Develop Reference

How would liquibase work for different deployments or prod environments on integration with maven plugin?

I have integrated liquibase with maven plugin (in pom.xml) along with jOOQ generator that reads from db connection after liquibase migration.
The liquibase migration -> jooq generator runs on running mvn clean compile (Compile and build step).
I am wondering how will the liquibase change-management work for different deployments or different prod environments?
Will it create tables automatically for all the prod environments? Please guide.

This seems like the same ask as your earlier question.
If it's not the same, then the first place to look is Liquibase Documentation for Maven and then the jOOQ manual for Code generation from Liquibase XML, YAML, JSON files.

How does production database creation work in Jhipster?

Having some issues when uploading my jhipster generated app to heroku, after some research I found out that some entity modifications I did while developing are not done in production db so some fields are missing.
I also added a field to User entity, so now I cannot even register/login while that field is missing from the table.
Would like to know how exacly the database generation works in prod mode so I can make it work. Could it be related to smth missing in liquibase changelog?(I'm absolutely new to liquibase so I'm a bit lost).
UPDATE:
The problem seems to be a missing column from "jhi_user" table. I need to create a database changelog to add that missing column, so I ran
"mvn liquibase:generateChangeLog"
I saw the correct changelog poping in the console, but no changelog was created under my changelogs folder. What am i doing wrong?

First, check that there is a migration file corresponding to your entity in the directory:
src/main/resources/config/liquibase/changelog/
Then confirm that the Heroku app has a Database by running:
heroku addons
Then run Maven to repackage your WAR file:
mvn install -Pprod -DskipTests
Then deploy again:
heroku deploy:jar target/*.war
JHipster will run migrations at boot time. If you are using Postgresql, you can inspect the tables by running heroku pg:psql and using commands like \d

The problem was changelogs were not beeing generated when i created entities from yo jhipster:entity command.
Solved the issue doing:
mvn liquibase:diff
Plus some hand-done changesets and adding them to master.xml.
After that:
mvn liquibase:dropAll
mvn liquibase:update
Then deployed to heroku and every table was created.

Flyway repair with Spring Boot

I don't quite understand what I am supposed to do when a migration fails using Flyway in a Spring Boot project.
I activated Flyway by simply adding the Flyway dependency in my pom.xml. And everything works fine. My database scripts are migrated when I launch the Spring Boot app.
But I had an error in one of my scripts and my last migration failed. Now when I try to migrate, there is a "Migration checksum mismatch". Normally, I would run mvn flyway:repair, but since I am using Spring Boot, I am not supposed to use the Flyway Maven plug-in. So what am I supposed to do?

there are several ways to perform a repair on the database. I personally prefer the simple SQL statement.
SQL Statement:
Just delete the row with the failed migration. After that you can run the migration again.
Run flyway directly
You can install Flyway local and run flyway repair in the console
Use the Flyway Maven Plugin
Add the Flyway Maven Plugin to your pom and run mvn flyway:repair. I don't think this contradict with the Spring Boot concept.
Extend Spring Boot
Spring Boot will call Flyway.migrate() to perform the database migration. If you would like more control, provide a #Bean that implements FlywayMigrationStrategy.
In the FlywayMigrationStrategy you can call the migrate or repair method from flyway. More Information is available in the Spring Boot Reference Guide.
I don't think the FlywayMigrationStrategy in the application is the right place to repair the database. A failed migration is a exception and should be handle outside the application.

You can do it through code by declaring the following bean.
#Bean
public FlywayMigrationStrategy cleanMigrateStrategy() {
return flyway -> {
flyway.repair();
flyway.migrate();
};
}

Flyway Maven Plugin
Just to add this info to #Daniel's answer
1.
...
<plugin>
<groupId>org.flywaydb</groupId>
<artifactId>flyway-maven-plugin</artifactId>
<version>4.1.0</version>
<configuration>
<url>jdbc:mysql://localhost:3306</url>
<user>root</user>
<password>root</password>
<schemas>
<schema>[your_schema]</schema>
</schemas>
</configuration>
</plugin>
...
2.
mvn flyway:clean
3.
mvn flyway:repair
PS.: if the step 2 and 3 don't work change the order.
More info on maven goals: https://flywaydb.org/documentation/maven/

When database migration fails, the migration is marked as failed in the schema history table (i.e flyway_schema_history) indicating manual database cleanup may be required. But if database supports DDL transactions, the migration is rolled back automatically and nothing is recorded in the schema history table. PostgreSQL, Amazon Redshift, MS SQL are few of the databases which support DDL transactions whereas Oracle Database, MySQL, MariaDB, Amazon Aurora does not support DDL transactions.
In case of failed migration entries, there are several options to repair it (only applicable for databases that do NOT support DDL transactions) as described by #daniel-käfer. I want to add another (may be easier way) to deal with failed migrations.
There are several callbacks supported by flyway, afterMigrateError is one of them. If we add a sql file with name afterMigrateError.sql then, it will be executed after each failed migrate runs. Therefore, we can simply create a file afterMigrateError.sql on default location of database migration folder (resources/db/migration) with sql command to remove failed migrations from flyway_schema_history table.
The sql command afterMigrateError.sql can be as mentioned below:
DELETE IGNORE FROM flyway_schema_history WHERE success=0;
This command looks for the table flyway_schema_history if it exists otherwise it will do no changes. Then it simply looks for the rows which has success column with 0 entry (actually this happen if migration fails , all successful migration will have value 1 in success column), then delete such entries. Now, we can simply change our latest migration file and correct it and run again.

Install flyway locally as said above, change directory into the installation then run (example for H2):
./flyway -url=jdbc:h2:/Users/mugo/dev/h2/das-boot -user=sa -password= repair

How to update the JHipster project after updating JHipster generator?

I updated my JHipster installation as per this page by running the command
npm update -g generator-jhipster
But to update my application I am not sure where should I run the next command yo jhipster.
I tried running it from the root of existing project, but it asked me to enter the name of the new project.
I tried running it at one level above the root of existing project, then also it asked me the name of the new project. But this time I entered the same name and the jhipster generation process ran. However there was no change in any of the major files like package.json or Gruntfile.js or bower.json
What is the correct way to update a JHipster project, once the JHipster generator is updated?

JHipster developers replied over twitter saying that yo jhipster has to be executed at the project root folder.

Following [jhipster releases] (https://jhipster.github.io/2015/05/31/jhipster-release-2.14.2.html):
How to upgrade
Update your version of JHipster with:
npm update -g generator-jhipster
And then you can update your project when you run again
yo jhipster
You can also update your entities by running again the entity sub-generator, for example if your entity is named Foo
yo jhipster:entity Foo

JHipster now has a page on Upgrading an application.
https://jhipster.github.io/upgrading-an-application/
TL;DR
Running the upgrade sub-generator
Go into the application’s root directory:
cd myapplication/
To upgrade your application, type:
yo jhipster:upgrade
If you want to run the upgrade sub-generator even if no new JHipster version is available, type:
yo jhipster:upgrade --force

If you want to update all entities you need to run
yo jhipster --with-entities
from the root of your project

Our jHipster monolithic project is based on an older build of the generator, and still reliant on bower / angularjs for the client. Thus the auto-update ability would never work.
I've been manually updating spring-boot-starter-parent every other sprint to try and bring it up into 2.x parity, but am still unable to leave the 1.5.x version stream due to various dependency issues with (mainly) Hibernate.
As a possible suggestion if you're in the same boat with your own monolithic project:
Pull down select versions of the jhipster-generator
Generate a "hello world" starter monolithic project
Compare the generated pom.xml with your own project
Compare the generated entity and configuration files with your own project

Run below command at the root of your project. Also, make sure to delete nodemodules and target folders before upgrading the project.
yo jhipster:upgrade

jhipster --force --with-entities this is how i do it (npm)

Hibernate Setup

I always used Hibernate annotations in my old job, but since all our projects were already set up, I never really learned the mechanism behind it.
Could someone please give me a brief outline of how to set everything up, just to get me started?
I am developing in Java using Maven and Oracle 10g Express Edition. My IDE is Eclipse.

I'd recommend starting with the Hibernate tutorial. Basically, you'll need to create a Hibernate configuration file on your classpath (dropping it in src/main/resources works with the default Maven project layout) and then start annotating your data objects. There's a tutorial for Hibernate with XML configuration as well.

The (non-Maven) steps to build a Hibernate project in Eclipse would be:
Step 1: Add the required JARs to setup Hibernate project
Step 2: Add the JARs to the lib folder of your project
Step 3: Additionally, I would suggest you to explore the Hibernate directory structure since you are using it for the first time.
If you need more assistance, I wrote a post on my site http://myjavatrainer.com/setup-hibernate-project/
Hope it will be helpful to you.
Maven is build tool for your projects. Maven is a build tool by Apache, it will help to manage the dependencies better. You will have to install Maven separately and set it up. Read its documentation full and get it setup. Instead of creating a normal Java app or a web app in Eclipse, you will be creating a Maven project.
MAKE SURE YOU ADD A JAR FOR DRIVER CONNECTOR for the type of database you are planning to use through Hibernate.