获取单个请求参数

采用 request.getParameter(标签名称) 方法

获取多个请求参数

采用 request.getParameterValues() 方法，多用于获取复合标签 checkbox 中，返回 String[ ] 数组类型。

获取所有请求参数名称

采用 request.getParameterNames() 方法，返回 Enumeration<String> 类型。

		Enumeration<String> parameterNames = request.getParameterNames();
		System.out.println("表单所有参数名称：");
		while (parameterNames.hasMoreElements()) {
			System.out.println(parameterNames.nextElement());
			
		}

获取所有请求参数

采用 request.getParameterMap() 方法，返回 Map<String, String[]> 类型，特别要注意该方法的遍历。

		Map<String, String[]> parameterMap = request.getParameterMap();
		System.out.println("表单所有参数：");
		for (Entry<String, String[]> entry : parameterMap.entrySet()) {
			System.out.println(entry.getKey());//获取键
			System.out.println(Arrays.toString(entry.getValue()));//获取键值
		}

上述内容综合代码

package com.RequestHttpServlet;

import java.io.IOException;
import java.util.Arrays;
import java.util.Enumeration;
import java.util.Map;
import java.util.Map.Entry;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

/**
 * Servlet implementation class ThirdRequestServlet
 */
@WebServlet("/ThirdRequestServlet")
public class ThirdRequestServlet extends HttpServlet {
	private static final long serialVersionUID = 1L;
       
    /**
     * @see HttpServlet#HttpServlet()
     */
    public ThirdRequestServlet() {
        super();
        // TODO Auto-generated constructor stub
    }

	/**
	 * @see HttpServlet#service(HttpServletRequest request, HttpServletResponse response)
	 */
	protected void service(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		// TODO Auto-generated method stub
		
		//获取单个请求参数
		String userName = request.getParameter("username");
		System.out.println("用户名是："+userName);
		
		//获取多个请求参数
		String[] parameterValues = request.getParameterValues("userhobby");
		System.out.println("用户爱好是：");
		System.out.println(Arrays.toString(parameterValues));
		
		//获取所有请求参数名称
		Enumeration<String> parameterNames = request.getParameterNames();
		System.out.println("表单所有参数名称：");
		while (parameterNames.hasMoreElements()) {
			System.out.println(parameterNames.nextElement());
			
		}
		
		//获取所有请求参数
		Map<String, String[]> parameterMap = request.getParameterMap();
		System.out.println("表单所有参数：");
		for (Entry<String, String[]> entry : parameterMap.entrySet()) {
			System.out.println(entry.getKey());//获取键
			System.out.println(Arrays.toString(entry.getValue()));//获取键值
		}
		
	}

}

<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>Insert title here</title>
</head>
<body>
	<form action="/JWDemo/ThirdRequestServlet" method="get">
		<input type="text" name="username" placeholder="请输入用户名">
		<br>
		<input type="radio" value="男"  name="usersex">男
		<input type="radio" value="女" name="usersex">女
		<br>
		<input type="checkbox" value="听音乐" name="userhobby">听音乐
		<input type="checkbox" value="运动" name="userhobby">运动
		<input type="checkbox" value="电子游戏" name="userhobby">电子游戏
		<br>
		<input type="submit" value="提交">
	</form>
</body>
</html>