[JAVA] A story about introducing Evolutions into the Play Framework

Operating environment

OS OSX
Play Framework 2.5.10(Java)
JDK 1.8.0
MySQL 5.7.18
IntelliJ IDEA

What is Evolutions?

Evolustions is a Play Framework DB migration tool. You can easily update and share your DB schema among multiple developers.

Introduction background

In local development, multiple developers used their respective DBs to add columns and tables. I used the same source code, but the DB schema was different, so I had to update it manually often. Matching the DB schema across multiple developers is easy with Evolutions.

How to use Evolutions

Evolutions setup

Added ʻevolutions` to the list of dependent libraries in build.sbt

`build.sbt`


name := """play-evolutions-sample"""

version := "1.0-SNAPSHOT"

lazy val root = (project in file(".")).enablePlugins(PlayJava)

scalaVersion := "2.11.7"

libraryDependencies ++= Seq(
  "mysql" % "mysql-connector-java" % "5.1.38",
  javaJdbc,
  cache,
  javaWs,
  evolutions
)

Click Refresh project in the upper right

Check the settings in application.conf

It is commented out by default, but make sure it is not false just in case

`application.conf`


play.evolutions {
  # You can disable evolutions for a specific datasource if necessary
  #db.default.enabled = false
}

Or explicitly write db.default.enabled = true

Description of Evolution Script

Create a directory $ mkdir -p conf/evolutions/default Create and describe a SQL file that modifies the database under conf / evolutions / default

It consists of two parts, Ups and Downs, and the contents to be described are as follows.

# --- !Ups

Description of the required schema conversion method(SQL statement)


# --- !Downs 

Description of how to undo the above conversion(SQL statement)

If you want to add a new dummy table

`1.sql`


# --- !Ups
create table dummy(
    id integer not null,
    name varchar(255),
    created_at datetime not null,
    updated_at datetime not null
);

# --- !Downs 
drop table dummy

If you want to add a column to the dummy table

`2.sql`


# --- !Ups
ALTER TABLE dummy ADD(
    deleted_at datetime not null
);

# --- !Downs
ALTER TABLE dummy DROP(
    deleted_at
);

About file name

Name the files 1.sql for the first script, 2.sql for the second script, and so on.

About execution

Run locally with $ activator run and jump tohttp: // localhost: 9000 / ʻApply this script now!` Pressing the button will execute the described Evolution Script

About Downs

Downs are not run manually, they are run when the contents of the Ups change. Downs is executed before Ups is executed, and as a result, the schema of the database is updated.

References

Evolutions - 2.1.x The source code is here