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)
[java] view plain copy PRint?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1"; OutputStream out = response.getOutputStream(); out.write(data.getBytes());//查找本机默认编码进行编码[java] view plain copy print? 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" );[java] view plain copy print?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[java] view plain copy print?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[java] view plain copy print?[java] view plain copy print?response.setContentType(“text/html;charset=UTF-8”);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
[java] view plain copy print?int x=97; OutputStream out = response.getOutputStream(); out.write((x+”“).getBytes());////向客户端发送数字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”))
[java] view plain copy print?//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();//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[java] view plain copy print? //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://s1.VeVb.com/20170221/ngwujgzxrds53.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://s1.VeVb.com/20170221/5nqhuq3ypfu53.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://s1.VeVb.com/20170221/wpjzchfijqx53.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>//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());[java] view plain copy print?//response.setHeader("Expires", (System.currentTimeMillis()+24*3600*10*1000)+"");//缓存10天 response.setDateHeader("Expires",System.currentTimeMillis()+10*24*1000*60*60);//response.setHeader("Expires", (System.currentTimeMillis()+24*3600*10*1000)+"");//缓存10天 response.setDateHeader("Expires",System.currentTimeMillis()+10*24*1000*60*60);1.5 控制客户端刷新时间[java] view plain copy print?//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());//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());1.6 控制客户端缓存时间[java] view plain copy print?//response.setHeader(“Expires”, (System.currentTimeMillis()+24*3600*10*1000)+”“);//缓存10天 response.setDateHeader(”Expires”,System.currentTimeMillis()+10*24*1000*60*60);//response.setHeader("Expires", (System.currentTimeMillis()+24*3600*10*1000)+"");//缓存10天 response.setDateHeader("Expires",System.currentTimeMillis()+10*24*1000*60*60);1.7 用response实现请求重定向
特点：地址栏会变，发送两次请求，增加服务器负担。
实现方式：response.sendRedirect()实现原理：302状态码和location头即可实现重定向
[java] view plain copy print? //response.sendRedirect(“/day05/servlet/ResponseDemo5”);//绝对路径 // 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”);//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");1.8 小细节[java] view plain copy print?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 responseString 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二、request（HttpServletRequest）对象
2.1.get方法
[java] view plain copy print?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2.2 获取客户端请求头[java] view plain copy print?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/>”); }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/>"); }2.3获取请求参数String usernameValue = request.getParameter(“username”);//参数不存在为null
[java] view plain copy print?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 }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 }[java] view plain copy print? //获取所有的请求参数名 ion 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)); }//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)); }2.4 封装到bean[java] view plain copy print?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; } }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; }}[java] view plain copy print?//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)//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)2.5 得到请求正文[java] view plain copy print?//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)); }//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)); }2.6解决请求参数的中文乱码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”);
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。
如：request.setCharacterEncoding(“UTF-8”);// 只适合POST请求方式
2.7请求转发 forward
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）rd.forward(request, response);
2.8 包含include
RequestDispatcher rd = request.getRequestDispatcher(“/servlet/RequestDemo9”);rd.include(request, response);
三 、路径的写法: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）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如果是客户端调用的，必须加上项目名1、转发：request.getRequestDispather(String url)绝对路径：url /servlet/ServletDemo2、重定向：response.sendRedirect(String url)绝对路径：url /day05/servlet/ServletDemo3、超链接：<a href=”url”/>绝对路径：url /day05/servlet/ServletDemo4、类加载文件的路径web应用中只能用相对路径，相对于classes目录的5、<fomr action=”url”/>绝对路径：/day05/servlet/ServletDemo6、页面分帧(frame)绝对路径：/day05/servlet/ServletDemo7、ServletContext.getRealPath(url)绝对路径：url /servlet/ServletDemoURLEncoder.encode(“name”, “UTF-8”)//解决文件下载名中文乱码
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