HTTP Status 请教什么原因？500 - Request processing failed; nested exception is java.lang.NullPointerException

HTTP状态为什么要问？500 -请求处理失败；NestedException是Java . lang . nullpointerexception http状态。为什么这么问？500 -请求处理失败；nested Exception is Java . lang . nullpointerexception简介:类型异常报告 消息请求处理失败；嵌套异常是java.lang.NullPointerE