Question

是Post提交的参数过长原因造成的吗

Answer 1

在servlet规范3.1.1节里，对POST数据何时会被当做parameters有描述：
1. The request is an HTTP or HTTPS request.
2. The HTTP method is POST.
3. The content type is application/x-www-form-urlencoded.
4. The servlet has made an initial call of any of the getParameter family of methods on the request object.

If the conditions are met, post form data will no longer be available for reading directly from the request object’s input stream.

规范里已经明确的声明当请求满足: 1) http/https, 2) POST, 3) Content-type 是application/x-www-form-urlencoded, 4) 调用过getParameter方法；则数据会被当做请求的paramaters，而不能再通过 request 的 inputstream 直接读取。