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JavaWeb入門:HttpResponse和HttpRequest詳解

 更新時間：2021年07月16日 16:35:18   作者：寧在春  
這篇文章主要介紹了Django的HttpRequest和HttpResponse對象，分享了相關(guān)代碼示例，小編覺得還是挺不錯的，具有一定借鑒價值，需要的朋友可以參考下

HttpResponse 講解

HttpServletResponse概述:

​ 在創(chuàng)建Servlet時會覆蓋service()方法，或doGet()/doPost(),這些方法都有兩個參數(shù)，一個為代表請求的request和代表響應(yīng)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(qiáng)大。

Response運(yùn)行流程

img

響應(yīng)頭有很多這里只介紹常用的。

[外鏈圖片轉(zhuǎn)存失敗,源站可能有防盜鏈機(jī)制,建議將圖片保存下來直接上傳(img-bAvaDBGw-1620739367741)(C:\Users\ASUS\Desktop\JavaWeb_study\JavaWeb\JavaWeb.assets\image-20210511163256716.png)]

在瀏覽器可以按F12 抓包看響應(yīng)頭、請求頭、具體的可以再查。

設(shè)置響應(yīng)行

設(shè)置響應(yīng)的狀態(tài)碼

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

測試

在這里插入圖片描述

設(shè)置響應(yīng)頭

刷新 跳轉(zhuǎn)頁面

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

測試

[外鏈圖片轉(zhuǎn)存失敗,源站可能有防盜鏈機(jī)制,建議將圖片保存下來直接上傳(img-LGJQhKor-1620739367743)(C:\Users\ASUS\Desktop\JavaWeb_study\JavaWeb\JavaWeb.assets\image-20210511162434487.png)]

一個小demo 實(shí)現(xiàn)刷新 頁面累加

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

設(shè)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 {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        // 解決中文亂碼問題
        // 設(shè)置響應(yīng)頭
        // 設(shè)置字符編碼 resp.setCharacterEncoding("UTF-8");
        // 設(shè)置響應(yīng)內(nèi)容以什么格式展示到頁面 什么編碼格式 包含了設(shè)置字符編碼
        resp.setContentType("text/html;charset=utf-8");
        PrintWriter writer = resp.getWriter();
        writer.print("中國,你好！??！");
    }
    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        doGet(req, resp);
    }
}

測試

[外鏈圖片轉(zhuǎn)存失敗,源站可能有防盜鏈機(jī)制,建議將圖片保存下來直接上傳(img-5VCR2LeF-1620739367746)(C:\Users\ASUS\Desktop\JavaWeb_study\JavaWeb\JavaWeb.assets\image-20210511162823603.png)]

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 {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        resp.sendRedirect("hello.jsp");
//        resp.setHeader("location","www.baidu.com"); 通過設(shè)置響應(yīng)頭轉(zhuǎn)發(fā)
    }
    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        doGet(req, resp);
    }
}

request轉(zhuǎn)發(fā)

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

重定向和轉(zhuǎn)發(fā)的區(qū)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(shè)置消息頭告訴瀏覽器，我要下載1.png這個圖片 設(shè)置編碼

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

把讀取到的內(nèi)容回送給瀏覽器

 int len=0;
byte[] bytes=new byte[1024];
// ServletOutputStream 提供用于將二進(jìn)制數(shù)據(jù)發(fā)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(guān)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 {
    @Override
    protected 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(shè)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(nèi)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(guān)閉資源
        servletOutputStream.close();
        fileInputStream.close();
    }
    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        doGet(req, resp);
    }
}

HttpRequest 講解

HttpServletRequest概述

​ 我們在創(chuàng)建Servlet時會覆蓋service()方法，或doGet()/doPost(),這些方法都有兩個參數(shù)，一個為代表請求的request和代表響應(yīng)response。service（）方法中寫了根據(jù)請求方式的不同調(diào)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(qiáng)大.

Request 運(yùn)行流程

img

獲取請求攜帶的參數(shù)

/**
 * @Author: crush
 * @Date: 2021-05-11 16:52
 * version 1.0
 */
@WebServlet("/request1")
public class RequestTest1 extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        // 這里是請求的參數(shù)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>");
    }
    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        doGet(req, resp);
    }
}

[外鏈圖片轉(zhuǎn)存失敗,源站可能有防盜鏈機(jī)制,建議將圖片保存下來直接上傳(img-2zxGslkb-1620739367750)(C:\Users\ASUS\Desktop\JavaWeb_study\JavaWeb\JavaWeb.assets\image-20210511170056042.png)]

獲取多個參數(shù)的值

  @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        // 設(shè)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 {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        // 獲得請求的url
        StringBuffer 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(fā)出此請求的HTTP方法的名稱，例如GET，POST或PUT
        String method = req.getMethod();
        System.out.println("返回發(fā)出此請求的HTTP方法的名稱==>"+method);
        //返回發(fā)送請求的客戶端或最后一個代理的Internet協(xié)議（IP）地址
        String remoteAddr = req.getRemoteAddr();
        System.out.println("remoteAddr==>"+remoteAddr);
    }
    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        doGet(req, resp);
    }
}

request實(shí)現(xiàn)轉(zhuǎn)發(fā)

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

request是一個域?qū)ο?/h3>

request對象也是一個存儲數(shù)據(jù)的區(qū)域?qū)ο?，所以也具有如下方法?/p>

setAttribute(String name, Object o)

getAttribute(String name)

removeAttribute(String name)

ServletContext 作用域：

創(chuàng)建：啟動web應(yīng)用程序的時候創(chuàng)建

銷毀：關(guān)閉web應(yīng)用程序的時候銷毀

域的作用范圍：整個web應(yīng)用的啟動周期

request作用域：

創(chuàng)建：訪問時創(chuàng)建request

銷毀：響應(yīng)結(jié)束request銷毀

域的作用范圍：一次請求中

總結(jié)

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