equals("suv")) {
            frame = new Frame(Color.RED);
            engine = new Engine("oil");
            wheel = new Wheel(20);
            computer = new Computer("ios");
            navigation = new Navigation("gps");

        }else if(type.equals("city")) {
            frame = new Frame(Color.CYAN);
            engine = new Engine("oil");
            wheel = new Wheel(30);
            computer = new Computer("windows");
            navigation = new Navigation("beidou");

        }

        Car car = new Car();
        car.setFrame(frame);
        car.setEngine(engine);
        car.setWheel(wheel);
        car.setComputer(computer);
        car.setNavigation(navigation);

        System.out.println(car);
    }
}

Console

Car{frame=Frame{color=java.awt.Color[r=0,g=0,b=0]}, engine=Engine{type='oil'}, wheel=Wheel{size=30}, navigation=Navigation{gps='gps'}, computer=Computer{os='android'}}

基于Builder模式的实现

Main

package online.javabook.gof.creational.patterns4.builder.car.app.good;

import online.javabook.gof.creational.patterns4.builder.car.builder.api.ICarBuilder;
import online.javabook.gof.creational.patterns4.builder.car.builder.impl.CityCarBuilder;
import online.javabook.gof.creational.patterns4.builder.car.builder.impl.SportCarBuilder;
import online.javabook.gof.creational.patterns4.builder.car.builder.impl.SuvCarBuilder;
import online.javabook.gof.creational.patterns4.builder.car.director.api.CarDirector;
import online.javabook.gof.creational.patterns4.builder.car.product.main.Car;

public class Main {
    public static void main(String[] args) {

        ICarBuilder carBuilder = null;

        String type = "city";
        if(type.equals("city")) {
            carBuilder = new CityCarBuilder();

        }else if(type.equals("suv")) {
            carBuilder = new SuvCarBuilder();

        }else if(type.equals("city")) {
            carBuilder = new SportCarBuilder();
        }

        CarDirector carDirector = new CarDirector(carBuilder);
        carDirector.construct();
        Car car = carBuilder.getCar();
        System.out.println(car);
    }
}

Console

Car{frame=Frame{color=java.awt.Color[r=0,g=0,b=0]}, engine=Engine{type='oil'}, wheel=Wheel{size=10}, navigation=Navigation{gps='gps'}, computer=Computer{os='android'}}