Chapter 7. Property expressions

Substituting the value of a configuration property:

You can use a property expression to avoid hardcoding property values in you configuration. Use the ${<property_name>} syntax to write an expression that references a configuration property, as shown in the following example:

remote.host=quarkus.io
callable.url=https://${remote.host}/

remote.host=quarkus.io
callable.url=https://${remote.host}/

The value of the callable.url property resolves to https://quarkus.io/.

Setting a property value that is specific to a particular configuration profile:

In the following example, the %dev configuration profile and the default configuration profile are set to use data source connection URLs with different host addresses. Depending on the configuration profile with which you start your application, your data source driver uses the database URL that you set for the profile:

%dev.quarkus.datasource.jdbc.url=jdbc:mysql://localhost:3306/mydatabase?useSSL=false
quarkus.datasource.jdbc.url=jdbc:mysql://remotehost:3306/mydatabase?useSSL=false

%dev.quarkus.datasource.jdbc.url=jdbc:mysql://localhost:3306/mydatabase?useSSL=false
quarkus.datasource.jdbc.url=jdbc:mysql://remotehost:3306/mydatabase?useSSL=false

You can achieve the same result in a simplified way by setting a different value of the custom application.server property for each configuration profile. You can then reference the property in the database connection URL of your application, as shown in the example:

%dev.application.server=localhost
application.server=remotehost

quarkus.datasource.jdbc.url=jdbc:mysql://${application.server}:3306/mydatabase?useSSL=false

%dev.application.server=localhost
application.server=remotehost

quarkus.datasource.jdbc.url=jdbc:mysql://${application.server}:3306/mydatabase?useSSL=false

The application.server property resolves to the appropriate value depending on the profile that you choose when you run your application.

Setting a default value of a property expression:

You can define a default value for a property expression. Quarkus uses the default value if the value of the property that is required to expand the expression is not resolved from any of your configuration sources. You can set a default value of an expression using the following syntax:

${<expression>:<default_value>}

${<expression>:<default_value>}

In the following example, the property expression in the data source URL uses mysql.db.server as the default value of the application.server property:

quarkus.datasource.jdbc.url=jdbc:mysql://${application.server:mysql.db.server}:3306/mydatabase?useSSL=false

quarkus.datasource.jdbc.url=jdbc:mysql://${application.server:mysql.db.server}:3306/mydatabase?useSSL=false

Nesting property expressions:

You can compose property expressions by nesting a property expression inside another property expression. When nested property expressions are expanded, the inner expression is expanded first:

${<outer_property_expression>${<inner_property_expression>}}

${<outer_property_expression>${<inner_property_expression>}}

Multiple property expressions:

You can join two or more property expression together as shown below:

${<first_property>}${<second_property>}

${<first_property>}${<second_property>}

Combining property expressions with environment variables:

You can use property expressions to substitute the values of environment variables. The expression in the following example substitutes the value that is set for the HOST environment variable as the value of the application.host property. When HOST environment variable is not set, application.host uses the value of the remote.host property as the default:

remote.host=quarkus.io
application.host=${HOST:${remote.host}}

remote.host=quarkus.io
application.host=${HOST:${remote.host}}