控制層@Value注解取不到值

 

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

 

如上所示，同樣的代碼，寫在在業務層，運行時能取到正確的值，但在控制層卻取得了@Value注解中的Key（@Value注解有個特點，如果取不到值，那么不是返回一個null，而是返回Key）。

 

原因是controller注冊在dispatcherservlet-servlet.xml代表的Spring MVC的容器中，而service則注冊在application-context.xml代表的Spring的容器中。

 

如果context:property-placeholder只注冊在Spring的容器中，那么自然只有業務層的類可以取到enable-upload-image的值，而控制器取不到值。

 

解決方法就是把各種context:property-placeholder在兩個容器中都注冊一下。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>