jsp页面中 用ajax 向servlet 传参

jsp中的js代码
XMLHttpReq.open("POST",url,true)//不能为GET
var params = "content="+document.getElementById("content1").value;
var params = encodeURI(params );
var params = encodeURI(params );//encodeURI 编码后传递参数到后台去，是要两次编码的
XMLHttpReq.setRequestHeader("Content-Type","application/x-www-form-urlencoded"); //要设置request头部
XMLHttpReq.send(params);


servlet端接收
String comment = request.getParameter("content"); //获得参数
try {
comment = java.net.URLDecoder.decode(comment, "utf-8"); //转码
} catch (UnsupportedEncodingException e) {
e.printStackTrace();
}