【設計模式】（十八）--結構型模式--過濾器模式

【設計模式】（十八）–結構型模式–過濾器模式

過濾器模式定義

Filter pattern or Criteria pattern is a design pattern that enables developers to filter a set of objects using different criteria and chaining them in a decoupled way through logical operations.

意思是：過濾器模式或“標準”模式是一種設計模式，使開發人員可以使用不同的標準過濾一組對象，並通過邏輯操作以解耦的方式鏈接它們。

過濾器模式結合多個標準來獲得單一標準，通常有如下個元素

• Criteria 抽象過濾條件的接口
• Concrete Criteria 根據需要實現過濾條件接口的具體過濾條件
• Need Filter Object 需要過濾的對象

過濾器模式雖然不是我們常說的二十三種設計模式之一，但是在在應用中廣泛使用。

過濾器模式的優點

過濾器模式結構清晰，解耦合

過濾器模式的使用場景

• 對大量類似對象有相同的過濾邏輯

過濾器模式的簡單實現

類圖

實現

public class Test {
    public static void main(String[] args) {
        List<Hero> heroList = getHeroList();
        Criteria price8888Criteria = new Price8888Criteria();
        Criteria price13888Criteria = new Price13888Criteria();
        Criteria marksmanCriteria = new MarksmanCriteria();
        Criteria price8888AndMarksmanCriteria = new AndCriteria(price8888Criteria, marksmanCriteria);
        Criteria price8888OrPrice13888Criteria = new OrCriteria(price8888Criteria, price13888Criteria);
        System.out.println("所有英雄列表");
        printHeroInfo(heroList);
        System.out.println("13888英雄");
        List<Hero> price13888HeroList = price13888Criteria.meetCriteria(heroList);
        printHeroInfo(price13888HeroList);
        System.out.println("8888英雄");
        List<Hero> price8888HeroList = price8888Criteria.meetCriteria(heroList);
        printHeroInfo(price8888HeroList);
        System.out.println("所有射手英雄");
        List<Hero> marksmanList = marksmanCriteria.meetCriteria(heroList);
        printHeroInfo(marksmanList);
        System.out.println("價格爲8888的射手英雄");
        List<Hero> price8888MarksmanList = price8888AndMarksmanCriteria.meetCriteria(heroList);
        printHeroInfo(price8888MarksmanList);
        System.out.println("價格爲8888或者13888的英雄");
        List<Hero> price8888Or13888List = price8888OrPrice13888Criteria.meetCriteria(heroList);
        printHeroInfo(price8888Or13888List);

    }

    private static List<Hero> getHeroList() {
        List<Hero> heroList = new ArrayList<>();
        heroList.add(new Hero("魯班七號", 8888, Profession.MARKSMAN));
        heroList.add(new Hero("狄仁傑", 8888, Profession.MARKSMAN));
        heroList.add(new Hero("黃忠", 13888, Profession.MARKSMAN));
        heroList.add(new Hero("王昭君", 8888, Profession.MAGE));
        heroList.add(new Hero("馬可波羅", 13888, Profession.MARKSMAN));
        heroList.add(new Hero("貂蟬", 13888, Profession.MAGE));
        heroList.add(new Hero("曜", 13888, Profession.ASSASSIN));
        heroList.add(new Hero("老夫子", 8888, Profession.FIGHTER));
        heroList.add(new Hero("李元芳", 13888, Profession.MARKSMAN));
        return heroList;
    }

    private static void printHeroInfo(List<Hero> heroList) {
        StringBuffer heroBuffer = new StringBuffer();
        for (Hero hero : heroList) {
            heroBuffer.append(hero.getName());
            heroBuffer.append(";");
        }
        System.out.println("             " + heroBuffer.toString());
    }
}
public interface Criteria {
    List<Hero> meetCriteria(List<Hero> heroList);
}
public class Hero {
    private String name;

    private int price;

    private Profession profession;

    public Hero(String name, int price, Profession profession) {
        this.name = name;
        this.price = price;
        this.profession = profession;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public int getPrice() {
        return price;
    }

    public void setPrice(int price) {
        this.price = price;
    }

    public Profession getProfession() {
        return profession;
    }

    public void setProfession(Profession profession) {
        this.profession = profession;
    }
}
public enum Profession {
    MAGE("mege", "法師"),
    ASSASSIN("assassin","刺客"),
    FIGHTER("fighter","戰士"),
    SUPPORT("support","輔助"),
    TANK("tank","坦克"),
    MARKSMAN("marksman", "射手");
    private String profession;
    private String zhName;

    private Profession(String profession, String zhName) {
        this.profession = profession;
        this.zhName = zhName;
    }

}
public class Price8888Criteria implements Criteria {

    private static final int PRICE_8888 = 8888;

    @Override
    public List<Hero> meetCriteria(List<Hero> heroList) {
        List<Hero> price8888 = new ArrayList<>();
        for (Hero hero : heroList) {
            if (PRICE_8888 == hero.getPrice()) {
                price8888.add(hero);
            }
        }
        return price8888;
    }
}
public class Price13888Criteria implements Criteria {

    private static final int PRICE_13888 = 13888;

    @Override
    public List<Hero> meetCriteria(List<Hero> heroList) {
        List<Hero> price13888 = new ArrayList<>();
        for (Hero hero : heroList) {
            if (PRICE_13888 == hero.getPrice()) {
                price13888.add(hero);
            }
        }
        return price13888;
    }
}
public class MarksmanCriteria implements Criteria {

    @Override
    public List<Hero> meetCriteria(List<Hero> heroList) {
        List<Hero> maksmanList = new ArrayList<>();
        for (Hero hero : heroList) {
            if (Profession.MARKSMAN == hero.getProfession()) {
                maksmanList.add(hero);
            }
        }
        return maksmanList;
    }
}
public class AndCriteria implements Criteria {

    private Criteria criteria;
    private Criteria otherCriteria;

    public AndCriteria(Criteria criteria, Criteria otherCriteria) {
        this.criteria = criteria;
        this.otherCriteria = otherCriteria;
    }

    @Override
    public List<Hero> meetCriteria(List<Hero> heroList) {
        List<Hero> firstCriteriaPersons = criteria.meetCriteria(heroList);
        return otherCriteria.meetCriteria(firstCriteriaPersons);
    }
}
public class OrCriteria implements Criteria {

    private Criteria criteria;
    private Criteria otherCriteria;

    public OrCriteria(Criteria criteria, Criteria otherCriteria) {
        this.criteria = criteria;
        this.otherCriteria = otherCriteria;
    }

    @Override
    public List<Hero> meetCriteria(List<Hero> heroList) {
        List<Hero> firstCriteriaItems = criteria.meetCriteria(heroList);
        List<Hero> otherCriteriaItems = otherCriteria.meetCriteria(heroList);

        for (Hero hero : otherCriteriaItems) {
            if (!firstCriteriaItems.contains(hero)) {
                firstCriteriaItems.add(hero);
            }
        }
        return firstCriteriaItems;
    }
}

結果

實現解讀
通過過濾器模式實現王者榮耀中部分英雄列表的過濾。