How do placeholders work in Flyway?

Question

I\'m evaluating Flyway for use in my project. Our current SQL scripts contain placeholders for things like URLs which will have a different domain names depending on the env

Answer 1

Currently when supplying placeholders as properties, the property name should be prefixed with flyway.placeholders.

For example the ${env.token} placeholder can be specified directly as this Ant property: flyway.placeholders.env.token

There is currently no support for passing a property file directly, without using prefixes for the property names. Feel free to raise an issue in the Issue Tracker. :-)

Answer 2

Maven version:

<build>
    <plugins>
        <plugin>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-maven-plugin</artifactId>
        </plugin>
        <plugin>
            <groupId>org.flywaydb</groupId>
            <artifactId>flyway-maven-plugin</artifactId>
            <configuration>
                <url>jdbc:mysql://localhost/cloud</url>
                <user>root</user>
                <password>root</password>
                <placeholderReplacement>false</placeholderReplacement>
            </configuration>
            <dependencies>
                <dependency>
                    <groupId>mysql</groupId>
                    <artifactId>mysql-connector-java</artifactId>
                    <version>${mysql.version}</version>
                    <scope>runtime</scope>
                </dependency>
            </dependencies>
        </plugin>
    </plugins>
</build>

Answer 3

From my experience, it's much easier to use environment variables instead of CLI or config file (especialy when using docker and k8s).

You can use environment variables in the following format -

export FLYWAY_PLACEHOLDERS_USER=${USER}

Then in you sql statement, use this variable like this -

INSERT INTO tmptable (user)
VALUES ('${user}')

read more about environment variables here

Answer 4

If the token was subdomain:

INSERT INTO FEED VALUES ('app.${subdomain}.company.org/feed1', 'My Feed');

The values in flyway.conf:

flyway.url=jdbc:mydb://db
flyway.user=root
flyway.schemas=schema1
flyway.placeholders.subdomain=example

Or command line:

flyway -url=jdbc:mydb://db -user=root -schemas=schema1 -placeholders.subdomain=example migrate

Would run the script as:

INSERT INTO FEED VALUES ('app.example.company.org/feed1', 'My Feed');