JSP 中request与response的用法详解

作者:袖梨 2023-08-24
这篇文章主要介绍了JSP 中request与response的用法详解的相关资料,希望通过本文能帮助到大家,需要的朋友可以参考下

JSP 中request与response的用法详解

概要:

在学习这两个对象之前,我们应该已经有了http协议的基本了解了,如果不清楚http协议的可以看我的关于http协议的介绍。因为其实request和response的使用大部分都是对http协议的操作。

request对象的介绍

我们先从request对象进行介绍:

我们知道http协议定义了请求服务器的格式:

请求行请求头空格请求体(get请求没有请求体)

好了,这里我们就不详细介绍了,我们只看几个应用就可以了,没什么难度:

应用1 获取请求头

/*** 获取HTTP请求头  *   String getHeader(String name),适用于单值头  *   int getIntHeader(String name),适用于单值int类型的请求头  *   long getDateHeader(String name),适用于单值毫秒类型的请求头  *  Enumeration<String> getHeaders(String name),适用于多值请求头***/ public class CServlet extends HttpServlet {public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {String ip = request.getRemoteAddr();//获取IP地址 String method = request.getMethod();//获取请求方式 System.out.println(ip); System.out.println(method); getLiuLanQi(request); protectMethod(request, response); } //防盗链 public void protectMethod(HttpServletRequest request, HttpServletResponse response) { String url = request.getHeader("referer"); System.out.println(url); if(url != null && url.equalsIgnoreCase("http://localhost:8080/day10/MyHtml.html") ) { System.out.println("hi"); } else { response.setStatus(302); response.setHeader("Location","/day10/MyHtml.html"); System.out.println("重定向"); } } //判断浏览器的类型 public void getLiuLanQi(HttpServletRequest request) { String user = request.getHeader("User-Agent"); if(user != null) { String userNoC = user.toLowerCase(); if(userNoC.contains("chrome")) { System.out.println("浏览器类型:谷歌" ); } else if(userNoC.contains("firefox/")) { System.out.println("浏览器类型:火狐"); } else { System.out.println("浏览器类型:IE"); } } else { System.out.println("null"); } } } 

应用2获取URL路径

/*** 获取请求URL http://localhost:8080/day10_2/AServlet?username=xxx&password=yyy     > String getScheme():获取协议,http     > String getServerName():获取服务器名,localhost     > String getServerPort():获取服务器端口,8080     > *****String getContextPath():获取项目名,/day10_2     > String getServletPath():获取Servlet路径,/AServlet     > String getQueryString():获取参数部分,即问号后面的部分。username=xxx&password=yyy     > String getRequestURI():获取请求URI,等于项目名+Servlet路径。/day10_2/AServlet     > String getRequestURL():获取请求URL,等于不包含参数的整个请求路径。http://localhost:8080/day10_2/AServlet***/ public class DServlet extends HttpServlet {public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { System.out.println(request.getScheme()); System.out.println(request.getServerName()); System.out.println(request.getServerPort()); System.out.println(request.getContextPath()); System.out.println(request.getServletPath()); System.out.println(request.getQueryString()); System.out.println(request.getRequestURI()); System.out.println(request.getRequestURL()); }} 

应用3获取请求参数

/**** 请求参数:有一个参数一个值的,还有一个参数多个值!     > *****String getParameter(String name):获取指定名称的请求参数值,适用于单值请求参数     > String[] getParameterValues(String name):获取指定名称的请求参数值,适用于多值请求参数     > Enumeration<String> getParameterNames():获取所有请求参数名称     > *****Map<String,String[]> getParameterMap():获取所有请求参数,其中key为参数名,value为参数值。**/ public class EServlet extends HttpServlet {public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { doPost(request,response); }public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { request.setCharacterEncoding("utf-8");//调用他来解决乱码问题的,不会的可以看我写的解决乱码的那一篇 String name = request.getParameter("name"); String password = request.getParameter("password"); String[] aihao = request.getParameterValues("aihao"); response.setHeader("content-type", "text/html;charset=utf-8"); PrintWriter pw = response.getWriter(); pw.println("name:" + name + "<br/>"); pw.println("password:" + password + "<br/>"); pw.print("aihao"); for (int i = 0; i < aihao.length; i++) { switch (i) { case 1: pw.print("吃饭"); break; case 2: pw.print("睡觉"); break; case 3: pw.print("打豆豆"); break;default:break; } } pw.close(); }} 
<!-- 用于发送请求的html --> <html><head> <title>denglu.html</title> <meta http-equiv="content-type" content="text/html; charset=UTF-8"></head><body> <form action="/day10/EServlet" method="post"><!-- 通过post方法提交 --> 姓名:<input type="text" name="name"/><br/> 密码:<input type="password" name="password"><br/> 爱好:<input type="checkbox" name="aihao" value="1"/>吃饭 <input type="checkbox" name="aihao" value="2"/>睡觉 <input type="checkbox" name="aihao" value="3"/>打豆豆 <input type="submit" value="提交"> </form></body> </html> 

应用4设置request对象属性

用来实现同一个应用程序servlet之间值得传递,我们还用到了转发

/***** request域     Servlet中三大域对象:request、session、application,都有如下三个方法:     > void setAttribute(String name, Object value)     > Object getAttribute(String name)> void removeAttribute(String name);     > 同一请求范围内使用request.setAttribute()、request.getAttribute()来传值!前一个Servlet调用setAttribute()保存值,后一个Servlet调用getAttribute()获取值。 **/ public class FServlet extends HttpServlet {public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { request.setAttribute("name","weijinhao"); request.setAttribute("password", "123"); RequestDispatcher rd = request.getRequestDispatcher("/GServlet"); rd.forward(request, response); }} 
public class GServlet extends HttpServlet {public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { String name = (String)request.getAttribute("name"); String password = (String)request.getAttribute("password"); response.setHeader("content-type", "text/html;charset=utf-8"); PrintWriter pw = response.getWriter(); pw.println("name:" + name + "<br/>"); pw.println("password:" + password + "<br/>"); pw.close(); }} 

好了,request的用法大致就是这摸多了。

让我们来看看response对象吧。

response对象的使用

http协议定义了响应浏览器的格式

响应行响应头空格响应体

response对象的大致应用是用在设置响应码,设置响应头,及设置响应正文。

应用1设置响应正文

/*** response的正文* 1,字符流* 2,字节流*/ public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { //String n = "hello javaweb"; //byte[] b = n.getBytes(); //字节流的使用 /*ServletOutputStream outputStream = response.getOutputStream(); outputStream.write(b); outputStream.close();*/ //字符流的使用 /*PrintWriter p = response.getWriter(); p.write(n); p.close();*///commoms工具包的使用 FileInputStream fileInputStream = new FileInputStream("C:/Users/74087/Desktop/6226354_994604.jpg"); byte[] b = IOUtils.toByteArray(fileInputStream); ServletOutputStream outputStream = response.getOutputStream(); outputStream.write(b); outputStream.close(); }} 

应用2 设置响应码和响应头

/***response 的响应码*1, sendError(int sc)//发送错误代码*2, sendError(int sc, java.lang.String msg) //发送错误代码及描述*3, setStatus(int sc) //发送成功响应代码*response 的响应头*1, setDateHeader(java.lang.String name, long date)*2, setHeader(java.lang.String name, java.lang.String value)*3, setIntHeader(java.lang.String name, int value)*下面的和上面的作用一样但是是为了进行多值的添加*addDateHeader(java.lang.String name, long date)*addHeader(java.lang.String name, java.lang.String value)*addIntHeader(java.lang.String name, int value)*/ public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { //sendNum(response); //sendRe(response); //refresh(response); //noCache(response); } //禁用浏览器缓存 public void noCache(HttpServletResponse response) { response.setHeader("Cache-Control","no-cache"); response.setHeader("pragma","0"); response.setHeader("expires","no-cache"); } //自动跳转 public void refresh(HttpServletResponse response) { response.setHeader("refresh", "5;url=http://www.baidu.com"); } //重定向的使用 public void sendRe(HttpServletResponse response) { response.setStatus(302); response.setHeader("Location", "http://www.baidu.com"); }public void sendNum(HttpServletResponse response) throws IOException { response.setStatus(200); response.sendError(404); response.sendError( 404, "ser accept your request but i don't want to you see my web page"); }} 

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