Servlet

一.服务器：装有服务器软件的计算机

数据库服务器：装有MySql软件的计算机。

Web服务器：装有Web服务器软件的计算机,用于接收请求,处理请求,响应请求。

二.http协议---超文本传输协议：1）浏览器往服务器发送 ---- 请求；2）服务器往浏览器回写 ---- 响应

1）请求(request)----请求行,请求头,请求体

1.请求行：请求信息的第一行（格式：请求方式<get和pos>  访问的资源   协议/版本     举例：GET /day0801/1.html HTTP/1.1）

2.请求头：请求信息的第二行到空行结束（格式：key/value (value可以是多个值)）

3.请求体:空行以下的内容（只有post才有请求体  get请求参数拼接在URL后面）

2）响应(response)---响应行 响应头 响应体 

1.响应行:响应信息的第一行（格式：协议/版本  状态码   状态码说明      例如：HTTP/1.1 200 OK）

状态码：200----正常响应成功；302----重定向；304----读缓存；404----用户操作资源不存在；500----服务器内部异常。

2.响应头:从响应信息的第二行到空行结束（格式：key/value(value可以是多个值)）  

3.响应体:空行以下的内容

三.Servlet

1）步骤：

（1）创建web项目
（2）定义一个Java类，实现Servlet接口
（3）重写所有未实现方法
（4）配置Servlet，在web.xml
 <!-- 配置Servlet，为了配置Servlet的访问路径 -->
 <servlet>
<servlet-name>demo1</servlet-name>
<servlet-class>org.westos.servlet.ServletDemo</servlet-class>
 </servlet>
  
 <servlet-mapping>
<servlet-name>demo1</servlet-name>
<!-- 设置访问路径，以/开头  -->
<url-pattern>/demo</url-pattern>
 </servlet-mapping>
（5）发布项目
（6）访问/demo路径访问该Servlet

2)Servlet中的五个需要被实现的方法

public class ServletDemo implements Servlet {// 当Servlet被创建时调用，而且只调用一次public void init(ServletConfig config) throws ServletException {System.out.println("Servlet被创建了");}// 对外提供服务的方法，每一次请求时都会调用该方法public void service(ServletRequest req, ServletResponse res)throws ServletException, IOException {System.out.println("请求来了");}// 获取配置对象public ServletConfig getServletConfig() {// TODO Auto-generated method stubreturn null;}// 获取Servleet版本，作者等信息public String getServletInfo() {// TODO Auto-generated method stubreturn null;}// 当Servlet被销毁时调用public void destroy() {System.out.println("Servlet被销毁了");}

3）ServletConfig--配置对象

/* * 让服务器一开始就进行初始化的方法: 再web.xml中配置---<load-on-startup>0</load-on-startup> * 它的默认值是-1,即在第一次请求时才调用init()方法,如果是非负整数 服务器开启时就会调用 init()方法 */public void init(ServletConfig config) throws ServletException {// ServletConfig--配置对象:是一个接口,子类对象由服务器创建,当服务器调用init()方法时作为参数传递// 配置对象的作用:// 1.获取web.xml中配置的初始化参数// 方式一:config.getInitParameter(name)String name = config.getInitParameter("username");System.out.println(name);String age = config.getInitParameter("age");System.out.println(age);System.out.println("--------------------------");// 方式二: config.getInitParameterNames()Enumeration<String> values = config.getInitParameterNames();while (values.hasMoreElements()) {String key = values.nextElement();String value = config.getInitParameter(key);System.out.println(value);}}

public void init(ServletConfig config) throws ServletException {// ServletConfig--配置对象// 作用2:获取全局域对象:config.getServletContext()// ServletContext--全局上下文对象(一个域<域:范围>对象):是一个接口,他的子类对象由服务器创建ServletContext context = config.getServletContext();// 在域中存储数据context.setAttribute("num", "100");// 获取域中的数据String value = (String) context.getAttribute("num");// 100// 清除域中的数据context.removeAttribute("num");// 获取域中的数据String value2 = (String) context.getAttribute("num");// nullSystem.out.println(value);// 100System.out.println(value2);// null// 作用3:获取Web.xml 配置的Servlet的名字 :config.getServletName()String name = config.getServletName();System.out.println(name);// myDemo2}

4）ServletContext---

全局上下文对象(一个域<域:范围>对象)

ServletConfig config;// 单例的// 在Servlet 最好不要定义成员变量 因为会有线程安全问题的存在// final int num=100;public void init(ServletConfig config) throws ServletException {this.config = config;}public ServletConfig getServletConfig() {// TODO Auto-generated method stubreturn config;}public void service(ServletRequest req, ServletResponse res)throws ServletException, IOException {// ServletContext作用:// 1.在域中的资源间共享数据// 2.用来获取服务器的真实路径// //读取a.txt(在WEB-INF目录下)// File file = new File(// "D:\\tomcat\\apache-tomcat-7.0.26\\webapps\\ServletDemo2\\WEB-INF\\a.txt");// FileInputStream in = new FileInputStream(file);// // 读取b.txt(WEB-Root目录下)// File file2 = new File(// "D:\\tomcat\\apache-tomcat-7.0.26\\webapps\\ServletDemo2\\b.txt");// FileInputStream in2 = new FileInputStream(file2);//// // 读取c.txt(src目录下) \\WEB-INF\\classes\\c.txt// File file3 = new File(// "D:\\tomcat\\apache-tomcat-7.0.26\\webapps\\ServletDemo2\\WEB-INF\\classes\\c.txt");// FileInputStream in3 = new FileInputStream(file3);//// System.out.println(in);// System.out.println(in2);// System.out.println(in3);// 动态获取服务器的真实路径ServletConfig config2 = this.getServletConfig();ServletContext context = config.getServletContext();String realPath = context.getRealPath("/");System.out.println(realPath);//D:\tomcat\apache-tomcat-7.0.26\webapps\ServletDemo2\// 读取a.txtFile file1 = new File(context.getRealPath("/WEB-INF/a.txt"));// 读取b.txtFile file2 = new File(context.getRealPath("/b.txt"));// 读取c.txtFile file3 = new File(context.getRealPath("/WEB-INF/classes/c.txt"));System.out.println(file1);//D:\tomcat\apache-tomcat-7.0.26\webapps\ServletDemo2\WEB-INF\a.txtSystem.out.println(file2);//D:\tomcat\apache-tomcat-7.0.26\webapps\ServletDemo2\b.txtSystem.out.println(file3);//D:\tomcat\apache-tomcat-7.0.26\webapps\ServletDemo2\WEB-INF\classes\c.txt// 调用工具类 读取文件 MyUtil.readFile();}

四.GenericServlet--适配器（实现了Servletjie接口）

public class ServletDemo extends GenericServlet {// 适配器@Overridepublic void service(ServletRequest req, ServletResponse res)throws ServletException, IOException {ServletContext context = this.getServletContext();ServletConfig config2 = this.getServletConfig();ServletContext context2 = config2.getServletContext();}}

五.HttpServlet(继承了GenericServlet，重写了service()方法)

public class ServletDemo2 extends HttpServlet {@Overrideprotected void doGet(HttpServletRequest req, HttpServletResponse resp)throws ServletException, IOException {System.out.println("get请求来了");}@Overrideprotected void doPost(HttpServletRequest req, HttpServletResponse resp)throws ServletException, IOException {this.doGet(req, resp);System.out.println("post请求来了");}}

 1）响应对象

public void doGet(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {/* * request 请求对象 ; response 响应对象 请求对象和响应对象直接由服务器创建管理和销毁 */// PrintWriter writer = response.getWriter();// writer.write("hello");// writer.write("你好");//??// 为了防止乱码,设置服务器对字符流的编码，默认服务器用的是ISO-8859-1// response.setCharacterEncoding("utf-8");// 告诉浏览器用相应的编码去解码// response.setHeader("content-type", "text/html; charset=utf-8");// 以上两行代码合并// 设置字符打印输出流的编码,并告诉浏览器用相应的编码去解码response.setContentType("text/html; charset=utf-8");// 获取发送字符数据的对象PrintWriter writer = response.getWriter();writer.write("你好");}public void doPost(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {this.doGet(request, response);}

public void doGet(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {// 获取图片路径String path = this.getServletContext().getRealPath("/girl.jpg");FileInputStream fis = new FileInputStream(new File(path));// 获取响应对象中的字节输出流ServletOutputStream fos = response.getOutputStream();// 读写操作// byte[] bys = new byte[1024];// int len = 0;// while ((len = fis.read(bys)) != -1) {// fos.write(bys, 0, len);// }IOUtils.copy(fis, fos);// 释放资源fos.close();fis.close();}

//重定向/* *重定向的特点：页面跳转 *1.两次请求，两次响应 *2.地址栏会发生变化 *3.可以跳转到外部站点的资源，也可以跳转到内部站点的资源 * */public class ServletDemo extends HttpServlet {public void doGet(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {/* * //设置状态码 * response.setStatus(302);  * //通过Http协议中的响应头告诉浏览器重定向的位置 * response.setHeader("location", "http://www.baidu.com");//跳到外部站点 * response.setHeader("location", "/ServletDemo4/demo2");//跳到内部站点 *///以上两步合并response.sendRedirect("http://www.baidu.com");}public void doPost(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {this.doGet(request, response);}}

2）请求对象

//请求对象request 由服务器创建，管理，和销毁 用来封装请求消息public class ServletDemo2 extends HttpServlet {public void doGet(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {// 获取请求方法String method = request.getMethod();// GET// 获取URI--统一资源标识符String uri = request.getRequestURI();// /ServletDemo4/demo2// 获取URL--统一资源定位符StringBuffer url = request.getRequestURL();// http://localhost:8080/ServletDemo4/demo2// 获取协议版本String protocol = request.getProtocol();// HTTP/1.1System.out.println(method);System.out.println(uri);System.out.println(url);System.out.println(protocol);// 获取ipString ip = request.getRemoteAddr();// 获取主机名String host = request.getRemoteHost();// 获取端口int port = request.getRemotePort();System.out.println(ip);System.out.println(host);System.out.println(port);String header = request.getHeader("user-agent");// 获取请求头System.out.println(header);// Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML,// like Gecko) Chrome/51.0.2704.79 Safari/537.36 Edge/14.14393}public void doPost(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {this.doGet(request, response);}}

//处理get和post请求public class ServletDemo3 extends HttpServlet {// 处理get请求--get请求参数拼接在URL后面public void doGet(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {String line = request.getQueryString();// 通过request.getQueryString()获取出来的请求参数经过了浏览器的URLEncode()编码System.out.println(line);// usename=%E5%BC%A0%E4%B8%89&password=12345// 通过URLDecode解码line = URLDecoder.decode(line, "utf-8");System.out.println(line);// usename=张三&password=124567}//处理post请求--post请求把请求参数封装在请求体里面public void doPost(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {String line = request.getReader().readLine();System.out.println(line);//usename=%E5%BC%A0%E4%B8%89&password=12345line = URLDecoder.decode(line, "utf-8");System.out.println(line);//usename=张三&password=12345}}

//this.doGet(request, response)的由来public class ServletDemo4 extends HttpServlet {public void doGet(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {getParment(request, response);}public void doPost(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException { this.doGet(request, response);//getParment(request, response);}private void getParment(HttpServletRequest request,HttpServletResponse response) throws IOException  {String method = request.getMethod();String line = null;if ("get".equals(method)) {line = request.getQueryString();} else if ("post".equals(method)) {line = request.getReader().readLine();}String[] split = line.split("&");String[] split2 = split[0].split("=");String ukey = split2[0];String uvalue = split2[1];String[] split3 = split[1].split("=");String pkey = split3[0];String pvalue = split3[1];}}

public void doGet(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {// 处理中文乱码的方式(只针对post请求)//request.setCharacterEncoding("utf-8");String username = request.getParameter("username");String password = request.getParameter("password");//System.out.println(username + "---" + password);//??????---12345// 处理中文乱码的方式(get/post请求均可用)// byte[] bytes = username.getBytes("Iso-8859-1");// username = new String(bytes, "utf-8");System.out.println(username + "---" + password);}

public class ServletDemo6 extends HttpServlet {public void doGet(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {//设置编码request.setCharacterEncoding("utf-8");response.setContentType("text/html;charset=utf-8");//获取请求参数//方式一:String username = request.getParameter("username");String password = request.getParameter("password");//复选框String[] values = request.getParameterValues("hobby");for(String v:values){System.out.println(v);}//方式二:将请求参数的值和键全部封装进Map集合中Map<String,String[]> map = request.getParameterMap();Set<String> keySet = map.keySet();for(String key:keySet){String[] values2 = map.get(key);for(String v:values2){System.out.println(key+"---"+v);}}//方式三Enumeration<String> names = request.getParameterNames();while (names.hasMoreElements()) {String key = names.nextElement();String v = request.getParameter(key);System.out.println(v);}}

//请求转发/*特点: * 1.地址栏不发生变化 *2.一次请求一次响应 *3.只能请求内部站点的资源 * */public class ServletDemo7 extends HttpServlet {public void doGet(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {request.getRequestDispatcher("/demo2").forward(request, response);}public void doPost(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {this.doGet(request, response);}}

六.验证码小案例

//制作一个验证码public class ServletDemo5 extends HttpServlet {public void doGet(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {String str = "";// 创建一个图片对象(参三--图片类型)int width = 150;int height = 60;BufferedImage img = new BufferedImage(width, height,BufferedImage.TYPE_INT_RGB);// -------美化图片部分-------// 获取画笔Graphics g = img.getGraphics();// 设置画笔的颜色g.setColor(Color.CYAN);// 填充背景g.fillRect(0, 0, width, height);// 设置边框g.setColor(Color.BLUE);g.drawRect(0, 0, width - 1, height - 1);// ------图片添加文字-------g.setColor(Color.black);String msg = "abcdefghigklmnopqrstuvwxyzABCDEFGHIGKLMNOPQRSTUVWXYZ0123456789";// 随机获取四个字符Random random = new Random();for (int i = 1; i <= 4; i++) {// 获取随机角标int index = random.nextInt(msg.length());// 获取随机角标对应的字符char ch = msg.charAt(index);str = str + ch;// 给图片添加文字g.drawString(ch + "", width / 5 * i, height / 2);}System.out.println(str);// ------添加干扰线-----g.setColor(Color.RED);for (int i = 0; i < 5; i++) {// 获取四个随机坐标int x1 = random.nextInt(width);int x2 = random.nextInt(width);int y1 = random.nextInt(height);int y2 = random.nextInt(height);g.drawLine(x1, y1, x2, y2);}ImageIO.write(img, "jpg", response.getOutputStream());}public void doPost(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {this.doGet(request, response);}}

My.html

 <body>   <img src="/ServletDemo/demo5" id="yzm" /><a href="javascript:void(0)" onclick="change()">看不清换一张</a></body><script type="text/javascript">function change() {document.getElementById("yzm").src = "/ServletDemo3/demo5?imgpath="+ new Date().getTime();}</script>