ACME包中的以POST方式发送数//AURLConnectionthatimplementsPOST.////SomeimplementationsofURLConnection,e.g.theoneinNavigator3.0,//donotsupportPOST.Thisisastripped-downversionthatdoes.////Notethatitcan'tinheritfromjava.net.URLConnectionbecausethat//classhasnopublicconstruct