[009] Design Patterns - Filter Pattern

2015. 12. 8. 09:57

Design Patterns - Filter Pattern

(원문 위치 : http://www.tutorialspoint.com/design_pattern/filter_pattern.htm )

필터(Filter) 또는 기준(Criteria) 패턴은 개발자가 다른 기준과 논리적 연산을 통해 분리된 방법으로 이것들을 연결(chain)하는 것을 사용하여 객체 셋(set of objects)를 필터하는 것을 가능하게 한다. 이 디자인 패턴의 형태는 이 패턴이 단일의 기준을 얻기 위해 다수의 기준을 묶기 때문에 구조적 패턴에 속한다.

Implementation

Person 객체, Criteria 인터페이스 그리고 Person 객체의 목록을 필터하기 위해 이 인터페이스를 구현하는 구체적인 클래스를 생성할 것이다. CriteriaPatternDemo, demo 클래스는 다양한 기준과 그것들을 조합에 기초하여 Person객체 리스트를 필터하기 위해 Criteria 객체를 사용한다.

Filter Pattern UML Diagram

Step 1

기준이 적용되기위한 클래스를 생성한다.

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;
   }	
}

Step 2

기준을 위한 인터페이스를 생성한다.

Criteria.java

import java.util.List;

public interface Criteria {
   public List<Person> meetCriteria(List<Person> persons);
}

Step 3

Criteria인터페이스를 구현하는 구체적인 클래스를 생성한다.

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;
   }
}

Step4

다른 기준과 person을 필터하기 위한 기준의 조합을 사용한다.

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() + " ]");
      }
   }      
}

Step 5

결과를 확인한다.

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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