What causes "The maximum allowed length must be greater than 0" in flowable/flowable-engine?

Pass a positive integer for maxAllowedLength (e.g. the DB column length, commonly 4001 for text columns)

flowable/flowable-engine · error · FlowableIllegalArgumentException

The maximum allowed length must be greater than 0

Error message

The maximum allowed length must be greater than 0

What it means

Constructor guard: MaxAllowedLengthVariableVerifier rejects a configured maximum length of zero or negative at construction time. The verifier exists to enforce DB column length limits for variables; an unusable limit is refused immediately.

Source

Thrown at modules/flowable-engine-common/src/main/java/org/flowable/common/engine/impl/variable/MaxAllowedLengthVariableVerifier.java:30

 */
package org.flowable.common.engine.impl.variable;

import org.apache.commons.lang3.StringUtils;
import org.flowable.common.engine.api.FlowableIllegalArgumentException;
import org.flowable.common.engine.api.scope.ScopeTypes;
import org.flowable.variable.api.types.ValueFields;
import org.flowable.variable.api.types.VariableType;

/**
 * @author Filip Hrisafov
 */
public class MaxAllowedLengthVariableVerifier implements VariableLengthVerifier {

    protected final int maxAllowedLength;

    public MaxAllowedLengthVariableVerifier(int maxAllowedLength) {
        if (maxAllowedLength <= 0) {
            throw new FlowableIllegalArgumentException("The maximum allowed length must be greater than 0");
        }
        this.maxAllowedLength = maxAllowedLength;
    }

    @Override
    public void verifyLength(int length, ValueFields valueFields, VariableType variableType) {
        if (length > maxAllowedLength) {
            String scopeId;
            String scopeType;
            if (StringUtils.isNotEmpty(valueFields.getTaskId())) {
                scopeId = valueFields.getTaskId();
                scopeType = ScopeTypes.TASK;
            } else if (StringUtils.isNotEmpty(valueFields.getProcessInstanceId())) {
                scopeId = valueFields.getProcessInstanceId();
                scopeType = ScopeTypes.BPMN;
            } else {
                scopeId = valueFields.getScopeId();
                scopeType = valueFields.getScopeType();

View on GitHub (pinned to d6d39ce1c6)

Solutions

Pass a positive integer for maxAllowedLength (e.g. the DB column length, commonly 4001 for text columns)
Check the config property feeding the value — ensure it parses to the intended positive number
Remove/omit the verifier if no length limit is needed

Example fix

// before
new MaxAllowedLengthVariableVerifier(0);
// after
new MaxAllowedLengthVariableVerifier(4001);

Defensive patterns

Strategy: validation

Validate before calling

if (maxAllowedLength == null || maxAllowedLength <= 0)
    throw new IllegalArgumentException("maxAllowedLength must be > 0, got: " + maxAllowedLength);

Type guard

boolean isValidMaxLength(Integer len) {
    return len != null && len > 0;
}

Try / catch

try {
    new MaxAllowedLengthVariableVerifier(cfgLen);
} catch (FlowableIllegalArgumentException e) {
    logger.error("Invalid verifier limit, falling back to default", e);
    verifier = new MaxAllowedLengthVariableVerifier(4001);
}

Prevention

Wire the limit from the actual DB column size
Validate config properties parse to positive integers
Never use 0/-1 as placeholder limits

When it happens

Trigger: Creating a MaxAllowedLengthVariableVerifier (directly or via engine configuration wiring a variable length verifier) with maxAllowedLength <= 0.

Common situations: Configuration mistakes like 0 or -1 placeholders; computing the limit from a property that failed to parse; copy-paste of the wrong constant.

Understand the failure class

Background: "Invalid value" and "allowed values are" config errors: what your library rejected and how to fix it — this error's family across 41 libraries.

Related errors

AI-assisted analysis of flowable/flowable-engine@d6d39ce1c6 (2026-09-11). Data as JSON: /api/errors/7f9bd27d6ff35837. Report an issue: GitHub.