一篇部落格上手request和response

鶴城發表於2023-04-19

概念

request：獲取請求資料
response：設定響應資料

Request

request繼承體系

ServletRequest——Java提供的請求物件根介面
HttpServletRequest——Java提供的對http協議封裝的請求物件介面
RequestFacade——tomcat實現定義類

request獲取資料

package com.itheijma.web;

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;

@WebServlet("/req1")
public class RequestDemo1 extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        //String method() 獲取請求方式
        String method = req.getMethod();
        System.out.println(method);
        //String getContextPath() 獲取虛擬目錄（專案訪問路徑）
        String contextPath = req.getContextPath();
        System.out.println(contextPath);
        //StringBuffer getRequestURL() 獲取URL（統一資源定位符）
        StringBuffer url = req.getRequestURL();
        System.out.println(url.toString());
        //String getRequestURI() 獲取URI（統一資源識別符號）
        String uri = req.getRequestURI();
        System.out.println(uri);
        //String getQueryString() 獲取請求引數（get方式）
        String queryString = req.getQueryString();
        System.out.println(queryString);

        //------------
        //獲取請求頭
        String agent = req.getHeader("user-agent");
        System.out.println(agent);
    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        //獲取post請求體：請求引數

        // 1. 獲取字元輸入流
        BufferedReader br = req.getReader();
        // 2. 讀取資料
        String line = br.readLine();
        System.out.println(line);

    }
}

request通用的方式獲取資料

package com.itheijma.web;

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;

@WebServlet("/req2")
public class RequestDemo2 extends HttpServlet{
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        //get請求邏輯
//        System.out.println("get...");

        // 1.獲取所有引數的map集合
        Map<String, String[]> map = req.getParameterMap();
        for (String key : map.keySet()) {
            //username:zhangsan
            System.out.print(key+":");

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

            System.out.println();
        }

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

        // 2.根據key獲取引數值，陣列
        String[] hobbies = req.getParameterValues("hobby");
        for (String hobby : hobbies) {

            System.out.println(hobby);
        }

        // 3. 根據key獲取單個引數值
        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請求邏輯
        this.doGet(req,resp);


//        System.out.println("post...");
//        // 1.獲取所有引數的map集合
//        Map<String, String[]> map = req.getParameterMap();
//        for (String key : map.keySet()) {
//            //username:zhangsan
//            System.out.print(key+":");
//
//            //獲取值
//            String[] values = map.get(key);
//            for (String value : values) {
//                System.out.print(value + " ");
//            }
//
//            System.out.println();
//        }
//
//        System.out.println("----------");
//
//        // 2.根據key獲取引數值，陣列
//        String[] hobbies = req.getParameterValues("hobby");
//        for (String hobby : hobbies) {
//
//            System.out.println(hobby);
//        }
//
//        // 3. 根據key獲取單個引數值
//        String username = req.getParameter("username");
//        String password = req.getParameter("password");
//        System.out.println(username);
//        System.out.println(password);


    }
}

request請求引數中文亂碼解決方法

package com.itheijma.web;



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;


/**
 * 中文亂碼問題解決方案
 */
@WebServlet("/req3")
public class RequestDemo3 extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        this.doGet(request, response);
    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // 1. 解決亂碼 POST 獲取引數方式:getReader()讀取資料流
        request.setCharacterEncoding("utf-8"); //設定字元輸入流的編碼


        // 2. 獲取username
        String username = request.getParameter("username");
        System.out.println("解決亂碼前："+username);


        // 3. 解決亂碼 GET 獲取引數方式:getQueryString
        // 亂碼原因：tomcat進行url解碼，預設的字符集ISO-8859-1
//        // 3.1 先對亂碼資料進行編碼：轉為位元組陣列
//        byte[] bytes = username.getBytes(StandardCharsets.ISO_8859_1);
//        // 3.2 位元組陣列解碼
//        username = new String(bytes, StandardCharsets.UTF_8);

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

        System.out.println("解決亂碼後"+username);


    }
}

request請求轉發

請求轉發（forward）：一種在伺服器內部的資源跳轉方式。
請求轉發特點：

  1. 瀏覽器位址列路徑不發生變化
  2. 只能轉發到當前伺服器的內部資源
  3. 一次請求，可以在轉發的資源間使用request共享資料
    req4
package com.itheijma.web;



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;


/**
 * 請求轉發
 */
@WebServlet("/req4")
public class RequestDemo4 extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        this.doGet(request, response);
    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        System.out.println("demo4");

        //儲存資料
        request.setAttribute("msg","hello");

        //請求轉發
        request.getRequestDispatcher("/req5").forward(request,response);
    }
}

req5

package com.itheijma.web;

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("/req5")
public class RequestDemo5 extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        this.doGet(request, response);
    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        System.out.println("demo5");

        //獲取資料
        Object msg = request.getAttribute("msg");
        System.out.println(msg);
    }
}

response

Response完成重定向

重定向：一種資源跳轉的方式
resp1

package com.itheima.web.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("/resp1")
public class ResponseDemo1 extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        this.doGet(request, response);
    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        System.out.println("resp1...");

//        // 重定向
//        // 1. 設定狀態碼 302
//        response.setStatus(302);
//        // 2. 設定響應頭 Location
//        response.setHeader("Location","/tomcat-demo2/resp2");

        // 簡化方式完成重定向
        response.sendRedirect("/tomcat-demo2/resp2");

    }
}

resp2

package com.itheima.web.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("/resp2")
public class ResponseDemo2 extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        this.doGet(request, response);
    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        System.out.println("resp2...");
    }
}

重定向特點：

  1. 瀏覽器位址列路徑發生變化
  2. 可以重定向到任意位置的資源（伺服器內、外部均可）
  3. 兩次請求，不能在多個資源使用request共享資料

資源路徑問題（什麼時候加虛擬目錄）
瀏覽器使用：需要加虛擬目錄
服務端使用：不需要加虛擬目錄

動態獲取虛擬目錄

        //動態獲取虛擬目錄
        String contextPath = request.getContextPath();
        response.sendRedirect(contextPath + "/resp2");

Response響應字元資料

package com.itheima.web.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;


/**
 * 響應字元資料：設定字元資料的響應體
 */
@WebServlet("/resp3")
public class ResponseDemo3 extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        this.doGet(request, response);
    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        response.setContentType("text/html;charset=utf-8");
        //獲取字元輸出流
        PrintWriter writer = response.getWriter();
        //content-type
        //response.setHeader("content-type","text/html");
        writer.write("你好");
        writer.write("<h1>aaa</h1>");

        //細節：流不需要關閉
    }
}

Response響應位元組資料

package com.itheima.web.response;

import org.apache.commons.io.IOUtils;

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.FileInputStream;
import java.io.IOException;
import java.io.PrintWriter;


/**
 * 響應位元組資料：設定位元組資料的響應體
 */
@WebServlet("/resp4")
public class ResponseDemo4 extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        this.doGet(request, response);
    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

        // 1. 讀取檔案
        FileInputStream fis = new FileInputStream("e://a.jpg");

        // 2. 獲取response位元組輸出流
        ServletOutputStream os = response.getOutputStream();

        // 3. 完成流的copy

//        byte[] buff = new byte[1024];
//        int len = 0;
//        while ((len = fis.read(buff)) != -1){
//            os.write(buff,0,len);
//        }
        IOUtils.copy(fis,os);//使用工具類

        fis.close();
    }
}

pom檔案匯入工具類

<dependency>
            <groupId>commons-io</groupId>
            <artifactId>commons-io</artifactId>
            <version>2.6</version>
        </dependency>

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