HttpResponse 讲解

HttpServletResponse概述:

​ 在创建Servlet时会覆盖service()方法，或doGet()/doPost(),这些方法都有两个参数，一个为代表请求的request和代表响应response。service方法中的response的类型是ServletResponse，而doGet/doPost方法的response的类型是HttpServletResponse，HttpServletResponse是ServletResponse的子接口，功能和方法更加强大。

Response运行流程

响应头有很多这里只介绍常用的。

在浏览器可以按F12 抓包看响应头、请求头、具体的可以再查。

设置响应行

设置响应的状态码

/*** @Author: crush* @Date: 2021-05-09 19:35* version 1.0*/ @WebServlet("/test3") public class HttpResponseTest3 extends HttpServlet {@Overrideprotected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {System.out.println("设置状态码,前台通过判断状态码，来判断请求是否成功");resp.setStatus(404);}@Overrideprotected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {doGet(req, resp);} }

测试

设置响应头

刷新 跳转页面

/*** @Author: crush* @Date: 2021-05-09 19:35* version 1.0*/ @WebServlet("/test4") public class HttpResponseTest4 extends HttpServlet {@Overrideprotected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {// 设置响应头 每1秒自动刷新System.out.println("设置响应头 每1秒自动刷新");resp.setHeader("Refresh", "1");//定时跳转 3秒后将自动跳转 // resp.setHeader("Refresh","3;URL=hello.jsp");}@Overrideprotected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {doGet(req, resp);} }

测试

一个小demo 实现刷新 页面累加

/*** response* @author Adimi*/ @WebServlet("/test4") public class ResponseTest4 extends HttpServlet {private static Integer id=1;@Overrideprotected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {response.setHeader("Refresh","1");PrintWriter writer = response.getWriter();id++;writer.print("id==>"+id);}@Overrideprotected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {doGet(req, resp);} }

设置字符编码 解决中文乱码问题

/*** @Author: crush* @Date: 2021-05-09 19:35* version 1.0*/ @WebServlet("/test1") public class HttpResponseTest1 extends HttpServlet {@Overrideprotected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {// 解决中文乱码问题// 设置响应头// 设置字符编码 resp.setCharacterEncoding("UTF-8");// 设置响应内容以什么格式展示到页面 什么编码格式 包含了设置字符编码resp.setContentType("text/html;charset=utf-8");PrintWriter writer = resp.getWriter();writer.print("中国,你好！！！");}@Overrideprotected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {doGet(req, resp);} }

测试

重定向 redirect

/*** 重定向* @Author: crush* @Date: 2021-05-09 19:35* version 1.0*/ @WebServlet("/test5") public class HttpResponseTest5 extends HttpServlet {@Overrideprotected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {resp.sendRedirect("hello.jsp"); // resp.setHeader("location","www.baidu.com"); 通过设置响应头转发}@Overrideprotected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {doGet(req, resp);} }

request转发

/*** 重定向* @Author: crush* @Date: 2021-05-09 19:35* version 1.0*/ @WebServlet("/test5") public class HttpResponseTest5 extends HttpServlet {@Overrideprotected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { // resp.sendRedirect("hello.jsp");req.getRequestDispatcher("hello.jsp").forward(req,resp);}@Overrideprotected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {doGet(req, resp);} }

重定向和转发的区别

文件下载

获取路径资源

String path=this.getServletContext().getRealPath("WEB-INF\\classes\\8.jpg");

读取资源

FileInputStream fileInputStream=new FileInputStream(path);

获取到文件名，路径在电脑上保存的形式是 \ \

String fileName=path.substring(path.lastIndexOf("\\")+1);

设置消息头告诉浏览器，我要下载1.png这个图片 设置编码

resp.setHeader("Content-Disposition", "attachment; filename=" + URLEncoder.encode(fileName, "UTF-8"));

把读取到的内容回送给浏览器

int len=0; byte[] bytes=new byte[1024]; // ServletOutputStream 提供用于将二进制数据发送到客户端的输出流 ServletOutputStream servletOutputStream=resp.getOutputStream(); while((len=fileInputStream.read(bytes))>0) {servletOutputStream.write(bytes,0,len); }

关闭资源

servletOutputStream.close();fileInputStream.close();

注：8.jpg 放在我的resources 文件夹下 但是这里需要写的是编译完8.jpg存放的位置

具体代码

/*** @Author: crush* @Date: 2021-05-09 19:40* version 1.0*/ @WebServlet("/down") public class ResponseDownFile extends HttpServlet {@Overrideprotected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {//获取路径资源String path=this.getServletContext().getRealPath("WEB-INF\\classes\\8.jpg");//读取资源FileInputStream fileInputStream=new FileInputStream(path);//获取到文件名，路径在电脑上保存的形式是\\String fileName=path.substring(path.lastIndexOf("\\")+1);//设置消息头告诉浏览器，我要下载1.png这个图片// 该方式文件名为中文时会乱码//防止中文乱码resp.setHeader("Content-Disposition", "attachment; filename=" + URLEncoder.encode(fileName, "UTF-8"));//把读取到的内容回送给浏览器int len=0;byte[] bytes=new byte[1024];ServletOutputStream servletOutputStream=resp.getOutputStream();while((len=fileInputStream.read(bytes))>0) {servletOutputStream.write(bytes,0,len);}// 关闭资源servletOutputStream.close();fileInputStream.close();}@Overrideprotected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {doGet(req, resp);} }

HttpRequest 讲解

HttpServletRequest概述

​ 我们在创建Servlet时会覆盖service()方法，或doGet()/doPost(),这些方法都有两个参数，一个为代表请求的request和代表响应response。service（）方法中写了根据请求方式的不同调用doget()和dopost().

service方法中的request的类型是ServletRequest，而doGet/doPost方法的request类型HttpServletRequest，HttpServletRequest是ServletRequest的子接口，功能和方法更加强大.

Request 运行流程

获取请求携带的参数

/*** @Author: crush* @Date: 2021-05-11 16:52* version 1.0*/ @WebServlet("/request1") public class RequestTest1 extends HttpServlet {@Overrideprotected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {// 这里是请求的参数名 必须是同名的 String username = req.getParameter("username"); String password = req.getParameter("password");PrintWriter writer = resp.getWriter();writer.print("<h1>"+username+":"+password+"</h1>");}@Overrideprotected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {doGet(req, resp);} }

获取多个参数的值

@Overrideprotected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {// 设置请求的编码 不然会乱码req.setCharacterEncoding("utf-8");Enumeration<String> names = req.getParameterNames();while (names.hasMoreElements()) {String name = (String) names.nextElement();String[] values = req.getParameterValues(name);System.out.println(name+":"+ Arrays.toString(values));}}

获得请求行的信息

/*** @Author: crush* @Date: 2021-05-11 16:52* version 1.0*/ @WebServlet("/request3") public class RequestTest3 extends HttpServlet {@Overrideprotected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {// 获得请求的urlStringBuffer requestURL = req.getRequestURL();System.out.println("请求的URL===>"+requestURL);// 获得请求的Servlet的路径String path = req.getServletPath();System.out.println("请求的Servlet的路径===>"+path);//返回发出此请求的HTTP方法的名称，例如GET，POST或PUTString method = req.getMethod();System.out.println("返回发出此请求的HTTP方法的名称==>"+method);//返回发送请求的客户端或最后一个代理的Internet协议（IP）地址String remoteAddr = req.getRemoteAddr();System.out.println("remoteAddr==>"+remoteAddr);}@Overrideprotected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {doGet(req, resp);} }

request实现转发

/*** @Author: crush* @Date: 2021-05-11 16:52* version 1.0*/ @WebServlet("/request2") public class RequestTest2 extends HttpServlet {@Overrideprotected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {// 访问request2 转发到 request4去req.getRequestDispatcher("/request4").forward(req,resp);}@Overrideprotected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {doGet(req, resp);} }

request是一个域对象

request对象也是一个存储数据的区域对象，所以也具有如下方法：

setAttribute(String name, Object o)

getAttribute(String name)

removeAttribute(String name)

ServletContext 作用域：

创建：启动web应用程序的时候创建

销毁：关闭web应用程序的时候销毁

域的作用范围：整个web应用的启动周期

request作用域：

创建：访问时创建request

销毁：响应结束request销毁

域的作用范围：一次请求中

自言自语

努力生活、加油学习。

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