Convert JSON String to Map using Jackson

In this short article, you'll learn how to convert a JSON string to a Map in Java and vice versa using the Jackson library.

Dependencies

To add Jackson to your Gradle project, add the following dependency to the build.gradle file:

implementation 'com.fasterxml.jackson.core:jackson-databind:2.10.0'

For Maven, include the below dependency to your pom.xml file:

<dependency>
    <groupId>com.fasterxml.jackson.core</groupId>
    <artifactId>jackson-databind</artifactId>
    <version>2.10.0</version>
</dependency>

Convert JSON String to Map

To convert a JSON string to a Java Map with the same properties and keys, you can use the readValue() method from ObjectMapper:

try {
    // JSON string
    String json = "{\"name\":\"John Doe\",\"email\":\"john.doe@example.com\"," +
            "\"roles\":[\"Member\",\"Admin\"],\"admin\":true}";

    // convert a JSON string to Java Map
    Map<String, Object> map = new ObjectMapper().readValue(json, Map.class);

    // print map keys and values
    for (Map.Entry<String, Object> entry : map.entrySet()) {
        System.out.println(entry.getKey() + "=" + entry.getValue());
    }

} catch (Exception ex) {
    ex.printStackTrace();
}

You should see the following output printed on the console:

name=John Doe
email=john.doe@example.com
roles=[Member, Admin]
admin=true

To convert a JSON string stored in a file into a Java map, you can pass an instance of File to readValue():

Map<String, Object> map = new ObjectMapper().readValue(
        Paths.get("user.json").toFile(), 
        Map.class
);

Convert Map to JSON String

To convert a Java Map to a JSON string, you can use the writeValueAsString() method from the ObjectMapper class:

try {
    // create a map
    Map<String, Object> map = new HashMap<>();
    map.put("name", "John Deo");
    map.put("email", "john.doe@example.com");
    map.put("roles", new String[]{"Member", "Admin"});
    map.put("admin", true);

    // convert map to JSON string
    String json = new ObjectMapper().writeValueAsString(map);

    // print JSON string
    System.out.println(json);

} catch (Exception ex) {
    ex.printStackTrace();
}

You should see the following JSON printed on the console:

{"roles":["Member","Admin"],"name":"John Deo","admin":true,"email":"john.doe@example.com"}

If you want to write the converted Map directly to a JSON file, use the writeValue() method instead:

new ObjectMapper().writeValue(Paths.get("user.json").toFile(), map);

For more Jackson examples, check out the How to read and write JSON using Jackson in Java tutorial.

✌️ Like this article? Follow me on Twitter and LinkedIn. You can also subscribe to RSS Feed.

You might also like...

Digital Ocean

The simplest cloud platform for developers & teams. Start with a $200 free credit.

Buy me a coffee ☕

If you enjoy reading my articles and want to help me out paying bills, please consider buying me a coffee ($5) or two ($10). I will be highly grateful to you ✌️

Enter the number of coffees below:

✨ Learn to build modern web applications using JavaScript and Spring Boot

I started this blog as a place to share everything I have learned in the last decade. I write about modern JavaScript, Node.js, Spring Boot, core Java, RESTful APIs, and all things web development.

The newsletter is sent every week and includes early access to clear, concise, and easy-to-follow tutorials, and other stuff I think you'd enjoy! No spam ever, unsubscribe at any time.