[Prototype] How to support complex attributes in logs/events? (Option B)

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

@@ -65,4 +65,9 @@ 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 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

@@ -14,6 +14,7 @@
 import static io.opentelemetry.api.common.AttributeKey.longKey;
 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;
@@ -86,6 +87,21 @@ default AttributesBuilder put(String key, boolean value) {
     return put(booleanKey(key), value);
   }
 
+  /**
+   * Puts a {@link Value} attribute into this.
+   *
+   * <p>Note: It is strongly recommended to use {@link #put(AttributeKey, Object)}, and pre-allocate
+   * your keys, if possible.
+   *
+   * <p>IMPORTANT: {@link Value} attributes are only supported by Logs. Spans and Metrics do not
+   * support {@link Value} attributes.
+   *
+   * @return this Builder
+   */
+  default AttributesBuilder put(String key, Value<?> value) {
+    return put(valueKey(key), value);
+  }
+
   /**
    * Puts a String array attribute into this.
    *

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

@@ -115,4 +115,8 @@ static Value<List<KeyValue>> of(Map<String, Value<?>> value) {
    */
   // TODO(jack-berg): Should this be a JSON encoding?
   String asString();
+
+  static ValueBuilder builder() {
+    return new ValueBuilderImpl();
+  }
 }

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

@@ -0,0 +1,63 @@
+/*
+ * Copyright The OpenTelemetry Authors
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+package io.opentelemetry.api.common;
+
+import static java.util.stream.Collectors.toList;
+
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.List;
+
+public interface ValueBuilder {
+
+  Value<?> build();
+
+  ValueBuilder put(String key, Value<?> value);
+
+  default ValueBuilder put(String key, String value) {
+    put(key, Value.of(value));
+    return this;
+  }
+
+  default ValueBuilder put(String key, long value) {
+    put(key, Value.of(value));
+    return this;
+  }
+
+  default ValueBuilder put(String key, double value) {
+    put(key, Value.of(value));
+    return this;
+  }
+
+  default ValueBuilder put(String key, boolean value) {
+    put(key, Value.of(value));
+    return this;
+  }
+
+  default ValueBuilder put(String key, String... value) {
+    put(key, Value.of(Arrays.stream(value).map(Value::of).collect(toList())));
+    return this;
+  }
+
+  default ValueBuilder put(String key, long... value) {
+    put(key, Value.of(Arrays.stream(value).mapToObj(Value::of).collect(toList())));
+    return this;
+  }
+
+  default ValueBuilder put(String key, double... value) {
+    put(key, Value.of(Arrays.stream(value).mapToObj(Value::of).collect(toList())));
+    return this;
+  }
+
+  default ValueBuilder put(String key, boolean... value) {
+    List<Value<?>> values = new ArrayList<>(value.length);
+    for (boolean val : value) {
+      values.add(Value.of(val));
+    }
+    put(key, Value.of(values));
+    return this;
+  }
+}

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

@@ -0,0 +1,20 @@
+package io.opentelemetry.api.common;
+
+import java.util.ArrayList;
+import java.util.List;
+
+class ValueBuilderImpl implements ValueBuilder {
+
+  private final List<KeyValue> keyValues = new ArrayList<>();
+
+  @Override
+  public ValueBuilder put(String key, Value<?> value) {
+    keyValues.add(KeyValue.of(key, value));
+    return this;
+  }
+
+  @Override
+  public Value<?> build() {
+    return Value.of(keyValues.toArray(new KeyValue[0]));
+  }
+}