Bean实例化的三种方式

Bean实例化的三种方式

ApplicationContext.xml文档：

<!-- 
			bean实例化三种方式：
			
					1. 用构造器来实例化 （掌握）
					2. 使用静态工厂方法实例化 （理解）
					3. 使用实例工厂方法实例化 （理解）
	 -->
	 
	 <!-- 1、用构造器来实例化：使用class的默认无参构造函数实例化
	 		 IUserDao userDao = new UserDaoImpl();
	  -->
	 <bean id ="userDao" class="spring.UserDaoImpl"></bean>
	 
	 <!-- 使用静态工厂方法实例化 
	 	  IUserDao userDao2= DaoStaticFactory.createUserDao();
	 -->
	 <bean id="userDao2" class="spring.factory.DaoStaticFactory" factory-method="createUserDao"></bean>
	 
	 <!-- 使用实例化工厂方法实例化
	 	  DaoNotStaticFactory factory = new DaoNotStaticFactory();
		  IUserDao userDao3= factory.createUserDao();
	  -->
	  <bean id="factory" class="spring.factory.DaoNotStaticFactory" ></bean>
	 <bean id="userDao3" factory-bean="factory"  factory-method="createUserDao"></bean>

实例化工厂：DaoNotStaticFactory

package spring.factory;

import spring.IUserDao;
import spring.UserDaoImpl;
/*
 * 实例工厂
 */
public class DaoNotStaticFactory {
	//DaoNotStaticFactory factory = new DaoNotStaticFactory();
	//IUserDao userDao3= factory.createUserDao();
	public IUserDao createUserDao() {
		return new UserDaoImpl();
	}

}

静态实例化工厂：DaoStaticFactory

package spring.factory;

import spring.IUserDao;
import spring.UserDaoImpl;

/*
 * 静态工厂：方法使用static修饰
 */
public class DaoStaticFactory {
	//IUserDao userDao2= DaoStaticFactory.createUserDao();
	public static IUserDao createUserDao() {
		return new UserDaoImpl();
	}
	

}

test:

package spring.factory;

import org.springframework.context.support.ClassPathXmlApplicationContext;

import spring.IUserDao;

public class test {
	public static void main(String[] args) {
		//加载并解析ApplicationContext.xml
		ClassPathXmlApplicationContext 	factory=  new ClassPathXmlApplicationContext("applicationContext.xml");
		
		//获取工厂中的IUseDao对象
		IUserDao userDao= (IUserDao)factory.getBean("userDao");
		IUserDao userDao2= (IUserDao)factory.getBean("userDao2");
		IUserDao userDao3= (IUserDao)factory.getBean("userDao3");
		
		//掉用方法
		userDao.selectUser();
		userDao2.selectUser();
		userDao3.selectUser();
		
		//销毁对象
		factory.close();
	}

}