flowable/flowable-engine · error · IllegalArgumentException

input clause is required

Error message

input clause is required

What it means

ELExpressionExecutor.executeInputExpression validates its DMN model arguments before evaluation and throws IllegalArgumentException when inputClause is null (also for null input expression or input entry). It ensures the executor never evaluates a malformed input clause.

Source

Thrown at modules/flowable-dmn-engine/src/main/java/org/flowable/dmn/engine/impl/el/ELExpressionExecutor.java:34

import org.flowable.common.engine.impl.el.ExpressionManager;
import org.flowable.dmn.engine.FlowableDmnExpressionException;
import org.flowable.dmn.model.InputClause;
import org.flowable.dmn.model.LiteralExpression;
import org.flowable.dmn.model.OutputClause;
import org.flowable.dmn.model.UnaryTests;
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);

View on GitHub (pinned to d6d39ce1c6)

Solutions

1. Fix the DMN XML so every <input> has an <inputExpression> and each rule has a non-empty <inputEntry>.
2. Validate DMN resources against the DMN XSD before deployment.
3. In programmatic model building, populate InputClause, its input expression, and InputEntry objects before execution.
4. Catch IllegalArgumentException during decision execution and report which rule/clause is malformed.

Example fix

// before
InputClause clause = null; // never populated
Boolean hit = ELExpressionExecutor.executeInputExpression(clause, entry, em, ctx);
// after
InputClause clause = new InputClause();
clause.setInputExpression(new LiteralExpression());
clause.getInputExpression().setText("${amount}");
Boolean hit = ELExpressionExecutor.executeInputExpression(clause, entry, em, ctx);

if (inputClause == null || inputClause.getInputExpression() == null || inputEntry == null) {
    throw new IllegalArgumentException("Input clause, input expression and input entry must all be set");
}

try {
    Boolean hit = ELExpressionExecutor.executeInputExpression(clause, entry, expressionManager, ctx);
} catch (IllegalArgumentException e) {
    log.warn("Malformed DMN input structure: {}", e.getMessage());
}

When it happens

Trigger: Executing a decision table whose rule/input structure is incomplete: an input entry or InputClause object is null because the DMN XML was malformed (missing <inputExpression> or <inputEntry>) or programmatically built DMN model objects were left partially populated.

Common situations: Generated or hand-edited DMN missing input expression elements; custom DMN model construction in tests; parser bugs/older DMN 1.0 files missing required elements that the executor assumes.

Understand the failure class

Background: "missing required argument" and "the following required arguments were not provided": what required-argument errors mean and how to fix them — this error's family across 20 libraries.

Related errors

• decisionKey is null
• decisionKey is null
• decisionKey is null
• deploymentId is null
• resourceName is null

AI-assisted analysis of flowable/flowable-engine@d6d39ce1c6 (2026-09-11). Data as JSON: /api/errors/797fb59925ad1532. Report an issue: GitHub.