I am trying to to convert JSON to POJO class. This JSON I am getting from third party REST API call and I want to convert it into POJO class. For this I am using jackson-databind jar and below is part of my code.
ObjectMapper mapper = new ObjectMapper();
Object modelObject; // object in which I want to convert my JSON object
mapper.writeValue(request.getShipmentDataJson(), modelObject);
Here for now instead of POJO class I declared modelObjcet variable of Object type and my question is do we need to create POJO class with required fields and getter setter methods before converting JSON to POJO?
If yes, then how should we create this POJO class from JSONSchema and when it get created?
Please explain me this concept. My understanding is we POJO should get create directly from JSONSchema but when and how that I don't know. And I think once POJO get created then I can use my above code to store JSON object to POJO.
You need an object with fields corresponding to incoming JSON (names and datatypes) - so jackson can populate and instantiate it. There are tools like this:
http://www.jsonschema2pojo.org/
to generate java code from JSON
Related
I am trying to deserialize an object of a class that I do not own. The class has attribute names such as id_, address_, name_, but its getters are getId() getAddress() getName() etc.
When I try to deserialize the JSON using Jackson, I get
com.fasterxml.jackson.databind.exc.UnrecognizedPropertyException: Unrecognized field "id_", not marked as ignorable
It looks like this happens because Jackson's looking for getId_() instead of getId(). Since I do not own the underlying class, I cannot use Jackson's annotations to map attributes to custom json fields.
How can I deserialize with a custom mapping of object attributes to its getter methods?
You can try a custom deserializer.
check out: https://www.baeldung.com/jackson-deserialization
This way you can register a deserializer for the class.
However, you still have to edit it when the class changes.
One other thing you can try:
mapper.setVisibility(PropertyAccessor.FIELD, Visibility.ANY);
This will give the mapper full access to private members.
You can apply a MixIn for Jackson - that's how I solved my issue trying to serialize and deserialize JSON for an auto-generated AVRO class (Avro generated class issue with json conversion [kotlin])
Here is an example:
https://medium.com/#shankar.ganesh.1234/jackson-mixin-a-simple-guide-to-a-powerful-feature-d984341dc9e2
I have bean object say Documents having properties. And I have an arraylist as List<Documents>. I have a json string as follows:
[{"language"="English","Type"="fiction"},{}]
Language and type are properties of Documents class. I want to deserialize it into a List<Documents> using JSONDeserializer in Liferay.
Used Serialization implements and #JSON annotation on getters of documents class
I am using GSON to parse a JSON file and i want to map this JSON object to a POJO class. The problem is the property name in JSON doesn't have camel-case but my java POJO object having camel-case property name.
Is there any idea without having any performance hit?
Eg: attribute name in JSON file is 'OrderNumber', But in my POJO class , Instead ordernumber, i have 'salesNumber' as attribute name. Now how can we map that OrderNumber from JSON to salesNumber of POJO class?
Thanks in advance!
You can use #SerializedName annotation in this case.
private class SomeObject {
#SerializedName("OrderNumber")
private String salesNumber;
}
Is there away to parse json with java keywords like class, case, default etc. to java object using Gson library?
The lines
Gson gson = new Gson();
MyObject myObject = gson.fromJson(json, MyObject.class);
simply parse json to my pojo, but I have key "class" in my json and I can't use the field "class" in java classes.
Yes, annotate your fields with #SerializedName, specifying the name of the field.
#SerializedName("class")
private String classField;
Or use a custom TypeAdapter.
You have to use annotations. These annotations tell Gson which JSON field maps to which Java property:
http://www.javacreed.com/gson-annotations-example/
I am developing a web application. I have database used by the web service. I want to send the same data to the web pages which are calling web service.
I get the data i.e. single row from the database by using hibernate and POJO classes(getColumn). Now I have object(POJO class) of the Table which represent single row of the database. For sending it back to the web pages (html, jsp), I need to convert it to the json object as my web service returns the json object.
How can I make Json object from POJO classes. There are many other ways to generate Json String but i want json object.
How can do this?
Thank you
You can use GSon to convert json object to java object
Link
to refer example.
Gson gson = new Gson();
//to get json object use toJson
String json = gson.toJson(obj);
//to get java object use fromJson
MyClass obj = gson.fromJson(jsonObj, MyClass.class);
or
jackson is also pretty fast and easy to use
private ObjectMapper mapper = new ObjectMapper();
JsonNode node = mapper.convertValue(YOUR POJO CLASS, JsonNode.class);
You can use Jackson and achieve this as above. GSON also does the job.
The way I use is with Google's Gson library. Very simple and powerful
Spring and Jackson as it is so simple. You can find a very basic example below Jackson/spring JSON example