标签：字符串 utf-8 actor 构造函数 context 表示 str rar spring
注入参数详解：null值和级联属性
可以使用专用的<null/>元素标签为Bean的字符串或其他对象类型的属性注入null值。
和Struts，Hiberante等框架一样，Spring支持级联属性的配置。
可以如下设置null值
<?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"> <!-- 配置bean class:bean的全类名，通过反射的方式在IOC容器中创建bean，所以要求Bean中必须有无参的构造函数 id:表示容器的bean，id唯一 --> <bean id="hello" class="logan.spring.study.HelloWorld"> </bean> <bean id="hello2" class="logan.spring.study.HelloWorld"> </bean> <!-- 通过构造方法来配置Bean的属性 --> <bean id="car" class="logan.spring.study.Car"> <constructor-arg value="Audi" index="0"></constructor-arg> <constructor-arg value="Shanghai" index="1"></constructor-arg> <constructor-arg value="3000000" index="2" type="double"></constructor-arg> </bean> <bean id="car2" class="logan.spring.study.Car"> <constructor-arg value="Baoma" type="java.lang.String"></constructor-arg> <constructor-arg type="java.lang.String"> <value><![CDATA[<Shanghai>]]></value> </constructor-arg> <constructor-arg type="int"> <value>250</value> </constructor-arg> </bean> <bean id="person" class="logan.spring.study.Person"> <property name="name" value="Tom"></property> <property name="age" value="24"></property> <property name="car"> <bean class="logan.spring.study.Car"> <constructor-arg value="Ford"></constructor-arg> <constructor-arg value="Changan"></constructor-arg> <constructor-arg value="20000000" type="double"></constructor-arg> </bean> </property> </bean> <bean id="person2" class="logan.spring.study.Person"> <constructor-arg value="Jerry"></constructor-arg> <constructor-arg value="25"></constructor-arg> <!-- <constructor-arg ref="car"></constructor-arg> --> <constructor-arg><null/></constructor-arg> </bean> </beans>
输出结果
五月 19, 2017 8:54:47 下午 org.springframework.context.support.ClassPathXmlApplicationContext prepareRefresh 信息: Refreshing org.springframework.context.support.ClassPathXmlApplicationContext@3eb07fd3: startup date [Fri May 19 20:54:47 CST 2017]; root of context hierarchy 五月 19, 2017 8:54:47 下午 org.springframework.beans.factory.xml.XmlBeanDefinitionReader loadBeanDefinitions 信息: Loading XML bean definitions from class path resource [applicationContext.xml] HelloWorld‘s Constructor... HelloWorld‘s Constructor... Car [brand=Audi, corp=Shanghai, price=3000000.0, maxspeed=0] Car [brand=Baoma, corp=<Shanghai>, price=0.0, maxspeed=250] Person [name=Jerry, age=25, car=null]
看下面级联属性的赋值
<?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"> <!-- 配置bean class:bean的全类名，通过反射的方式在IOC容器中创建bean，所以要求Bean中必须有无参的构造函数 id:表示容器的bean，id唯一 --> <bean id="hello" class="logan.spring.study.HelloWorld"> </bean> <bean id="hello2" class="logan.spring.study.HelloWorld"> </bean> <!-- 通过构造方法来配置Bean的属性 --> <bean id="car" class="logan.spring.study.Car"> <constructor-arg value="Audi" index="0"></constructor-arg> <constructor-arg value="Shanghai" index="1"></constructor-arg> <constructor-arg value="3000000" index="2" type="double"></constructor-arg> </bean> <bean id="car2" class="logan.spring.study.Car"> <constructor-arg value="Baoma" type="java.lang.String"></constructor-arg> <constructor-arg type="java.lang.String"> <value><![CDATA[<Shanghai>]]></value> </constructor-arg> <constructor-arg type="int"> <value>250</value> </constructor-arg> </bean> <bean id="person" class="logan.spring.study.Person"> <property name="name" value="Tom"></property> <property name="age" value="24"></property> <property name="car"> <bean class="logan.spring.study.Car"> <constructor-arg value="Ford"></constructor-arg> <constructor-arg value="Changan"></constructor-arg> <constructor-arg value="20000000" type="double"></constructor-arg> </bean> </property> </bean> <bean id="person2" class="logan.spring.study.Person"> <constructor-arg value="Jerry"></constructor-arg> <constructor-arg value="25"></constructor-arg> <!-- <constructor-arg ref="car"></constructor-arg> <constructor-arg><null/></constructor-arg> --> <constructor-arg ref="car"></constructor-arg> <property name="car.maxspeed" value="250"></property> </bean> </beans>
下面是输出结果，注意：属性需要先初始化以后才可以为级联属性赋值，否则会有异常，和Struts2不同。
五月 19, 2017 9:17:51 下午 org.springframework.context.support.ClassPathXmlApplicationContext prepareRefresh 信息: Refreshing org.springframework.context.support.ClassPathXmlApplicationContext@3eb07fd3: startup date [Fri May 19 21:17:51 CST 2017]; root of context hierarchy 五月 19, 2017 9:17:51 下午 org.springframework.beans.factory.xml.XmlBeanDefinitionReader loadBeanDefinitions 信息: Loading XML bean definitions from class path resource [applicationContext.xml] HelloWorld‘s Constructor... HelloWorld‘s Constructor... Car [brand=Audi, corp=Shanghai, price=3000000.0, maxspeed=250] Car [brand=Baoma, corp=<Shanghai>, price=0.0, maxspeed=250] Person [name=Jerry, age=25, car=Car [brand=Audi, corp=Shanghai, price=3000000.0, maxspeed=250]]
标签：字符串 utf-8 actor 构造函数 context 表示 str rar spring
原文地址：http://www.cnblogs.com/LoganChen/p/6880326.html
