简介
过滤器模式（Filter Pattern）或标准模式（Criteria Pattern），是一种结构型模式。这种模式允许使用不同的标准条件来过滤一组对象，并通过逻辑运算的方式把各条件连接起来，它结合多个标准来获得单一标准。
例子将创建一个 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。Test 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。
作用
- 可以通过层层筛选，过滤出自己想要的结果。
面向接口编程，将对象过滤，接口不依赖对象；对象无入侵，每次只需要增加规则就行了，不用修改过滤对象类。
实现步骤
- 创建Criteria基础接口，定义过滤方法。
创建多个条件类，实现过滤逻辑。
客户端调用时，通条件类过滤数据。
UML
Java代码
标准接口类
// Criteria.java 定义抽象标准接口，聚合实体对象
public interface Criteria {
public List<Person> filter(List<Person> persons);
}
具体标准实现类
// AndCriteria.java 定义And过滤标准
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> filter(List<Person> persons) {
List<Person> firstCriteriaPersons = criteria.filter(persons);
return otherCriteria.filter(firstCriteriaPersons);
}
} // OrCriteria.java 定义Or过滤标准
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> filter(List<Person> persons) {
List<Person> firstCriteriaItems = criteria.filter(persons);
List<Person> otherCriteriaItems = otherCriteria.filter(persons); for (Person person : otherCriteriaItems) {
if (!firstCriteriaItems.contains(person)) {
firstCriteriaItems.add(person);
}
}
return firstCriteriaItems;
}
} // CriteriaFemale.java 根据标准接口实现的过滤
public class CriteriaFemale implements Criteria { @Override
public List<Person> filter(List<Person> persons) {
List<Person> femalePersons = new ArrayList<Person>();
for (Person person : persons) {
if (person.getGender().equalsIgnoreCase("FEMALE")) {
femalePersons.add(person);
}
}
return femalePersons;
}
} // CriteriaMale.java 根据标准接口实现的过滤
public class CriteriaMale implements Criteria { @Override
public List<Person> filter(List<Person> persons) {
List<Person> malePersons = new ArrayList<Person>();
for (Person person : persons) {
if (person.getGender().equalsIgnoreCase("MALE")) {
malePersons.add(person);
}
}
return malePersons;
}
} // CriteriaSingle.java 根据标准接口实现按属性的过滤
public class CriteriaSingle implements Criteria { @Override
public List<Person> filter(List<Person> persons) {
List<Person> singlePersons = new ArrayList<Person>();
for (Person person : persons) {
if (person.getStatus().equalsIgnoreCase("SINGLE")) {
singlePersons.add(person);
}
}
return singlePersons;
}
}
业务实体类
// Person.java 定义一个实体类，用来过滤的对象
public class Person { private String name;
private String gender;
private String status; public Person(String name, String gender, String status) {
this.name = name;
this.gender = gender;
this.status = status;
} public String getName() {
return name;
} public String getGender() {
return gender;
} public String getStatus() {
return status;
} public String toString() {
return "Person : [ Name : " + getName() + ", Gender : "
+ getGender() + ", Marital Status : " + getStatus() + " ]";
}
}
测试调用
/**
* 过滤器模式就是不断组合过滤条件，然后层层过滤的模式
* 这里是简单演示，用List筛选来模拟过滤，实际例子有各种数据结构
*/
List<Person> persons = new ArrayList<Person>(); persons.add(new Person("王男单", "Male", "Single"));
persons.add(new Person("李男婚", "Male", "Married"));
persons.add(new Person("张女婚", "Female", "Married"));
persons.add(new Person("赵女单", "Female", "Single"));
persons.add(new Person("刘男单", "Male", "Single"));
persons.add(new Person("杨男单", "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); // 查询男性
System.out.println("Males: ");
printPersons(male.filter(persons)); // 查询女性
System.out.println("\nFemales: ");
printPersons(female.filter(persons)); // 嵌套查询女性且单身
System.out.println("\nFemales and Single: ");
printPersons(single.filter(female.filter(persons))); // 查询男性男性单身
System.out.println("\nSingle Males: ");
printPersons(singleMale.filter(persons)); // 查询女性或单身
System.out.println("\nSingle Or Females: ");
printPersons(singleOrFemale.filter(persons));
C代码
head文件
// func.h文件
#include <stdio.h>
#include <ctype.h>
#include <stdlib.h>
#include <stdbool.h>
#include <string.h> char *str_toupper(char str[]);
char *str_tolower(char str[]); // 定义用于过滤的Person数组查询对象
// 因C语言无法定义动态数组，将数组长度存在此处
typedef struct FilterPersons
{
int length;
struct Person **persons;
} FilterPersons; // 定义一个实体类，用来过滤的对象
typedef struct Person
{
char name[50];
char gender[20];
char status[20];
char *(*get_name)(struct Person *);
char *(*to_string)(struct Person *);
bool (*is_contained)(struct Person *, struct FilterPersons *);
} Person;
Person *person_constructor(char *name, char *gender, char *status); // 定义抽象标准接口，聚合要过滤的对象集合
typedef struct Criteria
{
struct Criteria *first_criteria;
struct Criteria *other_criteria;
FilterPersons *(*filter)(FilterPersons *, struct Criteria *);
} Criteria; // 根据标准接口实现的过滤
typedef struct CriteriaFemale
{
FilterPersons *(*filter)(FilterPersons *, struct Criteria *);
} CriteriaFemale;
CriteriaFemale *criteria_female_constructor(); // 根据标准接口实现的过滤
typedef struct CriteriaMale
{
FilterPersons *(*filter)(FilterPersons *, struct Criteria *);
} CriteriaMale;
CriteriaMale *criteria_male_constructor(); // 根据标准接口实现的过滤
typedef struct CriteriaSingle
{
FilterPersons *(*filter)(FilterPersons *, struct Criteria *);
} CriteriaSingle;
CriteriaSingle *criteria_single_constructor(); // 定义And过滤标准
typedef struct AndCriteria
{
struct Criteria *first_criteria;
struct Criteria *other_criteria;
FilterPersons *(*filter)(FilterPersons *, struct Criteria *);
} AndCriteria;
AndCriteria *and_criteria_constructor(Criteria *, Criteria *); // 定义Or过滤标准
typedef struct OrCriteria
{
struct Criteria *first_criteria;
struct Criteria *other_criteria;
FilterPersons *(*filter)(FilterPersons *, struct Criteria *);
} OrCriteria;
OrCriteria *or_criteria_constructor(Criteria *, Criteria *);
条件接口类
// criteria.c 定义抽象标准接口，聚合实体对象
#include "func.h"
// c语言没有抽象类或接口，Criterial作为基础struct定义在head， 这里放一些公共函数
char *str_toupper(char str[])
{
int size = strlen(str);
char *result = (char *)malloc(size * sizeof(char));
int i = 0;
while (str[i])
{
result[i] = toupper(str[i]);
i++;
} return result;
} char *str_tolower(char str[])
{
int size = strlen(str);
char *result = (char *)malloc(size * sizeof(char));
int i = 0;
while (str[i])
{
result[i] = tolower(str[i]);
i++;
} return result;
}
具体标准实现类
// and_criteria.c 定义And过滤标准
#include "func.h"
// 先过滤条件1，再把结果按照条件2进行过滤
FilterPersons *and_criteria_filter(FilterPersons *filter, Criteria *criteria)
{
FilterPersons *first_filter = criteria->first_criteria->filter(filter, criteria);
return criteria->other_criteria->filter(first_filter, criteria);
} AndCriteria *and_criteria_constructor(Criteria *first_criteria, Criteria *other_criteria)
{
Criteria *criteria = (Criteria *)malloc(sizeof(Criteria));
criteria->filter = &and_criteria_filter;
AndCriteria *and_criteria = (AndCriteria *)criteria;
and_criteria->first_criteria = first_criteria;
and_criteria->other_criteria = other_criteria;
and_criteria->filter = &and_criteria_filter;
return and_criteria;
} // or_criteria.c 定义Or过滤标准
#include "func.h"
// 先过滤条件1，再把结果按照条件2进行过滤
FilterPersons *or_criteria_filter(FilterPersons *filter, Criteria *criteria)
{
FilterPersons *first_filter = criteria->first_criteria->filter(filter, criteria);
FilterPersons *other_filter = criteria->other_criteria->filter(filter, criteria); int first_size = first_filter->length;
int other_size = other_filter->length; for (int i = 0; i < other_size; i++)
{
Person *person = other_filter->persons[i];
// 符合项如果不存在条件1里，则追加到条件1里去
if (!person->is_contained(person, first_filter))
{
// 这里数组长度直接增加
first_filter->persons[first_size++] = person;
}
} first_filter->length = first_size; return first_filter;
} OrCriteria *or_criteria_constructor(Criteria *first_criteria, Criteria *other_criteria)
{
Criteria *criteria = (Criteria *)malloc(sizeof(Criteria));
criteria->filter = &or_criteria_filter;
OrCriteria *or_criteria = (OrCriteria *)criteria;
or_criteria->first_criteria = first_criteria;
or_criteria->other_criteria = other_criteria;
or_criteria->filter = &or_criteria_filter;
return or_criteria;
} // ccriteria_female.c 根据标准接口实现的过滤
#include "func.h"
// 根据是否女性进行过滤
FilterPersons *criteria_female_filter(FilterPersons *filter, Criteria *criteria)
{
int person_size = filter->length;
int *female_index_list = (int *)malloc(person_size * sizeof(int));
int count = 0;
char *gender;
for (int i = 0; i < person_size; i++)
{
if (filter->persons[i] == NULL)
{
break;
}
gender = str_toupper(filter->persons[i]->gender);
if (strcmp(gender, "FEMALE") == 0)
{
// 记录下所有符合条件的person下标
female_index_list[count] = i;
count += 1;
}
}
free(gender);
free(female_index_list); // 将符合条件的person追加到新数组
Person **female_persons = (Person **)calloc(count, sizeof(Person));
for (int i = 0; i < count; i++)
{
female_persons[i] = filter->persons[female_index_list[i]];
}
FilterPersons *female_filter = (FilterPersons *)calloc(1, sizeof(FilterPersons));
female_filter->length = count;
female_filter->persons = female_persons;
return female_filter;
} CriteriaFemale *criteria_female_constructor()
{
Criteria *criteria = (Criteria *)malloc(sizeof(Criteria));
criteria->filter = &criteria_female_filter;
CriteriaFemale *criteria_female = (CriteriaFemale *)criteria;
criteria_female->filter = &criteria_female_filter;
return criteria_female;
} // criteria_male.c 根据标准接口实现的过滤
#include "func.h" // 根据是否男性进行过滤
FilterPersons *criteria_male_filter(FilterPersons *filter, Criteria *criteria)
{
int person_size = filter->length;
int *male_index_list = (int *)malloc(person_size * sizeof(int));
int count = 0;
char *gender;
for (int i = 0; i < person_size; i++)
{
if (filter->persons[i] == NULL)
{
break;
}
gender = str_tolower(filter->persons[i]->gender);
if (strcmp(gender, "male") == 0)
{
// 记录下所有符合条件的person下标
male_index_list[count] = i;
count += 1;
}
}
free(gender);
free(male_index_list); // 将符合条件的person追加到新数组
Person **male_persons = (Person **)calloc(count, sizeof(Person));
for (int i = 0; i < count; i++)
{
male_persons[i] = filter->persons[male_index_list[i]];
}
FilterPersons *male_filter = (FilterPersons *)calloc(1, sizeof(FilterPersons));
male_filter->length = count;
male_filter->persons = male_persons;
return male_filter;
} CriteriaMale *criteria_male_constructor()
{
Criteria *criteria = (Criteria *)malloc(sizeof(Criteria));
criteria->filter = &criteria_male_filter;
CriteriaMale *criteria_male = (CriteriaMale *)criteria;
criteria_male->filter = &criteria_male_filter;
return criteria_male;
} // criteria_single.c 根据标准接口实现按属性的过滤
#include "func.h" // 根据是否单身进行过滤
FilterPersons *criteria_single_filter(FilterPersons *filter, Criteria *criteria)
{
int person_size = filter->length;
int *single_index_list = (int *)malloc(person_size * sizeof(int));
int count = 0;
char *status;
for (int i = 0; i < person_size; i++)
{
if (filter->persons[i] == NULL)
{
break;
}
status = str_tolower(filter->persons[i]->status);
if (strcmp(status, "single") == 0)
{
// 记录下所有符合条件的person下标
single_index_list[count] = i;
count += 1;
}
}
free(status);
free(single_index_list); // 将符合条件的person追加到新数组
Person **single_persons = (Person **)calloc(count, sizeof(Person));
for (int i = 0; i < count; i++)
{
single_persons[i] = filter->persons[single_index_list[i]];
} FilterPersons *single_filter = (FilterPersons *)calloc(1, sizeof(FilterPersons));
single_filter->length = count;
single_filter->persons = single_persons;
return single_filter;
} CriteriaSingle *criteria_single_constructor()
{
Criteria *criteria = (Criteria *)malloc(sizeof(Criteria));
criteria->filter = &criteria_single_filter;
CriteriaSingle *criteria_single = (CriteriaSingle *)criteria;
criteria_single->filter = &criteria_single_filter;
return criteria_single;
}
业务实体类
// person.c 定义一个实体类，用来过滤的对象
#include "func.h"
// 是否被包含在对象数组中
bool person_is_contained(Person *person, FilterPersons *filter)
{
int persons_size = filter->length;
for (int i = 0; i < persons_size; i++)
{
if (filter->persons[i] == person)
{
return true;
}
}
return false;
} char *person_get_name(Person *person)
{
return person->name;
} // 返回字符串
char *person_to_string(Person *person)
{
char *result = (char *)malloc(500 * sizeof(char));
strcat(result, "Person :[ name :");
strcat(result, person->name);
strcat(result, ", gender : ");
strcat(result, person->gender);
strcat(result, ", status : ");
strcat(result, person->status);
strcat(result, "]");
return result;
} Person *person_constructor(char *name, char *gender, char *status)
{
Person *person = (Person *)malloc(sizeof(Person));
strncpy(person->name, name, 50);
strncpy(person->gender, gender, 20);
strncpy(person->status, status, 20);
person->get_name = &person_get_name;
person->to_string = &person_to_string;
person->is_contained = &person_is_contained;
return person;
}
测试调用
/**
* 过滤器模式就是不断组合过滤条件，然后层层过滤的模式
* 这里是简单演示，用List筛选来模拟过滤，实际例子有各种数据结构。
*/
int data_size = 6;
// 定义一些数据
char data[6][3][100] = {
{"王男单", "Male", "Single"},
{"李男婚", "Male", "Married"},
{"张女婚", "Female", "Married"},
{"赵女单", "Female", "Single"},
{"刘男单", "Male", "Single"},
{"杨男单", "Male", "Single"}};
// 定义persons数组
Person *persons[data_size];
for (int i = 0; i < data_size; i++)
{
char *name = data[i][0];
char *gender = data[i][1];
char *status = data[i][2];
Person *person = person_constructor(name, gender, status);
persons[i] = person;
}
// 构建查询对象
FilterPersons *filter_persons = (FilterPersons *)malloc(sizeof(FilterPersons *));
filter_persons->length = data_size;
filter_persons->persons = persons;
// 声明属性过滤条件，可用Criteria或具体条件声明
Criteria *criteria_male = (Criteria *)criteria_male_constructor();
CriteriaFemale *criteria_female = criteria_female_constructor();
Criteria *criteria_single = (Criteria *)criteria_single_constructor();
// 声明逻辑条件，传入属性过滤条件
Criteria *single_male = (Criteria *)and_criteria_constructor(criteria_single, criteria_male);
OrCriteria *single_or_female = or_criteria_constructor(criteria_single, (Criteria *)criteria_female);
// 查询男性
printf("\n Males: ");
print_persons(((CriteriaMale *)criteria_male)->filter(filter_persons, criteria_male));
// 查询女性
printf("\nFemales: ");
print_persons(criteria_female->filter(filter_persons, (Criteria *)criteria_female));
// 嵌套查询女性且单身
printf("\nFemales and Single: ");
FilterPersons *females = criteria_female->filter(filter_persons, (Criteria *)criteria_female);
print_persons(((CriteriaSingle *)criteria_single)->filter(females, criteria_single));
// 查询男性男性单身
printf("\nSingle Males: ");
// 逐个条件过滤，与下面AndCriteria效果相同
FilterPersons *single_males = ((CriteriaMale *)criteria_male)->filter(filter_persons, criteria_male);
print_persons(((CriteriaSingle *)criteria_single)->filter(single_males, criteria_single));
printf("\nSingle Males: ");
// 通过AndCriteria来过滤
FilterPersons *single_males2 = ((AndCriteria *)single_male)->filter(filter_persons, single_male);
print_persons(single_males2);
// 查询女性或单身
printf("\nSingle Or Females: ");
print_persons(single_or_female->filter(filter_persons, (Criteria *)single_or_female));
free(filter_persons);
free(criteria_male);
free(criteria_female);
free(criteria_single);
free(single_male);
free(single_or_female);
return 0;
更多语言版本
不同语言实现设计模式：https://github.com/microwind/design-pattern
