Jackson – Deserialize using generic class
You need to create a TypeReference object for each generic type you use and use that for deserialization. For example – mapper.readValue(jsonString, new TypeReference<Data<String>>() {});
jackson
How to specify jackson to only use fields – preferably globally
You can configure individual ObjectMappers like this: ObjectMapper mapper = new ObjectMapper(); mapper.setVisibility(mapper.getSerializationConfig().getDefaultVisibilityChecker() .withFieldVisibility(JsonAutoDetect.Visibility.ANY) .withGetterVisibility(JsonAutoDetect.Visibility.NONE) .withSetterVisibility(JsonAutoDetect.Visibility.NONE) .withCreatorVisibility(JsonAutoDetect.Visibility.NONE)); If you want it set globally, I usually access a configured mapper through a wrapper class.
How to convert a JSON string to a Map with Jackson JSON
[Update Sept 2020] Although my original answer here, from many years ago, seems to be helpful and is still getting upvotes, I now use the GSON library from Google, which I find to be more intuitive. I’ve got the following code: public void testJackson() throws IOException { ObjectMapper mapper = new ObjectMapper(); File from = … Read more
Converting Java objects to JSON with Jackson
To convert your object in JSON with Jackson: import com.fasterxml.jackson.databind.ObjectMapper; import com.fasterxml.jackson.databind.ObjectWriter; ObjectWriter ow = new ObjectMapper().writer().withDefaultPrettyPrinter(); String json = ow.writeValueAsString(object);
No Creators, like default construct, exist): cannot deserialize from Object value (no delegate- or property-based Creator
Reason: This error occurs because jackson library doesn’t know how to create your model which doesn’t have an empty constructor and the model contains constructor with parameters which didn’t annotated its parameters with @JsonProperty(“field_name”). By default java compiler creates empty constructor if you didn’t add constructor to your class. Solution: Add an empty constructor to … Read more
When is the @JsonProperty property used and what is it used for?
Here’s a good example. I use it to rename the variable because the JSON is coming from a .Net environment where properties start with an upper-case letter. public class Parameter { @JsonProperty(“Name”) public String name; @JsonProperty(“Value”) public String value; } This correctly parses to/from the JSON: “Parameter”:{ “Name”:”Parameter-Name”, “Value”:”Parameter-Value” }
How to parse a JSON string into JsonNode in Jackson?
A slight variation on Richards answer but readTree can take a string so you can simplify it to: ObjectMapper mapper = new ObjectMapper(); JsonNode actualObj = mapper.readTree(“{\”k1\”:\”v1\”}”);
Convert a Map to a POJO
Well, you can achieve that with Jackson, too. (and it seems to be more comfortable since you were considering using jackson). Use ObjectMapper‘s convertValue method: final ObjectMapper mapper = new ObjectMapper(); // jackson’s objectmapper final MyPojo pojo = mapper.convertValue(map, MyPojo.class); No need to convert into JSON string or something else; direct conversion does much faster.
Jackson enum Serializing and DeSerializer
The serializer / deserializer solution pointed out by @xbakesx is an excellent one if you wish to completely decouple your enum class from its JSON representation. Alternatively, if you prefer a self-contained solution, an implementation based on @JsonCreator and @JsonValue annotations would be more convenient. So leveraging on the example by @Stanley the following is … Read more
Converting JSON data to Java object
I looked at Google’s Gson as a potential JSON plugin. Can anyone offer some form of guidance as to how I can generate Java from this JSON string? Google Gson supports generics and nested beans. The [] in JSON represents an array and should map to a Java collection such as List or just a … Read more