1.构造方法造对象

    <!--方式一：构造方法实例化bean-->
    <bean id="bookDao" class="com.itheima.dao.impl.BookDaoImpl"/>

public interface BookDao {
    public void save();
}

import com.itheima.dao.BookDao;

public class BookDaoImpl implements BookDao {

    public BookDaoImpl() {
        System.out.println("book dao constructor is running ....");
    }

    public void save() {
        System.out.println("book dao save ...");
    }

}

import com.itheima.dao.BookDao;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

public class AppForInstanceBook {
    public static void main(String[] args) {
        ApplicationContext ctx = new ClassPathXmlApplicationContext("applicationContext.xml");
        BookDao bookDao = (BookDao) ctx.getBean("bookDao");
        bookDao.save();
    }
}

运行结果

book dao constructor is running ....
book dao save ...