Android Room Generic Dao

AppDao.java

import android.arch.persistence.db.SimpleSQLiteQuery;
import android.arch.persistence.db.SupportSQLiteQuery;
import android.arch.persistence.room.Dao;
import android.arch.persistence.room.Delete;
import android.arch.persistence.room.Insert;
import android.arch.persistence.room.OnConflictStrategy;
import android.arch.persistence.room.RawQuery;

import java.lang.reflect.ParameterizedType;
import java.util.List;

@Dao
public abstract class AppDao<T> {

    @Insert(onConflict = OnConflictStrategy.REPLACE)
    public abstract long save(T obj);

    @Insert(onConflict = OnConflictStrategy.REPLACE)
    public abstract long[] save(T... objs);

    @Insert(onConflict = OnConflictStrategy.FAIL)
    public abstract long insert(T obj);

    @Insert(onConflict = OnConflictStrategy.FAIL)
    public abstract long[] insert(T... objs);

    @Delete
    public abstract void delete(T obj);

    public int deleteAll() {
        SimpleSQLiteQuery query = new SimpleSQLiteQuery(
            "delete from " + getTableName()
        );
        return doDeleteAll(query);
    }

    public List<T> findAllValid() {
        SimpleSQLiteQuery query = new SimpleSQLiteQuery(
            "select * from " + getTableName() + " where deleteFlag = 0 order by sortKey"
        );
        return doFindAllValid(query);
    }

    public T find(long id) {
        SimpleSQLiteQuery query = new SimpleSQLiteQuery(
            "select * from " + getTableName() + " where deleteFlag = 0 and id = ?",
            new Object[]{id}
        );
        return doFind(query);
    }

    public String getTableName() {

        Class clazz = (Class)
            ((ParameterizedType) getClass().getSuperclass().getGenericSuperclass())
                .getActualTypeArguments()[0];
        // tableName = StringUtil.toSnakeCase(clazz.getSimpleName());
        String tableName = clazz.getSimpleName();
        return tableName;
    }

    @RawQuery
    protected abstract List<T> doFindAllValid(SupportSQLiteQuery query);

    @RawQuery
    protected abstract T doFind(SupportSQLiteQuery query);

    @RawQuery
    protected abstract int doDeleteAll(SupportSQLiteQuery query);
}

UserDao.java

package com.swalloworks.rakurakukakeibo.system;

import android.arch.persistence.room.Dao;

import com.swalloworks.rakurakukakeibo.base.AppDao;

/**
 * Remember to keep the generic/class information in your proguard-rules.pro
 */
@Dao
public abstract class UserDao extends AppDao<User> {
}

hi, i'm using this method but i faced with this error:
Cannot use unbound generics in Dao classes. If you are trying to create a base DAO, create a normal class, extend it with type params then mark the subclass with @dao.
any suggestion why?

Cannot use unbound generics in Dao classes. If you are trying to create a base DAO, create a normal class, extend it with type params then mark the subclass with @dao.

My guess is that you are using a Dao class without generic/class information.
The AppDao above can NOT be used directly, just the UserDao can.