HttpServletRequest
HttpServletRequest代表客户端的请求，用户通过Http协议访问服务器，Http请求中的所有信息会被封装到HttpServletRequest，通过这个HttpServletRequest的方法，获得客户端的所有信息.
1、获取前端传递的参数、请求转发
req.getParameter();
req.getParameterValues();
index.jsp
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
<title>登陆</title>
</head>
<body>
<h1>登陆</h1>
<div style="text-align: center">
<%-- 这里表单的意思，以post方式提交表单，提交到我们的Login请求--%>
<form action="${pageContext.request.contextPath}/login" method="post">
用户名：<input type="text" name="username"> <br>
密码：<input type="password" name="password"><br>
爱好：
<input type="checkbox" name="hobbys" value="唱歌">唱歌
<input type="checkbox" name="hobbys" value="代码">代码
<input type="checkbox" name="hobbys" value="跳舞">跳舞
<input type="checkbox" name="hobbys" value="电影">电影
<br>
<input type="submit">
</form>
</div>
</body>
</html>
success.jps
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
<title>Title</title>
</head>
<body>
<h1>登陆成功！</h1>
</body>
</html>
public class LoginServlet extends HttpServlet {
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
req.setCharacterEncoding("utf-8");
resp.setCharacterEncoding("utf-8");
String username = req.getParameter("username");
String password = req.getParameter("password");
String[] hobbys = req.getParameterValues("hobbys");
//后台接收 中文乱码问题
System.out.println("=================================================");
System.out.println(username);
System.out.println(password);
System.out.println(Arrays.toString(hobbys));
System.out.println("=================================================");
//重定向页面（跳转页面）
//通过请求转发
//这里的 / 代表当前的web应用
req.getRequestDispatcher("/success.jsp").forward(req,resp);
}
@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
doGet(req,resp);
}
}
<servlet>
<servlet-name>LoginServlet</servlet-name>
<servlet-class>com.kk.servlet.LoginServlet</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>LoginServlet</servlet-name>
<url-pattern>/login</url-pattern>
</servlet-mapping>
