Add a few missing @nullables in instrumentation-api (#3806)

instrumentation-api/src/main/java/io/opentelemetry/instrumentation/api/db/SqlStatementSanitizer.java

@@ -10,6 +10,7 @@
 
 import io.opentelemetry.instrumentation.api.caching.Cache;
 import io.opentelemetry.instrumentation.api.internal.SupportabilityMetrics;
+import org.checkerframework.checker.nullness.qual.Nullable;
 
 /**
  * This class is responsible for masking potentially sensitive parameters in SQL (and SQL-like)
@@ -21,7 +22,7 @@ public final class SqlStatementSanitizer {
   private static final Cache<String, SqlStatementInfo> sqlToStatementInfoCache =
       Cache.newBuilder().setMaximumSize(1000).build();
 
-  public static SqlStatementInfo sanitize(String statement) {
+  public static SqlStatementInfo sanitize(@Nullable String statement) {
     if (!isStatementSanitizationEnabled() || statement == null) {
       return SqlStatementInfo.create(statement, null, null);
     }

instrumentation-api/src/main/java/io/opentelemetry/instrumentation/api/instrumenter/AttributesExtractor.java

@@ -42,7 +42,8 @@ protected abstract void onEnd(
    * Sets the {@code value} with the given {@code key} to the {@link AttributesBuilder} if {@code
    * value} is not {@code null}.
    */
-  protected static <T> void set(AttributesBuilder attributes, AttributeKey<T> key, T value) {
+  protected static <T> void set(
+      AttributesBuilder attributes, AttributeKey<T> key, @Nullable T value) {
     if (value != null) {
       attributes.put(key, value);
     }

instrumentation-api/src/main/java/io/opentelemetry/instrumentation/api/instrumenter/EndTimeExtractor.java

@@ -6,6 +6,7 @@
 package io.opentelemetry.instrumentation.api.instrumenter;
 
 import java.time.Instant;
+import org.checkerframework.checker.nullness.qual.Nullable;
 
 /**
  * Extractor of the end time of response processing. An {@link EndTimeExtractor} should always use
@@ -16,5 +17,5 @@
 public interface EndTimeExtractor<RESPONSE> {
 
   /** Returns the timestamp marking the end of the response processing. */
-  Instant extract(RESPONSE response);
+  Instant extract(@Nullable RESPONSE response);
 }

instrumentation-api/src/main/java/io/opentelemetry/instrumentation/api/instrumenter/code/CodeSpanNameExtractor.java

@@ -7,6 +7,7 @@
 
 import io.opentelemetry.instrumentation.api.instrumenter.SpanNameExtractor;
 import io.opentelemetry.instrumentation.api.tracer.ClassNames;
+import org.checkerframework.checker.nullness.qual.Nullable;
 
 /**
  * A helper {@link SpanNameExtractor} implementation for instrumentations that target specific Java
@@ -37,7 +38,7 @@ public String extract(REQUEST request) {
     return className + "." + methodName;
   }
 
-  private static String defaultString(String s) {
+  private static String defaultString(@Nullable String s) {
     return s == null ? "<unknown>" : s;
   }
 }

instrumentation-api/src/main/java/io/opentelemetry/instrumentation/api/instrumenter/rpc/RpcAttributesExtractor.java

@@ -30,7 +30,8 @@ protected final void onStart(AttributesBuilder attributes, REQUEST request) {
   }
 
   @Override
-  protected final void onEnd(AttributesBuilder attributes, REQUEST request, RESPONSE response) {
+  protected final void onEnd(
+      AttributesBuilder attributes, REQUEST request, @Nullable RESPONSE response) {
     // No response attributes
   }
 

instrumentation-api/src/main/java/io/opentelemetry/instrumentation/api/internal/ContextPropagationDebug.java

@@ -12,6 +12,7 @@
 import java.util.Iterator;
 import java.util.List;
 import java.util.concurrent.CopyOnWriteArrayList;
+import org.checkerframework.checker.nullness.qual.Nullable;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
@@ -68,6 +69,7 @@ public static void debugContextLeakIfEnabled() {
     }
   }
 
+  @Nullable
   private static List<Propagation> getPropagations(Context context) {
     return context.get(THREAD_PROPAGATION_LOCATIONS);
   }