I am new to spring roo, and now, I am building a small project using spring roo 1.2.0.M1, and I fins=d that when I create a jpa repository using repository jpa, I only see the interface has been created, but I cannot find the class which implements that interface.
Another thing is I want to add #PersistenceContext to repository to specify which persistence context it should use. Because I cannot find the implement class, I cannot find out a way to do this.
If someone knows how to do this, please help me!
Thanks in advance!
This sounds like roo uses Spring Data JPA which works exactly that way: you define an interface using fixed name conventions, and at runtime the implementation proxy is generated for you based on the method name and return type (similar to the scaffolding approach of rails / grails).
Here's blog post that explains the mechanism:
GETTING STARTED WITH SPRING DATA JPA
Related
I have the following Spring Data JPA repository:
public interface FooRepository extends PagingAndSortingRepository<Foo, Long> {}
And after migrating to Spring Boot 3, I started getting Error messages for most standard repository methods (e.g. fooRepository.findById(id), fooRepository.save(foo), fooRepository.findAll())
I couldn't find anything related to this in the Spring Boot 3.0 Migration Guide
It seems that Spring Data 3.0 has now separated the "Sorting" repositories from the base ones (i.e. PagingAndSortingRepository and other interfaces don't extend CrudRepository anymore), and so, we have to make our repositories extend more than one framework repo interfaces, combining them as we want to.
A cause for this is that Spring Data JPA has introduced a ListCrudRepository interface now that retrieves List results instead of Iterable as the CrudRepository did (which in many cases was a pain to deal with).
So, with this unbinding, we can now choose to combine PagingAndSortingRepository with CrudRepository as was the previous behavior, or instead use it with ListCrudRepository.
All this is explained in this Spring Data Announcement post, and also in the Spring Data 3.0 docs:
Note that the various sorting repositories no longer extended their respective CRUD repository as they did in Spring Data Versions pre 3.0. Therefore, you need to extend both interfaces if you want functionality of both.
the question is simple, but I can't find any of answer about this.
After searching, I realize that kotlin data class is not suitable for Spring JPA because data class is immutable and does not support inheritance.
So, I wonder are there any alternatives for JPA which support data class.
Thanks,
I find two kotlin-based ORM, ktorm and exposed.
It seems both are very good for start, and it supports data class.
But, at some point, I thought that I need to move to ktor rather than Spring boot when I wanna use kotlin more kotlin-tic way..
I started to read this tutorial: spring boot tutorial
In this I read that under model module they implemented POJOs and Repository interfaces. -> tutorial on github
In Repository interfaces I found two methods without implementations:
findByUsername,
findByAccountUsername.
My questions are:
How does it work when those methods in repository interfaces have no
implementations and those are not inherited from any super class?
Does it work with name conventions and reflections?
Does Spring Data has inmemory database to work with?
(1) How does it work when those methods in repository interfaces have
no implementations and those are not inherited from any super class?
The Repository interfaces are being implemented (backed up) by Spring Container at Runtime.
(2) Does it work with name conventions and reflections?
Yes, it works on naming conventions and spring container uses JDK's proxy classes to intercept the calls to the Repository.
(3) Does Spring Data has inmemory database to work with?
No, Spring does not use any inmemory database
Please refer the below link for more detailed explanation:
How are Spring Data repositories actually implemented?
For your question 1 and 2, they are right. They use naming convention and reflection. If you don't want to use their naming convention, you can use #Query with HQL, and certainly the hidden class (which implements for your interface) will handle these query also (you don't need to roll the implementation out).
For your last question, as list of IMDB here: https://en.wikipedia.org/wiki/List_of_in-memory_databases , spring data is not supporting for them. You must invoke another Java driver or spring product for each one.
Does anyone know any Java frameworks that follows the repository approach with automatic implementation of query methods (e.g. findByNameAndLastName(…)) but not tied to Spring, only pure JPA. Such feature also exists in GORM. I would like to see if there is any project that can be used in Guice or pure JavaEE environment without bringing Spring as a dependency.
(Disclaimer: I am the author of Spring Data JPA)
There is the CDI Query Module which is very similar to what Spring Data JPA. There's also a DeltaSpike module.
Note that Spring Data JPA ships with a CDI extension that creates repository proxies as plain CDI beans and does not bootstrap a Spring container. There are APIs that allow the creationg of repository proxies programmatically such as:
EntityManager em = // … obtain EntityManager
JpaRepositoryFactory factory = new JpaRepositoryFactory(em);
UserRepository repository = factory.getRepository(UserRepository.class);
Yes, it still requires Spring libraries to be present on the classpath but it is then using them similar to how you would use Commons Collection or the like. We try not to reinvent the wheel and the Spring libraries we depend on provide a lot of useful code that we do not have to re-code.
So if it's Spring as DI container you're worrying about, feel free to give the CDI extension of Spring Data JPA a choice. If you don't want to use any Spring whatsoever (for whatever reason), have a look at the alternatives.
Based on Oliver's information, followed up as also interested in this topic --
CDI Query joining Deltaspike mail thread: http://apache-deltaspike-incubator-discussions.2316169.n4.nabble.com/Porting-the-CDI-Query-extension-project-to-DeltaSpike-td4329922.html
Deltaspike base link: http://deltaspike.apache.org/index.html
Getting started: http://deltaspike.apache.org/documentation.html
Just did their 0.4th release as of 5/31/2013.
However, have not done enough of a review to contrast/compare Deltaspike versus Spring-Data w/ CDI extensions (spring-data being very mature).
Take a look at Tomato on github!
It is a functional replacement for Spring JPA, has zero dependencies, performs better and is far easier to use. It will reduce your data access code by 98% and deliver the results you want right out of the box.
https://rpbarbati.github.io/Tomato.
If you want free, fully functional dynamic forms and/or tables for any Tomato entity or hierarchy, that can also be customized easily, try the angular based companion project...
https://rpbarbati.github.io/Basil
Both are current, maintained projects.
Try it yourself, or contact the author at rodney.barbati#gmail.com with questions.
I want to create a new application in Spring MVC, before start it, I want to learn how to use Spring MVC with annotations and JDBC template. I search many blogs and tutorials about that, but they are pretty much confusing as well.
Hopefully somebody could give me a good link where I could learn step by step for the annotation driven spring mvc application.
Have a look at following series:
Barebones Spring MVC
Articles about writing sample Spring Finance Manager
Both have a git/svn repositories with working and complete code, so if you can't find something in article you may read the code :-)
Also I can't see any problems with using JDBC templates: it's just a way how you are implementing your DAO and nothing more. All other code interacts with DAO by interface and know nothing about implementation.
Very helpfull for me is to separate code to different layers which of them interacts between each other, like in this picture:
(image stolen from http://www.captaindebug.com)
Spring provides even special annotations to allow grouping classes to layers. They are: #Controller for controllers, #Service for classes with business logic and #Repository for marking your DAOs.