The annotation will create a bean for each sub-property within the given property. As an example consider the following class:

Using @EachProperty

Using @EachProperty

@EachProperty("test.datasource")
(1)
class DataSourceConfiguration {
    final String name
    URI url = new URI("localhost")
    DataSourceConfiguration(@Parameter String name) (2)
            throws URISyntaxException {
        this.name = name
    }
}

@EachProperty("test.datasource")  (1)
class DataSourceConfiguration (2)
@Throws(URISyntaxException::class)
constructor(@param:Parameter val name: String) {
    (3)
    var url = URI("localhost")

The above DataSourceConfiguration defines a property to configure one or many hypothetical data sources of some sort. The URLs themselves can be configured using any of the PropertySource instances evaluated to Micronaut:

Providing Configuration to @EachProperty

Providing Configuration to @EachProperty

    ApplicationContext applicationContext = ApplicationContext.run(PropertySource.of(
            "test",
            [
                    "test.datasource.one.url": "jdbc:mysql://localhost/one",
                    "test.datasource.two.url": "jdbc:mysql://localhost/two"
            ]
    ))

        val applicationContext = ApplicationContext.run(PropertySource.of(
                "test",
                mapOf(
                        "test.datasource.one.url" to "jdbc:mysql://localhost/one",
                        "test.datasource.two.url" to "jdbc:mysql://localhost/two"
                )
        ))

In the above example two data sources (called one and two) are defined under the test.datasource prefix defined earlier in the @EachProperty annotation. Each of these configuration entries triggers the creation of a new DataSourceConfiguration bean such that the following test succeeds:

Evaluating Beans Built by @EachProperty

Evaluating Beans Built by @EachProperty

        when:
        Collection<DataSourceConfiguration> beansOfType = applicationContext.getBeansOfType(DataSourceConfiguration.class)
        assertEquals(2, beansOfType.size()) (1)
                DataSourceConfiguration.class,
                Qualifiers.byName("one") (2)
        )
        then:
        new URI("jdbc:mysql://localhost/one") == firstConfig.getUrl()

        val beansOfType = applicationContext.getBeansOfType(DataSourceConfiguration::class.java)
        assertEquals(2, beansOfType.size.toLong()) (1)
        val firstConfig = applicationContext.getBean(
                DataSourceConfiguration::class.java,
                Qualifiers.byName("one") (2)
        )
        assertEquals(
                URI("jdbc:mysql://localhost/one"),
                firstConfig.url
        )