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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