Tomcat7.0.63之前：
maxPostSize The maximum size in bytes of the POST which will be handled by the container FORM URL parameter parsing.
The limit can be disabled by setting this attribute to a value less than or equal to 0. If not specified, this attribute is set to 2097152 (2 megabytes).
设置为0和负数均可以代表不限制
Tomcat7.0.63（包含）之后：
maxPostSize The maximum size in bytes of the POST which will be handled by the container FORM URL parameter parsing.
The limit can be disabled by setting this attribute to a value less than zero. If not specified, this attribute is set to 2097152 (2 megabytes / 2 MB ).
不可以设置为0，只能是负数代表不限制一般取 -1
来源：oschina
链接：https://my.oschina.net/HeAlvin/blog/4339242