Handle null input in StringEncoder

exporters/common/src/main/java/io/opentelemetry/exporter/internal/marshal/AbstractStringEncoder.java

@@ -6,6 +6,7 @@
 package io.opentelemetry.exporter.internal.marshal;
 
 import java.io.IOException;
+import javax.annotation.Nullable;
 
 /**
  * This class contains shared logic for UTF-8 encoding operations while allowing subclasses to
@@ -20,8 +21,11 @@ abstract class AbstractStringEncoder implements StringEncoder {
   private final FallbackStringEncoder fallback = new FallbackStringEncoder();
 
   @Override
-  public final void writeUtf8(CodedOutputStream output, String string, int utf8Length)
+  public final void writeUtf8(CodedOutputStream output, @Nullable String string, int utf8Length)
       throws IOException {
+    if (string == null) {
+      return;
+    }
     // if the length of the latin1 string and the utf8 output are the same then the string must be
     // composed of only 7bit characters and can be directly copied to the output
     if (string.length() == utf8Length && isLatin1(string)) {
@@ -33,8 +37,10 @@ public final void writeUtf8(CodedOutputStream output, String string, int utf8Len
   }
 
   @Override
-  public final int getUtf8Size(String string) {
-    if (isLatin1(string)) {
+  public final int getUtf8Size(@Nullable String string) {
+    if (string == null) {
+      return 0;
+    } else if (isLatin1(string)) {
       byte[] bytes = getStringBytes(string);
       // latin1 bytes with negative value (most significant bit set) are encoded as 2 bytes in utf8
       return string.length() + countNegative(bytes);

exporters/common/src/main/java/io/opentelemetry/exporter/internal/marshal/FallbackStringEncoder.java

@@ -6,6 +6,7 @@
 package io.opentelemetry.exporter.internal.marshal;
 
 import java.io.IOException;
+import javax.annotation.Nullable;
 
 /**
  * Fallback StringEncoder implementation using standard Java string operations.
@@ -20,14 +21,16 @@ final class FallbackStringEncoder implements StringEncoder {
   FallbackStringEncoder() {}
 
   @Override
-  public int getUtf8Size(String string) {
-    return encodedUtf8Length(string);
+  public int getUtf8Size(@Nullable String string) {
+    return string != null ? encodedUtf8Length(string) : 0;
   }
 
   @Override
-  public void writeUtf8(CodedOutputStream output, String string, int utf8Length)
+  public void writeUtf8(CodedOutputStream output, @Nullable String string, int utf8Length)
       throws IOException {
-    encodeUtf8(output, string);
+    if (string != null) {
+      encodeUtf8(output, string);
+    }
   }
 
   // adapted from

exporters/common/src/main/java/io/opentelemetry/exporter/internal/marshal/StringEncoder.java

@@ -6,6 +6,7 @@
 package io.opentelemetry.exporter.internal.marshal;
 
 import java.io.IOException;
+import javax.annotation.Nullable;
 
 /**
  * Interface for efficient UTF-8 string encoding operations.
@@ -29,13 +30,14 @@
 public interface StringEncoder {
 
   /** Returns the number of bytes required to encode the string as UTF-8. */
-  int getUtf8Size(String string);
+  int getUtf8Size(@Nullable String string);
 
   /**
    * Write a string as UTF-8 bytes to the output stream using the pre-calculated UTF-8 length from
    * {@link #getUtf8Size(String)}.
    */
-  void writeUtf8(CodedOutputStream output, String string, int utf8Length) throws IOException;
+  void writeUtf8(CodedOutputStream output, @Nullable String string, int utf8Length)
+      throws IOException;
 
   /** Returns the best available StringEncoder implementation. */
   static StringEncoder getInstance() {

exporters/common/src/test/java/io/opentelemetry/exporter/internal/marshal/StringEncoderTest.java

@@ -61,6 +61,9 @@ void testUtf8SizeLatin1_VarHandle() {
   private static void testUtf8Encoding(StringEncoder stringEncoder) {
     assertThat(stringEncoder).isNotNull();
 
+    assertThat(stringEncoder.getUtf8Size(null)).isEqualTo(0);
+    assertThat(testUtf8(null, 0, stringEncoder)).isEqualTo("");
+
     assertThat(stringEncoder.getUtf8Size("")).isEqualTo(0);
     assertThat(testUtf8("", 0, stringEncoder)).isEqualTo("");
 
@@ -87,6 +90,8 @@ private static void testUtf8Encoding(StringEncoder stringEncoder) {
   }
 
   private static void testUtf8SizeLatin1(StringEncoder stringEncoder) {
+    assertThat(stringEncoder.getUtf8Size(null)).isEqualTo(0);
+
     // Run repeated test logic for each encoder
     Random random = new Random();
     for (int i = 0; i < 1000; i++) {