Request&Response（请求?响应）

最后更新时间：2022年07月13日

Javaweb - day9 - Request&Response

简述

  • Request：获取请求数据
  • Response：设置响应数据

Requset

Request继承体系

  • Tomcat需要解析请求数据，封装为request对象，并且创建request对象传递到service方法中。
  • 使用request对象，查阅JavaEE API文档的HttpServletRequest接口。

Request获取请求数据

获取请求数据

  • 请求行
  • 请求头
  • 请求体

实例

package com.itheima.web.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.BufferedReader;
import java.io.IOException;

/**
 * request 获取请求数据
 */
@WebServlet("/req1")
public class RequestDemo1 extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        // String getMethod()：获取请求方式： GET
        String method = req.getMethod();
        System.out.println(method);//GET
        // String getContextPath()：获取虚拟目录(项目访问路径)：/request-demo
        String contextPath = req.getContextPath();
        System.out.println(contextPath);
        // StringBuffer getRequestURL(): 获取URL(统一资源定位符)：http://localhost:8080/request-demo/req1
        StringBuffer url = req.getRequestURL();
        System.out.println(url.toString());
        // String getRequestURI()：获取URI(统一资源标识符)： /request-demo/req1
        String uri = req.getRequestURI();
        System.out.println(uri);
        // String getQueryString()：获取请求参数（GET方式）： username=zhangsan
        String queryString = req.getQueryString();
        System.out.println(queryString);


        //------------
        // 获取请求头：user-agent: 浏览器的版本信息
        String agent = req.getHeader("user-agent");
        System.out.println(agent);


    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        //获取post 请求体：请求参数

        //1. 获取字符输入流
        BufferedReader br = req.getReader();
        //2. 读取数据
        String line = br.readLine();
        System.out.println(line);


    }
}

通用方式获取请求参数

servlet模板

实例

package com.itheima.web.request;

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

/**
 * request 通用方式获取请求参数
 */
@WebServlet("/req2")
public class RequestDemo2 extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        //GET请求逻辑
        //System.out.println("get....");

        //1. 获取所有参数的Map集合
        Map<String, String[]> map = req.getParameterMap();
        for (String key : map.keySet()) {
            // username:zhangsan lisi
            System.out.print(key+":");

            //获取值
            String[] values = map.get(key);
            for (String value : values) {
                System.out.print(value + " ");
            }

            System.out.println();
        }

        System.out.println("------------");

        //2. 根据key获取参数值，数组
        String[] hobbies = req.getParameterValues("hobby");
        for (String hobby : hobbies) {

            System.out.println(hobby);
        }

        //3. 根据key 获取单个参数值
        String username = req.getParameter("username");
        String password = req.getParameter("password");

        System.out.println(username);
        System.out.println(password);
    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        //POST请求逻辑

        this.doGet(req,resp);

        System.out.println("post....");

        //1. 获取所有参数的Map集合
        Map<String, String[]> map = req.getParameterMap();
        for (String key : map.keySet()) {
            // username:zhangsan lisi
            System.out.print(key+":");

            //获取值
            String[] values = map.get(key);
            for (String value : values) {
                System.out.print(value + " ");
            }

            System.out.println();
        }

        System.out.println("------------");

        //2. 根据key获取参数值，数组
        String[] hobbies = req.getParameterValues("hobby");
        for (String hobby : hobbies) {

            System.out.println(hobby);
        }

        //3. 根据key 获取单个参数值
        String username = req.getParameter("username");
        String password = req.getParameter("password");

        System.out.println(username);
        System.out.println(password);


    }
}

请求参数中文乱码处理

实例

package com.itheima.web.request;


import javax.servlet.*;
import javax.servlet.http.*;
import javax.servlet.annotation.*;
import java.io.IOException;
import java.nio.charset.StandardCharsets;

/**
 * 中文乱码问题解决方案
 */
@WebServlet("/req4")
public class RequestDemo4 extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //1. 解决乱码：POST，getReader()
        //request.setCharacterEncoding("UTF-8");//设置字符输入流的编码

        //2. 获取username
        String username = request.getParameter("username");
        System.out.println("解决乱码前："+username);

        //3. GET,获取参数的方式：getQueryString
        // 乱码原因：tomcat进行URL解码，默认的字符集ISO-8859-1
       /* //3.1 先对乱码数据进行编码：转为字节数组
        byte[] bytes = username.getBytes(StandardCharsets.ISO_8859_1);
        //3.2 字节数组解码
        username = new String(bytes, StandardCharsets.UTF_8);*/

        username  = new String(username.getBytes(StandardCharsets.ISO_8859_1),StandardCharsets.UTF_8);

        System.out.println("解决乱码后："+username);

    }

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

Request请求转发

请求转发特点

  • 浏览器地址栏路径不发生变化
  • 只能转发到当前服务器的内部资源
  • 一次请求，可以在转发的资源间使用request共享数据

实例（req5）

package com.itheima.web.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.nio.charset.StandardCharsets;

/**
 * 请求转发
 */
@WebServlet("/req5")
public class RequestDemo5 extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        System.out.println("demo5...");
        System.out.println(request);
        //存储数据
        request.setAttribute("msg","hello");

        //请求转发
        request.getRequestDispatcher("/req6").forward(request,response);

    }

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

实例（req6）

package com.itheima.web.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;

/**
 * 请求转发
 */
@WebServlet("/req6")
public class RequestDemo6 extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        System.out.println("demo6...");
        System.out.println(request);
        //获取数据
        Object msg = request.getAttribute("msg");
        System.out.println(msg);

    }

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

Response

Response设置响应数据功能介绍

Response完成重定向

重定向特点（和请求转发的特点相反）

  • 浏览器地址栏路径发生变化
  • 可以重定向到任意位置的资源（服务器内部、外部均可)
  • 两次请求，不能在多个资源使用request共享数据

路径问题

Response响应字符数据

Response响应字节数据

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