使用shiro安全框架上传文件时用HttpSession获取ServletContext为null问题解决方法。

   <!--在shiroFilter 中加入一下配置-->

　　<init-param>
        <param-name>targetFilterLifecycle</param-name>
        <param-value>true</param-value>
    </init-param>

　　<!--shiroFilter配置 -->

　　<filter>
        <filter-name>shiroFilter</filter-name>
        <filter-class>org.springframework.web.filter.DelegatingFilterProxy</filter-class>
        <init-param>
            <param-name>targetFilterLifecycle</param-name>
            <param-value>true</param-value>
        </init-param>
    </filter>
    <filter-mapping>
        <filter-name>shiroFilter</filter-name>
        <url-pattern>/*</url-pattern>
    </filter-mapping> 
                

　　　　 ServletContext context = session.getServletContext();
        String path = context.getRealPath("upload");
        String fileName = file.getOriginalFilename();
        System.out.println(path);
        File targetFile = new File(path, fileName);
        if(!targetFile.exists()){
            targetFile.mkdirs();
        }