tiennm99/java-design-patterns
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Ilkka Seppälä committed 2024-05-27 10:04:48 +03:00
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@@ -48,22 +48,17 @@ public class Person {
private String surname; private String surname;
private int age; private int age;
/**
* Constructor.
*/
public Person(String name, String surname, int age) { public Person(String name, String surname, int age) {
this.name = name; this.name = name;
this.surname = surname; this.surname = surname;
this.age = age; this.age = age;
} }
} }
``` ```
We are using Spring Data to create the `PersonRepository` so it becomes really simple. We are using Spring Data to create the `PersonRepository`, so it becomes really simple.
```java ```java
@Repository @Repository
public interface PersonRepository extends CrudRepository<Person, Long>, JpaSpecificationExecutor<Person> { public interface PersonRepository extends CrudRepository<Person, Long>, JpaSpecificationExecutor<Person> {
Person findByName(String name); Person findByName(String name);
@@ -78,7 +73,6 @@ public class PersonSpecifications {
public static class AgeBetweenSpec implements Specification<Person> { public static class AgeBetweenSpec implements Specification<Person> {
private final int from; private final int from;
private final int to; private final int to;
public AgeBetweenSpec(int from, int to) { public AgeBetweenSpec(int from, int to) {
@@ -110,65 +104,88 @@ public class PersonSpecifications {
And here's the repository example in action. And here's the repository example in action.
```java ```java
var peter = new Person("Peter", "Sagan", 17); public static void main(String[] args) {
var nasta = new Person("Nasta", "Kuzminova", 25);
var john = new Person("John", "lawrence", 35);
var terry = new Person("Terry", "Law", 36);
repository.save(peter); var context = new ClassPathXmlApplicationContext("applicationContext.xml");
repository.save(nasta); var repository = context.getBean(PersonRepository.class);
repository.save(john);
repository.save(terry);
LOGGER.info("Count Person records: {}",repository.count()); var peter = new Person("Peter", "Sagan", 17);
var nasta = new Person("Nasta", "Kuzminova", 25);
var john = new Person("John", "lawrence", 35);
var terry = new Person("Terry", "Law", 36);
var persons = (List<Person>) repository.findAll(); // Add new Person records
persons.stream().map(Person::toString).forEach(LOGGER::info); repository.save(peter);
repository.save(nasta);
repository.save(john);
repository.save(terry);
nasta.setName("Barbora"); // Count Person records
nasta.setSurname("Spotakova"); LOGGER.info("Count Person records: {}", repository.count());
repository.save(nasta);
repository.findById(2L).ifPresent(p ->LOGGER.info("Find by id 2: {}",p));
repository.deleteById(2L); // Print all records
LOGGER.info("Count Person records: {}",repository.count()); var persons = (List<Person>) repository.findAll();
persons.stream().map(Person::toString).forEach(LOGGER::info);
repository.findOne(new PersonSpecifications.NameEqualSpec("John")).ifPresent(p ->LOGGER.info("Find by John is {}",p)); // Update Person
nasta.setName("Barbora");
nasta.setSurname("Spotakova");
repository.save(nasta);
persons = repository.findAll(new PersonSpecifications.AgeBetweenSpec(20, 40)); repository.findById(2L).ifPresent(p -> LOGGER.info("Find by id 2: {}", p));
LOGGER.info("Find Person with age between 20,40: ");
persons.stream().map(Person::toString).forEach(LOGGER::info); // Remove record from Person
repository.deleteById(2L);
repository.deleteAll(); // count records
LOGGER.info("Count Person records: {}", repository.count());
// find by name
repository
.findOne(new PersonSpecifications.NameEqualSpec("John"))
.ifPresent(p -> LOGGER.info("Find by John is {}", p));
// find by age
persons = repository.findAll(new PersonSpecifications.AgeBetweenSpec(20, 40));
LOGGER.info("Find Person with age between 20,40: ");
persons.stream().map(Person::toString).forEach(LOGGER::info);
repository.deleteAll();
context.close();
}
``` ```
Program output: Program output:
``` ```
Count Person records: 4 INFO [2024-05-27 07:00:32,847] com.iluwatar.repository.App: Count Person records: 4
Person [id=1, name=Peter, surname=Sagan, age=17] INFO [2024-05-27 07:00:32,859] com.iluwatar.repository.App: Person(id=1, name=Peter, surname=Sagan, age=17)
Person [id=2, name=Nasta, surname=Kuzminova, age=25] INFO [2024-05-27 07:00:32,859] com.iluwatar.repository.App: Person(id=2, name=Nasta, surname=Kuzminova, age=25)
Person [id=3, name=John, surname=lawrence, age=35] INFO [2024-05-27 07:00:32,859] com.iluwatar.repository.App: Person(id=3, name=John, surname=lawrence, age=35)
Person [id=4, name=Terry, surname=Law, age=36] INFO [2024-05-27 07:00:32,859] com.iluwatar.repository.App: Person(id=4, name=Terry, surname=Law, age=36)
Find by id 2: Person [id=2, name=Barbora, surname=Spotakova, age=25] INFO [2024-05-27 07:00:32,869] com.iluwatar.repository.App: Find by id 2: Person(id=2, name=Barbora, surname=Spotakova, age=25)
Count Person records: 3 INFO [2024-05-27 07:00:32,873] com.iluwatar.repository.App: Count Person records: 3
Find by John is Person [id=3, name=John, surname=lawrence, age=35] INFO [2024-05-27 07:00:32,878] com.iluwatar.repository.App: Find by John is Person(id=3, name=John, surname=lawrence, age=35)
Find Person with age between 20,40: INFO [2024-05-27 07:00:32,881] com.iluwatar.repository.App: Find Person with age between 20,40:
Person [id=3, name=John, surname=lawrence, age=35] INFO [2024-05-27 07:00:32,881] com.iluwatar.repository.App: Person(id=3, name=John, surname=lawrence, age=35)
Person [id=4, name=Terry, surname=Law, age=36] INFO [2024-05-27 07:00:32,881] com.iluwatar.repository.App: Person(id=4, name=Terry, surname=Law, age=36)
``` ```
## Class diagram
![Repository](./etc/repository.png "Repository")
## Applicability ## Applicability
* Use when you want to decouple the business logic and data access layers of your application. * Use when you want to decouple the business logic and data access layers of your application.
* Suitable for scenarios where multiple data sources might be used and the business logic should remain unaware of the data source specifics. * Suitable for scenarios where multiple data sources might be used and the business logic should remain unaware of the data source specifics.
* Ideal for testing purposes as it allows the use of mock repositories. * Ideal for testing purposes as it allows the use of mock repositories.
## Tutorials
* [Don’t use DAO, use Repository (Thinking in Objects)](http://thinkinginobjects.com/2012/08/26/dont-use-dao-use-repository/)
* [Advanced Spring Data JPA - Specifications and Querydsl (Spring)](https://spring.io/blog/2011/04/26/advanced-spring-data-jpa-specifications-and-querydsl/)
* [Repository Pattern Benefits and Spring Implementation (Stack Overflow)](https://stackoverflow.com/questions/40068965/repository-pattern-benefits-and-spring-implementation)
* [Design patterns that I often avoid: Repository pattern (InfoWorld)](https://www.infoworld.com/article/3117713/design-patterns-that-i-often-avoid-repository-pattern.html)
## Known Uses ## Known Uses
* Spring Data JPA: Provides a repository abstraction over JPA implementations. * Spring Data JPA: Provides a repository abstraction over JPA implementations.
@@ -196,8 +213,4 @@ Trade-offs:
## Credits ## Credits
* [Domain-Driven Design: Tackling Complexity in the Heart of Software](https://amzn.to/3wlDrze) * [Domain-Driven Design: Tackling Complexity in the Heart of Software](https://amzn.to/3wlDrze)
* [Patterns of Enterprise Application Architecture](https://www.amazon.com/gp/product/0321127420/ref=as_li_tl?ie=UTF8&camp=1789&creative=9325&creativeASIN=0321127420&linkCode=as2&tag=javadesignpat-20&linkId=d9f7d37b032ca6e96253562d075fcc4a) * [Patterns of Enterprise Application Architecture](https://amzn.to/3WfKBPR)
* [Don’t use DAO, use Repository](http://thinkinginobjects.com/2012/08/26/dont-use-dao-use-repository/)
* [Advanced Spring Data JPA - Specifications and Querydsl](https://spring.io/blog/2011/04/26/advanced-spring-data-jpa-specifications-and-querydsl/)
* [Repository Pattern Benefits and Spring Implementation](https://stackoverflow.com/questions/40068965/repository-pattern-benefits-and-spring-implementation)
* [Design patterns that I often avoid: Repository pattern](https://www.infoworld.com/article/3117713/design-patterns-that-i-often-avoid-repository-pattern.html)