过滤模式或标准模式是一种设计模式,使开发人员能够使用不同的标准过滤一组对象,并通过逻辑操作以分离的方式将它们链接起来.这种类型的设计模式属于结构模式,因为此模式结合了多个标准以获得单一标准.
实施
我们将创建一个 Person 对象, Criteria 接口和实现此接口的具体类,用于过滤 Person 对象的列表. CriteriaPatternDemo ,我们的演示类使用 Criteria 对象根据各种标准及其组合过滤 Person 对象列表.
步骤1
创建一个要使用哪个标准的类.
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Criteria创建一个界面.
Criteria.java
import java.util.List;public interface Criteria { public ListmeetCriteria(List persons); }
步骤3
创建实现 Criteria 接口的具体类.
CriteriaMale.java
import java.util.ArrayList;import java.util.List;public class CriteriaMale implements Criteria { @Override public ListmeetCriteria(List persons) { List malePersons = new ArrayList (); 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 ListmeetCriteria(List persons) { List femalePersons = new ArrayList (); 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 ListmeetCriteria(List persons) { List singlePersons = new ArrayList (); 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 ListmeetCriteria(List persons) { List 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 ListmeetCriteria(List persons) { List firstCriteriaItems = criteria.meetCriteria(persons); List otherCriteriaItems = otherCriteria.meetCriteria(persons); for (Person person : otherCriteriaItems) { if(!firstCriteriaItems.contains(person)){ firstCriteriaItems.add(person); } } return firstCriteriaItems; }}
Step4
使用不同的Criteria及其组合来过滤掉人员.
CriteriaPatternDemo.java
import java.util.ArrayList;import java.util.List;public class CriteriaPatternDemo { public static void main(String[] args) { Listpersons = new ArrayList (); 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 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 ]