生成器模式

使用生成器模式封装一个产品的构造过程，并允许按步骤构造。

示例—度假计划

需要为每位客人定制度假计划。由于客人的不同需求，客人自己可以选择旅馆以及各种门票、餐厅订位，甚至也可以选择登记参加特殊的活动。每个客人的度假计划可能都不一样，例如天数、活动类型。比方说，当地居民可能不需要旅馆，但是想要用餐并参与特殊活动。而其他的客人可能是从外地飞过来的，所以需要旅馆、用餐和门票。

UML图表示

生成器模式-度假计划

代码演示

计划类

package Builder;

public class Planner {

    Planner(){
        plan = new StringBuilder();
    }

    private StringBuilder plan;


    public String getPlan() {
        return plan.toString();
    }

    public void addEvent(String event) {
        this.plan.append(event);
        plan.append("\n");
    }
}

生成计划的接口

package Builder;

public interface AbstractBuilder {
    void buildDay(String date);
    void addHotel(String date, String hotel);
    void addReservation(String reservation);
    void addSpecialEvent(String event);
    void addTickets(String tickets);
    Planner getVacationPlanner();
}

生成计划实现类

package Builder;

public class VacationBuilder implements AbstractBuilder {

    Planner vacation;

    VacationBuilder(){
        vacation = new Planner();
    }

    @Override
    public void buildDay(String date) {
        vacation.addEvent("Your plan is in " + date + ". ");
    }

    @Override
    public void addHotel(String date, String hotel) {
        vacation.addEvent("Checking in "+ hotel + " hotel at " + date + ". ");
    }

    @Override
    public void addReservation(String reservation) {
        vacation.addEvent("Your " + reservation + " was reserved. ");
    }

    @Override
    public void addSpecialEvent(String event) {
        vacation.addEvent("You are enjoying " + event + ". ");
    }

    @Override
    public void addTickets(String tickets) {
        vacation.addEvent("You'll have tickets of " + tickets + ". ");
    }

    @Override
    public Planner getVacationPlanner() {
        return vacation;
    }
}

客户类

package Builder;

public class Client {

    Planner constructPlanner(){
       AbstractBuilder builder = new VacationBuilder();

       builder.buildDay("2017-10-01");
       builder.addHotel("2017-10-01","Super Star");
       builder.addReservation("a Mexican restaurant ");
       builder.addSpecialEvent("New Year Concert");
       builder.addTickets("Pattems on Ice");

       return builder.getVacationPlanner();
    }

    String showPlan(){
        return constructPlanner().getPlan();
    }

}

测试代码

package Builder;

public class BuilderDriver {
    public static void main(String[] args) {
        Client C1 = new Client();
        System.out.println("The Plan for C1: ");
        System.out.println(C1.showPlan());
    }
}

测试结果

The Plan for C1: 
Your plan is in 2017-10-01. 
Checking in Super Star hotel at 2017-10-01. 
Your a Mexican restaurant  was reserved. 
You are enjoying New Year Concert. 
You'll have tickets of Pattems on Ice.