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Request和Response学习笔记3

获取请求参数通用方式

 String getParameter(String name)
 // 根据参数名称获取参数值
 
 String[] getParameterValues(String name)
 // 根据参数名称获取参数值的数组 
 
 Enumeration<String> getParameterNames()
 // 获取所有请求的参数名称
 
 Map<String,String[]> getParameterMap()
 // 获取所有参数的map集合

无论get还是post请求方式都可以使用这些方法来获取请求参数

根据参数获取参数值

创建一个html文件：login02.html

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>用户登录</title>
</head>
<body>
    <form action="/RequestAndResponse_war_exploded/study/request/demo04" method="post">
        <input type="email" name="userEmail" placeholder="请输入您的邮箱"><br>
        <input type="password" name="userPassword" placeholder="请输入您的密码"><br>
        <input type="submit" value="post登录">
    </form>
    <br>
    <form action="/RequestAndResponse_war_exploded/study/request/demo04" method="get">
        <input type="email" name="userEmail" placeholder="请输入您的邮箱"><br>
        <input type="password" name="userPassword" placeholder="请输入您的密码"><br>
        <input type="submit" value="get登录">
    </form>
</body>
</html>

创建一个类，RequestDemo04.java

package study.request;

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

@WebServlet("/study/request/demo04")
public class RequestDemo04 extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp)
            throws ServletException, IOException {
        String userEmail = req.getParameter("userEmail");
        String userPassword = req.getParameter("userPassword");
        System.out.println("userEmail = " + userEmail + "
" + "userPassword = " + userPassword);
    }
    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp)
            throws ServletException, IOException {
        String userEmail = req.getParameter("userEmail");
        String userPassword = req.getParameter("userPassword");
        System.out.println("userEmail = " + userEmail + "
" + "userPassword = " + userPassword);
    }
}

上面的 doGet() 方法和 doPost() 方法中的方法体内容一样，可以进行修改：

public class RequestDemo04 extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp)
            throws ServletException, IOException {
        String userEmail = req.getParameter("userEmail");
        String userPassword = req.getParameter("userPassword");
        System.out.println("userEmail = " + userEmail + "
" + "userPassword = " + userPassword);
    }
    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp)
            throws ServletException, IOException {
        this.doGet(req, resp);
    }
}

浏览器访问：http://localhost:8080/RequestAndResponse_war_exploded/login02.html
- Post 请求
  
  控制台输出：
```
userEmail = post@icloud.com
userPassword = 123456
```
  页面跳转到：http://localhost:8080/RequestAndResponse_war_exploded/study/request/demo04
- Get 请求
  
  控制台输出：
```
userEmail = get@icloud.com
userPassword = abcdef
```
  页面跳转到：http://localhost:8080/RequestAndResponse_war_exploded/study/request/demo04?userEmail=get%40icloud.com&userPassword=abcdef

根据参数名称获取参数值的数组

创建一个html文件：login03.html

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>爱好</title>
</head>
<body>
    <form action="/RequestAndResponse_war_exploded/study/request/demo05" method="post">
        <input type="checkbox" name="hobby" value="study"> 学习
        <input type="checkbox" name="hobby" value="game"> 游戏 <br>
        <input type="submit" value="post提交">
    </form>
    <br>
    <form action="/RequestAndResponse_war_exploded/study/request/demo05" method="get">
        <input type="checkbox" name="hobby" value="study"> 学习
        <input type="checkbox" name="hobby" value="game"> 游戏 <br>
        <input type="submit" value="get提交">
    </form>
</body>
</html>

创建一个demo.java：RequestDemo05.java

package study.request;

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

@WebServlet("/study/request/demo05")
public class RequestDemo05 extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp)
            throws ServletException, IOException {
        // 根据参数名称获取参数值的数组
        String[] hobbies = req.getParameterValues("hobby");     // 参数名称为hobby
        for (String hobby : hobbies) {
            System.out.println(hobby);
        }
    }
    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp)
            throws ServletException, IOException {
        this.doGet(req, resp);
    }
}

启动服务器，访问：http://localhost:8080/RequestAndResponse_war_exploded/login03.html

这里两种提交方式都一样！！！
- 选择：study，并提交，控制台输出
```
study    
```
  浏览器页面跳转到：http://localhost:8080/RequestAndResponse_war_exploded/study/request/demo05
- 选择：study、game并提交，控制台输出
```
study    game    
```
  浏览器页面跳转到：http://localhost:8080/RequestAndResponse_war_exploded/study/request/demo05

获取所有请求的参数名称

创建一个类，RequestDemo06.java

package study.request;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.util.Enumeration;

@WebServlet("/study/request/demo06")
public class RequestDemo06 extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp)
            throws ServletException, IOException {
        // 获取所有请求参数名称
        Enumeration<String> parameterNames = req.getParameterNames();
        while (parameterNames.hasMoreElements()) {
            String parameterName = parameterNames.nextElement();
            // 输出参数名称，已经根据参数名称输出对应的值
            System.out.println(parameterName + ":" + req.getParameter(parameterName) + "
");
        }
    }
    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp)
            throws ServletException, IOException {
        this.doGet(req, resp);
    }
}

创建余个html文件：login04.html

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>用户爱好</title>
</head>
<body>
<form action="/RequestAndResponse_war_exploded/study/request/demo06" method="get">
    <label><input type="email" name="userEmail" placeholder="请输入您的邮箱"></label><br>
    <label><input type="password" name="userPassword" placeholder="请输入您的密码"></label><br>
    <label><input type="checkbox" name="hobby1" value="study"></label> 学习
    <label><input type="checkbox" name="hobby2" value="game"></label> 游戏 <br>
    <input type="submit" value="提交">
</form>
</body>
</html>

启动服务器，访问：http://localhost:8080/RequestAndResponse_war_exploded/login04.html

提交，控制台输出：
```
userEmail:stringbug@icloud.com

userPassword:123456

hobby1:study

hobby2:game
```
浏览器页面跳转到：http://localhost:8080/RequestAndResponse_war_exploded/study/request/demo06?userEmail=stringbug%40icloud.com&userPassword=123456&hobby1=study&hobby2=game

获取所有参数的map集合

创建一个html文件：login05.html

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>用户爱好</title>
</head>
<body>
<form action="/RequestAndResponse_war_exploded/study/request/demo07" method="get">
    <label><input type="email" name="userEmail" placeholder="请输入您的邮箱"></label><br>
    <label><input type="password" name="userPassword" placeholder="请输入您的密码"></label><br>
    <label><input type="checkbox" name="hobby" value="study"></label> 学习
    <label><input type="checkbox" name="hobby" value="game"></label> 游戏 <br>
    <input type="submit" value="提交">
</form>
</body>
</html>

login05.html 与 login04.html 的差别是：将hobby1、hobby2均改为了hobby

将路径中的demo06改为了demo07

创建一个类：RequestDemo07.java

package study.request;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.util.Map;
import java.util.Set;

@WebServlet("/study/request/demo07")
public class RequestDemo07 extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp)
            throws ServletException, IOException {
        // 获取所有请求参数的map集合
        Map<String, String[]> parameterMap = req.getParameterMap();
        // 获取所有的请求名称
        Set<String> parameterNames = parameterMap.keySet();
        for (String parameterName : parameterNames) {
            // 输出每个请求名称
            System.out.println("请求名称 -- " + parameterName);
            // 根据请求名称获取对应的请求值
            String[] parameterValues = req.getParameterValues(parameterName);
            for (String parameterValue : parameterValues) {
                // 输出每个请求值
                System.out.println(parameterName + ":" + parameterValue);
            }
        }
    }
    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp)
            throws ServletException, IOException {
        this.doGet(req, resp);
    }
}

启动服务器，访问：http://localhost:8080/RequestAndResponse_war_exploded/login05.html
提交，控制台输出：
```
请求名称 -- userEmail
userEmail:stringbug@icloud.com
请求名称 -- userPassword
userPassword:123456
请求名称 -- hobby
hobby:study
hobby:game
```
浏览器页面跳转到：http://localhost:8080/RequestAndResponse_war_exploded/study/request/demo07?userEmail=stringbug%40icloud.com&userPassword=123456&hobby=study&hobby=game

参考文献

无

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原文地址：https://www.cnblogs.com/liyihua/p/14477444.html