Initial relocation of ContextUtils classes. (open-telemetry#904)

* Initial relocation of ContextUtils classes.

Now they will live within the child `propagation` package,
with a prefix based on their cross-cutting concern, to be
referenced easily.

api/src/main/java/io/opentelemetry/correlationcontext/CorrelationsContextUtils.java

@@ -0,0 +1,99 @@
+/*
+ * Copyright 2019, OpenTelemetry Authors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package io.opentelemetry.correlationcontext;
+
+import io.grpc.Context;
+import io.opentelemetry.context.ContextUtils;
+import io.opentelemetry.context.Scope;
+import javax.annotation.Nullable;
+import javax.annotation.concurrent.Immutable;
+
+/**
+ * Utility methods for accessing the {@link CorrelationContext} contained in the {@link
+ * io.grpc.Context}.
+ *
+ * @since 0.1.0
+ */
+@Immutable
+public final class CorrelationsContextUtils {
+  private static final Context.Key<CorrelationContext> CORR_CONTEXT_KEY =
+      Context.key("opentelemetry-corr-context-key");
+
+  /**
+   * Creates a new {@code Context} with the given value set.
+   *
+   * @param corrContext the value to be set.
+   * @param context the parent {@code Context}.
+   * @return a new context with the given value set.
+   * @since 0.1.0
+   */
+  public static Context withCorrelationContext(CorrelationContext corrContext, Context context) {
+    return context.withValue(CORR_CONTEXT_KEY, corrContext);
+  }
+
+  /**
+   * Returns the {@link CorrelationContext} from the current {@code Context}, falling back to an
+   * empty {@link CorrelationContext}.
+   *
+   * @return the {@link CorrelationContext} from the current {@code Context}.
+   * @since 0.3.0
+   */
+  public static CorrelationContext getCurrentCorrelationContext() {
+    return getCorrelationContext(Context.current());
+  }
+
+  /**
+   * Returns the {@link CorrelationContext} from the specified {@code Context}, falling back to an
+   * empty {@link CorrelationContext}.
+   *
+   * @param context the specified {@code Context}.
+   * @return the {@link CorrelationContext} from the specified {@code Context}.
+   * @since 0.3.0
+   */
+  public static CorrelationContext getCorrelationContext(Context context) {
+    CorrelationContext corrContext = CORR_CONTEXT_KEY.get(context);
+    return corrContext == null ? EmptyCorrelationContext.getInstance() : corrContext;
+  }
+
+  /**
+   * Returns the {@link CorrelationContext} from the specified {@code Context}. If none is found,
+   * this method returns {code null}.
+   *
+   * @param context the specified {@code Context}.
+   * @return the {@link CorrelationContext} from the specified {@code Context}.
+   * @since 0.1.0
+   */
+  @Nullable
+  public static CorrelationContext getCorrelationContextWithoutDefault(Context context) {
+    return CORR_CONTEXT_KEY.get(context);
+  }
+
+  /**
+   * Returns a new {@link Scope} encapsulating the provided {@link CorrelationContext} added to the
+   * current {@code Context}.
+   *
+   * @param corrContext the {@link CorrelationContext} to be added to the current {@code Context}.
+   * @return the {@link Scope} for the updated {@code Context}.
+   * @since 0.1.0
+   */
+  public static Scope withScopedCorrelationContext(CorrelationContext corrContext) {
+    Context context = withCorrelationContext(corrContext, Context.current());
+    return ContextUtils.withScopedContext(context);
+  }
+
+  private CorrelationsContextUtils() {}
+}

api/src/main/java/io/opentelemetry/correlationcontext/DefaultCorrelationContextManager.java

@@ -18,7 +18,6 @@
 
 import io.opentelemetry.context.Scope;
 import io.opentelemetry.context.propagation.HttpTextFormat;
-import io.opentelemetry.correlationcontext.unsafe.ContextUtils;
 import io.opentelemetry.internal.Utils;
 import java.util.Collections;
 import java.util.List;
@@ -50,7 +49,7 @@ public static CorrelationContextManager getInstance() {
 
   @Override
   public CorrelationContext getCurrentContext() {
-    return ContextUtils.getValue();
+    return CorrelationsContextUtils.getCurrentCorrelationContext();
   }
 
   @Override
@@ -60,7 +59,7 @@ public CorrelationContext.Builder contextBuilder() {
 
   @Override
   public Scope withContext(CorrelationContext distContext) {
-    return ContextUtils.withCorrelationContext(distContext);
+    return CorrelationsContextUtils.withScopedCorrelationContext(distContext);
   }
 
   @Override

api/src/main/java/io/opentelemetry/trace/DefaultTracer.java

@@ -20,7 +20,6 @@
 import io.opentelemetry.context.propagation.HttpTextFormat;
 import io.opentelemetry.internal.Utils;
 import io.opentelemetry.trace.propagation.HttpTraceContext;
-import io.opentelemetry.trace.unsafe.ContextUtils;
 import java.util.Map;
 import javax.annotation.concurrent.ThreadSafe;
 
@@ -46,12 +45,12 @@ public static Tracer getInstance() {
 
   @Override
   public Span getCurrentSpan() {
-    return ContextUtils.getValue();
+    return TracingContextUtils.getCurrentSpan();
   }
 
   @Override
   public Scope withSpan(Span span) {
-    return ContextUtils.withSpan(span);
+    return TracingContextUtils.withScopedSpan(span);
   }
 
   @Override

api/src/main/java/io/opentelemetry/trace/TracingContextUtils.java

@@ -0,0 +1,97 @@
+/*
+ * Copyright 2019, OpenTelemetry Authors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package io.opentelemetry.trace;
+
+import io.grpc.Context;
+import io.opentelemetry.context.ContextUtils;
+import io.opentelemetry.context.Scope;
+import javax.annotation.Nullable;
+import javax.annotation.concurrent.Immutable;
+
+/**
+ * Util methods/functionality to interact with the {@link io.grpc.Context}.
+ *
+ * @since 0.1.0
+ */
+@Immutable
+public final class TracingContextUtils {
+  private static final Context.Key<Span> CONTEXT_SPAN_KEY =
+      Context.<Span>key("opentelemetry-trace-span-key");
+
+  /**
+   * Creates a new {@code Context} with the given {@link Span} set.
+   *
+   * @param span the value to be set.
+   * @param context the parent {@code Context}.
+   * @return a new context with the given value set.
+   * @since 0.1.0
+   */
+  public static Context withSpan(Span span, Context context) {
+    return context.withValue(CONTEXT_SPAN_KEY, span);
+  }
+
+  /**
+   * Returns the {@link Span} from the current {@code Context}, falling back to a default, no-op
+   * {@link Span}.
+   *
+   * @return the {@link Span} from the current {@code Context}.
+   * @since 0.3.0
+   */
+  public static Span getCurrentSpan() {
+    return getSpan(Context.current());
+  }
+
+  /**
+   * Returns the {@link Span} from the specified {@code Context}, falling back to a default, no-op
+   * {@link Span}.
+   *
+   * @param context the specified {@code Context}.
+   * @return the {@link Span} from the specified {@code Context}.
+   * @since 0.3.0
+   */
+  public static Span getSpan(Context context) {
+    Span span = CONTEXT_SPAN_KEY.get(context);
+    return span == null ? DefaultSpan.getInvalid() : span;
+  }
+
+  /**
+   * Returns the {@link Span} from the specified {@code Context}. If none is found, this method
+   * returns {code null}.
+   *
+   * @param context the specified {@code Context}.
+   * @return the {@link Span} from the specified {@code Context}.
+   * @since 0.1.0
+   */
+  @Nullable
+  public static Span getSpanWithoutDefault(Context context) {
+    return CONTEXT_SPAN_KEY.get(context);
+  }
+
+  /**
+   * Returns a new {@link Scope} encapsulating the provided {@link Span} added to the current {@code
+   * Context}.
+   *
+   * @param span the {@link Span} to be added to the current {@code Context}.
+   * @return the {@link Scope} for the updated {@code Context}.
+   * @since 0.1.0
+   */
+  public static Scope withScopedSpan(Span span) {
+    return ContextUtils.withScopedContext(withSpan(span, Context.current()));
+  }
+
+  private TracingContextUtils() {}
+}