代码详解设计模式--过滤器模式_不同的标准过滤一组对象

过滤器模式

  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。最常见的应用如MyBatis中。

// 实体
@Data
@AllArgsConstructor
public class Person {
   private String name;
   private String gender;
   private String maritalStatus;
}

// 条件接口
public interface Criteria {
   public List<Person> filter(List<Person> persons);
}

// 男性条件
public class MaleCriteria 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;
   }
}

// 女性条件
public class FemaleCriteria 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;
   }
}

// 单身条件
public class SingleCriteria implements Criteria {
   @Override
   public List<Person> filter(List<Person> persons) {
      List<Person> singlePersons = new ArrayList<Person>(); 
      for (Person person : persons) {
         if(person.getMaritalStatus().equalsIgnoreCase("SINGLE")){
            singlePersons.add(person);
         }
      }
      return singlePersons;
   }
}

// 与条件
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);
   }
}

// 或条件
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;
   }
}

// 使用示例
public class Demo {
   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 MaleCriteria();
      Criteria female = new FemaleCriteria();
      Criteria single = new SingleCriteria();
      Criteria singleMale = new AndCriteria(single, male);
      Criteria singleOrFemale = new OrCriteria(single, female);
 
      System.out.println("Males: ");
      printPersons(male.filter(persons));
 
      System.out.println("Females: ");
      printPersons(female.filter(persons));
 
      System.out.println("Single Males: ");
      printPersons(singleMale.filter(persons));
 
      System.out.println("Single Or Females: ");
      printPersons(singleOrFemale.filter(persons));
   }
 
   public static void printPersons(List<Person> persons){
      for (Person person : persons) {
         System.out.println(person.toString());
      }
   }      
}
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133