The development process doesn’t end when you first release your application. Through your own planning, feature requests, and bug reports, developers improve their applications on a regular basis. Sometimes, those changes result in changes to the data structure and underlying database. When users upgrade, they need a process that transitions them to improved versions of your application. For this, you must create an upgrade process.
Here’s what’s involved in creating an upgrade process for your app:
- Specifying the schema version
- Declaring dependencies
- Writing upgrade steps
- Writing the registrator
- Waiting for upgrade completion
Liferay has an Upgrade framework you can use to make this easier to do. It’s a feature-rich framework that makes upgrades safe: the system records the current state of the schema so that if the upgrade fails, the process can revert the module back to its previous version. Meaningful schema versioning is important to clearly communicate the updates to your users.
Liferay DXP’s Upgrade framework executes your module’s upgrades automatically when the new version starts for the first time. You implement concrete data schema changes in upgrade step classes and then register them with the upgrade framework using an upgrade step registrator. An upgrade step is a class that adapts module data to the module’s target database schema. It can execute SQL commands and DDL files to upgrade the data. The Upgrade framework lets you encapsulate upgrade logic in multiple upgrade step classes per schema version.
The Upgrade framework executes the upgrade steps to update the current module
data to the latest schema. The registrator’s
register method informs the
Upgrade framework about each new schema and associated upgrade steps to adapt
data to it. Each schema upgrade is represented by a registration. A
registration is an abstraction for all the changes you need to apply to the
database from one schema version to the next one.
Upgrade registrations are defined by the following values:
- Module’s bundle symbolic name
- Schema version to upgrade from (as a
- Schema version to upgrade to (as a
- List of upgrade steps
A registration’s upgrade step list can consist of as many upgrade steps as needed. How you name and organize upgrade steps is up to you. Liferay’s upgrade classes are organized using a package structure similar to this one:
UpgradeFoo.java← Upgrade Step
UpgradeFoo.java← Upgrade Step
UpgradeBar.java← Upgrade Step
The example upgrade structure shown above is for a module that has two database
2.0.0. They’re represented by packages
v2_0_0. Each version package contains upgrade step classes that update the
database. The example upgrade steps focus on fictitious data elements
Bar. The registrator class (
MyCustomModuleUpgrade, in this example) is
responsible for registering the applicable upgrade steps for each schema
Here are some organizational tips:
Put all upgrade classes in a sub-package called
Group together similar database updates (ones that operate on a data element or related data elements) in the same upgrade step class.
Create upgrade steps in sub-packages named after each data schema version.
The diagram below illustrates the relationship between the registrator and the upgrade steps.
This section covers these topics: