Jsonparseexception: Illegal unquoted character ((CTRL-CHAR, code 10)

java

json-parsing

error-handling

best-practices

byAnton Shumikhin·Feb 27, 2025

When facing a JsonParseException due to an illegal unquoted character (CTRL-CHAR, code 10), you're dealing with unescaped line breaks in your JSON. You need to replace newline characters with the escaped version \\n in your JSON strings.

Correct example:

String jsonString = "{\"key\": \"value on line1\\nvalue on line2\"}";

Always ensure your JSON strings have all control characters sufficiently escaped to guarantee a smooth parsing process.

Preventing issues with control characters

Control characters may sneak into JSON strings via user input or data imports. Correct problematic strings by replacing or escaping these invisible tricksters:

// Tossing control characters out of the club 🏌️
jsonString = jsonString.replace("\n", "\\n")
                       .replace("\r", "\\r");

You can also train object mappers like Jackson to tolerate certain characters, but use with care:

ObjectMapper mapper = new ObjectMapper();
// Jackson turning a blind eye to the charlatans 🙈
mapper.configure(JsonReadFeature.ALLOW_UNESCAPED_CONTROL_CHARS.mappedFeature(), true);

Remember: Allowing control characters might open doors to security risks or database mayhem.

Solidifying your JSON handling game

Correctly formatting JSON strings does more than just averting errors. It's also key to preserving data integrity and ensuring your application chats seamlessly with APIs or data warehouses. Here are some field-tested strategies:

Confirm the integrity of your JSON before trying to process or transmit it.
Use purpose-built libraries and automated tools to take care of escaping control characters. StringEscapeUtils from Apache Commons Lang can help here.
Where needed, customize object mappers judiciously to endure minor syntax violations - knowing the risks is crucial.

Decoding error messages

Error messages are your code's cry for help. A JsonParseException:

com.fasterxml.jackson.core.JsonParseException: Illegal unquoted character ((CTRL-CHAR, code 10)): has to be escaped using backslash

... basically says that your JSON broke the parser’s heart because it found a character that breaks the rules. It even points you to the exact location of the oversight, helping you make things right again.

Staying abreast with technology changes

Programming libraries and best practices evolve, and so should you. Here's what changes mean in practice:

Advancements in libraries like Jackson lead to phasing out of older features like JsonParser.Feature.ALLOW_UNQUOTED_CONTROL_CHARS in favor of latest ones like JsonReadFeature.ALLOW_UNESCAPED_CONTROL_CHARS.
Adjust your code to stay current and avoid dependencies on deprecated features - they are prone to eventual removal.

Adapting to changes not only safeguards against JsonParseException, but also powers a robust and future-proof application.

Continuous learning with trusted resources

JSON mastery is a constant journey:

From Javadocs to GitHub threads - turn to reliable resources associated with libraries you're using. They are gold mines for troubleshooting and understanding JSON formatting norms.
Make good use of online validators to rigorously test JSON strings - better safe than sorry.
Stay up-to-date with latest RFC specifications and cutting-edge community best practices - it's business as usual in the world of programming.