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。

 

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，我们的演示类使用 Criteria 对象，基于各种标准和它们的结合来过滤 Person 对象的列表。

步骤 1

创建一个类，在该类上应用标准。

Person.java

public class Person { private String name; private String gender; private String maritalStatus; public Person(String name,String gender,String maritalStatus){ this.name = name; this.gender = gender; this.maritalStatus = maritalStatus; } public String getName() { return name; } public String getGender() { return gender; } public String getMaritalStatus() { return maritalStatus; } }

步骤 2

为标准（Criteria）创建一个接口。

Criteria.java

import java.util.List; public interface Criteria { public List<Person> meetCriteria(List<Person> persons); }

步骤 3

创建实现了 Criteria 接口的实体类。

CriteriaMale.java

import java.util.ArrayList; import java.util.List; public class CriteriaMale implements Criteria { @Override public List<Person> meetCriteria(List<Person> persons) { List<Person> malePersons = new ArrayList<Person>(); for (Person person : persons) { if(person.getGender().equalsIgnoreCase("MALE")){ malePersons.add(person); } } return malePersons; } }

CriteriaFemale.java

import java.util.ArrayList; import java.util.List; public class CriteriaFemale implements Criteria { @Override public List<Person> meetCriteria(List<Person> persons) { List<Person> femalePersons = new ArrayList<Person>(); for (Person person : persons) { if(person.getGender().equalsIgnoreCase("FEMALE")){ femalePersons.add(person); } } return femalePersons; } }

CriteriaSingle.java

import java.util.ArrayList; import java.util.List; public class CriteriaSingle implements Criteria { @Override public List<Person> meetCriteria(List<Person> persons) { List<Person> singlePersons = new ArrayList<Person>(); for (Person person : persons) { if(person.getMaritalStatus().equalsIgnoreCase("SINGLE")){ singlePersons.add(person); } } return singlePersons; } }

AndCriteria.java

import java.util.List; 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<Person> meetCriteria(List<Person> persons) { List<Person> firstCriteriaPersons = criteria.meetCriteria(persons); return otherCriteria.meetCriteria(firstCriteriaPersons); } }

OrCriteria.java

import java.util.List; 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<Person> meetCriteria(List<Person> persons) { List<Person> firstCriteriaItems = criteria.meetCriteria(persons); List<Person> otherCriteriaItems = otherCriteria.meetCriteria(persons); for (Person person : otherCriteriaItems) { if(!firstCriteriaItems.contains(person)){ firstCriteriaItems.add(person); } } return firstCriteriaItems; } }

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

import java.util.ArrayList; import java.util.List; public class CriteriaPatternDemo { public static void main(String[] args) { List<Person> persons = new ArrayList<Person>(); persons.add(new Person("Robert","Male", "Single")); persons.add(new Person("John","Male", "Married")); persons.add(new Person("Laura","Female", "Married")); persons.add(new Person("Diana","Female", "Single")); persons.add(new Person("Mike","Male", "Single")); persons.add(new Person("Bobby","Male", "Single")); Criteria male = new CriteriaMale(); Criteria female = new CriteriaFemale(); Criteria single = new CriteriaSingle(); Criteria singleMale = new AndCriteria(single, male); Criteria singleOrFemale = new OrCriteria(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)); } public static void printPersons(List<Person> persons){ for (Person person : 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 ]

 桥接模式

组合模式 

 

1 篇笔记 写笔记

1.    dream_on_sakura_rain

     271***2293@qq.com

   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

      dream_on_sakura_rain

     271***2293@qq.com

   9个月前 (09-01)