Of course! Working with JSON strings in Java is a fundamental task. There are several excellent libraries to handle this, but the most modern and recommended approach is using Jakarta JSON Binding (JSON-B) or Jackson.

Here's a comprehensive guide covering the most common scenarios, from simple to complex.

The Modern Standard: Using Jakarta JSON-B (Recommended)

Jakarta JSON-B is a standard API for binding JSON data to Java objects and vice-versa. It's included in Java EE (now Jakarta EE) and is the default in many modern environments like Spring Boot. The most popular implementation is Yasson.

Step 1: Add Dependencies

You need two dependencies: the API and the implementation (Yasson).

Maven (pom.xml):

<dependency>
    <groupId>jakarta.json.bind</groupId>
    <artifactId>jakarta.json-api</artifactId>
    <version>3.0.0</version>
</dependency>
<dependency>
    <groupId>org.eclipse</groupId>
    <artifactId>yasson</artifactId>
    <version>3.0.3</version>
</dependency>

Gradle (build.gradle):

implementation 'jakarta.json.bind:jakarta.json-api:3.0.0'
implementation 'org.eclipse:yasson:3.0.3'

Step 2: Create a Java Class (POJO)

Your Java class should have fields that match the keys in your JSON string. Use @JsonbProperty to customize the mapping if needed.

import jakarta.json.bind.annotation.JsonbProperty;
import jakarta.json.bind.annotation.JsonbDateFormat;
import java.time.LocalDate;
import java.util.List;
public class User {
    // This field will map to the "userName" key in the JSON
    @JsonbProperty("userName")
    private String name;
    private int age;
    private boolean isActive;
    @JsonbDateFormat("yyyy-MM-dd") // Customize date format
    private LocalDate registrationDate;
    private List<String> roles;
    // Getters and Setters (required for JSON-B)
    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 boolean isActive() { return isActive; }
    public void setActive(boolean active) { isActive = active; }
    public LocalDate getRegistrationDate() { return registrationDate; }
    public void setRegistrationDate(LocalDate registrationDate) { this.registrationDate = registrationDate; }
    public List<String> getRoles() { return roles; }
    public void setRoles(List<String> roles) { this.roles = roles; }
    @Override
    public String toString() {
        return "User{" +
                "name='" + name + '\'' +
                ", age=" + age +
                ", isActive=" + isActive +
                ", registrationDate=" + registrationDate +
                ", roles=" + roles +
                '}';
    }
}

Step 3: Perform JSON Operations

Create a Jsonb instance to handle the conversion.

import jakarta.json.bind.Jsonb;
import jakarta.json.bind.JsonbBuilder;
import java.util.Arrays;
public class Main {
    public static void main(String[] args) {
        // 1. Create a Jsonb instance
        Jsonb jsonb = JsonbBuilder.create();
        // --- JSON String to Java Object (Deserialization) ---
        String jsonString = """
                {
                  "userName": "John Doe",
                  "age": 30,
                  "isActive": true,
                  "registrationDate": "2025-10-27",
                  "roles": ["ADMIN", "USER"]
                }
                """;
        User user = jsonb.fromJson(jsonString, User.class);
        System.out.println("--- Deserialized Object ---");
        System.out.println(user);
        System.out.println("Name: " + user.getName());
        System.out.println("Role: " + user.getRoles().get(0));
        System.out.println();
        // --- Java Object to JSON String (Serialization) ---
        User newUser = new User();
        newUser.setName("Jane Smith");
        newUser.setAge(28);
        newUser.setActive(true);
        newUser.setRegistrationDate(LocalDate.now());
        newUser.setRoles(Arrays.asList("MANAGER", "USER"));
        String newJsonString = jsonb.toJson(newUser);
        System.out.println("--- Serialized JSON String ---");
        System.out.println(newJsonString);
    }
}

Output:

--- Deserialized Object ---
User{name='John Doe', age=30, isActive=true, registrationDate=2025-10-27, roles=[ADMIN, USER]}
Name: John Doe
Role: ADMIN
--- Serialized JSON String ---
{"isActive":true,"age":28,"name":"Jane Smith","registrationDate":"2025-05-21","roles":["MANAGER","USER"]}

The Most Popular Library: Jackson

Jackson is the de-facto standard in the Java world, especially in the Spring ecosystem. It's extremely powerful and flexible.

Step 1: Add Dependencies

Maven (pom.xml):

<dependency>
    <groupId>com.fasterxml.jackson.core</groupId>
    <artifactId>jackson-databind</artifactId>
    <version>2.17.0</version>
</dependency>

(This single dependency is usually enough, as it includes the core and databind modules).

Step 2: Create a Java Class (POJO)

The class structure is very similar to JSON-B.

import com.fasterxml.jackson.annotation.JsonProperty;
import com.fasterxml.jackson.annotation.JsonFormat;
import java.time.LocalDate;
import java.util.List;
public class User {
    // Maps to "userName" in JSON
    @JsonProperty("userName")
    private String name;
    private int age;
    private boolean isActive;
    // Configures date format
    @JsonFormat(shape = JsonFormat.Shape.STRING, pattern = "yyyy-MM-dd")
    private LocalDate registrationDate;
    private List<String> roles;
    // Getters and Setters
    public String getName() { return name; }
    public void setName(String name) { this.name = name; }
    // ... other getters and setters
}

Step 3: Perform JSON Operations

Jackson uses an ObjectMapper for all conversions.

import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.databind.ObjectMapper;
import java.util.Arrays;
public class Main {
    public static void main(String[] args) {
        // 1. Create an ObjectMapper instance
        ObjectMapper objectMapper = new ObjectMapper();
        // --- JSON String to Java Object (Deserialization) ---
        String jsonString = """
                {
                  "userName": "John Doe",
                  "age": 30,
                  "isActive": true,
                  "registrationDate": "2025-10-27",
                  "roles": ["ADMIN", "USER"]
                }
                """;
        try {
            User user = objectMapper.readValue(jsonString, User.class);
            System.out.println("--- Deserialized Object ---");
            System.out.println(user);
            System.out.println("Name: " + user.getName());
            System.out.println();
            // --- Java Object to JSON String (Serialization) ---
            User newUser = new User();
            newUser.setName("Jane Smith");
            newUser.setAge(28);
            newUser.setActive(true);
            newUser.setRegistrationDate(LocalDate.now());
            newUser.setRoles(Arrays.asList("MANAGER", "USER"));
            // For pretty printing
            String newJsonString = objectMapper.writerWithDefaultPrettyPrinter().writeValueAsString(newUser);
            System.out.println("--- Serialized JSON String ---");
            System.out.println(newJsonString);
        } catch (JsonProcessingException e) {
            e.printStackTrace();
        }
    }
}

Output:

--- Deserialized Object ---
User{name='John Doe', age=30, isActive=true, registrationDate=2025-10-27, roles=[ADMIN, USER]}
Name: John Doe
--- Serialized JSON String ---
{
  "name" : "Jane Smith",
  "age" : 28,
  "isActive" : true,
  "registrationDate" : "2025-05-21",
  "roles" : [ "MANAGER", "USER" ]
}

Handling JSON Without a Class (Simple Parsing)

Sometimes you don't have a predefined Java class and just need to read a value from a JSON string. For this, you can use the jakarta.json API (also known as JSON-P), which is a lower-level API for parsing, creating, and manipulating JSON.

Step 1: Add Dependency

This is usually included with JSON-B, but can be standalone.

Maven (pom.xml):

<dependency>
    <groupId>jakarta.json</groupId>
    <artifactId>jakarta.json-api</artifactId>
    <version>2.1.3</version>
</dependency>

Step 2: Parse the JSON String

import jakarta.json.Json;
import jakarta.json.JsonObject;
import jakarta.json.JsonReader;
import java.io.StringReader;
public class SimpleJsonParser {
    public static void main(String[] args) {
        String jsonString = """
                {
                  "userName": "John Doe",
                  "age": 30,
                  "isActive": true,
                  "address": {
                    "street": "123 Main St",
                    "city": "New York"
                  }
                }
                """;
        // Use try-with-resources to automatically close the reader
        try (JsonReader jsonReader = Json.createReader(new StringReader(jsonString))) {
            // The entire JSON is read as a JsonObject
            JsonObject jsonObject = jsonReader.readObject();
            // Get simple values
            String name = jsonObject.getString("userName");
            int age = jsonObject.getInt("age");
            boolean isActive = jsonObject.getBoolean("isActive");
            System.out.println("Name: " + name);
            System.out.println("Age: " + age);
            System.out.println("Is Active: " + isActive);
            // Get a nested JsonObject
            JsonObject address = jsonObject.getJsonObject("address");
            String city = address.getString("city");
            System.out.println("City: " + city);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

Output:

Name: John Doe
Age: 30
Is Active: true
City: New York

Summary: Which One to Choose?