Controller里面写：
image.png
前台页面：
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Title</title>
</head>
<body>
文件上传
<form action="upload" method="post" enctype="multipart/form-data">
<div>
<input type="file" name="file">
</div>
<div>
<input type="submit" value="提交">
</div>
</form>
</body>
</html>
