Split SpanContext into interface / impl

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

@@ -0,0 +1,51 @@
+/*
+ * Copyright The OpenTelemetry Authors
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+package io.opentelemetry.api.trace;
+
+import com.google.auto.value.AutoValue;
+import com.google.auto.value.extension.memoized.Memoized;
+import javax.annotation.concurrent.Immutable;
+
+@Immutable
+@AutoValue
+abstract class ImmutableSpanContext implements SpanContext {
+
+  private static final SpanContext INVALID =
+      create(
+          TraceId.getInvalid(),
+          SpanId.getInvalid(),
+          TraceFlags.getDefault(),
+          TraceState.getDefault(),
+          /* remote= */ false);
+
+  static SpanContext getInvalid() {
+    return INVALID;
+  }
+
+  static SpanContext create(
+      String traceIdHex, String spanIdHex, byte traceFlags, TraceState traceState, boolean remote) {
+    return new AutoValue_ImmutableSpanContext(
+        traceIdHex, spanIdHex, traceFlags, traceState, remote);
+  }
+
+  @Override
+  @Memoized
+  public byte[] getTraceIdBytes() {
+    return SpanContext.super.getTraceIdBytes();
+  }
+
+  @Override
+  @Memoized
+  public byte[] getSpanIdBytes() {
+    return SpanContext.super.getSpanIdBytes();
+  }
+
+  @Override
+  @Memoized
+  public boolean isValid() {
+    return SpanContext.super.isValid();
+  }
+}

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

@@ -5,8 +5,6 @@
 
 package io.opentelemetry.api.trace;
 
-import com.google.auto.value.AutoValue;
-import com.google.auto.value.extension.memoized.Memoized;
 import javax.annotation.concurrent.Immutable;
 
 /**
@@ -15,25 +13,24 @@
  * trace_id} and {@link SpanId span_id}) associated with the {@link Span} and a set of options
  * (currently only whether the context is sampled or not), as well as the {@link TraceState
  * traceState} and the {@link boolean remote} flag.
+ *
+ * <p>Implementations of this interface *must* be immutable and have well-defined value-based
+ * equals/hashCode implementations. If an implementation does not strictly conform to these
+ * requirements, behavior of the OpenTelemetry APIs and default SDK cannot be guaranteed. It is
+ * strongly suggested that you use the implementation that is provided here via {@link
+ * #create(String, String, byte, TraceState)} or {@link #createFromRemoteParent(String, String,
+ * byte, TraceState)}.
  */
 @Immutable
-@AutoValue
-public abstract class SpanContext {
-
-  private static final SpanContext INVALID =
-      create(
-          TraceId.getInvalid(),
-          SpanId.getInvalid(),
-          TraceFlags.getDefault(),
-          TraceState.getDefault());
+public interface SpanContext {
 
   /**
    * Returns the invalid {@code SpanContext} that can be used for no-op operations.
    *
    * @return the invalid {@code SpanContext}.
    */
-  public static SpanContext getInvalid() {
-    return INVALID;
+  static SpanContext getInvalid() {
+    return ImmutableSpanContext.getInvalid();
   }
 
   /**
@@ -45,15 +42,10 @@ public static SpanContext getInvalid() {
    * @param traceState the trace state for the span context.
    * @return a new {@code SpanContext} with the given identifiers and options.
    */
-  public static SpanContext create(
+  static SpanContext create(
       String traceIdHex, String spanIdHex, byte traceFlags, TraceState traceState) {
-    return create(traceIdHex, spanIdHex, traceFlags, traceState, /* remote=*/ false);
-  }
-
-  private static SpanContext create(
-      String traceIdHex, String spanIdHex, byte traceFlags, TraceState traceState, boolean remote) {
-    return new AutoValue_SpanContext(
-        traceIdHex, spanIdHex, traceFlags, traceState, /* remote$=*/ remote);
+    return ImmutableSpanContext.create(
+        traceIdHex, spanIdHex, traceFlags, traceState, /* remote=*/ false);
   }
 
   /**
@@ -66,60 +58,51 @@ private static SpanContext create(
    * @param traceState the trace state for the span context.
    * @return a new {@code SpanContext} with the given identifiers and options.
    */
-  public static SpanContext createFromRemoteParent(
+  static SpanContext createFromRemoteParent(
       String traceIdHex, String spanIdHex, byte traceFlags, TraceState traceState) {
-    return create(traceIdHex, spanIdHex, traceFlags, traceState, /* remote=*/ true);
+    return ImmutableSpanContext.create(
+        traceIdHex, spanIdHex, traceFlags, traceState, /* remote=*/ true);
   }
 
-  abstract String getTraceIdHex();
-
-  abstract String getSpanIdHex();
-
   /**
    * Returns the trace identifier associated with this {@code SpanContext}.
    *
    * @return the trace identifier associated with this {@code SpanContext}.
    */
-  public String getTraceIdAsHexString() {
-    return getTraceIdHex();
-  }
+  String getTraceIdAsHexString();
 
   /**
    * Returns the byte[] representation of the trace identifier associated with this {@link
    * SpanContext}.
    */
-  @Memoized
-  public byte[] getTraceIdBytes() {
-    return TraceId.bytesFromHex(getTraceIdHex(), 0);
+  default byte[] getTraceIdBytes() {
+    return TraceId.bytesFromHex(getTraceIdAsHexString(), 0);
   }
 
   /**
    * Returns the span identifier associated with this {@code SpanContext}.
    *
    * @return the span identifier associated with this {@code SpanContext}.
    */
-  public String getSpanIdAsHexString() {
-    return getSpanIdHex();
-  }
+  String getSpanIdAsHexString();
 
   /**
    * Returns the byte[] representation of the span identifier associated with this {@link
    * SpanContext}.
    */
-  @Memoized
-  public byte[] getSpanIdBytes() {
-    return SpanId.bytesFromHex(getSpanIdHex(), 0);
+  default byte[] getSpanIdBytes() {
+    return SpanId.bytesFromHex(getSpanIdAsHexString(), 0);
   }
 
   /** Whether the span in this context is sampled. */
-  public boolean isSampled() {
+  default boolean isSampled() {
     return (getTraceFlags() & 1) == 1;
   }
 
   /** The byte-representation of {@link TraceFlags}. */
-  public abstract byte getTraceFlags();
+  byte getTraceFlags();
 
-  public void copyTraceFlagsHexTo(char[] dest, int destOffset) {
+  default void copyTraceFlagsHexTo(char[] dest, int destOffset) {
     BigendianEncoding.byteToBase16String(getTraceFlags(), dest, destOffset);
   }
 
@@ -128,22 +111,21 @@ public void copyTraceFlagsHexTo(char[] dest, int destOffset) {
    *
    * @return the {@code TraceState} associated with this {@code SpanContext}.
    */
-  public abstract TraceState getTraceState();
+  TraceState getTraceState();
 
   /**
    * Returns {@code true} if this {@code SpanContext} is valid.
    *
    * @return {@code true} if this {@code SpanContext} is valid.
    */
-  @Memoized
-  public boolean isValid() {
-    return TraceId.isValid(getTraceIdHex()) && SpanId.isValid(getSpanIdHex());
+  default boolean isValid() {
+    return TraceId.isValid(getTraceIdAsHexString()) && SpanId.isValid(getSpanIdAsHexString());
   }
 
   /**
    * Returns {@code true} if the {@code SpanContext} was propagated from a remote parent.
    *
    * @return {@code true} if the {@code SpanContext} was propagated from a remote parent.
    */
-  public abstract boolean isRemote();
+  boolean isRemote();
 }