spring中bean的singleton属性

1.  UserDao.java

package com.lxh.springSingleton;

public interface UserDao {
	// 保存User
	public void save();
}

2.  UserDaoImpl.java

package com.lxh.springSingleton;

public class UserDaoImpl implements UserDao {

	@Override
	public void save() {
		System.out.println("save user ...");
	}

}

3.  UserService.java

package com.lxh.springSingleton;

import org.apache.log4j.Logger;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

public class UserService {
	// ApplicationContext
	public static ApplicationContext context = new ClassPathXmlApplicationContext(
			UserService.class.getResource("").toString()
					+ "/applicationContext.xml");
	// 日志
	private static Logger logger = Logger.getLogger(UserService.class);
	// 属性
	private UserDao userDaoImpl;

	// set,get
	public UserDao getUserDaoImpl() {
		return userDaoImpl;
	}

	public void setUserDaoImpl(UserDao userDaoImpl) {
		this.userDaoImpl = userDaoImpl;
	}

	// userService
	public static void main(String[] args) {
		System.out.println();
		UserService us = (UserService) context.getBean("userService");
		UserService us2 = (UserService) context.getBean("userService");

		logger.info("*****"+us +","+us2+"*****");
		logger.info("*****"+us.userDaoImpl+","+us2.userDaoImpl+"*****");

	}
}

4.  applicationContext.xml (singleton="false")

<?xml version="1.0" encoding="GBK"?>
<!DOCTYPE beans PUBLIC "-//SPRING//DTD BEAN//EN" "http://www.springframework.org/dtd/spring-beans.dtd">
<beans>
	<bean id="userDao" class="com.lxh.springSingleton.UserDaoImpl" singleton="false"/>
	<bean id="userService" class="com.lxh.springSingleton.UserService" singleton="false">
		<property name="userDaoImpl" ref="userDao"/>
	</bean>
</beans>

5.  applicationContext.xml (singleton="true")

<?xml version="1.0" encoding="GBK"?>
<!DOCTYPE beans PUBLIC "-//SPRING//DTD BEAN//EN" "http://www.springframework.org/dtd/spring-beans.dtd">
<beans>
	<bean id="userDao" class="com.lxh.springSingleton.UserDaoImpl" singleton="true"/>
	<bean id="userService" class="com.lxh.springSingleton.UserService" singleton="true">
		<property name="userDaoImpl" ref="userDao"/>
	</bean>
</beans>

6.  singleton="false" 运行结果

7.  singleton="true"  运行结果

8.  小结：

通过以上分析可以得出结论：在spring的bean配置中，若singleton=“false”，则该bean为非单例，即每请求一次，就会重新创建一个；若singleton=“true”则结论相反。

补充：默认情况下，singleton=“true”.