@requestbody: How to Use or Not Use

First of all, note that @ requestbody accepts the JSON string
so write this

dataType:"json",
contentType: 'application/json',
data: JSON.stringify(data.field),

Instead of @ requestbody, you can directly receive the JSON type

dataType:"json",
data: data.field,

The situation of not using @ requestbody
front end page

$.ajax({
		url: "http://localhost:8081/role//saveOrUpdate",
		method:"post",
	   dataType:"json",     
			// contentType: 'application/json',
		data: data.field,   
		success(data){
			console.log("======================")
				console.log(data.field)
			if(data.code == 200){
			layer.msg('add success', function () {
			 window.location = 'list.html';
				}); 
				}
		},
error(data){
	console.log(data)
	if(data.code != 200){
layer.msg(data); 
								}
								}
							});

Back end:

@PostMapping("/saveOrUpdate")
    public Result saveOrUpdate(Roles roles){
        System.out.println(roles);
        boolean saveOrUpdate = roleService.saveOrUpdate(roles);
        if(saveOrUpdate == true)
            return Result.succ(null);
        else
            return Result.fail("failed to add");
    }

Using @ requestbody
front end:

$.ajax({
								url: "http://localhost:8081/role//saveOrUpdate",
								method:"post",
								dataType:"json",
								contentType: 'application/json',   
								data: JSON.stringify(data.field),  
								success(data){
									console.log("======================")
									console.log(data.field)
									if(data.code == 200){
										layer.msg('add success', function () {
										    window.location = 'list.html';
										}); 
									}
								},
								error(data){
									console.log(data)
									if(data.code != 200){
										layer.msg(data); 
								}
								}
							});

back-end

@PostMapping("/saveOrUpdate")
    public Result saveOrUpdate(@RequestBody Roles roles){
        System.out.println(roles);
        boolean saveOrUpdate = roleService.saveOrUpdate(roles);
        if(saveOrUpdate == true)
            return Result.succ(null);
        else
            return Result.fail("failed to add");
    }

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