I wanted to read and write data from underlying db with Apache ignite . I'm doing a spring boot app so i just want to know whether i can use JPA features for it ?
As far as my understanding goes, Apache Ignite does not implement any JPA APIs. So you can't access data stored in Ignite in JPA fashion.
However, you can probably use JPA to cache data in Ignite while writing it to, and reading from, underlying JPA store. In this case you will need to implement your own CacheStore. Example: https://github.com/gridgain/gridgain-advanced-examples/tree/master/src/main/java/org/gridgain/examples/datagrid/store (this is based on Mongo but you can rewrite it to use JPA).
Related
In My Application, Using the below technologies
Spring boot 2.7.x
Cassandra
spring batch 5. x
java 11
As part of this, I need to extract data from the Cassandra database and need to write out the file
so here I need to use queries to fetch data so
just want to know what is the best way to maintain all queries at one place so any query changes come in the future, I shouldn't build the app rather just need to modify the query.
Using a repository class is necessary. If you are using JPA i recommend using a repository for each Entity class. With JDBC it is possible to create a single repository which contains all the queries. To access the query methodes i would use a service class. In this way your code is structured well and maintainable for future changes.
I created user in oracle database and I am trying to create session but I find many ways in spring boot so what is the easy way if I want to create classe connections using the Username and Password ?
You can jdbc template, spring data JDBC or spring data JPA, well depending on your use case.
If your data model is quite complex, you should avoid using the JDBC template as you will need to write prepared statements which can be cumbersome. JPA will allow you to use object-oriented programming principles and also will help you map the entities to your database columns.
For example, if you are going to use spring data JPA, you need to set the application properties as follows:
spring.datasource.type=oracle.oracleucp.jdbc.UCPDataSource
spring.datasource.oracleucp.connection-factory-class-name=oracle.jdbc.pool.OracleDataSource
spring.datasource.oracleucp.sql-for-validate-connection=select * from dual
spring.datasource.oracleucp.connection-pool-name=UcpPoolBooks
spring.datasource.oracleucp.initial-pool-size=5
spring.datasource.oracleucp.min-pool-size=5
spring.datasource.oracleucp.max-pool-size=10
This would behind the scene create an Oracle Datasource. In this example, we are using Oracle Universal Connection Pooling. You can also use HikariCP which is quite popular.
check this out
If you want to use UCP with above properties then you must have SpringBoot version higher than 2.4.0.
Check out the Spring Boot code sample on GitHub.
Is it possible to use Hibernate and RDBMS(Mysql, Postgres etc) with ReactiveCrudRepository instead of CrudRepository? I have tried some samples with Spring Data Jpa and Hibernate, but couldn't get it done. I was only able to find a few samples on ReactiveCrudRepository for MongoDB and cassandra.
Is it possible to use Hibernate and Mysql with ReactiveCrudRepository instead of CrudRepository?
TL;DR:
Not with Hibernate and MySQL, but with R2DBC and Postgres, Microsoft SQL Server or H2.
Take a look at Spring Data R2DBC.
Long Version
Why not JPA?
With Hibernate/JPA included this won't happen in the foreseeable future.
JPA is based on the idea that you load part of your data model into memory, manipulate the resulting object model and let JPA transform these changes.
All this within a single transaction.
This is kind of the opposite how one deals with a reactive store where you try to make atomic changes and try to decouple the loading, processing and storing and all this without blocking.
Why not JDBC?
So we have to look at the technology level below JPA: JDBC.
But JDBC is still blocking: You send a SQL statement to your database and then JDBC will block until you get the result.
And again this goes against the idea of reactive: Never block.
One could wrap this in a thread pool to mitigate this to some extent, but that is more of a workaround than a solution.
Why R2DBC?
There are some suitable drivers for some databases that could be used for reactive repositories.
But they are proprietary and thereby not a good basis for something that really should eventually work across all (relevant) relational databases.
For some time the Spring Data team hoped that ADBA would fill that gap.
But discussions on the mailing list made it clear that ADBA was not aiming for reactive but only for asynchronous.
Again not what we needed for a reactive repository abstraction.
So early in 2018 various people living at the intersection or reactive and relational decided that we need a standard for reactive database access.
R2DBC (Reactive Relational Database Connectivity)
is a proposal for such a standard.
The hope is that it either helps convincing Oracle to move ADBA to a reactive approach or if that doesn't happen it becomes the standard itself.
And with already three implementations available chances for the second option look promising.
R2DBC itself is mainly an SPI, i.e. an API that is to be implemented by database providers.
The SPI is designed in a way that puts minimal requirements on implementers.
But this also makes R2DBC somewhat cumbersome to use.
The idea is that other libraries will step up and build libraries designed for usability on top of that SPI, as it happened with JDBC.
Spring Data R2DBC
Spring Data R2DBC is one such library and it offers what you asked for: Support for ReactiveCrudRepository although it is independent of JPA/Hibernate and there is no support for MySQL yet.
State of the projects
Both R2DBC and Spring Data R2DBC didn't have a production release yet and it will take at least several months to get there.
Spring Data R2DBC just released the first milestone.
See the release article for its current capabilities.
R2DBC is on its 6th milestone. See the release article for details.
See also this answer: Why does Spring not provide reactive (non-blocking) clients for relational databases?
Original answer as a reference for archeologists:
As of now (Jan 2017) it is not possible.
The currently relevant release for the reactive part of Spring Data is Spring Data Kay M1 (You can check if there is a newer version available on the project home page)
And a blog post from the Spring Data team about that release and specifically the reactive parts in it starts with (emphasis mine):
Spring Data Kay M1 is the first release ever that comes with support for reactive data access. Its initial set of supported stores — MongoDB, Apache Cassandra, and Redis — all ship reactive drivers already, which made them very natural candidates for such a prototype.
The reason is that there is no standard non-blocking way to access a relational database. So only those that support this kind of API are supported right now.
One could implement a ReactiveCrudRepository using JPA or JDBC and delegate the work to a thread pool. This would provide an async API on the outside, but would still consume the resources for the Threads and block between independent data accesses, so only a small part of the benefits of the reactive approach would get realized.
Hibernate started a new Hibernate Reactive subproject for reactive streams support which provides Hibernate/JPA similar APIs to access RDBMS. But unfortunately at the moment, Spring Data does not support it. So there is no a ReactiveCrudRepoisoty for Hibernate Reactive.
But you can integrate Hibernate with Spring yourself and get reactive support.
Define a persistence.xml file, note the provider class must be specified as the one in Hibernate Reactive.
Declare a Mutiny.SessionFactory bean.
Then inject it in your repository class.
I have created a complete example demos Hibernate Reactive + Spring.
Update: Till now Spring team has no plan to support it, if you are willing to taste other framework, check Quarkus and Micronaunt, both have seamless Hibernate Reactive support. Check my Quarkus Hibernate Reactive example and Micronaut Hibernate Reactive example.
According to quote from previous answer
One could implement a ReactiveCrudRepository using JPA or JDBC and delegating the work to a thread pool. This would provide an async API on the outside, but would still consume the resources for the Threads and block between independent data accesses, so only a small part of the benefits of the reactive approach would get realized.
James Ward claims it can be non-blocking. I mean I asked him:
yeah ok, but isn't ScalikeJDBC-Async doing exactly the same? just putting query invocation into another thread pool?
and he replied
No because ScalalikeJDBC-Async uses https://github.com/mauricio... which is actually a non-blocking (NIO) JDBCish database driver.
source
So you can be reactive by replacing hibernate + spring data with postgresql-async (should work with mysql).
you could try with quarkus framework and panache mongo hibernate reactive repositories. https://quarkus.io/guides/mongodb-panache .It is easy manage a reactive repository over mongoDB, It is later but hope helps.
I want to access a Neo4j DB with Java and wanted to know what the preferred way to do this is. I just want to write a quite simple data structure to the DB.
http://neo4j.com/developer/java/ gives following options:
JDBC
Hibernate OGM
Spring Data
Rest API via Unmanaged Extensions
I looked into accessing Neo4J with JDBC and Hibernate OGM. It seems that its not worth it to use for me. JDBC gives me some trouble. So should i go with the REST way or try to fix my JDBC problems?
The JDBC driver is really a wrapper around the REST interface (as of neo4j 2.3). There is a example application how to use it. Should suffice for very simple use.
Then there is neo4j-ogm (different from Hibernate OGM) - this is an object graph mapping library, similar to hibernate in ORM world. This has minimal external dependencies and is very easy to use - ideal for cases where you want to map couple of objects into graph.
Then there is the Spring Data Neo4j project, which since version 4 uses neo4j-ogm for mapping, but adds other Spring data features, like repositories, derived finder queries, transactions ...
I am working on spring batchupdate ,I search on google I didn't find any solution for my problem.
I have two databases(MySQL,ORALCE) I want to read data from mysql and write into oracle by using batch update .
Your problem is unclear.
You can first read the data from MySQL with one Spring JdbcTemplate object initialized with MySql data source, and then use another JdbcTemplate object, initialized with Oracle data source, to write the data.
If you want to do it in one transaction, you will have to use distributed transactions/XA libraries, such as Atomicos, and Spring distributed transaction manager. See here https://docs.spring.io/spring-boot/docs/current/reference/html/boot-features-jta.html for details on Spring integration with distributed transactions libraries.