js怎么传数据到servlet

<form action="YourServletURL" method="post">
    <input type="text" name="username" id="username">
    <input type="submit" value="Submit">
</form>

document.getElementById('username').value = 'JohnDoe';

protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    String username = request.getParameter("username");
    // 处理username
}

var xhr = new XMLHttpRequest();
xhr.open('POST', 'YourServletURL', true);
xhr.setRequestHeader('Content-Type', 'application/x-www-form-urlencoded');
xhr.onreadystatechange = function() {
    if (xhr.readyState === 4 && xhr.status === 200) {
        console.log(xhr.responseText);
    }
};
xhr.send('username=JohnDoe');

protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    String username = request.getParameter("username");
    // 处理username
    response.setContentType("text/plain");
    response.setCharacterEncoding("UTF-8");
    response.getWriter().write("Success");
}

fetch('YourServletURL', {
    method: 'POST',
    headers: {
        'Content-Type': 'application/x-www-form-urlencoded',
    },
    body: 'username=JohnDoe'
})
.then(response => response.text())
.then(result => console.log(result))
.catch(error => console.error('Error:', error));