Attribute "resource" 问题

Attribute "resource" must be declared for element type "mapper"

为什么resource这里会出错

 <?xml version="1.0" encoding="UTF-8"?>  
<!DOCTYPE configuration PUBLIC "-//mybatis.org//DTD Config 3.0//EN"    
"http://mybatis.org/dtd/mybatis-3-config.dtd">

<configuration>

    <environments default="mysql_developer">
        <environment id="mysql_developer">
            <transactionManager type="jdbc"/>   
            <dataSource type="pooled">
                <property name="driver" value="com.mysql.jdbc.Driver"/>
                <property name="url" value="jdbc:mysql://localhost:3306/mybatis"/>
                <property name="username" value="root"/>
                <property name="password" value="123456"/>
            </dataSource>
        </environment>
    </environments>

    <mappers>
        <mapper resource="Nov18/service/usermapper.xml" />
    </mappers>


</configuration>

试试改下第一行的<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
"http://mybatis.org/dtd/mybatis-3-mapper.dtd">

Nov18/service/usermapper.xml 路径这里确定没写错吗?

这个错误以前没有，删了.metadata文件从新导入就成这样。是配置的问题吗？