FasterXML/jackson-databind · error · IllegalArgumentException

maxProblems must be positive, was: ${maxProblems}

Error message

maxProblems must be positive, was: ${maxProblems}

What it means

Thrown by the CollectingProblemHandler constructor when maxProblems is <= 0. This handler accumulates deserialization problems up to a cap; a non-positive cap is meaningless (it would collect nothing or be unbounded by mistake), so the constructor rejects it.

Source

Thrown at src/main/java/tools/jackson/databind/deser/CollectingProblemHandler.java:110

     * Maximum number of problems to collect before stopping.
     */
    private final int _maxProblems;

    /**
     * Constructs a handler with the default maximum problem limit.
     */
    public CollectingProblemHandler() {
        this(DEFAULT_MAX_PROBLEMS);
    }

    /**
     * Constructs a handler with a specific maximum problem limit.
     *
     * @param maxProblems Maximum number of problems to collect (must be positive)
     */
    public CollectingProblemHandler(int maxProblems) {
        if (maxProblems <= 0) {
            throw new IllegalArgumentException("maxProblems must be positive, was: " + maxProblems);
        }
        _maxProblems = maxProblems;
    }

    /**
     * Gets the maximum number of problems this handler will collect.
     */
    public int getMaxProblems() {
        return _maxProblems;
    }

    /**
     * Retrieves the problem collection bucket from context attributes.
     *
     * @return Problem bucket, or null if not in collecting mode
     */
    @SuppressWarnings("unchecked")
    public static List<CollectedProblem> getBucket(DeserializationContext ctxt) {

View on GitHub (pinned to 87876ca5c0)

Solutions

1. Pass a strictly positive integer (e.g. CollectingProblemHandler.DEFAULT_MAX_PROBLEMS or a sensible cap like 100).
2. Validate configuration before construction: if the configured limit is <= 0, fall back to the default.
3. Treat 0/empty as 'use default' rather than passing it through.

Example fix

// before
int cap = config.getInt("max.problems", 0);
handler = new CollectingProblemHandler(cap);

// after
int cap = config.getInt("max.problems", CollectingProblemHandler.DEFAULT_MAX_PROBLEMS);
if (cap <= 0) cap = CollectingProblemHandler.DEFAULT_MAX_PROBLEMS;
handler = new CollectingProblemHandler(cap);

int cap = configuredMaxProblems;
if (cap <= 0) cap = CollectingProblemHandler.DEFAULT_MAX_PROBLEMS;
handler = new CollectingProblemHandler(cap);

When it happens

Trigger: Constructing new CollectingProblemHandler(0) or new CollectingProblemHandler(negative), or computing the cap from user input/configuration that resolves to zero or a negative number.

Common situations: Reading a 'max problems' limit from config where the default is unset (0); passing a size derived from a collection length that is empty; arithmetic that underflows; misinterpreting 0 as 'unlimited'.

Related errors

• Cannot pass null modifier
• Cannot pass null resolver
• Cannot pass null resolver
• Cannot deserialize Class ${type.getName()} (of type ${typeSt
• `DeserializationProblemHandler.handleNullForPrimitives()` fo

AI-assisted analysis of FasterXML/jackson-databind@87876ca5c0 (2026-08-11). Data as JSON: /api/errors/78d61cb6de82ab9a. Report an issue: GitHub.