Add Labels.asMap and hide the builder implementation. (#2189)

* Add Labels.asMap and hide the builder implementation.

* Not public

* Spot

* More merge

api/common/src/main/java/io/opentelemetry/api/common/ArrayBackedLabels.java

@@ -0,0 +1,44 @@
+/*
+ * Copyright The OpenTelemetry Authors
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+package io.opentelemetry.api.common;
+
+import com.google.auto.value.AutoValue;
+import io.opentelemetry.api.internal.ImmutableKeyValuePairs;
+import java.util.List;
+import java.util.function.BiConsumer;
+import javax.annotation.concurrent.Immutable;
+
+@AutoValue
+@Immutable
+abstract class ArrayBackedLabels extends ImmutableKeyValuePairs<String, String> implements Labels {
+  private static final Labels EMPTY = Labels.builder().build();
+
+  static Labels empty() {
+    return EMPTY;
+  }
+
+  ArrayBackedLabels() {}
+
+  @Override
+  protected abstract List<Object> data();
+
+  @Override
+  public void forEach(BiConsumer<String, String> consumer) {
+    List<Object> data = data();
+    for (int i = 0; i < data.size(); i += 2) {
+      consumer.accept((String) data.get(i), (String) data.get(i + 1));
+    }
+  }
+
+  static Labels sortAndFilterToLabels(Object... data) {
+    return new AutoValue_ArrayBackedLabels(sortAndFilter(data, /* filterNullValues= */ false));
+  }
+
+  @Override
+  public LabelsBuilder toBuilder() {
+    return new ArrayBackedLabelsBuilder(data());
+  }
+}

api/common/src/main/java/io/opentelemetry/api/common/ArrayBackedLabelsBuilder.java

@@ -21,7 +21,7 @@ class ArrayBackedLabelsBuilder implements LabelsBuilder {
 
   @Override
   public Labels build() {
-    return Labels.ArrayBackedLabels.sortAndFilterToLabels(data.toArray());
+    return ArrayBackedLabels.sortAndFilterToLabels(data.toArray());
   }
 
   @Override

api/common/src/main/java/io/opentelemetry/api/common/Labels.java

@@ -5,11 +5,9 @@
 
 package io.opentelemetry.api.common;
 
-import static io.opentelemetry.api.common.Labels.ArrayBackedLabels.sortAndFilterToLabels;
+import static io.opentelemetry.api.common.ArrayBackedLabels.sortAndFilterToLabels;
 
-import com.google.auto.value.AutoValue;
-import io.opentelemetry.api.internal.ImmutableKeyValuePairs;
-import java.util.List;
+import java.util.Map;
 import java.util.function.BiConsumer;
 import javax.annotation.Nullable;
 import javax.annotation.concurrent.Immutable;
@@ -27,52 +25,14 @@ import javax.annotation.concurrent.Immutable;
 @Immutable
 public interface Labels {
 
-  /** Iterates over all the key-value pairs of labels contained by this instance. */
-  void forEach(BiConsumer<String, String> consumer);
-
-  /** The number of key-value pairs of labels in this instance. */
-  int size();
-
-  /** Returns the value for the given {@code key}, or {@code null} if the key is not present. */
-  @Nullable
-  String get(String key);
-
-  /** Returns whether this instance is empty (contains no labels). */
-  boolean isEmpty();
-
-  @AutoValue
-  @Immutable
-  abstract class ArrayBackedLabels extends ImmutableKeyValuePairs<String, String>
-      implements Labels {
-    private static final Labels EMPTY = Labels.builder().build();
-
-    ArrayBackedLabels() {}
-
-    @Override
-    protected abstract List<Object> data();
-
-    @Override
-    public void forEach(BiConsumer<String, String> consumer) {
-      List<Object> data = data();
-      for (int i = 0; i < data.size(); i += 2) {
-        consumer.accept((String) data.get(i), (String) data.get(i + 1));
-      }
-    }
-
-    static Labels sortAndFilterToLabels(Object... data) {
-      return new AutoValue_Labels_ArrayBackedLabels(
-          sortAndFilter(data, /* filterNullValues= */ false));
-    }
-
-    @Override
-    public LabelsBuilder toBuilder() {
-      return new ArrayBackedLabelsBuilder(data());
-    }
-  }
-
   /** Returns a {@link Labels} instance with no attributes. */
   static Labels empty() {
-    return ArrayBackedLabels.EMPTY;
+    return ArrayBackedLabels.empty();
+  }
+
+  /** Creates a new {@link LabelsBuilder} instance for creating arbitrary {@link Labels}. */
+  static LabelsBuilder builder() {
+    return new ArrayBackedLabelsBuilder();
   }
 
   /** Returns a {@link Labels} instance with a single key-value pair. */
@@ -136,20 +96,27 @@ public interface Labels {
         key5, value5);
   }
 
-  static Labels of(String[] keyValueLabelPairs) {
+  /** Returns a {@link Labels} instance with the provided {@code keyValueLabelPairs}. */
+  static Labels of(String... keyValueLabelPairs) {
     return sortAndFilterToLabels((Object[]) keyValueLabelPairs);
   }
 
-  /**
-   * Create a {@link ArrayBackedLabelsBuilder} pre-populated with the contents of this Labels
-   * instance.
-   */
-  LabelsBuilder toBuilder();
+  /** Iterates over all the key-value pairs of labels contained by this instance. */
+  void forEach(BiConsumer<String, String> consumer);
 
-  /**
-   * Creates a new {@link ArrayBackedLabelsBuilder} instance for creating arbitrary {@link Labels}.
-   */
-  static LabelsBuilder builder() {
-    return new ArrayBackedLabelsBuilder();
-  }
+  /** The number of key-value pairs of labels in this instance. */
+  int size();
+
+  /** Returns the value for the given {@code key}, or {@code null} if the key is not present. */
+  @Nullable
+  String get(String key);
+
+  /** Returns whether this instance is empty (contains no labels). */
+  boolean isEmpty();
+
+  /** Returns a read-only view of these {@link Labels} as a {@link Map}. */
+  Map<String, String> asMap();
+
+  /** Create a {@link LabelsBuilder} pre-populated with the contents of this Labels instance. */
+  LabelsBuilder toBuilder();
 }

api/common/src/test/java/io/opentelemetry/api/common/LabelsTest.java

@@ -29,6 +29,16 @@ class LabelsTest {
     assertThat(entriesSeen).containsExactly(entry("key1", "value1"), entry("key2", "value2"));
   }
 
+  @Test
+  void asMap() {
+    Labels labels =
+        Labels.of(
+            "key1", "value1",
+            "key2", "value2");
+
+    assertThat(labels.asMap()).containsExactly(entry("key1", "value1"), entry("key2", "value2"));
+  }
+
   @Test
   void forEach_singleAttribute() {
     final Map<String, String> entriesSeen = new HashMap<>();