avaje / avaje-spi-service

avaje-spi-service

Uses Annotation processing to automatically add META-INF/services entries for classes and validate module-info.java files.

Usage

1. Add dependency:

<dependency>
  <groupId>io.avaje</groupId>
  <artifactId>avaje-spi-service</artifactId>
  <version>${spi.version}</version>
  <optional>true</optional>
  <scope>provided</scope>
</dependency>

When working with Java modules you need to add the annotation module as a static dependency.

module my.module {
  requires static io.avaje.spi;
}

2. Add @ServiceProvider

On classes that you'd like registered, put the @ServiceProvider annotation. As long as you only have one interface or one superclass, that type is assumed to be the spi interface. So given the example below:

@ServiceProvider
public class MyProvider implements SomeSPI {
  ...
}

You get the META-INF/services/com.example.SomeSPI file whose content is org.acme.MyProvider.

If you have multiple interfaces and/or base type, the library cannot infer the contract type. In such a case, specify the contract type explicitly by giving it to @ServiceProvider like this:

@ServiceProvider(SomeSPI.class)
public class MyExtendedProvider extends AbstractSet implements Comparable, Serializable, SomeSPI {
  ...
}

3. module-info validation

For modular projects, the processor will throw a compile error describing what provides statements you have missed. So if you define the SPI like the the previous steps, and have a module setup like the following:

module my.module {

  requires static io.avaje.spi;

}

You'll get the following compile error:

 Compilation failure /src/main/java/module-info.java:[1,1]
 Missing `provides SomeSPI with MyProvider, MyExtendedProvider;`

Related Works

• Pistachio