SpringIOC容器——参数值注入

基本在注入：

<bean id="myDataSource" class="org.apache.commons.dbcp.BasicDataSource">
		<property name="driverClassName" value="oracle.jdbc.OracleDriver" />
		<property name="url" value="jdbc:oracle:thin:@localhost:1521:XE" />
		<property name="username" value="jsd1403" />
		<property name="password" value="root" />
	</bean>

 或者下面的写法：

<!-- 视图解析器 -->
	<bean id="viewResolver"
		class="org.springframework.web.servlet.view.InternalResourceViewResolver">
		<property name="prefix">
			<value>/WEB-INF/jsp/</value>
		</property>
		<property name="suffix">
			<value>.jsp</value>
		</property>
	</bean>

Bean对象注入:

<bean id="empservice" class="spring.EmpService">
		<!-- 构造器注入：
			<constructor-arg index="0" ref="empdao"></constructor-arg>
		-->
		<!--属性注入：
			<property name="empDao" ref="empdao"></property>
		-->
		<constructor-arg index="0">
			<bean class="spring.EmpDao"></bean>
		</constructor-arg>
	</bean>
	<bean id="empdao" class="spring.EmpDao"></bean>

 EmpService.java编写

public class EmpService {
	private EmpDao empDao;
	
	public EmpService() {
		System.out.println("------new( )-------");
	}

	public EmpService(EmpDao empDao) {
		System.out.println("------new( param1 )-------");
		this.empDao = empDao;
	}
       //getter and setter
 }

List集合注入

<bean id="msg" class="com.lydia.Message">
		<property name="friends">
			<list>
				<value>jack</value>
				<value>kevin</value>
			</list>
		</property>
	</bean>

Set集合注入：

<bean id="msg" class="com.lydia.Message">
		<property name="friends">
			<set>
				<value>jack</value>
				<value>kevin</value>
			</set>
		</property>
	</bean>

Map注入:

<bean id="msg" class="com.lydia.Message">
		<property name="friends">
			<map>
				<entry key="1001" value="kevin"></entry>
				<entry key="1002" value="Charles"></entry>
			</map>
		</property>
	</bean>

Properties注入：

<bean id="msg" class="com.lydia.Message">
<property name="dbProp">
			<props>
				<prop key="username">root</prop>
				<prop key="password">root</prop>
			</props>
		</property>
	</bean>

也可以引入Spring再带的标签，不过要先修改applicationContext.xml中的文件协议头，加上util的描述:

<?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:jdbc="http://www.springframework.org/schema/jdbc" xmlns:jee="http://www.springframework.org/schema/jee"
	xmlns:tx="http://www.springframework.org/schema/tx" xmlns:jpa="http://www.springframework.org/schema/data/jpa"
	xmlns:util="http://www.springframework.org/schema/util" xmlns:mvc="http://www.springframework.org/schema/mvc"
	xsi:schemaLocation="
		http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-3.2.xsd
		http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-3.2.xsd
		http://www.springframework.org/schema/jdbc http://www.springframework.org/schema/jdbc/spring-jdbc-3.2.xsd
		http://www.springframework.org/schema/jee http://www.springframework.org/schema/jee/spring-jee-3.2.xsd
		http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx-3.2.xsd
		http://www.springframework.org/schema/data/jpa http://www.springframework.org/schema/data/jpa/spring-jpa-1.3.xsd
		http://www.springframework.org/schema/util http://www.springframework.org/schema/util/spring-util-3.2.xsd
		http://www.springframework.org/schema/mvc http://www.springframework.org/schema/mvc/spring-mvc-3.2.xsd">

接下来就可以使用了: 

<!-- 定义集合bean -->
	<util:list id="friendList">
		<value>jack</value>
		<value>kevin</value>
	</util:list>
	<util:set id="friendSet">
		<value>jack</value>
		<value>kevin</value>
	</util:set>
	<util:properties id="dbprop" >
		<prop key="username">root</prop>
		<prop key="password">root</prop>
	</util:properties>
	<util:map id="friendMap">
		<entry key="username" value="root"></entry>
		<entry key="password" value="root"></entry>
	</util:map>
	<!-- 引入上面定义的集合 -->
	<bean id="msgBean" class="com.tarena.MessageBean">
		<property name="someList" ref="friendList"></property>
		<property name="someSet" ref="friendSet"></property>
		<property name="someMap" ref="friendMap"></property>
		<property name="someProps" ref="dbprop"></property>
	</bean>

注入Spring表达式

<util:properties id="jdbc" 
		location="classpath:db.properties"/>
	<bean id="mydb" class="org.apache.commons.dbcp.datasources">
		<property name="username">#{jdbc.username}</property>
		<property name="password">#{jdbc.password}</property>
	</bean

注入null 或 空字符串

Spring将属性的空参数当作空字符串而不是null

<bean id="myBean' class="">
    <property name="username' value="">
<bean>

 如果注入null值则：

<bean id="myBean" class>
    <property name="username">
           <null/>
    <property>
 </bean>