设计模式 - 建造者模式（Builder Pattern）

• Separate the construction of a complex object from its representation so that the sameconstruction process can create different representations.（将一个复杂对象的构建与它的表示分离，使得同样的构建过程可以创建不同的表示。）

建造者模式通用类图

 

 

image.png

看上面图可能有点懵，举一个简单的例子

假如现在有一个生产电脑代工厂，可能会生产很多电脑品牌的组装电脑，不同的电脑品牌组装电脑的顺序可能不一样。
假如现在要为两个电脑品牌(联想、华为)组装电脑
这些部件假如只有显示器、键盘、鼠标、硬盘
需求就是这样，为不同电脑品牌组装顺序不一样，但是都提供一个公共的方法assemble()
需求有点复杂我们现在看具体代码

在ComputerModel中我们定义了一个setSequence方法，组装点的这几个动作要如何排布，是在这个ArrayList中定义的。然后assemble()方法根据sequence定义的顺序完成指定的顺序动作

首先创建ComputerModel

import org.apache.commons.lang3.StringUtils;

import java.util.ArrayList;
import java.util.List;

/**
 * @author shuliangzhao
 * @Title: ComputerModel
 * @ProjectName design-parent
 * @Description: TODO
 * @date 2019/5/29 22:40
 */
public abstract class ComputerModel {
    //sequence控制组装顺序
    private List sequence = new ArrayList<>();

    protected abstract void productScreen();
    protected abstract void productMouse();
    protected abstract void productKeyboard();
    protected abstract void productHardDisk();

    public void assemble() {
        for (String str:sequence) {
            if (StringUtils.equals(str,"screen")) {
                this.productScreen();
            }else if (StringUtils.equals(str,"mouse")) {
                this.productMouse();
            }else if (StringUtils.equals(str,"keyboard")) {
                this.productKeyboard();
            }else if (StringUtils.equals(str,"hardDisk")) {
                this.productHardDisk();
            }
        }
    }

    public void setSequence(List sequence) {
        this.sequence = sequence;
    }
}

LenovoComputer

/**
 * @author shuliangzhao
 * @Title: LenovoComputer
 * @ProjectName design-parent
 * @Description: TODO
 * @date 2019/5/29 22:49
 */
    public class LenovoComputer extends ComputerModel {
    @Override
    protected void productScreen() {
        System.out.println("联想电脑组装屏幕");
    }

    @Override
    protected void productMouse() {
        System.out.println("联想电脑组装鼠标");
    }

    @Override
    protected void productKeyboard() {
        System.out.println("联想电脑组装键盘");
    }

    @Override
    protected void productHardDisk() {
        System.out.println("联想电脑组装硬盘");
    }
}

HuaweiComputer

/**
 * @author shuliangzhao
 * @Title: HuaweiComputer
 * @ProjectName design-parent
 * @Description: TODO
 * @date 2019/5/29 22:51
 */
public class HuaweiComputer extends ComputerModel {
    @Override
    protected void productScreen() {
        System.out.println("华为电脑组装屏幕");
    }

    @Override
    protected void productMouse() {
        System.out.println("华为电脑组装鼠标");
    }

    @Override
    protected void productKeyboard() {
        System.out.println("华为电脑组装键盘");
    }

    @Override
    protected void productHardDisk() {
        System.out.println("华为电脑组装硬盘");
    }
}

ComputerBuilder

/**
 * @author shuliangzhao
 * @Title: ComputerBuilder
 * @ProjectName design-parent
 * @Description: TODO
 * @date 2019/5/29 22:51
 */
public abstract class ComputerBuilder {
    //建造一个模型，你要给我一个顺序要求，就是组装顺序
    public abstract void setSequence(List sequence);
    //设置完毕顺序后，就可以直接拿到这个电脑组装顺序
    public abstract ComputerModel getComputerModel();
}

HuaweiBuilder

/**
 * @author shuliangzhao
 * @Title: HuaweiBuilder
 * @ProjectName design-parent
 * @Description: TODO
 * @date 2019/5/29 22:56
 */
public class HuaweiBuilder extends ComputerBuilder {

    private HuaweiComputer huaweiComputer = new HuaweiComputer();

    @Override
    public void setSequence(List sequence) {
        this.huaweiComputer.setSequence(sequence);
    }

    @Override
    public ComputerModel getComputerModel() {
        return this.huaweiComputer;
    }
}

LenovoBuilder

/**
 * @author shuliangzhao
 * @Title: LenovoBuilder
 * @ProjectName design-parent
 * @Description: TODO
 * @date 2019/5/29 22:54
 */
public class LenovoBuilder extends ComputerBuilder {

    private LenovoComputer lenovoComputer = new LenovoComputer();

    @Override
    public void setSequence(List sequence) {
        lenovoComputer.setSequence(sequence);
    }

    @Override
    public ComputerModel getComputerModel() {
        return this.lenovoComputer;
    }
}

场景类Director

/**
 * 场景类可以根据不同场景组装电脑
 * @author shuliangzhao
 * @Title: Director
 * @ProjectName design-parent
 * @Description: TODO
 * @date 2019/5/29 22:57
 */
public class Director {
    private List sequence = new ArrayList<>();
    private HuaweiBuilder huaweiBuilder = new HuaweiBuilder();
    private LenovoBuilder lenovoBuilder = new LenovoBuilder();

    //组装华为A系列先屏幕、鼠标、键盘、硬盘
    public HuaweiComputer getAHuaweiComputer() {
        this.sequence.clear();
        sequence.add("screen");
        sequence.add("mouse");
        sequence.add("keyboard");
        sequence.add("hardDisk");
        this.huaweiBuilder.setSequence(sequence);
        return (HuaweiComputer) this.huaweiBuilder.getComputerModel();
    }

    //组装华为B系列先鼠标、屏幕、硬盘、键盘
    public HuaweiComputer getBHuaweiComputer() {
        this.sequence.clear();
        sequence.add("mouse");
        sequence.add("screen");
        sequence.add("hardDisk");
        sequence.add("keyboard");
        this.huaweiBuilder.setSequence(sequence);
        return (HuaweiComputer) this.huaweiBuilder.getComputerModel();
    }

    //组装联想A系列先硬盘、键盘、鼠标、屏幕
    public LenovoComputer getALenovoComputer() {
        this.sequence.clear();
        sequence.add("hardDisk");
        sequence.add("keyboard");
        sequence.add("mouse");
        sequence.add("screen");
        this.lenovoBuilder.setSequence(sequence);
        return (LenovoComputer) this.lenovoBuilder.getComputerModel();
    }

    //组装联想B系列先键盘、鼠标、硬盘屏幕
    public LenovoComputer getBLenovoComputer() {
        this.sequence.clear();
        sequence.add("keyboard");
        sequence.add("mouse");
        sequence.add("hardDisk");
        sequence.add("screen");
        this.lenovoBuilder.setSequence(sequence);
        return (LenovoComputer) this.lenovoBuilder.getComputerModel();
    }
}

客户端

/**
 * @author shuliangzhao
 * @Title: Client
 * @ProjectName design-parent
 * @Description: TODO
 * @date 2019/5/29 23:07
 */
public class Client {

    public static void main(String[] args) {
        Director director = new Director();
        //组装华为A系列10台
        for (int i = 0;i<2;i++) {
            director.getAHuaweiComputer().assemble();
        }
        //组装联想B系列10台
        for (int i=0;i<2;i++) {
            director.getBLenovoComputer().assemble();
        }
    }
}

运行结果

 

image.png

• 建造者模式优点：

1.具有封装性，使用建造者模式可以使客户端不必知道产品内部组成的细节。
2.建造者独立，容易扩展

• 建造者模式使用场景：

1.相同的方法，不同的执行顺序，产生不同的事件结果时，可以采用建造者模式
2.产品类非常复杂，或者产品类中的调用顺序不同产生了不同的效能，这个时候使用建
造者模式非常合适。

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