I am trying to think of scenario to use Jackson TreeModel and Databinding API (Object mapper). When you would chose one again the another ?
URL-es you added to a question contain the answer in the overview.
Working with Tree Model
We’ll use JsonNode for various conversions as well as adding,
modifying and removing nodes.
and
Intro to the Jackson ObjectMapper
This write-up is focused on understanding the Jackson ObjectMapper
class – and how to serialize Java objects into JSON and deserialize
JSON string into Java objects.
I can only confirm that. 99% of examples I had to serialize Java POJO classes to JSON and vice versa. When I need to change a little JSON I use Tree Model to avoid whole serializing and deserializing process.
Related
I can't find any explanation about difference between jackson's ObjectMapper to other mappers like dozer/mapStruct/modelMapping/etc. All the articles compare dozer/mapStruct/modelMapping but they ignore ObjectMapper. I can't understand what is wrong? Is the same mapper?
Dozer, MapStruct and ModelMapping are Java Bean to Java Bean mappers frameworks that recursively copies data from one object to another, property by property, field by field.
From other side, ObjectMapper provides functionality for reading and writing JSON, either to and from basic POJOs, or to and from a general-purpose JSON Tree Model. ObjectMapper has some additional features like converting objects (see convertValue method) but it is not a main reason why this class was created.
So, if you want to implement sophisticated mapping between two different models you should use mappers; if you want to serialise model to JSON or deserialise model from JSON payload you have to use ObjectMapper from Jackson.
Jackson library- Mainly concerned with converting Objects/ Entities to JSON and back.
ModelMapper/ MapStruct - Concerned with mapping One entity to another like, mapping an Entity to its DTO. This operation can get pretty gnarly owing to the size and complexity of different entities, so we need these libraries to make work easier.
I need to provide a different version of response object for the same existing URI. I am going with Accept/Content-type conneg methodologies. I am using Jackson to covert my POJO into json. please help me how should i do it with jackson.
for the object model, must i have a base class and object versions are extended class?
Instead of having one object that would be serialized in two different ways, I'd recommend using two separate DTOs. One for each version.
The content negotiation will happen not on Jackson's side, but on the JAX-RS side with the #Produces annotation.
One method returning DTOv1 will produce application/vnd.v1+json while the other will return DTOv2 with application/vnd.v2+json.
How can one obtain a default deserialized object in a custom Jackson deserializer?
I have an object which contains some fields which are not to be serialized, but which I wish to always be populated upon deserialization. In other words, a post-deserialize step.
I have created my own deserializer and annotated the class with a corresponding #JsonDeserialize, but I don't want to deserialize each field in the domain object by hand. Is there a way to get the regular deserialized object so I can just populate my custom fields? (Or else, just register a post-deserialization processor on a bean)
I have seen the answer to this question which hints at an answer, but I'm sufficiently unaware of the Jackson API to determine how best to actually effect this.
This can be achieved by using a BeanSerializerModifier and extending BeanSerializerBase, as per #ryanp's answer to this question.
I can easily find tools that:
transform JSON to csharp model classes
transform JSON to objc model classes
transform JSON to POJOs for java
etc.
But what happens if I'm looking to step in the middle of this process and roll my own transformer from JSON to blah model classes?
Is there a programming framework or tool that understands JSON very well and simply provides hooks or callbacks that I can programmatically implement, in order to do the second half of the job, which is to spit out my own style of model classes?
My motivation behind this question is the fact that I found: http://jsonpack.com/ModelGenerators/ObjectiveC which helps generate ObjC model classes which are dependent on the JSONKit framework but I would like to generate ObjC model classes that are dependent on the RestKit framework instead.
If I understand you correctly, you are probably looking for a "SAX style" parser. That is, you implement some sort of a delegate for a parser which receives parse events from the parser and which handles these events appropriately.
So, instead of creating a JSON representation which is a hierarchy of Foundation objects consisting of NSArray, NSDictionary, and NSString etc., your delegate instead creates one or more instances of certain custom classes.
While this is feasible, if you have such a "SAX style" parser (which NSJSONSerialization is not), it certainly requires some amount of effort. Note, that you can always "convert" a Foundation hierarchy to any other object - say a Core Data model object. (Means, initialize an object from a NSDictionary). But, the more elaborate approach is certainly faster.
The two Objective-C JSON parser frameworks that I know of which have a SAX style API are SBJson https://github.com/stig/json-framework/ and JPJson https://github.com/couchdeveloper/JPJson.
The latter parser library (JPJson) is in fact quite obviously designed by separating these two tasks: a) parsing and b) performing semantic actions. You can subclass from an existing base class "semantic actions" "and create your own and override "handler methods" which correspond to handle the parse events.
I'm the author of JPJson and currently updating it to accommodate for new clang compiler (C++11) and Xcode.
Can anyone please elabortae me the reasons why should I use Data Contract Serializer
while we have XML/Binary serializer already there in .Net ?
This is a site i found when i was looking into the same issue.
You should check this out
Quoting from the same link mentioned above:
Advantages of DataContractSerializer over XMLSerializer
Opt-in rather than opt-out properties to serialize.
Because it is opt in you can serialize not only properties, but also fields. You can even serialize non-public members such as private or protected members. And you dont need a set on a property either (however without a setter you can serialize, but not deserialize)
Is about 10% faster than XmlSerializer to serialize the data because since you don’t have full control over how it is serialize, there is a lot that can be done to optimize the serialization/deserialization process.
Can understand the SerializableAttribute and know that it needs to be serialized
More options and control over KnownTypes
Hope it helps!
One more HUGE advantage; DataContract serialization allows for interop between any two classes that implement the same DataContract. This is what allows WCF to generate the data classes for you automatically when you reference a WCF service. You can also "hack" this process by referencing a published DataContract in a new user-developed class (or two or three); You can then transfer data between instances of these classes, and any other new ones you create, via serialization. This is also possible but much more difficult with XML serialization, and impossible with binary serialization.