feat: minor fix

Author: opensourcevk

library/src/main/java/com/mastercard/developer/oauth2/http/UserAgent.java

@@ -12,22 +12,28 @@ public final class UserAgent {
     private static final String PRODUCT = "Mastercard-OAuth2-Client";
     private static final String UNKNOWN_VERSION = "0.0.0-unknown";
     private static final String VERSION = readVersionFile();
+    // Cache the user-agent string to avoid rebuilding it on every call
+    private static final String CACHED_USER_AGENT = buildUserAgent();
 
     private UserAgent() {}
 
     /**
-     * Builds a stable user-agent string:
+     * Returns a stable, pre-built user-agent string:
      *   Product/Version (Runtime; OS [OS Version])
      * Example:
      *   Mastercard-OAuth2-Client/1.0.0 (Java/17.0.2; Linux 5.15)
      */
     public static String get() {
+        return CACHED_USER_AGENT;
+    }
+
+    private static String buildUserAgent() {
         String javaVer = System.getProperty("java.version", "unknown");
         String osName = System.getProperty("os.name", "unknown");
         String osVer = System.getProperty("os.version", "").trim();
-        var runtime = "Java/" + javaVer;
+        String runtime = "Java/" + javaVer;
         String osPart = osName + (osVer.isEmpty() ? "" : " " + osVer);
-        return String.format("%s/%s (%s; %s)", PRODUCT, VERSION, runtime, osPart);
+        return PRODUCT + "/" + VERSION + " (" + runtime + "; " + osPart + ")";
     }
 
     private static String readVersionFile() {

library/src/main/java/com/mastercard/developer/oauth2/internal/json/GsonJsonProvider.java

@@ -1,6 +1,7 @@
 package com.mastercard.developer.oauth2.internal.json;
 
 import com.google.gson.Gson;
+import com.google.gson.GsonBuilder;
 import com.google.gson.reflect.TypeToken;
 import com.mastercard.developer.oauth2.internal.json.exception.OAuth2ClientJsonException;
 import java.lang.reflect.Type;
@@ -9,13 +10,18 @@
 
 public class GsonJsonProvider implements JsonProvider {
 
-    private static final Gson gson = new Gson();
+    // Use a configured Gson instance and cache the Map type to avoid allocating a new TypeToken on each parse.
+    private static final Gson gson = new GsonBuilder()
+        .disableHtmlEscaping()
+        .serializeNulls()
+        .create();
+
+    private static final Type MAP_TYPE = new TypeToken<Map<String, Object>>() {}.getType();
 
     @Override
     public Map<String, Object> parse(String json) throws OAuth2ClientJsonException {
         try {
-            Type type = new TypeToken<Map<String, Object>>() {}.getType();
-            return gson.fromJson(json, type);
+            return gson.fromJson(json, MAP_TYPE);
         } catch (Exception e) {
             throw new OAuth2ClientJsonException("Failed to read JSON", e);
         }

library/src/main/java/com/mastercard/developer/oauth2/internal/json/JacksonJsonProvider.java

@@ -10,11 +10,13 @@ public class JacksonJsonProvider implements JsonProvider {
 
     private static final ObjectMapper mapper = new ObjectMapper();
 
+    // Cache the TypeReference to avoid creating a new anonymous subclass on each parse call.
+    private static final TypeReference<Map<String, Object>> MAP_TYPE_REFERENCE = new TypeReference<Map<String, Object>>() {};
+
     @Override
     public Map<String, Object> parse(String json) throws OAuth2ClientJsonException {
         try {
-            var typeReference = new TypeReference<Map<String, Object>>() {};
-            return mapper.readValue(json, typeReference);
+            return mapper.readValue(json, MAP_TYPE_REFERENCE);
         } catch (Exception e) {
             throw new OAuth2ClientJsonException("Failed to read JSON", e);
         }