feat: Eliminate one deserialization step in the majority of scenarios when parsing Model response

Signed-off-by: bourne7 <[email protected]>

Author: bourne7

spring-ai-model/src/main/java/org/springframework/ai/util/json/JsonParser.java

@@ -168,8 +168,21 @@ else if (javaType.isEnum()) {
 			return Enum.valueOf((Class<Enum>) javaType, value.toString());
 		}
 
-		String json = JsonParser.toJson(value);
-		return JsonParser.fromJson(json, javaType);
+		Object result = null;
+		if (value instanceof String jsonString) {
+			try {
+				result = JsonParser.fromJson(jsonString, javaType);
+			} catch (Exception e) {
+				//  ignore
+			}
+		}
+
+		if (result == null) {
+			String json = JsonParser.toJson(value);
+			result = JsonParser.fromJson(json, javaType);
+		}
+
+		return result;
 	}
 
 }