java 过滤器模式(Filter/Criteria Pattern)详细介绍

java 过滤器模式(Filter/Criteria Pattern)

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。

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

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

验证输出。

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 ]

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