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Areas where Jackson is Used:

    1.   Direct usage of Jackson by Portal code

    2.   Indirect dependency through other packages

Modules with direct dependency on Jackson package:


Portal-SDK:


  1. epsdk-fw
  2. epsdk-analytics
  3. epsdk-app-common
  4. epsdk-app-os
  5. epsdk-core
  6. epsdk-domain
  7. epsdk-music
  8. epsdk-workflow
  9. epsdk-aaf

Portal:

  1. Portal-BE-Common:
  2. Portal-BE-OS:
  3. Portal-widget-ms:

Packages used that have dependency on Jackson:

Portal-SDK:

  1. org.elasticsearch:elasticsearch:jar – Not using this package anywhere in the code and can be removed, as confirmed by Sunder.
  2. org.onap.portal.sdk:epsdk-music:jar


Portal:


  1. com.orbitz.consul:consul-client:jar
  2. org.elasticsearch:elasticsearch:jar - Not using this package anywhere in the code and can be removed, as confirmed by Sunder

Code Analysis:

  1. Portal-SDK:   Approximately 60+ files that inculde fatserxml jackson excluding test files.
  2. Portal: Approximately 60+ files that inculde fatserxml jackson excluding test files


Using Gson In our Code:

Gson Maven Dependency:


            <dependency>

                        <groupId>com.google.code.gson</groupId>

                        <artifactId>gson</artifactId>

                        <version>${gson.version}</version>

            </dependency>


POC- Replacing Jackson with Gson in our code:

  • Gson FromJson method as replacement for Jackson readValue method-Replaced Jackson methods with Gson methods in saveRoleFunction() method of RoleFunctionListController class as below,


                  Replaced this,

                                  public void saveRoleFunction() {

                                              String data = roleFunc;

                                              RoleFunction availableRoleFunction = mapper.readValue(data, RoleFunction.class);

                                              System.out.println("mapper.readVlaue:"+availableRoleFunction);   

                                   }

              With this,

                                  public void saveRoleFunction() {

                                              String data = roleFunc;

                                              RoleFunction roleFunctonAvailable = gson.fromJson(data, RoleFunction.class);

                                              System.out.println("gson:fromJson:"+roleFunctonAvailable);    

                                  }


               Output for both methods, gson.fromJson() and mapper.readValue, is same.


  • Gson toJson method as replacement for Jackson writeValueAsString method-Replaced Jackson methods with Gson methods in buildJsonResponse() method of JsonMessage class as below,


              Replaced this,

                              public static String buildJsonResponse(boolean success, String msg) {

                                           String json = null;

                                           json = new ObjectMapper().writeValueAsString(response);

                                          System.out.println("mapper.WriteValueAsString:"+json);

                                           return json;

                            }


             With this,

                           public static String buildJsonResponse(boolean success, String msg) {

                                        String jsonFromGson = null;

                                         jsonFromGson = new Gson().toJson(response);

                                         System.out.println("Gson().toJson:"+jsonFromGson);

                                         return jsonFromGson;

                          }


            Output for both methods, gson.fromJson() and mapper.readValue, is same



Jackson Methods used in our code and their equivalents in Gson:

            Below are few of the methods and their usages in Gson that can be used as replacements for Jackson,

Jackson MethodJackson ClassUsageGSON Equivalent MethodGSON Equivalent ClassUsage
readValuejackson.databind.ObjectMapper<ObjectType> obj = mapper.readValue(JsonString, ClassType);fromJsoncom.google.gson.Gson;<ObjectType> obj = gson.fromJson(data, RoleFunction.class);
writeValueAsStringjackson.databind.ObjectMapperString json = new ObjectMapper().writeValueAsString(Object);toJsoncom.google.gson.Gson;String resultJson = new Gson().toJson(Object);
configurejackson.databind.ObjectMapperobjectMapper.configure(com.fasterxml.jackson.databind.SerializationFeature.WRITE_DATES_AS_TIMESTAMPS)
objectMapper.disable(DeserializationFeature.FAIL_ON_NULL_FOR_PRIMITIVES)		Use GsonBuilder to construct a Gson instance when you need to set configuration options other than the defaultcom.google.gson.GsonBuilderGson gson = new GsonBuilder()
     .serializeNulls()
     .setDateFormat(DateFormat.LONG)
     .create();
readTreejackson.databind.ObjectMapperJsonNode root = mapper.readTree(request.getReader());parsecom.google.gson.JsonParserJsonElement rootNode = parser.parse(jsonString);
NAjackson.databind.JsonNode;Base class for all JSON nodes, which form the basis of JSONNAimport com.google.gson.JsonElement;class representing an element of Json. It could either be a JsonObject, a JsonArray, a JsonPrimitive or a JsonNull
NAjackson.core.type.TypeReferenceTypeReference<List<Type>> typeRef = new TypeReference<List<Type>>() {};
      List<Type> listObj = mapper.readValue(requestBody, typeRef);		NAimport com.google.gson.reflect.TypeToken;listObj = gson.fromJson(jsonString, new TypeToken<Hashtable<String, Type>>() {}.getType());
NAimport com.fasterxml.jackson.databind.type.TypeFactory;
NA

NAjackson.annotation.JsonIgnoreProperties;JsonIgnoreProperties(ignoreUnknown = true)NAcom.google.gson.annotations.ExposeGSON @Expose annotation using GsonBuilder.excludeFieldsWithoutExposeAnnotation().
NAjackson.annotation.JsonRootName;JsonRootName(value="abc")
public class ClassName {}		NAjavax.xml.bind.annotation.XmlElementXmlRootElement
public class ClassName {}


References:
https://www.baeldung.com/jackson-vs-gson
http://websystique.com/java/json/gson-json-annotations-example/
https://www.tutorialspoint.com/gson/gson_tree_model.htm
https://google.github.io/gson/apidocs/index.html?com/google/gson/class-use/JsonElement.html
https://www.baeldung.com/gson-deserialization-guide
http://websystique.com/java/json/gson-tree-model-example/

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