4.6 Using @EachProperty to Drive Configuration

The @ConfigurationProperties annotation is great for a single configuration class, but sometimes you want multiple instances each with their own distinct configuration. That is where EachProperty comes in.

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

Using @EachProperty

import io.micronaut.context.annotation.Parameter;
import io.micronaut.context.annotation.EachProperty;
@EachProperty("test.datasource")  (1)
public class DataSourceConfiguration {
    private final String name;
    private URI url = new URI("localhost");
    public DataSourceConfiguration(@Parameter String name) (2)
            throws URISyntaxException {
        this.name = name;
    }
    public String getName() {
        return name;
    }
    public URI getUrl() { (3)
        return url;
    }
    public void setUrl(URI url) {
        this.url = url;
    }
}

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
    }
}

Using @EachProperty

@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 url 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

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

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"
            ]
    ))

Providing Configuration to @EachProperty

        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

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

Evaluating Beans Built by @EachProperty

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

Evaluating Beans Built by @EachProperty

        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
        )