Is it possible to use multiple JPA implementations in a Spring Boot project ? For example Hibernate for one data source/database and Eclipse Link for another data source/database. If it is possible then how can we use it.
Using Hibernate I successfully handle multiple data source in a single spring boot project. But I don't know how to use multiple JPA in a project .
Yes It is possible you can implements as many times you want jpa interface
You need to create different repository for each entity and implements the JpaInterface in each repository
for example-:
#Repository
public interface CommentRepository extends JpaRepository<Comment,Long> {
}
NOw to use with different class just replace
1- Comment as that class Name
2- and Long as that class id datatype
Related
In my spring boot project, I am using this starter jpa . i have done all the db related thing in appliction.properties. Project is working fine . I fail to undestand where is this methods defination. We have just defined a abstract method how is this method even working?
public interface UserRepository extends JpaRepository<UserEntity, Integer>{
Optional<UserEntity> getUserByUserName(String user);
}
This is part of the magic of JPA Repositories. I don't actually know the details of how it works either, I just know how to use it.
Ultimately, I think it has to do with how Spring proxies interfaces. Spring will create an instance of an interface at runtime. When the methods are named according to the specs, Spring can generate an appropriate method.
Here is a good article that goes into detail on how you can construct the method names to make the query that you want: https://www.baeldung.com/spring-data-derived-queries.
Currently spring data has multiple db support (mysql, cassandra, mongo.. very big list), however i want to add my custom repository from the scratch like adding custom db support in spring data. I don't want to extend any existing repositories, instead I want to create a parallel repository strutcutre for my custom datasource. Looking at current implementation it looks like tedious task. It would be a great if someone could help me with minimal requirement to do this.
You could create a repository annotated bean where you would inject EntityManager or the proper bean that is acting like that, depending on database type that you are using.
#Repository
public class MyCustomRepositoryImpl implements MyCustomRepository {
#Autowired
private EntityManager entityManager;
//the methods that you are going to create.
}
For more details see:
https://docs.spring.io/spring-data/data-commons/docs/1.6.1.RELEASE/reference/html/repositories.html
Chapter: 1.3 Custom implementations for Spring Data repositories
I'm using Spring Data JPA repositories (like MyRepo extends JpaRepository) and it works without #Repository and without #EnableJpaRepositories annotations. Could someone explain why?
Probably you are using Spring Boot.
Spring Data repositories usually extend from the Repository or CrudRepository interfaces. If you use auto-configuration, repositories are searched from the package containing your main configuration class (the one annotated with #EnableAutoConfiguration or #SpringBootApplication) down.
Please check the Spring Boot Reference Documentation (v2.7.2) for more details.
you don't need #Repository to make use of Spring Data JPA.
The Interface extending the CrudRepository or JPARepository would work even without annotating it with #Repository.
The Core reason why you need to have this annotation in place is it makes unchecked exceptions thrown in the DAO layer eligible to be translated into Spring DataAccessException. Which in turn would be easier to work with. This is the important aspect of using #Repository
More details see this -> https://www.youtube.com/watch?v=z2re1MfWtz0&list=PLO0KWyajXMh4fGMvAw1yQ1x7mWayRcmX3&index=8&t=0s
For more information look into these class which is used to auto-configure Spring Data JPA Repositories:
JpaRepositoriesAutoConfigureRegistrar
Docs : http://www.atetric.com/atetric/javadoc/org.springframework.boot/spring-boot-autoconfigure/1.2.0.RELEASE/org/springframework/boot/autoconfigure/data/jpa/JpaRepositoriesAutoConfigureRegistrar.html
#EnableJpaRepositories
private static class EnableJpaRepositoriesConfiguration {
}
I am very new to spring and mongo db.Please suggest the way for my problem: I have this web app written in Spring boot and it mainly uses JPA for database. I have a multiple entity and then I have multiple repositories that extends JPARepository with some methods that fetch data from the database.
But now I need to have a second database and it must be MongoDB. Everything is identical to the JPA, but now I have a new repository class, that this time extends MongoRepository.
public interface CustomerRepository extends CrudRepository<Customer, Long> {
List<Customer> findByLastName(String lastName);
}
public interface CustomerRepositoryMongo extends MongoRepository<Customer, Long> {
List<Customer> findByLastName(String lastName);
}
So now I have two classes, CustomerRepository and CustomerRepositoryMongo.
1.First of all what all changes i have to made to run it in a mongodb inside the eclipse Ide and how can i configure mongodb inside eclipse IDE.?
2.How can i easily switch between two dbs,how to specify which repository to used?
3.I have no idea how can i achieve this also i can not have both the interfaces with the same name.
4.I have tried the jpa approach with #profile annotation,its working fine..but to use the mongodb ,i have to create the collection for all the entities which has #table ,#entity annotation.So shall i use #document annotation as well to specify the collection name because i am using the different names in my queries.
My application is based on Spring Boot, Hibernate, MySQL using Spring Data JPA to stitch them.
Use case is to use slave db node for doing heavy read operations so as to avoid all traffic being served from master mysql node. One way of achieving this is to have multiple Entity Managers pointing to separate data sources(one to master and other to slave node). This way has been explained quite well in below SO questions and blogs.
Spring Boot, Spring Data JPA with multiple DataSources
https://scattercode.co.uk/2016/01/05/multiple-databases-with-spring-boot-and-spring-data-jpa/
Where I am stuck is to understand if there is a way I can inject different entity managers for different use cases in my Repository Annotated Interface.
The only way I see it can be done is extending repository with a custom implementation which gives uses custom entity manager annotated with relevant persistenceContext like below.
public interface CustomerRepository extends JpaRepository<Customer, Integer>, MyCustomCustomerRepository{
}
public class MyCustomCustomerRepositoryImpl implements MyCustomCustomerRepository {
#PersistenceContext(unitName = "entityManagerFactoryTwo")
EntityManager entityManager;
}
I would like to avoid doing this custom implementation. Any help around solving this use case(which I feel should be very common) would be appreciated.
NOTE: Entities are same in both databases so giving separate packages for entity scanning and similar solutions might not work.
Here is a nice sample you can use:
dynamic-datasource-routing-with-spring.
Inside you can find an AbstractRoutingDatasource + an interceptor for a custom annotation that wires the service method to a required database.
However you can just use datasource switch explicitly.
Below is the pull request that shows the diff and how I made it work with most configurations annotation driven instead of xml. It is based on cra6's answer above. i.e. using spring's RoutingDataSource capability.
https://github.com/himanshuvirmani/rest-webservice-sample/pull/1/files