Java Filter Pattern(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。

1. 创建一个类，在该类上应用标准。

/**
 * 1. 创建一个类，在该类上应用标准。
 * @author mazaiting
 */
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;
    }   
}

1. 为标准（Criteria）创建一个接口。

/**
 * 2. 为标准（Criteria）创建一个接口
 * @author mazaiting
 */
public interface Critertia {
    /**男性*/
    public static final String MALE = "MALE";
    /**女性*/
    public static final String FEMALE = "FEMALE";
    /**单身*/
    public static final String SINGLE = "SINGLE";
    
    /**
     * 获取指定的人群
     * @param persons
     */
    public List<Person> meetCriteria(List<Person> persons);
}

1. 创建实现了 Criteria 接口的实体类。

/**
 * 3. 创建实现了 Criteria 接口的实体类--过滤男性。
 * @author mazaiting
 */
public class CriteriaMale implements Critertia{

    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;
    }

}

/**
 * 3. 创建实现了 Criteria 接口的实体类。--过滤女性
 * @author mazaiting
 */
public class CriteriaFemale implements Critertia{

    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;
    }

}

/**
 * 3. 创建实现了 Criteria 接口的实体类。--过滤单身
 * @author mazaiting
 */
public class CriteriaSingle implements Critertia{

    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;
    }

}

/**
 * 3. 创建实现了 Criteria 接口的实体类。--双重过滤
 * @author mazaiting
 */
public class AndCriteria implements Critertia{

    private Critertia critertia;
    private Critertia otherCritertia;
    
    public AndCriteria(Critertia critertia, Critertia otherCriteria) {
        this.critertia = critertia;
        this.otherCritertia = otherCriteria;
    }
    
    public List<Person> meetCriteria(List<Person> persons) {
        List<Person> firstCriteriaPersons = critertia.meetCriteria(persons);
        return otherCritertia.meetCriteria(firstCriteriaPersons);
    }

}

/**
 * 3. 创建实现了 Criteria 接口的实体类。--或过滤
 * @author mazaiting
 */
public class OrCriteria implements Critertia{

    private Critertia critertia;
    private Critertia otherCritertia;
    
    public OrCriteria(Critertia critertia, Critertia otherCritertia) {
        this.critertia = critertia;
        this.otherCritertia = otherCritertia;
    }
    
    public List<Person> meetCriteria(List<Person> persons) {
        List<Person> firstCriteriaItems = critertia.meetCriteria(persons);
        List<Person> otherCriteriaItems = otherCritertia.meetCriteria(persons);
        
        for (Person person : otherCriteriaItems) {
            if (!firstCriteriaItems.contains(person)) {
                firstCriteriaItems.add(person);
            }
        }
        
        return firstCriteriaItems;
    }

}

1. 主函数验证

public class Client {
    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"));
        
        Critertia male = new CriteriaMale();
        Critertia single = new CriteriaSingle();
        Critertia critertia = new AndCriteria(male, single);
        
        List<Person> meetCriteria = critertia.meetCriteria(persons);
        printPersons(meetCriteria);
        
    }
    
    /**
     * 打印数据
     * @param 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()
                +" ]");
          }
       } 
}

1. 打印结果

Person : [ Name : Robert, Gender : Male, Marital Status : Single ]
Person : [ Name : Mike, Gender : Male, Marital Status : Single ]
Person : [ Name : Bobby, Gender : Male, Marital Status : Single ]