JSON Beautifier Library for Java

Assuming you're starting out with an existing JSON string, then Jackson can do this for you:

ObjectMapper objectMapper = new ObjectMapper();objectMapper.configure(SerializationConfig.Feature.INDENT_OUTPUT, true);String originalJson = ...JsonNode tree = objectMapper .readTree(originalJson);String formattedJson = objectMapper.writeValueAsString(tree);

Update to previous answer by skaffman, with newer versions of Jackson (2+, I think). The second line of code is now:

objectMapper.configure(SerializationFeature.INDENT_OUTPUT, true);

With Jackson 2.6.1

String beautify(String json) throws IOException {    ObjectMapper mapper = new ObjectMapper();    Object obj = mapper.readValue(json, Object.class);    return mapper.writerWithDefaultPrettyPrinter().writeValueAsString(obj);}

pom.xml:

    <dependency>        <groupId>com.fasterxml.jackson.core</groupId>        <artifactId>jackson-core</artifactId>        <version>2.6.1</version>    </dependency>    <dependency>        <groupId>com.fasterxml.jackson.core</groupId>        <artifactId>jackson-databind</artifactId>        <version>2.6.1</version>    </dependency>

Convert JSON String to Pretty Print JSON output using Jackson