Sometimes we need to exclude certain fields from the JSON output. For example, if we have a field that contains sensitive information, we may not want to include it in the JSON representation of the object. In such cases, we can use the Expose annotation provided by Gson. The Gson @Expose annotation The Gson @Expose annotation can be used to specify whether a field isto be exposed or not (included or not). The @Expose annotation can take two parameters, and each parameter is a boolean which can take either the value true or false. The two parameters are: ... Read More

We can read and write a file using Gson streaming API, and it is based on the sequential read and write standard. The JsonWriter and JsonReader are the core classes built for streaming write and read in Streaming API. Reading & Writing a File using Gson Streaming API The JsonWriter writes a JSON-encoded value to a stream, one token at a time. The stream includes both literal values (strings, numbers, booleans, and nulls) as well as begin and end delimiters of objects and arrays, and JsonReader reads a JSON-encoded value as a stream of tokens. The tokens are traversed in depth-first order, ... Read More

Sometimes, we may need to parse a JSON into a Gson tree model in Java. For example, we may need to parse a JSON string into a tree model when we want to manipulate the JSON data in a more easy way.The getAsJsonObject() Method The Gson library is used to parse a JSON String into a Tree Model. We will be using the JsonParser to parse the JSON string into a Tree Model of type JsonElement. We will be using the getAsJsonObject() method of JsonElement for getting the element as JsonObject, and the other is getAsJsonArray(), which is a method ... Read More

When we have a JSON object and want to change a specific field name for some reason, we can use the Jackson library in Java.The Jackson Annotation @JsonProperty The Jackson Annotation @JsonProperty is used on a property or method during the serialization or deserialization of JSON. It takes an optional 'name' parameter, which is useful in case the property name is different from the key name in JSON. By default, if the key name matches the property name, the value is mapped to the property value. If the key name is different, we can use the @JsonProperty annotation to ... Read More

The Jackson is a library for Java and it has very powerful data binding capabilities and it also provides a framework to serialize custom java objects to JSON and deserialize JSON back to Java object. Ignoring Null and Empty Fields Using Jackson The Jackson library provides @JsonInclude annotation, which controls the serialization of a class as a whole or its individual fields based on their values during serialization. The @JsonInclude annotation contains below two values: Include.NON_NULL: Indicates that only properties with not null values will be included in JSON. Include.NON_EMPTY: Indicates ... Read More

Pretty printing JSON is a process of formatting our JSON data to make it more readable and good-looking.The prettyPrint() Method of Flexjson We will be using the Flexjson library to pretty print JSON in Java. The Flexjson library is a lightweight library that is used for serializing as well as deserializing Java objects to and from JSON. A JSONSerializer is the main class for performing the serialization of Java objects to JSON and by default, performs a shallow serialization. We can pretty-print JSON using the prettyPrint(boolean prettyPrint) method of JSONSerializer class. Syntax of prettyPrint() The syntax of the prettyPrint() method ... Read More

Deserializing a JSON to a Java object means converting a JSON string into a Java object.The deserialize() Method of the Flexjson Library We will be using the Flexjson library to deserialize a JSON to a Java object in Java. The Flexjson library is a lightweight library that is used for serializing as well as deserializing Java objects to and from JSON. A JSONDeserializer is the main class for performing deserialization of JSON to Java objects. We can deserialize a JSON string to a Java object using the deserialize(String json, Class type) method of JSONDeserializer. Syntax of deserialize() Method The syntax of the ... Read More

While parsing a JSON String to or from a Java object, by default, Gson tries to create an instance of the Java class by calling the default constructor. In the case of Java, if a class doesn’t contain a default constructor or we want to do some initial configuration while creating Java objects, we need to create and register our own instance creator. Custom Instance Creator Using Gson Custom instance means creating a new instance that is not the default. In this instance, we can add whatever properties we want. There are many libraries that create custom instances. In this ... Read More

The java.util.EnumMap class is a specialized Map implementation for use with enum keys. Following are the important points about EnumMap −All of the keys in an enum map must come from a single enum type that is specified, explicitly or implicitly, when the map is created.Enum maps are maintained in the natural order of their keys.EnumMap is not synchronized. If multiple threads access an enum map concurrently, and at least one of the threads modifies the map, it should be synchronized externally.Following are the constructors of the EnumMap class −Sr.NoConstructor & Description1EnumMap(Class keyType)This constructor creates an empty enum map with the specified ... Read More

Compare two strings using compareTo() method in Java. The syntax is as follows −int compareTo(Object o)Here, o is the object to be compared.The return value is 0 if the argument is a string lexicographically equal to this string; a value less than 0 if the argument is a string lexicographically greater than this string; and a value greater than 0 if the argument is a string lexicographically less than this string.ExampleLet us now see an example − Live Demopublic class Demo {    public static void main(String args[]) {       String str1 = "Strings are immutable";       ... Read More