request和response的知识

约定不等于承诺〃 2022-04-01 10:54 192阅读 0赞

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("<meta http-equiv='content-type' content='text/type;charset=UTF-8'>".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"));
    	}
    }

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);
    		
    	}
    }

//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();
    	}
    }

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="<meta http-equiv='refresh' content='3;url=/testweb/index.jsp'>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,<a href=\"/index.jsp\">请点击此处</a>";
    		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,<a href=\"/index.jsp\">请点击此处</a>");
    	}
    
    	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);
    	}
    
    }

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);
    	}
    
    }

/**
     * 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);
    	}
    
    }