JavaWeb

JavaWeb

1.Servlet

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns="http://xmlns.jcp.org/xml/ns/javaee"xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaeehttp://xmlns.jcp.org/xml/ns/javaee/web-app_4_0.xsd"version="4.0"metadata-complete="true"><!--注册Servlet--><servlet><servlet-name>hello</servlet-name><servlet-class>com.jf.servlet.HelloServlet</servlet-class></servlet><!--Servlet的请求路径--><servlet-mapping><servlet-name>hello</servlet-name><url-pattern>/hello</url-pattern></servlet-mapping><servlet><servlet-name>error</servlet-name><servlet-class>com.jf.servlet.ErrorServlet</servlet-class><!--可以自定义后缀实现请求映射，注意*前面不能加项目映射的路径--><!--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-mapping><servlet-name>error</servlet-name><url-pattern>/*</url-pattern></servlet-mapping>
</web-app>

package com.jf.servlet;import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.io.PrintWriter;public class ErrorServlet extends HttpServlet {@Overrideprotected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {resp.setContentType("text/html");resp.setCharacterEncoding("utf-8");PrintWriter writer = resp.getWriter();writer.print("<h1>404</h1>");}@Overrideprotected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {super.doPost(req, resp);}
}

//
// Source code recreated from a .class file by IntelliJ IDEA
// (powered by FernFlower decompiler)
//package com.jf.servlet;import java.io.IOException;
import java.io.PrintWriter;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;public class HelloServlet extends HttpServlet {public HelloServlet() {}protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {System.out.println("进入doGet方法");PrintWriter writer = resp.getWriter();writer.print("Hello,Servlet");}protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {super.doPost(req, resp);}
}

2.ServletContext

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:

1.共享数据

我在这个Servet中保存的数据，可以在另外一个servlet中拿到:

package com.jf.servlet;import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;public class HelloServlet extends HttpServlet {@Overrideprotected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {ServletContext context = this.getServletContext();String username="张飞";//数据context.setAttribute("username",username);//将一个数据保存在了ServletContext中，名字为;username，值username}
}

package com.jf.servlet;import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;public class GetServlet extends HttpServlet {@Overrideprotected 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);}@Overrideprotected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {doGet(req, resp);}
}

<servlet><servlet-name>hello</servlet-name><servlet-class>com.jf.servlet.HelloServlet</servlet-class></servlet><servlet-mapping><servlet-name>hello</servlet-name><url-pattern>/hello</url-pattern></servlet-mapping>
<servlet><servlet-name>getc</servlet-name><servlet-class>com.jf.servlet.GetServlet</servlet-class>
</servlet>
<servlet-mapping><servlet-name>getc</servlet-name><url-pattern>/getc</url-pattern>
</servlet-mapping>

2.获取初始化参数

<!--配置一些web应用初始化参数-->
<context-param><param-name>url</param-name><param-value>jdbc:mysql://localhost:3306/mybatis</param-value>
</context-param>

package com.jf.servlet;import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;public class ServletDemo03 extends HttpServlet {@Overrideprotected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {ServletContext context = this.getServletContext();String url = context.getInitParameter("url");resp.getWriter().print(url);}@Overrideprotected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {doGet(req, resp);}
}

<servlet><servlet-name>gp</servlet-name><servlet-class>com.jf.servlet.ServletDemo03</servlet-class>
</servlet>
<servlet-mapping><servlet-name>gp</servlet-name><url-pattern>/gp</url-pattern>
</servlet-mapping>

3.请求转发

package com.jf.servlet;import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;public class ServletDemo04 extends HttpServlet {@Overrideprotected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {ServletContext context = this.getServletContext();context.getRequestDispatcher("/gp").forward(req,resp);//请求转发}@Overrideprotected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {doGet(req, resp);}
}

<servlet><servlet-name>sd4</servlet-name><servlet-class>com.jf.servlet.ServletDemo04</servlet-class>
</servlet>
<servlet-mapping><servlet-name>sd4</servlet-name><url-pattern>/sd4</url-pattern>
</servlet-mapping>

4.读取资源文件

Properties
在java日录下新建properties
在resources日录下新建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:

maven由于他的约定大于配置，我们之后可以能遇到我们写的配置文件，无法被导出或者生效的问题，解决方案:

需要一个文件流

username=root
password=123456

<!--在build中配置resources，来防止资源导出失败的问题-->
<build><resources><resource><directory>src/main/resources</directory><includes><include>**/*.properties</include><include>**/*.xml</include></includes><filtering>true</filtering></resource><resource><directory>src/main/java</directory><includes><include>**/*.properties</include><include>**/*.xml</include></includes><filtering>true</filtering></resource></resources>
</build>

package com.jf.servlet;import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.io.InputStream;
import java.util.Properties;public class ServletDemo05 extends HttpServlet {@Overrideprotected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {InputStream is = this.getServletContext().getResourceAsStream("/WEB-INF/classes/db.properties");Properties prop = new Properties();prop.load(is);String user = prop.getProperty("username");String pwd = prop.getProperty("password");resp.getWriter().print(user+":"+pwd);}@Overrideprotected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {doGet(req, resp);}
}

<servlet><servlet-name>sd5</servlet-name><servlet-class>com.jf.servlet.ServletDemo05</servlet-class>
</servlet>
<servlet-mapping><servlet-name>sd5</servlet-name><url-pattern>/sd5</url-pattern>
</servlet-mapping>

3.HttpServletResponse

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。
如果要获取客户端请求过来的参数:找HttpServletRequest

如果要给客户端响应一些信息:找HttpServletResponse

1.下载文件

package com.jf.servlet;import javax.servlet.ServletException;
import javax.servlet.ServletOutputStream;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.FileInputStream;
import java.io.IOException;
import java.net.URLEncoder;public class FileServlet extends HttpServlet {@Overrideprotected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
//        1.要获取下载文件的路径String realPath = "D:\\code\\maven\\java-14-maven\\response\\src\\main\\resources\\zhangsan.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();}@Overrideprotected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {doGet(req, resp);}
}

<servlet><servlet-name>filedown</servlet-name><servlet-class>com.jf.servlet.FileServlet</servlet-class></servlet>
<servlet-mapping><servlet-name>filedown</servlet-name><url-pattern>/down</url-pattern>
</servlet-mapping>

2.验证码功能

package com.jf.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 {@Overrideprotected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {//如何让浏览器5秒刷新一次resp.setHeader("refresh","5");//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/jpg");//浏览器有缓存，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;}@Overrideprotected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {doGet(req, resp);}
}

<servlet><servlet-name>ImageServlet</servlet-name><servlet-class>com.jf.servlet.ImageServlet</servlet-class>
</servlet>
<servlet-mapping><servlet-name>ImageServlet</servlet-name><url-pattern>/img</url-pattern>
</servlet-mapping>

3.重定向

B一个web资源收到客户端A请求后，B会通知A客户端去访问另外一个web资源C，这个过程就叫重定向

常见场景：

• 用户登录

void sendRedirect(String var1) throws IOException;

测试：

package com.jf.servlet;import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;public class RedirectServlet extends HttpServlet {@Overrideprotected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
//       resp.setHeader(" Location","/response_war/img");
//       resp.setStatus(302);resp.sendRedirect("/response_war/img");}@Overrideprotected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {doGet(req, resp);}
}

重定向和转发的不同点：

• 相同点：

  页面都会跳转

• 不同点：

​ 请求转发的url不会发生变化

​ 重定向时候，url地址栏会发生变化

Demo:

package com.jf.servlet;import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;public class Request extends HttpServlet {@Overrideprotected 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);//重定向时候一定注意，路径问题，否则出现404resp.sendRedirect("/response_war/success.jsp");}@Overrideprotected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {doGet(req, resp);}
}

<html>
<body>
<!--这里提交的路径，需要寻找项目的路径-->
<%--${pageContext.request.contextPath}代表当前的项目--%>
<h2>Hello World!</h2>
<form action="${pageContext.request.contextPath}/login" method="get">用户名：<input type="text" name="username"><br>密码：<input type="password" name="password"><br><input type="submit">
</form>
</body>
</html>

<%--Created by IntelliJ IDEA.User: hjfDate: 2024/8/19Time: 16:50To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head><title>Title</title><h1>Success</h1>
</head>
<body></body>
</html>

4.HttpServletRequest

HttpServletRequest代表客户端的请求，用户通过http协议访问服务器，HTTP请求中的所有的信息会被封装到HttpServletRequest，通过这个HttpServletRequest方法，获得客户端的所有信息。

获取参数，请求转发：

package com.jf.servlet;import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.lang.reflect.Array;
import java.util.Arrays;public class LoginServlet extends HttpServlet {@Overrideprotected 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[] hobbies = req.getParameterValues("hobbies");System.out.println("===============");System.out.println(username);System.out.println(password);System.out.println(Arrays.toString(hobbies));System.out.println("======================");//通过请求转发//这里的/代表当前的web应用req.getRequestDispatcher("/success.jsp").forward(req,resp);}@Overrideprotected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {doGet(req, resp);}
}

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head><title>登录</title>
</head>
<body>
<div><form action="${pageContext.request.contextPath}/login" method="post">用户名：<input type="text" name="username"><br>密码：<input type="password" name="password"><br>爱好：<input type="checkbox" name="hobbies" value="电影">电影<input type="checkbox" name="hobbies" value="代码">代码<input type="checkbox" name="hobbies" value="旅游">旅游<input type="checkbox" name="hobbies" value="独处">独处<br><input type="submit"></form>
</div>
</body>
</html>

<%--Created by IntelliJ IDEA.User: hjfDate: 2024/8/19Time: 17:33To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head><title>Title</title>
</head>
<body>
<h1>登录成功</h1>
</body>
</html>

5.Cookie Session

5.1 保存回话的两种技术

cookie

• 客户端技术（响应，请求）

session

• 服务端技术，利用这个技术，可以保存用户的会话信息

5.2 cookie

1.从请求中拿到cookie信息

2.服务器响应给客户端cookie

• 一个Cookie只能保存一个信息
• 一个web站点可以给浏览器发送多个cookie，最多可以保存20个cookie
• Cookie大小有限制为4kb
• 300个cookie浏览器上限

删除Cookie;

• 不设置有效期，关闭浏览器，自动失效
• 设置有效期为0

编码和解码

URLEncoder.encode("张飞","utf-8")
URLDecoder.decode(cookie.getValue(),"utf-8")

package com.jf.servlet;import javax.servlet.ServletException;
import javax.servlet.http.Cookie;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.io.PrintWriter;
import java.util.Date;public class CookieDemo01 extends HttpServlet {@Overrideprotected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {//解决中文乱码问题req.setCharacterEncoding("utf-8");resp.setCharacterEncoding("utf-8");PrintWriter out = resp.getWriter();//Cookie，服务器从客户端拿取Cookie[] cookies = req.getCookies();//这里返回数组，说明存在多个cookie//判断cookie是否存在if(cookies!=null){//如果存在out.write("你上一次访问的时间是：");for (int i = 0; i < cookies.length; i++) {Cookie cookie = cookies[i];//获取cookie的名字if(cookie.getName().equals("lastLoginTime")){//获取cookie中的值long lastLoginTime = Long.parseLong(cookie.getValue());Date date = new Date(lastLoginTime);out.write(date.toLocaleString());}}}else {out.write("这是你第一次访问本站");}//服务给客户端响应一个cookieCookie cookie = new Cookie("lastLoginTime",System.currentTimeMillis()+"");//cookie有效期为1天cookie.setMaxAge(24*60*60);resp.addCookie(cookie);}@Overrideprotected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {doGet(req, resp);}
}

package com.jf.servlet;import javax.servlet.ServletException;
import javax.servlet.http.Cookie;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.io.PrintWriter;
import java.net.URLDecoder;
import java.net.URLEncoder;
import java.util.Date;//中文数据传递
public class CookieDemo03 extends HttpServlet {@Overrideprotected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {//解决中文乱码问题req.setCharacterEncoding("utf-8");resp.setCharacterEncoding("utf-8");//Cookie，服务器从客户端拿取Cookie[] cookies = req.getCookies();//这里返回数组，说明存在多个cookiePrintWriter out = resp.getWriter();//判断cookie是否存在if(cookies!=null){//如果存在out.write("你上一次访问的时间是：");for (int i = 0; i < cookies.length; i++) {Cookie cookie = cookies[i];//获取cookie的名字if(cookie.getName().equals("name")){//解码out.write(URLDecoder.decode(cookie.getValue(),"utf-8"));}}}else {out.write("这是你第一次访问本站");}//编码Cookie cookie = new Cookie("name", URLEncoder.encode("张飞","utf-8"));resp.addCookie(cookie);}@Overrideprotected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {super.doPost(req, resp);}
}

5.3 Session（重点）

什么是session

• 服务器会给每一个用户创建一个Session对象
• 一个session 独占一个浏览器，只要浏览器没有关闭，这个session就存在
• 用户登录网站，整个网站都可以访问----》保存用户的信息

session和cookie的区别

• cookie就是把用户的数据写给浏览器，浏览器保存（可以保存多个）
• session把用户的数据写到用户独占Session中，服务器保存（保存重要的信息，减少服务器资源的浪费）
• session对象是由服务创建

使用场景

• 保存一个登陆用户的信息
• 购物车信息
• 在整个网站中经常使用的数据，将它保存在Session中；

package com.jf.servlet;import com.jf.pojo.Person;import javax.servlet.ServletException;
import javax.servlet.http.*;
import java.io.IOException;public class SessionDemo01 extends HttpServlet {@Overrideprotected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {//解决乱码问题resp.setCharacterEncoding("utf-8");req.setCharacterEncoding("utf-8");resp.setContentType("text/html;charset=utf-8");//得到sessionHttpSession session = req.getSession();//给session存信息session.setAttribute("name",new Person("张飞",15));//获取session的idString sessionId = session.getId();//判断Seesion是不是新创建的if(session.isNew()){resp.getWriter().write("session创建成功,ID:"+sessionId);}else {resp.getWriter().write("session已经在服务器中存在了,ID:"+sessionId);}//session创建的时候做了：
//        Cookie cookie = new Cookie("JSESSIONID",sessionId);
//        resp.addCookie(cookie);}@Overrideprotected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {doGet(req, resp);}
}

得到session

package com.jf.servlet;import com.jf.pojo.Person;import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
import java.io.IOException;public class SessionDemo02 extends HttpServlet {@Overrideprotected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {//解决乱码问题resp.setCharacterEncoding("utf-8");req.setCharacterEncoding("utf-8");resp.setContentType("text/html;charset=utf-8");//得到sessionHttpSession session = req.getSession();Person person = (Person) session.getAttribute("name");System.out.println(person.toString());}@Overrideprotected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {doGet(req, resp);}
}

手动注销

package com.jf.servlet;import com.jf.pojo.Person;import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
import java.io.IOException;public class SessionDemo03 extends HttpServlet {@Overrideprotected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {HttpSession session = req.getSession();session.removeAttribute("name");session.invalidate();//注销}@Overrideprotected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {doGet(req, resp);}
}

自动注销在web.xml中配置

<!--设置session的失效时间-->
<session-config><!--15分钟后失效，以分钟为单位--><session-timeout>15</session-timeout>
</session-config>

6.JSP

什么是jsp

• java server page:java服务器端页面，也和servlet一样，用于动态Web页面

最大的特点：

• 写JSP和HTML一样
• 区别：
  • HTML只给用户提供静态的数据
  • JSP页面可以嵌入java代码，为用户提供动态数据

浏览器向服务器发送请求，不管访问什么资源，其实都是访问Servlet

JSP最终也会被装换一个java类

//初始化
public void _jspInit() {}
//销毁
public void _jspDestroy() {}
//JSPService
public void _jspService(HttpServletRequest request,HttpServletResponse response)

    final javax.servlet.jsp.PageContext pageContext;//页面上下文final javax.servlet.ServletContext application;//applicationContextfinal javax.servlet.ServletConfig config;//configjavax.servlet.jsp.JspWriter out = null;//outfinal java.lang.Object page = this;//page:当前页javax.servlet.jsp.JspWriter _jspx_out = null;javax.servlet.jsp.PageContext _jspx_page_context = null;HttpServletRequest request//请求HttpServletResponse response//响应

输出页面前增加的代码

	  response.setContentType("text/html; charset=UTF-8");//设置响应的类型pageContext = _jspxFactory.getPageContext(this, request, response,null, false, 8192, true);_jspx_page_context = pageContext;application = pageContext.getServletContext();config = pageContext.getServletConfig();out = pageContext.getOut();_jspx_out = out;

以上的这些对象都可以在JSP中使用

在JSP页面中，只要是JAVA代码就会原封不动的输出

如果是HTML代码，就会封装为：

out.write("<html>\r\n")

这样的格式，输出到前端

6.1 JSP基础语法

JSP表达式

<%--  JSP表达式作用：用来将程序的输出，输出到客户端
--%><%= new java.util.Date()%>

JSP脚本片段

<%--  JSP脚本片段--%>
<%int sum = 0;for (int i = 0; i <=100; i++) {sum+=i;}out.print("<h1>Sum="+sum+"</h1>");
%>

JSP片段的再实现

<%--  JSP脚本片段--%>
<%int sum = 0;for (int i = 0; i <=100; i++) {sum+=i;}out.print("<h1>Sum="+sum+"</h1>");
%>
<%int x=10;out.println(x);
%>
<%int y=2;out.println(y);
%>
<%--在代码中嵌入HTML代码--%>
<%for (int i = 0; i <=5; i++) {
%>
<h1>hello world</h1>
<%}
%>

JSP声明

<%!static {System.out.println("Loading Servlet!");}private int globVar= 0 ;public void k(){System.out.println("进入了K方法");}
%>

JSP声明：会被编译到JSP生成Java的类中，其他的就会被生成到_jspService方法中。

JSP注释不会在客户端中显示，html就会显示。

6.2 JSP指令

jsp导包

<%@ page import="java.util.Date" %>

jsp定制错误页面

方法一：

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<%@ page errorPage="error/500.jsp" %>
<html>
<%--定制错误页面--%>
<head><title>Title</title>
</head>
<body>
<%int x =1/0;
%>
</body>
</html>

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head><title>Title</title>
</head>
<body>
<img src="../img/500.png" alt="500">
</body>
</html>

方法二：

<%@ page contentType="text/html;charset=UTF-8" language="java" %><html>
<%--定制错误页面--%>
<head><title>Title</title>
</head>
<body>
<%int x =1/0;
%>
</body>
</html>

在web.xml中

<error-page><error-code>500</error-code><location>/error/500.jsp</location>
</error-page>

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head><title>Title</title>
</head>
<body>
<img src="../img/500.png" alt="500">
</body>
</html>

JSP拼接页面

<%@ page contentType="text/html;charset=UTF-8" language="java" %><html>
<head><title>Title</title>
</head>
<body>
<%--@include会将两个页面合二为一--%>
<%@include file="common/header.jsp"%>
<h1>网页主体</h1>
<%@include file="common/footer.jsp"%><hr>
<%--JSP标签
jsp:include：拼接页面，本质是三个
--%>
<jsp:include page="common/header.jsp"/>
<h1>网页主体</h1>
<jsp:include page="common/footer.jsp"/>
</body>
</html>

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<h1>我是footer</h1>

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head><title>Title</title>
</head>
<body>
<h1>我是header</h1>
</body>
</html>

6.3 9大内置对象

• PageContext 存东西
• Request 存东西
• Response
• Session 存东西
• Application [ServletContext] 存东西
• config [ServletConfig]
• out
• page
• exception

Request ：客户端向服务器发送请求，产生的数据，用户看完就没用了，比如：新闻

Session ：客户端向服务器发送请求，产生的数据，用户用完一会还有用，比如购物车

Application：客户端向服务器发送请求，产生的数据，一个用户用完了，其他用户还可能使用，比如聊天数据

常见场景：

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head><title>Title</title>
</head>
<body>
<%pageContext.setAttribute("name1","张飞1号");//保存的数据只在一个页面中有效request.setAttribute("name2","张飞2号");//保存的数据只在一次请求中有效，请求转发会携带这个数据session.setAttribute("name3","张飞3号");//保存的数据只在一次会话中有效，从打开浏览器到关闭浏览器application.setAttribute("name4","张飞4号");//保存的数据只在服务器中有效，从打开服务器到关闭服务器
%>
<%--脚本片段的代码，会被原封不动生成到...jsp.java要求：这里的代码，必须保证Java语法的正确性
--%>
<%//从pageContext取出，我们通过寻找的方式来//从底层到高层（作用域）page-->request-->session-->applicationString name1 = (String) pageContext.findAttribute("name1");String name2 = (String) pageContext.findAttribute("name2");String name3 = (String) pageContext.findAttribute("name3");String name4 = (String) pageContext.findAttribute("name4");String name5 = (String) pageContext.findAttribute("name5");pageContext.forward("/pageDemo03.jsp");
%>
<%--使用EL表达式输出--%>
<h1>取出的值：</h1>
<h2>${name1}</h2>
<h2>${name2}</h2>
<h2>${name3}</h2>
<h2>${name4}</h2>
<h2><%= name5%></h2>
</body>
</html>

7 JSP标签，JSTL标签，EL表达式

<!--            jsp表达式的依赖--><groupId>javax.servlet.jsp.jstl</groupId><artifactId>jstl-api</artifactId><version>1.2</version></dependency><dependency>
<!--         standard标签   --><groupId>taglibs</groupId><artifactId>standard</artifactId><version>1.1.2</version></dependency>

EL表达式：${}

作用：

• 获取数据
• 执行运算
• 获取web开发的常用对象

JSP标签：

<jsp:forward page="jspTag2.jsp"><jsp:param name="name" value="js"/><jsp:param name="age" value="15"/>
</jsp:forward>

JSTL表达式：

JSTL标签的使用是为了弥补HTML的不足，它自定义了许多标签，标签的代码和java代码一样

核心标签：

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
<html>
<head><title>Title</title>
</head>
<body>
<h4>测试</h4>
<form action="coreif.jsp" method="get">
<%--    EL表达式获取表单中的数据${param.参数名}
--%><input type="text" name="username" value="${param.username}"><input type="submit" value="登录">
</form>
<%--判断如果提交的用户是管理员，则登录成功--%>
<c:if test="${param.username=='admin'}" var="isAdmin"><c:out value="管理员欢迎您"></c:out>
</c:if>
<c:out value="${isAdmin}"></c:out>
</body>
</html>

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
<html>
<head><title>Title</title>
</head>
<body>
<%--定义一个变量score,值为85--%>
<c:set  var="score" value="85"></c:set>
<c:choose><c:when test="${score>=90}">你的成绩为优秀</c:when><c:when test="${score>=80}">你的成绩为良好</c:when>
</c:choose>
</body>
</html>

<%@ page import="java.util.ArrayList" %>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
<html>
<head><title>Title</title>
</head>
<body>
<%ArrayList<String> people = new ArrayList<>();people.add(0,"张飞");people.add(1,"张2");people.add(2,"张3");people.add(3,"张4");request.setAttribute("list",people);
%>
<%--
var 每一次遍历的变量
items 要遍历的对象
begin 哪里开始
end 到哪里
step 步长
--%>
<c:forEach var="people" items="${list}"><c:out value="${people}"></c:out>
</c:forEach>
<hr>
<c:forEach var="people" items="${list}" begin="1" end="2" step="1"><c:out value="${people}"></c:out>
</c:forEach>
</body>
</html>

8 MVC三层架构

Model

• 业务处理：业务逻辑（Service）
• 数据持久层：CRUD (Dao)

View

• 展示数据
• 提供链接发起Servlet请求（a,img,form...）

Controller

• 接收用户的请求：（req:请求参数，Session信息...）
• 交给业务层处理对应的代码
• 控制视图的跳转

登录-->接收用户的登录请求-->处理用户的请求（获取用户登录的参数,username,password）-->交给业务层处理登录业务（判断用户名和密码是否正确：事务）-->Dao层查询用户名和密码是否正确-->数据库

9 Filter

Filter:过滤器，用来过滤网站的数据

• 用来处理中文乱码
• 用来登录验证

步骤：

1.导包

2.编写过滤器

package com.jf.filter;import javax.servlet.*;
import java.io.IOException;public class CharacterEncodingFilter implements Filter {//初始化 web服务器启动，就已经初始化了@Overridepublic void init(FilterConfig filterConfig) throws ServletException {System.out.println("CharacterEncodingFilter已经初始化了");}//chain :链/** 1.过滤中的所有的代码，在过滤特定请求的时候都会执行* 2.必须要让过滤器继续同行* chain.doFilter(request,response);* */@Overridepublic void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {request.setCharacterEncoding("utf-8");response.setCharacterEncoding("utf-8");response.setContentType("text/html;charset=UTF-8");System.out.println("CharacterEncodingFilter执行前");chain.doFilter(request,response);//让我们的请求继续执行，如果不写，程序就会停止System.out.println("CharacterEncodingFilter执行后");}//销毁 web服务器停止了，过滤就会销毁@Overridepublic void destroy() {System.out.println("CharacterEncodingFilter销毁");}
}

在web.xml中设置：

<filter><filter-name>CharacterEncodingFilter</filter-name><filter-class>com.jf.filter.CharacterEncodingFilter</filter-class>
</filter>
<filter-mapping><filter-name>CharacterEncodingFilter</filter-name><url-pattern>/servlet/*</url-pattern>
</filter-mapping>

10.监听器

1.编写监听器接口

package com.jf.listener;import javax.servlet.ServletContext;
import javax.servlet.http.HttpSessionEvent;
import javax.servlet.http.HttpSessionListener;//统计网站的在线人数：
public class OnlineCountListener implements HttpSessionListener {//创建session监听//一旦创建session就会触发一次事件@Overridepublic void sessionCreated(HttpSessionEvent se) {ServletContext ctx = se.getSession().getServletContext();System.out.println(se.getSession().getId());Integer onlineCount = (Integer) ctx.getAttribute("OnlineCount");if(onlineCount==null){onlineCount = new Integer(1);}else {int count= onlineCount.intValue();onlineCount= new Integer(count+1);}ctx.setAttribute("OnlineCount",onlineCount);}//销毁session监听//一旦销毁session就会触发一次事件@Overridepublic void sessionDestroyed(HttpSessionEvent se) {ServletContext ctx = se.getSession().getServletContext();Integer onlineCount = (Integer) ctx.getAttribute("OnlineCount");if(onlineCount==null){onlineCount = new Integer(0);}else {int count= onlineCount.intValue();onlineCount= new Integer(count-1);}ctx.setAttribute("onlineCount",onlineCount);}/** session销毁* 手动销毁： se.getSession().invalidate();* 自动销毁在web.xml中设置：<session-config><session-timeout>1</session-timeout></session-config>* */
}

2.在web.xml注册监听器

<listener><listener-class>com.jf.listener.OnlineCountListener</listener-class>
</listener>

11.监听器和过滤器的常见应用

在GUI中监听器的应用：

package com.jf.listener;import java.awt.*;
import java.awt.event.WindowEvent;
import java.awt.event.WindowListener;public class TestPanel {public static void main(String[] args) {Frame frame = new Frame("窗口关闭");Panel panel = new Panel(null);frame.setLayout(null);frame.setBounds(300,300,500,500);frame.setBackground(new Color(0,0,255));panel.setBounds(50,50,300,300);panel.setBackground(new Color(0,255,0));frame.add(panel);frame.setVisible(true);//监听事件，监听关闭事件frame.addWindowListener(new WindowListener() {@Overridepublic void windowOpened(WindowEvent e) {System.out.println("打开");}@Overridepublic void windowClosing(WindowEvent e) {System.out.println("关闭img");System.exit(0);}@Overridepublic void windowClosed(WindowEvent e) {System.out.println("关闭ed");}@Overridepublic void windowIconified(WindowEvent e) {}@Overridepublic void windowDeiconified(WindowEvent e) {}@Overridepublic void windowActivated(WindowEvent e) {System.out.println("激活");}@Overridepublic void windowDeactivated(WindowEvent e) {System.out.println("未激活");}});}
}

用户登录之后才能进入主页，用户注销后就不能进入主页

1.用户登录之后，向session中放入用户的数据

2.进入主页的时候判断用户是否登录

package com.jf.listener;import javax.servlet.*;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;public class SysFilter implements Filter {@Overridepublic void init(FilterConfig filterConfig) throws ServletException {}@Overridepublic void doFilter(ServletRequest req, ServletResponse resp, FilterChain chain) throws IOException, ServletException {HttpServletRequest request = (HttpServletRequest) req;HttpServletResponse response = (HttpServletResponse) resp;if(request.getSession().getAttribute("USER_SESSION")==null){response.sendRedirect("/error.jsp");}chain.doFilter(request,response);}@Overridepublic void destroy() {}
}

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head><title>Title</title>
</head>
<body>
<form action="/servlet/login" method="post"><input type="text" name="username"><input type="submit">
</form>
</body>
</html>

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head><title>Title</title>
</head>
<body>
<h1>错误</h1>
<h1>没有权限，密码错误</h1>
<p><a href="/Login.jsp">返回登录页面</a></p>
</body>
</html>

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head><title>Title</title>
</head>
<body><h1>主页</h1>
<p><a href="/servlet/logout">注销</a></p>
</body>
</html>

package com.jf.servlet;import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;public class LoginServlet extends HttpServlet {@Overrideprotected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {//获取前端请求的参数String username = req.getParameter("username");if(username.equals("admin")){//登录成功req.getSession().setAttribute("USER_SESSION",req.getSession().getId());resp.sendRedirect("/sys/success.jsp");}else {//登录失败resp.sendRedirect("/error.jsp");}}@Overrideprotected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {doGet(req, resp);}
}

package com.jf.servlet;import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;public class LogoutServlet extends HttpServlet {@Overrideprotected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {Object user_session = req.getSession().getAttribute("USER_SESSION");if(user_session!=null){req.getSession().removeAttribute("USER_SESSION");resp.sendRedirect("/Login.jsp");}else {resp.sendRedirect("/Login.jsp");}}@Overrideprotected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {doGet(req, resp);}
}

12.JDBC

JDBC:java连接数据库

需要jar包：

• java.sql
• javax.sql
• mysql-conneter-java

package com.jf.test;import java.sql.*;public class TestJdbc {public static void main(String[] args) throws ClassNotFoundException, SQLException {//解决中文乱码useUnicode=true&characterEncoding=utf-8String url = "jdbc:mysql://localhost:3306/jdbc?useUnicode=true&characterEncoding=utf-8&useSSL=true";String username = "root";String password = "123456";//1.加载驱动Class.forName("com.mysql.jdbc.Driver");//2.连接数据库Connection connection = DriverManager.getConnection(url, username, password);//3.向数据库发送sql的对象Statement statement = connection.createStatement();//4.编写sqlString sql="select * from users";//5.执行sql,返回一个rs:结果集ResultSet rs = statement.executeQuery(sql);while (rs.next()){System.out.println("id="+rs.getObject("id"));System.out.println("name="+rs.getObject("name"));System.out.println("password="+rs.getObject("password"));System.out.println("email="+rs.getObject("email"));System.out.println("birthday="+rs.getObject("birthday"));}//6.关闭连接，释放资源 先开后关rs.close();statement.close();connection.close();}
}

预编译sql

package com.jf.test;import java.sql.*;public class TestJdbc2 {public static void main(String[] args) throws ClassNotFoundException, SQLException {//解决中文乱码useUnicode=true&characterEncoding=utf-8String url = "jdbc:mysql://localhost:3306/jdbc?useUnicode=true&characterEncoding=utf-8&useSSL=true";String username = "root";String password = "123456";//1.加载驱动Class.forName("com.mysql.jdbc.Driver");//2.连接数据库Connection connection = DriverManager.getConnection(url, username, password);//3.编写sqlString sql="insert into users(id, name, password, email, birthday) values (?,?,?,?,?)";//4.预编译PreparedStatement preparedStatement = connection.prepareStatement(sql);preparedStatement.setInt(1,5);//给第一个占位符?的值赋值为1preparedStatement.setString(2,"java张三");//给第二个占位符?的值赋值为java张三preparedStatement.setString(3,"123456");//给第三个位符?的值赋值为123456preparedStatement.setString(4,"ks@qq.com");//给第四个占位符?的值赋值为ks@qq.compreparedStatement.setDate(5,new Date(new java.util.Date().getTime()));//给第五个占位符?的值赋值为new Date(new java.util.Date().getTime())//5.执行sqlint i = preparedStatement.executeUpdate();if(i>0){System.out.println("插入成功");}preparedStatement.close();connection.close();}
}

junit单元测试

依赖：

<!--        单元测试--><dependency><groupId>junit</groupId><artifactId>junit</artifactId><version>4.12</version></dependency>

简答使用

@Test注解只有在方法上有效，只要加了这个注解的方法，就可以直接使用

@Test
public void test(){System.out.println("hello");
}

事务：

package com.jf.test;import org.junit.Test;import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;public class TestJdbc3 {@Testpublic void test(){//解决中文乱码useUnicode=true&characterEncoding=utf-8String url = "jdbc:mysql://localhost:3306/jdbc?useUnicode=true&characterEncoding=utf-8&useSSL=true";String username = "root";String password = "123456";Connection connection = null;//1.加载驱动try {Class.forName("com.mysql.jdbc.Driver");//2.连接数据库connection = DriverManager.getConnection(url, username, password);//3.通知数据库开启事务false开启connection.setAutoCommit(false);String sql="update account set money=money-100 where name='A'";connection.prepareStatement(sql).executeUpdate();//4.制作错误//int i = 1/0;String sql2="update account set money=money+100 where name='B'";connection.prepareStatement(sql2).executeUpdate();connection.commit();//以上两条SQL都执行成功了，就提交事务System.out.println("提交成功");} catch (Exception e) {try {//如果出现异常，就通知数据库回滚事务connection.rollback();} catch (SQLException e1) {e1.printStackTrace();}e.printStackTrace();}finally {try {connection.close();} catch (SQLException e) {e.printStackTrace();}}}
}

13.邮件发送

import com.sun.mail.util.MailSSLSocketFactory;import javax.mail.*;
import javax.mail.internet.InternetAddress;
import javax.mail.internet.MimeMessage;
import java.security.GeneralSecurityException;
import java.util.Properties;public class Test {//简单邮件：没有附件和图片，纯文本邮件//复杂邮件：有附件和图片//要发送邮件，需要获得协议和支持，开启服务POP3/STMP//jlljptqkgezoihicpublic static void main(String[] args) throws Exception {Properties prop = new Properties();prop.setProperty("mail.host","smtp.qq.com");prop.setProperty("mail.transport.protocol","smtp");prop.setProperty("mail.smtp.auth","true");//验证用户密码MailSSLSocketFactory sf =new MailSSLSocketFactory();sf.setTrustAllHosts(true);prop.put("mail.smtp.ssl.enable","true");prop.put("mail.smtp.ssl.socketFactory",sf);//使用JavaMial发送邮件的5个步骤//1.创建定义整个应用程序所需的环境信息的Session对象Session session = Session.getDefaultInstance(prop, new Authenticator() {@Overrideprotected PasswordAuthentication getPasswordAuthentication() {return new PasswordAuthentication("1514086388@qq.com ", "jlljptqkgezoihic");}});session.setDebug(true);//2.通过session获得transport对象Transport ts = session.getTransport();//3.使用邮箱的用户名和授权码连上邮件服务器ts.connect("smtp.qq.com","1514086388@qq.com","jlljptqkgezoihic");//4.创建邮件MimeMessage message = new MimeMessage(session);message.setFrom(new InternetAddress("1514086388@qq.com"));//发件人message.setRecipient(Message.RecipientType.TO,new InternetAddress("1514086388@qq.com"));//收件人message.setSubject("HELLO");message.setContent("<h1 style='color:red'>你好</h1>","text/html;charset=UTF-8");//5.发送邮件ts.sendMessage(message,message.getAllRecipients());//6.关闭链接ts.close();}}