implemented LinkEnricher registration via Enrich annotation

scm-annotations/src/main/java/sonia/scm/api/v2/resources/Enrich.java

@@ -0,0 +1,26 @@
+package sonia.scm.api.v2.resources;
+
+import java.lang.annotation.Documented;
+import java.lang.annotation.ElementType;
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
+import java.lang.annotation.Target;
+
+/**
+ * Annotation to specify the source of an enricher.
+ *
+ * @author Sebastian Sdorra
+ * @since 2.0.0
+ */
+@Documented
+@Target(ElementType.TYPE)
+@Retention(RetentionPolicy.RUNTIME)
+public @interface Enrich {
+
+  /**
+   * Source mapping class.
+   *
+   * @return source mapping class
+   */
+  Class<?> value();
+}

scm-core/src/main/java/sonia/scm/api/v2/resources/LinkEnricher.java

@@ -1,11 +1,18 @@
 package sonia.scm.api.v2.resources;
 
+import sonia.scm.plugin.ExtensionPoint;
+
 /**
  * A {@link LinkEnricher} can be used to append hateoas links to a specific json response.
+ * To register an enricher use the {@link Enrich} annotation or the {@link LinkEnricherRegistry} which is available
+ * via injection.
+ *
+ * <b>Warning:</b> enrichers are always registered as singletons.
  *
  * @author Sebastian Sdorra
  * @since 2.0.0
  */
+@ExtensionPoint
 @FunctionalInterface
 public interface LinkEnricher {
 

scm-webapp/src/main/java/sonia/scm/api/v2/resources/LinkEnricherAutoRegistration.java

@@ -0,0 +1,45 @@
+package sonia.scm.api.v2.resources;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+import sonia.scm.plugin.Extension;
+
+import javax.inject.Inject;
+import javax.servlet.ServletContextEvent;
+import javax.servlet.ServletContextListener;
+import java.util.Set;
+
+/**
+ * Registers every {@link LinkEnricher} which is annotated with an {@link Enrich} annotation.
+ */
+@Extension
+public class LinkEnricherAutoRegistration implements ServletContextListener {
+
+  private static final Logger LOG = LoggerFactory.getLogger(LinkEnricherAutoRegistration.class);
+
+  private final LinkEnricherRegistry registry;
+  private final Set<LinkEnricher> enrichers;
+
+  @Inject
+  public LinkEnricherAutoRegistration(LinkEnricherRegistry registry, Set<LinkEnricher> enrichers) {
+    this.registry = registry;
+    this.enrichers = enrichers;
+  }
+
+  @Override
+  public void contextInitialized(ServletContextEvent sce) {
+    for (LinkEnricher enricher : enrichers) {
+      Enrich annotation = enricher.getClass().getAnnotation(Enrich.class);
+      if (annotation != null) {
+        registry.register(annotation.value(), enricher);
+      } else {
+        LOG.warn("found LinkEnricher extension {} without Enrich annotation", enricher.getClass());
+      }
+    }
+  }
+
+  @Override
+  public void contextDestroyed(ServletContextEvent sce) {
+    // nothing todo
+  }
+}

scm-webapp/src/test/java/sonia/scm/api/v2/resources/LinkEnricherAutoRegistrationTest.java

@@ -0,0 +1,64 @@
+package sonia.scm.api.v2.resources;
+
+import com.google.common.collect.ImmutableSet;
+import org.junit.jupiter.api.Test;
+
+import java.util.Set;
+
+import static org.assertj.core.api.Java6Assertions.assertThat;
+
+class LinkEnricherAutoRegistrationTest {
+
+  @Test
+  void shouldRegisterAllAvailableLinkEnrichers() {
+    LinkEnricher one = new One();
+    LinkEnricher two = new Two();
+    LinkEnricher three = new Three();
+    LinkEnricher four = new Four();
+    Set<LinkEnricher> enrichers = ImmutableSet.of(one, two, three, four);
+
+    LinkEnricherRegistry registry = new LinkEnricherRegistry();
+
+    LinkEnricherAutoRegistration autoRegistration = new LinkEnricherAutoRegistration(registry, enrichers);
+    autoRegistration.contextInitialized(null);
+
+    assertThat(registry.allByType(String.class)).containsOnly(one, two);
+    assertThat(registry.allByType(Integer.class)).containsOnly(three);
+  }
+
+  @Enrich(String.class)
+  public static class One implements LinkEnricher {
+
+    @Override
+    public void enrich(LinkEnricherContext context, LinkAppender appender) {
+
+    }
+  }
+
+  @Enrich(String.class)
+  public static class Two implements LinkEnricher {
+
+    @Override
+    public void enrich(LinkEnricherContext context, LinkAppender appender) {
+
+    }
+  }
+
+  @Enrich(Integer.class)
+  public static class Three implements LinkEnricher {
+
+    @Override
+    public void enrich(LinkEnricherContext context, LinkAppender appender) {
+
+    }
+  }
+
+  public static class Four implements LinkEnricher {
+
+    @Override
+    public void enrich(LinkEnricherContext context, LinkAppender appender) {
+
+    }
+  }
+
+}