Implement Environment Variable Context Propagation carriers in api/incubator

Author: Bhagirath00

api/incubator/src/main/java/io/opentelemetry/api/incubator/propagation/EnvironmentGetter.java

@@ -0,0 +1,47 @@
+/*
+ * Copyright The OpenTelemetry Authors
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+package io.opentelemetry.api.incubator.propagation;
+
+import io.opentelemetry.context.propagation.TextMapGetter;
+import java.util.Collections;
+import java.util.Locale;
+import java.util.Map;
+import javax.annotation.Nullable;
+
+/**
+ * A {@link TextMapGetter} that extracts context from a map carrier, intended for use with
+ * environment variables.
+ *
+ * <p>Standard environment variable names are uppercase (e.g., {@code TRACEPARENT}, {@code
+ * TRACESTATE}, {@code BAGGAGE}). This getter translates keys to uppercase before looking them up in
+ * the carrier.
+ */
+public enum EnvironmentGetter implements TextMapGetter<Map<String, String>> {
+  INSTANCE;
+
+  @Override
+  public Iterable<String> keys(Map<String, String> carrier) {
+    if (carrier == null) {
+      return Collections.emptyList();
+    }
+    return carrier.keySet();
+  }
+
+  @Nullable
+  @Override
+  public String get(@Nullable Map<String, String> carrier, String key) {
+    if (carrier == null || key == null) {
+      return null;
+    }
+    // Spec recommends using uppercase for environment variable names.
+    return carrier.get(key.toUpperCase(Locale.ROOT));
+  }
+
+  @Override
+  public String toString() {
+    return "EnvironmentGetter";
+  }
+}

api/incubator/src/main/java/io/opentelemetry/api/incubator/propagation/EnvironmentSetter.java

@@ -0,0 +1,37 @@
+/*
+ * Copyright The OpenTelemetry Authors
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+package io.opentelemetry.api.incubator.propagation;
+
+import io.opentelemetry.context.propagation.TextMapSetter;
+import java.util.Locale;
+import java.util.Map;
+import javax.annotation.Nullable;
+
+/**
+ * A {@link TextMapSetter} that injects context into a map carrier, intended for use with
+ * environment variables.
+ *
+ * <p>Standard environment variable names are uppercase (e.g., {@code TRACEPARENT}, {@code
+ * TRACESTATE}, {@code BAGGAGE}). This setter translates keys to uppercase before inserting them
+ * into the carrier.
+ */
+public enum EnvironmentSetter implements TextMapSetter<Map<String, String>> {
+  INSTANCE;
+
+  @Override
+  public void set(@Nullable Map<String, String> carrier, String key, String value) {
+    if (carrier == null || key == null || value == null) {
+      return;
+    }
+    // Spec recommends using uppercase for environment variable names.
+    carrier.put(key.toUpperCase(Locale.ROOT), value);
+  }
+
+  @Override
+  public String toString() {
+    return "EnvironmentSetter";
+  }
+}

api/incubator/src/test/java/io/opentelemetry/api/incubator/propagation/EnvironmentGetterTest.java

@@ -0,0 +1,51 @@
+/*
+ * Copyright The OpenTelemetry Authors
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+package io.opentelemetry.api.incubator.propagation;
+
+import static io.opentelemetry.sdk.testing.assertj.OpenTelemetryAssertions.assertThat;
+
+import java.util.Collections;
+import java.util.HashMap;
+import java.util.Map;
+import org.junit.jupiter.api.Test;
+
+class EnvironmentGetterTest {
+
+  @Test
+  void get() {
+    Map<String, String> carrier = new HashMap<>();
+    carrier.put("TRACEPARENT", "val1");
+    carrier.put("TRACESTATE", "val2");
+    carrier.put("BAGGAGE", "val3");
+    carrier.put("OTHER", "val4");
+
+    assertThat(EnvironmentGetter.INSTANCE.get(carrier, "traceparent")).isEqualTo("val1");
+    assertThat(EnvironmentGetter.INSTANCE.get(carrier, "TRACESTATE")).isEqualTo("val2");
+    assertThat(EnvironmentGetter.INSTANCE.get(carrier, "Baggage")).isEqualTo("val3");
+    assertThat(EnvironmentGetter.INSTANCE.get(carrier, "other")).isEqualTo("val4");
+  }
+
+  @Test
+  void get_null() {
+    assertThat(EnvironmentGetter.INSTANCE.get(null, "key")).isNull();
+    assertThat(EnvironmentGetter.INSTANCE.get(Collections.emptyMap(), null)).isNull();
+  }
+
+  @Test
+  void keys() {
+    Map<String, String> carrier = new HashMap<>();
+    carrier.put("K1", "V1");
+    carrier.put("K2", "V2");
+
+    assertThat(EnvironmentGetter.INSTANCE.keys(carrier)).containsExactlyInAnyOrder("K1", "K2");
+    assertThat(EnvironmentGetter.INSTANCE.keys(null)).isEmpty();
+  }
+
+  @Test
+  void testToString() {
+    assertThat(EnvironmentGetter.INSTANCE.toString()).isEqualTo("EnvironmentGetter");
+  }
+}

api/incubator/src/test/java/io/opentelemetry/api/incubator/propagation/EnvironmentSetterTest.java

@@ -0,0 +1,41 @@
+/*
+ * Copyright The OpenTelemetry Authors
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+package io.opentelemetry.api.incubator.propagation;
+
+import static io.opentelemetry.sdk.testing.assertj.OpenTelemetryAssertions.assertThat;
+
+import java.util.HashMap;
+import java.util.Map;
+import org.junit.jupiter.api.Test;
+
+class EnvironmentSetterTest {
+
+  @Test
+  void set() {
+    Map<String, String> carrier = new HashMap<>();
+    EnvironmentSetter.INSTANCE.set(carrier, "traceparent", "val1");
+    EnvironmentSetter.INSTANCE.set(carrier, "TRACESTATE", "val2");
+    EnvironmentSetter.INSTANCE.set(carrier, "Baggage", "val3");
+
+    assertThat(carrier).containsEntry("TRACEPARENT", "val1");
+    assertThat(carrier).containsEntry("TRACESTATE", "val2");
+    assertThat(carrier).containsEntry("BAGGAGE", "val3");
+  }
+
+  @Test
+  void set_null() {
+    Map<String, String> carrier = new HashMap<>();
+    EnvironmentSetter.INSTANCE.set(null, "key", "val");
+    EnvironmentSetter.INSTANCE.set(carrier, null, "val");
+    EnvironmentSetter.INSTANCE.set(carrier, "key", null);
+    assertThat(carrier).isEmpty();
+  }
+
+  @Test
+  void testToString() {
+    assertThat(EnvironmentSetter.INSTANCE.toString()).isEqualTo("EnvironmentSetter");
+  }
+}