Spring学习笔记—装配Bean
在Spring中,对象无需自己负责查找或创建与其关联的其他对象。相反,容器负责把需要相互协作的对象引用赋予各个对象。创建应用对象之间协作关系的行为通常称为装配(wiring),这也是依赖注入的本质。
在XML文件中声明Bean时,Spring配置文件的根元素是来源于Spring beans命名空间所定义的<beans>元素。以下是一个典型的Spring XML配置文件:
<?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" xmlns:aop="http://www.springframework.org/schema/aop" xmlns:tx="http://www.springframework.org/schema/tx" xmlns:jee="http://www.springframework.org/schema/jee" xmlns:lang="http://www.springframework.org/schema/lang" xmlns:util="http://www.springframework.org/schema/util" xsi:schemaLocation=" http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-3.1.xsd http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx-3.1.xsd http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop-3.1.xsd http://www.springframework.org/schema/jee http://www.springframework.org/schema/jee/spring-jee-3.1.xsd http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-3.1.xsd http://www.springframework.org/schema/lang http://www.springframework.org/schema/lang/spring-lang-3.1.xsd http://www.springframework.org/schema/util http://www.springframework.org/schema/util/spring-util-3.1.xsd"> <!-- Bean declaration go here --> </beans></span>在 <beans>元素内,可以放置所有的Spring配置信息,包括<bean>元素的声明。
Spring核心框架自带的10个命名空间配置如下:
<bean id="zookeeperSources" class="com.dangdang.config.service.easyzk.support.spring.ZookeeperSourceFactoryProxy" > <constructor-arg name="appName" value="${server.name}" /> <constructor-arg name="configFactory" ref="configFactory" /> <constructor-arg name="nodes" value=""/> </bean></span>2) 通过工厂化方法创建Bean
<bean id="zookeeperSources" class="com.dangdang.config.service.ZookeeperSource" factory-method="create"/>
<bean id="zookeeperSources" class="com.dangdang.config.service.ZookeeperSource" scope="prototype"/></span>Spring的作用域选项:
<bean id="auditor" class="com.springinaction.springidol.Auditor" init-method="turnOnLights" destroy-method="turnOffLights" /></span>可以使用<beans>元素的default-init-method和default-destroy-method为应用上下文中所有的Bean设置共同的初始化和销毁方法。
<beans xmlns="http://www.springframework.org/schema/beans" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation=" http://www.springframework.org/schema/beans/spring-beans-3.1.xsd" default-init-method=" turnOnLights" default-destroy-method="turnOffLights"> </beans></span>
<bean id =“kenny" class="com.ouc.springinaction.test"> <property name ="song" value="Bells" /> </bean>
<bean id =“saxon" class="com.ouc.springinaction.saxontest"></bean> <bean id =“kenny" class="com.ouc.springinaction.test2"> <property name ="song" value="Bells" /> <property name ="saxonIns" ref="saxon" /> </bean>Spring提倡面向接口编程,面向接口编程与依赖注入协作实现了松散耦合。
<bean id =“saxon" class="com.ouc.springinaction.saxontest"></bean> <bean id =“kenny" class="com.ouc.springinaction.test2"> <property name ="song" value="Bells" /> <property name ="saxonIns"> <bean class="com.ouc.springinaction.saxontest"> /property> </bean>内部Bean是通过直接声明一个<bean>元素作为 <property>元素的子节点而定义的。
<bean id =“kenny" class="com.ouc.springinaction.test3"> p:song = "Bells" p:saxonIns-ref = "saxon" /> </bean>使用p:作为<bean>元素所有属性的前缀来装配Bean的属性。-ref后缀作为一个标识来告知Spring应该装配一个引用。
<bean id =“hank" class="com.ouc.springinaction.test4"> <property name ="ins"> <set> <ref bean = "guitar" /> <ref bean = "cymbal" /> <ref bean = "harmonica" /> <ref bean = "harmonica" /> </set> </property> </bean>
<bean id =“hank" class="com.ouc.springinaction.test4"> <property name ="ins"> <list> <ref bean = "guitar" /> <ref bean = "cymbal" /> <ref bean = "harmonica" /> </list> </property> </bean>装配Map集合
<bean id =“hank" class="com.ouc.springinaction.test4"> <property name ="ins"> <map> <entry key="GUITAR" value-ref = "guitar" /> <entry key="GUITAR1" value-ref = "guitar1" /> <entry key="GUITAR2" value-ref = "guitar2" /> </map> </property> </bean>
<bean id =“hank" class="com.ouc.springinaction.test4"> <property name ="ins"> <props> <prop key="GUITAR"> STRUM </prop> <prop key="CYMBAL"> CRASH </prop> </props> </property> </bean>● <property> 元素用于把值或Bean引用注入到Bean的属性中。
<property name ="nullIns"><null/></property>
<property name="cappacity" value="#{1e4}" />
<property name="ins" value="#{saxno.song}" /> <property name="ins" value="#{saxno.song()?.toUpperCase()}" />使用?.运算符代替点(.)来访问toUpperCase()方法。
<property name="mathplier" value="#{T(java.lang.Math).PI}" /> <property name="randomNum" value="#{T(java.lang.Math).random()}" />使用SpEL进行数值运算
<property name="area" value="#{T(java.lang.Math).PI * circle.radius ^ 2}" />比较值
<property name="hasCap" value="#{count.total le 10000}" />逻辑表达式
<property name="outStock" value="#{!pro.available}" /> <property name="outStock" value="#{not pro.available}" />条件表达式
<property name="song" value="#{keny.song != null ? keny.song : 'Green'}" /> <property name="song" value="#{keny.song ?: 'Green'}" />SpEL正则表达式
<property name="validEmail" value="#{admin.email matches '[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\\.com'}" />使用<util:list>元素在Spring里配置一个包含City对象的List集合。
<util:list id ="cities"> <bean class="com.habuma.spel.city" p:name="Chicago" p:state="IL" p:population="2556321" /> p:name="Chicago1" p:state="IL1" p:population="2556312" /> p:name="Chicago2" p:state="IL2" p:population="2556311" /> </util:list>访问集合成员
<property name="choseCity" value="#{cities[2]}" /> <property name="choseCity" value="#{cities['Chicago']}" />两种特殊的选择属性的方式:systemEnvironment和systemProperties。
<property name="homePath" value="#{systemEnvironment['HOME']}" />
<property name="homePath" value="#{systemProperties['app.home']}" />查询集合成员
<property name="bigCities" value="#{cities.?[population gt 10000]}" />使用".^[]"和".$[]",从集合中查询第一匹配项和最后一个匹配项。
<property name="cityNames" value="#{cities.![name]}" />