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How to convert Java object to JSON using GSON library?
JSON or JavaScript Object Notation is a lightweight text-based open standard designed for human-readable data interchange. Conventions used by JSON are known to programmers, which include C, C++, Java, Python, Perl, etc.
There are several Java libraries available to handle JSON objects. Google Gson is a simple Java-based library to serialize Java objects to JSON and vice versa. It is an open-source library developed by Google.
Converting Java object to JSON
The Google's Gson library provides a class with the same name (Gson) which is the main class of the library.
This class provides a method named toJson() there are several variants of this method where one among them accepts a Java object and converts it into a JSON object and returns it.
Therefore, to convert a Java object to a JSON String using GSON library −
Add the following maven dependency to your pom.xml
<dependency> <groupId>com.google.code.gson</groupId> <artifactId>gson</artifactId> <version>2.8.5</version> </dependency>
Create a javabean/POJO object with private variables and setter/getter methods.
Create another class (make sure that the POJO class is available to this).
In it, create an object of the POJO class, set required values to it using the setter methods.
Instantiate the Gson class.
Invoke the toJson() method by passing the above created POJO object.
Retrieve and print the obtained JSON.
Example
import com.google.gson.Gson;
class Student {
private int id;
private String name;
private int age;
private long phone;
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public int getAge() {
return age;
}
public void setAge(int age) {
this.age = age;
}
public long getPhone() {
return phone;
}
public void setPhone(long phone) {
this.phone = phone;
}
}
public class ObjectTOString {
public static void main(String args[]) {
Student std = new Student();
std.setId(001);
std.setName("Krishna");
std.setAge(30);
std.setPhone(9848022338L);
//Creating the Gson object
Gson gSon = new Gson();
String jsonString = gSon.toJson(std);
System.out.println(jsonString);
}
}Output
{"id":1,"name":"Krishna","age":30,"phone":9848022338}
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