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By default, the Gson object does not serialize the fields with null values to JSON. If a field in a Java object is null, Gson excludes it. We can force Gson to serialize null values via the GsonBuilder class.
You can ignore null fields at the class level by using @JsonInclude(Include. NON_NULL) to only include non-null fields, thus excluding any attribute whose value is null. You can also use the same annotation at the field level to instruct Jackson to ignore that field while converting Java object to json if it's null.
The GSON JsonParser class can parse a JSON string or stream into a tree structure of Java objects. GSON also has two other parsers. The Gson JSON parser which can parse JSON into Java objects, and the JsonReader which can parse a JSON string or stream into tokens (a pull parser).
ConclusionBoth Gson and Jackson are good options for serializing/deserializing JSON data, simple to use and well documented. Advantages of Gson: Simplicity of toJson/fromJson in the simple cases. For deserialization, do not need access to the Java entities.
See Gson User Guide - Null Object Support:
The default behaviour that is implemented in Gson is that null object fields are ignored. This allows for a more compact output format; however, the client must define a default value for these fields as the JSON format is converted back into its Java form.
Here's how you would configure a Gson instance to output null:
Gson gson = new GsonBuilder().serializeNulls().create();
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