java 過濾器模式(Filter/Criteria Pattern)詳細介紹

更新時間：2016年10月02日 10:26:18 投稿：lqh

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java 過濾器模式(Filter/Criteria Pattern)

過濾器模式（Filter Pattern）或標準模式（Criteria Pattern）是一種設(shè)計模式，這種模式允許開發(fā)人員使用不同的標準來過濾一組對象，通過邏輯運算以解耦的方式把它們連接起來。這種類型的設(shè)計模式屬于結(jié)構(gòu)型模式，它結(jié)合多個標準來獲得單一標準。

實現(xiàn)

我們將創(chuàng)建一個 Person 對象、Criteria 接口和實現(xiàn)了該接口的實體類，來過濾 Person 對象的列表。CriteriaPatternDemo，我們的演示類使用 Criteria 對象，基于各種標準和它們的結(jié)合來過濾 Person 對象的列表。

步驟 1

創(chuàng)建一個類，在該類上應(yīng)用標準。

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;
  }  
}

步驟 2

為標準（Criteria）創(chuàng)建一個接口。

Criteria.java

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

步驟 3

創(chuàng)建實現(xiàn)了 Criteria 接口的實體類。

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;
  }
}

步驟4

使用不同的標準（Criteria）和它們的結(jié)合來過濾 Person 對象的列表。

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()
      +" ]");
   }
  }   
}

步驟 5

驗證輸出。

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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