Java-Response對象設置響應消息

功能：設置響應消息

1.設置響應行

1. 格式：HTTP/1.1 200 OK
2. 設置狀態碼：setStatus(int sc)

2.設置響應頭：setHeader(String name,String value)

3.設置響應體:

• 使用步驟：
  1. 獲取輸出流
     • 字符輸入流：PrintWirter getWriter()
     • 字節輸出流：ServletOutputStream getOutputStream()
  2. 使用輸出流，將數據輸出到客戶端瀏覽器（核心）

案例

1.完成重定向

• 重定向：資源跳轉的方式
• 代碼實現：
  //訪問/ResponseDemo1，會自動跳轉到/ResponseDemo2資源
  // //1.設置狀態碼為302
  // response.setStatus(302);
  // //2.設置響應頭location
  // response.setHeader("location", "/07_Response_war_exploded/ResponseDemo2");
  // 簡單的重定向
  response.sendRedirect("/07_Response_war_exploded/ResponseDemo2");
• 重定向的特點：redirect
  1. 地址欄發生變化
  2. 重定向可以訪問其他站點（服務器）的資源
  3. 重定向是兩次請求，不可以使用request對象來共享數據
• 轉發的特點：forward
  1. 轉發地址欄路徑不變
  2. 轉發只能訪問當前服務器下的資源
  3. 轉發是一次請求，可以使用request對象來共享數據
• forward和redirect區別
• 路徑寫法
  1. 相對路徑：通過相對路徑不確定唯一資源
     • 規則：找到當前資源與目標資源之間的相對位置關系
       • ./：當前目錄
       • ../：后退一級目錄
  2. 絕對路徑
     • 規則：判斷定義的路徑是給誰用的？判斷請求將來從哪發出
       • 給客戶端瀏覽器使用：需要加虛擬目錄
         • 建議虛擬目錄動態獲取：request.getContextPath()
         • ,
           ,重定向....
       • 給服務器使用：不需要加虛擬目錄

代碼如下

package cn.itcast.web.servlet;

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("/ResponseDemo1")
public class ResponseDemo1 extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        System.out.println("demo1111................");
        //訪問/ResponseDemo1，會自動跳轉到/ResponseDemo2資源
        // //1.設置狀態碼為302
        // response.setStatus(302);
        // //2.設置響應頭location
        // response.setHeader("location", "/07_Response_war_exploded/ResponseDemo2");
        //    簡單的重定向
        response.sendRedirect("/07_Response_war_exploded/ResponseDemo2");
    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        this.doPost(request, response);
    }
}
----------------------------------------------------------------
package cn.itcast.web.servlet;

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("/ResponseDemo2")
public class ResponseDemo2 extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        System.out.println("demo2222................");
    }

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

2.服務器輸出字符數據到瀏覽器

• 步驟
  1. 獲取字符輸出流
  2. 輸出數據
• 亂碼問題：
  • 簡單形式//告訴瀏覽器，服務器發送的消息體數據的編碼，建議瀏覽器使用該編碼解碼
  • response.setHeader("content-type", "text/html;charset=utf-8");

代碼如下

package cn.itcast.web.servlet;

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("/ResponseDemo4")
public class ResponseDemo4 extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //獲取流對象之前，設置流的默認編碼：ISO-8859-1 設置為：GBK
        response.setCharacterEncoding("utf-8");
        //告訴瀏覽器，服務器發送的消息體數據的編碼，建議瀏覽器使用該編碼解碼
        response.setHeader("content-type", "text/html;charset=utf-8");
        //1.獲取字符輸出流
        PrintWriter pw = response.getWriter();
        //2.輸出數據
        // pw.write("<h1>hello response</h1>");
        pw.write("<h1>你好 response</h1>");
        System.out.println("demo444................");
    }

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

3.服務器輸出字節數據到瀏覽器

• 步驟 獲取字節輸出流，輸出數據

代碼如下

package cn.itcast.web.servlet;

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;

@WebServlet("/ResponseDemo5")
public class ResponseDemo5 extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        response.setHeader("content-type", "text/html;charset=utf-8");
        //1.獲取字節輸出流
        ServletOutputStream sos = response.getOutputStream();
        //2.輸出數據
        // sos.write("hello".getBytes());
        sos.write("你好".getBytes("utf-8"));
    }

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

4.驗證碼

• 本質：圖片
• 目的：防止惡意表單注冊

代碼如下

package cn.itcast.web.servlet;

import javax.imageio.ImageIO;
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.awt.*;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.util.Random;

@WebServlet("/CheckCodeServlet")
public class CheckCodeServlet extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        int width = 100;
        int height = 50;
        //創建一對象，在內存中圖片（驗證碼圖片對象）
        BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);
        //美化圖片
        //2.1.填充背景色
        Graphics g = image.getGraphics();//畫筆對象
        g.setColor(Color.pink);//設置畫筆顏色
        g.fillRect(0, 0, width, height);
        //2.2.畫邊框
        g.setColor(Color.BLUE);
        g.drawRect(0, 0, width - 1, height - 1);

        String str = "ABCDEFGHIJKLMNOPQRSTOVWXYZabcdefghijklmnopqrstovwxyz";
        //生成隨機角標
        Random ran = new Random();
        for (int i = 1; i <= 4; i++) {
            int index = ran.nextInt(str.length());
            //獲取字符
            char ch = str.charAt(index);//隨機字符
            g.drawString(ch + "", width / 5 * i, height / 2);
            //2.3.寫驗證碼
        }
        //2.4畫干擾線
        g.setColor(Color.GREEN);
        for (int i = 0; i <= 4; i++) {
            int x1 = ran.nextInt(width);
            int x2 = ran.nextInt(width);
            int y1 = ran.nextInt(height);
            int y2 = ran.nextInt(height);
            g.drawLine(x1, x1, x2, y2);
        }

        //將圖片輸出到頁面顯示
        ImageIO.write(image, "jpg", response.getOutputStream());
    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        this.doPost(request, response);
    }
}
--------------------------------------------------------------------------
<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <script>
        window.onload = function () {
            var img = document.getElementById("checkCode");
            img.onclick = function () {
                //加時間戳
                var date = new Date().getTime();
                img.src = "/07_Response_war_exploded/CheckCodeServlet?" + date;
            }
        }
    </script>
</head>
<body>
<img src="/07_Response_war_exploded/CheckCodeServlet"/>
<a id="checkCode" href="">看不清換一張</a>
</body>
</html>

5.獲取ServletContext

• ServletContext getServletContext()

5.1 代碼如下

package cn.itcast.web.request;

import javax.servlet.ServletContext;
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("/RequestDemo10")
public class RequestDemo10 extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //    獲取數據
        ServletContext servletContext = request.getServletContext();
        System.out.println(servletContext);
        System.out.println("demo1010被訪問了.....");

    }


    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //    get 獲取請求參數
        // String username = request.getParameter("username");
        // System.out.println("get");
        // System.out.println(username);
        this.doPost(request, response);
    }
}

5.2 概念：代表整個web應用，可以和程序的容器（服務器）來通信

5.3 獲取MINE類型

    * MIME類型：在互聯網通信過程中定義的一種文件數據類型
        * 格式 大類型/小類型 text/html image/jepg
    * 獲取：String getMimeType(String file)

代碼如下

package cn.itcast.web.servletcontext;

import javax.servlet.ServletContext;
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("/ServletContextDemo2")
public class ServletContextDemo2 extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
/*
1.獲取MINE類型
* MIME類型：在互聯網通信過程中定義的一種文件數據類型
    * 格式 大類型/小類型 text/html image/jepg
* 獲取：String getMimeType(String file)
*/

        // 2.通過HttpServlet獲取
        ServletContext context2 = this.getServletContext();
        //定義文件名稱
        String filename = "a.jpg";//image/jpeg
        //獲取MIME類型1
        String mimeType = context2.getMimeType(filename);
        System.out.println(mimeType);
    }

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

5.4 域對象：共享數據

    1. setAttribute(String name,Object value)
    2. getAttribute(String name)
    3. removeAttribute(String name)
    * ServletContext對象范圍：所有用戶所有請求的數據

代碼如下

package cn.itcast.web.servletcontext;

import javax.servlet.ServletContext;
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("/ServletContextDemo3")
public class ServletContextDemo3 extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // 2.通過HttpServlet獲取
        ServletContext context = this.getServletContext();
        //設置數據
        context.setAttribute("msg", "haha");
    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        this.doPost(request, response);
    }
}
---------------------------------------------------------------
package cn.itcast.web.servletcontext;

import javax.servlet.ServletContext;
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("/ServletContextDemo4")
public class ServletContextDemo4 extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // 2.通過HttpServlet獲取
        ServletContext context = this.getServletContext();
        //設置數據
        Object msg = context.getAttribute("msg");
        System.out.println(msg);
    }

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

5.5 獲取文件的真實（服務器）路徑

    1. 方法：String getRealPath(String path)

代碼如下

package cn.itcast.web.servletcontext;

import javax.servlet.ServletContext;
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.File;
import java.io.IOException;

@WebServlet("/ServletContextDemo5")
public class ServletContextDemo5 extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // 2.通過HttpServlet獲取
        ServletContext context = this.getServletContext();
        //獲取文件的服務器路徑
        String realPath = context.getRealPath("/b.txt");
        System.out.println(realPath);
        File file = new File(realPath);
        String c = context.getRealPath("/WEB-INF/c.txt");
        System.out.println(c);
        String a = context.getRealPath("/WEB-INF/classes/a.txt");
        System.out.println(a);
    }

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

5.4 獲取：

1. 通過request對象獲取
    request.getServletContext()
2. 通過HttpServlet獲取
    this.getServletContext();

代碼如下

package cn.itcast.web.servletcontext;

import javax.servlet.ServletContext;
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("/ServletContextDemo1")
public class ServletContextDemo1 extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        /**
        ServletContext對象獲取
        1.通過request對象獲取
        request.getServletContext()
        2.通過HttpServlet獲取
        this.getServletContext();
        */
        // 1.通過request對象獲取
        ServletContext context1 = request.getServletContext();
        // 2.通過HttpServlet獲取
        ServletContext context2 = this.getServletContext();
        System.out.println(context1);
        System.out.println(context2);
        System.out.println(context1 == context2);
    }

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