Java设计模-过滤器模式

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

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

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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

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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

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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

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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

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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

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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

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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

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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。

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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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