设计模式学习笔记--过滤器模式

八、过滤器模式

过滤器模式(Filter Pattern)或标准模式(Criteria Pattern)，允许开发者通过不同的标准类过滤一组对象，通过逻辑运算以解耦的方式把它们连接起来。

实现

通过创建Person类、Criteria接口和实现类，来过滤Person对象的列表。

- 创建实体类

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;  }}

• 创建接口

Criteria.java

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

• 创建接口实现类

CriteriaMale.java

import java.util.ArrayList;import java.util.List;public class CriteriaMate 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;   }}

• 演示

使用不同标准来过滤Person对象
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()            +" ]");      }   }      }

• 输出

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 ]