This document summarizes new features in Grails 1.4 related to agile database modeling, including replacing HSQLDB with H2 as the default in-memory database, adding reverse engineering capabilities to generate GORM classes from an existing database, and implementing database migrations based on Liquibase to version control and rollback database schema changes. It provides an overview and status of these features, which are currently available as plugins, and demonstrates reverse engineering and database migrations.

1. Agile Database Modelling
New GORM Features in Grails 1.4
Prepared for SF Grails Café Centro
March 2011
by Christian Hang
Thanks to Taulia for hosting and food!!

2. Agenda
New (GORM) Features in Grails 1.4
Quick intro to H2
Reverse Engineering
Database Migrations
Other new Grails 1.4 features
Summary

3. New (GORM) Features in Grails 1.4
Replace HQSQL with H2
Best-of-bread in-memory DB
Built-in web console

4. New (GORM) Features in Grails 1.4
Replace HQSQL with H2
Best-of-breed in-memory DB
Built-in web console
Reverse Engineering
Based on Hibernate's reverse engineering
Create GORM classes from existing DB

5. New (GORM) Features in Grails 1.4
Replace HQSQL with H2
Best-of-bread in-memory DB
Built-in web console
Reverse Engineering
Based on Hibernate's reverse engineering
Create GORM classes from existing DB
Database Migrations
Based on Liquibase
"Revision" the DB
Allows track/rollback schema changes

6. Current Status
No hard dependencies on Grails 1.4
Everything available as plugins today
Both main features developed by Burt Beckwith

7. Current Status
No hard dependencies on Grails 1.4
Everything available as plugins today
Both main features developed by Burt Beckwith
H2 plugin or JAR dependency
com.h2database:h2:1.2.147

8. Current Status
No hard dependencies on Grails 1.4
Everything available as plugins today
Both main features developed by Burt Beckwith
H2 plugin or JAR dependency
com.h2database:h2:1.2.147
Reverse Engineering
http://grails-plugins.github.com/grails-db-reverse-engineer/
grails install-plugin db-reverse-engineer
latest version 0.3

9. Current Status
No hard dependencies on Grails 1.4
Everything available as plugins today
Both main features developed by Burt Beckwith
H2 plugin or JAR dependency
com.h2database:h2:1.2.147
Reverse Engineering
http://grails-plugins.github.com/grails-db-reverse-engineer/
grails install-plugin db-reverse-engineer
latest version 0.3
Database Migrations
http://grails-plugins.github.com/grails-database-migration/
grails install-plugin database-migration
latest version 0.2

10. Take your DB tools with you

11. H2 in Grails 1.4
Replaces HSQLDB
support in-memory, file-based, clustered DB
comes with a build-in web console
http://localhost:8080/appname/dbconsole
Available as (insecure) plugin today

12. Use legacy databases
in Grails even faster!

13. Reverse Engineering
Existing DB + Grails command = GORM classes

14. Reverse Engineering
Existing DB + Grails command = GORM classes
Uses DB connection from DataSource.groovy
Configuration in grails-app/conf/Config.groovy
Started with grails db-reverse-engineer

15. Reverse Engineering
Existing DB + Grails command = GORM classes
Uses DB connection from DataSource.groovy
Configuration in grails-app/conf/Config.groovy
Started with grails db-reverse-engineer
Detailed configuration available
covers many-to-many relations
include/exclude tables, columns etc.
Creates belongsTo, hasMany and constraints
Simplest configuration:
grails.plugin.reveng.packageName = com.acme.db

16. Demo Reverse Engineering

17. The good and the bad
Recognizes length limitations & constraints
Creates relates between entities
Even handles composite primary keys

18. The good and the bad
Recognizes length limitations & constraints
Creates relates between entities
Even handles composite primary keys
Careful: Will probably not get it 100% correct!
Always review generated classes

19. The good and the bad
Recognizes length limitations & constraints
Creates relates between entities
Even handles composite primary keys
Careful: Will probably not get it 100% correct!
Always review generated classes
Still helps to save a lot of work

20. Your source code is in VCS,
but do you version your DB?

21. Database Migrations
Liquibase: verbose XML schema changesets

22. Database Migrations
Liquibase: verbose XML schema changesets
<?xml version="1.0" encoding="UTF-8" standalone="no"?>
<databaseChangeLog xmlns="http://www.liquibase.org/xml/ns/dbchangelog"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://www.liquibase.org/xml/ns/dbchangelog
http://www.liquibase.org/xml/ns/dbchangelog/dbchangelog-2.0.xsd">
<changeSet author="christianhang (generated)" id="1300172497244-1">
<createTable tableName="BLURB">
<column autoIncrement="true" name="ID" type="BIGINT">
<constraints nullable="false" primaryKey="true"
primaryKeyName="CONSTRAINT_3"/>
</column>
<column name="VERSION" type="BIGINT">
<constraints nullable="false"/>
</column>
<column name="CONTENT" type="VARCHAR(100000)"/>
<column name="NAME" type="VARCHAR(255)">
<constraints nullable="false"/>
</column>
</createTable>
</changeSet>
....

23. Database Migrations
Liquibase: verbose XML schema changesets
Plugin: Groovy changesets & automation

24. Database Migrations
Liquibase: verbose XML schema changesets
Plugin: Groovy changesets & automation
databaseChangeLog = {
changeSet(author: "christianhang (generated)", id: "1300168672278-1") {
createTable(tableName: "BLURB") {
column(autoIncrement: "true", name: "ID", type: "BIGINT") {
constraints(nullable: "false", primaryKey: "true",
primaryKeyName: "CONSTRAINT_3")
}
column(name: "VERSION", type: "BIGINT") {
constraints(nullable: "false")
}
column(name: "CONTENT", type: "VARCHAR(100000)")
column(name: "NAME", type: "VARCHAR(255)") {
constraints(nullable: "false")
}
}
}
...

25. Database Migrations
Liquibase: verbose XML schema changesets
Plugin: Groovy changesets & automation
Automatically generate changelogs
grails dbm-generate-changelog changelog.groovy
grails dbm-gorm-diff
Apply changelogs to database
grails dbm-changelog-sync changelog.groovy
grails dbm-update
Rollback changes
grails dbm-rollback-count
grails dbm-rollback-to-date

26. Database Migrations
Liquibase: verbose XML schema changesets
Plugin: Groovy changesets & automation
Two options
track changes manually (changeset first)
create automatic diffs (GORM first)

27. Database Migrations
Liquibase: verbose XML schema changesets
Plugin: Groovy changesets & automation
Two options
track changes manually (changeset first)
create automatic diffs (GORM first)
Allows to track schema changes in VCS
Create DB from scratch
Apply/rollback incremental changes

28. Database Migrations
Liquibase: verbose XML schema changesets
Plugin: Groovy changesets & automation
Two options
track changes manually (changeset first)
create automatic diffs (GORM first)
Allows to track schema changes in VCS
Create DB from scratch
Apply/rollback incremental changes
Possibilities:
Simplifies development with changing DB
Manage updates to production DB

29. Demo Database Migrations

30. Issues to watch out for
BACKUP your database!
Always review automatic changesets!

31. Issues to watch out for
BACKUP your database!
Always review automatic changesets!
Indexes, triggers etc. might be missed
Checksum errors
Changes tracked by filename in
grails-app/conf/migrations/xxxx.groovy
It doesn't like changeset changes

32. Summary
New goodies before Grails 1.4 release
Lots of automation when working with databases
Reverse Engineering simplifies app setup
Best practice: Version your DB

33. References
http://grails-plugins.github.com/grails-db-reverse-
engineer/docs/manual/index.html
http://grails-plugins.github.com/grails-db-reverse-
engineer/docs/manual/index.html
http://fbflex.wordpress.com/2011/01/19/working-with-the-grails-
database-migration-plugin/
http://burtbeckwith.com/blog/?p=376

34. Contact
Email: christian.hang@gmail.com
Twitter: @livingtocode
Blog: livingtocode.com
http://sfgrails.com
@sfgrails
Thanks to Taulia for hosting and food!!