spring-Bean的实例化

✨博客主页：👉 不会压弯的小飞侠 ✨欢迎关注：👉点赞🎀收藏⭐留言✒ ✨系列专栏：👉 Spring专栏 ✨如果觉得博主的文章还不错的话，请三连支持一下博主。 ✨欢迎大佬指正，一起学习！一起加油！

🔥提供可访问的构造方法：

package com.study.dao.impl;
import com.study.dao.BookDao;
public class BookDaoImpl implements BookDao { 
    public BookDaoImpl() { 
        System.out.println("无参构造！");
    }

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

🔥配置：

<bean id="bookDao"  class="com.study.dao.impl.BookDaoImpl" ></bean>

注意： ⭐⭐⭐：如果无参构造方法不存在则抛出BeabCreationException。

🔥静态工厂

package com.study.factory;
import com.study.dao.BookDao;
import com.study.dao.impl.BookDaoImpl;
public class BookDaoFactory { 
    public static BookDao getBookDao(){ 
        return new BookDaoImpl();
    }
}

🔥配置

<bean id="bookDao" name="dao" class="com.study.factory.BookDaoFactory" factory-method="getBookDao"></bean>

🔥实例化工厂

package com.study.factory;
import com.study.dao.BookDao;
import com.study.dao.impl.BookDaoImpl;
public class BookDaoFactory { 
    public  BookDao getBookDao(){ 
        return new BookDaoImpl();
    }
}

}

🔥配置

<bean id="bookDao" name="dao" class="com.study.factory.BookDaoFactory"></bean>
    <bean id="book" factory-method="getBookDao" factory-bean="bookDao"></bean>

🔥FactoryBean

package com.study.factory;
import com.study.dao.BookDao;
import com.study.dao.impl.BookDaoImpl;
import org.springframework.beans.factory.FactoryBean;
public class BookDaoFactoryBean implements FactoryBean<BookDao> { 
    public BookDao getObject() throws Exception { 
        return new BookDaoImpl();
    }

    public Class<?> getObjectType() { 
        return BookDao.class;
    }
}

🔥配置

<bean id="bookDao" class="com.study.factory.BookDaoFactoryBean"></bean>