greenrobot/greenDAO · error · DaoException

Could not init DAOConfig

Error message

Could not init DAOConfig

What it means

DaoConfig's constructor initializes keyIsNumeric and other metadata by reflecting over the entity and its Property fields; any Exception during this reflection (missing inner Properties class, illegal access, bad property types) is wrapped as DaoException "Could not init DAOConfig" with the cause attached. It happens when a DAO class is registered that greendao cannot reflect upon.

Solutions

1. Regenerate DAO classes: re-run the greendao Gradle plugin build / annotation processor so <Entity>$Properties matches the entity.
2. Inspect getCause() to see the underlying reflection error and fix the specific entity/property.
3. Clean and rebuild the project to remove stale generated sources.
4. Add ProGuard keep rules for generated classes: -keep class *$Properties { *; } and keep entity fields used by greendao.

Example fix

// after editing an entity, before: relying on stale generated code
// terminal:
./gradlew clean :app:generateGreenDaoSources :app:build
// build.gradle keep rule added:
-keepclassmembers class * extends org.greenrobot.greendao.Property { *; }

try {
    Class.forName(entityClass.getName() + "$Properties");
} catch (ClassNotFoundException e) {
    throw new IllegalStateException("DAO classes not generated for " + entityClass + "; run greendao generator");
}

try {
    daoSession = new DaoMaster(db).newSession();
} catch (DaoException e) {
    Throwable cause = e.getCause(); // reflection error naming the bad entity
    log.severe("DAOConfig init failed: " + cause + " — regenerate DAO classes");
}

When it happens

Trigger: Registering a DAO whose generated $Properties class is missing or out of sync with the entity (stale/failed annotation-processor run), a Property referencing a field type reflection can't resolve, or code changes to an entity without regenerating DAO classes.

Common situations: Editing an entity class after code generation (greenDAO generator/Gradle plugin) without regenerating; renaming entities so Foo$Properties no longer exists; ProGuard removing generated Property fields in release builds.

Related errors

• No DAO registered for
• Expected unique result, but count was
• Cannot delete entity, key is null
• Entity does not exist in the database anymore
• Cannot update entity without key - was it inserted before?

AI-assisted analysis of greenrobot/greenDAO@0bbb338e17 (2026-09-08). Data as JSON: /api/errors/b9b69861b740996d. Report an issue: GitHub.

Appendix: source

Thrown at DaoCore/src/main/java/org/greenrobot/greendao/internal/DaoConfig.java:94

            String[] nonPkColumnsArray = new String[nonPkColumnList.size()];
            nonPkColumns = nonPkColumnList.toArray(nonPkColumnsArray);
            String[] pkColumnsArray = new String[pkColumnList.size()];
            pkColumns = pkColumnList.toArray(pkColumnsArray);

            pkProperty = pkColumns.length == 1 ? lastPkProperty : null;
            statements = new TableStatements(db, tablename, allColumns, pkColumns);

            if (pkProperty != null) {
                Class<?> type = pkProperty.type;
                keyIsNumeric = type.equals(long.class) || type.equals(Long.class) || type.equals(int.class)
                        || type.equals(Integer.class) || type.equals(short.class) || type.equals(Short.class)
                        || type.equals(byte.class) || type.equals(Byte.class);
            } else {
                keyIsNumeric = false;
            }

        } catch (Exception e) {
            throw new DaoException("Could not init DAOConfig", e);
        }
    }

    private static Property[] reflectProperties(Class<? extends AbstractDao<?, ?>> daoClass)
            throws ClassNotFoundException, IllegalArgumentException, IllegalAccessException {
        Class<?> propertiesClass = Class.forName(daoClass.getName() + "$Properties");
        Field[] fields = propertiesClass.getDeclaredFields();

        ArrayList<Property> propertyList = new ArrayList<Property>();
        final int modifierMask = Modifier.STATIC | Modifier.PUBLIC;
        for (Field field : fields) {
            // There might be other fields introduced by some tools, just ignore them (see issue #28)
            if ((field.getModifiers() & modifierMask) == modifierMask) {
                Object fieldValue = field.get(null);
                if (fieldValue instanceof Property) {
                    propertyList.add((Property) fieldValue);
                }
            }

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