TIKA-4700 Support OSGi Service Loader Mediator (#2714)

Generate according capabilities headers for providers via TikaComponent
annotations and Bnd's
https://bnd.bndtools.org/chapters/230-manifest-annotations.html#meta-infservices-annotations.
According capabilities headers for the consumer are generated via Bnd's
ServiceConsumer annotations.

Author: kwin

tika-annotation-processor/src/main/java/org/apache/tika/annotation/TikaComponentProcessor.java

@@ -337,6 +337,8 @@ private void writeServiceFiles() {
                     writer.write("# Generated by TikaComponentProcessor\n");
                     writer.write("# Do not edit manually\n");
                     for (String impl : sortedImplementations) {
+                        // add comments for Bnd to generate OSGi metadata for Service Mediator spec (https://bnd.bndtools.org/chapters/230-manifest-annotations.html#meta-infservices-annotations)
+                        writer.write("#@aQute.bnd.annotation.spi.ServiceProvider()\n");
                         writer.write(impl);
                         writer.write("\n");
                     }

tika-core/src/main/java/org/apache/tika/config/ServiceLoader.java

@@ -34,14 +34,25 @@
 import java.util.Set;
 import java.util.regex.Pattern;
 
+import aQute.bnd.annotation.spi.ServiceConsumer;
+
+import org.apache.tika.detect.Detector;
 import org.apache.tika.exception.TikaConfigException;
+import org.apache.tika.parser.Parser;
 import org.apache.tika.utils.ServiceLoaderUtils;
 
 /**
  * Internal utility class that Tika uses to look up service providers.
+ * Supports both static service loading using the {@link ServiceLoader} mechanism (and via
+ * <a href="https://docs.osgi.org/specification/osgi.cmpn/7.0.0/service.loader.html">OSGi Service Loader Mediator</a>) 
+ * as well as dynamic loading via OSGi service tracking (from the {@link TikaActivator} class).
+ * However the Tika parsers don't register as regular OSGi services, 
+ * so the dynamic loading is only used for detectors and parser services from non-Tika bundles.
  *
  * @since Apache Tika 0.9
  */
+@ServiceConsumer(Parser.class)
+@ServiceConsumer(Detector.class)
 public class ServiceLoader {
 
     /**

tika-parent/pom.xml

@@ -283,6 +283,7 @@
 
   <properties>
     <revision>4.0.0-SNAPSHOT</revision>
+    <javaVersion>17</javaVersion>
     <maven.compiler.source>17</maven.compiler.source>
     <maven.compiler.target>17</maven.compiler.target>
     <maven.compiler.release>17</maven.compiler.release>
@@ -1462,6 +1463,20 @@
         <groupId>org.apache.felix</groupId>
         <artifactId>maven-bundle-plugin</artifactId>
         <version>${maven.bundle.version}</version>
+        <configuration>
+            <instructions>
+              <!-- https://bnd.bndtools.org/instructions/metainf_services.html -->
+              <_metainf-services>auto</_metainf-services>
+            </instructions>
+        </configuration>
+        <dependencies>
+            <!-- upgrade to a newer version of Bnd to leverage https://bnd.bndtools.org/chapters/230-manifest-annotations.html#meta-infservices-annotations -->
+            <dependency>
+                <groupId>biz.aQute.bnd</groupId>
+                <artifactId>biz.aQute.bndlib</artifactId>
+                <version>${biz.aqute.version}</version>
+            </dependency>
+        </dependencies>
       </plugin>
       <plugin>
         <groupId>org.apache.maven.plugins</groupId>