How to submit multiple sets of identical data (arrays) to the background with Ajax?

I wrote this in Ajax.

$ ("#subbutton"). Click (function () {
var machinecode_1=$ ("#machineCode_1"). Val ();
var machinecode_2=$ ("#machineCode_2"). Val ();
var machinecode_3=$ ("#machineCode_3"). Val ();
var machinecode_4=$ ("#machineCode_4"). Val ();
var machinecode_5=$ ("#machineCode_5"). Val ();
$.ajax ({
Type: "POST",
ContentType: "Application/json",
URL: "./system/dealer_addallmachcode",
Data: {machinearr: ([Machinecode_1,machinecode_2,machinecode_3,machinecode_4,machinecode_5]). Join (";")},
DataType: ' JSON ',
Success:function (Result) {
Alert ("Increased success");
}
});
});

Background SSM framework: Machinearr and get Set

Debug report NULL pointer error

Machinearr no data. Later after looking for inquiries to find the cause of the error, Application/json need to change to

application/x-www-form-urlencoded, but why did I check out their differences?
Application/json:application/json is the MIME type returned in the background, not the way the foreground submits. application/x-www-form-urlencoded: Form data is encoded as a name/value pair。 This is the standard encoding format. multipart/form-data: The form data is encoded as a message, and each control on the page corresponds to a part of the message。 Text/plain: Form data is encoded in plain text with no control or formatting characters.

The Enctype property of a form is encoded in two common ways: application/x-www-form-urlencoded and Multipart/form-data, which are application/by default. X-www-form-urlencoded. When action is get, the browser uses x-www-form-urlencoded encoding to convert the form data into a string (name1=value1& amp;name2=value2 ... ), and then append the string to the URL, using the. Split, to load the new URL. When the action is post, the browser encapsulates the form data into the HTTP body and then sends it to the server. If you don't have a type=file control, you can use the default application/x-www-form-urlencoded. But if you have type=file, you will need to use Multipart/form-data. The browser splits the entire form into units of controls and adds Content-disposition (form-data or file) to each section, Content-type (default = Text/plain), name (control name), and so on. and add the separator (boundary).

Summary: Client-submitted contenttype can only be application/x-www-form-urlencoded or multipart/form-data, and binary data uses multiple encodings. The preceding default encoding is the string, which is the file. But if you download from the server, the code is many, such as you say Application/json,text/plan,application/image ... All can be.

How to submit multiple sets of identical data (arrays) to the background with Ajax?