greenrobot/greenDAO · error · DaoException

Illegal date value: expected java.util.Date or Long for…

Error message

Illegal date value: expected java.util.Date or Long for value 

What it means

For properties typed java.util.Date, checkValueForType() accepts only a Date instance or a Long (epoch millis) and converts both to a long for storage. Any other value type (String, Integer, etc.) triggers this DaoException. The conversion exists because greenDAO stores dates as numeric timestamps.

Solutions

1. Parse the string to a Date first (e.g. new SimpleDateFormat("yyyy-MM-dd").parse(value)) and pass the Date.
2. Pass epoch milliseconds as a Long instead.
3. Check the property type in the generated Properties class; only Date-typed properties enforce this rule.

Example fix

// before
queryBuilder.where(UserDao.Properties.CreatedAt.eq("2024-01-01")); // DaoException
// after
Date d = new SimpleDateFormat("yyyy-MM-dd").parse("2024-01-01");
queryBuilder.where(UserDao.Properties.CreatedAt.eq(d));

Object v = /* candidate */;
if (!(v instanceof java.util.Date || v instanceof Long)) {
  throw new IllegalArgumentException("Date property needs Date or Long");
}

boolean isDateValue(Object v) { return v instanceof java.util.Date || v instanceof Long; }

try { cond = Properties.CreatedAt.eq(v); } catch (DaoException e) { cond = Properties.CreatedAt.eq(parseDate(v)); }

When it happens

Trigger: where(Properties.CreatedAt.eq("2024-01-01")) or passing an Integer/other type to a condition on a Date-typed property.

Common situations: Passing dates as formatted strings from JSON/API payloads instead of parsing them to java.util.Date first.

Related errors

• Illegal value: found array, but simple object required
• Illegal boolean value: numbers must be 0 or 1, but was
• This operation only works with cached lazy lists
• Could not move to cursor location
• Loading of entity failed (null) at position

AI-assisted analysis of greenrobot/greenDAO@0bbb338e17 (2026-09-08). Data as JSON: /api/errors/4919399e8875b9ae. Report an issue: GitHub.

Appendix: source

Thrown at DaoCore/src/main/java/org/greenrobot/greendao/query/WhereCondition.java:84

                }
            }
        }
    }

    class PropertyCondition extends AbstractCondition {

        private static Object checkValueForType(Property property, Object value) {
            if (value != null && value.getClass().isArray()) {
                throw new DaoException("Illegal value: found array, but simple object required");
            }
            Class<?> type = property.type;
            if (type == Date.class) {
                if (value instanceof Date) {
                    return ((Date) value).getTime();
                } else if (value instanceof Long) {
                    return value;
                } else {
                    throw new DaoException("Illegal date value: expected java.util.Date or Long for value " + value);
                }
            } else if (property.type == boolean.class || property.type == Boolean.class) {
                if (value instanceof Boolean) {
                    return ((Boolean) value) ? 1 : 0;
                } else if (value instanceof Number) {
                    int intValue = ((Number) value).intValue();
                    if (intValue != 0 && intValue != 1) {
                        throw new DaoException("Illegal boolean value: numbers must be 0 or 1, but was " + value);
                    }
                } else if (value instanceof String) {
                    String stringValue = ((String) value);
                    if ("TRUE".equalsIgnoreCase(stringValue)) {
                        return 1;
                    } else if ("FALSE".equalsIgnoreCase(stringValue)) {
                        return 0;
                    } else {
                        throw new DaoException(
                                "Illegal boolean value: Strings must be \"TRUE\" or \"FALSE\" (case insensitive), but was "

View on GitHub (pinned to 0bbb338e17)