Error: DynamoDB could not invoke null on class

In legacy Java DynamoDBMapper, “could not invoke null on class” can mean the mapper found no matching setter for a mapped property. The word null may describe the reflected method, not the object being loaded. Inspect the nested mapping exception and the named model class.

1. Ensure each mapped mutable property has public bean-style getters and setters with matching types, such as String getId() and void setId(String id).
2. Check overloaded setters, primitive versus boxed types, boolean accessor naming, and generated Lombok methods. Inspect the compiled class if generated code differs from the source.
3. Provide a public no-argument constructor for mutable models. Mark calculated properties as ignored if they should not be persisted.
4. If the setter exists but throws, fix the exception inside it rather than treating every invocation failure as a missing method.

DynamoDBMapper is part of AWS SDK for Java 1.x. In Java 2.x, use the Enhanced Client’s bean schema with matching accessors, or an immutable schema with its builder. Do not mix old and new annotation packages.

See Java mapping examples and the legacy mapper reflection implementation.