1、引言

　　Spring中，对象无需自己负责查找或创建与其关联的其他对象，而是由容器负责把需要相互协作的对象引用赋予各个对象。创建应用对象之间的协作关系的行为通常称为装配（Wiring），这也是依赖注入的本质。

2、声明Bean

　　配置Bean的方式主要有两种：基于XML文件的配置方式和基于Java注解的配置方式。传统的基于XML文件的配置方式在声明Bean时，Spring配置文件的根元素来源于Spring beans命名空间所定义的<beans>元素。除了beans命名空间外，Java自带了多种XML命名空间，通过这些命名空间可以配置Spring容器。

　　下图为一些常见的Spring命名空间：

简单声明Bean的实例：

Bean类：

 package com.springinaction.springidol;

public class Juggler implements Performer {

     private int beanBags = 3;

     public Juggler(){

     }

     public Juggler( int beanBags){

            this. beanBags = beanBags;

     }

     public void perform() throws PerformanceException {

           System. out.println( "抛掷 "+ beanBags + "个豆袋子" );

     }

 }

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"

     xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd" >

     <bean id ="duke" class= "com.springinaction.springidol.Juggler" >

            <constructor-arg value ="15" />

     </bean >

</beans>

3、Spring的常用装配Bean值的方法

<?xml version="1.0" encoding= "UTF-8"?>

  <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     http://www.springframework.org/schema/beans/spring-beans.xsd">

     <!--构造器注入值 -->

     <bean id ="duke" class= "com.springinaction.springidol.Juggler" >

            <constructor-arg value ="15" />

     </bean >

     <bean id ="sonnet29" class= "com.springinaction.springidol.Sonnet29" >

     </bean >

     <bean id ="poeticDuke" class= "com.springinaction.springidol.PoeticJuggler" >

            <constructor-arg  value ="15" />

            <!--构造器注入对象引用 -->

            <constructor-arg  ref ="sonnet29" />

     </bean >

     <!--通过工厂方法创建Bean,适合单例设计模式 -->

     <bean id ="theStage" class= "com.springinaction.springidol.Stage"

            factory-method= "getInstance">

     </bean >

     <!--初始化和销毁Bean -->

     <bean id ="auditorium" class= "com.springinaction.springidol.Auditorium"

            init-method= "turnOnLights" destroy-method="turnOffLights" >

     </bean >

     <!--注入属性值 -->

     <bean id ="kenny" class= "com.springinaction.springidol.Instrumentalist" >

            <!--注入简单值 -->

            <property name ="song" value="Jingle Bells" />

            <!--注入引用 -->

            <property name ="instrument" ref="pinao" />

            <!-- 内部Bean（inner bean） -->

            <!-- <property name="instrument"> <bean class="com.springinaction.springidol.Saxophone"></bean>

                </property> -->

     </bean >

     <!--装配集合 -->

     <bean id ="hank" class= "com.springinaction.springidol.OneManBand" >

            <property name ="instruments">

                 <list >

                      <ref bean ="pinao" />

                      <ref bean ="saxophon" />

                 </list >

            </property >

     </bean >

     <!--装配Map集合 -->

     <bean id ="hank2" class= "com.springinaction.springidol.OneManBand2" >

            <property name ="instruments">

                 <map >

                      <entry key ="PINAO" value-ref="pinao" />

                      <entry key ="SAXOPHON" value-ref="saxophon" />

                 </map >

            </property >

     </bean >

     <!--装配Properties集合 -->

     <bean id ="hank3" class= "com.springinaction.springidol.OneManBand3" >

            <property name ="instruments">

                 <props >

                      <prop key ="PINAO">TOOT TOOT TOOT</ prop>

                      <prop key ="SAXOPHON">PLINK PLINK PLINK</prop>

                 </props >

            </property >

     </bean >

     <!--装配空值 -->

     <bean id="example" class="com.springinaction.springidol.OneManBand2">

           <property name="someNonNullProperty">

                <null />

           </property>

     </bean>

     <bean id ="saxophon" class= "com.springinaction.springidol.Saxophone" ></bean >

     <bean id ="pinao" class= "com.springinaction.springidol.Pinao" ></bean >

</beans>

4、SPEL(Spring表达式语言)

　　Spring还可以使用表达式进行装配，Spring使用SPEL装配的实例如下所示：

<?xml version="1.0" encoding= "UTF-8"?>

  <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 http://www.springframework.org/schema/beans/spring-beans.xsd">

     <!-- 字面值 -->

     <bean id ="duke" class= "com.springinaction.springidol.Juggler" >

            <!-- 整形 -->

            <property name ="song" value="#{5}" />

            <!-- 混合表达 -->

            <property name ="song" value="The Value is #{5}" />

            <!--浮点数 -->

            <property name ="song" value="#{89.7}" />

            <!--科学计数法 -->

            <property name ="song" value="#{1e4}" />

            <!--单引号或双引号为字符串 -->

            <property name ="song" value="#{'string'}" />

            <property name ="song" value='#{"string"}' />

            <!--布尔值 -->

            <property name ="song" value="#{false}" />

     </bean >

     <!-- 引用Bean、Properties和方法 -->

     <bean id ="car1" class= "com.springinaction.springidol.Instrumentalist" >

            <!-- 使用SPEL表达式装配Bean值 -->

            <property name ="instrument" value="#{saxophone}" />

            <!-- 使用SPEL表达式装配属性值 -->

            <property name ="song" value="#{kenny.song}" />

            <!-- 使用SPEL表达式调用其他Bean的方法 -->

            <property name ="song" value= "#{songSelector.selectSong()?.toUpperCase()}" />

     </bean >

     <!-- 操作类,T()会调用类作用域的方法和常量 -->

     <bean id ="car1" class= "com.springinaction.springidol.Instrumentalist" >

            <!-- 使用SPEL表达式获取PI值 -->

            <property name ="multiolier" value= "#{T(java.lang.Math).PI}" />

            <!-- 使用SPEL表达式获取随机数 -->

            <property name ="song" value= "#{T(java.lang.Math).random()}" />

     </bean >

     <!-- SPEL进行数值计算 -->

     <bean id ="car1" class= "com.springinaction.springidol.Instrumentalist" >

            <!-- 使用SPEL进行常规计算 -->

            <property name ="adjustedAmount" value= "#{counter.total+42}" />

            <!-- 使用SPEL进行乘法运算 -->

            <property name ="adjustedAmount" value="#{2 * T(java.lang.Math).PI * circle.radius}" />

            <!-- 使用SPEL进行除法运算 -->

            <property name ="adjustedAmount" value= "#{counter.total / counter.count}" />

            <!-- 使用SPEL进行求余运算 -->

            <property name ="adjustedAmount" value= "#{counter.total % counter.count}}" />

            <!-- 不同于Java，SPEL还提供乘方运算 -->

            <property name ="adjustedAmount"

                 value= "#{2 * T(java.lang.Math).PI * circle.radius ^ 2}" />

            <!-- 使用SPEL还可以使用+号进行字符串的连接 -->

            <property name ="adjustedAmount"

                 value= "#{performer.firstName + '' + performer.lastName}" />

     </bean >

     <!-- SPEL进行比较 -->

     <bean id ="car2" class= "com.springinaction.springidol.Instrumentalist" >

            <!-- 判断条件是否成立，进行装配布尔值属性,并且Spring中使用le和ge替代<=和>=号 -->

            <property name ="equal" value="#{counter.total == 100}" />

     </bean >

     <!-- SPEL的逻辑表达式 and、or、not或！ -->

     <bean id ="car1" class= "com.springinaction.springidol.Instrumentalist2" >

            <property name ="largeCircle"

                 value= "#{shape.kind == 'circle' and shape.perimeter gt 1000}" />

            <property name ="outOfStock" value= "#{!product.avaliable}" />

     </bean >

     <!-- SPEL的条件表达式 -->

     <bean id ="car1" class= "com.springinaction.springidol.Instrumentalist2" >

            <property name ="song"

                 value= "#{kenny.song != null ? kenny.song : 'Greensleeves'}" />

            <!-- 三元运算符的简化形式 ,这被称为elvis运算符 -->

            <property name ="song" value="#{kenny.song ?: 'Greensleeves'}" />

     </bean >

     <!-- SPEL的正则表达式 -->

     <bean id ="car1" class= "com.springinaction.springidol.Instrumentalist2" >

            <property name ="validEmail"

                 value= "#{admin.email matches '[a-zA-Z0-9._%+-]+\\.com'}" />

     </bean >

</beans>

SPEL的重要功能，筛选集合实例：

 <?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:p= "http://www.springframework.org/schema/p"

     xmlns:util="http://www.springframework.org/schema/util"

     xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd

     http://www.springframework.org/schema/util http://www.springframework.org/schema/util/spring-util.xsd">

     <!-- 使用Spring设置列表 -->

     <util:list id ="cities">

            <bean class ="com.springinaction.springidol.spel.City" p:name= "Chicage1"

                 p:state= "1L" p:population ="111111111"></ bean>

            <bean class ="com.springinaction.springidol.spel.City" p:name= "Chicage2"

                 p:state= "2L" p:population ="211111111">

            </bean >

            <bean class ="com.springinaction.springidol.spel.City" p:name= "Chicage3"

                 p:state= "3L" p:population ="311111111">

            </bean >

            <bean class ="com.springinaction.springidol.spel.City" p:name= "Chicage4"

                 p:state= "4L" p:population ="411111111">

            </bean >

            <bean class ="com.springinaction.springidol.spel.City" p:name= "Chicage5"

                 p:state= "5L" p:population ="511111111">

            </bean >

            <bean class ="com.springinaction.springidol.spel.City" p:name= "Chicage6"

                 p:state= "6L" p:population ="611111111">

            </bean >

            <bean class ="com.springinaction.springidol.spel.City" p:name= "Chicage7"

                 p:state= "7L" p:population ="711111111">

            </bean >

            <bean class ="com.springinaction.springidol.spel.City" p:name= "Chicage8"

                 p:state= "8L" p:population ="811111111">

            </bean >

     </util:list >

     <!-- SPEL筛选集合 -->

     <bean id ="spelSelectSet" class= "com.springinaction.springidol.spel.ChooseCity" >

            <!-- 选择第三个城市 -->

            <!-- <property name="chooseCitySet" value="#{cities[2]}"></property> -->

            <!-- 随机选择城市 -->

            <property name ="chooseCitySet"

                 value= "#{cities[T(java.lang.Math).random() * cities.size()]}"></property>

            <!-- 系统环境 -->

            <property name ="systemEnviorment" value= "#{systemEnvironment['JAVA_HOME']}" ></property >

            <!-- 系统配置信息 -->

            <property name ="systemProperties" value= "#{systemProperties['path']}"></property >

            <!-- 查询集合成员.?[]运算符 -->

            <property name ="bigCities" value= "#{cities.?[population gt 400000000]}" ></property >

            <!-- 查询第一个符合条件.^[]运算符 -->

            <property name ="firstBigCity" value= "#{cities.^[population gt 400000000]}" ></property >

            <!-- 查询最后一个符合条件.$[]运算符 -->

            <property name ="lastBigCity" value= "#{cities.$[population gt 400000000]}" ></property >

            <!-- 集合投影,即将将每一个成员中选取特有的属性放入新集合中 ,运算符.![] -->

            <property name ="cityNames" value= "#{cities.?[population gt 400000000].![name + ',' +state]}"></ property>

     </bean >

</beans>

巴特西

Spring笔记2——Spring中Bean的装配

1、引言

2、声明Bean

简单声明Bean的实例：

SPEL的重要功能，筛选集合实例：

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