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 its own distinct configuration. That is where EachProperty comes in.

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

Using @EachProperty

import java.net.URI;
import java.net.URISyntaxException;
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

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

Using @EachProperty

import io.micronaut.context.annotation.EachProperty
import io.micronaut.context.annotation.Parameter
import java.net.URI
import java.net.URISyntaxException
@EachProperty("test.datasource")  (1)
class DataSourceConfiguration
@Throws(URISyntaxException::class)
constructor(@param:Parameter val name: String) { (2)
    var url = URI("localhost") (3)
}

The above DataSourceConfiguration defines a url property to configure one or more data sources. 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) (1)
        val firstConfig = applicationContext.getBean(
                DataSourceConfiguration::class.java,
                Qualifiers.byName("one") (2)
        )
        assertEquals(
                URI("jdbc:mysql://localhost/one"),
                firstConfig.url
        )

List-Based Binding

The default behavior of @EachProperty is to bind from a map style of configuration, where the key is the named qualifier of the bean and the value is the data to bind from. For cases where map style configuration doesn’t make sense, it is possible to inform Micronaut that the class is bound from a list. Simply set the list member on the annotation to true.

@EachProperty List Example

import io.micronaut.context.annotation.EachProperty;
import io.micronaut.context.annotation.Parameter;
import io.micronaut.core.order.Ordered;
import java.time.Duration;
@EachProperty(value = "ratelimits", list = true) (1)
public class RateLimitsConfiguration implements Ordered { (2)
    private final Integer index;
    private Duration period;
    private Integer limit;
    RateLimitsConfiguration(@Parameter Integer index) { (3)
        this.index = index;
    }
    @Override
    public int getOrder() {
        return index;
    }
    public Duration getPeriod() {
        return period;
    }
    public void setPeriod(Duration period) {
        this.period = period;
    }
    public Integer getLimit() {
        return limit;
    }
    public void setLimit(Integer limit) {
        this.limit = limit;
    }
}

@EachProperty List Example

import io.micronaut.context.annotation.EachProperty
import io.micronaut.context.annotation.Parameter
import io.micronaut.core.order.Ordered
import java.time.Duration
@EachProperty(value = "ratelimits", list = true) (1)
class RateLimitsConfiguration implements Ordered { (2)
    private final Integer index
    Duration period
    Integer limit
    RateLimitsConfiguration(@Parameter Integer index) { (3)
        this.index = index
    }
    @Override
    int getOrder() {
        index
    }
}

@EachProperty List Example

import io.micronaut.context.annotation.EachProperty
import io.micronaut.context.annotation.Parameter
import io.micronaut.core.order.Ordered
import java.time.Duration
@EachProperty(value = "ratelimits", list = true) (1)
class RateLimitsConfiguration
    constructor(@param:Parameter private val index: Int) (3)
    : Ordered { (2)
    var period: Duration? = null
    var limit: Int? = null
    override fun getOrder(): Int {
        return index
    }
}