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设计模式
(追記) (追記ここまで)

过滤器模式

过滤器模式(Filter Pattern)或标准模式(Criteria Pattern)是一种设计模式,这种模式允许开发人员使用不同的标准来过滤一组对象,通过逻辑运算以解耦的方式把它们连接起来。这种类型的设计模式属于结构型模式,它结合多个标准来获得单一标准。

概要

意图

用于将对象的筛选过程封装起来,允许使用不同的筛选标准动态地筛选对象。

主要解决的问题

当需要根据多个不同的条件或标准来筛选一组对象时,过滤器模式提供了一种灵活的方式来定义这些条件,避免在客户端代码中硬编码筛选逻辑。

使用场景

  • 当对象集合需要根据不同的标准进行筛选时。
  • 当筛选逻辑可能变化,或者需要动态地组合多个筛选条件时。

实现方式

  • 定义筛选接口:创建一个筛选接口,定义一个筛选方法。
  • 实现具体筛选器:为每个筛选标准实现筛选接口,封装具体的筛选逻辑。
  • 组合筛选器:允许筛选器之间进行组合,形成复杂的筛选逻辑。

关键代码

  • 筛选接口:定义筛选方法,如 matches()。
  • 具体筛选器类:实现筛选接口,封装具体的筛选逻辑。
  • 组合筛选器:实现筛选器的组合逻辑,如逻辑与(AND)、逻辑或(OR)等。

应用实例

  1. 图书管理系统:根据作者、出版年份、类别等不同标准筛选图书。
  2. 在线购物平台:根据价格、品牌、用户评分等条件筛选商品。

优点

  1. 封装性:筛选逻辑被封装在独立的筛选器对象中。
  2. 灵活性:可以动态地添加、修改或组合筛选条件。
  3. 可扩展性:容易添加新的筛选标准,无需修改现有代码。

缺点

  • 复杂性:随着筛选条件的增加,系统可能变得复杂。
  • 性能问题:如果筛选器组合过于复杂,可能会影响性能。

使用建议

  • 当筛选逻辑可能变化或需要根据不同标准动态筛选对象时,考虑使用过滤器模式。
  • 在设计时,确保筛选器的接口和实现保持一致,以便于组合和扩展。

注意事项

  • 确保筛选器的组合逻辑正确无误,避免引入逻辑错误。
  • 在实现时,考虑性能影响,特别是在处理大量数据时。

概要

过滤器模式包含以下几个主要角色:

  • 过滤器接口(Filter/Criteria):定义一个接口,用于筛选对象。该接口通常包含一个方法,用于根据特定条件过滤对象。

  • 具体过滤器类(Concrete Filter/Concrete Criteria):实现过滤器接口,具体定义筛选对象的条件和逻辑。

  • 对象集合(Items/Objects to be filtered):要被过滤的对象集合。这些对象通常是具有共同属性的实例,例如一组人、一组产品等。

  • 客户端(Client):使用具体过滤器类来筛选对象集合。客户端将对象集合和过滤器结合起来,以获得符合条件的对象。

实现

我们将创建一个 Person 对象、Criteria 接口和实现了该接口的实体类,来过滤 Person 对象的列表。CriteriaPatternDemo 类使用 Criteria 对象,基于各种标准和它们的结合来过滤 Person 对象的列表。

过滤器模式的 UML 图

步骤 1

创建一个类,在该类上应用标准。

Person.java

publicclassPerson{privateStringname; privateStringgender; privateStringmaritalStatus; publicPerson(Stringname,Stringgender,StringmaritalStatus){this.name = name; this.gender = gender; this.maritalStatus = maritalStatus; }publicStringgetName(){returnname; }publicStringgetGender(){returngender; }publicStringgetMaritalStatus(){returnmaritalStatus; }}

步骤 2

为标准(Criteria)创建一个接口。

Criteria.java

importjava.util.List; publicinterfaceCriteria{publicList<Person> meetCriteria(List<Person> persons); }

步骤 3

创建实现了 Criteria 接口的实体类。

CriteriaMale.java

importjava.util.ArrayList; importjava.util.List; publicclassCriteriaMaleimplementsCriteria{ @OverridepublicList<Person> meetCriteria(List<Person> persons){List<Person> malePersons = newArrayList<Person>(); for(Personperson : persons){if(person.getGender().equalsIgnoreCase("MALE")){malePersons.add(person); }}returnmalePersons; }}

CriteriaFemale.java

importjava.util.ArrayList; importjava.util.List; publicclassCriteriaFemaleimplementsCriteria{ @OverridepublicList<Person> meetCriteria(List<Person> persons){List<Person> femalePersons = newArrayList<Person>(); for(Personperson : persons){if(person.getGender().equalsIgnoreCase("FEMALE")){femalePersons.add(person); }}returnfemalePersons; }}

CriteriaSingle.java

importjava.util.ArrayList; importjava.util.List; publicclassCriteriaSingleimplementsCriteria{ @OverridepublicList<Person> meetCriteria(List<Person> persons){List<Person> singlePersons = newArrayList<Person>(); for(Personperson : persons){if(person.getMaritalStatus().equalsIgnoreCase("SINGLE")){singlePersons.add(person); }}returnsinglePersons; }}

AndCriteria.java

importjava.util.List; publicclassAndCriteriaimplementsCriteria{privateCriteriacriteria; privateCriteriaotherCriteria; publicAndCriteria(Criteriacriteria, CriteriaotherCriteria){this.criteria = criteria; this.otherCriteria = otherCriteria; } @OverridepublicList<Person> meetCriteria(List<Person> persons){List<Person> firstCriteriaPersons = criteria.meetCriteria(persons); returnotherCriteria.meetCriteria(firstCriteriaPersons); }}

OrCriteria.java

importjava.util.List; publicclassOrCriteriaimplementsCriteria{privateCriteriacriteria; privateCriteriaotherCriteria; publicOrCriteria(Criteriacriteria, CriteriaotherCriteria){this.criteria = criteria; this.otherCriteria = otherCriteria; } @OverridepublicList<Person> meetCriteria(List<Person> persons){List<Person> firstCriteriaItems = criteria.meetCriteria(persons); List<Person> otherCriteriaItems = otherCriteria.meetCriteria(persons); for(Personperson : otherCriteriaItems){if(!firstCriteriaItems.contains(person)){firstCriteriaItems.add(person); }}returnfirstCriteriaItems; }}

步骤4

使用不同的标准(Criteria)和它们的结合来过滤 Person 对象的列表。

CriteriaPatternDemo.java

importjava.util.ArrayList; importjava.util.List; publicclassCriteriaPatternDemo{publicstaticvoidmain(String[]args){List<Person> persons = newArrayList<Person>(); persons.add(newPerson("Robert","Male", "Single")); persons.add(newPerson("John","Male", "Married")); persons.add(newPerson("Laura","Female", "Married")); persons.add(newPerson("Diana","Female", "Single")); persons.add(newPerson("Mike","Male", "Single")); persons.add(newPerson("Bobby","Male", "Single")); Criteriamale = newCriteriaMale(); Criteriafemale = newCriteriaFemale(); Criteriasingle = newCriteriaSingle(); CriteriasingleMale = newAndCriteria(single, male); CriteriasingleOrFemale = newOrCriteria(single, female); System.out.println("Males: "); printPersons(male.meetCriteria(persons)); System.out.println("\nFemales: "); printPersons(female.meetCriteria(persons)); System.out.println("\nSingle Males: "); printPersons(singleMale.meetCriteria(persons)); System.out.println("\nSingle Or Females: "); printPersons(singleOrFemale.meetCriteria(persons)); }publicstaticvoidprintPersons(List<Person> persons){for(Personperson : persons){System.out.println("Person : [ Name : " + person.getName() +", Gender : " + person.getGender() +", Marital Status : " + person.getMaritalStatus() +" ]"); }}}

步骤 5

执行程序,输出结果:

Males: 
Person : [ Name : Robert, Gender : Male, Marital Status : Single ]
Person : [ Name : John, Gender : Male, Marital Status : Married ]
Person : [ Name : Mike, Gender : Male, Marital Status : Single ]
Person : [ Name : Bobby, Gender : Male, Marital Status : Single ]
Females: 
Person : [ Name : Laura, Gender : Female, Marital Status : Married ]
Person : [ Name : Diana, Gender : Female, Marital Status : Single ]
Single Males: 
Person : [ Name : Robert, Gender : Male, Marital Status : Single ]
Person : [ Name : Mike, Gender : Male, Marital Status : Single ]
Person : [ Name : Bobby, Gender : Male, Marital Status : Single ]
Single Or Females: 
Person : [ Name : Robert, Gender : Male, Marital Status : Single ]
Person : [ Name : Diana, Gender : Female, Marital Status : Single ]
Person : [ Name : Mike, Gender : Male, Marital Status : Single ]
Person : [ Name : Bobby, Gender : Male, Marital Status : Single ]
Person : [ Name : Laura, Gender : Female, Marital Status : Married ]
AI 思考中...

4 篇笔记 写笔记

  1. #0

    dream_on_sakura_rain

    271***[email protected]

    18

    过滤模式的实现在java8里面有典型的应用方法就是分组操作,可以根据指定的指标进行分组筛选。

    Map<Integer, List<Person >> groupMap = persons.stream().collect(Collectors.groupingBy(Person::getGender));
groupMap.forEach((k, v) -> {
 System.out.println(k);
 v.forEach(System.out::println);
});

    得到的结果形式就是:

    • k:是分组的指标,上面代码中的 gender
    • v:是一个list的集合对象,就是 personList

    dream_on_sakura_rain

    271***[email protected]

    8年前 (2018年09月01日)
  2. #0

    Veminga

    115***[email protected]

    8

    Java8 中有单独的过滤器。

    eg:

    List<String> aList = Lists.newArrayList("1","2","");
aList.stream().filter(x -> StringUtils.isNotEmpty(x))

    这个方法可以可获取到全部非空的字符串。

    Veminga

    115***[email protected]

    7年前 (2019年10月16日)
  3. #0

    Lonnie

    354***[email protected]

    0

    Swift 实现,直接贴代码:

    struct Person: Hashable {
 let name: String
 let gender: String
 let maritalStatus: String
}
protocol Criteria {
 func meetCriteria(_ persons: [Person]) -> [Person]
}
struct CriteriaMale: Criteria {
 func meetCriteria(_ persons: [Person]) -> [Person] {
 return persons.filter({0ドル.gender.uppercased() == "MALE"})
 }
}
struct CriteriaFemale: Criteria {
 func meetCriteria(_ persons: [Person]) -> [Person] {
 return persons.filter({0ドル.gender.uppercased() == "FEMALE"})
 }
}
struct CriteriaSingle: Criteria {
 func meetCriteria(_ persons: [Person]) -> [Person] {
 return persons.filter({0ドル.maritalStatus.uppercased() == "SINGLE"})
 }
}
struct AndCriteria: Criteria {
 var criteria: Criteria
 var otherCriteria: Criteria
 func meetCriteria(_ persons: [Person]) -> [Person] {
 return criteria.meetCriteria(otherCriteria.meetCriteria(persons))
 }
}
struct OrCriteria: Criteria {
 var criteria: Criteria
 var otherCriteria: Criteria
 func meetCriteria(_ persons: [Person]) -> [Person] {
 return Array(Set(criteria.meetCriteria(persons)).union(otherCriteria.meetCriteria(persons)))
 }
}
class FilterPattern: ListItem {
 func execute() {
 var persons = [Person]();
 persons.append(Person(name: "Robert",gender: "Male", maritalStatus: "Single"))
 persons.append(Person(name: "John",gender: "Male", maritalStatus: "Married"))
 persons.append(Person(name: "Laura",gender: "Female", maritalStatus: "Married"))
 persons.append(Person(name: "Diana",gender: "Female", maritalStatus: "Single"))
 persons.append(Person(name: "Mike",gender: "Male", maritalStatus: "Single"))
 persons.append(Person(name: "Bobby",gender: "Male", maritalStatus: "Single"))
 let male = CriteriaMale()
 let female = CriteriaFemale()
 let single = CriteriaSingle()
 let singleMale = AndCriteria(criteria: single, otherCriteria: male)
 let singleOrFemale = OrCriteria(criteria: single, otherCriteria: female)
 
 print("Males: ");
 print(male.meetCriteria(persons))
 print("\nFemales: ")
 print(female.meetCriteria(persons))
 
 print("\nSingle Males: ");
 print(singleMale.meetCriteria(persons))
 print("\nSingle Or Females: ");
 print(singleOrFemale.meetCriteria(persons))
 }
}
var persons = [Person]();
persons.append(Person(name: "Robert",gender: "Male", maritalStatus: "Single"))
persons.append(Person(name: "John",gender: "Male", maritalStatus: "Married"))
persons.append(Person(name: "Laura",gender: "Female", maritalStatus: "Married"))
persons.append(Person(name: "Diana",gender: "Female", maritalStatus: "Single"))
persons.append(Person(name: "Mike",gender: "Male", maritalStatus: "Single"))
persons.append(Person(name: "Bobby",gender: "Male", maritalStatus: "Single"))
let male = CriteriaMale()
let female = CriteriaFemale()
let single = CriteriaSingle()
let singleMale = AndCriteria(criteria: single, otherCriteria: male)
let singleOrFemale = OrCriteria(criteria: single, otherCriteria: female)
print("Males: ");
print(male.meetCriteria(persons))
print("\nFemales: ")
print(female.meetCriteria(persons))
print("\nSingle Males: ");
print(singleMale.meetCriteria(persons))
print("\nSingle Or Females: ");
print(singleOrFemale.meetCriteria(persons))

    Lonnie

    354***[email protected]

    7年前 (2019年12月11日)
  4. #0

    Siskin.xu

    sis***@sohu.com

    2

    Python 代码:

    # Filter Pattern with Python Code
from abc import abstractmethod,ABCMeta
# 创建一个类,在该类上应用标准
class Person():
 _name = ""
 _gender = ""
 _maritalStatus = ""
 def __init__(self,inName,inGender,inMaritalStatus):
 self._name = inName
 self._gender = inGender
 self._maritalStatus = inMaritalStatus
 def getName(self):
 return self._name
 def getGender(self):
 return self._gender
 def getMaritalStatus(self):
 return self._maritalStatus
 @staticmethod 
 def printPersons(inPersons): 
 for aPerson in inPersons: 
 print("Person : [ Name : {0}, Gender : {1}, Marital Status : {2}]".format(aPerson.getName(),aPerson.getGender(),aPerson.getMaritalStatus()))
# 为标准(Criteria)创建一个接口
class Criteria(metaclass=ABCMeta): 
 @abstractmethod 
 def meetCriteria(self,inPersons): 
 pass
# 创建实现了Criteria接口的实体类
class CriteriaMale(Criteria): 
 def meetCriteria(self,inPersons): 
 malePersons = [] 
 for aPerson in inPersons:
 if aPerson.getGender().upper() == "MALE":
 malePersons.append(aPerson)
 return malePersons
class CriteriaFemale(Criteria):
 def meetCriteria(self,inPersons):
 femalePersons = []
 for aPerson in inPersons:
 if aPerson.getGender().upper() == "FEMALE":
 femalePersons.append(aPerson)
 return femalePersons
class CriteriaSingle(Criteria):
 def meetCriteria(self,inPersons):
 singlePersons = []
 for aPerson in inPersons:
 if aPerson.getMaritalStatus().upper() == "SINGLE":
 singlePersons.append(aPerson)
 return singlePersons
class AndCriteria(Criteria):
 _criteria = None
 _otherCriteria = None 
 def __init__(self,inCriteria,inOtherCriteria): 
 self._criteria = inCriteria 
 self._otherCriteria = inOtherCriteria 
 def meetCriteria(self,inPersons): 
 # 获得第一次过滤结果 
 firstCriteriaPerson = self._criteria.meetCriteria(inPersons) 
 # 返回第二次过滤结果 
 return self._otherCriteria.meetCriteria(firstCriteriaPerson)
class OrCriteria(Criteria): 
 _criteria = None 
 _otherCriteria = None 
 def __init__(self, inCriteria, inOtherCriteria): 
 self._criteria = inCriteria 
 self._otherCriteria = inOtherCriteria 
 def meetCriteria(self,inPersons): 
 #先用Criteria分别构造数据 
 firstCriteriaItems = self._criteria.meetCriteria(inPersons) 
 otherCriteriaItems = self._otherCriteria.meetCriteria(inPersons) 
 # 完成或运算 
 for aPerson in otherCriteriaItems: 
 if aPerson not in firstCriteriaItems :
 firstCriteriaItems.append(aPerson)
 return firstCriteriaItems
# 调用输出
if __name__ == '__main__': 
 persons = [] 
 persons.append(Person("Robert","Male","Single")) 
 persons.append(Person("John", "Male", "Married")) 
 persons.append(Person("Laura", "Female", "Married")) 
 persons.append(Person("Diana", "Female", "Single")) 
 persons.append(Person("Mike", "Male", "Single")) 
 persons.append(Person("Bobby", "Male", "Single")) 
 male = CriteriaMale() female = CriteriaFemale() 
 single = CriteriaSingle() 
 singleMale = AndCriteria(single, male) 
 singleOrFemale = OrCriteria(single,female) 
 print("Males: ") 
 Person.printPersons(male.meetCriteria(persons)) 
 print("\nFemales: ") 
 Person.printPersons(female.meetCriteria(persons)) 
 print("\nSingle: ") 
 Person.printPersons(single.meetCriteria(persons)) 
 print("\nSingle Males: ") 
 Person.printPersons(singleMale.meetCriteria(persons)) 
 print("\nSingle or Female:") 
 Person.printPersons(singleOrFemale.meetCriteria(persons))

    Siskin.xu

    sis***@sohu.com

    6年前 (2020年03月11日)

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