Jackson is a standard library for handling JSON-related issues in Java. In this tutorial, we will learn how to convert Java objects to JSON using the Jackson library.
First, I will illustrate with a Maven project as follows:
Jackson dependency is as follows:
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<dependency> <groupId>com.fasterxml.jackson.core</groupId> <artifactId>jackson-databind</artifactId> <version>2.18.1</version> </dependency> |
The current Application class has the following contents:
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package com.huongdanjava.jackson; public class Application { public static void main(String[] args) { } } |
Since we are converting a Java object to a JSON string, the first thing we need to do is to define a Java object. I have defined a Student class in the com.huongdanjava.jackson package as simple as:
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package com.huongdanjava.jackson; public class Student { private String name; private int age; 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; } } |
OK, let’s get started on our topic.
First, we need to initialize a Student object:
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Student student = new Student(); student.setName("Khanh"); student.setAge(30); |
To convert this Student object to a JSON string, I would use the ObjectMapper object in the Jackson library to do this.
We will initialize it first:
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ObjectMapper om = new ObjectMapper(); |
and use its writeValueAsString() method to convert a Student object to a JSON string:
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String json = om.writeValueAsString(student); System.out.println(json); |
Result:
If you want the resulting JSON string to be better formatted then you can use the ObjectMapper object and call the writerWithDefaultPrettyPrinter() method before calling the writeValueAsString() method:
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ObjectMapper om = new ObjectMapper(); String json = om.writerWithDefaultPrettyPrinter().writeValueAsString(student); System.out.println(json); |
At this point, the result will be:
