可以用 request.getReader() 读出来
参考一下：
StringBuffer buffer = new StringBuffer();
String line;
try {
BufferedReader reader = request.getReader();
while ((line = reader.readLine()) != null) {
buffer.append( line );
}
}
catch (Exception e) {
}finally {
}
String ClientMsg = buffer.toString(); //request.getParameter("ClientMsg");