Proper procedure for modifying JHipster Entities using JDL

Question

I am trying out JHipster (version 6.4.1) using a Monolith and disk-based H2 database. I have created some entities in JDL and have the basic CRUD webpages working. Now that I feel comfortable with the process, I want to add fields and rename others. I figured I could simply update the JDL, re-import the JDL, start the application, and see the result of my changes. What I see is ValidationFailedException from Liquibase and the application throwing HTTP 500 errors due to database problems.

I have looked all over for guidance on the proper process for handling this seemingly common development scenario. Most of the places I have looked for guidance (such as https://www.jhipster.tech/creating-an-entity) discuss importing JDL as a one-time-only operation and do not discuss how to incrementally change and import the JDL.

I have tried a number of suggestions as seen on SO, such as not overwriting the changelogs, doing a liquibase:diff, and adding that to master.xml. This still causes the ValidationFailedException. In the master.xml I see the comment <!-- jhipster-needle-liquibase-add-changelog - JHipster will add liquibase changelogs here --> which leads me to believe that JHipster should be doing the heavy lifting, but I am just missing a step.

I am by no means a JHipster nor a Liquibase expert, but I want to learn. How I can perform simple entity updates without a huge hassle?

[Update with more detail]

After re-importing the updated JDL, I have managed to get rid of the DB Validation Errors by blowing away the database with rm -rf target/h2db/db.

I'm happy with my changes and feel like a commit is in order. What I see is

• master.xml is unchanged
• the changelog from the first JDL import has been modified to include the updates I made

If I understand how liquibase works, I would have expected

1. None of the existing changelogs would be touched
2. A brand new changelog file would be created that contained just the JDL changes I made this round
3. master.xml to have changed only in that it would contain an additional changelog entry, pointing to the file created in item 2

Am I misinterpreting how Liquibase represents evolution of the DB schema?

Answer 1

It appears that the page you referenced does have some instructions for updating entities. Farther down the page I saw this:

Updating an existing entity

The entity configuration is saved in a specific .json file, in the .jhipster directory. So if you run the sub-generator again, using an existing entity name, you can update or regenerate the entity.

When you run the entity sub-generator for an existing entity, you will be asked a question ‘Do you want to update the entity? This will replace the existing files for this entity, all your custom code will be overwritten’ with following options:

• Yes, re generate the entity - This will just regenerate your entity. Tip: This can be forced by passing a --regenerate flag when running the sub-generator
• Yes, add more fields and relationships - This will give you questions to add more fields and relationships
• Yes, remove fields and relationships - This will give you questions to remove existing fields and relationships from the entity
• No, exit - This will exit the sub-generator without changing anything

You might want to update your entity for the following reasons:

• You want to add/remove fields and relationships to an existing entity
• You want to reset your entity code to its original state
• You have updated JHipster, and would like to have your entity generated with the new templates
• You have modified the .json configuration file (the format is quite close to the questions asked by the generator, so it’s not very complicated), so you can have a new version of your entity
• You have copy/pasted the .json file, and want a new entity that is very close to the copied entity