1 Request 简介

1.1 request 对象和 response 对象的原理

request 和 response 对象是由服务器创建的。我们来使用它们request 对象是来获取请求消息，response 对象是来设置响应消息

1.2 request 对象继承体系结构：

ServletRequest -- 接口 | 继承 HttpServletRequest -- 接口 | 实现 org.apache.catalina.connector.RequestFacade 类(tomcat)

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2 获取请求行数据

* GET /yang/demo1?name=zhangsan HTTP/1.1 * 方法： 1. 获取请求方式 ：GET * String getMethod() 2. 获取虚拟目录：/yang * String getContextPath() 3. 获取Servlet路径: /demo1 * String getServletPath() 4. 获取get方式请求参数：name=zhangsan * String getQueryString() 5. 获取请求URI：/yang/demo1 * String getRequestURI(): /yang/demo1 * StringBuffer getRequestURL() :http://localhost/yang/demo * URL:统一资源定位符 ： http://localhost/yang/demo1 中华人民共和国 * URI：统一资源标识符 : /day14/demo1 共和国 6. 获取协议及版本：HTTP/1.1 * String getProtocol( 7. 获取客户机的IP地址： * String getRemoteAddr() package cn.ys.request; import javax.servlet.ServletException; import javax.servlet.annotation.WebServlet; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import java.io.IOException; /** * 演示Request对象获取请求行数据 */ @WebServlet("/requestDemo1") public class RequestDemo1 extends HttpServlet { protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { } protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { //1. 获取请求方式 ：GET String method = request.getMethod(); System.out.println(method); //2.(*)获取虚拟目录：如果tomcat配置有虚拟路径/yang，会显示为：/yang String contextPath = request.getContextPath(); System.out.println(contextPath); //3. 获取Servlet路径: /requestDemo1 String servletPath = request.getServletPath(); System.out.println(servletPath); //4. 获取get方式请求参数：name=zhangsan String queryString = request.getQueryString(); System.out.println(queryString); //5.(*)获取请求URI：/requestDemo1 如果tomcat配置有虚拟路径/yang，会显示为：/yang/requestDemo1 String requestURI = request.getRequestURI(); // 显示为：/yang/requestDemo1 StringBuffer requestURL = request.getRequestURL(); // ip:port ，显示为：http://localhost:8083/requestDemo1 System.out.println(requestURI); System.out.println(requestURL); //6. 获取协议及版本：HTTP/1.1 String protocol = request.getProtocol(); System.out.println(protocol); //7. 获取客户机的IP地址：0:0:0:0:0:0:0:1 String remoteAddr = request.getRemoteAddr(); System.out.println(remoteAddr); } }

启动程序，浏览器访问：http://localhost:8083/requestDemo1 ，控制台打印：

GET /requestDemo1 null /requestDemo1 http://localhost:8083/requestDemo1 HTTP/1.1 0:0:0:0:0:0:0:1

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3 获取请求头数据

* 方法： * (*)String getHeader(String name):通过请求头的名称获取请求头的值 * Enumeration<String> getHeaderNames():获取所有的请求头名称 package cn.ys.request; import javax.servlet.ServletException; import javax.servlet.annotation.WebServlet; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import java.io.IOException; import java.util.Enumeration; /** * 获取请求头数据 */ @WebServlet("/requestDemo2") public class RequestDemo2 extends HttpServlet { protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { } protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { //演示获取请求头数据 //1.获取所有请求头名称 Enumeration<String> headerNames = request.getHeaderNames(); //2.遍历 while(headerNames.hasMoreElements()){ String name = headerNames.nextElement(); //根据名称获取请求头的值 String value = request.getHeader(name); System.out.println(name + "---" + value); } } }

启动程序，浏览器访问：http://localhost:8083/requestDemo2 ，控制台打印：

host---localhost:8083 connection---keep-alive upgrade-insecure-requests---1 user-agent---Mozilla/5.0 (Macintosh; Intel Mac OS X 10_14_6) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/76.0.3809.100 Safari/537.36 sec-fetch-mode---navigate sec-fetch-user---?1 accept---text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,image/apng,*/*;q=0.8,application/signed-exchange;v=b3 sec-fetch-site---none accept-encoding---gzip, deflate, br accept-language---zh-CN,zh;q=0.9 cookie---Webstorm-831a412=5d726d67-b442-4c10-bfc3-7e79f1e0fd7e; Idea-cd82aecb=0b96a5f9-afc0-46d0-9e7d-5ab2bf244735

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4 浏览器端的重要头信息

Accept：指定浏览器或其他客户端可以处理的 MIME 类型。值 image/png 或 image/jpeg 是最常见的两种可能值。Accept-Charset：指定浏览器可以用来显示信息的字符集。例如 ISO-8859-1。Accept-Encoding：指定浏览器知道如何处理的编码类型。值 gzip 或 compress 是最常见的两种可能值。Accept-Language：指定客户端的首选语言，在这种情况下，Servlet 会产生多种语言的结果。例如，en、en-us、ru 等。Authorization：用于客户端在访问受密码保护的网页时识别自己的身份。|Connection：指示客户端是否可以处理持久 HTTP 连接。持久连接允许客户端或其他浏览器通过单个请求来检索多个文件。值 Keep-Alive 意味着使用了持续连接。|Content-Length：只适用于 POST 请求，并给出 POST 数据的大小（以字节为单位）。|Cookie：把之前发送到浏览器的 cookies 返回到服务器。|Host：指定原始的 URL 中的主机和端口。If-Modified-Since：表示只有当页面在指定的日期后已更改时，客户端想要的页面。如果没有新的结果可以使用，服务器会发送一个 304 代码，表示 Not Modified 头信息。If-Unmodified-Since：是 If-Modified-Since 的对立面，它指定只有当文档早于指定日期时，操作才会成功。Referer：指示所指向的 Web 页的 URL。例如，如果您在网页 1，点击一个链接到网页 2，当浏览器请求网页 2 时，网页 1 的 URL 就会包含在 Referer 头信息中。User-Agent：识别发出请求的浏览器或其他客户端，并可以向不同类型的浏览器返回不同的内容。

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5 判断浏览器版本

package cn.ys.request; import javax.servlet.ServletException; import javax.servlet.annotation.WebServlet; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import java.io.IOException; import java.util.Enumeration; /** * 判断浏览器版本 */ @WebServlet("/requestDemo3") public class RequestDemo3 extends HttpServlet { protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { } protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { //演示获取请求头数据:user-agent String agent = request.getHeader("user-agent"); //判断agent的浏览器版本 if(agent.contains("Chrome")){ //谷歌 System.out.println("谷歌来了..."); }else if(agent.contains("Firefox")){ //火狐 System.out.println("火狐来了..."); } } }

启动查询，浏览器输入：http://localhost:8083/requestDemo3 ，控制台打印：

谷歌来了...

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6 防盗链

package cn.ys.request; import javax.servlet.ServletException; import javax.servlet.annotation.WebServlet; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import java.io.IOException; /** * 防盗链 */ @WebServlet("/requestDemo4") public class RequestDemo4 extends HttpServlet { protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { } protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { //演示获取请求头数据:referer String referer = request.getHeader("referer"); System.out.println(referer); // http://localhost:8083/login.html //防盗链 if(referer != null ){ if(referer.contains("/yang")){ //正常访问 // System.out.println("播放电影...."); response.setContentType("text/html;charset=utf-8"); response.getWriter().write("播放电影...."); }else{ //盗链 //System.out.println("想看电影吗？来优酷吧..."); response.setContentType("text/html;charset=utf-8"); response.getWriter().write("想看电影吗？来优酷吧..."); } } } }

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7 获取请求体数据

请求体：只有 POST 请求方式，才有请求体，在请求体中封装了 POST 请求的请求参数 步骤：

1. 获取流对象 * BufferedReader getReader()：获取字符输入流，只能操作字符数据 * ServletInputStream getInputStream()：获取字节输入流，可以操作所有类型数据 * 在文件上传知识点后讲 2. 再从流对象中拿数据 <!DOCTYPE html> <html lang="en"> <head> <meta charset="UTF-8"> <title>注册页面</title> </head> <body> <form action="/requestDemo5" method="post"> <input type="text" placeholder="请输入用户名" name="username"><br> <input type="text" placeholder="请输入密码" name="password"><br> <input type="submit" value="注册"> </form> </body> </html> package cn.ys.request; import javax.servlet.ServletException; import javax.servlet.annotation.WebServlet; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import java.io.BufferedReader; import java.io.IOException; /** * 获取请求消息体 */ @WebServlet("/requestDemo5") public class RequestDemo5 extends HttpServlet { protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { //获取请求消息体--请求参数 //1.获取字符流 BufferedReader br = request.getReader(); //2.读取数据 String line = null; while((line = br.readLine()) != null){ System.out.println(line); // username=zhangsan&password=zhangsan111 } } protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { } }

启动程序，打开页面，表单输入信息提交，控制台打印：

username=zhangsan&password=zhangsan111

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8 获取请求的参数

获取请求参数通用方式：不论 get 还是 post 请求方式都可以使用下列方法来获取请求参数

String getParameter(String name):根据参数名称获取参数值 username=zs&password=123String[] getParameterValues(String name):根据参数名称获取参数值的数组 hobby=xx&hobby=gameEnumeration getParameterNames():获取所有请求的参数名称Map<String,String[]> getParameterMap():获取所有参数的map集合 package cn.ys.request; import javax.servlet.ServletException; import javax.servlet.annotation.WebServlet; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import java.io.BufferedReader; import java.io.IOException; import java.util.Enumeration; import java.util.Map; import java.util.Set; @WebServlet("/requestDemo6") public class RequestDemo6 extends HttpServlet { protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { //post 获取请求参数 //根据参数名称获取参数值 String username = request.getParameter("username"); /* System.out.println("post"); System.out.println(username);*/ //根据参数名称获取参数值的数组 String[] hobbies = request.getParameterValues("hobby"); /*for (String hobby : hobbies) { System.out.println(hobby); }*/ //获取所有请求的参数名称 Enumeration<String> parameterNames = request.getParameterNames(); /*while(parameterNames.hasMoreElements()){ String name = parameterNames.nextElement(); System.out.println(name); String value = request.getParameter(name); System.out.println(value); System.out.println("----------------"); }*/ // 获取所有参数的map集合 Map<String, String[]> parameterMap = request.getParameterMap(); //遍历 Set<String> keyset = parameterMap.keySet(); for (String name : keyset) { //获取键获取值 String[] values = parameterMap.get(name); System.out.println(name); for (String value : values) { System.out.println(value); } System.out.println("-----------------"); } } protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { //get 获取请求参数 /* //根据参数名称获取参数值 String username = request.getParameter("username"); System.out.println("get"); System.out.println(username);*/ this.doPost(request, response); } }

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9 中文乱码问题

* get方式：tomcat 8 已经将 get 方式乱码问题解决了 * post方式：会乱码 * 解决：在获取参数前，设置request的编码request.setCharacterEncoding("utf-8"); package cn.ys.request; import javax.servlet.ServletException; import javax.servlet.annotation.WebServlet; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import java.io.IOException; import java.util.Enumeration; import java.util.Map; import java.util.Set; @WebServlet("/requestDemo7") public class RequestDemo7 extends HttpServlet { protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { //1.设置流的编码 request.setCharacterEncoding("utf-8"); //获取请求参数username String username = request.getParameter("username"); System.out.println(username); } protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { this.doPost(request,response); } }

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10 请求转发：一种在服务器内部的资源跳转方式

1. 步骤： 1. 通过request对象获取请求转发器对象：RequestDispatcher getRequestDispatcher(String path) 2. 使用RequestDispatcher对象来进行转发：forward(ServletRequest request, ServletResponse response) 2. 特点： 1. 浏览器地址栏路径不发生变化 2. 只能转发到当前服务器内部资源中。 3. 转发是一次请求 package cn.ys.request; import javax.servlet.RequestDispatcher; import javax.servlet.ServletException; import javax.servlet.annotation.WebServlet; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import java.io.IOException; @WebServlet("/requestDemo8") public class RequestDemo8 extends HttpServlet { protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { System.out.println("demo8888被访问了。。。"); //转发到demo9资源 /* RequestDispatcher requestDispatcher = request.getRequestDispatcher("/requestDemo9"); requestDispatcher.forward(request,response); */ //存储数据到request域中 request.setAttribute("msg","hello"); request.getRequestDispatcher("/requestDemo9").forward(request, response); //request.getRequestDispatcher("http://www.baidu.com").forward(request, response); } protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { this.doPost(request,response); } }

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11 共享数据

* 域对象：一个有作用范围的对象，可以在范围内共享数据 * request域：代表一次请求的范围，一般用于请求转发的多个资源中共享数据 * 方法： 1. void setAttribute(String name,Object obj):存储数据 2. Object getAttitude(String name):通过键获取值 3. void removeAttribute(String name):通过键移除键值对 package cn.ys.request; import javax.servlet.RequestDispatcher; import javax.servlet.ServletException; import javax.servlet.annotation.WebServlet; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import java.io.IOException; @WebServlet("/requestDemo8") public class RequestDemo8 extends HttpServlet { protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { System.out.println("demo8888被访问了。。。"); //转发到demo9资源 /* RequestDispatcher requestDispatcher = request.getRequestDispatcher("/requestDemo9"); requestDispatcher.forward(request,response); */ //存储数据到request域中 request.setAttribute("msg","hello"); request.getRequestDispatcher("/requestDemo9").forward(request, response); //request.getRequestDispatcher("http://www.baidu.com").forward(request, response); } protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { this.doPost(request,response); } } package cn.ys.request; import javax.servlet.ServletException; import javax.servlet.annotation.WebServlet; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import java.io.IOException; @WebServlet("/requestDemo9") public class RequestDemo9 extends HttpServlet { protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { //获取数据 Object msg = request.getAttribute("msg"); System.out.println(msg); System.out.println("demo9999被访问了。。。"); } protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { this.doPost(request,response); } }

启动程序，浏览器输入：http://localhost:8083/requestDemo8 ，控制台打印：

demo8888被访问了。。。 hello demo9999被访问了。。。

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12 ServletContext

获取 ServletContext * ServletContext getServletContext()

package cn.ys.request; import javax.servlet.ServletContext; import javax.servlet.ServletException; import javax.servlet.annotation.WebServlet; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import java.io.IOException; @WebServlet("/requestDemo10") public class RequestDemo10 extends HttpServlet { protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { ServletContext servletContext = request.getServletContext(); System.out.println(servletContext); } protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { this.doPost(request,response); } }

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13 案例：用户登录

用户登录案例需求：

编写login.html登录页面 username & password 两个输入框使用Druid数据库连接池技术,操作mysql，day14数据库中user表使用JdbcTemplate技术封装JDBC登录成功跳转到SuccessServlet展示：登录成功！用户名,欢迎您登录失败跳转到FailServlet展示：登录失败，用户名或密码错误

开发步骤

1. 创建项目，导入html页面，配置文件，jar包 2. 创建数据库环境 CREATE DATABASE day14; USE day14; CREATE TABLE USER( id INT PRIMARY KEY AUTO_INCREMENT, username VARCHAR(32) UNIQUE NOT NULL, PASSWORD VARCHAR(32) NOT NULL ); 3. 创建包cn.itcast.domain,创建类User package cn.itcast.domain; /** * 用户的实体类 */ public class User { private int id; private String username; private String password; public int getId() { return id; } public void setId(int id) { this.id = id; } public String getUsername() { return username; } public void setUsername(String username) { this.username = username; } public String getPassword() { return password; } public void setPassword(String password) { this.password = password; } @Override public String toString() { return "User{" + "id=" + id + ", username='" + username + '\'' + ", password='" + password + '\'' + '}'; } } 4. 创建包cn.itcast.util,编写工具类JDBCUtils package cn.itcast.util; import com.alibaba.druid.pool.DruidDataSourceFactory; import javax.sql.DataSource; import javax.xml.crypto.Data; import java.io.IOException; import java.io.InputStream; import java.sql.Connection; import java.sql.SQLException; import java.util.Properties; /** * JDBC工具类 使用Durid连接池 */ public class JDBCUtils { private static DataSource ds ; static { try { //1.加载配置文件 Properties pro = new Properties(); //使用ClassLoader加载配置文件，获取字节输入流 InputStream is = JDBCUtils.class.getClassLoader().getResourceAsStream("druid.properties"); pro.load(is); //2.初始化连接池对象 ds = DruidDataSourceFactory.createDataSource(pro); } catch (IOException e) { e.printStackTrace(); } catch (Exception e) { e.printStackTrace(); } } /** * 获取连接池对象 */ public static DataSource getDataSource(){ return ds; } /** * 获取连接Connection对象 */ public static Connection getConnection() throws SQLException { return ds.getConnection(); } } 5. 创建包cn.itcast.dao,创建类UserDao,提供login方法 package cn.itcast.dao; import cn.itcast.domain.User; import cn.itcast.util.JDBCUtils; import org.springframework.dao.DataAccessException; import org.springframework.jdbc.core.BeanPropertyRowMapper; import org.springframework.jdbc.core.JdbcTemplate; /** * 操作数据库中User表的类 */ public class UserDao { //声明JDBCTemplate对象共用 private JdbcTemplate template = new JdbcTemplate(JDBCUtils.getDataSource()); /** * 登录方法 * @param loginUser 只有用户名和密码 * @return user包含用户全部数据,没有查询到，返回null */ public User login(User loginUser){ try { //1.编写sql String sql = "select * from user where username = ? and password = ?"; //2.调用query方法 User user = template.queryForObject(sql, new BeanPropertyRowMapper<User>(User.class), loginUser.getUsername(), loginUser.getPassword()); return user; } catch (DataAccessException e) { e.printStackTrace();//记录日志 return null; } } } 6. 编写cn.itcast.web.servlet.LoginServlet类 package cn.itcast.web.servlet; import cn.itcast.dao.UserDao; import cn.itcast.domain.User; import javax.servlet.ServletException; import javax.servlet.annotation.WebServlet; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import java.io.IOException; @WebServlet("/loginServlet") public class LoginServlet extends HttpServlet { @Override protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { //1.设置编码 req.setCharacterEncoding("utf-8"); //2.获取请求参数 String username = req.getParameter("username"); String password = req.getParameter("password"); //3.封装user对象 User loginUser = new User(); loginUser.setUsername(username); loginUser.setPassword(password); //4.调用UserDao的login方法 UserDao dao = new UserDao(); User user = dao.login(loginUser); //5.判断user if(user == null){ //登录失败 req.getRequestDispatcher("/failServlet").forward(req,resp); }else{ //登录成功 //存储数据 req.setAttribute("user",user); //转发 req.getRequestDispatcher("/successServlet").forward(req,resp); } } @Override protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { this.doGet(req,resp); } } 7. 编写FailServlet和SuccessServlet类 @WebServlet("/successServlet") public class SuccessServlet extends HttpServlet { protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { //获取request域中共享的user对象 User user = (User) request.getAttribute("user"); if(user != null){ //给页面写一句话 //设置编码 response.setContentType("text/html;charset=utf-8"); //输出 response.getWriter().write("登录成功！"+user.getUsername()+",欢迎您"); } } @WebServlet("/failServlet") public class FailServlet extends HttpServlet { protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { //给页面写一句话 //设置编码 response.setContentType("text/html;charset=utf-8"); //输出 response.getWriter().write("登录失败，用户名或密码错误"); } protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { this.doPost(request,response); } } 8. login.html中form表单的action路径的写法 * 虚拟目录+Servlet的资源路径 9. BeanUtils工具类，简化数据封装 * 用于封装JavaBean的 1. JavaBean：标准的Java类 1. 要求： 1. 类必须被public修饰 2. 必须提供空参的构造器 3. 成员变量必须使用private修饰 4. 提供公共setter和getter方法 2. 功能：封装数据 2. 概念： 成员变量： 属性：setter和getter方法截取后的产物 例如：getUsername() --> Username--> username 3. 方法： 1. setProperty() 2. getProperty() 3. populate(Object obj , Map map):将map集合的键值对信息，封装到对应的JavaBean对象中