Revert "customizers are sufficient"

This reverts commit 1a867b1.

Author: zeitlinger

docs/apidiffs/current_vs_latest/opentelemetry-sdk-extension-autoconfigure.txt

@@ -2,12 +2,14 @@ Comparing source compatibility of  against
 ***  MODIFIED CLASS: PUBLIC FINAL io.opentelemetry.sdk.autoconfigure.AutoConfiguredOpenTelemetrySdkBuilder  (not serializable)
 	===  CLASS FILE FORMAT VERSION: 52.0 <- 52.0
 	+++  NEW METHOD: PUBLIC(+) io.opentelemetry.sdk.autoconfigure.AutoConfiguredOpenTelemetrySdkBuilder setComponentLoader(io.opentelemetry.sdk.autoconfigure.ComponentLoader)
-+++  NEW INTERFACE: PUBLIC(+) ABSTRACT(+) io.opentelemetry.sdk.autoconfigure.ComponentLoader  (not serializable)
++++* NEW INTERFACE: PUBLIC(+) ABSTRACT(+) io.opentelemetry.sdk.autoconfigure.ComponentLoader  (not serializable)
 	+++  CLASS FILE FORMAT VERSION: 52.0 <- n.a.
 	+++  NEW SUPERCLASS: java.lang.Object
-	+++  NEW METHOD: PUBLIC(+) ABSTRACT(+) java.lang.Iterable<T> load(java.lang.Class<T>)
+	+++* NEW METHOD: PUBLIC(+) ABSTRACT(+) java.lang.Iterable<T> load(java.lang.Class<T>)
 		GENERIC TEMPLATES: +++ T:java.lang.Object
-	+++  NEW METHOD: PUBLIC(+) java.util.Map<java.lang.String,T> loadConfigurableProviders(java.lang.Class<T>)
+	+++* NEW METHOD: PUBLIC(+) java.util.Map<java.lang.String,T> loadConfigurableProviders(java.lang.Class<T>)
 		GENERIC TEMPLATES: +++ T:io.opentelemetry.sdk.autoconfigure.spi.ConfigurableProvider
-	+++  NEW METHOD: PUBLIC(+) java.util.List<T> loadOrdered(java.lang.Class<T>)
+	+++* NEW METHOD: PUBLIC(+) java.util.Optional<T> loadOptional(java.lang.Class<T>)
+		GENERIC TEMPLATES: +++ T:java.lang.Object
+	+++* NEW METHOD: PUBLIC(+) java.util.List<T> loadOrdered(java.lang.Class<T>)
 		GENERIC TEMPLATES: +++ T:io.opentelemetry.sdk.autoconfigure.spi.Ordered

sdk-extensions/autoconfigure/src/main/java/io/opentelemetry/sdk/autoconfigure/ComponentLoader.java

@@ -11,13 +11,19 @@
 import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
+import java.util.Optional;
 import java.util.stream.Collectors;
 import java.util.stream.StreamSupport;
 
 /** A loader for components that are discovered via SPI. */
 public interface ComponentLoader {
   <T> Iterable<T> load(Class<T> spiClass);
 
+  default <T> Optional<T> loadOptional(Class<T> spiClass) {
+    Iterable<T> iterable = load(spiClass);
+    return StreamSupport.stream(iterable.spliterator(), false).findFirst();
+  }
+
   /**
    * Load implementations of an ordered SPI (i.e. implements {@link Ordered}).
    *

sdk-extensions/autoconfigure/src/main/java/io/opentelemetry/sdk/autoconfigure/internal/SpiHelper.java

@@ -16,6 +16,7 @@
 import java.util.IdentityHashMap;
 import java.util.List;
 import java.util.Map;
+import java.util.Optional;
 import java.util.ServiceLoader;
 import java.util.Set;
 import java.util.function.BiFunction;
@@ -109,6 +110,10 @@ private <T> List<T> init(Iterable<T> components) {
     return result;
   }
 
+  public <T> Optional<T> loadOptional(Class<T> spiClass) {
+    return componentLoader.loadOptional(spiClass).map(this::maybeAddListener);
+  }
+
   private <T> T maybeAddListener(T object) {
     if (object instanceof AutoConfigureListener) {
       listeners.add((AutoConfigureListener) object);