(spring-第4回【IoC基础篇】)spring基于注解的配置
基于XML的bean属性配置:bean的定义信息与bean的实现类是分离的。
基于注解的配置:bean的定义信息是通过在bean实现类上标注注解实现。
也就是说,加了注解,相当于在XML中配置了,一样一样的。
一、举个栗子:
1 package com.mesopotamia.annotation; 2 3 import org.springframework.stereotype.Component; 4 5 @Component 6 public class Car { 7 private String name; 8 private String color; 9 private double price; 10 public Car(){ 11 name="保时捷"; 12 color="黄色"; 13 } 14 public String getName() { 15 return name; 16 } 17 public void setName(String name) { 18 this.name = name; 19 } 20 public String getColor() { 21 return color; 22 } 23 public void setColor(String color) { 24 this.color = color; 25 } 26 public double getPrice() { 27 return price; 28 } 29 public void setPrice(double price) { 30 this.price = price; 31 } 32 33 public String toString(){ 34 return "名字:"+name+" 颜色:"+color+" 价格:"+price; 35 } 36 }
第5行标注Component:spring看到这个属性标志,会自动将Car变成容器管理类,等同于在XML中这样配置:
1 <bean id="car" class="com.mesopotamia.annotation.Car"></bean>
二、spring启动之前的配置?
1 <?xml version="1.0" encoding="UTF-8" ?> 2 <beans xmlns="http://www.springframework.org/schema/beans" 3 xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 4 xmlns:context="http://www.springframework.org/schema/context" 5 xsi:schemaLocation="http://www.springframework.org/schema/beans 6 http://www.springframework.org/schema/beans/spring-beans-3.0.xsd 7 http://www.springframework.org/schema/context 8 http://www.springframework.org/schema/context/spring-context-3.0.xsd" 9 > 10 <context:component-scan base-package="com.mesopotamia.annotation"/> 11 </beans>
如上,
使用空间:context,
使用context的规则:component-scan.
第10行的意义:扫描这个包中的所有类,并从注解信息中获取bean的基本信息(没加注解的不扫描也不实例化)。
三、如何启动?
按正常方式启动即可加载(自己复习spring容器的加载),例如:
1 package com.mesopotamia.annotation; 2 3 import org.springframework.context.ApplicationContext; 4 import org.springframework.context.support.ClassPathXmlApplicationContext; 5 6 public class Main { 7 8 public static void main(String args[]){ 9 ApplicationContext ctx = new ClassPathXmlApplicationContext("com/mesopotamia/annotation/beans.xml"); 10 Car car= ctx.getBean(Car.class); 11 System.out.println(car.toString()); 12 } 13 14 }
第10行就已经实例化Car了,并且实例化之前先跑了Car的构造函数给car的属性附了值(因为我给构造函数里专门写了赋值语句,没写的话,属性是没有赋值的,除非见了鬼)。
下面是打印信息,从下面第4行结果可以看到已经附了值。
1 2015-11-13 23:44:18,414 INFO [main] (AbstractApplicationContext.java:456) - Refreshing org.springframework.context.support.ClassPathXmlApplicationContext@e80a59: startup date [Fri Nov 13 23:44:18 CST 2015]; root of context hierarchy 2 2015-11-13 23:44:18,480 INFO [main] (XmlBeanDefinitionReader.java:315) - Loading XML bean definitions from class path resource [com/mesopotamia/annotation/beans.xml] 3 2015-11-13 23:44:18,728 INFO [main] (DefaultListableBeanFactory.java:555) - Pre-instantiating singletons in org.springframework.beans.factory.support.DefaultListableBeanFactory@121ab80: defining beans [car,org.springframework.context.annotation.internalConfigurationAnnotationProcessor,org.springframework.context.annotation.internalAutowiredAnnotationProcessor,org.springframework.context.annotation.internalRequiredAnnotationProcessor,org.springframework.context.annotation.internalCommonAnnotationProcessor,org.springframework.context.annotation.internalPersistenceAnnotationProcessor]; root of factory hierarchy 4 名字:保时捷 颜色:黄色 价格:0.0
四、context:component-scan的配置直接选了相应包里的全部class,有没有更多的过滤方式?
有。context:component-scan标签下面可以再加子标签,如:
1 <context:component-scan base-package="com.baobaotao"> 2 <context:include-filter type="aspectj" expression="com.baobaotao.anno.*Plugin+"/> 3 <context:exclude-filter type="regex" expression="cn\.outofmemory\.spring\.[^.]+(Dao|Service)"/>
4</context:component-scan>
include-filter表示:包含哪些。type是类型,expression是表达式过滤。
exclude-filter表示:除去哪些。type是类型,expression是表达式过滤。
第二行表示:com.baobaotao.anno包下面所有以Plugin结尾的class。
第三行表示:除去所有以Dao或者Service结束的类。具体规则这里先不作讨论,你要觉得你行,那你自己先啃啃里面的肉(先去复习一下正则表达式)
其他过滤表达式举例:
五、除了Component外,其他的注解都有什么?
1、@Component 一般的bean类上面配置。
2、@Controller 对应表现层的Bean,也就是action。
3、@ Service 对应业务层bean。
4、@ Repository 对应持久层Bean。
上面的4种起到相同的效果,都是注入bean,注入bean的四大金刚,张龙赵虎王朝马汉,辅佐包黑炭。
5、@Autowired 成员变量或方法入参处标注,按类型匹配自动注入。
6、@Qualifier 按名称匹配方式注入。
7、@PostConstruct指定初始化方法。(相当于XML配置中的init-method)
8、@PreDestroy指定销毁方法。(相当于XML配置中的destroy-method)
9、@Scope 指定bean是prototype还是singleton。
六、上面这几个注解给个具体例子说明下?
不想往下看的可以去陪女朋友了,因为重点已经讲完了。下面是一个简单登录界面的栗子,为了突出重点,关于spring web方面的机制暂时不讲,只讲有关注解的部分,如果你还没看过spring web应用部分也无妨,下面的例子只涉及注解注入部分:
XML配置文件如下:
1 <?xml version="1.0" encoding="UTF-8" ?> 2 <beans xmlns="http://www.springframework.org/schema/beans" 3 xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 4 xmlns:p="http://www.springframework.org/schema/p" 5 xmlns:context="http://www.springframework.org/schema/context" 6 xmlns:aop="http://www.springframework.org/schema/aop" 7 xmlns:tx="http://www.springframework.org/schema/tx" 8 xsi:schemaLocation="http://www.springframework.org/schema/beans 9 http://www.springframework.org/schema/beans/spring-beans-3.0.xsd 10 http://www.springframework.org/schema/context 11 http://www.springframework.org/schema/context/spring-context-3.0.xsd 12 http://www.springframework.org/schema/tx 13 http://www.springframework.org/schema/tx/spring-tx-3.0.xsd 14 http://www.springframework.org/schema/aop 15 http://www.springframework.org/schema/aop/spring-aop-3.0.xsd"> 16 17 <!-- 扫描类包,将标注Spring注解的类自动转化Bean,同时完成Bean的注入 --> 18 <context:component-scan base-package="com.baobaotao.dao"/> 19 <context:component-scan base-package="com.baobaotao.service"/> 20 <context:component-scan base-package="com.baobaotao.domain"/> 21 22 <!-- 配置数据源 --> 23 <bean id="dataSource" class="org.apache.commons.dbcp.BasicDataSource" 24 destroy-method="close" 25 p:driverClassName="com.mysql.jdbc.Driver" 26 p:url="jdbc:mysql://localhost:3306/sampledb" 27 p:username="root" 28 p:password="2009118293zjl" /> 29 30 <!-- 配置Jdbc模板 --> 31 <bean id="jdbcTemplate" class="org.springframework.jdbc.core.JdbcTemplate" 32 p:dataSource-ref="dataSource" /> 33 34 <!-- 配置事务管理器 --> 35 <bean id="transactionManager" 36 class="org.springframework.jdbc.datasource.DataSourceTransactionManager" 37 p:dataSource-ref="dataSource" /> 38 39 <!-- 通过AOP配置提供事务增强,让service包下所有Bean的所有方法拥有事务 --> 40 <aop:config proxy-target-class="true"> 41 <aop:pointcut id="serviceMethod" 42 expression=" execution(* com.baobaotao.service..*(..))" /> 43 <aop:advisor pointcut-ref="serviceMethod" advice-ref="txAdvice" /> 44 </aop:config> 45 <tx:advice id="txAdvice" transaction-manager="transactionManager"> 46 <tx:attributes> 47 <tx:method name="*" /> 48 </tx:attributes> 49 </tx:advice> 50 </beans>
重点第18到20行:spring只扫描配置路径下所有带注解的地方来注入相关数据。其他行先不看,你想看我也不拦你。
WEB应用后台java分三层:control、service、dao层,简单讲一下,直接与jsp交互的就是control层,直接操作数据库的是dao层(持久层,数据库里的数据都是持久性的嘛),service层负责把dao层数据拿到,经过处理,返回给control层。control层拿到数据再交给jsp前台。(dao就是程序员,service就是老板,control就是客户,程序员做东西,客户使用,而老板是桥梁)
下面是control层:
1 package com.baobaotao.web; 2 3 import java.util.Date; 4 5 import javax.annotation.PostConstruct; 6 import javax.annotation.PreDestroy; 7 import javax.servlet.http.HttpServletRequest; 8 9 10 import org.apache.commons.logging.Log; 11 import org.apache.commons.logging.LogFactory; 12 import org.springframework.beans.factory.annotation.Autowired; 13 import org.springframework.stereotype.Controller; 14 import org.springframework.web.bind.annotation.RequestMapping; 15 import org.springframework.web.servlet.ModelAndView; 16 17 import com.baobaotao.domain.User; 18 import com.baobaotao.service.UserService; 19 20 @Controller 21 public class LoginController{ 22 Log log=LogFactory.getLog(LoginController.class); 23 24 @Autowired(required=false) 25 private UserService userService; 26 27 @RequestMapping(value = "/loginCheck.do") 28 public ModelAndView loginCheck(HttpServletRequest request,LoginCommand loginCommand){ 29 boolean isValidUser = userService.hasMatchUser(loginCommand.getUserName(),loginCommand.getPassword()); 30 if (!isValidUser) { 31 return new ModelAndView("login", "error", "用户名或密码错误。"); 32 } else { 33 User user = userService.findUserByUserName(loginCommand 34 .getUserName()); 35 user.setLastIp(request.getLocalAddr()); 36 user.setLastVisit(new Date()); 37 userService.loginSuccess(user); 38 request.getSession().setAttribute("user", user); 39 40 return new ModelAndView("main"); 41 } 42 } 43 44 @PostConstruct 45 public void init(){ 46 log.info("本应用程序正式拉开帷幕。。。"); 47 } 48 49 @PreDestroy 50 public void destroy(){ 51 log.info("本应用程序正式落幕,吓吓侬。。。"); 52 } 53 }
这里用到了几个注解,
spring看到@Controller会如同看到@Component一样,转换成spring容器管理的bean。
spring看到@Autowired(required=false)会自动注入(实例化)下面的userService。(直接用就行,就不用你来new一个对象啦)。
spring看到@PostConstruct就会在实例化本Bean后接着执行这个方法;
spring看到@PreDestroy就会在销毁之前执行下面的方法;
你的眼神告诉我你不相信我。好的,咱们看日志:
tomcat启动的时候spring容器会自动加载,下面是tomcat启动的日志:
1 。。。。。。 2 3 2015-11-15 21:24:31,673 DEBUG [main] (DefaultSingletonBeanRegistry.java:214) - Creating shared instance of singleton bean 'userDao' 4 2015-11-15 21:24:31,674 DEBUG [main] (AbstractAutowireCapableBeanFactory.java:430) - Creating instance of bean 'userDao' 5 2015-11-15 21:24:31,674 DEBUG [main] (AbstractBeanFactory.java:242) - Returning cached instance of singleton bean 'org.springframework.aop.support.DefaultBeanFactoryPointcutAdvisor#0' 6 7 。。。。。。 8 9 2015-11-15 21:24:31,676 DEBUG [main] (InjectionMetadata.java:82) - Processing injected method of bean 'userDao': AutowiredFieldElement for private org.springframework.jdbc.core.JdbcTemplate com.baobaotao.dao.UserDao.jdbcTemplate 10 2015-11-15 21:24:31,677 DEBUG [main] (AbstractBeanFactory.java:242) - Returning cached instance of singleton bean 'jdbcTemplate' 11 2015-11-15 21:24:31,677 DEBUG [main] (AutowiredAnnotationBeanPostProcessor.java:420) - Autowiring by type from bean name 'userDao' to bean named 'jdbcTemplate' 12 13 。。。。。。 14 15 2015-11-15 21:24:31,678 DEBUG [main] (AbstractAutowireCapableBeanFactory.java:458) - Finished creating instance of bean 'userDao' 16 17 18 。。。。。。 19 20 2015-11-15 21:24:31,679 DEBUG [main] (DefaultSingletonBeanRegistry.java:214) - Creating shared instance of singleton bean 'userService' 21 2015-11-15 21:24:31,679 DEBUG [main] (AbstractAutowireCapableBeanFactory.java:430) - Creating instance of bean 'userService' 22 2015-11-15 21:24:31,679 DEBUG [main] (AbstractBeanFactory.java:242) - Returning cached instance of singleton bean 'org.springframework.aop.support.DefaultBeanFactoryPointcutAdvisor#0' 23 2015-11-15 21:24:31,680 INFO [main] (UserService.java:18) - 实例化了UserService... 24 25 。。。。。。 26 27 2015-11-15 21:24:31,683 DEBUG [main] (InjectionMetadata.java:82) - Processing injected method of bean 'userService': AutowiredFieldElement for private com.baobaotao.dao.UserDao com.baobaotao.service.UserService.userDao 28 2015-11-15 21:24:31,685 DEBUG [main] (AbstractBeanFactory.java:242) - Returning cached instance of singleton bean 'userDao' 29 2015-11-15 21:24:31,685 DEBUG [main] (AutowiredAnnotationBeanPostProcessor.java:420) - Autowiring by type from bean name 'userService' to bean named 'userDao' 30 2015-11-15 21:24:31,686 DEBUG [main] (InjectionMetadata.java:82) - Processing injected method of bean 'userService': AutowiredFieldElement for private com.baobaotao.dao.LoginLogDao com.baobaotao.service.UserService.loginLogDao 31 2015-11-15 21:24:31,686 DEBUG [main] (AbstractBeanFactory.java:242) - Returning cached instance of singleton bean 'loginLogDao' 32 2015-11-15 21:24:31,687 DEBUG [main] (AutowiredAnnotationBeanPostProcessor.java:420) - Autowiring by type from bean name 'userService' to bean named 'loginLogDao' 33 34 。。。。。。 35 36 2015-11-15 21:24:32,093 INFO [main] (UserService.java:18) - 实例化了UserService... 37 2015-11-15 21:24:32,094 DEBUG [main] (AbstractAutowireCapableBeanFactory.java:458) - Finished creating instance of bean 'userService' 38 2015-11-15 21:24:32,094 DEBUG [main] (DefaultSingletonBeanRegistry.java:214) - Creating shared instance of singleton bean 'loginLog' 39 40 。。。。。。 41 42 015-11-15 21:24:32,252 INFO [main] (DefaultListableBeanFactory.java:555) - Pre-instantiating singletons in org.springframework.beans.factory.support.DefaultListableBeanFactory@c272bc: defining beans [loginController,org.springframework.context.annotation.internalConfigurationAnnotationProcessor,org.springframework.context.annotation.internalAutowiredAnnotationProcessor,org.springframework.context.annotation.internalRequiredAnnotationProcessor,org.springframework.context.annotation.internalCommonAnnotationProcessor,org.springframework.web.servlet.view.InternalResourceViewResolver#0]; parent: org.springframework.beans.factory.support.DefaultListableBeanFactory@691dee 43 2015-11-15 21:24:32,252 DEBUG [main] (DefaultSingletonBeanRegistry.java:214) - Creating shared instance of singleton bean 'loginController' 44 2015-11-15 21:24:32,254 DEBUG [main] (AbstractAutowireCapableBeanFactory.java:430) - Creating instance of bean 'loginController' 45 2015-11-15 21:24:32,255 INFO [main] (LoginController.java:25) - 实例化了LoginController... 46 2015-11-15 21:24:32,264 DEBUG [main] (InitDestroyAnnotationBeanPostProcessor.java:200) - Found init method on class [com.baobaotao.web.LoginController]: public void com.baobaotao.web.LoginController.init() 47 2015-11-15 21:24:32,265 DEBUG [main] (InitDestroyAnnotationBeanPostProcessor.java:208) - Found destroy method on class [com.baobaotao.web.LoginController]: public void com.baobaotao.web.LoginController.destroy() 48 2015-11-15 21:24:32,265 DEBUG [main] (InitDestroyAnnotationBeanPostProcessor.java:251) - Found init method on class [com.baobaotao.web.LoginController]: org.springframework.beans.factory.annotation.InitDestroyAnnotationBeanPostProcessor$LifecycleElement@316510 49 2015-11-15 21:24:32,265 DEBUG [main] (InitDestroyAnnotationBeanPostProcessor.java:259) - Found destroy method on class [com.baobaotao.web.LoginController]: org.springframework.beans.factory.annotation.InitDestroyAnnotationBeanPostProcessor$LifecycleElement@5cd39ffa 50 2015-11-15 21:24:32,266 DEBUG [main] (InjectionMetadata.java:59) - Found injected element on class [com.baobaotao.web.LoginController]: AutowiredFieldElement for private com.baobaotao.service.UserService com.baobaotao.web.LoginController.userService 51 2015-11-15 21:24:32,267 DEBUG [main] (AbstractAutowireCapableBeanFactory.java:504) - Eagerly caching bean 'loginController' to allow for resolving potential circular references 52 2015-11-15 21:24:32,268 DEBUG [main] (InjectionMetadata.java:82) - Processing injected method of bean 'loginController': AutowiredFieldElement for private com.baobaotao.service.UserService com.baobaotao.web.LoginController.userService 53 2015-11-15 21:24:32,269 DEBUG [main] (AbstractBeanFactory.java:242) - Returning cached instance of singleton bean 'userService' 54 2015-11-15 21:24:32,270 DEBUG [main] (AutowiredAnnotationBeanPostProcessor.java:420) - Autowiring by type from bean name 'loginController' to bean named 'userService' 55 2015-11-15 21:24:32,271 DEBUG [main] (InitDestroyAnnotationBeanPostProcessor.java:291) - Invoking init method on bean 'loginController': public void com.baobaotao.web.LoginController.init() 56 2015-11-15 21:24:32,271 INFO [main] (LoginController.java:50) - 本应用程序正式拉开帷幕。。。 57 2015-11-15 21:24:32,271 DEBUG [main] (AbstractAutowireCapableBeanFactory.java:458) - Finished creating instance of bean 'loginController' 58 59 。。。。。。
第44、45行是实例化LoginController,
第46/47行是根据@PostContruct和@PreDestroy发现了我们定义的初始化和销毁方法。
第53行,spring直接给了我们一个userService对象(因为它看到了@Autowired,required=false是说如果找不到对应的bean不报异常)。
第56行,spring看到@PostContruct执行了初始化方法。
当我把tomcat停掉,spring容器就会销毁,那么是不是要执行@PreDestroy下面的销毁方法?当然,你要相信科学,看停掉tomcat的日志:
。。。。。 5 2015-11-15 21:53:15,763 DEBUG [main] (InitDestroyAnnotationBeanPostProcessor.java:303) - Invoking destroy method on bean 'loginController': public void com.baobaotao.web.LoginController.destroy() 6 2015-11-15 21:53:15,763 INFO [main] (LoginController.java:55) - 本应用程序正式落幕,吓吓侬。。。 7 2015-11-15 21:53:15 org.apache.catalina.core.ApplicationContext log 8 信息: Closing Spring root WebApplicationContext 9 2015-11-15 21:53:15,764 INFO [main] (AbstractApplicationContext.java:1002) - Closing Root WebApplicationContext: startup date [Sun Nov 15 21:24:29 CST 2015]; root of context hierarchy
第六行果然执行了销毁方法。
请解释前面那个日志里第53行的Returning cached instance of singleton bean 'userService'。
是这样的,先看UserService的部分代码:
1 @Service 2 public class UserService { 3 private static Log log=LogFactory.getLog(UserService.class); 4 public UserService(){ 5 log.info("实例化了UserService..."); 6 }
我在这个类中注释了@Service,spring在启动的时候跟@Component、@Controller、@Repository一样,会自动把bean信息注入容器中(即把bean在spring容器中实例化),也就是说,当spring看到@Service时,会自动返回一个提前实例化好的UserService,而只要UserService上面不显式标注:@Scope("prototype"),那么默认UserService就是单例模式的。单例模式下,spring会把bean放到IoC容器的缓存池中,而把bean的引用返回给调用者。这就是Returning cached instance of singleton bean 'userService'这句话的意义。
好的,我把UserService的注解改成下面的方式:
1 @Service 2 @Scope("prototype") 3 public class UserService { 4 private static Log log=LogFactory.getLog(UserService.class); 5 public UserService(){ 6 log.info("实例化了UserService..."); 7 } 8
那么启动tomcat打印日志如下:
1 2015-11-15 22:11:09,723 DEBUG [main] (Cglib2AopProxy.java:755) - Method is declared on Advised interface: public abstract int org.springframework.aop.framework.Advised.indexOf(org.aopalliance.aop.Advice) 2 2015-11-15 22:11:09,724 DEBUG [main] (Cglib2AopProxy.java:755) - Method is declared on Advised interface: public abstract int org.springframework.aop.framework.Advised.indexOf(org.springframework.aop.Advisor) 3 2015-11-15 22:11:09,724 DEBUG [main] (Cglib2AopProxy.java:755) - Method is declared on Advised interface: public abstract java.lang.Class org.springframework.aop.TargetClassAware.getTargetClass() 4 2015-11-15 22:11:09,760 INFO [main] (UserService.java:20) - 实例化了UserService... 5 2015-11-15 22:11:09,760 DEBUG [main] (AbstractAutowireCapableBeanFactory.java:458) - Finished creating instance of bean 'userService' 6 2015-11-15 22:11:09,761 DEBUG [main] (AutowiredAnnotationBeanPostProcessor.java:420) - Autowiring by type from bean name 'loginController' to bean named 'userService' 7 2015-11-15 22:11:09,761 DEBUG [main] (InitDestroyAnnotationBeanPostProcessor.java:291) - Invoking init method on bean 'loginController': public void com.baobaotao.web.LoginController.init() 8 2015-11-15 22:11:09,761 INFO [main] (LoginController.java:50) - 本应用程序正式拉开帷幕。。。 9 2015-11-15 22:11:09,761 DEBUG [main] (AbstractAutowireCapableBeanFactory.java:458) - Finished creating instance of bean 'loginController' 10 2015-11-15 22:11:09,761 DEBUG [main] (AbstractBeanFactory.java:242) - Returning cached instance of singleton bean 'org.springframework.context.annotati
你会看到,在拉开帷幕之前,又实例化了一次UserService,这就是prototype的作用。
再看:
1 @Controller 2 public class LoginController{ 3 Log log=LogFactory.getLog(LoginController.class); 4 5 public LoginController(){ 6 log.info("实例化了LoginController..."); 7 } 8 9 @Autowired(required=false) 10 @Qualifier("service") 11 private UserService userService; 12
第10行,我在userService上面加了 @Qualifier("service")的注释,这个表示,我引用的是名字为service的bean的实例,那么你要给UserService起个名字叫service:
1 @Service("service") 2 @Scope("prototype") 3 public class UserService { 4 private static Log log=LogFactory.getLog(UserService.class); 5 public UserService(){ 6 log.info("实例化了UserService..."); 7 } 8
像第一行那样。(Component、Controller、Repository也是那样命名,如果是基于XML的注入如何命名?自己复习去。)
不加的话,系统找不到对应的bean,就会报错。
spring容器的三座大山:XML配置文件(或者注解配置、bean配置等),spring容器,bean类。不管是基于XML还是基于注解,无非就是为了把bean信息注入到spring容器中,南拳和北腿,各有千秋。下面是二者的对比:
本节内容就讲到这里。
吾生也有涯,而知也无涯。
——《庄子》