HttpServletResponce
Web服務器接收到客戶端的Http請求,針對這個請求,分別創建一個代表請求的HttpServletRequset對象,以及一個代表響應的HttpServletResponse對象。
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如果要獲取客戶端請求過來的參數:找HttpServletRequset
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如果要給客戶端響應一些信息:找HttpServletResponse
簡單分類:
1.向瀏覽器發送數據的方法
ServletOutputStream getOutputStream() throws IOException;
//平常的流
PrintWriter getWriter() throws IOException;
//中文使用
2.負責向瀏覽器發送響應頭的方法
void setCharacterEncoding(String var1);
void setContentLength(int var1);
void setContentLengthLong(long var1);
void setContentType(String var1);
void setDateHeader(String var1, long var2);
void addDateHeader(String var1, long var2);
void setHeader(String var1, String var2);
void addHeader(String var1, String var2);
void setIntHeader(String var1, int var2);
……
3.響應的狀態碼
int SC_CONTINUE = 100;
int SC_SWITCHING_PROTOCOLS = 101;
int SC_OK = 200;
int SC_CREATED = 201;
int SC_ACCEPTED = 202;
int SC_NON_AUTHORITATIVE_INFORMATION = 203;
int SC_NO_CONTENT = 204;
int SC_RESET_CONTENT = 205;
int SC_PARTIAL_CONTENT = 206;
int SC_MULTIPLE_CHOICES = 300;
int SC_MOVED_PERMANENTLY = 301;
int SC_MOVED_TEMPORARILY = 302;
int SC_FOUND = 302;
int SC_SEE_OTHER = 303;
int SC_NOT_MODIFIED = 304;
int SC_USE_PROXY = 305;
int SC_TEMPORARY_REDIRECT = 307;
int SC_BAD_REQUEST = 400;
int SC_UNAUTHORIZED = 401;
int SC_PAYMENT_REQUIRED = 402;
int SC_FORBIDDEN = 403;
int SC_NOT_FOUND = 404;
int SC_METHOD_NOT_ALLOWED = 405;
int SC_NOT_ACCEPTABLE = 406;
int SC_PROXY_AUTHENTICATION_REQUIRED = 407;
int SC_REQUEST_TIMEOUT = 408;
int SC_CONFLICT = 409;
int SC_GONE = 410;
int SC_LENGTH_REQUIRED = 411;
int SC_PRECONDITION_FAILED = 412;
int SC_REQUEST_ENTITY_TOO_LARGE = 413;
int SC_REQUEST_URI_TOO_LONG = 414;
int SC_UNSUPPORTED_MEDIA_TYPE = 415;
int SC_REQUESTED_RANGE_NOT_SATISFIABLE = 416;
int SC_EXPECTATION_FAILED = 417;
int SC_INTERNAL_SERVER_ERROR = 500;
int SC_NOT_IMPLEMENTED = 501;
int SC_BAD_GATEWAY = 502;
int SC_SERVICE_UNAVAILABLE = 503;
int SC_GATEWAY_TIMEOUT = 504;
int SC_HTTP_VERSION_NOT_SUPPORTED = 505;
常見應用:
2.下載文件
1.要獲取下載文件的路徑
2.獲取下載的文件名
3.設置,想辦法讓瀏覽器能夠支持下載我們需要的東西
4.獲取下載文件的輸入流
5.創建緩衝區
6.獲取OutputStream對象
7.將FileOutputStream流寫入到buffer緩衝區
8.使用OutputStream將緩衝區中的數據輸出到客戶端
package com.edwin.servlet;
import javax.servlet.ServletException;
import javax.servlet.ServletOutputStream;
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.net.URLEncoder;
/**
* @author Edwin D
* @date 2020.6.3 下午 9:22
*/
public class KuangFileServlet extends HttpServlet {
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
// 1. 要獲取下載文件的路徑
String realPath = "E:\\Java\\Self\\JavaWeb\\javaweb-02-servlet\\response\\src\\main\\webapp\\resource\\1.jpg";
System.out.println("下載文件的路徑:"+realPath);
// 2. 下載的文件名是啥?
String fileName = realPath.substring(realPath.lastIndexOf("\\") + 1);
// 3. 設置想辦法讓瀏覽器能夠支持(Content-Disposition)下載我們需要的東西,中文文件名URLEncoder.encode編碼,否則有可能亂碼
resp.setHeader("Content-Disposition","attachment;filename="+ URLEncoder.encode(fileName,"UTF-8"));
// 4. 獲取下載文件的輸入流
FileInputStream in = new FileInputStream(realPath);
// 5. 創建緩衝區
int len = 0;
byte[] buffer = new byte[1024];
// 6. 獲取OutputStream對象
ServletOutputStream out = resp.getOutputStream();
// 7. 將FileOutputStream流寫入到buffer緩衝區,使用OutputStream將緩衝區中的數據輸出到客戶端!
while ((len=in.read(buffer))>0){
out.write(buffer,0,len);
}
in.close();
out.close();
}
@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
doGet(req, resp);
}
}
另外一個版本:
package com.edwin.servlet;
import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.ServletOutputStream;
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.InputStream;
/**
* @author Edwin D
* @date 2020.6.3 下午 4:54
*/
public class FileServlet extends HttpServlet {
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
// 1.要獲取下載文件的路徑
// String realPath = "/static/png/1.jpg";
// System.out.println("獲取到的下載文件的路徑:"+realPath);
ServletContext ctx = this.getServletContext();
// 2.獲取下載的文件名
// String fileName = realPath.substring(realPath.lastIndexOf("/") + 1);
// System.out.println(fileName);
// 3.設置,想辦法讓瀏覽器能夠支持下載我們需要的東西
resp.setHeader("content-type", "application/jpg");
resp.addHeader("content-disposition", "attachment;filename=1.jpg");
// 4.獲取下載文件的輸入流
InputStream in = ctx.getResourceAsStream("/resource/1.jpg");
System.out.println(in);
// 5.創建緩衝區
int len = 0;
byte[] buffer = new byte[1024];
// 6.獲取OutputStream對象
ServletOutputStream out = resp.getOutputStream();
// 7.將FileOutputStream流寫入到buffer緩衝區,使用OutputStream將緩衝區中的數據輸出到客戶端
while ((len = in.read(buffer))>0) {
out.write(buffer,0,len);
}
// 8.關閉流
in.close();
out.close();
}
@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
doGet(req, resp);
}
}
xml:
<servlet>
<servlet-name>Down</servlet-name>
<servlet-class>com.edwin.servlet.FileServlet</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>Down</servlet-name>
<url-pattern>/Down</url-pattern>
</servlet-mapping>
輸出效果:
圖:
3.驗證碼功能
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前端實現。
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後端實現,需要用到Java圖片類,生成一個圖片。
package com.edwin.servlet;
import javax.imageio.ImageIO;
import javax.servlet.ServletException;
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;
/**
* @author Edwin D
* @date 2020.6.3 下午 9:42
*/
public class ImageServlet extends HttpServlet {
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
// 如何讓瀏覽器3秒鐘刷新一次。
// resp.setHeader("refresh", "3");
// 在內存中創建一個圖片
BufferedImage Image = new BufferedImage(80, 20, BufferedImage.TYPE_INT_RGB);
// 得到圖片
Graphics2D g = (Graphics2D) Image.getGraphics();//類比畫筆,進行2D繪畫。
// 設置圖片背景色
g.setColor(Color.WHITE);
g.fillRect(0, 0, 80, 20);
// 給圖片寫數據
g.setColor(Color.BLUE);
g.setFont(new Font(null, Font.BOLD, 20));
String c = makeNum();
g.drawString(c, 0, 20);
System.out.println(c);
// 告訴瀏覽器,這個請求用圖片的方式打開
resp.setContentType("image/jpg");
// 網站存在緩存,不讓瀏覽器緩存
resp.setDateHeader("expires", -1);
resp.setHeader("Cache-Control", "no-cache");
resp.setHeader("Pragma", "no-cache");
// 把圖片寫給瀏覽器
ImageIO.write(Image, "jpg", resp.getOutputStream());
}
@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
doGet(req, resp);
}
// 生成隨機數
public String makeNum() {
Random random = new Random();
String num = random.nextInt(9999999) + "";
// 生成一個8位數的驗證數字(有8個9)。
StringBuffer sb = new StringBuffer();
for (int i = 0; i < 7-num.length(); i++) {
sb.append("0");
}
// 用8-num.length(),得到的結果爲0(生成數爲8位)到8(生成了8個0)
// 這樣的話,就保證不論如何都會生成8位數的隨機數。不夠8位,可以用“0”來填充剩下的尾數(如果不夠8位的隨機數)
num = sb.toString() + num;
return num;
}
}
XML:
<servlet>
<servlet-name>Image</servlet-name>
<servlet-class>com.edwin.servlet.ImageServlet</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>Image</servlet-name>
<url-pattern>/Image</url-pattern>
</servlet-mapping>
輸出效果:
後臺檢驗:
參考文獻
《【狂神說Java】JavaWeb入門到實戰》
2020.06.04