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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