JavaWeb学习

从本章开始，将进入到JavaWeb开发的基础学习当中，前两部分分别为数据库以及前端的学习。

文章目录

前言
一、HTTP
二、Tomcat
三、Servlet
- 1、快速入门
- 2、执行流程
- 3、生命周期
四、Request & Response
- 1、Request
- 2、Response
五、JSP
- MVC模型：
- 三层架构：
六、Cookie & Session
- 1、Cookie
- 2、Session
- 3、注册和登录案例
七、Flitter
八、Listener
九、Ajax
十、Vue
- 1、常用指令
- 2、生命周期
十一、ElementUI
总结

前言

一、HTTP

HTTP：超文本传输协议，规定了浏览器和服务器之间数据传输（请求、响应）的规则。

二、Tomcat

三、Servlet

1、快速入门

package youth.web;

import javax.servlet.*;
import javax.servlet.annotation.WebServlet;
import java.io.IOException;

@WebServlet("/demo1")
public class ServletDemo1 implements Servlet {
    @Override
    public void init(ServletConfig servletConfig) throws ServletException {
        
    }

    @Override
    public ServletConfig getServletConfig() {
        return null;
    }

    @Override
    public void service(ServletRequest servletRequest, ServletResponse servletResponse) throws ServletException, IOException {
        System.out.println("Hello Servlet");
    }

    @Override
    public String getServletInfo() {
        return null;
    }

    @Override
    public void destroy() {

    }
}

2、执行流程

3、生命周期

原生Servlet

package youth.web;

import javax.servlet.*;
import javax.servlet.annotation.WebServlet;
import java.io.IOException;

@WebServlet(urlPatterns = "/demo1", loadOnStartup = 1)
public class ServletDemo1 implements Servlet {
    
    @Override
    public void init(ServletConfig config) throws ServletException {
        System.out.println("init...");
    }

    
    @Override
    public void service(ServletRequest req, ServletResponse res) throws ServletException, IOException {
        // 根据请求方式的不同，进行分别的处理
        HttpServletRequest request = (HttpServletRequest) req;
        
        // 1. 获取请求方式
        String method = request.getMethod();
        
        // 2. 判断
        if("GET".equals(method)) {
            // get方式的处理逻辑
        }else if("POST".equals(method)){
            // post方式的处理逻辑
        }
    }

    
    @Override
    public void destroy() {
        System.out.println("destroy...");
    }

    @Override
    public String getServletInfo() {
        return null;
    }

    @Override
    public ServletConfig getServletConfig() {
        return null;
    }
}

HttpServlet extends GenericServlet，重写了上述Servlet的方法，方便操作，对HttpServlet只需要重写doGet和doPost方法。

package youth.web;

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("/demo2")
public class ServletDemo2 extends HttpServlet {

    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        System.out.println("get");
    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        System.out.println("post");
    }
}

四、Request & Response

1、Request

package youth.web;

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.nio.Buffer;

@WebServlet("/req1")
public class RequestDemo1 extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        // String getMethod(); 获取请求方式：GET
        String method = req.getMethod();
        System.out.println(method);

        // String getContextPath(); 获取虚拟目录（项目访问路径）：/request-demo
        String contextPath = req.getContextPath();
        System.out.println(contextPath);

        // StringBuffer getRequestURL(): 获取URL（统一资源定位符）：http://localhost:8080/request-demo/req1
        StringBuffer url = req.getRequestURL();
        System.out.println(url.toString());

        // String getRequestURI(): 获取URI（统一资源标识符）： /request-demo/req1
        String uri = req.getRequestURI();
        System.out.println(uri);

        // String getQueryString(): 获取请求参数（GET方式）： username=youth
        String queryString = req.getQueryString();
        System.out.println(queryString);

        //--------------------
        // 获取请求头：User-agent：浏览器的版本信息
        String agent = req.getHeader("user-agent");
        System.out.println(agent);


    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        // 获取post 请求体：请求参数

        // 1. 获取字符输入流
        BufferedReader br = req.getReader();

        // 2. 读取数据
        String line = br.readLine();
        System.out.println(line);
    }
}

package youth.web;

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.Map;

@WebServlet("/req2")
public class RequestDemo2 extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        // GET请求逻辑
        //System.out.println("get...");

        // 1.获取所以参数的Map集合
        Map map = req.getParameterMap();
        for(String key : map.keySet()){
            System.out.print(key+":");

            // 获取值
            String[] values = map.get(key);
            for(String value: values){
                System.out.print(value+" ") ;
            }
            System.out.println();
        }
        System.out.println("---------------");

        // 2.根据key获取参数数组
        String[] hobbies = req.getParameterValues("hobby");
        for(String hobby : hobbies){
            System.out.println(hobby);
        }

        // 3.根据key获取单个参数值
        String username = req.getParameter("username");
        String password = req.getParameter("password");

        System.out.println(username);
        System.out.println(password);
    }

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

    // 解决乱码：POST.getReader()  GET.getQueryString

protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // 解决乱码：POST.getReader()
        request.setCharacterEncoding("UTF-8");
    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // 1.获取username
        String username = request.getParameter("username");
        System.out.println("解决乱码前："+username);

        // 2. GET,获取参数的方式：getQueryString
        // 乱码原因：Tomcat进行URL解码，默认的字符集ISO-8859-1
        // 2.1 先对乱码数据进行编码：转为字符数组
        byte[] bytes = username.getBytes(StandardCharsets.ISO_8859_1);
        // 2.2 字节数组解码
        username = new String(bytes, StandardCharsets.UTF_8);

        System.out.println("解决乱码后: "+username);
    }

一个Servlet将需要转发的数据存储到request当中（request.setAttribute），然后通过getRequestDispatcher(“URL”).forward(request,response)转发

@WebServlet("/req4")
public class RequestDemo4 extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        this.doGet(request, response);
    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        System.out.println("demo4...");

        // 存储数据
        request.setAttribute("msg","hello");

        // 请求转发
        request.getRequestDispatcher("/req5").forward(request,response);

    }
}

另一个Servlet负责接收转发的数据，通过request.getAttribute（“转发数据的键名”）

@WebServlet("/req5")
public class RequestDemo5 extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        this.doGet(request, response);
    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        System.out.println("demo5...");

        // 获取数据
        Object msg = request.getAttribute("msg");
        System.out.println(msg);

    }
}

2、Response

@WebServlet("/resp1")
public class ResponseDemo1 extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        this.doGet(request, response);
    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        System.out.println("resp1...");

//        // 重定向
//        // 1. 设置响应状态码 302
//        response.setStatus(302);
//
//        // 2. 设置响应头 Location
//        response.setHeader("Location", "/tomcat-demo/resp2");
        
        // 简化方式完成重定向
        response.sendRedirect("/tomcat-demo/resp2");
    }
}

        // 动态获取虚拟目录
        String contextPath = request.getContextPath();
        
        response.sendRedirect(contextPath+"/resp2");

        // 简化方式完成重定向
        // response.sendRedirect("/tomcat-demo/resp2");

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        response.setContentType("text/html; charset=utf-8");
        // 1.获取字符输出流，不需要关闭
        PrintWriter writer = response.getWriter();
//         content-type
//        response.setHeader("content-type", "text/html");
        writer.write("aaa");
        writer.write("aaa");
    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

        // 1.读取文件
        FileInputStream fis = new FileInputStream("C://Users//ThinkPad//Pictures//Camera Roll//background.png");

        // 2.获取response字节输出流
        ServletOutputStream os = response.getOutputStream();

        // 3.完成流的拷贝
//        byte[] buff = new byte[1024];
//        int len = 0;
//        while((len = fis.read(buff)) != -1)
//            os.write(buff,0, len);

        IOUtils.copy(fis, os);

        fis.close();
    }

数据库内创建用户表，并根据用户表的属性在java.pojo中创建User的java类。
编写登录（HTML、CSS）界面，其中用户名和密码的表单form的action属性填写LoginServlet的URL（LoginServlet用@注解改写）。
java.mapper中的UserMapper.class和resources.mapper的UserMapper.xml对应，UserMapper.class写方法名，xml里写具体的SQL语句（也可以用@注解的方式直接写在.class里），mybatis-config.xml配置JDBC的相关参数以及mapper的扫描（参考MyBatis官网）。
LoginServlet重写doGet和doPost方法，首先通过request.getParameter方法接收用户名和密码，然后调用Mapper查询用户是否存在（1.获取SqlSessionFactory对象，2.获取SqlSession对象，3.获取Mapper对象，4.调用UserMapper的方法，5.释放资源），最后根据查询的结果执行相应的语句。

mybatis-config.xml

LoginServlet

@WebServlet("/loginServlet")
public class loginServlet extends HttpServlet {
    @Override
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        this.doGet(request, response);
    }

    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // 1.用户名和密码的接收
        String username = request.getParameter("username");
        String password = request.getParameter("password");

        // 2.调用MyBatis查询
        // 2.1 获取SqlSessionFactory对象
        String resource = "mybatis-config.xml";
        InputStream inputStream = Resources.getResourceAsStream(resource);
        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);

        // 2.2 获取SqlSession对象
        SqlSession sqlSession = sqlSessionFactory.openSession();

        // 2.3 获取Mapper
        UserMapper userMapper = sqlSession.getMapper(UserMapper.class);

        // 2.4 调用方法
        User user = userMapper.select(username, password);

        // 2.5 释放资源
        sqlSession.close();

        response.setContentType("text/html; charset=utf-8");
        PrintWriter writer = response.getWriter();
        // 3.判断User是否为null
            if(user != null){
                // 登陆成功
                writer.write("登陆成功");
            }
            else{
                writer.write("登陆失败");
            }
    }
}

编写注册（HTML、CSS）界面，其中用户名和密码的表单form的action属性填写RegisterServlet的URL（RegisterServlet用@注解）。
java.mapper中的UserMapper.class和resources.mapper的UserMapper.xml对应，UserMapper.class写方法名，.xml里写具体的SQL语句（也可以用@注解的方式直接写在.class里），mybatis-config.xml配置JDBC的相关参数以及mapper的扫描（参考MyBatis官网）。
RegisterServlet重写doGet和doPost方法，首先通过request.getParameter方法接收用户名和密码，然后调用Mapper查询用户是否存在，最后根据查询的结果判断是否进行用户的注册，并且通过response返回结果给浏览器。

RegisterServlet

@WebServlet("/registerServlet")
public class registerServlet extends HttpServlet {
    @Override
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        this.doGet(request, response);
    }

    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // 1.用户名和密码的接收
        String username = request.getParameter("username");
        String password = request.getParameter("password");

        // 封装用户对象
        User user = new User();
        user.setUsername(username);
        user.setPassword(password);

        // 2.调用Mapper 根据用户名查询用户对象
        // 2.1 获取SqlSessionFactory对象
        String resource = "mybatis-config.xml";
        InputStream inputStream = Resources.getResourceAsStream(resource);
        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);

        // 2.2 获取SqlSession对象
        SqlSession sqlSession = sqlSessionFactory.openSession();

        // 2.3 获取Mapper
        UserMapper userMapper = sqlSession.getMapper(UserMapper.class);

        // 2.4 调用方法
        User u = userMapper.selectByUsername(username);

        response.setContentType("text/html; charset=utf-8");
        // 3. 判断用户对象是否为null
        if(u == null){
            // 用户名不存在，可以添加用户
            userMapper.add(user);

            // 提交事务
            sqlSession.commit();

            // 释放资源
            sqlSession.close();

            response.getWriter().write("注册成功");
        }
        else{
            // 用户名存在，给出提示信息
            response.getWriter().write("用户名已存在");
        }

    }
}

public class SqlSessionFactoryUtils {
    
    private  static SqlSessionFactory sqlSessionFactory;
    
    static {
        // 静态代码块会随着类的加载而自动执行，且只执行一次
        
        try{
            String resource = "mybatis-config.xml";
            InputStream inputStream = Resources.getResourceAsStream(resource);
            sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
    public static SqlSessionFactory getSqlSessionFactory(){
        return sqlSessionFactory;
    }
}

//        // 2.调用Mapper查询
//        // 2.1 获取SqlSessionFactory对象
//        String resource = "mybatis-config.xml";
//        InputStream inputStream = Resources.getResourceAsStream(resource);
//        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
        
        SqlSessionFactory sqlSessionFactory = SqlSessionFactoryUtils.getSqlSessionFactory();

五、JSP

<%…%>：编写Java代码
<%=…%>：输出内容或值到页面上
<%!..%>：成员变量或成员方法添加到类中

Servlet

EL表达式

brand.id执行的是getId()方法，而不是直接获取属性值。

<%--
  Created by IntelliJ IDEA.
  User: ThinkPad
  Date: 2022/6/26
  Time: 12:00
  To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>

<%--jstl引入--%>
<%@taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core"%>



    Title


    
        <%= true %>
    

    
        <%= false %>
    

    
        
            ${status.count}
            ${status.id}
        
    

    
        ${i}

MVC模型：

三层架构：

三层架构的数据增删改查案例

项目框架

创建数据库以及相应的表，并插入数据。

创建与表相对应的POJO类（下划线变量名改为驼峰命名）。

package youth.pojo;



public class Brand {
    // id 主键
    private Integer id;
    // 品牌名称
    private String brandName;
    // 企业名称
    private String companyName;
    // 排序字段
    private Integer ordered;
    // 描述信息
    private String description;
    // 状态：0：禁用  1：启用
    private Integer status;


    public Brand() {
    }

    public Integer getId() {
        return id;
    }

    public void setId(Integer id) {
        this.id = id;
    }

    public String getBrandName() {
        return brandName;
    }

    public void setBrandName(String brandName) {
        this.brandName = brandName;
    }

    public String getCompanyName() {
        return companyName;
    }

    public void setCompanyName(String companyName) {
        this.companyName = companyName;
    }

    public Integer getOrdered() {
        return ordered;
    }

    public void setOrdered(Integer ordered) {
        this.ordered = ordered;
    }

    public String getDescription() {
        return description;
    }

    public void setDescription(String description) {
        this.description = description;
    }

    public Integer getStatus() {
        return status;
    }

    public void setStatus(Integer status) {
        this.status = status;
    }

    @Override
    public String toString() {
        return "Brand{" +
                " + id +
                ", brandName='" + brandName + ''' +
                ", companyName='" + companyName + ''' +
                ", ordered=" + ordered +
                ", description='" + description + ''' +
                ", status=" + status +
                '}';
    }
}

3.编写Mapper三步骤：（1）编写mybatis-config.xml的核心配置文件（负责JDBC的连接），（2）编写java.youth.mapper.BrandMapper接口（负责调用SQL语句），（3）编写resources.youth.mapper.BrandMapper.xml（负责编写SQL语句）。

mybatis-config.xml

resources.youth.mapper.BrandMapper.xml

java.youth.mapper.BrandMapper

package youth.mapper;

import org.apache.ibatis.annotations.*;
import youth.pojo.Brand;

import java.util.List;

public interface BrandMapper {
    @Select("select * from tb_brand;")
    @ResultMap("brandResultMap")
    List selectAll();

    @Insert("insert into tb_brand values(#{id}, #{brandName}, #{companyName}, #{ordered}, #{description}, #{status});")
    void add(Brand brand);

    @Select("select * from tb_brand where id = #{id};")
    @ResultMap("brandResultMap")
    Brand selectById(int id);

    @Update("update tb_brand set brand_name = #{brandName}, company_name = #{companyName}, description = #{description}, status = #{status}, ordered = #{ordered} where id = #{id};")
    void update(Brand brand);

    @Delete("delete from tb_brand where id = #{id};")
    void delete(int id);
}

4.Service层，负责封装逻辑处理，访问数据库层调用mapper的方法处理数据。

package youth.service;

import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import youth.mapper.BrandMapper;
import youth.pojo.Brand;
import youth.util.SqlSessionFactoryUtils;

import java.util.List;

public class BrandService {
    SqlSessionFactory factory = SqlSessionFactoryUtils.getSqlSessionFactory();

    public List selectAll(){
        //调用BrandMapper.selectAll()

        // 2.获取SqlSession
        SqlSession sqlSession = factory.openSession();

        // 3.获取BrandMapper
        BrandMapper mapper = sqlSession.getMapper(BrandMapper.class);

        // 4.调用方法
        List brands = mapper.selectAll();

        sqlSession.close();

        return brands;
    }

    public Brand selectById(int id){
        //调用BrandMapper.selectAll()

        // 2.获取SqlSession
        SqlSession sqlSession = factory.openSession();

        // 3.获取BrandMapper
        BrandMapper mapper = sqlSession.getMapper(BrandMapper.class);

        // 4.调用方法
        Brand brand = mapper.selectById(id);

        sqlSession.close();

        return brand;
    }

    public void add(Brand brand){
        // 2.获取SqlSession
        SqlSession sqlSession = factory.openSession();

        // 3.获取BrandMapper
        BrandMapper mapper = sqlSession.getMapper(BrandMapper.class);

        // 4.调用方法
        mapper.add(brand);

        // 提交事务
        sqlSession.commit();

        // 释放资源
        sqlSession.close();
    }

    public void update(Brand brand){
        // 2.获取SqlSession
        SqlSession sqlSession = factory.openSession();

        // 3.获取BrandMapper
        BrandMapper mapper = sqlSession.getMapper(BrandMapper.class);

        // 4.调用方法
        mapper.update(brand);

        // 提交事务
        sqlSession.commit();

        // 释放资源
        sqlSession.close();
    }

    public void delete(int id){
        // 2.获取SqlSession
        SqlSession sqlSession = factory.openSession();

        // 3.获取BrandMapper
        BrandMapper mapper = sqlSession.getMapper(BrandMapper.class);

        // 4.调用方法
        mapper.delete(id);

        // 提交事务
        sqlSession.commit();

        // 释放资源
        sqlSession.close();
    }
}

5.Servlet层，封装浏览器传来的数据，转发给Service层进行数据的处理，并负责视图的展示。

package youth.web;

import youth.pojo.Brand;
import youth.service.BrandService;

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("/addServlet")
public class addServlet extends HttpServlet {

    private BrandService service = new BrandService();

    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        this.doGet(request, response);
    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

        // 处理POST请求的乱码问题
        request.setCharacterEncoding("utf-8");

        // 1. 接收表单提交的数据，封装为一个Brand对象
        String brandName = request.getParameter("brandName");
        String companyName = request.getParameter("companyName");
        String ordered = request.getParameter("ordered");
        String description = request.getParameter("description");
        String status = request.getParameter("status");

        // 封装为一个Brand对象
        Brand brand = new Brand();
        brand.setBrandName(brandName);
        brand.setCompanyName(companyName);
        brand.setDescription(description);
        brand.setOrdered(Integer.parseInt(ordered));
        brand.setStatus(Integer.parseInt(status));

        // 2.调用service 完成添加
        service.add(brand);

        // 3.转发到查询所以Servlet
        request.getRequestDispatcher("/selectAllServlet").forward(request, response);
    }
}

六、Cookie & Session

1、Cookie

发送Cookie

@WebServlet("/aServlet")
public class aServlet extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        this.doGet(request, response);
    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // 发送Cookie

        // 1. 创建Cookie对象
        Cookie cookie = new Cookie("username", "zs");

        // 2. 发送Cookie, 通过response
        response.addCookie(cookie);
    }
}

获取Cookie

@WebServlet("/bServlet")
public class bServlet extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        this.doGet(request, response);
    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // 获取Cookie

        // 1. 获取Cookie数组
        Cookie[] cookies = request.getCookies();

        // 2. 遍历数组
        for(Cookie cookie : cookies){
            // 3. 获取数据
            String name = cookie.getName();
            if("username".equals(name)){
                String value = cookie.getValue();
                System.out.println(name+":"+value);
                break;
            }
        }
    }
}

@WebServlet("/aServlet")
public class aServlet extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        this.doGet(request, response);
    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // 发送Cookie

        // 1. 创建Cookie对象
        Cookie cookie = new Cookie("username", "zs");

        // 设置存活时间
        cookie.setMaxAge(60 * 60 * 24 * 7); // 7 天

        // 2. 发送Cookie, 通过response
        response.addCookie(cookie);
    }
}

2、Session

存储数据到Session

@WebServlet("/aSession")
public class aSession extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        this.doGet(request, response);
    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // 存储到Session中

        // 1. 获取Session对象
        HttpSession session = request.getSession();

        // 2. 存储数据
        session.setAttribute("username", "zs");

    }
}

获取数据从Session

@WebServlet("/bSession")
public class bSession extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        this.doGet(request, response);
    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // 获取数据,从Session中

        // 1. 获取Session对象
        HttpSession session = request.getSession();

        // 2. 获取数据
        Object username = session.getAttribute("username");
        System.out.println(username);
    }
}

Cookie 和 Session的区别：

Cookie是服务器在第一次接收到浏览器发来的request请求时，通过response设置响应返回给浏览器一个Cookie。当浏览器再次访问服务器时，将携带服务器设置给浏览器的Cooike一起发送请求给服务器，服务器获取该id（key，value）便可识别出是哪一个浏览器。
Session是基于Cookie实现的，用来在一次会话的多次请求之间共享数据。即浏览器的多个请求都执行getSession方法来获取当前浏览器（会话）的Session（同一个），第一个请求使用setAttribute方法将value存储到key中，之后的请求可以使用getAttribute方法代入key的值获取相应的value。

3、注册和登录案例

loginServlet

@WebServlet("/loginServlet")
public class loginServlet extends HttpServlet {

    private UserService service = new UserService();

    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        this.doGet(request, response);
    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // 1. 获取用户名和密码
        String username = request.getParameter("username");
        String password = request.getParameter("password");

        // 获取复选框数据
        String remember = request.getParameter("remember");

        // 2. 调用service查询
        User user = service.login(username, password);

        // 3. 判断
        if(user != null){
            // 登录成功，跳转到查询所有的BrandServlet

            // 判断用户是否勾选记住我
            if("1".equals(remember)){
                // 勾选了，发送Cookie

                // 1. 创建Cookie对象
                Cookie c_username = new Cookie("username", username);
                Cookie c_password = new Cookie("password", password);

                // 设置Cookie 的存活时间
                c_username.setMaxAge(60 * 60 * 24 * 7);
                c_password.setMaxAge(60 * 60 * 24 * 7);
                // 2. 发送

                response.addCookie(c_username);
                response.addCookie(c_password);
            }

            // 将登录成功后的User对象，存储到session
            HttpSession session = request.getSession();
            session.setAttribute("user", user);

            String contextPath = request.getContextPath();
            response.sendRedirect("/brand-demo/selectAllServlet");
        }else{
            // 登录失败，跳转到login.jsp

            // 存储错误信息到request
            request.setAttribute("login_msg","用户名或密码错误");

            // 跳转到login.jsp
            request.getRequestDispatcher("/login.jsp").forward(request,response);
        }
    }
}

UserService

public class UserService {
    // 1.获取工厂
    SqlSessionFactory factory = SqlSessionFactoryUtils.getSqlSessionFactory();

    public User login(String username, String password){
        // 2.获取SqlSession
        SqlSession sqlSession = factory.openSession();

        // 3.获取BrandMapper
        UserMapper mapper = sqlSession.getMapper(UserMapper.class);

        // 4.调用方法
        User user = mapper.select(username, password);

        // 释放资源
        sqlSession.close();

        return user;
    }
}

UserMapper

public interface UserMapper {


    
    @Select("select * from tb_user where username = #{username} and password = #{password}")
    User select(@Param("username") String username,@Param("password")  String password);

    
    @Select("select * from tb_user where username = #{username}")
    User selectByUsername(String username);

    
    @Insert("insert into tb_user values(null,#{username},#{password})")
    void add(User user);
}

login.jsp

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
<%@ page isELIgnored="false" %>




    
    login
    




    
        LOGIN IN
        ${login_msg}
        Username:

        Password:
        Remember:
        
            
               
            没有账号？

registerServlet

@WebServlet("/registerServlet")
public class registerServlet extends HttpServlet {

    private UserService service = new UserService();

    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        this.doGet(request, response);
    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // 1. 获取用户名和密码
        String username = request.getParameter("username");
        String password = request.getParameter("password");

        // 获取输入的验证码
        String checkCode = request.getParameter("checkCode");

        // 程序生成的验证码
        HttpSession session = request.getSession();
        String checkCodeGen = (String) session.getAttribute("checkCodeGen");

        User user = new User();
        user.setUsername(username);
        user.setPassword(password);

        // 比对
        if(!checkCodeGen.equalsIgnoreCase(checkCode)){
            request.setAttribute("register_msg", "验证码错误");
            request.getRequestDispatcher("/register.jsp").forward(request, response);
            return;
        }
        // 2. 调用service注册
        boolean flag = service.register(user);

        // 3. 判断注册成功与否
        if(flag){
            request.setAttribute("register_msg", "注册成功，请登录");
            request.getRequestDispatcher("/login.jsp").forward(request,response);
        }else{
            request.setAttribute("register_msg", "用户名已存在");
            request.getRequestDispatcher("/register.jsp").forward(request,response);
        }
    }
}

checkCodeServlet

@WebServlet("/checkCodeServlet")
public class checkCodeServlet extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        this.doGet(request, response) ;
    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

        // 生成验证码
        ServletOutputStream os = response.getOutputStream();
        String checkCode = CheckCodeUtil.outputVerifyImage(100, 50, os, 4);

        // 存入Session
        HttpSession session = request.getSession();
        session.setAttribute("checkCodeGen", checkCode);
    }
}

registerService

    public boolean register(User user) {
        // 2.获取SqlSession
        SqlSession sqlSession = factory.openSession();

        // 3.获取UserMapper
        UserMapper mapper = sqlSession.getMapper(UserMapper.class);

        // 4.判断用户是否存在
        User u = mapper.selectByUsername(user.getUsername());

        if (u == null) {
            mapper.add(user);
            sqlSession.commit();
        }

        // 释放资源
        sqlSession.close();

        return u == null;
    }

register.jsp

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
<%@ page isELIgnored="false" %>



    
    欢迎注册
    




    
        欢迎注册
        已有帐号？ 登录
    
    

        

            
                用户名
                
                    
                    

                    ${register_msg}
                

            

            
                密码
                
                    
                    

                    密码格式有误
                
            


            
                验证码
                
                    
                    
                    看不清？

验证码库

package youth.util;

import javax.imageio.ImageIO;
import java.awt.*;
import java.awt.geom.AffineTransform;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.OutputStream;
import java.util.Arrays;
import java.util.Random;


public class CheckCodeUtil {

    public static final String VERIFY_CODES = "123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ";
    private static Random random = new Random();
    
    
    public static String outputVerifyImage(int w, int h, OutputStream os, int verifySize) throws IOException {
        String verifyCode = generateVerifyCode(verifySize);
        outputImage(w, h, os, verifyCode);
        return verifyCode;
    }

    
    public static String generateVerifyCode(int verifySize) {
        return generateVerifyCode(verifySize, VERIFY_CODES);
    }

    
    public static String generateVerifyCode(int verifySize, String sources) {
        // 未设定展示源的字码，赋默认值大写字母+数字
        if (sources == null || sources.length() == 0) {
            sources = VERIFY_CODES;
        }
        int codesLen = sources.length();
        Random rand = new Random(System.currentTimeMillis());
        StringBuilder verifyCode = new StringBuilder(verifySize);
        for (int i = 0; i < verifySize; i++) {
            verifyCode.append(sources.charAt(rand.nextInt(codesLen - 1)));
        }
        return verifyCode.toString();
    }

    
    public static String outputVerifyImage(int w, int h, File outputFile, int verifySize) throws IOException {
        String verifyCode = generateVerifyCode(verifySize);
        outputImage(w, h, outputFile, verifyCode);
        return verifyCode;
    }



    
    public static void outputImage(int w, int h, File outputFile, String code) throws IOException {
        if (outputFile == null) {
            return;
        }
        File dir = outputFile.getParentFile();
        //文件不存在
        if (!dir.exists()) {
            //创建
            dir.mkdirs();
        }
        try {
            outputFile.createNewFile();
            FileOutputStream fos = new FileOutputStream(outputFile);
            outputImage(w, h, fos, code);
            fos.close();
        } catch (IOException e) {
            throw e;
        }
    }

    
    public static void outputImage(int w, int h, OutputStream os, String code) throws IOException {
        int verifySize = code.length();
        BufferedImage image = new BufferedImage(w, h, BufferedImage.TYPE_INT_RGB);
        Random rand = new Random();
        Graphics2D g2 = image.createGraphics();
        g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);

        // 创建颜色集合，使用java.awt包下的类
        Color[] colors = new Color[5];
        Color[] colorSpaces = new Color[]{Color.WHITE, Color.CYAN,
                Color.GRAY, Color.LIGHT_GRAY, Color.MAGENTA, Color.ORANGE,
                Color.PINK, Color.YELLOW};
        float[] fractions = new float[colors.length];
        for (int i = 0; i < colors.length; i++) {
            colors[i] = colorSpaces[rand.nextInt(colorSpaces.length)];
            fractions[i] = rand.nextFloat();
        }
        Arrays.sort(fractions);
        // 设置边框色
        g2.setColor(Color.GRAY);
        g2.fillRect(0, 0, w, h);

        Color c = getRandColor(200, 250);
        // 设置背景色
        g2.setColor(c);
        g2.fillRect(0, 2, w, h - 4);

        // 绘制干扰线
        Random random = new Random();
        // 设置线条的颜色
        g2.setColor(getRandColor(160, 200));
        for (int i = 0; i < 20; i++) {
            int x = random.nextInt(w - 1);
            int y = random.nextInt(h - 1);
            int xl = random.nextInt(6) + 1;
            int yl = random.nextInt(12) + 1;
            g2.drawLine(x, y, x + xl + 40, y + yl + 20);
        }

        // 添加噪点
        // 噪声率
        float yawpRate = 0.05f;
        int area = (int) (yawpRate * w * h);
        for (int i = 0; i < area; i++) {
            int x = random.nextInt(w);
            int y = random.nextInt(h);
            // 获取随机颜色
            int rgb = getRandomIntColor();
            image.setRGB(x, y, rgb);
        }
        // 添加图片扭曲
        shear(g2, w, h, c);

        g2.setColor(getRandColor(100, 160));
        int fontSize = h - 4;
        Font font = new Font("Algerian", Font.ITALIC, fontSize);
        g2.setFont(font);
        char[] chars = code.toCharArray();
        for (int i = 0; i < verifySize; i++) {
            AffineTransform affine = new AffineTransform();
            affine.setToRotation(Math.PI / 4 * rand.nextDouble() * (rand.nextBoolean() ? 1 : -1), (w / verifySize) * i + fontSize / 2, h / 2);
            g2.setTransform(affine);
            g2.drawChars(chars, i, 1, ((w - 10) / verifySize) * i + 5, h / 2 + fontSize / 2 - 10);
        }

        g2.dispose();
        ImageIO.write(image, "jpg", os);
    }

    
    private static Color getRandColor(int fc, int bc) {
        if (fc > 255) {
            fc = 255;
        }
        if (bc > 255) {
            bc = 255;
        }
        int r = fc + random.nextInt(bc - fc);
        int g = fc + random.nextInt(bc - fc);
        int b = fc + random.nextInt(bc - fc);
        return new Color(r, g, b);
    }

    private static int getRandomIntColor() {
        int[] rgb = getRandomRgb();
        int color = 0;
        for (int c : rgb) {
            color = color << 8;
            color = color | c;
        }
        return color;
    }

    private static int[] getRandomRgb() {
        int[] rgb = new int[3];
        for (int i = 0; i < 3; i++) {
            rgb[i] = random.nextInt(255);
        }
        return rgb;
    }

    private static void shear(Graphics g, int w1, int h1, Color color) {
        shearX(g, w1, h1, color);
        shearY(g, w1, h1, color);
    }

    private static void shearX(Graphics g, int w1, int h1, Color color) {

        int period = random.nextInt(2);

        boolean borderGap = true;
        int frames = 1;
        int phase = random.nextInt(2);

        for (int i = 0; i < h1; i++) {
            double d = (double) (period >> 1)
                    * Math.sin((double) i / (double) period
                    + (6.2831853071795862D * (double) phase)
                    / (double) frames);
            g.copyArea(0, i, w1, 1, (int) d, 0);
            if (borderGap) {
                g.setColor(color);
                g.drawLine((int) d, i, 0, i);
                g.drawLine((int) d + w1, i, w1, i);
            }
        }

    }

    private static void shearY(Graphics g, int w1, int h1, Color color) {

        int period = random.nextInt(40) + 10; // 50;

        boolean borderGap = true;
        int frames = 20;
        int phase = 7;
        for (int i = 0; i < w1; i++) {
            double d = (double) (period >> 1)
                    * Math.sin((double) i / (double) period
                    + (6.2831853071795862D * (double) phase)
                    / (double) frames);
            g.copyArea(i, 0, 1, h1, 0, (int) d);
            if (borderGap) {
                g.setColor(color);
                g.drawLine(i, (int) d, i, 0);
                g.drawLine(i, (int) d + h1, i, h1);
            }

        }

    }
}

七、Flitter

@WebFilter("

    axios.get("http://localhost:8080/ajax-demo/axiosServlet?username=zhangsan").then(function (resp) {
        alert(resp.data);
    })



    //2. post
    

    axios.post("http://localhost:8080/ajax-demo/axiosServlet","username=zhangsan").then(function (resp) {
        alert(resp.data);
    })


    var jsObject = {name:"zhangsan"};

    axios({
        method:"post",
        url:"http://localhost:8080/ajax-demo/axiosServlet",
        data:jsObject
    }).then(function (resp) {
        alert(resp.data);
    })




    
    Title

JsonServlet

package com.itheima.json;

import com.alibaba.fastjson.JSON;

public class FastJsonDemo {

    public static void main(String[] args) {
        //1. 将Java对象转为JSON字符串
        User user = new User();
        user.setId(1);
        user.setUsername("zhangsan");
        user.setPassword("123");

        String jsonString = JSON.toJSONString(user);
        System.out.println(jsonString);//{"id":1,"password":"123","username":"zhangsan"}


        //2. 将JSON字符串转为Java对象

        User u = JSON.parseObject("{"id":1,"password":"123","username":"zhangsan"}", User.class);
        System.out.println(u);


    }
}

十、Vue




    
    Title



    
    
    {{username}}




    
    Title



    点击一下
    点击一下

1、常用指令




    
    Title




    
    Title



    div1
    div2
    div3
    
    div v-show




    
    Title



    
        {{addr}} 

    
    
    
        {{i+1}}--{{addr}}

2、生命周期




    
    Title



    
        {{addr}} 

    
    
    
        {{i+1}}--{{addr}}




    
    Title




    

    
    
        
            序号
            品牌名称
            企业名称
            排序
            品牌介绍
            状态
            操作
        
        
        
            {{i + 1}}
            {{brand.brandName}}
            {{brand.companyName}}
            {{brand.ordered}}
            {{brand.description}}
            {{brand.statusStr}}
            修改 删除

序号	品牌名称	企业名称	排序	品牌介绍	状态	操作
{{i + 1}}	{{brand.brandName}}	{{brand.companyName}}	{{brand.ordered}}	{{brand.description}}	{{brand.statusStr}}	修改删除




    
    Title


添加品牌

    品牌名称：

    企业名称：

    排序：

    描述信息：

    状态：
    禁用
    启用

十一、ElementUI

总结

提示：这里对文章进行总结：

用户名	${register_msg}
密码	密码格式有误
验证码	看不清？

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