为什么此错误出现在我的配置文件中？

Question

线程“主”中的异常org.springframework.beans.factory.xml.XmlBeanDefinitionStoreException：文件[D：\ eclipse-workspace \ spring \ IOC13-ApllicationContextContainerWithCustomer \ src \ org \ pp \ config \ applicationcontext.xml]无效；嵌套的异常是org.xml.sax.SAXParseException; lineNumber：21； columnNumber：36； cvc-complex-type.2.4.a：发现无效的内容（从元素“属性”开始）。 '{“ http://www.springframework.org/schema/beans”：导入，“ http://www.springframework.org/schema/beans”：别名，“ http://www.springframework.org/schema/beans”：bean，WC [## other：“ http://www.springframework.org/schema/beans”]，应该是http://www.springframework.org/schema/beans“：beans}'。

这是我的spring bean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">

<!-- configure property placeholder configurer -->
<bean id  ="pphc" class = "org.springframework.beans.factory.config.PropertyPlaceholderConfigurer">
<property name = "location" value = "src/org/pp/commons/DBdetails.properties"/>
</bean>

<!-- configure DriverManager datasource -->
<bean id = "dds" class = "org.springframework.jdbc.datasource.DriverManagerDataSource">
<property name = "driverClassName" value= "${jdbc.driver}"/>
<property name = "url" value= "${jdbc.url}"/>
<property name = "username" value= "${jdbc.user}"/>
<property name = "password" value= "${jdbc.pwd}"/>
</bean>

<!-- configure DAO -->
<bean id = "dao" class = "org.pp.dao.ResultDAO"/>
<property name = "ds" ref = "dds"/>
</bean>

<!-- configure service -->
<bean id = "service" class="org.pp.service.StudentService">
<property name ="dao" ref="dao"/>
</bean>

</beans>

为什么无法配置数据源ds以注入到dao组件中？