request 对象和 response 对象

Web服务器收到客户端的http请求，会针对每一次请求，分别创建一个用于代表请求的request对象、和代表响应的response对象

HttpServletResponse

HttpServletResponse对象代表服务器的响应。这个对象中封装了向客户端发送数据、发送响应头，发送响应状态码的方法。

1.向客户端输出中文数据（字节）

package cn.lsl.response;
import java.io.IOException;
import javax.servlet.ServletException; import javax.servlet.ServletOutputStream; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; public class ResponseDemo1 extends HttpServlet { public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { test5(response); } //输出整数：最好转换成字符串输出 private void test5(HttpServletResponse response) throws IOException{ int i = 98; response.getOutputStream().write((i+"").getBytes()); } //以字节流用默认编码向客户端输出中文数据：没有乱码 //默认的是GBK private void test1(HttpServletResponse response) throws IOException{ String s = "你好！一"; ServletOutputStream out = response.getOutputStream(); out.write(s.getBytes()); } //以字节流用utf-8编码向客户端输出中文数据 //以UTF-8编码发送数据，浏览器(默认用GB2312)会出现乱码 private void test2(HttpServletResponse response) throws IOException{ String s = "你好！二"; //通知客户端查看UTF-8码表 response.setHeader("Content-Type", "text/html;charset=UTF-8"); ServletOutputStream out = response.getOutputStream(); out.write(s.getBytes("UTF-8")); } //以字节流用utf-8编码向客户端输出中文数据 private void test3(HttpServletResponse response) throws IOException{ String s = "你好！三"; ServletOutputStream out = response.getOutputStream(); out.write("<meta http-equiv='Content-Type' content='text/html;charset=UTF-8'>".getBytes("UTF-8")); out.write(s.getBytes("UTF-8")); } //以字节流用utf-8编码向客户端输出中文数据 private void test4(HttpServletResponse response) throws IOException{ String s = "你好！四"; response.setContentType("text/html;charset=UTF-8"); ServletOutputStream out = response.getOutputStream(); out.write(s.getBytes("UTF-8")); } public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { doGet(request,response); } }

分析：出现乱码的图解

解决办法：

1)通过更改浏览器的编码方式：IE/”查看”/”编码”/”UTF-8”(不可取)

2)通过设置响应头告知客户端编码方式：response.setHeader(“Content-type”, “text/html;charset=UTF-8”);//告知浏览器数据类型及编码

3)通过meta标签模拟请求头:out.write("<meta http-equiv='Content-Type' content='text/html; charset=utf-8' />".getBytes());

4)通过以下方法：response.setContentType("text/html;charset=UTF-8");

2.向客户端输出中文数据（字符）

package cn.lsl.response;import java.io.IOException;
import java.io.PrintWriter; import javax.servlet.ServletException; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; public class ResponseDemo2 extends HttpServlet { public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { test3(response); } //字符流输出中文数据 private void test1(HttpServletResponse response) throws IOException{ String s = "你好！一"; response.setCharacterEncoding("UTF-8"); //设置查的UTF-8（对内容进行编码，查utf-8） response.setHeader("Content-Type", "text/html;charset=UTF-8");//通知浏览器以utf-8打开 PrintWriter out = response.getWriter(); out.write(s);//默认查的是ISO-8859-1码表  } //字符流输出中文数据 private void test2(HttpServletResponse response) throws IOException{ String s = "你好！二"; response.setCharacterEncoding("UTF-8"); response.setContentType("text/html;charset=UTF-8"); PrintWriter out = response.getWriter(); out.write(s); } //字符流输出中文数据 private void test3(HttpServletResponse response) throws IOException{ String s = "你好！三"; response.setContentType("text/html;charset=UTF-8"); PrintWriter out = response.getWriter(); out.write(s); } public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { doGet(request,response); } }

分析：

乱码原因：以默认编码发送数据 ISO-8859-1（没有中国二字编码），此时会发生乱码

解决办法：

1）

setCharacterEncoding(“UTF-8”);//更改编码为UTF-8

response.setHead(“Context-type”,”text/html;charset=UTF-8”);//告诉客户端编码方式

2）response.setContentType("text/html;charset=utf-8");

在字符流输出中文数据时:

response.setContentType("text/html;charset=utf-8");有两个作用：

通知字符流以UTF-8编码输出

通知客户端以UTF-8解码显示

3.输出随机验证码

package cn.lsl.response;import java.awt.Color;
import java.awt.Font; import java.awt.Graphics; import java.awt.image.BufferedImage; import java.io.IOException; import java.util.Random; import javax.imageio.ImageIO; import javax.servlet.ServletException; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; public class ResponseDemo3 extends HttpServlet { public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { //通知浏览器不要缓存 response.setHeader("Expires", "-1"); response.setHeader("Cache-Control", "no-cache"); response.setHeader("Pragma", "no-cache"); int width = 120; int height = 25; //创建一副内存图像BufferedImage BufferedImage image = new BufferedImage(width,height,BufferedImage.TYPE_INT_RGB); //得到属于该图片的画笔：Graphics(); Graphics g = image.getGraphics(); //画边框  g.setColor(Color.BLUE); g.drawRect(0, 0, width, height); //填充背景色  g.setColor(Color.YELLOW); g.fillRect(1, 1, width-2, height-2); //画干扰线  g.setColor(Color.GRAY); Random r = new Random(); for(int i=0; i<10; i++) g.drawLine(r.nextInt(width), r.nextInt(height), r.nextInt(width), r.nextInt(height)); //随机数字  g.setColor(Color.RED); g.setFont(new Font("宋体",Font.BOLD|Font.ITALIC,20)); int x = 23; for(int i=0; i<4; i++){ g.drawString(r.nextInt(10)+"", x, 20); x = x+20; } //输出到浏览器的页面上：ImageIO ImageIO.write(image, "jpg", response.getOutputStream()); } public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { doGet(request,response); } }

4.定时刷新

package cn.lsl.response;import java.io.IOException;
import java.io.PrintWriter; import java.util.Random; import javax.servlet.ServletException; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; public class ResponseDemo4 extends HttpServlet { public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { test2(response); } //定时刷新到自己 private void test1(HttpServletResponse response) throws IOException{ Random r = new Random(); int i = r.nextInt(); response.setIntHeader("Refresh", 1); response.getOutputStream().write((i+"").getBytes()); } //刷到别的页面 private void test2(HttpServletResponse response) throws IOException{ response.setContentType("text/html;charset=UTF-8"); PrintWriter out = response.getWriter(); response.setHeader("Refresh", "2;URL=/Response/index.jsp"); out.write("登陆成功！2秒后将跳转到主页！若没有跳转，请猛点<a href='/Response/index.jsp'>这里</a>"); } public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { doGet(request,response); } }

5.控制缓存时间

package cn.lsl.response;import java.io.IOException;import javax.servlet.ServletException; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; public class ResponseDemo5 extends HttpServlet { public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { //缓存一小时  response.setDateHeader("Expires", System.currentTimeMillis()+60*60*1000); response.getWriter().write("hello"); } public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { doGet(request,response); } }

6.请求重定向

请求重定向：一个web资源收到客户端请求后，通知客户端去访问另外一个web资源，这称之为请求重定向。

地址栏会连，并发送2次请求，增加服务器负担。

实现方式：response.sendRedirect();

原理：302/307状态码和location头即可实现重定向

package cn.lsl.response;
import java.io.IOException;
import javax.servlet.ServletException; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; public class ResponseDemo6 extends HttpServlet { public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { // response.setStatus(302); // response.setHeader("Location", "/Response/index.jsp"); response.sendRedirect("/Response/index.jsp"); } public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { doGet(request,response); } }

7.getOutputStream和getWriter方法分别用于得到输出二进制数据、输出文本数据的ServletOuputStream、Printwriter对象。

getOutputStream和getWriter这两个方法互相排斥，调用了其中的任何一个方法后，就不能再调用另一方法。会抛异常。

异常为：getOutputStream() has already been called for this response

package cn.lsl.response;import java.io.IOException;
import java.io.PrintWriter; import javax.servlet.ServletException; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; //字节流和字符流同时使用，报错 //getOutputStream() has already been called for this response public class ResponseDemo7 extends HttpServlet { public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { String s1 = "a"; response.getOutputStream().write(s1.getBytes()); String s2 = "b"; response.getWriter().write(s2); } public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { doGet(request,response); } }

注：通过字符流或字节流输出的数据并不是直接打给浏览器的。而是把数据写到response对象的缓存中的。服务器从缓存中取出数据，按照HTTP协议的响应格式输出给浏览器。如果你调用的response的输出流没有主动关闭，服务器会替你关的。

HttpServletRequest

HttpServletRequest对象代表客户端的请求，当客户端通过HTTP协议访问服务器时，HTTP请求头中的所有信息都封装在这个对象中，通过这个对象的方法，可以获得客户这些信息。

1.获取客户机信息的方法

getRequestURL方法返回客户端发出请求时的完整URL。

getRequestURI方法返回请求行中的资源名部分。

getQueryString 方法返回请求行中的参数部分。

getRemoteAddr方法返回发出请求的客户机的IP地址

getRemoteHost方法返回发出请求的客户机的完整主机名

getRemotePort方法返回客户机所使用的网络端口号

getLocalAddr方法返回WEB服务器的IP地址。

getLocalName方法返回WEB服务器的主机名

getMethod得到客户机请求方式

eg：

package cn.lsl.request;
import java.io.IOException;
import javax.servlet.ServletException; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; //获取客户机信息 public class RequestDemo1 extends HttpServlet { public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { //获取URL和URI //url:http://localhost:8080/Request/servlet/RequestDemo1 //uri:/Request/servlet/RequestDemo1 System.out.println("url:"+request.getRequestURL()); System.out.println("uri:"+request.getRequestURI()); //通过getQueryString可以获得get方式提交查询串url中？后面部分 System.out.println("queryString:"+request.getQueryString()); //获得客户端ip System.out.println("ip:"+request.getRemoteAddr()); //通过getContextPath获得工程虚拟目录名称 System.out.println("工程虚拟目录名称:"+request.getContextPath()); //通过getMethod获得请求方式 System.out.println("请求方式："+request.getMethod()); //获得当前访问资源路径 ----/servlet/RequestDemo1 System.out.println("当前访问资源路径:"+request.getRequestURI().substring(request.getContextPath().length())); } public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { doGet(request,response); } }

注：

1)URL和URI的区别

URL: http://localhost:8080/Request/servlet/RequestDemo1

URI: /Request/servlet/RequestDemo1

URI 包含 URL的，URL 一定完成路径，URI可以相对路径

http://localhost:8080/Request/servlet/RequestDemo1

是一个URL 同时也是 URI

/Request/servlet/RequestDemo1 ---- 都是URI 不是URL

2)获得当前访问资源路径：

request.getRequestURI().substring(request.getContextPath().length());

2.获取请求头信息

getHeader 获得头信息的值，转换一个字符串

getHeaders 获得头信息值，获得Enumeration

getHeaderNames 获得所有头信息名称返回 Enumeration

eg:

package cn.lsl.request;import java.io.IOException;
import java.util.Enumeration; import javax.servlet.ServletException; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; public class RequestDemo2 extends HttpServlet { public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { //获取指定头信息字段 String value = request.getHeader("Accept-Encoding"); System.out.println(value); System.out.println("---------------"); //获得所有头信息内容 Enumeration<String> enumeration = request.getHeaderNames(); while(enumeration.hasMoreElements()){ String name = enumeration.nextElement(); System.out.println(name+":"+request.getHeader(name)); } } public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { doGet(request,response); } }

3.防盗链程序

referer.html

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html> <head> <title>referer.html</title> <meta http-equiv="keywords" content="keyword1,keyword2,keyword3"> <meta http-equiv="description" content="this is my page"> <meta http-equiv="content-type" content="text/html; charset=UTF-8"> </head> <body> <h1>通过链接访问RequestDemo3 不是盗链</h1> <a href="/Request/servlet/RequestDemo3">link</a> </body> </html>

package cn.lsl.request;import java.io.IOException;
import javax.servlet.ServletException; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; public class RequestDemo3 extends HttpServlet { //防盗链 public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { //通过getHeader获得referer头信息 String referer = request.getHeader("referer"); //判断头信息可以知道是不是盗链 response.setContentType("text/html;charset=utf-8"); if(referer == null || !referer.startsWith("http://localhost")){ //盗链 response.getWriter().println("是盗链"); }else{ //不是盗链 response.getWriter().println("真不是盗链"); } } public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { doGet(request,response); } }

4.获取客户机请求参数

常用API四个

getParameter

getParameterValues

getParameterNames

getParameterMap

eg：

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html> <head> <title>request.html</title> <meta http-equiv="keywords" content="keyword1,keyword2,keyword3"> <meta http-equiv="description" content="this is my page"> <meta http-equiv="content-type" content="text/html; charset=UTF-8"> </head> <body> <h1>分别以get和post方式提交数据</h1> <h1>第一种：通过超链接提交数据以？方式</h1> <a href="/Request/servlet/RequestDemo4?name=zhangsan&city=shenzhen">超链接提交数据</a> <h1>第二种：通过form的post方式提交数据</h1> <form action="/Request/servlet/RequestDemo4" method="post"> 姓名<input type="text" name="name" /><br/> 城市<input type="text" name="city" /><br/> <input type="submit" value="提交"> </form> </body> </html>

package cn.lsl.request;import java.io.IOException;
import java.io.PrintWriter; import javax.servlet.ServletException; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; public class RequestDemo4 extends HttpServlet { public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { String name = request.getParameter("name"); System.out.println(name); String city = request.getParameter("city"); System.out.println(city); } public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { doGet(request,response); } }

5.获取复杂表单的数据及解决中文乱码问题

regist.html

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html> <head> <title>regist.html</title> <meta http-equiv="keywords" content="keyword1,keyword2,keyword3"> <meta http-equiv="description" content="this is my page"> <meta http-equiv="content-type" content="text/html; charset=UTF-8"> </head> <body> <form action="/Request/servlet/RequestDemo5" method="post"> <table> <tr> <td> 用户名 </td> <td> <input type="text" name="username" /> </td> </tr> <tr> <td> 密码 </td> <td> <input type="password" name="password" /> </td> </tr> <tr> <td> 性别 </td> <td> <input type="radio" name="gender" value="male" /> 男 <input type="radio" name="gender" value="female" /> 女 </td> </tr> <tr> <td> 爱好 </td> <td> <input type="checkbox" name="hobby" value="sport" /> 运动 <input type="checkbox" name="hobby" value="music" /> 音乐 <input type="checkbox" name="hobby" value="game" /> 游戏 </td> </tr> <tr> <td> 城市 </td> <td> <select name="city"> <option value="beijing"> 北京 </option> <option value="shanghai"> 上海 </option> <option value="shenzhen"> 深圳 </option> </select> </td> </

转载于:https://www.cnblogs.com/wl0000-03/p/6098552.html

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