Java Articles - Page 172 of 540

A JSONObject is an unordered collection of name/value pairs whereas Map is an object that maps keys to values. A Map cannot contain duplicate keys and each key can map to at most one value. We need to use the JSON-lib library for serializing and de-serializing a Map in JSON format. Initially, we can create a POJO class and pass this instance as an argument to the put() method of Map class and finally add this map instance to the accumulateAll() method of JSONObject.Syntaxpublic void accumulateAll(Map map)In the below example, we can convert Map to a JSON object.Exampleimport java.util.*; import net.sf.json.JSONObject; public class ConvertMapToJSONObjectTest { ... Read More

The net.sf.json.JSONArray is an ordered sequence of values. Its external text form is a string wrapped in square brackets with commas separating the values and an internal form is an object having get() and opt() methods for accessing the values by index, and element() method for adding or replacing values. The values can be any of these types like Boolean, JSONArray, JSONObject, Number, String and JSONNull object.We can convert a collection(List) to JSON array in the below exampleExampleimport java.util.*; import net.sf.json.JSONArray; import net.sf.json.JSONSerializer; public class ConvertCollectionToJsonArrayTest {    public static void main(String[] args) {       List strList = Arrays.asList("India", "Australia", "England", ... Read More

The JSON-lib is a Java library for serializing and de-serializing java beans, maps, arrays, and collections in JSON format. We can add elements to the JSON object using the element() method of JSONObject class. We need to download all the dependent jars like json-lib.jar, ezmorph.jar, commons-lang.jar, commons-collections.jar, commons-beanutils.jar, and commons-logging.jar and can import net.sf.json package in our java program to execute it.Syntaxpublic JSONObject element(String key, Object value) - put a key/value pair in the JSONObject Exampleimport java.util.Arrays; import net.sf.json.JSONObject; public class JsonAddElementTest {    public static void main(String[] args) {       JSONObject jsonObj = new JSONObject()          .element("name", "Raja ... Read More

The JsonBuilderFactory interface is a factory to create JsonObjectBuilder instance and JsonObjectBuilder is a builder for creating JsonObject models from scratch. This interface initializes an empty JSON object model and provides methods to add name/value pairs to the object model and to return the resulting object. We can create a JsonObjectBuilder instance that can be used to build JsonObject using the createObjectBuilder() method.SyntaxJsonObjectBuilder createObjectBuilder()In the below example, We can update an existing JSON data with newly added data.Exampleimport java.io.*; import javax.json.*; public class UpdateExistingJsonTest {    public static void main(String[] args) throws Exception {       String jsonString = "{\"id\":\"115\", \"name\":\"Raja\", \"address\":[{\"area\":\"Madhapur\", \"city\":\"Hyderabad\"}]}";       ... Read More

The ExclusionStrategy interface can be used to exclude any field during serialization and deserialization. We can provide a custom implementation of the ExclusionStrategy interface and need to register it with GsonBuilder using the setExclusionStrategies() method. It configures Gson to apply a set of exclusion strategies during serialization and deserialization.Syntaxpublic GsonBuilder setExclusionStrategies(ExclusionStrategy... strategies)Exampleimport com.google.gson.*; import com.google.gson.ExclusionStrategy; import com.google.gson.FieldAttributes; public class ExclusionStrategyTest {    public static void main(String args[]) throws Exception {       Gson gson = new GsonBuilder().setExclusionStrategies(new CustomExclusionStrategy()).create();          Person person = new Person();          person.setFirstName("Adithya");          person.setLastName("Sai");          person.setAddress("Hyderabad");     ... Read More

JSON Schema is a specification for JSON based format for defining the structure of JSON data. The JsonSchema class can provide a contract for what JSON data is required for a given application and how to interact with it. The JsonSchema can define validation, documentation, hyperlink navigation, and interaction control of JSON data. We can generate the JSON schema using the generateSchema() method of JsonSchemaGenerator, this class wraps the JSON schema generation functionality.Syntaxpublic JsonSchema generateSchema(Class type) throws com.fasterxml.jackson.databind.JsonMappingExceptionExampleimport com.fasterxml.jackson.core.JsonProcessingException; import com.fasterxml.jackson.databind.ObjectMapper; import com.fasterxml.jackson.module.jsonSchema.JsonSchema; import com.fasterxml.jackson.module.jsonSchema.JsonSchemaGenerator; import java.util.List; public class JSONSchemaTest {    public static void main(String[] args) throws JsonProcessingException {     ... Read More

In Java, org.simple.json and org.json are two libraries that help in reading, writing, and manipulating JSON. But still, they are different. In this article, we are going to learn about these differences. Difference between JSON.simple vs JSON Let's see the below differences and they are - Features JSON.simple JSON ... Read More

The Java Arrays are objects which store multiple variables of the same type, it holds primitive types and object references and an ArrayList can represent a resizable list of objects. We can add, remove, find, sort and replace elements using the list. A JsonArray can parse text from a string to produce a vector-like object. We can convert an array or ArrayList to JsonArray using the toJsonTree().getAsJsonArray() method of Gson class.Syntaxpublic JsonElement toJsonTree(java.lang.Object src)Exampleimport com.google.gson.*; import java.util.*; public class JavaArrayToJsonArrayTest {    public static void main(String args[]) {       String[][] strArray = {{"elem1-1", "elem1-2"}, {"elem2-1", "elem2-2"}};       ArrayList arrayList = ... Read More

While deserializing, a Gson can expect a JSON object but it can find a JSON array. Since it can't convert from one to the other, it can throw an error as "JsonSyntaxException: java.lang.IllegalStateException: Expected BEGIN_OBJECT but was BEGIN_ARRAY" at the runtime.Exampleimport com.google.gson.Gson; public class GsonErrorTest {    public static void main(String args[]) throws Exception {       String json = "{\"employee\":[{\"name\":\"Raja Ramesh\", \"technology\":\"java\"}]}";       Gson gson = new Gson();       Software software = gson.fromJson(json, Software.class);       System.out.println(software);    } } class Software {    Employee employee; } class Employee {    String name; ... Read More

The javax.json.JsonWriter interface can write a JSON object or array structure to an output source. The class javax.json.JsonWriterFactory contains methods to create JsonWriter instances. A factory instance can be used to create multiple writer instances with the same configuration. We can create writers from output source using the static method createWriter() of javax.json.Json class.Syntaxpublic static JsonWriter createWriter(Writer writer)In the below example, we can serialize a JSON object using the JsonWriter interface.Exampleimport java.io.StringWriter; import javax.json.Json; import javax.json.JsonObject; import javax.json.JsonObjectBuilder; import javax.json.JsonWriter; public class JsonWriterTest {    public static void main(String[] args) {       JsonObject jsonObj = Json.createObjectBuilder()                  .add("name", ... Read More