Adds '+' character to allowed characters in baggage value

api/all/src/main/java/io/opentelemetry/api/baggage/propagation/Parser.java

@@ -147,12 +147,21 @@ private static String decodeValue(@Nullable String value) {
       return null;
     }
     try {
-      return URLDecoder.decode(value, StandardCharsets.UTF_8.name());
+      return URLDecoder.decode(encodeAllowedCharacters(value), StandardCharsets.UTF_8.name());
     } catch (UnsupportedEncodingException e) {
       return null;
     }
   }
 
+  /**
+   * Encodes allowed '+' character into percent, so that URLDecoder won't treat it as a space
+   * character.
+   */
+  private static String encodeAllowedCharacters(String value) {
+    value = value.replace("+", "%2B");
+    return value;
+  }
+
   /**
    * Resets parsing state, preparing to start a new list element (see spec).
    *

api/all/src/test/java/io/opentelemetry/api/baggage/propagation/W3CBaggagePropagatorTest.java

@@ -473,4 +473,34 @@ void inject_nullSetter() {
     W3CBaggagePropagator.getInstance().inject(context, carrier, null);
     assertThat(carrier).isEmpty();
   }
+
+  @Test
+  void shouldAllowBase64SpecialCharacters() {
+    String encodedInBase64 =
+        "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";
+
+    W3CBaggagePropagator propagator = W3CBaggagePropagator.getInstance();
+
+    Context result =
+        propagator.extract(
+            Context.root(),
+            ImmutableMap.of(
+                "baggage",
+                "key1= value1; metadata-key = value; othermetadata, "
+                    + "key2 =value2 , key3 =\tvalue3 , foo="
+                    + encodedInBase64),
+            getter);
+
+    Baggage expectedBaggage =
+        Baggage.builder()
+            .put(
+                "key1",
+                "value1",
+                BaggageEntryMetadata.create("metadata-key = value; othermetadata"))
+            .put("key2", "value2", BaggageEntryMetadata.empty())
+            .put("key3", "value3")
+            .put("foo", encodedInBase64)
+            .build();
+    assertThat(Baggage.fromContext(result)).isEqualTo(expectedBaggage);
+  }
 }