refactor: ADK's ObjectMapper shared instance is mutable (i.e., not a constant immutable object) and, therefore, its name should have the capitalization of a constant's name; this CL aligns with other code files where it is referred as "objectMapper"

a2a/src/main/java/com/google/adk/a2a/converters/PartConverter.java

@@ -33,7 +33,8 @@
  */
 public final class PartConverter {
   private static final Logger logger = LoggerFactory.getLogger(PartConverter.class);
-  private static final ObjectMapper OBJECT_MAPPER = new ObjectMapper();
+  private static final ObjectMapper objectMapper = new ObjectMapper();
+
   // Constants for metadata types. By convention metadata keys are prefixed with "adk_" to align
   // with the Python and Golang libraries.
   public static final String A2A_DATA_PART_METADATA_TYPE_KEY = "adk_type";
@@ -172,7 +173,7 @@ private static Optional<com.google.genai.types.Part> convertDataPartToGenAiPart(
     }
 
     try {
-      String json = OBJECT_MAPPER.writeValueAsString(data);
+      String json = objectMapper.writeValueAsString(data);
       return Optional.of(com.google.genai.types.Part.builder().text(json).build());
     } catch (JsonProcessingException e) {
       logger.warn("Failed to serialize DataPart payload", e);
@@ -254,7 +255,7 @@ public static Optional<io.a2a.spec.Part<?>> fromGenaiPart(Part part) {
     return Optional.empty();
   }
 
-  @SuppressWarnings("unchecked") // safe conversion from OBJECT_MAPPER.readValue
+  @SuppressWarnings("unchecked") // safe conversion from objectMapper.readValue
   private static Map<String, Object> coerceToMap(Object value) {
     if (value == null) {
       return new HashMap<>();
@@ -272,7 +273,7 @@ private static Map<String, Object> coerceToMap(Object value) {
         return new HashMap<>();
       }
       try {
-        return OBJECT_MAPPER.readValue(str, Map.class);
+        return objectMapper.readValue(str, Map.class);
       } catch (JsonProcessingException e) {
         logger.warn("Failed to parse map from string payload", e);
         Map<String, Object> fallback = new HashMap<>();

core/src/main/java/com/google/adk/examples/ExampleUtils.java

@@ -50,7 +50,7 @@ public final class ExampleUtils {
   private static final String FUNCTION_RESPONSE_PREFIX = "```tool_outputs\n";
   private static final String FUNCTION_RESPONSE_SUFFIX = "\n```\n";
 
-  private static final ObjectMapper OBJECT_MAPPER = new ObjectMapper();
+  private static final ObjectMapper objectMapper = new ObjectMapper();
 
   /**
    * Converts a list of examples into a formatted few-shot prompt string.
@@ -140,7 +140,7 @@ private static void appendFunctionResponse(FunctionResponse response, StringBuil
       Object responseMap = response.response().orElse(ImmutableMap.of());
       builder
           .append(FUNCTION_RESPONSE_PREFIX)
-          .append(OBJECT_MAPPER.writeValueAsString(responseMap))
+          .append(objectMapper.writeValueAsString(responseMap))
           .append(FUNCTION_RESPONSE_SUFFIX);
     } catch (JsonProcessingException e) {
       builder.append(FUNCTION_RESPONSE_PREFIX).append(FUNCTION_RESPONSE_SUFFIX);

core/src/main/java/com/google/adk/flows/llmflows/RequestConfirmationLlmRequestProcessor.java

@@ -51,7 +51,7 @@
 public class RequestConfirmationLlmRequestProcessor implements RequestProcessor {
   private static final Logger logger =
       LoggerFactory.getLogger(RequestConfirmationLlmRequestProcessor.class);
-  private static final ObjectMapper OBJECT_MAPPER = JsonBaseModel.getMapper();
+  private static final ObjectMapper objectMapper = JsonBaseModel.getMapper();
   private static final String ORIGINAL_FUNCTION_CALL = "originalFunctionCall";
 
   @Override
@@ -177,7 +177,7 @@ private Optional<FunctionCall> getOriginalFunctionCall(FunctionCall functionCall
     }
     try {
       FunctionCall originalFunctionCall =
-          OBJECT_MAPPER.convertValue(
+          objectMapper.convertValue(
               functionCall.args().get().get(ORIGINAL_FUNCTION_CALL), FunctionCall.class);
       if (originalFunctionCall.id().isEmpty()) {
         return Optional.empty();
@@ -229,14 +229,14 @@ private static Optional<Map.Entry<String, ToolConfirmation>> maybeCreateToolConf
       return Optional.of(
           Map.entry(
               functionResponse.id().get(),
-              OBJECT_MAPPER.convertValue(responseMap, ToolConfirmation.class)));
+              objectMapper.convertValue(responseMap, ToolConfirmation.class)));
     }
 
     try {
       return Optional.of(
           Map.entry(
               functionResponse.id().get(),
-              OBJECT_MAPPER.readValue(
+              objectMapper.readValue(
                   (String) responseMap.get("response"), ToolConfirmation.class)));
     } catch (JsonProcessingException e) {
       logger.error("Failed to parse tool confirmation response", e);

core/src/main/java/com/google/adk/tools/FunctionCallingUtils.java

@@ -45,7 +45,7 @@
 public final class FunctionCallingUtils {
 
   private static final Logger logger = LoggerFactory.getLogger(FunctionCallingUtils.class);
-  private static final ObjectMapper OBJECT_MAPPER = JsonBaseModel.getMapper();
+  private static final ObjectMapper objectMapper = JsonBaseModel.getMapper();
 
   /** Holds the state during a single schema generation process to handle caching and recursion. */
   private static class SchemaGenerationContext {
@@ -162,7 +162,7 @@ private static Schema buildSchemaFromParameter(Parameter param) {
    * @throws IllegalArgumentException if a type is encountered that cannot be serialized by Jackson.
    */
   public static Schema buildSchemaFromType(Type type) {
-    return buildSchemaRecursive(OBJECT_MAPPER.constructType(type), new SchemaGenerationContext());
+    return buildSchemaRecursive(objectMapper.constructType(type), new SchemaGenerationContext());
   }
 
   /**
@@ -217,7 +217,7 @@ private static Schema buildSchemaRecursive(JavaType javaType, SchemaGenerationCo
         }
         builder.enum_(enumValues).type("STRING").format("enum");
       } else { // POJO
-        if (!OBJECT_MAPPER.canSerialize(rawClass)) {
+        if (!objectMapper.canSerialize(rawClass)) {
           throw new IllegalArgumentException(
               "Unsupported type: "
                   + rawClass.getName()
@@ -226,7 +226,7 @@ private static Schema buildSchemaRecursive(JavaType javaType, SchemaGenerationCo
                   + " directly.");
         }
         BeanDescription beanDescription =
-            OBJECT_MAPPER.getSerializationConfig().introspect(javaType);
+            objectMapper.getSerializationConfig().introspect(javaType);
         Map<String, Schema> properties = new LinkedHashMap<>();
         List<String> required = new ArrayList<>();
         for (BeanPropertyDefinition property : beanDescription.findProperties()) {

core/src/main/java/com/google/adk/tools/FunctionTool.java

@@ -44,7 +44,7 @@
 public class FunctionTool extends BaseTool {
 
   private static final Logger logger = LoggerFactory.getLogger(FunctionTool.class);
-  private static final ObjectMapper OBJECT_MAPPER = JsonBaseModel.getMapper();
+  private static final ObjectMapper objectMapper = JsonBaseModel.getMapper();
 
   private final @Nullable Object instance;
   private final Method func;
@@ -241,17 +241,15 @@ private Maybe<Map<String, Object>> call(Map<String, Object> args, ToolContext to
     } else if (result instanceof Maybe) {
       return ((Maybe<?>) result)
           .map(
-              data ->
-                  OBJECT_MAPPER.convertValue(data, new TypeReference<Map<String, Object>>() {}));
+              data -> objectMapper.convertValue(data, new TypeReference<Map<String, Object>>() {}));
     } else if (result instanceof Single) {
       return ((Single<?>) result)
-          .map(
-              data -> OBJECT_MAPPER.convertValue(data, new TypeReference<Map<String, Object>>() {}))
+          .map(data -> objectMapper.convertValue(data, new TypeReference<Map<String, Object>>() {}))
           .toMaybe();
     } else {
       try {
         return Maybe.just(
-            OBJECT_MAPPER.convertValue(result, new TypeReference<Map<String, Object>>() {}));
+            objectMapper.convertValue(result, new TypeReference<Map<String, Object>>() {}));
       } catch (IllegalArgumentException e) {
         // Conversion to map failed, in this case we follow
         // https://google.github.io/adk-docs/tools-custom/function-tools/#return-type and return
@@ -326,7 +324,7 @@ private Object[] buildArguments(
           continue;
         }
       } else if (argValue instanceof Map) {
-        arguments[i] = OBJECT_MAPPER.convertValue(argValue, paramType);
+        arguments[i] = objectMapper.convertValue(argValue, paramType);
         continue;
       }
       arguments[i] = castValue(argValue, paramType);
@@ -363,7 +361,7 @@ private static List<Object> createList(List<Object> values, Class<?> type) {
           || cls == String.class) {
         list.add(castValue(value, cls));
       } else {
-        list.add(OBJECT_MAPPER.convertValue(value, type));
+        list.add(objectMapper.convertValue(value, type));
       }
     }
     return list;
@@ -414,6 +412,6 @@ private static Object castValue(Object value, Class<?> type) {
         return value;
       }
     }
-    return OBJECT_MAPPER.convertValue(value, type);
+    return objectMapper.convertValue(value, type);
   }
 }

core/src/main/java/com/google/adk/tools/applicationintegrationtoolset/ApplicationIntegrationToolset.java

@@ -28,7 +28,7 @@ public class ApplicationIntegrationToolset implements BaseToolset {
   String serviceAccountJson;
   @Nullable String toolNamePrefix;
   @Nullable String toolInstructions;
-  public static final ObjectMapper OBJECT_MAPPER = new ObjectMapper();
+  public static final ObjectMapper objectMapper = new ObjectMapper();
   private final HttpClient httpClient;
   private final CredentialsHelper credentialsHelper;
 
@@ -118,13 +118,13 @@ public ApplicationIntegrationToolset(
 
   List<String> getPathUrl(String openApiSchemaString) throws Exception {
     List<String> pathUrls = new ArrayList<>();
-    JsonNode topLevelNode = OBJECT_MAPPER.readTree(openApiSchemaString);
+    JsonNode topLevelNode = objectMapper.readTree(openApiSchemaString);
     JsonNode specNode = topLevelNode.path("openApiSpec");
     if (specNode.isMissingNode() || !specNode.isTextual()) {
       throw new IllegalArgumentException(
           "Failed to get OpenApiSpec, please check the project and region for the integration.");
     }
-    JsonNode rootNode = OBJECT_MAPPER.readTree(specNode.asText());
+    JsonNode rootNode = objectMapper.readTree(specNode.asText());
     JsonNode pathsNode = rootNode.path("paths");
     Iterator<Map.Entry<String, JsonNode>> paths = pathsNode.fields();
     while (paths.hasNext()) {
@@ -184,12 +184,12 @@ private List<BaseTool> getAllTools() throws Exception {
               this.serviceAccountJson,
               this.httpClient,
               this.credentialsHelper);
-      ObjectNode parentOpenApiSpec = OBJECT_MAPPER.createObjectNode();
+      ObjectNode parentOpenApiSpec = objectMapper.createObjectNode();
       ObjectNode openApiSpec =
           integrationClient.getOpenApiSpecForConnection(toolNamePrefix, toolInstructions);
-      String openApiSpecString = OBJECT_MAPPER.writeValueAsString(openApiSpec);
+      String openApiSpecString = objectMapper.writeValueAsString(openApiSpec);
       parentOpenApiSpec.put("openApiSpec", openApiSpecString);
-      openApiSchemaString = OBJECT_MAPPER.writeValueAsString(parentOpenApiSpec);
+      openApiSchemaString = objectMapper.writeValueAsString(parentOpenApiSpec);
       List<String> pathUrls = getPathUrl(openApiSchemaString);
       for (String pathUrl : pathUrls) {
         String toolName = integrationClient.getOperationIdFromPathUrl(openApiSchemaString, pathUrl);
@@ -202,7 +202,7 @@ private List<BaseTool> getAllTools() throws Exception {
                   this.serviceAccountJson,
                   this.httpClient,
                   this.credentialsHelper,
-                  OBJECT_MAPPER);
+                  objectMapper);
 
           ConnectionsClient.ConnectionDetails connectionDetails =
               connectionsClient.getConnectionDetails();