I created a spring boot project and I link it with my DB under PgAdmin.
I've modified the application.properties correctly and created a class named "user" and its repository "userRepository" but I don't know if this will automaticly create the user table in the DB (I used annotations) or I have to create it in PgAdmin ?
Do I need to specify any controller or webController if I want to have Crud operations ? And where does the CrudRepository exists do I need to generate it and how ?
Excuse me this my first experience with spring, I will really appreciate if you guys can help me.
Thanks in advance.
For your first question:
I don't know if this will automaticly create the user table in the DB
You have several ways how to create your tables, for example with property in application.properties file
spring.jpa.hibernate.ddl-auto = [none|validate|update|create-drop]
where none means this configuration not affect existing database
update means updating changes in database
create-drop means creating all tables from scratch according your project entities classes.
You can check this documentations for additional information
https://docs.spring.io/spring-boot/docs/1.1.0.M1/reference/html/howto-database-initialization.html
59.2 Initialize a database using Hibernate
also you can check how to initialize database with existing sql scripts files in documentation above
59.3 Initialize a database using Spring JDBC
For question: Do I need to specify any controller or webController if I want to have Crud operations ? And where does the CrudRepository exists do I need to generate it and how ?
Yes you should create controllers to handle requests and repositories to work with JPA.I also suggest check tutorial first, for example this one (first in google)
https://bezkoder.com/spring-boot-jpa-crud-rest-api/
Related
I am creating backend for my CRUD application and I have an existing ORACLE DATABASE. I just want to fetch data from it but I 've seen so many tutorials and in every tutorial they are creating new table in the database by using #table annotation which I don't need ? So if anybody knows about this I could use some of his/her help in this problem?
For the database schema management with spring data/hibernate, setting spring.jpa.hibernate.ddl-auto option doesn't look like a cleaner approach.
Bcoz
1) We are forced to put the credentials of a user that has permission to create and delete in the application.properties.
2) In production, relaying on spring.jpa.hibernate.ddl-auto option could lead to dataloss, if not managed carefully.
So what is the best way out there to handle the database schema management automatically in a spring boot/spring data app?
Any pointers would help.
Thanks
If you want to track each change state of database then you can use flyway
See this link how to maintain database versioning in spring-boot
In production, you should ideally set spring.jpa.hibernate.ddl-auto property as none so that no schema changes are allowed.
For the database schema management with spring data/hibernate, I would suggest you go for Liquibase, it basically is an open source database-independent library for tracking, managing and applying database schema changes.
Every change to Schema is added as a changeset using property file in Liquibase , this is for the new changes.
In order to migrate the existing database structure into Liquibase, it provides you with commands to automatically generate Changesets by reading the current database.
So using this you can generate database schema, add constraints, load data.
More info at : https://www.liquibase.org/ , Why and when Liquibase?
I would like to use liquibase in my spring boot app. My requirement is that I have a dummy schema which is populated with tables every time I change the entity classes. This is done by hibernate's ddl create. There are many identical schemas to the dummy schema with data. I want those schemas to be compared with the dummy schema on update and be synced without affecting my data. How can I achieve this? I could not find a tutorial anywhere. If there is one please do give me the link.
I think this tutorial explains what your are looking for
baeldung maven liquibase plugin
In section 5.3 is a description on how you can get a changlog file with differences between two databases.
How can I insert data to a table on Spring Boot application start? My application is generated by JHipster. What I need to check is that if that particular data already exist in that table or not. If it doesn't I should add it.
If your application was generated by JHipster, then it should already include and be properly configured for Liquibase.
You have a few options:
You can use Liquibase's insert change to insert data.
You can put your data in a CSV file and use the loadData change to load it. Look for the loadData tag in 00000000000000_initial_schema.xml for examples.
You can use the sql change to run native SQL directly.
All three options can be combined with preconditions to make sure the data doesn't exist before trying to insert it. If you need the changeset to run every time you boot your application, you can use the runAlways="true" attribute (docs for that are on this page).
You can create a function in your service class which checks if the data already exists or not and if not then save that data.
You can implement an ApplicationRunner and use a repository to do whatever you need to do.
If the ApplicationRunner is a spring bean it is run on application startup.
For more sophisticated requirements I would try to rely on a tool like flyway that has good integration with spring boot
so im quite new to all spring and hibernate so i used a feature in myeclipse called generate CRUD application (it uses spring and hibernate for the heart of the application and JSF for presentation objects)that im intended to make changes so that i can work with .. my question is the following .. after i made the application that works fine by the way , i discovered that there are fields and probably even tables to be added to the database(an oracle 11g instance database)..so my questions are the following:
if i create the classes and update the existing .. will it be written directly in the database?
if not is there any way to do it because i dont think a direct update in the database will be a good idea ..
thank you in advance ..
If I understand correctly, you want to know whether the database schema can be created/updated automatically from your #Entity classes, and how to enable/disable such creation. Yes, it's possible by using some property. The name of the property would depend on your project kind. For example, in a default Spring Boot application, you can have
spring.jpa.hibernate.ddl-auto: update
in application.properties. The value update above will have the schema automatically created on first run and then updated on subsequently. validate instead of update won't alter the schema, but just validate it.
This stackoverflow post lists the possible values and their behaviour.