POST方法在Spring MVC中不起作用

我已经创建了一个登录表单

<form class="login100-form validate-form p-b-33 p-t-5" method="POST">
<div class="wrap-input100 validate-input" data-validate = "Enter username">
    <input class="input100" type="text" name="username" placeholder="User name">
    <span class="focus-input100" data-placeholder="&#xe82a;"></span>
</div>
<div class="wrap-input100 validate-input" data-validate="Enter password">
    <input class="input100" type="password" name="pass" placeholder="Password">
    <span class="focus-input100" data-placeholder="&#xe80f;"></span>
</div>
<div class="container-login100-form-btn m-t-32">
    <input class="login100-form-btn" type="button" onclick="location.href='eLibrary/login'" value="Login" >
</div>

我的控制器功能是

@RequestMapping(value = "/login", method = RequestMethod.POST)
public String login(HttpServletRequest request, HttpServletResponse response) {
    String userName = request.getParameter("username");
    String pass = request.getParameter("pass");
    return "list-books";
}

但是,当我尝试登录时,它给出了错误

HTTP状态405-不允许使用方法

不支持请求方法“GET”

我甚至试过

@PostMapping("/login")
public String login(HttpServletRequest request, HttpServletResponse response) {
    String userName = request.getParameter("username");
    String pass = request.getParameter("pass");
    return "list-books";
}

但在上述情况下,请求。getParameter(“username”)为null。

谁能帮帮我吗。