Spring Boot: Change property placeholder signifier

Question

What is the easiest way to change the prefix and suffix for the property placeholder in Spring Boot?

The default is @Value("${some.property}"), however this looks ugly in Kotlin, since it needs to be escaped - ${something} is a language feature in Kotlin for String templates.

Answer 1

It is possible to customize the prefix used by declaring the following beans in your configuration:

@Bean
fun propertyConfigurer() = PropertySourcesPlaceholderConfigurer().apply {
    setPlaceholderPrefix("%{")
}

if you have any existing code (like Spring Boot actuators or @LocalServerPort) that is using the ${...} syntax, you should declare:

@Bean
fun kotlinPropertyConfigurer() = PropertySourcesPlaceholderConfigurer().apply {
    setPlaceholderPrefix("%{")
    setIgnoreUnresolvablePlaceholders(true)
}

@Bean
fun defaultPropertyConfigurer() = PropertySourcesPlaceholderConfigurer()

Escaping the dollar like in @Value("\${some.property}") is another possible option that require no @Bean declaration.

For Spring Boot tests configured with @SpringBootTest(webEnvironment = WebEnvironment.RANDOM_PORT) you can use @LocalServerPort instead of @Value("\${local.server.port}").

@ConfigurationProperties would be a better alternative, especially with Kotlin data classes, but currently you have to use Kotlin classes with nullable var properties since only getter/setter are supported. You can vote for this issue or comment to show your interest in getting that supported in Spring Boot 2.x.