过滤器模式

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
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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

1. 创建一个类，在该类上应用标准::

   //Person.java
   public class Person {

   private String name;<br />       private String gender;<br />       private String maritalStatus;
   public Person(String name,String gender,String maritalStatus){<br />          this.name = name;<br />          this.gender = gender;<br />          this.maritalStatus = maritalStatus;<br />       }
   public String getName() {<br />          return name;<br />       }<br />       public String getGender() {<br />          return gender;<br />       }<br />       public String getMaritalStatus() {<br />          return maritalStatus;<br />       }<br />    }

2. 为标准（Criteria）创建一个接口::

   //Criteria.java
   import java.util.List;

   public interface Criteria {
   public List meetCriteria(List persons);
   }

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<br />       public List<Person> meetCriteria(List<Person> persons) {<br />          List<Person> malePersons = new ArrayList<Person>();<br />          for (Person person : persons) {<br />             if(person.getGender().equalsIgnoreCase("MALE")){<br />                malePersons.add(person);<br />             }<br />          }<br />          return malePersons;<br />       }<br />    }
   

   //CriteriaFemale.java
   import java.util.ArrayList;
   import java.util.List;

   public class CriteriaFemale implements Criteria {

   @Override<br />       public List<Person> meetCriteria(List<Person> persons) {<br />          List<Person> femalePersons = new ArrayList<Person>();<br />          for (Person person : persons) {<br />             if(person.getGender().equalsIgnoreCase("FEMALE")){<br />                femalePersons.add(person);<br />             }<br />          }<br />          return femalePersons;<br />       }<br />    }
   

   //CriteriaSingle.java
   import java.util.ArrayList;
   import java.util.List;

   public class CriteriaSingle implements Criteria {

   @Override<br />       public List<Person> meetCriteria(List<Person> persons) {<br />          List<Person> singlePersons = new ArrayList<Person>();<br />          for (Person person : persons) {<br />             if(person.getMaritalStatus().equalsIgnoreCase("SINGLE")){<br />                singlePersons.add(person);<br />             }<br />          }<br />          return singlePersons;<br />       }<br />    }
   

   //AndCriteria.java
   import java.util.List;

   public class AndCriteria implements Criteria {

   private Criteria criteria;<br />       private Criteria otherCriteria;
   
   public AndCriteria(Criteria criteria, Criteria otherCriteria) {<br />          this.criteria = criteria;<br />          this.otherCriteria = otherCriteria;<br />       }
   
   @Override<br />       public List<Person> meetCriteria(List<Person> persons) {<br />          List<Person> firstCriteriaPersons = criteria.meetCriteria(persons);<br />          return otherCriteria.meetCriteria(firstCriteriaPersons);<br />       }<br />    }
   

   //OrCriteria.java
   import java.util.List;

   public class OrCriteria implements Criteria {

   private Criteria criteria;<br />       private Criteria otherCriteria;
   
   public OrCriteria(Criteria criteria, Criteria otherCriteria) {<br />          this.criteria = criteria;<br />          this.otherCriteria = otherCriteria;<br />       }
   
   @Override<br />       public List<Person> meetCriteria(List<Person> persons) {<br />          List<Person> firstCriteriaItems = criteria.meetCriteria(persons);<br />          List<Person> otherCriteriaItems = otherCriteria.meetCriteria(persons);
   
      for (Person person : otherCriteriaItems) {<br />             if(!firstCriteriaItems.contains(person)){<br />               firstCriteriaItems.add(person);<br />             }<br />          }<br />          return firstCriteriaItems;<br />       }<br />    }
   

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
   import java.util.ArrayList;
   import java.util.List;

   public class CriteriaPatternDemo {
   public static void main(String[] args) {
   List persons = new ArrayList();

      persons.add(new Person("Robert","Male", "Single"));<br />          persons.add(new Person("John","Male", "Married"));<br />          persons.add(new Person("Laura","Female", "Married"));<br />          persons.add(new Person("Diana","Female", "Single"));<br />          persons.add(new Person("Mike","Male", "Single"));<br />          persons.add(new Person("Bobby","Male", "Single"));
   
      Criteria male = new CriteriaMale();<br />          Criteria female = new CriteriaFemale();<br />          Criteria single = new CriteriaSingle();<br />          Criteria singleMale = new AndCriteria(single, male);<br />          Criteria singleOrFemale = new OrCriteria(single, female);
   
      System.out.println("Males: ");<br />          printPersons(male.meetCriteria(persons));
   
      System.out.println("\nFemales: ");<br />          printPersons(female.meetCriteria(persons));
   
      System.out.println("\nSingle Males: ");<br />          printPersons(singleMale.meetCriteria(persons));
   
      System.out.println("\nSingle Or Females: ");<br />          printPersons(singleOrFemale.meetCriteria(persons));<br />       }
   
   public static void printPersons(List<Person> persons){<br />          for (Person person : persons) {<br />             System.out.println("Person : [ Name : " + person.getName()<br />                +", Gender : " + person.getGender()<br />                +", Marital Status : " + person.getMaritalStatus()<br />                +" ]");<br />          }<br />       }<br />    }