java 过滤器模式(Filter/Criteria Pattern)详细介绍

java 过滤器模式(filter/criteria pattern)

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。

 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

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

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

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

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

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

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

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

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。

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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