[Java知识库]Spring-ioc快速入门详解02

Spring-ioc快速入门详解02

bean实例化的三种方式

需要交给SpringIOC管理的对象并不都是自己new的,也就是说不能通过无参构造去实例化.

1. 无参构造方法实例化

<!--将对象交给ioc管理,默认为单例scope="singleton",需手动设置为多例-->
    <bean id="UserDao" class="com.kiui.dao.impl.UserDaoImpl" scope="prototype"/>

2. 工厂静态方法实例化
   applicationContext.xml注册bean

<bean id="UserDao" class="com.kiui.factory.StaticFactory" factory-method="getUserDao"/>

工厂类

package com.kiui.factory;
import com.kiui.dao.UserDao;
import com.kiui.dao.impl.UserDaoImpl;
/**
 * @author Kiui
 */
public class StaticFactory {
    public static UserDao getUserDao() {
        return new UserDaoImpl();
    }
}

3. 工厂方法实例化
   applicationContext.xml注册bean

    <bean id="factory" class="com.kiui.factory.DynamicFactory"/>
    <bean id="UserDao" factory-bean="factory" factory-method="getUserDao"/>

工厂类

package com.kiui.factory;
import com.kiui.dao.UserDao;
import com.kiui.dao.impl.UserDaoImpl;
/**
 * @author Kiui
 */
public class DynamicFactory {
    public UserDao getUserDao() {
        return new UserDaoImpl();
    }
}

测试代码

package com.kiui.demo;
import com.kiui.dao.UserDao;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;
/**
 * @author Kiui
 */
public class UserDaoDemo {
  public static void main(String[] args) {

    ApplicationContext app = new ClassPathXmlApplicationContext("applicationContext.xml");

    UserDao userDao = (UserDao) app.getBean("UserDao");

    userDao.save();

  }
}

控制台:

save running...