java 過濾器模式(Filter/Criteria Pattern)詳細介紹

java 過濾器模式(Filter/Criteria Pattern)

過濾器模式（Filter Pattern）或標準模式（Criteria Pattern）是一種設計模式，這種模式允許開發人員使用不同的標準來過濾一組對象，通過邏輯運算以解耦的方式把它們連接起來。這種類型的設計模式屬於結構型模式，它結合多個標準來獲得單一標準。

過濾器模式（Filter Pattern）或標準模式（Criteria Pattern）是一種設計模式，這種模式允許開發人員使用不同的標準來過濾一組對象，通過邏輯運算以解耦的方式把它們連接起來。這種類型的設計模式屬於結構型模式，它結合多個標準來獲得單一標準。

實現

我們將創建一個Person 對象、Criteria 接口和實現了該接口的實體類，來過濾Person 對象的列表。 CriteriaPatternDemo，我們的演示類使用Criteria 對象，基於各種標準和它們的結合來過濾Person 對象的列表。

步驟1

創建一個類，在該類上應用標準。

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; } }

步驟2

為標準（Criteria）創建一個接口。

Criteria.java

 import java.util.List; public interface Criteria { public List<Person> meetCriteria(List<Person> persons);}

步驟3

創建實現了Criteria 接口的實體類。

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; }}

步驟4

使用不同的標準（Criteria）和它們的結合來過濾Person 對象的列表。

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() +" ]"); } } }

步驟5

驗證輸出。

 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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