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JavaWeb 入门篇（4）HttpResponse 详解 HttpRequest 详解

發布時間：2025/3/19 java 29 豆豆

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HttpResponse 講解

HttpServletResponse概述:

? 在創建Servlet時會覆蓋service()方法，或doGet()/doPost(),這些方法都有兩個參數，一個為代表請求的request和代表響應response。service方法中的response的類型是ServletResponse，而doGet/doPost方法的response的類型是HttpServletResponse，HttpServletResponse是ServletResponse的子接口，功能和方法更加強大。

Response運行流程

響應頭有很多這里只介紹常用的。

在瀏覽器可以按F12 抓包看響應頭、請求頭、具體的可以再查。

設置響應行

設置響應的狀態碼

/*** @Author: crush* @Date: 2021-05-09 19:35* version 1.0*/ @WebServlet("/test3") public class HttpResponseTest3 extends HttpServlet {@Overrideprotected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {System.out.println("設置狀態碼,前臺通過判斷狀態碼，來判斷請求是否成功");resp.setStatus(404);}@Overrideprotected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {doGet(req, resp);} }

測試

設置響應頭

刷新跳轉頁面

/*** @Author: crush* @Date: 2021-05-09 19:35* version 1.0*/ @WebServlet("/test4") public class HttpResponseTest4 extends HttpServlet {@Overrideprotected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {// 設置響應頭每1秒自動刷新System.out.println("設置響應頭每1秒自動刷新");resp.setHeader("Refresh", "1");//定時跳轉 3秒后將自動跳轉 // resp.setHeader("Refresh","3;URL=hello.jsp");}@Overrideprotected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {doGet(req, resp);} }

測試

一個小demo 實現刷新頁面累加

/*** response* @author Adimi*/ @WebServlet("/test4") public class ResponseTest4 extends HttpServlet {private static Integer id=1;@Overrideprotected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {response.setHeader("Refresh","1");PrintWriter writer = response.getWriter();id++;writer.print("id==>"+id);}@Overrideprotected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {doGet(req, resp);} }

設置字符編碼解決中文亂碼問題

/*** @Author: crush* @Date: 2021-05-09 19:35* version 1.0*/ @WebServlet("/test1") public class HttpResponseTest1 extends HttpServlet {@Overrideprotected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {// 解決中文亂碼問題// 設置響應頭// 設置字符編碼 resp.setCharacterEncoding("UTF-8");// 設置響應內容以什么格式展示到頁面什么編碼格式包含了設置字符編碼resp.setContentType("text/html;charset=utf-8");PrintWriter writer = resp.getWriter();writer.print("中國,你好！！！");}@Overrideprotected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {doGet(req, resp);} }

測試

重定向 redirect

/*** 重定向* @Author: crush* @Date: 2021-05-09 19:35* version 1.0*/ @WebServlet("/test5") public class HttpResponseTest5 extends HttpServlet {@Overrideprotected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {resp.sendRedirect("hello.jsp"); // resp.setHeader("location","www.baidu.com"); 通過設置響應頭轉發}@Overrideprotected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {doGet(req, resp);} }

request轉發

/*** 重定向* @Author: crush* @Date: 2021-05-09 19:35* version 1.0*/ @WebServlet("/test5") public class HttpResponseTest5 extends HttpServlet {@Overrideprotected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { // resp.sendRedirect("hello.jsp");req.getRequestDispatcher("hello.jsp").forward(req,resp);}@Overrideprotected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {doGet(req, resp);} }

重定向和轉發的區別

文件下載

獲取路徑資源

String path=this.getServletContext().getRealPath("WEB-INF\\classes\\8.jpg");

讀取資源

FileInputStream fileInputStream=new FileInputStream(path);

獲取到文件名，路徑在電腦上保存的形式是 \ \

String fileName=path.substring(path.lastIndexOf("\\")+1);

設置消息頭告訴瀏覽器，我要下載1.png這個圖片設置編碼

resp.setHeader("Content-Disposition", "attachment; filename=" + URLEncoder.encode(fileName, "UTF-8"));

把讀取到的內容回送給瀏覽器

int len=0; byte[] bytes=new byte[1024]; // ServletOutputStream 提供用于將二進制數據發送到客戶端的輸出流 ServletOutputStream servletOutputStream=resp.getOutputStream(); while((len=fileInputStream.read(bytes))>0) {servletOutputStream.write(bytes,0,len); }

關閉資源

servletOutputStream.close();fileInputStream.close();

注：8.jpg 放在我的resources 文件夾下但是這里需要寫的是編譯完8.jpg存放的位置

具體代碼

/*** @Author: crush* @Date: 2021-05-09 19:40* version 1.0*/ @WebServlet("/down") public class ResponseDownFile extends HttpServlet {@Overrideprotected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {//獲取路徑資源String path=this.getServletContext().getRealPath("WEB-INF\\classes\\8.jpg");//讀取資源FileInputStream fileInputStream=new FileInputStream(path);//獲取到文件名，路徑在電腦上保存的形式是\\String fileName=path.substring(path.lastIndexOf("\\")+1);//設置消息頭告訴瀏覽器，我要下載1.png這個圖片// 該方式文件名為中文時會亂碼//防止中文亂碼resp.setHeader("Content-Disposition", "attachment; filename=" + URLEncoder.encode(fileName, "UTF-8"));//把讀取到的內容回送給瀏覽器int len=0;byte[] bytes=new byte[1024];ServletOutputStream servletOutputStream=resp.getOutputStream();while((len=fileInputStream.read(bytes))>0) {servletOutputStream.write(bytes,0,len);}// 關閉資源servletOutputStream.close();fileInputStream.close();}@Overrideprotected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {doGet(req, resp);} }

HttpRequest 講解

HttpServletRequest概述

? 我們在創建Servlet時會覆蓋service()方法，或doGet()/doPost(),這些方法都有兩個參數，一個為代表請求的request和代表響應response。service（）方法中寫了根據請求方式的不同調用doget()和dopost().

service方法中的request的類型是ServletRequest，而doGet/doPost方法的request類型HttpServletRequest，HttpServletRequest是ServletRequest的子接口，功能和方法更加強大.

Request 運行流程

獲取請求攜帶的參數

/*** @Author: crush* @Date: 2021-05-11 16:52* version 1.0*/ @WebServlet("/request1") public class RequestTest1 extends HttpServlet {@Overrideprotected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {// 這里是請求的參數名必須是同名的 String username = req.getParameter("username"); String password = req.getParameter("password");PrintWriter writer = resp.getWriter();writer.print("<h1>"+username+":"+password+"</h1>");}@Overrideprotected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {doGet(req, resp);} }

獲取多個參數的值

@Overrideprotected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {// 設置請求的編碼不然會亂碼req.setCharacterEncoding("utf-8");Enumeration<String> names = req.getParameterNames();while (names.hasMoreElements()) {String name = (String) names.nextElement();String[] values = req.getParameterValues(name);System.out.println(name+":"+ Arrays.toString(values));}}

獲得請求行的信息

/*** @Author: crush* @Date: 2021-05-11 16:52* version 1.0*/ @WebServlet("/request3") public class RequestTest3 extends HttpServlet {@Overrideprotected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {// 獲得請求的urlStringBuffer requestURL = req.getRequestURL();System.out.println("請求的URL===>"+requestURL);// 獲得請求的Servlet的路徑String path = req.getServletPath();System.out.println("請求的Servlet的路徑===>"+path);//返回發出此請求的HTTP方法的名稱，例如GET，POST或PUTString method = req.getMethod();System.out.println("返回發出此請求的HTTP方法的名稱==>"+method);//返回發送請求的客戶端或最后一個代理的Internet協議（IP）地址String remoteAddr = req.getRemoteAddr();System.out.println("remoteAddr==>"+remoteAddr);}@Overrideprotected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {doGet(req, resp);} }

request實現轉發

/*** @Author: crush* @Date: 2021-05-11 16:52* version 1.0*/ @WebServlet("/request2") public class RequestTest2 extends HttpServlet {@Overrideprotected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {// 訪問request2 轉發到 request4去req.getRequestDispatcher("/request4").forward(req,resp);}@Overrideprotected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {doGet(req, resp);} }

request是一個域對象

request對象也是一個存儲數據的區域對象，所以也具有如下方法：

setAttribute(String name, Object o)

getAttribute(String name)

removeAttribute(String name)

ServletContext 作用域：

創建：啟動web應用程序的時候創建

銷毀：關閉web應用程序的時候銷毀

域的作用范圍：整個web應用的啟動周期

request作用域：

創建：訪問時創建request

銷毀：響應結束request銷毀

域的作用范圍：一次請求中

自言自語

努力生活、加油學習。

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