// 提供 mongo 實作的 Dao
@Module
public class DaoMongoModule {
    @Provides
    Dao getDaoMongoImpl(){
        return new DaoMongoImpl();
    }
}

// 提供 Mysql 實作的 Dao
@Module
public class DaoMysqlModule {
    @Provides
    Dao getDaoMysqlImpl(){
        return new DaoMysqlImpl();
    }
}

// 注入 Mongo 實作的 Dao 的 component
@Component(modules = {DaoMongoModule.class})
public interface BusinessMongoComponent {
    void inject(Business business);
}

// 注入 Mysql 實作的 Dao 的 component
@Component(modules = {DaoMysqlModule.class})
public interface BusinessMysqlComponent {
    void inject(Business business);
}

public class Main {
    public static void main(String []args){
        // 產生底層 Dao 是用 Mongo 實作的 Business 物件
        Business businessMongo = new Business();
        DaggerBusinessMongoComponent.create().inject(businessMongo);

        // 產生底層 Dao 是用 Mysql 實作的 Business 物件
        Business businessMysql = new Business();
        DaggerBusinessMysqlComponent.create().inject(businessMongo);
    }
}