I am new in Spring data JPA and when I am searching I also read Spring Data JPA #Modifying Annotation and why do we have to use #Modifying annotation for queries in Data Jpa.
After reading the accepted answer on SO page, I am confused. Now, could you pls clarify me about the following issues?
1. Should we still need to use #Modifying Annotation in the last version(s) of Spring Data JPA? If so, could you explain how should I use properly (any annotation for proper usage)?
2. I am also wondering if the similar issue is valid for #Transactional annotation? Should we also need to use it for the create, update and delete methods in Spring Boot service methods? If so, could you also give a proper usage examples for an example scenario?
from what i understand from the references, yes you have to use #Modifying for an Insert/create/delete ddl query. And you have to use #Modifying(clearAutomatically=true, flushAutomatically=true) if you are doing more update/modifying operations before or after another update/modifying operations. In the given SO he clearly stated whats happening if you are not using those two flags.
#Transactional should use for the service method/ business method. if you execute set of selections, updates, deletion in one business logic, those will be grouped and one persistence context will be used for them. so your micro query changes are visible to other micro queries with in the transaction(there can be many micro queries in your business logic code). Even if you use those above flags without using #transaction those changes wont visible to other micro queries as its work in different transaction level and which will fail your business logic .
Related
the Topic already says one of the key roles regarding ORM
Don't run your own ORM Implementation
But, I have a situation here where I'm not sure how to get our Requirements implemented properly.
To give you a bit of background, currently we are using Spring Data JPA with Hibernate as JPA Implementation and all is fine so far.
But we have separate fields which we want to "manage" automatically, a bit similar to Auditing Annotations from Hibernate (#CreatedBy, #ModifiedBy, ...).
In our case this is e.g. a specific "instance" the entity belongs to.
Our Application is rather a Framework than an App, so other Developers frequently add Entities and we want to keep it simple and intuitive.
But, we do not only want to set it automatically on storage but also add it as condition for most "simple and frequent" queries (see my related question here Inject further query conditions / inject automatic entity field values when using Spring Data JPA Repositories).
Thus, I thought about building a simple Layer on top of the EntityManager and its Criteria API to support at least simple Queries like
findById(xx)
findByStringAttribute(String attribute, String value)
findByIntegerAttribute(int attribute, String value)
...
I'm not sure if this is too broad of a question but, what are your thoughts on that? Is this a reasonable idea or should I skip that idea?
I want to learn more about Spring JPA and what happens under the hood when a native JPA query (using PostgreSQL) is defined and called in a Repository class. I have tried searching online but all posts are related to defining and using native queries.
I am more interested to learn about what happens when my SpringBoot application calls a method that is annotated with #Query. I am mainly looking into this to try and understand the performance of executing such a query within Java.
Can anyone point me to a resource which goes in depth on what exactly happens under the hood when using Spring JPA?
Can anyone point me to a resource which goes in depth on what exactly happens under the hood when using Spring [DATA] JPA?
The authoritative source for this kind of information is the source.
Let me point you to some places of interest.
Basically the following happens:
find and extract the query from the annotation.
possibly create a count query from that.
replace spell expression with parameters.
add ordering if applicable.
prepare the query with the EntityManager.
register parameters.
add pagination limits.
execute the query.
transform result.
Output log to view what SQL query really generated and executed
For example, in application.properties:
logging.level.org.springframework.data.jpa=debug
logging.level.org.hibernate=debug
SpringBoot log reference
Check the source code of spring-data-jpa here:
https://github.com/spring-projects/spring-data-jpa/blob/master/src/main/java/org/springframework/data/jpa/repository/query/JpaQueryExecution.java
I am using Spring Data JPA. I am using normalized DB which means, to get a full details of what i want, i have to join many tables. As you know JPA generates method name based on query. But, due to multiple joins, my method name becomes so long. sometimes, its more than 250 chars.
I am looking for #query annotation with JPA methods instead of auto generated JPA method names.
I wanna know the performance implications if i use #query annotation?
Also, please suggest any alternatives to solve my long method names keeping performance into consideration.
Whenever you write your query using Spring Data (i.e List<MyObj> findAllByName(String name)) spring data actually generates your query the same way as you'd write it using #Query annotation. So, technically speaking, boot-up time will be quicker if you write your queries as HQL or JPQL within #Query annotation. The most performant way is of course to use native queries, but it can be a pain in the ass later in the game.
I'm writing a library that wraps the JpaRepository interface of Spring Data Jpa because I want to add the same criteria automatically to all JpaRepository DB calls (something like and where t > something).
For example findById function of JpaRepository under the hood will be translated to find by id and where t > something
Is it possible? and if so, how do I do it?
Thanks!
A long time ago this was planned, but the team came to the conclusion that it really doesn't seem possible to do it properly. So No, the feature does not exist. See here for details: https://jira.spring.io/browse/DATACMNS-293
There is Hibernates #Where and #Filter though.
I want to implement a search function with five optional variables and in every combination, so a switch/case is not a possible way. So i can't use the build in spring boot functions, because they are not dynamic (correct me if i'm wrong).
I know there is the #query annotation in the crudrepository, but there is no way to write a query with optional parameters?
I tried to write my own database access with jpa, without the help of spring boot CrudRepository.
I read in the manual this should work:
#Autowired
#PersistenceContext
private EntityManager em;
#Transactional
public List<Persons>searchPersons(params...){}
But here is the problem, my EntityManager is always null and i have no idea why. I searched some hours and found nothing.
Maybe you guys know a way to write a dynamic SQL query in Spring Boot.
Is there a way in the CrudRepository to define optional parameters for the query?
Btw i use a postgreSQL database.
Many thanks for your help.
You might want to have a look at Specifications.
See the documentation here
For that to work, your repository interface needs to implement JpaSpecificationExecutor.
You can use a custom repository (create your own interface, write one Impl class for it and extend your repository by that interface.
You should then have:
PersonRepositoryCustom
PersonRepositoryCustomImpl
Next, you implement a query, using the EntityManager autowired into your repository. You can do this by using JPQL or the JPA 2.1 Criteria API.
For each parameter, have a condition to add it to the query itself, as well as the prepared statement parameters. That way, you can build a dynamic query.
The following thread is related:
Best way to create JPA query that might contain a parameter or might not
I know this question is old but to anyone coming here interested in implementing dynamic SQL queries, check out these two blog posts, they are great.
Implementing dynamic SQL queries using Spring Data JPA
Specification and Criteria API
Writing dynamic SQL queries using Spring Data JPA repositories and
EntityManager