异常之java.lang.nullpointerexception 怎么解决及出现原因？
空指针异常问题很常见,个人觉得有意义拿出谈谈HTTP Status 500 – Internal Server ErrorTypeException ReportDescriptionThe server encountered an unexpected condition that prevented it from fulfilling the request.Exceptionjava.lang.NullPointerException org.apache.catali..
