Spring基础:快速入门spring(8):bean scope
2016-11-27 10:48
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在这篇文章中我们会了解一下spring中bean scope, 并使用简单例子来看一下singleton和prototype的使用方法。
|特征|详细
|No.1|使用单态模式,只有一个实例
我们使用spring的reference的例子来具体说明。如上图所示,虽然在多处被使用,其实他们使用的单态方式提供的同一个实例。
bean scope
在spring中,bean的lifecyle大体如下所示种类 | 详细 |
---|---|
singleton | (Default) Scopes a single bean definition to a single object instance per Spring IoC container. |
prototype | Scopes a single bean definition to any number of object instances. |
request | Scopes a single bean definition to the lifecycle of a single HTTP request; that is, each HTTP request has its own instance of a bean created off the back of a single bean definition. Only valid in the context of a web-aware Spring ApplicationContext. |
session | Scopes a single bean definition to the lifecycle of an HTTP Session. Only valid in the context of a web-aware Spring ApplicationContext. |
globalSession | Scopes a single bean definition to the lifecycle of a global HTTP Session. Typically only valid when used in a Portlet context. Only valid in the context of a web-aware Spring ApplicationContext. |
application | Scopes a single bean definition to the lifecycle of a ServletContext. Only valid in the context of a web-aware Spring ApplicationContext. |
websocket | Scopes a single bean definition to the lifecycle of a WebSocket. Only valid in the context of a web-aware Spring ApplicationContext. |
singleton scope
singleton也是spring的default的scope,使用这种方式的bean的scope至少有如下的特征|特征|详细
|No.1|使用单态模式,只有一个实例
我们使用spring的reference的例子来具体说明。如上图所示,虽然在多处被使用,其实他们使用的单态方式提供的同一个实例。
修改spring设定文件
spring的default的方式,其实可以不必修改,但是为了方便,还是修改如下,将scope加入。<?xml version="1.0" encoding="UTF-8"?> <beans xmlns="http://www.springframework.org/schema/beans" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:context="http://www.springframework.org/schema/context" xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context.xsd"> <context:property-placeholder location="classpath:com/liumiao/demo/spring/Person.properties" /> <bean id="thePerson" class="com.liumiao.demo.spring.Student" init-method="initMethod" destroy-method="destroyMethod" scope="singleton"> <property name="teachingService" ref="theService"></property> <property name="name" value="${person.name}" /> <property name="country" value="${person.country}" /> </bean> <bean id="theService" class="com.liumiao.demo.spring.SwimmingTeachingService"> </bean> </beans>
修改TestDemo
为了更清楚地确认结果,修改TestDemo,来查看使用singleton的方式下,创建的bean到底是不是同一个。package com.liumiao.demo.spring; import com.liumiao.demo.spring.Person; import org.springframework.context.support.ClassPathXmlApplicationContext; public class TestDemo { public TestDemo() { } public static void main(String[] args) { ClassPathXmlApplicationContext context = new ClassPathXmlApplicationContext("classpath:com/liumiao/demo/spring/spring-cfg.xml"); Student person = (Student) context.getBean("thePerson", Person.class); System.out.println(person.sayhello()); System.out.println(person.provideTeachingService()); System.out.println(person.getCountry()); System.out.println(person.getName()); Student personB = (Student)context.getBean("thePerson",Person.class); if (person == personB){ System.out.println("person and personB point to the same object..."); }else{ System.out.println("person and personB point to the different object..."); } System.out.println("person object address" + person); System.out.println("personB object address" + personB); context.close(); } }
执行结果
重执行结果中可以清楚地看到,person和personB实际上使用的是同一个实例。十一月 27, 2016 10:38:31 上午 org.springframework.context.support.ClassPathXmlApplicationContext prepareRefresh 信息: Refreshing org.springframework.context.support.ClassPathXmlApplicationContext@25f38edc: startup date [Sun Nov 27 10:38:31 CST 2016]; root of context hierarchy 十一月 27, 2016 10:38:31 上午 org.springframework.beans.factory.xml.XmlBeanDefinitionReader loadBeanDefinitions 信息: Loading XML bean definitions from class path resource [com/liumiao/demo/spring/spring-cfg.xml] 十一月 27, 2016 10:38:32 上午 org.springframework.context.support.PropertySourcesPlaceholderConfigurer loadProperties 信息: Loading properties file from class path resource [com/liumiao/demo/spring/Person.properties] Student Default construct is called... Student: set method: SetName:liumiao.cn Student: set method: SetCountry:ChinaPRC 十一月 27, 2016 10:38:32 上午 org.springframework.context.support.ClassPathXmlApplicationContext doClose User customized init-method is called 信息: Closing org.springframework.context.support.ClassPathXmlApplicationContext@25f38edc: startup date [Sun Nov 27 10:38:31 CST 2016]; root of context hierarchy Hello, I am a student. I teach how to study... ChinaPRC liumiao.cn person and personB point to the same object... person object addresscom.liumiao.demo.spring.Student@167fdd33 personB object addresscom.liumiao.demo.spring.Student@167fdd33 User customized destroy-method is called
prototype确认
prototype方式如下,产生的是不同的实例。修改spring的设定文件
<?xml version="1.0" encoding="UTF-8"?> <beans xmlns="http://www.springframework.org/schema/beans" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:context="http://www.springframework.org/schema/context" xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context.xsd"> <context:property-placeholder location="classpath:com/liumiao/demo/spring/Person.properties" /> <bean id="thePerson" class="com.liumiao.demo.spring.Student" init-method="initMethod" destroy-method="destroyMethod" scope="prototype"> <property name="teachingService" ref="theService"></property> <property name="name" value="${person.name}" /> <property name="country" value="${person.country}" /> </bean> <bean id="theService" class="com.liumiao.demo.spring.SwimmingTeachingService"> </bean> </beans>
执行结果
TestDemo无需再修正,可以直接确认结果如下. 可以清楚地看到使用的是不同的实例,确实和singleton的方式有所不同。十一月 27, 2016 10:43:09 上午 org.springframework.context.support.ClassPathXmlApplicationContext prepareRefresh 信息: Refreshing org.springframework.context.support.ClassPathXmlApplicationContext@3eb07fd3: startup date [Sun Nov 27 10:43:09 CST 2016]; root of context hierarchy 十一月 27, 2016 10:43:09 上午 org.springframework.beans.factory.xml.XmlBeanDefinitionReader loadBeanDefinitions 信息: Loading XML bean definitions from class path resource [com/liumiao/demo/spring/spring-cfg.xml] 十一月 27, 2016 10:43:09 上午 org.springframework.context.support.PropertySourcesPlaceholderConfigurer loadProperties 信息: Loading properties file from class path resource [com/liumiao/demo/spring/Person.properties] Student Default construct is called... Student: set method: SetName:liumiao.cn Student: set method: SetCountry:ChinaPRC User customized init-method is called Hello, I am a student. I teach how to study... ChinaPRC liumiao.cn Student Default construct is called... Student: set method: SetName:liumiao.cn Student: set method: SetCountry:ChinaPRC User customized init-method is called person and personB point to the different object... person object addresscom.liumiao.demo.spring.Student@4d95d2a2 personB object addresscom.liumiao.demo.spring.Student@53f65459 十一月 27, 2016 10:43:09 上午 org.springframework.context.support.ClassPathXmlApplicationContext doClose 信息: Closing org.springframework.context.support.ClassPathXmlApplicationContext@3eb07fd3: startup date [Sun Nov 27 10:43:09 CST 2016]; root of context hierarchy
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