Prototype: Complex attributes (Option C - minimal)

Author: trask

api/all/src/main/java/io/opentelemetry/api/common/AttributeKey.java

@@ -70,4 +70,9 @@ static AttributeKey<List<Long>> longArrayKey(String key) {
   static AttributeKey<List<Double>> doubleArrayKey(String key) {
     return InternalAttributeKeyImpl.create(key, AttributeType.DOUBLE_ARRAY);
   }
+
+  /** Returns a new AttributeKey for generic {@link Value} valued attributes. */
+  static AttributeKey<Value<?>> valueKey(String key) {
+    return InternalAttributeKeyImpl.create(key, AttributeType.VALUE);
+  }
 }

api/all/src/main/java/io/opentelemetry/api/common/AttributeType.java

@@ -17,5 +17,6 @@ public enum AttributeType {
   STRING_ARRAY,
   BOOLEAN_ARRAY,
   LONG_ARRAY,
-  DOUBLE_ARRAY
+  DOUBLE_ARRAY,
+  VALUE
 }

api/all/src/main/java/io/opentelemetry/api/common/AttributesBuilder.java

@@ -12,8 +12,11 @@
 import static io.opentelemetry.api.common.AttributeKey.doubleKey;
 import static io.opentelemetry.api.common.AttributeKey.longArrayKey;
 import static io.opentelemetry.api.common.AttributeKey.longKey;
+import static io.opentelemetry.api.common.AttributeKey.mapArrayKey;
+import static io.opentelemetry.api.common.AttributeKey.mapKey;
 import static io.opentelemetry.api.common.AttributeKey.stringArrayKey;
 import static io.opentelemetry.api.common.AttributeKey.stringKey;
+import static io.opentelemetry.api.common.AttributeKey.valueKey;
 
 import java.util.Arrays;
 import java.util.List;
@@ -164,6 +167,21 @@ default AttributesBuilder put(String key, boolean... value) {
     return put(booleanArrayKey(key), toList(value));
   }
 
+  /**
+   * Puts a generic ({@link Value}) attribute into this.
+   *
+   * <p>Note: It is strongly recommended to use {@link #put(AttributeKey, Object)}, and pre-allocate
+   * your keys, if possible.
+   *
+   * @return this Builder
+   */
+  default AttributesBuilder put(String key, Value<?> value) {
+    if (value == null) {
+      return this;
+    }
+    return put(valueKey(key), value);
+  }
+
   /**
    * Puts all the provided attributes into this Builder.
    *