How to Convert String to JSON Object in Java

Learn how to convert String to JSON Object in Java using Jackson ObjectMapper with a simple example and readValue() method. Jackson provides the ObjectMapper class, which can deserialize a JSON string into a corresponding Java object.

Code Explanation (Step-by-Step)

Here, we create two classes: StudentDepartment, and ConvertStringToJson.
The StudentDepartment class contains two fields: branch and name. The @JsonProperty annotation is used to map JSON properties to these fields.
The stringToJsonData() method takes two parameters: a JSON string and the target class type, such as StudentDepartment.class.
Inside the stringToJsonData() method, we create an ObjectMapper object.
The mapper.readValue(string, clazz) method deserializes the JSON string into an object of the specified Java class.
Now the method returns the converted Java object.

Jackson Maven Dependency :-

				
					<dependency>
    <groupId>com.fasterxml.jackson.core</groupId>
    <artifactId>jackson-databind</artifactId>
    <version><!-- use the current version for your project --></version>
</dependency>

				
					import java.io.IOException;

import com.fasterxml.jackson.databind.ObjectMapper;

class StudentDepartment {

    private String branch;
    private String name;

    public String getBranch() {
        return branch;
    }

    public void setBranch(String branch) {
        this.branch = branch;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    @Override
    public String toString() {
        return "StudentDepartment{" +
                "branch='" + branch + '\'' +
                ", name='" + name + '\'' +
                '}';
    }
}

public class ConvertStringToJson {

    public static void main(String[] args) {

        String jsonString =
                "{\"branch\":\"Computer Science\",\"name\":\"Santosh\"}";

        try {
            StudentDepartment studentDepartment =
                    stringToJsonData(
                            jsonString,
                            StudentDepartment.class
                    );

            System.out.println(studentDepartment);

        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    private static <T> T stringToJsonData(
            String jsonString,
            Class<T> clazz) throws IOException {

        ObjectMapper mapper = new ObjectMapper();
        return mapper.readValue(jsonString, clazz);
    }
}

Output :-
StudentDepartment{branch=’Computer Science’, name=’Santosh’}

Handle Invalid JSON Strings in Java

				
					import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.databind.ObjectMapper;

class Student {

    private int id;
    private String name;

    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 class InvalidJsonExample {

    public static void main(String[] args) {

        // Invalid JSON String
        String jsonString = "{\"id\":101,\"name\":\"Santosh\"";

        ObjectMapper mapper = new ObjectMapper();

        try {

            Student student = mapper.readValue(jsonString, Student.class);

            System.out.println("Student ID: " + student.getId());
            System.out.println("Student Name: " + student.getName());

        } catch (JsonProcessingException e) {

            System.out.println("Invalid JSON String");
            System.out.println("Error: " + e.getMessage());
        }
    }
}
``

Output :-
Invalid JSON String
Error: …

Is @JsonProperty required here?

No. Because your JSON property names and Java field names are already identical, Jackson can map them without @JsonProperty.
It becomes particularly useful when the names are different. For example:

				
					@JsonProperty("student_name")
private String name;

				
					{
  "student_name": "Santosh"
}

Handle Invalid JSON Strings in Java

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