把实现了Servlet接口的Java程序叫做,Servlet
Serlvet接口Sun公司有两个默认的实现类:HttpServlet,GenericServlet
构建一个普通的Maven项目,删掉里面的src目录,以后我们的学习就在这个项目里面建立Moudel;这个空的工程就是Maven主工程;
关于Maven父子工程的理解:
父项目中会有
<modules>
<module>servlet-01module>
modules>
子项目会有
<parent>
<artifactId>javaweb-02-servletartifactId>
<groupId>com.kuanggroupId>
<version>1.0-SNAPSHOTversion>
parent>
父项目中的java子项目可以直接使用
son extends father
Maven环境优化
编写一个Servlet程序
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编写一个普通类
实现Servlet接口,这里我们直接继承HttpServlet
public class HelloServlet extends HttpServlet {
//由于get或者post只是请求实现的不同的方式,可以相互调用,业务逻辑都一样;
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
//ServletOutputStream outputStream = resp.getOutputStream();
PrintWriter writer = resp.getWriter(); //响应流
writer.print("Hello,Serlvet");
}
@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
doGet(req, resp);
}
}
编写Servlet的映射
为什么需要映射:我们写的是JAVA程序,但是要通过浏览器访问,而浏览器需要连接web服务器,所以我们需要再web服务中注册我们写的Servlet,还需给他一个浏览器能够访问的路径;
<servlet>
<servlet-name>helloservlet-name>
<servlet-class>com.kuang.servlet.HelloServletservlet-class>
servlet>
<servlet-mapping>
<servlet-name>helloservlet-name>
<url-pattern>/hellourl-pattern>
servlet-mapping>
配置Tomcat
注意:配置项目发布的路径就可以了
启动测试,OK!
Servlet是由Web服务器调用,web服务器在收到浏览器请求之后,会:
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一个Servlet可以指定一个映射路径
<servlet-mapping>
<servlet-name>helloservlet-name>
<url-pattern>/hellourl-pattern>
servlet-mapping>
一个Servlet可以指定多个映射路径
<servlet-mapping>
<servlet-name>helloservlet-name>
<url-pattern>/hellourl-pattern>
servlet-mapping>
<servlet-mapping>
<servlet-name>helloservlet-name>
<url-pattern>/hello2url-pattern>
servlet-mapping>
<servlet-mapping>
<servlet-name>helloservlet-name>
<url-pattern>/hello3url-pattern>
servlet-mapping>
<servlet-mapping>
<servlet-name>helloservlet-name>
<url-pattern>/hello4url-pattern>
servlet-mapping>
<servlet-mapping>
<servlet-name>helloservlet-name>
<url-pattern>/hello5url-pattern>
servlet-mapping>
一个Servlet可以指定通用映射路径
<servlet-mapping>
<servlet-name>helloservlet-name>
<url-pattern>/hello/*url-pattern>
servlet-mapping>
默认请求路径
<servlet-mapping>
<servlet-name>helloservlet-name>
<url-pattern>/*url-pattern>
servlet-mapping>
指定一些后缀或者前缀等等….
<servlet-mapping>
<servlet-name>helloservlet-name>
<url-pattern>*.qinjiangurl-pattern>
servlet-mapping>
优先级问题
指定了固有的映射路径优先级最高,如果找不到就会走默认的处理请求;
<servlet>
<servlet-name>errorservlet-name>
<servlet-class>com.kuang.servlet.ErrorServletservlet-class>
servlet>
<servlet-mapping>
<servlet-name>errorservlet-name>
<url-pattern>/*url-pattern>
servlet-mapping>
web容器在启动的时候,它会为每个web程序都创建一个对应的ServletContext对象,它代表了当前的web应用;
我在这个Servlet中保存的数据,可以在另外一个servlet中拿到;
public class HelloServlet extends HttpServlet {
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
//this.getInitParameter() 初始化参数
//this.getServletConfig() Servlet配置
//this.getServletContext() Servlet上下文
ServletContext context = this.getServletContext();
String username = "秦疆"; //数据
context.setAttribute("username",username); //将一个数据保存在了ServletContext中,名字为:username 。值 username
}
}
public class GetServlet extends HttpServlet {
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
ServletContext context = this.getServletContext();
String username = (String) context.getAttribute("username");
resp.setContentType("text/html");
resp.setCharacterEncoding("utf-8");
resp.getWriter().print("名字"+username);
}
@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
doGet(req, resp);
}
}
hello
com.kuang.servlet.HelloServlet
hello
/hello
getc
com.kuang.servlet.GetServlet
getc
/getc
测试访问结果;
<context-param>
<param-name>urlparam-name>
<param-value>jdbc:mysql://localhost:3306/mybatisparam-value>
context-param>
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
ServletContext context = this.getServletContext();
String url = context.getInitParameter("url");
resp.getWriter().print(url);
}
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
ServletContext context = this.getServletContext();
System.out.println("进入了ServletDemo04");
//RequestDispatcher requestDispatcher = context.getRequestDispatcher("/gp"); //转发的请求路径
//requestDispatcher.forward(req,resp); //调用forward实现请求转发;
context.getRequestDispatcher("/gp").forward(req,resp);
}
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Properties
发现:都被打包到了同一个路径下:classes,我们俗称这个路径为classpath:
思路:需要一个文件流;
username=root12312
password=zxczxczxc
public class ServletDemo05 extends HttpServlet {
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
InputStream is = this.getServletContext().getResourceAsStream("/WEB-INF/classes/com/kuang/servlet/aa.properties");
Properties prop = new Properties();
prop.load(is);
String user = prop.getProperty("username");
String pwd = prop.getProperty("password");
resp.getWriter().print(user+":"+pwd);
}
@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
doGet(req, resp);
}
}
访问测试即可ok;
web服务器接收到客户端的http请求,针对这个请求,分别创建一个代表请求的HttpServletRequest对象,代表响应的一个HttpServletResponse;
负责向浏览器发送数据的方法
ServletOutputStream getOutputStream() throws IOException;
PrintWriter getWriter() throws IOException;
负责向浏览器发送响应头的方法
void setCharacterEncoding(String var1);
void setContentLength(int var1);
void setContentLengthLong(long var1);
void setContentType(String var1);
void setDateHeader(String var1, long var2);
void addDateHeader(String var1, long var2);
void setHeader(String var1, String var2);
void addHeader(String var1, String var2);
void setIntHeader(String var1, int var2);
void addIntHeader(String var1, int var2);
响应的状态码
int SC_CONTINUE = 100;
int SC_SWITCHING_PROTOCOLS = 101;
int SC_OK = 200;
int SC_CREATED = 201;
int SC_ACCEPTED = 202;
int SC_NON_AUTHORITATIVE_INFORMATION = 203;
int SC_NO_CONTENT = 204;
int SC_RESET_CONTENT = 205;
int SC_PARTIAL_CONTENT = 206;
int SC_MULTIPLE_CHOICES = 300;
int SC_MOVED_PERMANENTLY = 301;
int SC_MOVED_TEMPORARILY = 302;
int SC_FOUND = 302;
int SC_SEE_OTHER = 303;
int SC_NOT_MODIFIED = 304;
int SC_USE_PROXY = 305;
int SC_TEMPORARY_REDIRECT = 307;
int SC_BAD_REQUEST = 400;
int SC_UNAUTHORIZED = 401;
int SC_PAYMENT_REQUIRED = 402;
int SC_FORBIDDEN = 403;
int SC_NOT_FOUND = 404;
int SC_METHOD_NOT_ALLOWED = 405;
int SC_NOT_ACCEPTABLE = 406;
int SC_PROXY_AUTHENTICATION_REQUIRED = 407;
int SC_REQUEST_TIMEOUT = 408;
int SC_CONFLICT = 409;
int SC_GONE = 410;
int SC_LENGTH_REQUIRED = 411;
int SC_PRECONDITION_FAILED = 412;
int SC_REQUEST_ENTITY_TOO_LARGE = 413;
int SC_REQUEST_URI_TOO_LONG = 414;
int SC_UNSUPPORTED_MEDIA_TYPE = 415;
int SC_REQUESTED_RANGE_NOT_SATISFIABLE = 416;
int SC_EXPECTATION_FAILED = 417;
int SC_INTERNAL_SERVER_ERROR = 500;
int SC_NOT_IMPLEMENTED = 501;
int SC_BAD_GATEWAY = 502;
int SC_SERVICE_UNAVAILABLE = 503;
int SC_GATEWAY_TIMEOUT = 504;
int SC_HTTP_VERSION_NOT_SUPPORTED = 505;
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
// 1. 要获取下载文件的路径
String realPath = "F:\\班级管理\\西开【19525】\\2、代码\\JavaWeb\\javaweb-02-servlet\\response\\target\\classes\\秦疆.png";
System.out.println("下载文件的路径:"+realPath);
// 2. 下载的文件名是啥?
String fileName = realPath.substring(realPath.lastIndexOf("\\") + 1);
// 3. 设置想办法让浏览器能够支持(Content-Disposition)下载我们需要的东西,中文文件名URLEncoder.encode编码,否则有可能乱码
resp.setHeader("Content-Disposition","attachment;filename="+URLEncoder.encode(fileName,"UTF-8"));
// 4. 获取下载文件的输入流
FileInputStream in = new FileInputStream(realPath);
// 5. 创建缓冲区
int len = 0;
byte[] buffer = new byte[1024];
// 6. 获取OutputStream对象
ServletOutputStream out = resp.getOutputStream();
// 7. 将FileOutputStream流写入到buffer缓冲区,使用OutputStream将缓冲区中的数据输出到客户端!
while ((len=in.read(buffer))>0){
out.write(buffer,0,len);
}
in.close();
out.close();
}
验证怎么来的?
package com.kuang.servlet;
import javax.imageio.ImageIO;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.awt.*;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.util.Random;
public class ImageServlet extends HttpServlet {
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
//如何让浏览器3秒自动刷新一次;
resp.setHeader("refresh","3");
//在内存中创建一个图片
BufferedImage image = new BufferedImage(80,20,BufferedImage.TYPE_INT_RGB);
//得到图片
Graphics2D g = (Graphics2D) image.getGraphics(); //笔
//设置图片的背景颜色
g.setColor(Color.white);
g.fillRect(0,0,80,20);
//给图片写数据
g.setColor(Color.BLUE);
g.setFont(new Font(null,Font.BOLD,20));
g.drawString(makeNum(),0,20);
//告诉浏览器,这个请求用图片的方式打开
resp.setContentType("image/jpeg");
//网站存在缓存,不让浏览器缓存
resp.setDateHeader("expires",-1);
resp.setHeader("Cache-Control","no-cache");
resp.setHeader("Pragma","no-cache");
//把图片写给浏览器
ImageIO.write(image,"jpg", resp.getOutputStream());
}
//生成随机数
private String makeNum(){
Random random = new Random();
String num = random.nextInt(9999999) + "";
StringBuffer sb = new StringBuffer();
for (int i = 0; i < 7-num.length() ; i++) {
sb.append("0");
}
num = sb.toString() + num;
return num;
}
@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
doGet(req, resp);
}
}
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B一个web资源收到客户端A请求后,B他会通知A客户端去访问另外一个web资源C,这个过程叫重定向
常见场景:
void sendRedirect(String var1) throws IOException;
测试:
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
/*
resp.setHeader("Location","/r/img");
resp.setStatus(302);
*/
resp.sendRedirect("/r/img");//重定向
}
面试题:请你聊聊重定向和转发的区别?
相同点
不同点
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<%--这里提交的路径,需要寻找到项目的路径--%>
<%--${pageContext.request.contextPath}代表当前的项目--%>
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
//处理请求
String username = req.getParameter("username");
String password = req.getParameter("password");
System.out.println(username+":"+password);
//重定向时候一定要注意,路径问题,否则404;
resp.sendRedirect("/r/success.jsp");
}
<servlet>
<servlet-name>requsetservlet-name>
<servlet-class>com.kuang.servlet.RequestTestservlet-class>
servlet>
<servlet-mapping>
<servlet-name>requsetservlet-name>
<url-pattern>/loginurl-pattern>
servlet-mapping>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
Title
Success
HttpServletRequest代表客户端的请求,用户通过Http协议访问服务器,HTTP请求中的所有信息会被封装到HttpServletRequest,通过这个HttpServletRequest的方法,获得客户端的所有信息;
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)]
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)]
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@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
req.setCharacterEncoding("utf-8");
resp.setCharacterEncoding("utf-8");
String username = req.getParameter("username");
String password = req.getParameter("password");
String[] hobbys = req.getParameterValues("hobbys");
System.out.println("=============================");
//后台接收中文乱码问题
System.out.println(username);
System.out.println(password);
System.out.println(Arrays.toString(hobbys));
System.out.println("=============================");
System.out.println(req.getContextPath());
//通过请求转发
//这里的 / 代表当前的web应用
req.getRequestDispatcher("/success.jsp").forward(req,resp);
}
面试题:请你聊聊重定向和转发的区别?
相同点
不同点
会话:用户打开一个浏览器,点击了很多超链接,访问多个web资源,关闭浏览器,这个过程可以称之为会话;
有状态会话:一个同学来过教室,下次再来教室,我们会知道这个同学,曾经来过,称之为有状态会话;
你能怎么证明你是西开的学生?
你 西开
一个网站,怎么证明你来过?
客户端 服务端
cookie
session
常见常见:网站登录之后,你下次不用再登录了,第二次访问直接就上去了!
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)]
Cookie[] cookies = req.getCookies(); //获得Cookie
cookie.getName(); //获得cookie中的key
cookie.getValue(); //获得cookie中的vlaue
new Cookie("lastLoginTime", System.currentTimeMillis()+""); //新建一个cookie
cookie.setMaxAge(24*60*60); //设置cookie的有效期
resp.addCookie(cookie); //响应给客户端一个cookie
cookie:一般会保存在本地的 用户目录下 appdata;
一个网站cookie是否存在上限!聊聊细节问题
删除Cookie;
编码解码:
URLEncoder.encode("秦疆","utf-8")
URLDecoder.decode(cookie.getValue(),"UTF-8")
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)]
什么是Session:
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Session和cookie的区别:
使用场景:
使用Session:
package com.kuang.servlet;
import com.kuang.pojo.Person;
import javax.servlet.ServletException;
import javax.servlet.http.*;
import java.io.IOException;
public class SessionDemo01 extends HttpServlet {
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
//解决乱码问题
req.setCharacterEncoding("UTF-8");
resp.setCharacterEncoding("UTF-8");
resp.setContentType("text/html;charset=utf-8");
//得到Session
HttpSession session = req.getSession();
//给Session中存东西
session.setAttribute("name",new Person("秦疆",1));
//获取Session的ID
String sessionId = session.getId();
//判断Session是不是新创建
if (session.isNew()){
resp.getWriter().write("session创建成功,ID:"+sessionId);
}else {
resp.getWriter().write("session以及在服务器中存在了,ID:"+sessionId);
}
//Session创建的时候做了什么事情;
// Cookie cookie = new Cookie("JSESSIONID",sessionId);
// resp.addCookie(cookie);
}
@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
doGet(req, resp);
}
}
//得到Session
HttpSession session = req.getSession();
Person person = (Person) session.getAttribute("name");
System.out.println(person.toString());
HttpSession session = req.getSession();
session.removeAttribute("name");
//手动注销Session
session.invalidate();
会话自动过期:web.xml配置
<session-config>
<session-timeout>15session-timeout>
session-config>
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)]