How to pretty print JSON using Jackson in Java

In this short article, you'll learn how to use Jackson to enable pretty print JSON output.

By default, Jackson outputs the final JSON in the compact format:

try {
    // create user object
    User user = new User("John Doe", "john.doe@example.com",
            new String[]{"Member", "Admin"}, true);

    // convert user object to JSON
    String json = new ObjectMapper().writeValueAsString(user);

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

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

Here is what the generated JSON looks like:

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

To enable the pretty print JSON output while serializing a Java Object, you can use the writerWithDefaultPrettyPrinter() method of ObjectMapper:

try {
    // create user object
    User user = new User("John Doe", "john.doe@example.com",
            new String[]{"Member", "Admin"}, true);

    // create object mapper instance
    ObjectMapper mapper = new ObjectMapper();

    // convert user object to pretty print JSON
    String json = mapper.writerWithDefaultPrettyPrinter().writeValueAsString(user);

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

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

Now here is what the final pretty print JSON looks like:

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

You can also enable the pretty print JSON output globally by using the DefaultPrettyPrinter class, as shown below:

try {
    // create user object
    User user = new User("John Doe", "john.doe@example.com",
            new String[]{"Member", "Admin"}, true);

    // create object mapper instance
    ObjectMapper mapper = new ObjectMapper();

    // create an instance of DefaultPrettyPrinter
    ObjectWriter writer = mapper.writer(new DefaultPrettyPrinter());

    // convert user object to pretty print JSON
    String json = writer.writeValueAsString(user);

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

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

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

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