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,通过逻辑运算用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。
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public class Person {
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private String name;
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private String gender;
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private String maritalStatus;
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public Person(String name,String gender,String maritalStatus){
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this.name = name;
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this.gender = gender;
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this.maritalStatus = maritalStatus;
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}
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public String getName() {
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return name;
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}
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public String getGender() {
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return gender;
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}
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public String getMaritalStatus() {
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return maritalStatus;
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}
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}
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import java.util.List;
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public interface Criteria {
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public List<Person> meetCriteria(List<Person> persons);
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}
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import java.util.ArrayList;
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import java.util.List;
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public class CriteriaMale implements Criteria {
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@Override
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public List<Person> meetCriteria(List<Person> persons) {
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List<Person> malePersons = new ArrayList<Person>();
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for (Person person : persons) {
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if(person.getGender().equalsIgnoreCase("MALE")){
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malePersons.add(person);
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}
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}
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return malePersons;
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}
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}
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import java.util.ArrayList;
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import java.util.List;
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public class CriteriaFemale implements Criteria {
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@Override
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public List<Person> meetCriteria(List<Person> persons) {
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List<Person> femalePersons = new ArrayList<Person>();
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for (Person person : persons) {
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if(person.getGender().equalsIgnoreCase("FEMALE")){
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femalePersons.add(person);
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}
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}
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return femalePersons;
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}
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}
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import java.util.ArrayList;
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import java.util.List;
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public class CriteriaSingle implements Criteria {
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@Override
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public List<Person> meetCriteria(List<Person> persons) {
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List<Person> singlePersons = new ArrayList<Person>();
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for (Person person : persons) {
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if(person.getMaritalStatus().equalsIgnoreCase("SINGLE")){
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singlePersons.add(person);
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}
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}
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return singlePersons;
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}
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}
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import java.util.List;
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public class AndCriteria implements Criteria {
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private Criteria criteria;
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private Criteria otherCriteria;
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public AndCriteria(Criteria criteria, Criteria otherCriteria) {
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this.criteria = criteria;
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this.otherCriteria = otherCriteria;
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}
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@Override
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public List<Person> meetCriteria(List<Person> persons) {
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List<Person> firstCriteriaPersons = criteria.meetCriteria(persons);
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return otherCriteria.meetCriteria(firstCriteriaPersons);
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}
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}
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import java.util.List;
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public class OrCriteria implements Criteria {
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private Criteria criteria;
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private Criteria otherCriteria;
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public OrCriteria(Criteria criteria, Criteria otherCriteria) {
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this.criteria = criteria;
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this.otherCriteria = otherCriteria;
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}
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@Override
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public List<Person> meetCriteria(List<Person> persons) {
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List<Person> firstCriteriaItems = criteria.meetCriteria(persons);
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List<Person> otherCriteriaItems = otherCriteria.meetCriteria(persons);
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for (Person person : otherCriteriaItems) {
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if(!firstCriteriaItems.contains(person)){
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firstCriteriaItems.add(person);
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}
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}
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return firstCriteriaItems;
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}
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}
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import java.util.ArrayList;
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import java.util.List;
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public class CriteriaPatternDemo {
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public static void main(String[] args) {
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List<Person> persons = new ArrayList<Person>();
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persons.add(new Person("Robert","Male", "Single"));
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persons.add(new Person("John","Male", "Married"));
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persons.add(new Person("Laura","Female", "Married"));
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persons.add(new Person("Diana","Female", "Single"));
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persons.add(new Person("Mike","Male", "Single"));
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persons.add(new Person("Bobby","Male", "Single"));
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Criteria male = new CriteriaMale();
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Criteria female = new CriteriaFemale();
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Criteria single = new CriteriaSingle();
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Criteria singleMale = new AndCriteria(single, male);
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Criteria singleOrFemale = new OrCriteria(single, female);
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System.out.println("Males: ");
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printPersons(male.meetCriteria(persons));
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System.out.println("\nFemales: ");
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printPersons(female.meetCriteria(persons));
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System.out.println("\nSingle Males: ");
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printPersons(singleMale.meetCriteria(persons));
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System.out.println("\nSingle Or Females: ");
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printPersons(singleOrFemale.meetCriteria(persons));
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}
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public static void printPersons(List<Person> persons){
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for (Person person : persons) {
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System.out.println("Person : [ Name : " + person.getName()
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+", Gender : " + person.getGender()
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+", Marital Status : " + person.getMaritalStatus()
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+" ]");
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}
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}
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}
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