Java过滤器模式(条件模式)

过滤器模式或条件模式是一种设计模式，使开发人员可以使用不同的条件过滤一组对象，并通过逻辑操作以解耦方式将其链接。 这种类型的设计模式属于结构模式，因为该模式组合多个标准以获得单个标准。

实现实现

我们将创建一个Person对象，Criteria接口和具体类，实现这个接口来过滤Person对象的列表。CriteriaPatternDemo是一个演示类，使用Criteria对象基于各种标准及其组合过滤拥有Person对象的列表（List)。

示例的结构图如下 -

第1步

创建要应用标准的类。

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;   }    }
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第2步

创建Criteria的接口。

Criteria.java

import java.util.List;public interface Criteria {   public List<Person> meetCriteria(List<Person> persons);}
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第3步

创建实现Criteria接口的具体类。

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;   }}
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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;   }}
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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;   }}
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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);   }}
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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;   }}
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第4步

使用不同的条件及其组合过滤掉人。

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() + " ]");      }   }      }
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第5步

验证输出结果，执行上面的代码得到结果如下 -

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 ]