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.
Related
Am using Spring Data JPA and hibernate in as springboot project for persistence, Whenever the method findyById() method on the Repository(JPA CRUD Repository) returns no data for the Primary key for an entity which uses #Version annotation for optimistic locking, it tries to insert an entity to the database.
I could see the insert query generated in the log file.
Has anyone come across such an issue? Please help.
The things I noticed from your explanation seem very strange to the program because this should not happen, you are just doing a simple query, it should not depend on the output of the query. Consider how much you have to look at different situations in very large application to avoid unexpected behaviors that cause problems.
One of the goals of ORM (Hibernate, etc.) is to ensure that the application meets your needs without worries.
There may be configuration on the side of your existing application that cause this problem.
In my opinion, to understand the problem, create another simple project with the minimum requirements, try again.
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/
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
I need a why to change the JPA catalog element in my java class? We have many database environments which we need to be able to deploy our application too. Example: In your dev environment we have a database for new development, and production support. All database live on the same server so we have the following database names: am_web_dd and am_web_ps. So we need to be able to change the catalog at build time or start up time. We've thought of using Maven to do a search and replace during build but I was wondering if there is a way of doing this with a parameter?
Here is one of our #RooJpaActiceRecord statements:
#RooJpaActiveRecord(catalog = "am_web_t4", schema = "dbo", table = "user_t")
I would like to be able to make catalog a parameter. Is this possible? if not what would be the best approach?
Thank you for your time!
I know it is possible from a JPA standpoint, but I don't think you will be able to using straight Roo. This might help.
There may also be a way to use a Java Configuration object in Spring to build your JPA Entity Manager. I think that's were you want to set it.
The approach you suggest of making catalog dynamic would be suitable if you wanted to let the user choose/change the schema on demand, however, it looks like this is not your requirements, so I would steer away from this path as it more difficult than you need.
You can use spring profiles to define different database connections and use an environment variable to define which one is active. Spring profiles can be set in XML or java configuration classes.