JavaWeb基础1-1

JavaWeb基础1-1

一、Maven

常用的Maven仓库

用pom.xml文件表示：

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<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>org.example</groupId>
    <artifactId>New_Maven_1</artifactId>
    <version>1.0-SNAPSHOT</version>
    <packaging>war</packaging>

    <properties>
        <maven.compiler.source>8</maven.compiler.source>
        <maven.compiler.target>8</maven.compiler.target>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
    </properties>

    <build>
        <plugins>
            <plugin>
                <!--Tomcat-->
                <groupId>org.apache.tomcat.maven</groupId>
                <artifactId>tomcat7-maven-plugin</artifactId>
                <version>2.2</version>
                <configuration>
                    <port>8080</port>
                    <path>/</path>
                </configuration>
            </plugin>
        </plugins>
    </build>
    <dependencies>
        <!--servlet-->
        <dependency>
            <groupId>javax.servlet</groupId>
            <artifactId>javax.servlet-api</artifactId>
            <version>3.1.0</version>
            <scope>provided</scope>
        </dependency>

        <!--IO流工具类-->
        <dependency>
            <groupId>commons-io</groupId>
            <artifactId>commons-io</artifactId>
            <version>2.11.0</version>
        </dependency>

        <!--Mybatis-->
        <dependency>
            <groupId>org.mybatis</groupId>
            <artifactId>mybatis</artifactId>
            <version>3.5.6</version>
        </dependency>

        <!--MySQL-->
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>8.0.33</version>
        </dependency>

        <!--JSP-->
        <dependency>
            <groupId>javax.servlet.jsp</groupId>
            <artifactId>jsp-api</artifactId>
            <version>2.2</version>
            <scope>provided</scope>
        </dependency>

        <!--JSTL/jsp依赖-->
        <dependency>
            <groupId>jstl</groupId>
            <artifactId>jstl</artifactId>
            <version>1.2</version>
        </dependency>

        <!--JSTL依赖-->
        <dependency>
            <groupId>taglibs</groupId>
            <artifactId>standard</artifactId>
            <version>1.1.2</version>
        </dependency>
        
        <!--fastjson-->
        <dependency>
            <groupId>com.alibaba</groupId>
            <artifactId>fastjson</artifactId>
            <version>1.2.83</version>
        </dependency>

    </dependencies>


</project>

二、MyBatis

优秀的持久层框架，简化JDBC的开发

JavaEE的三层：表现层、业务层、持久层

可以理解为Java程序与数据库的连接和交换方式

三、Mapper

首先注意映射关系，如图：

1、写在xml文件中的方法

BrandMapper.xml

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<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper
        PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
        "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="com.study.mapper.BrandMapper">
    <resultMap id="brandResultMap" type="brand">
        <result column="brand_name" property="brandName"></result>
        <result column="company_name" property="companyName"></result>
    </resultMap>
</mapper>

BrandMapper.java

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package com.study.mapper;

import org.apache.ibatis.annotations.ResultMap;
import org.apache.ibatis.annotations.Select;
import com.study.pojo.Brand;
import java.util.List;

public interface BrandMapper {

    /**
     * 查询所有
     * @return
     */
    @Select("select * from tb_brand")
    @ResultMap("brandResultMap")
    List<Brand> selectAll();
}

2、全部写在注释中的方法

UserMapper.xml

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<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper
        PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
        "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="User.mapper.UserMapper">

</mapper>

UserMapper.java

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package User.mapper;
import User.pojo.User;
import org.apache.ibatis.annotations.Insert;
import org.apache.ibatis.annotations.Param;
import org.apache.ibatis.annotations.Select;

public interface UserMapper {

    /**
     * 根据用户名和密码查询用户对象
     * @param username
     * @param password
     * @return
     */
    @Select("select * from tb_user where username = #{username} and password = #{password}")
    User select(@Param("username") String username, @Param("password") String password);

    /**
     * 根据用户名查询用户对象
     * @param username
     * @return
     */
    @Select("select * from tb_user where username = #{username}")
    User selectByUsername(@Param("username") String username);

    /**
     * 添加用户
     * @param user
     */
    @Insert("insert into tb_user values(null,#{username},#{password})")
    void add(User user);

}

四、Tomcat

一个网络服务框架

可以本地配置，也可以Maven导入一个插件

同时注意，Tomcat9及之前的版本默认的编码格式不是UTF-8，是ISO-8859-1，Tomcat10是UTF-8，可能会出现中文乱码的问题

GET的解决方式：

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@WebServlet("/resp3")
public class ResponseDemo3 extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        String username = "张三";
        //1.URL编码
//        String encode = URLEncoder.encode(username, "utf-8");
//        System.out.println(encode);
        //2.URL解码
//        String decode = URLDecoder.decode(username, "utf-8");
//        System.out.println(decode);
        //3.转化为字节数据
//        byte[] bytes = decode.getBytes("ISO-8859-1");
//        for(byte b : bytes) {
//            System.out.println(b + " ");
//        }
        //4.将字节数组转化为字符串
//        String s = new String(bytes, "utf-8");
//        System.out.println(s);

        //一行代码解决
        String s = new String(username.getBytes("ISO-8859-1"),"utf-8");

    }
}

POST的解决方式：

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@WebServlet("/resp3")
public class ResponseDemo3 extends HttpServlet {

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        resp.setContentType("text/html;charset=utf-8");
        //设置字符输入流的编码，这样就可以了
    }
}

五、Servlet

1、Request和Response

使用Request对象来【获取请求】数据

使用Response对象来【设置相应】数据

一般格式：

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@WebServlet("/resp2")
//Web访问的路径
public class ResponseDemo2 extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        //设置响应类型
        resp.setContentType("text/html;charset=utf-8");
        //通过Response对象获取输出流
        PrintWriter writer = resp.getWriter();
        //写数据
        writer.write("resp2");
    }

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

2、SqlSessionFactory

一般要抽取一个SqlSessionFactory工具类

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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;
    }
}

相关的调用和替代：

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@WebServlet("/request-demo/registerServlet")
public class RegisterServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {

    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        //1.接受用户数据
        String username = req.getParameter("username");
        String password = req.getParameter("password");

        //2.封装用户对象
        User user = new User();
        user.setUsername(username);
        user.setPassword(password);

        //3.调用mapper，根据用户名查询用户对象
//        String resource = "mybatis-config.xml";
//        InputStream inputStream = Resources.getResourceAsStream(resource);
//        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
//        上面为旧方法，下面用调用静态方法解决：
        SqlSessionFactory sqlSessionFactory = SqlSessionFactoryUtils.getSqlSessionFactory();

        SqlSession sqlSession = sqlSessionFactory.openSession();
        UserMapper userMapper = sqlSession.getMapper(UserMapper.class);
        User u = userMapper.selectByUsername(username);

        //4.判断对象是否存在
        if (u == null) {
            //用户名不存在，添加用户
            userMapper.add(user);
            sqlSession.commit();
            sqlSession.close();
            resp.setContentType("text/html;charset=utf-8");
            resp.getWriter().write("注册成功");
        } else {
            //用户已存在，提示
            resp.setContentType("text/html;charset=utf-8");
            resp.getWriter().write("用户已存在");
        }

    }
}

六、JSP

先导入最先的需要的Maven库和其依赖

1、Java Server Pages/Java服务端页面

一种动态的网页技术，可以定义HTML、JS、CSS等静态内容，还可以定义Java代码的动态内容

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<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>Title</title>
</head>
<body>
    <%
        System.out.println("hello");
    	//在这里写Java
    %>
</body>
</html>

2、EL表达式和JSTL

EL表达式特点（四大域对象）

ServletDemo1设定：
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@WebServlet("/JSTL")
public class ServletDemo1 extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        //1.存储到request域中
        req.setAttribute("username", "NewUserRequest");
        req.setAttribute("status",1);

        //2.转发到el-demo.jps
        req.getRequestDispatcher("/el-demo.jsp-demo.jsp").forward(req,resp);
    
        //3.遍历粗存的举例
        List<String> list = new ArrayList<>();
        list.add("aaa");
        list.add("bbb");
        list.add("ccc");
    }

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

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

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
<%--if判断--%>
    <c:if test="${status} == 1">
        <h1>Test Successful</h1>
    </c:if>
    <c:if test="${status} == 0">
        <h1>Test fail</h1>
    </c:if>
<%--for遍历--%>
    <c:forEach items="${list}" var="item">
        <h1>${item}</h1>
    </c:forEach>
</body>
</html>

3、MVC模式和三层架构

七、Cookie和Session

1、Cookie

Cookie的概念：

Cookie: 客户端会话技术，将数据保存到客户端，以后每次请求都携带Cookie数据进行访问。

Cookie的使用：
储存：
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@WebServlet("/aServlet")
public class AServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        //1.创建Cookie对象
        Cookie cookie = new Cookie("username", "NewUser");
        //设置存活时间
        cookie.setMaxAge(60*60*24*1);
        //2.发送Cookie
        resp.addCookie(cookie);
    }
    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        super.doPost(req, resp);
    }
}
读取：
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@WebServlet("/bServlet")
public class BServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        //1.获取Cookie数组
        Cookie[] cookies = req.getCookies();
        //2.遍历数组
        for (Cookie cookie : cookies) {
            String name = cookie.getName();
            if("username".equals(name)){
                String value = cookie.getValue();
                System.out.println(name + ":" + value);
            }
            break;
        }
    }
    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        super.doPost(req, resp);
    }
}
Cookie不能直接储存中文，要进行URL编码：
储存：
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@WebServlet("/aServlet")
public class AServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        //1.创建Cookie对象
        //1-1.创建中文字符串
        String value = "张三";
        //1-2.URL编码
        value = URLEncoder.encode(value, "UTF-8");
        Cookie cookie = new Cookie("username", value);
        //设置存活时间
        cookie.setMaxAge(60*60*24*1);
        //2.发送Cookie
        resp.addCookie(cookie);
    }
    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        super.doPost(req, resp);
    }
}
读取：
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@WebServlet("/bServlet")
public class BServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        //1.获取Cookie数组
        Cookie[] cookies = req.getCookies();
        //2.遍历数组
        for (Cookie cookie : cookies) {
            String name = cookie.getName();
            if("username".equals(name)){
                String value = cookie.getValue();
                //URL解码
                value = URLDecoder.decode(value, "utf-8");
                System.out.println(name + ":" + value);
            }
            break;
        }
    }
    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        super.doPost(req, resp);
    }
}

2、Session

服务端会话跟踪技术，将数据保存到服务端

Session是基于Cookie实现

基本用法：
储存：
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@WebServlet(name = "SessionDemo1", value = "/SessionDemo1")
public class SessionDemo1 extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //1.获取Session对象
        HttpSession session = request.getSession();
        //2.存储对象
        session.setAttribute("username", "NewUserSession");
    }
    @Override
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    }
}
读取：
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@WebServlet(name = "SessionDemo2", value = "/SessionDemo2")
public class SessionDemo2 extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        HttpSession session = request.getSession();
        Object username = session.getAttribute("username");
        System.out.println(username);
    }
}
Java > JavaWeb
#JavaWeb
JavaWeb基础1-1
https://davidpenn888.github.io/2023/05/16/JavaWeb_1_1/
作者
David Penn
发布于
2023年5月16日
许可协议