greenrobot/greenDAO · error · RuntimeException

Property already defined:

Error message

Property already defined: 

What it means

Entity.addProperty keeps a set of property names and throws if the name was already added. Duplicate property names would produce invalid generated Java/SQL, so the schema DSL rejects them at definition time. All addXxxProperty helpers (addBooleanProperty, addIntProperty, etc.) funnel through addProperty.

Solutions

1. Remove or rename the duplicate addXxxProperty call so each property name is unique per entity.
2. If you intended a primary key, use addIdProperty() once instead of adding a separate "id" property.
3. Keep entity schema definitions in one place to avoid split definitions across files/branches.
4. Track property names in a constant list and generate the calls to guarantee uniqueness.

Example fix

// before
entity.addIdProperty();
entity.addLongProperty("id"); // duplicate
// after
entity.addIdProperty(); // single definition

Set<String> seen = new HashSet<>();
for (String name : propertyNames) {
    if (!seen.add(name)) throw new IllegalArgumentException("Duplicate property: " + name);
}

try {
    entity.addIntProperty("id");
} catch (RuntimeException e) {
    if (e.getMessage().startsWith("Property already defined")) {
        log.warn("Skipping duplicate property: " + e.getMessage());
        return;
    }
    throw e;
}

When it happens

Trigger: Calling entity.addIntProperty("id") twice, or combining addIdProperty() with an explicit addLongProperty("id") / addProperty(PropertyType.Long, "id") on the same entity.

Common situations: Copy-pasting entity definitions; adding a custom property that collides with an implicit id property; merging schema code from branches where both defined the same column; refactoring where a base entity helper is invoked along with a manual duplicate.

Understand the failure class

Background: Schema validation failed / invalid input schema: payload rejected because its shape doesn't match the expected schema — this error's family across 28 libraries.

Related errors

• Duplicate property ordinals
• Interface defined more than once:
• Duplicate name for
• Property does not exist in
• AUTOINCREMENT is only available to primary key properties…

AI-assisted analysis of greenrobot/greenDAO@0bbb338e17 (2026-09-08). Data as JSON: /api/errors/7bd234d02c51735e. Report an issue: GitHub.

Appendix: source

Thrown at DaoGenerator/src/org/greenrobot/greendao/generator/Entity.java:143

    public PropertyBuilder addDoubleProperty(String propertyName) {
        return addProperty(PropertyType.Double, propertyName);
    }

    public PropertyBuilder addByteArrayProperty(String propertyName) {
        return addProperty(PropertyType.ByteArray, propertyName);
    }

    public PropertyBuilder addStringProperty(String propertyName) {
        return addProperty(PropertyType.String, propertyName);
    }

    public PropertyBuilder addDateProperty(String propertyName) {
        return addProperty(PropertyType.Date, propertyName);
    }

    public PropertyBuilder addProperty(PropertyType propertyType, String propertyName) {
        if (!propertyNames.add(propertyName)) {
            throw new RuntimeException("Property already defined: " + propertyName);
        }
        PropertyBuilder builder = new PropertyBuilder(schema, this, propertyType, propertyName);
        properties.add(builder.getProperty());
        return builder;
    }

    /** Adds a standard _id column required by standard Android classes, e.g. list adapters. */
    public PropertyBuilder addIdProperty() {
        PropertyBuilder builder = addLongProperty("id");
        builder.dbName("_id").primaryKey();
        return builder;
    }

    /** Adds a to-many relationship; the target entity is joined to the PK property of this entity (typically the ID). */
    public ToMany addToMany(Entity target, Property targetProperty) {
        Property[] targetProperties = {targetProperty};
        return addToMany(null, target, targetProperties);
    }

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