Java中不兼容的泛型类型

我在Java中有一个复杂的泛型类型实现，但我无法完成它.我在AddItemEvent节课上遇到了错误.getHandler中的返回类型与其父类要求的类型不匹配.

AddItemEventHandler实际上是BaseEventHandler<BaseEvent<AddItemCommand, AddItemPayload>, AddItemCommand, AddItemPayload>，但我在这条线上得到了一个错误.

public abstract class BasePayload {
}

public class AddItemPayload extends BasePayload {
    private int id;
    private String name;
    public AddItemPayload(int id, String name) {
        this.id = id;
        this.name = name;
    }
    public int getId() {
        return id;
    }
    public String getName() {
        return name;
    }
}

public class BaseCommand<T extends BasePayload> {
    String command;
    T payload;

    public BaseCommand(String command, T payload) {
        this.command = command;
        this.payload = payload;
    }
}

public class AddItemCommand extends BaseCommand<AddItemPayload> {
    public AddItemCommand(AddItemPayload payload) {
        super("AddItem", payload);
    }
}


public abstract class BaseEventHandler<E extends BaseEvent<C, P>, C extends BaseCommand<P>, P extends BasePayload> {
    abstract public void onTry(E event, ArrayList<BaseEvent<?, ?>> actualEvents);
    abstract public void onCommit(String uuid, E event);
}

public class AddItemEventHandler extends BaseEventHandler<AddItemEvent, AddItemCommand, AddItemPayload> {
    @Override
    public void onTry(AddItemEvent event, ArrayList<BaseEvent<?, ?>> actualEvents) {
    }
    @Override
    public void onCommit(String uuid, AddItemEvent event) {
    }
}


public abstract class BaseEvent<C extends BaseCommand<P>, P extends BasePayload> {
    abstract protected BaseEventHandler<BaseEvent<C, P>, C, P> getHandler();
}

public class AddItemEvent extends BaseEvent<AddItemCommand, AddItemPayload> {
    @Override
    protected BaseEventHandler<BaseEvent<AddItemCommand, AddItemPayload>, AddItemCommand, AddItemPayload> getHandler() {
        return new AddItemEventHandler(); // I have an error on this line
        /*
        Incompatible types. Found: 'org.example.handlers.AddItemEventHandler',
        required: 'org.example.handlers.BaseEventHandler<org.example.events.BaseEvent<org.example.commands.AddItemCommand,org.example.payload.AddItemPayload>,
        org.example.commands.AddItemCommand,org.example.payload.AddItemPayload>'
        */
    }
}