request和response的知识-白红宇

request和response的知识

阅读量：4322 次

发布时间：2019-06-06

本文共 6295 字，大约阅读时间需要 20 分钟。

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public class Demo1 extends HttpServlet {

public void doGet(HttpServletRequest request, HttpServletResponse response)          throws ServletException, IOException {      doPost(request, response);  }    //在servlet中用outputstream输出中文的问题  public void doPost(HttpServletRequest request, HttpServletResponse response)          throws ServletException, IOException {      test4(response);  }  private void test4(HttpServletResponse response)  throws IOException, UnsupportedEncodingException {      //如果servle的代码写成这样"response.getOutputStream().write(1);"，因为      //浏览器默认的编码是gb2312，那么它会去寻找编号为1所对应的字符，结果是为""，      //如果写成字符串"1"的话，那么这个1字符是经过getBytes之后的，所以会直接输出1      response.getOutputStream().write(1);      response.getOutputStream().write("1".getBytes());  }  private void test3(HttpServletResponse response)  throws IOException, UnsupportedEncodingException {      String name="中国3";      //如果程序把text/html后面的;写成了,的话，那么浏览器会提示下载此servlet文件      response.setHeader("Content-type", "text/html,charset=UTF-8");      response.getOutputStream().write(name.getBytes("UTF-8"));  }  private void test2(HttpServletResponse response)      throws IOException, UnsupportedEncodingException {      String name="中国2";      //用html技术中的meta标签来模拟http的响应头，来控制浏览器的行为      response.getOutputStream().write("
    ".getBytes());      response.getOutputStream().write(name.getBytes("UTF-8"));  }  private void test1(HttpServletResponse response)          throws IOException, UnsupportedEncodingException {      String name="中国1";      //程序以什么码表输出了，程序就要控制浏览器以什么样的码表打开      response.setHeader("Content-type", "text/html;charset=UTF-8");      //response.getOutputStream().write(name.getBytes());      response.getOutputStream().write(name.getBytes("UTF-8"));  }

}

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public class Demo2 extends HttpServlet {

public void doGet(HttpServletRequest request, HttpServletResponse response)          throws ServletException, IOException {      doPost(request, response);  }

//通过response的wirter流输出数据

public void doPost(HttpServletRequest request, HttpServletResponse response)

throws ServletException, IOException {

//因为在servlet传递给浏览器的过程中是通过response进行编码后传递的，而老外默认是

//使用iso8859-1来进行编码传递的，所以我们需要对response的编码进行设置，以控制

//response以什么码表向浏览器写出数据

//测试得知，在设置response的编码时最好写在上面

//第一种方式，控制response的编码和浏览器显示的编码,因为浏览器默认是gb2312的      //response.setCharacterEncoding("utf-8");      //下面这句通过response设置浏览器的编码，其实默认同时也把response的编码也给设置了,所以上面的那句话也可以省略掉了      //response.setContentType("text/html;charset=utf-8");            //第二种方式，控制response的编码与浏览器的一致，也就是gb2312编码      response.setCharacterEncoding("gb2312");            String name="中国";      PrintWriter out=response.getWriter();      //第三种方式，不设置response的编码，使用默认的iso8859-1，然后把string转化为8859-1后进行传递      //out.print(new String(name.getBytes(),"iso8859-1"));            out.print(name);        }

}

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//文件下载

public class Demo3 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 {      String path=this.getServletContext().getRealPath("/download/小破孩.jpg");      String filename=path.substring(path.lastIndexOf("/")+1);      //如果下载文件是中文文件，那么文件名需要经过url编码      response.setHeader("content-disposition", "attachment;filename="+URLEncoder.encode(filename,"utf-8"));      InputStream is=new FileInputStream(path);      OutputStream os=response.getOutputStream();      int len=0;      byte[] bs=new byte[1024];      while((len=is.read(bs))>0){          os.write(bs, 0, len);      }      os.close();      is.close();  }

}

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public class Demo5 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 {      //test1(response);      //test2(response);      test3(request,response);  }  //实用的跳转技术，最终的信息还是要在浏览器中显示比较好，这样的话容易排版，test2中是输出的是直接页面的源代码  private void test3(HttpServletRequest request, HttpServletResponse response) throws IOException, ServletException {            String message="
    恭喜你,登录成功了,本浏览器将在3秒后,跳到首页,如果没有跳,请点击此处";      request.setAttribute("message", message);      this.getServletContext().getRequestDispatcher("/forword.jsp").forward(request, response);        }  private void test2(HttpServletResponse response) throws IOException {      //假设这是一个用于登录的Servlet      //假设程序运行到此，用户登录成功了      response.setContentType("text/html;charset=gb2312");      response.setHeader("refresh", "3;url='/testweb/index.jsp'");      response.getWriter().write("恭喜你,登录成功了,本浏览器将在3秒后,跳到首页,如果没有跳,请点击此处");  }  private void test1(HttpServletResponse response) throws IOException {      response.setHeader("refresh", "3");//每隔三秒刷新一次      int data=new Random().nextInt(1000);      response.getWriter().println(data);  }

}

[java] view plain copy

public class Demo5 extends HttpServlet {

public void doGet(HttpServletRequest request, HttpServletResponse response)          throws ServletException, IOException {      //使用expries缓存当前内容      response.setDateHeader("expires", System.currentTimeMillis()+1000*3600);      String data="bbbbbbbbbbbbbbbbbb";      System.out.println("访问---");      response.getWriter().write(data);  }  public void doPost(HttpServletRequest request, HttpServletResponse response)          throws ServletException, IOException {      doGet(request, response);  }

}

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/**

重定向的特点:

1.浏览器会向服务器发送两次请求,意味着就有两个request/response

2.用重定向技术，地址栏会发生变化

*用户登录和购物车时,通常会用到重定向技术

同时调用getOutPutStream()和getWriter()会抛出异常
/
public class Demo6 extends HttpServlet {

public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {

/sendRedirect的内部原理
response.setStatus(302);
response.setHeader("location", "/testweb/index.jsp");
/
response.sendRedirect("/testweb/index.jsp");
}

public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {

doGet(request, response);
}