控制层@Value注解取不到值

    @Value("${enable-upload-image}")
    private String enable;

如上所示，同样的代码，写在在业务层，运行时能取到正确的值，但在控制层却取得了@Value注解中的Key（@Value注解有个特点，如果取不到值，那么不是返回一个null，而是返回Key）。

原因是controller注册在dispatcherservlet-servlet.xml代表的Spring MVC的容器中，而service则注册在application-context.xml代表的Spring的容器中。

如果context:property-placeholder只注册在Spring的容器中，那么自然只有业务层的类可以取到enable-upload-image的值，而控制器取不到值。

解决方法就是把各种context:property-placeholder在两个容器中都注册一下。如：

spring-properties.xml

<?xml version="1.0" encoding="UTF-8" ?>
<beans xmlns="http://www.springframework.org/schema/beans"
    xmlns:context="http://www.springframework.org/schema/context"
    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
                http://www.springframework.org/schema/context
                http://www.springframework.org/schema/context/spring-context.xsd">

    <context:property-placeholder
        location="classpath:wechat/official-account.properties"
        ignore-unresolvable="true" />

    <context:property-placeholder location="classpath:conf.properties"
        ignore-unresolvable="true" />

    <context:property-placeholder location="classpath:copywriting.properties"
        ignore-unresolvable="true" />

</beans>

application-context.xml

<?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">

    <import resource="classpath:springframework/spring-*.xml" />

</beans>

dispatcherservlet-servlet.xml

<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:mvc="http://www.springframework.org/schema/mvc" xmlns:aop="http://www.springframework.org/schema/aop"
    xsi:schemaLocation="http://www.springframework.org/schema/beans
            http://www.springframework.org/schema/beans/spring-beans.xsd
            http://www.springframework.org/schema/context
            http://www.springframework.org/schema/context/spring-context.xsd
            http://www.springframework.org/schema/mvc
            http://www.springframework.org/schema/mvc/spring-mvc.xsd
            http://www.springframework.org/schema/aop
            http://www.springframework.org/schema/aop/spring-aop.xsd">

    <!-- 其他配置忽略 -->

    <import resource="classpath:springframework/spring-properties.xml" />

</beans>