Request请求和Response响应

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feilinli 2022-03-03 11:41:04 博主文章分类：Java Web ©著作权

文章标签 java 服务器 http request response 文章分类 Java 后端开发

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Request请求和Response响应

1 Request请求

1.1 Request请求行数据
1.2 Request获取请求头数据
1.3 Request获取请求体数据
1.4 获取请求参数通用方式

get请求不会乱码，post请求乱码解决

1.5 请求转发（服务器内部的资源跳转方式）
1.6 共享数据

2 Response响应

2.1 重定向2.2 服务器输出字符数据到浏览器2.3 服务器输出字节数据到浏览器2.4 验证码

3 ServletContext对象

1 Request请求

1.1 Request请求行数据

package Request;

import javax.servlet.*;
import javax.servlet.http.*;
import javax.servlet.annotation.*;
import java.io.IOException;

/**
 * Request请求行数据
 */
@WebServlet("/RequestServlet")
public class RequestServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
//        Request获取请求方式
        String method = request.getMethod();
        System.out.println(method);
//        Request获取虚拟目录
        String contextPath = request.getContextPath();
        System.out.println(contextPath);
//        获取servlet路径
        String servletPath = request.getServletPath();
        System.out.println(servletPath);
//        获取get请求方式的请求参数
        String name = request.getQueryString();
        System.out.println(name);
//        获取请求方法的URI URL
        String requestURI = request.getRequestURI();
        System.out.println(requestURI);
        StringBuffer requestURL = request.getRequestURL();
        System.out.println(requestURL);
//        获取协议及版本
        String protocol = request.getProtocol();
        System.out.println(protocol);
//        获取客户机的IP
        String remoteAddr = request.getRemoteAddr();
        System.out.println(remoteAddr);
    }

    @Override
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    }
}

Request请求和Response响应_java

1.2 Request获取请求头数据

package Request;

import javax.servlet.*;
import javax.servlet.http.*;
import javax.servlet.annotation.*;
import java.io.IOException;
import java.util.Enumeration;

/**
 * Request获取请求头数据
 */
@WebServlet("/RequestServlet_02")
public class RequestServlet_02 extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
//获取所有请求头名称
        Enumeration<String> headerNames = request.getHeaderNames();
//        遍历
        while (headerNames.hasMoreElements()) {
            String name = headerNames.nextElement();
//            根据名称获取请求头的值
            String value = request.getHeader(name);
            System.out.println(name + "=" + value);
        }
        System.out.println("===================================================");
//案例：        演示获取请求头数据：user-agent
        String agent = request.getHeader("user-agent");
//        判断agent的浏览器版本
        if (agent.contains("Chrome")) {
            System.out.println("我是谷歌浏览器");
        } else if (agent.contains("Firefox")) {
            System.out.println("我是火狐浏览器");
        }
        System.out.println("===================================================");
//案例：        演示获取请求头数据：referer
        String referer = request.getHeader("referer");
        System.out.println(referer);
    }

    @Override
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    }
}

Request请求和Response响应_request_02

1.3 Request获取请求体数据

仅有post请求才能获取到请求体数据，在项目的web目录下建立一个regist.html文件：

Request请求和Response响应_request_03

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>注册页面</title>
</head>
<body>
<form action="http://localhost:8080/HttpServlet_war_exploded//RequestServlet_03" method="post">
    <input type="text" name="username" placeholder="请输入用户名"><br>
    <input type="text" name="password" placeholder="请输入密码"><br>
    <input type="submit" value="注册">
</form>
</body>
</html>

在项目的src下建立一个RequestServlet_03文件：

package Request;

import javax.servlet.*;
import javax.servlet.http.*;
import javax.servlet.annotation.*;
import java.io.BufferedReader;
import java.io.IOException;

/**
 * 获取请求消息体
 */
@WebServlet("/RequestServlet_03")
public class RequestServlet_03 extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    }

    @Override
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //获取请求消息体，请求参数
        // 获取字符流
        BufferedReader reader = request.getReader();
        // 读取数据
        String line = null;
        while ((line = reader.readLine()) != null) {
            System.out.println(line);
        }
    }
}

启动服务器，访问regist.html文件，填写用户名和密码参数进行提交，可以在IDEA控制台获取到该表单提交的参数信息。

Request请求和Response响应_服务器_04

Request请求和Response响应_服务器_05

1.4 获取请求参数通用方式

在JavaEE项目的web目录下创建regist2.html文件：

Request请求和Response响应_http_06

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>注册页面</title>
</head>
<body>
<form action="http://localhost:8080/HttpServlet_war_exploded//RequestServlet_04" method="post">
    <input type="text" name="username" placeholder="请输入用户名"><br>
    <input type="text" name="password" placeholder="请输入密码"><br>
    <input type="checkbox" name="hobby" value="game">游戏
    <input type="checkbox" name="hobby" value="play">玩耍
    <input type="checkbox" name="hobby" value="study">学习
    <br>
    <input type="submit" value="注册">
</form>
</body>
</html>

创建RequestServlet_04类：

package 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;
import java.util.Map;
import java.util.Set;

/**
 * 获取请求消息体
 */
@WebServlet("/RequestServlet_04")
public class RequestServlet_04 extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //get获取请求参数
        // 1 根据参数名称获取参数值
        String parameter = request.getParameter("username");
        System.out.println("get");
        System.out.println(parameter);
        System.out.println("-------------------------------------------");
        // 2 根据参数名称获取参数值的数组
        String[] hobbies = request.getParameterValues("hobby");
        for (String hobby : hobbies
        ) {
            System.out.println(hobby);
        }
        System.out.println("-------------------------------------------");
        // 3 获取所有请求的参数名称
        Enumeration<String> parameterNames = request.getParameterNames();
        while (parameterNames.hasMoreElements()) {
            String name = parameterNames.nextElement();
            System.out.println(name);
            String value = request.getParameter(name);
            System.out.println(value);
            System.out.println("=====================");
        }
        System.out.println("-------------------------------------------");
        // 4 获取所有参数的map集合
        Map<String, String[]> parameterMap = request.getParameterMap();
        // 遍历
        Set<String> keySet = parameterMap.keySet();
        for (String name : keySet
        ) {
            // 获取键获取值
            String[] values = parameterMap.get(name);
            System.out.println(name);
            for (String value : values
            ) {
                System.out.println(value);
            }
            System.out.println("=====================");
        }
    }

    @Override
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //post获取请求参数
        //根据参数名称获取参数值
//        System.out.println("post");
//        String parameter = request.getParameter("username");
//        System.out.println(parameter);
        this.doGet(request, response);
    }
}

启动服务器，访问regist2.html文件，输入参数进行提交：

Request请求和Response响应_request_07

Request请求和Response响应_request_08

get请求不会乱码，post请求乱码解决

在执行请求时执行流的编码：

request.setCharacterEncoding("utf-8");

1.5 请求转发（服务器内部的资源跳转方式）

创建两个Java文件：RequestServlet_05、RequestServlet_06，通过访问RequestServlet_05后，跳转继续访问到RequestServlet_06。

package Request;

import javax.servlet.RequestDispatcher;
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("/RequestServlet_05")
public class RequestServlet_05 extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        request.setCharacterEncoding("utf-8");
        System.out.println("RequestServlet_05被访问了......");
//        请求转发
//        RequestDispatcher requestDispatcher = request.getRequestDispatcher("/RequestServlet_06");
//        requestDispatcher.forward(request,response);
        request.getRequestDispatcher("/RequestServlet_06").forward(request, response);
    }

    @Override
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        this.doGet(request, response);
    }
}

package 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("/RequestServlet_06")
public class RequestServlet_06 extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        request.setCharacterEncoding("utf-8");
        System.out.println("RequestServlet_06被访问了......");
    }

    @Override
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        this.doGet(request, response);
    }
}

Request请求和Response响应_java_09

特点：
1、浏览器地址不发生变化
2、只能转发到当前服务器内部资源
3、转发是一次请求

1.6 共享数据

借助上面转发的两个例子：在RequestServlet_05中定义一个name变量，值设为beijing，转发后在RequestServlet_06中可以获取到这个数据。

package Request;

import javax.servlet.RequestDispatcher;
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("/RequestServlet_05")
public class RequestServlet_05 extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        request.setCharacterEncoding("utf-8");

        //转发前存储数据到request域中
        request.setAttribute("name","beijing");


        System.out.println("RequestServlet_05被访问了......");
//        请求转发
//        RequestDispatcher requestDispatcher = request.getRequestDispatcher("/RequestServlet_06");
//        requestDispatcher.forward(request,response);
        request.getRequestDispatcher("/RequestServlet_06").forward(request, response);
    }

    @Override
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        this.doGet(request, response);
    }
}

package 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("/RequestServlet_06")
public class RequestServlet_06 extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        request.setCharacterEncoding("utf-8");
        System.out.println("RequestServlet_06被访问了......");

        //转发后获取共享数据
        Object name = request.getAttribute("name");
        System.out.println(name);
    }

    @Override
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        this.doGet(request, response);
    }
}

Request请求和Response响应_request_10

2 Response响应

2.1 重定向

Request请求和Response响应_服务器_11

package Response;

import javax.servlet.*;
import javax.servlet.http.*;
import javax.servlet.annotation.*;
import java.io.IOException;

/**
 * 重定向
 */
@WebServlet("/ResponseServlet_01")
public class ResponseServlet_01 extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        System.out.println("ResponseServlet_01...");
        //重定向，当访问ResponseServlet_01时，自动跳转到ResponseServlet_02资源
//        // 1 设置状态码为302
//        response.setStatus(302);
//        // 2 设置响应头location
//        response.setHeader("location","ResponseServlet_02");

        //重定向的简化写法
        response.sendRedirect("ResponseServlet_02");
    }

    @Override
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        this.doGet(request, response);
    }
}

package Response;

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("/ResponseServlet_02")
public class ResponseServlet_02 extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        System.out.println("ResponseServlet_02...");
    }

    @Override
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        this.doGet(request,response);
    }
}

重定向特点：
1、地址发生变化
2、可以访问其他站点资源
3、重定向是两次请求，不能共享数据

2.2 服务器输出字符数据到浏览器

服务器传送数据至浏览器中文乱码解决：

//        获取流对象之前设置编码方式，告诉浏览器，服务器发送的消息体数据的编码
        response.setContentType("text/html;charset=utf-8");

package Response;

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.io.PrintWriter;

@WebServlet("/ResponseServlet_03")
public class ResponseServlet_03 extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
//        获取流对象之前设置编码方式，告诉浏览器，服务器发送的消息体数据的编码
        response.setContentType("text/html;charset=utf-8");

        //获取字符输出流
        PrintWriter pw = response.getWriter();
        //输出数据
        pw.write("hello(你好) , response");
    }

    @Override
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        this.doGet(request, response);
    }
}

2.3 服务器输出字节数据到浏览器

package Response;

import javax.servlet.ServletException;
import javax.servlet.ServletOutputStream;
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.nio.charset.StandardCharsets;

@WebServlet("/ResponseServlet_04")
public class ResponseServlet_04 extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
//        获取流对象之前设置编码方式，告诉浏览器，服务器发送的消息体数据的编码
        response.setContentType("text/html;charset=utf-8");

        //获取字节输出流
        ServletOutputStream outputStream = response.getOutputStream();
        //输出数据
        outputStream.write("你好".getBytes(StandardCharsets.UTF_8));
    }

    @Override
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        this.doGet(request, response);
    }
}

2.4 验证码

写一个regist.html文件，模拟简单登录页面，使用标签插入服务器中的图片验证码：

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>注册页面</title>
    <script>
        window.onload = function () {
            //获取图片对象
            var img = document.getElementById("check");
            //绑定单击事件
            img.onclick = function () {
                //加时间戳
                var date = new Date().getTime();
                img.src = "/HttpServlet_war_exploded/ResponseServlet_05?" + date;
            }

            //获取文字对象
            var text = document.getElementById("change");
            //绑定单击事件
            text.onclick = function () {
                //加时间戳
                var date = new Date().getTime();
                img.src = "/HttpServlet_war_exploded/ResponseServlet_05?" + date;
            }
        }
    </script>
</head>
<body>
<form action="http://localhost:8080/HttpServlet_war_exploded//RequestServlet_03" method="post">
    <input type="text" name="username" placeholder="请输入用户名"><br>
    <input type="text" name="password" placeholder="请输入密码"><br>
    <img id="check" src="/HttpServlet_war_exploded/ResponseServlet_05"/>
    <br>
    <a id="change" href="#">看不清，换一张</a>
    <input type="submit" value="注册">
</form>
</body>
</html>

package Response;

import javax.imageio.ImageIO;
import javax.servlet.ServletException;
import javax.servlet.ServletOutputStream;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.awt.*;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.util.Random;

@WebServlet("/ResponseServlet_05")
public class ResponseServlet_05 extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        int width = 100;
        int height = 50;
        //1.创建一对象，在内存中图片（验证码图片对象）
        BufferedImage bufferedImage = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);
        //2.美化图片
        //2.1 填充背景色
        Graphics graphics = bufferedImage.getGraphics();//画笔对象
        graphics.setColor(Color.PINK);
        graphics.fillRect(0, 0, width, height);
        //2.2 画边框
        graphics.setColor(Color.BLUE);
        graphics.drawRect(0, 0, width - 1, height - 1);
        //2.3写验证码
        String str = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxqz0123456789";
        //生成随机角标
        Random random = new Random();
        for (int i = 0; i <= 4; i++) {
            int index = random.nextInt(str.length());
            //获取字符
            char c = str.charAt(index);
            //2.3 写验证码
            graphics.drawString(c + "", width / 5 * i, height / 2);
        }
        //2.4画干扰线
        graphics.setColor(Color.GREEN);
        //随机生成坐标点
        for (int i = 0; i < 10; i++) {
            int x1 = random.nextInt(width);
            int x2 = random.nextInt(width);
            int y1 = random.nextInt(height);
            int y2 = random.nextInt(height);
            graphics.drawLine(x1, y1, x2, y2);
        }
        //3.将图片输出到页面展示
        ImageIO.write(bufferedImage, "jpg", response.getOutputStream());
    }

    @Override
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        this.doGet(request, response);
    }
}

Request请求和Response响应_response_12

3 ServletContext对象

Request请求和Response响应_服务器_13

package ServletContext;

import javax.servlet.*;
import javax.servlet.http.*;
import javax.servlet.annotation.*;
import java.io.IOException;

@WebServlet(name = "ServletContext_01", value = "/ServletContext_01")
public class ServletContext_01 extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // 获取ServletContext对象
        //获取方式1
//        ServletContext servletContext1 = request.getServletContext();
        //获取方式2
        ServletContext servletContext2 = this.getServletContext();

        // 定义一个文件名称
        String filename = "beijing.html";
        // 1    获取MIME类型
        String mimeType = servletContext2.getMimeType(filename);
        System.out.println(mimeType);   //text/html

        // 2    获取文件服务器路径
        // 分别获取web目录下，web目录下的WEB-INF目录下，以及src目录下的文件地址
        String realPath = servletContext2.getRealPath("/b.txt");//获取web目录
        String realPath1 = servletContext2.getRealPath("/WEB-INF/c.txt");//web目录下的WEB-INF目录下
        String realPath2 = servletContext2.getRealPath("/WEB-INF/classes/a.txt");//src目录下的文件地址
        System.out.println(realPath);
        System.out.println(realPath1);
        System.out.println(realPath2);
    }

    @Override
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        this.doGet(request, response);
    }
}

Request请求和Response响应_response_14

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