flowable/flowable-engine · error · IllegalArgumentException

input entry is required

Error message

input entry is required

What it means

Thrown by ELExpressionExecutor.executeInputExpression when the inputEntry (UnaryTests) argument is null. The input entry holds the test expression that decides whether a rule row matches; without it the condition cannot be created, so the executor rejects the call immediately with an IllegalArgumentException.

Source

Thrown at modules/flowable-dmn-engine/src/main/java/org/flowable/dmn/engine/impl/el/ELExpressionExecutor.java:40

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * @author Yvo Swillens
 */
public class ELExpressionExecutor {

    private static final Logger LOGGER = LoggerFactory.getLogger(ELExpressionExecutor.class);

    public static Boolean executeInputExpression(InputClause inputClause, UnaryTests inputEntry, ExpressionManager expressionManager, ELExecutionContext executionContext) {
        if (inputClause == null) {
            throw new IllegalArgumentException("input clause is required");
        }
        if (inputClause.getInputExpression() == null) {
            throw new IllegalArgumentException("input expression is required");
        }
        if (inputEntry == null) {
            throw new IllegalArgumentException("input entry is required");
        }
        if (executionContext == null) {
            throw new IllegalArgumentException("execution context is required");
        }
        
        String inputExpression = inputClause.getInputExpression().getText();
        executionContext.checkExecutionContext(inputExpression);
        
        // pre parse expression
        String parsedExpression = ELInputEntryExpressionPreParser.parse(inputEntry.getText(), inputExpression, inputClause.getInputExpression().getTypeRef());

        Expression expression = expressionManager.createExpression(parsedExpression);
        RuleExpressionCondition condition = new RuleExpressionCondition(expression);
        
        try {
            return condition.evaluate(executionContext.getStackVariables(), executionContext);
        } catch (Exception ex) {
            LOGGER.warn("Error while executing input entry: {}", parsedExpression, ex);

View on GitHub (pinned to d6d39ce1c6)

Solutions

1. Provide a valid UnaryTests object (with getText() returning the test expression, e.g. "" or a literal) instead of null.
2. Verify every rule row in the decision table has one entry per input clause and fix the model/XML or row-mapping code.
3. If empty cells are legitimate, substitute an empty UnaryTests before calling rather than passing null.
4. Guard each argument for null before invoking the executor and skip or log the rule instead.

Example fix

// before
UnaryTests inputEntry = rule.getInputEntries().get(i); // may be null
Boolean hit = ELExpressionExecutor.executeInputExpression(clause, inputEntry, em, ctx);
// after
UnaryTests inputEntry = rule.getInputEntries().get(i);
if (inputEntry != null) {
    Boolean hit = ELExpressionExecutor.executeInputExpression(clause, inputEntry, em, ctx);
} else {
    // skip missing entry or substitute empty UnaryTests
}

if (inputEntry == null) {
    // skip rule, substitute empty UnaryTests, or raise a validation error
}

boolean hasInputEntry(UnaryTests e) { return e != null; }

try {
    ELExpressionExecutor.executeInputExpression(clause, entry, em, ctx);
} catch (IllegalArgumentException e) {
    if ("input entry is required".equals(e.getMessage())) {
        // rule row is missing an input entry: report row/clause index
    } else { throw e; }
}

When it happens

Trigger: Passing null as the second argument to ELExpressionExecutor.executeInputExpression — e.g. a rule row cell for that input column is absent or the parser produced no UnaryTests object for it.

Common situations: Custom decision-table evaluators iterating rule rows where some cells are empty/unparsed; DMN XML rule rows with fewer entries than input clauses; test code calling the executor with placeholder nulls.

Related errors

• input expression is required
• execution context is required
• output clause is required
• output entry is required
• <exception message from evaluation failure>

AI-assisted analysis of flowable/flowable-engine@d6d39ce1c6 (2026-09-11). Data as JSON: /api/errors/c779ccfa123264c1. Report an issue: GitHub.