过滤器模式（Filter Pattern）

过滤器模式

一、什么是过滤器模式

  过滤器模式（Filter Pattern），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。

二、具体实现

1、主要角色

过滤对象：需要过滤的对象。

过滤条件接口：抽象过滤条件的接口。

具体的过滤条件：根据需要实现过滤条件接口的具体过滤条件。

2、代码实现

1、需要过滤的对象

package com.designpattern.filterPattern;

/**
 * 过滤的对象
 *
 * @author zhongtao on 2018/12/12
 */
public class Person {

    private String name;
    private String gender;  //性别
    private int age;

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getGender() {
        return gender;
    }

    public void setGender(String gender) {
        this.gender = gender;
    }

    public int getAge() {
        return age;
    }

    public void setAge(int age) {
        this.age = age;
    }

    public Person(String name, String gender, int age) {
        this.name = name;
        this.gender = gender;
        this.age = age;
    }

    public Person() {
    }

    @Override
    public String toString() {
        return "Person{" +
                "name='" + name + '\'' +
                ", gender='" + gender + '\'' +
                ", age=" + age +
                '}';
    }
}

2、过滤条件接口

package com.designpattern.filterPattern;

import java.util.List;

/**
 * 过滤条件接口
 *
 * @author zhongtao on 2018/12/12
 */
public interface FilterCriteria {

    List<Person> filterCriteria(List<Person> persons);
}

3、具体过滤条件 实现过滤条件接口

package com.designpattern.filterPattern;

import java.util.List;
import java.util.Objects;
import java.util.stream.Collectors;

/**
 * 过滤男性
 *
 * @author zhongtao on 2018/12/12
 */
public class MaleFilter implements FilterCriteria {
    @Override
    public List<Person> filterCriteria(List<Person> persons) {
        //通过流来处理
        return persons.stream().filter(person -> Objects.equals(person.getGender(), "MALE")).collect(Collectors.toList());
    }
}

package com.designpattern.filterPattern;

import java.util.List;
import java.util.stream.Collectors;

/**
 * 年龄大于20
 *
 * @author zhongtao on 2018/12/12
 */
public class AgeGreaterThan20Filter implements FilterCriteria {
    @Override
    public List<Person> filterCriteria(List<Person> persons) {
        return persons.stream().filter(person -> person.getAge() > 20).collect(Collectors.toList());
    }
}

package com.designpattern.filterPattern;

import java.util.List;
import java.util.Objects;
import java.util.stream.Collectors;

/**
 * 过滤男性并且年龄大于20
 *
 * @author zhongtao on 2018/12/12
 */
public class MaleAndAgeGreaterThan20Filter implements FilterCriteria {
    @Override
    public List<Person> filterCriteria(List<Person> persons) {
        return persons.stream().filter(person -> Objects.equals(person.getGender(), "MALE"))
                .filter(person -> person.getAge() > 20)
                .collect(Collectors.toList());
    }
}

4、测试过滤器模式

package com.designpattern.filterPattern;

import org.junit.Test;

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

/**
 * @author zhongtao on 2018/12/12
 */
public class FilterPatternTest {

    /**
     * 测试过滤器模式
     */
    @Test
    public void testFilterPattern() {
        List<Person> persons = new ArrayList<>();

        persons.add(new Person("Peter", "MALE", 24));
        persons.add(new Person("Mary", "FEMALE", 22));
        persons.add(new Person("Bob", "MALE", 18));
        persons.add(new Person("Lina", "FEMALE", 20));
        persons.add(new Person("Luna", "FEMALE", 21));

        FilterCriteria maleFilter = new MaleFilter();
        List<Person> males = maleFilter.filterCriteria(persons);
        System.out.println("男的：" + males);

        FilterCriteria ageGreaterThan20 = new AgeGreaterThan20Filter();
        List<Person> ageThan20 = ageGreaterThan20.filterCriteria(persons);
        System.out.println("年龄大于20的人：" + ageThan20);

        FilterCriteria maleAndAgeGreaterThan20 = new MaleAndAgeGreaterThan20Filter();
        List<Person> personList = maleAndAgeGreaterThan20.filterCriteria(persons);
        System.out.println("男的且年龄大于20的人：" + personList);
    }
}

5、测试结果

男的：[Person{name='Peter', gender='MALE', age=24}, Person{name='Bob', gender='MALE', age=18}]
年龄大于20的人：[Person{name='Peter', gender='MALE', age=24}, Person{name='Mary', gender='FEMALE', age=22}, Person{name='Luna', gender='FEMALE', age=21}]
男的且年龄大于20的人：[Person{name='Peter', gender='MALE', age=24}]

源码地址：https://github.com/zt19994/designPattern