1. HTTP

概念：Hyper Text Transfer Protocol 超文本传输协议

传输协议：定义了，客户端和服务器端通信时，发送数据的格式

特点：

基于TCP/IP的高级协议默认端口号:80基于请求/响应模型的：一次请求对应一次响应无状态的：每次请求之间相互独立，不能交互数据

历史版本：

1.0：每一次请求响应都会建立新的连接1.1：复用连接

请求消息数据格式

请求行

请求方式 请求url 请求协议/版本

GET /login.html HTTP/1.1

请求方式： HTTP协议有7中请求方式，常用的有2种 GET： 请求参数在请求行中，在url后。请求的url长度有限制的不太安全 POST： 请求参数在请求体中请求的url长度没有限制的相对安全

请求头：客户端浏览器告诉服务器一些信息

请求头名称: 请求头值

常见的请求头：

User-Agent：浏览器告诉服务器，我访问你使用的浏览器版本信息

可以在服务器端获取该头的信息，解决浏览器的兼容性问题

Referer：http://localhost/login.html

告诉服务器，我(当前请求)从哪里来？ 作用：防盗链、统计工作：

请求空行

空行，就是用于分割POST请求的请求头，和请求体的。

请求体(正文)：

封装POST请求消息的请求参数的

字符串格式：

POST /login.html HTTP/1.1

Host: localhost

User-Agent: Mozilla/5.0 (Windows NT 6.1; Win64; x64; rv:60.0) Gecko/0101 Firefox/60.0

Accept: text/html,application/xhtml+xml,application/xml;q=0.9,/;q=0.8

Accept-Language: zh-CN,zh;q=0.8,zh-TW;q=0.7,zh-HK;q=0.5,en-US;q=0.3,en;q=0.2

Accept-Encoding: gzip, deflate

Referer: http://localhost/login.html

Connection: keep-alive

Upgrade-Insecure-Requests: 1

username=zhangsan

响应消息：服务器端发送给客户端的数据

响应行

组成：协议/版本 响应状态码 状态码描述响应状态码：服务器告诉客户端浏览器本次请求和响应的一个状态。 状态码都是3位数字分类： 1xx：服务器就收客户端消息，但没有接受完成，等待一段时间后，发送1xx多状态码2xx：成功。代表：xx：重定向。代表：302(重定向)，304(访问缓存)4xx：客户端错误。 代表： 404（请求路径没有对应的资源）405：请求方式没有对应的doXxx方法 5xx：服务器端错误。代表：500(服务器内部出现异常)

响应头：

格式：头名称： 值常见的响应头： Content-Type：服务器告诉客户端本次响应体数据格式以及编码格式Content-disposition：服务器告诉客户端以什么格式打开响应体数据 in-line：默认值,在当前页面内打开attachment：filename=xxx：以附件形式打开响应体。文件下载

响应空行

响应体:传输的数据

响应字符串格式

HTTP/1.1 200 OK

Content-Type: text/html;charset=UTF-8

Content-Length: 101

Date: Wed, 06 Jun 07:08:42 GMT

(响应体)

2. Request

request对象和response对象的原理

① request和response对象是由服务器创建的。我们来使用它们

② request对象是来获取请求消息，response对象是来设置响应消息

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)

request功能：

获取请求消息数据

获取请求行数据

GET/day14/demo1?name=zhangsan HTTP/1.1方法：

获取请求方式 ：GET

String getMethod()

🧨获取虚拟目录：/day14🧨

String getContextPath()

获取Servlet路径: /demo1

String getServletPath()

获取get方式请求参数：name=zhangsan

String getQueryString()

🧨获取请求URI：/day14/demo1🧨

String getRequestURI(): /day14/demo1

StringBuffer getRequestURL() :http://localhost/day14/demo1

URL:统一资源定位符 ： http://localhost/day14/demo1 中华人民共和国

URI：统一资源标识符 : /day14/demo1 共和国

获取协议及版本：HTTP/1.1

String getProtocol()

获取客户机的IP地址：

String getRemoteAddr()

package cn.itcast.web.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 getMethod()2. (*)获取虚拟目录：/day14* String getContextPath()3. 获取Servlet路径: /requestDemo1* String getServletPath()4. 获取get方式请求参数：name=zhangsan* String getQueryString()5. (*)获取请求URI：/day14/demo1* String getRequestURI():/day14/requestDemo1* StringBuffer getRequestURL() :http://localhost/day14/requestDemo16. 获取协议及版本：HTTP/1.1* String getProtocol()7. 获取客户机的IP地址：* String getRemoteAddr()*///1. 获取请求方式 ：GETString method = request.getMethod();System.out.println(method);//2.(*)获取虚拟目录：/day14String contextPath = request.getContextPath();System.out.println(contextPath);//3. 获取Servlet路径: /demo1String servletPath = request.getServletPath();System.out.println(servletPath);//4. 获取get方式请求参数：name=zhangsanString queryString = request.getQueryString();System.out.println(queryString);//5.(*)获取请求URI：/day14/demo1String requestURI = request.getRequestURI();StringBuffer requestURL = request.getRequestURL();System.out.println(requestURI);System.out.println(requestURL);//6. 获取协议及版本：HTTP/1.1String protocol = request.getProtocol();System.out.println(protocol);//7. 获取客户机的IP地址：String remoteAddr = request.getRemoteAddr();System.out.println(remoteAddr);}}

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

获取user-agent

package cn.itcast.web.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;@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-agentString 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...");}}}

获取referer

package cn.itcast.web.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("/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:refererString referer = request.getHeader("referer");System.out.println(referer);//http://localhost/day14/login.html//防盗链if(referer != null ){if(referer.contains("/day14")){//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...");}}}}

Enumeration getHeaderNames():获取所有的请求头名称

package cn.itcast.web.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;`在这里插入代码片`import java.util.Enumeration;@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);}}}

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：

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

再从流对象中拿数据

package cn.itcast.web.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;@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);}}protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {}}

其他功能：

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 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.itcast.web.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);}}

请求转发：一种在服务器内部的资源跳转方式

步骤：

通过request对象获取请求转发器对象：RequestDispatcher getRequestDispatcher(String path)使用RequestDispatcher对象来进行转发：forward(ServletRequest request, ServletResponse response)

特点：

浏览器地址栏路径不发生变化只能转发到当前服务器内部资源中。转发是一次请求

package cn.itcast.web.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("").forward(request,response);}protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {this.doPost(request,response);}}

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： void setAttribute(String name,Object obj):存储数据Object getAttitude(String name):通过键获取值void removeAttribute(String name):通过键移除键值对

结合上面存储代码一起看

package cn.itcast.web.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);}}

获取ServletContext：

ServletContext getServletContext()

3. 案例

需求：

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

分析

开发步骤

创建项目，导入html页面，配置文件，jar包

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);

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;}@Overridepublic String toString() {return "User{" +"id=" + id +", username='" + username + '\'' +", password='" + password + '\'' +'}';}}

创建包cn.itcast.util,编写工具类JDBCUtils

package cn.itcast.util;importcom.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();}}

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sqlString 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;}}}

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 {@Overrideprotected 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userif(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);}}@Overrideprotected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {this.doGet(req,resp);}}

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);}}

login.html中form表单的action路径的写法

虚拟目录+Servlet的资源路径

BeanUtils工具类，简化数据封装

用于封装JavaBean的

JavaBean：标准的Java类

要求： 类必须被public修饰必须提供空参的构造器成员变量必须使用private修饰提供公共setter和getter方法 功能：封装数据

概念：

成员变量：

属性：setter和getter方法截取后的产物

例如：getUsername() --> Username–> username

方法：

setProperty()：设置属性值getProperty()：获取属性值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

4. Response

设置响应行

格式：HTTP/1.1 200 ok设置状态码：setStatus(int sc)

设置响应头：setHeader(String name, String value)

设置响应体：

使用步骤：

获取输出流

字符输出流：PrintWriter getWriter()

字节输出流：ServletOutputStream getOutputStream()

使用输出流，将数据输出到客户端浏览器

案例：

① 完成重定向

重定向：资源跳转的方式

代码实现：

package cn.itcast.web.servlet;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;/*** 重定向*/@WebServlet("/responseDemo1")public class ResponseDemo1 extends HttpServlet {protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {System.out.println("demo1........");//访问/responseDemo1，会自动跳转到/responseDemo2资源/* //1. 设置状态码为302response.setStatus(302);//2.设置响应头locationresponse.setHeader("location","/day15/responseDemo2");*///动态获取虚拟目录String contextPath = request.getContextPath();//简单的重定向方法response.sendRedirect(contextPath+"/responseDemo2");//response.sendRedirect("");}protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {this.doPost(request,response);}}

重定向的特点:redirect

① 地址栏发生变化

② 重定向可以访问其他站点(服务器)的资源

③ 重定向是两次请求。不能使用request对象来共享数据

转发的特点：forward

① 转发地址栏路径不变

② 转发只能访问当前服务器下的资源

③ 转发是一次请求，可以使用request对象来共享数据

路径写法：

路径分类 相对路径：通过相对路径不可以确定唯一资源

如：./index.html

不以/开头，以.开头路径

规则：找到当前资源和目标资源之间的相对位置关系

./：当前目录…/：后退一级目录 绝对路径：通过绝对路径可以确定唯一资源

如：http://localhost/day15/responseDemo2 /day15/responseDemo2

以/开头的路径

规则：判断定义的路径是给谁用的？判断请求将来从哪儿发出

给客户端浏览器使用：需要加虚拟目录(项目的访问路径) 建议虚拟目录动态获取：request.getContextPath()<a> , <form>重定向… 给服务器使用：不需要加虚拟目录 转发路径

② 服务器输出字符数据到浏览器

6. 步骤：

① 获取字符输出流

② 输出数据

7. 注意：乱码问题

① PrintWriter pw = response.getWriter();获取的流的默认编码是ISO-8859-1② 设置该流的默认编码③ 告诉浏览器响应体使用的编码④ //简单的形式，设置编码，是在获取流之前设置```javaresponse.setContentType("text/html;charset=utf-8");```

代码

package cn.itcast.web.servlet;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.io.PrintWriter;@WebServlet("/responseDemo4")public class ResponseDemo4 extends HttpServlet {protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {//获取流对象之前，设置流的默认编码：ISO-8859-1 设置为：GBK// response.setCharacterEncoding("utf-8");//告诉浏览器，服务器发送的消息体数据的编码。建议浏览器使用该编码解码//response.setHeader("content-type","text/html;charset=utf-8");//简单的形式，设置编码response.setContentType("text/html;charset=utf-8");//1.获取字符输出流PrintWriter pw = response.getWriter();//2.输出数据//pw.write("<h1>hello response</h1>");pw.write("你好啊啊啊 response");}protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {this.doPost(request,response);}}

③ 服务器输出字节数据到浏览器

步骤：

① 获取字节输出流

② 输出数据

代码

package cn.itcast.web.servlet;import javax.servlet.ServletException;import javax.servlet.ServletOutputStream;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("/responseDemo5")public class ResponseDemo5 extends HttpServlet {protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {response.setContentType("text/html;charset=utf-8");//1.获取字节输出流ServletOutputStream sos = response.getOutputStream();//2.输出数据sos.write("你好".getBytes("utf-8"));}protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {this.doPost(request,response);}}

④ 验证码

JavaWeb：生成简单随机图片验证码返回给客户端

5. ServletContext

概念：代表整个web应用，可以和程序的容器(服务器)来通信

获取：

通过request对象获取

request.getServletContext();

通过HttpServlet获取

this.getServletContext();

package cn.itcast.web.servletcontext;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("/servletContextDemo1")public class ServletContextDemo1 extends HttpServlet {protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {/*ServletContext对象获取：1. 通过request对象获取request.getServletContext();2. 通过HttpServlet获取this.getServletContext();*///1. 通过request对象获取ServletContext context1 = request.getServletContext();//2. 通过HttpServlet获取ServletContext context2 = this.getServletContext();System.out.println(context1);System.out.println(context2);System.out.println(context1 == context2);//true}protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {this.doPost(request,response);}}

功能：

获取MIME类型：

MIME类型:在互联网通信过程中定义的一种文件数据类型

格式： 大类型/小类型 text/html image/jpeg

获取：String getMimeType(String file)

package cn.itcast.web.servletcontext;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("/servletContextDemo2")public class ServletContextDemo2 extends HttpServlet {protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {/*ServletContext功能：1. 获取MIME类型：* MIME类型:在互联网通信过程中定义的一种文件数据类型* 格式： 大类型/小类型 text/htmlimage/jpeg* 获取：String getMimeType(String file)2. 域对象：共享数据3. 获取文件的真实(服务器)路径*///2. 通过HttpServlet获取ServletContext context = this.getServletContext();//3. 定义文件名称String filename = "a.jpg";//image/jpeg//4.获取MIME类型String mimeType = context.getMimeType(filename);System.out.println(mimeType);}protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {this.doPost(request,response);}}

域对象：共享数据

setAttribute(String name,Object value)

getAttribute(String name)

removeAttribute(String name)

ServletContext对象范围：所有用户所有请求的数据

package cn.itcast.web.servletcontext;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("/servletContextDemo3")public class ServletContextDemo3 extends HttpServlet {protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {/*ServletContext功能：1. 获取MIME类型：2. 域对象：共享数据3. 获取文件的真实(服务器)路径*///2. 通过HttpServlet获取ServletContext context = this.getServletContext();//设置数据context.setAttribute("msg","haha");}protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {this.doPost(request,response);}}

package cn.itcast.web.servletcontext;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("/servletContextDemo4")public class ServletContextDemo4 extends HttpServlet {protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {/*ServletContext功能：1. 获取MIME类型：2. 域对象：共享数据3. 获取文件的真实(服务器)路径*///2. 通过HttpServlet获取ServletContext context = this.getServletContext();//获取数据Object msg = context.getAttribute("msg");System.out.println(msg);}protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {this.doPost(request,response);}}

获取文件的真实(服务器)路径

方法：String getRealPath(String path)

String b = context.getRealPath("/b.txt");//web目录下资源访问

System.out.println(b);

String c = context.getRealPath("/WEB-INF/c.txt");//WEB-INF目录下的资源访问

System.out.println©;

String a = context.getRealPath("/WEB-INF/classes/a.txt");//src目录下的资源访问

System.out.println(a);

package cn.itcast.web.servletcontext;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.File;import java.io.IOException;@WebServlet("/servletContextDemo5")public class ServletContextDemo5 extends HttpServlet {protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {/*ServletContext功能：1. 获取MIME类型：2. 域对象：共享数据3. 获取文件的真实(服务器)路径*/// 通过HttpServlet获取ServletContext context = this.getServletContext();// 获取文件的服务器路径String b = context.getRealPath("/b.txt");//web目录下资源访问System.out.println(b);// File file = new File(realPath);String c = context.getRealPath("/WEB-INF/c.txt");//WEB-INF目录下的资源访问System.out.println(c);String a = context.getRealPath("/WEB-INF/classes/a.txt");//src目录下的资源访问System.out.println(a);}protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {this.doPost(request,response);}}

6. 案例：文件下载