jquery Asynchronous Request returns JSON

The first step: the front desk js Demo:

function SubmitForm () {
var hostname = $ ("#hostname"). Val ();
var port= $ ("#port"). Val ();
var validname= $ ("#validName"). Val ();
var vp= $ ("#vp"). Val ();
$.getjson ("req?Hostname= "+hostname+" &port= "+port+" &validname= "+validname+" &vp= "+VP, function (JSON) {
var ISS = json.issuccess//Front-end parsing
if (iss== "S") {
$ ("#etable"). Append ("<tr><td>" +hostname+ "</td><td>" +port+ "</td><td>" + Validname+ "</td><td>" +vp+ "</td><td>" +json.validcode+ "</td></tr>");
}
});
}

Step two: Back-end Demo:

@RequestMapping ("/main/req")
Public String Save () {
Date date = new Date ();
String hostname = this.request.getParameter ("hostname");
String port = this.request.getParameter ("port");
String validname = This.request.getParameter ("Validname");
String VP = this.request.getParameter ("VP");
String Validcode = "";
Validcode = dateformatutil.stringfromdate (date);
Validcode = Base64.encode (Validcode.getbytes ());
String savetime = dateformatutil.stringfromstanderdate (date);
String id = guid.getguid ();
Mailconfig mailconfig = new Mailconfig ();
Mailconfig.setid (ID);
Mailconfig.sethostname (hostname);
Mailconfig.setport (port);
Mailconfig.setsavetime (Savetime);
Mailconfig.setvalidcode (Validcode);
Mailconfig.setvalidname (Validname);
MAILCONFIG.SETVP (VP);
Boolean res = Mailservice.save (mailconfig);
map<string,object> returnmsg = new hashmap<string,object> ();
try {
if (res = = True) {
Returnmsg.put ("Issuccess", "S");
Returnmsg.put ("Validcode", Validcode);
this.response.getWriter (). Print (Jsonobject.fromobject (returnmsg));
}else {
Returnmsg.put ("Issuccess", "E");
This.response.getWriter (). Print (Jsonobject.fromobject (returnmsg));

}
} catch (IOException e) {
E.printstacktrace ();
}
return null;
}

jquery Asynchronous Request returns JSON