request对象和response对象
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。
1.要得到客户机提交过来的数据,只需要找request对象就行了。
2、要向客户机输出数据,只需要找response对象就行了。
一、response对象
1.1向客户端发送数据,以字节为单位(一定要先设置编码方式,再输出)
- String data = "你好,中国1";
- OutputStream out = response.getOutputStream();
- out.write(data.getBytes());//查找本机默认编码进行编码
- String data = "你好,中国2";
- OutputStream out = response.getOutputStream();
- out.write(data.getBytes("UTF-8"));//以UTF-8进行编码
- //告诉浏览器编码方式
- response.setHeader("Content-Type","text/html;charset=UTF-8" );
- String data = "你好,中国3";
- OutputStream out = response.getOutputStream();
- out.write("<meta http-equiv='Content-Type' content='text/html;charset=UTF-8'>".getBytes());////通过meta标签模拟请求头
- out.write(data.getBytes("UTF-8"));//以UTF-8进行编码
- String data = "你好,中国4";
- OutputStream out = response.getOutputStream();
- response.setContentType("text/html;charset=UTF-8");
- out.write(data.getBytes("UTF-8"));//以UTF-8进行编码
- response.setContentType("text/html;charset=UTF-8");
等价于下面两句代码的效果:
response.setCharacterEncoding("UTF-8");//更改服务器发送数据的默认编码
response.setHeader("Content-Type","text/html;charset=UTF-8");//还要通知客户端解码方式
- int x=97;
- OutputStream out = response.getOutputStream();
- out.write((x+"").getBytes());////向客户端发送数字
1.2 以字符为单位向客户端发送数据
String data = "你是谁?";
response.setCharacterEncoding("UTF-8"); //设置编码为UTF-8
response.setHeader("Content-Type", "text/html;charset=UTF-8");//告诉客户端编码方式
// 第二种方法:相当于以上两句代码
//response.setContentType("text/html;charset=UTF-8");
PrintWriter writer = response.getWriter();//默认编码是iso-8859-1 创建该对象前必须设置好编码方式
writer.write(data);
System.out.println(response.getCharacterEncoding());
1.3 让客户端以下载方式打开文件,解决中文文件名乱码问题(URLEncoder.encode(name, "UTF-8"))
- //得到文件的真实路径
- String realPath = getServletContext().getRealPath("/files/漂亮美眉.jpg");
- //获取文件名
- String name = realPath.substring(realPath.lastIndexOf("\\"));
- //设置响应头,通知客户端以下载的方式打开文件
- response.setHeader("Content-Disposition", "attachment;filename="+URLEncoder.encode(name, "UTF-8"));
- //构建输入流
- InputStream in = new FileInputStream(realPath);
- //输出到客户端的流
- OutputStream out = response.getOutputStream();
- int len = -1;
- byte buf[] = new byte[1024];
- while((len=in.read(buf))!=-1)
- {
- out.write(buf, 0, len);
- }
- in.close();
1.4 输出随机数字生成验证码图片
- //设置不要缓存(3种方式,建议三种都设置,防止浏览器不支持)
- response.addHeader("Pragma", "no-cache");
- response.setHeader("Cache-Control", "no-cache");
- response.setHeader("Expires", "0");
- //1.内存图像 BufferedImage
- BufferedImage image = new BufferedImage(WIDTH,HEIGHT,BufferedImage.TYPE_INT_RGB);
- //2.创建画笔
- Graphics g = image.getGraphics();
- //2.1画边框
- g.setColor(Color.GRAY);//设置边框颜色
- g.drawRect(0, 0, WIDTH, HEIGHT);//画矩形边框
- //2.2填充边框
- g.fillRect(1, 1, WIDTH-1, HEIGHT-1);
- //2.3输出验证随机数字4个
- Random r = new Random();
- g.setColor(Color.BLUE);
- int x = 5;
- for(int i=0;i<4;i++)
- {
- g.setFont(new Font("宋体",Font.BOLD,20));
- g.drawString(r.nextInt(10)+"", x, 20);
- x+=30;
- }
- //2.4画干扰线
- g.setColor(Color.YELLOW);
- for(int i = 0;i<9;i++)
- {
- g.drawLine(r.nextInt(WIDTH),r.nextInt(HEIGHT), r.nextInt(WIDTH), r.nextInt(HEIGHT));
- }
- //3 利用response输出流输出image
- ImageIO.write(image,"jpeg",response.getOutputStream());<pre name="code" class="java"> //response.setHeader("Expires", (System.currentTimeMillis()+24*3600*10*1000)+"");//缓存10天
- response.setDateHeader("Expires",System.currentTimeMillis()+10*24*1000*60*60);</pre><br>
- <pre></pre>
- <p></p>
- <pre></pre>
- 1.5 控制客户端刷新时间
- <p></p>
- <p></p>
- <pre name="code" class="java"> //response.setHeader("Refresh", "5;URL=/day05/default.html");//5秒后跳转,url是跳转的链接
- response.getOutputStream().write("<meta http-equiv=\"Refresh\" content=\"3;URL=/day05/login.html\">".getBytes());</pre>1.6 控制客户端缓存时间
- <p></p>
- <p></p>
- <pre name="code" class="java"> //response.setHeader("Expires", (System.currentTimeMillis()+24*3600*10*1000)+"");//缓存10天
- response.setDateHeader("Expires",System.currentTimeMillis()+10*24*1000*60*60);</pre><br>
- 1.7 用response实现请求重定向
- <p></p>
- <p><img src="http://hi.csdn.net/attachment/201202/14/0_13292204202s0e.gif" alt=""></p>
- <p>特点:地址栏会变,发送两次请求,增加服务器负担。</p>
- <p>实现方式:response.sendRedirect()<br>
- 实现原理:302状态码和location头即可实现重定向<br>
- </p>
- <pre name="code" class="java"> //response.sendRedirect("/day05/servlet/ResponseDemo5");//绝对路径
- 注意 // response.sendRedirect("/servlet/ResponseDemo5");//相对路径这里用是错误的,因为重定向是由客户端发起的
- response.setStatus(307);//302 或者 307都可
- response.setHeader("location", "http://localhost:8080/day05/servlet/ResponseDemo1");</pre><br>
- 1.8 小细节
- <p></p>
- <p></p>
- <pre name="code" class="java"> String s1 = "abc";
- String s2 = "def";
- response.getOutputStream().write(s1.getBytes());
- //response.getWriter().write(s2);
- //注: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。
- //java.lang.IllegalStateException:
- //getOutputStream() has already been called for this response</pre><br>
- <p><br>
- </p>
- <p>二、request(HttpServletRequest)对象</p>
- <p>2.1.get方法</p>
- <p></p><pre name="code" class="java"> String locale = request.getLocalName();//传输协议
- String url = request.getRequestURL().toString();//请求的地址
- String uri = request.getRequestURI();//没有主机名的地址
- String protocol = request.getProtocol();//获取协议
- String add = request.getRemoteAddr();//客户端IP
- String host = request.getRemoteHost();//客户端主机名
- String port = request.getRemotePort()+"";//客户端端口号
- String method = request.getMethod();//客户端的请求方式
- String localAddr = request.getLocalAddr();//获取服务器地址
- String username = request.getParameter("username");//地址后面?请求的参数
- String serverPort = request.getServerPort()+"";//服务器端口号
- String serverName = request.getServerName();//服务器名</pre><br>
- 2.2 获取客户端请求头<p></p>
- <p></p><pre name="code" class="java"> response.setContentType("text/html;charset=UTF-8");
- PrintWriter out = response.getWriter();
- //获取单个请求头的值
- out.write(request.getHeader("Accept-Language")+"<br/>");
- //获取单个请求头多个值
- Enumeration headers = request.getHeaders("user-agent");
- while(headers.hasMoreElements())
- {
- out.println(headers.nextElement()+"<hr/>");
- }
- //获取所有的请求头名
- Enumeration names = request.getHeaderNames();
- while(names.hasMoreElements())
- { //根据请求头名得到对应的值
- String name = (String)names.nextElement();
- out.println(name+"="+request.getHeader(name)+"<br/>");
- }</pre><br>
- 2.3获取请求参数<p></p>
- <p>String usernameValue = request.getParameter("username");//参数不存在为null<br>
- </p>
- <p></p><pre name="code" class="java">String names[] = request.getParameterValues("username");
- for(String name:names)
- {
- System.out.println(name);////得到某个请求参数的所有值
- }</pre><pre name="code" class="java"> //获取所有的请求参数名
- Enumeration names = request.getParameterNames();
- while(names.hasMoreElements())
- { //根据参数名得到值
- String name = (String)names.nextElement();
- System.out.println(name+"------->"+request.getParameter(name));
- }</pre><br>
- 2.4 封装到bean<br>
- <pre name="code" class="java">public class Student {
- private String[] username;
- private String password;
- public String[] getUsername() {
- return username;
- }
- public void setUsername(String[] username) {
- this.username = username;
- }
- public String getPassword() {
- return password;
- }
- public void setPassword(String password) {
- this.password = password;
- }
- }
- </pre><pre name="code" class="java">//利用BeanUtils和 getParameterMap()将对象封装到bean
- private void test5(HttpServletRequest request) {
- // TODO Auto-generated method stub
- Map map = request.getParameterMap();
- Student s = new Student();
- try {
- BeanUtils.populate(s, map);
- } catch (IllegalAccessException e) {
- // TODO Auto-generated catch block
- e.printStackTrace();
- } catch (InvocationTargetException e) {
- // TODO Auto-generated catch block
- e.printStackTrace();
- }
- String[] names = s.getUsername();
- System.out.println(names[0]);//aa
- System.out.println(names[1]);//bb
- System.out.println(s.getPassword());//123
- }//从客户端传过来的值username两个(假如是aa和bb) 和一个password值(假如是123)</pre><br>
- 2.5 得到请求正文<br>
- <pre name="code" class="java"> //获取请求正文
- InputStream in = request.getInputStream();
- byte[] buf =new byte[1024];
- int len = -1;
- while((len=in.read(buf))!=-1)
- {
- System.out.println(new String(buf,0,len));
- }</pre><br>
- 2.6解决请求参数的中文乱码<p></p>
- <p> get方式:先按照原编码得到原始字节码,然后再重新编码。如:name = new String(name.getBytes("ISO-8859-1"),"UTF-8");</p>
- <p>post方式:客户端是什么编码,发送的请求数据就是什么编码,根据客户端的编码,告知服务器编码方式。</p>
- <p>如:request.setCharacterEncoding("UTF-8");// 只适合POST请求方式</p>
- <p><br>
- </p>
- <p>2.7请求转发 forward</p>
- <p><span style="white-space:pre"></span>RequestDispatcher rd = request.getRequestDispatcher("path");//得到转发器,path可以是相对路径或者绝对路径(因为是服务器发起的)<br>
- <span style="white-space:pre"></span>rd.forward(request, response);<br>
- </p>
- <p><img src="http://hi.csdn.net/attachment/201202/14/0_1329238218CM8E.gif" alt=""><br>
- </p>
- <p>2.8 包含include</p>
- <p><span style="white-space:pre"></span>RequestDispatcher rd = request.getRequestDispatcher("/servlet/RequestDemo9");<br>
- <span style="white-space:pre"></span>rd.include(request, response);<br>
- </p>
- <p><img src="http://hi.csdn.net/attachment/201202/14/0_1329238034rHHG.gif" alt=""><br>
- </p>
- <p>三 、路径的写法:<br>
- a、绝对路径写法:ServeltContext都必须用绝对路径。“/”开始 (如ServletContext.getRequestDispatcher("path") path必须是绝对路径)<br>
- b、相对路径:其他情况都可以使用相对路径,也可以使用绝对路径<br>
- <br>
- <br>
- c、在使用绝对路径时,要不要加"/"或者是项目名:如果是服务器调用的,不用加项目名,用“/”就可以代表了当前应用根目录<br>
- 如果是客户端调用的,必须加上项目名<br>
- <br>
- <br>
- 1、转发:request.getRequestDispather(String url)<br>
- 绝对路径:url /servlet/ServletDemo<br>
- 2、重定向:response.sendRedirect(String url)<br>
- 绝对路径:url /day05/servlet/ServletDemo<br>
- <br>
- <br>
- 3、超链接:<a href="url"/><br>
- 绝对路径:url /day05/servlet/ServletDemo<br>
- 4、类加载文件的路径<br>
- web应用中只能用相对路径,相对于classes目录的<br>
- 5、<fomr action="url"/><br>
- 绝对路径:/day05/servlet/ServletDemo<br>
- 6、页面分帧(frame)<br>
- 绝对路径:/day05/servlet/ServletDemo<br>
- 7、ServletContext.getRealPath(url)<br>
- 绝对路径:url /servlet/ServletDemo<br>
- <br>
- <br>
- URLEncoder.encode("name", "UTF-8")//解决文件下载名中文乱码</p>
- <p><br>
- </p>
- <p></p>
参考:
request对象和response对象 - CSDN博客
http://blog.csdn.net/a859522265/article/details/7259115