JavaWeb小项目练习(基于三层架构实现登录，对表增，删，改，查的操作)

?一 创建项目并修改项目结构

File->New->Project新建一个名为javaweb01的工程

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javaweb01->New->Module新建一个名为MyManage的模块

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将MyManage模块设置为支持web项目

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将web项目重命名并移动到main路径下

配置pom文件(文件依赖,打包方式,以及支持加载的文件)

<?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>
    <parent>
        <groupId>com.by</groupId>
        <artifactId>javaweb</artifactId>
        <version>1.0-SNAPSHOT</version>
    </parent>

    <artifactId>MyManage</artifactId>
<!--    项目打包方式-->
    <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>
    <dependencies>
<!--        依赖Servlet-->
        <dependency>
            <groupId>javax.servlet</groupId>
            <artifactId>servlet-api</artifactId>
            <version>2.5</version>
        </dependency>

<!--        依赖Mybatis-->
        <dependency>
            <groupId>org.mybatis</groupId>
            <artifactId>mybatis</artifactId>
            <version>3.4.5</version>
        </dependency>
<!--        依赖mysql-->
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>5.1.47</version>
        </dependency>
<!--        依赖log4j-->
        <dependency>
            <groupId>log4j</groupId>
            <artifactId>log4j</artifactId>
            <version>1.2.17</version>
        </dependency>
<!--        依赖jsp-api-->
        <dependency>
            <groupId>javax.servlet.jsp</groupId>
            <artifactId>jsp-api</artifactId>
            <version>2.0</version>
        </dependency>
<!--       依赖jstl-->
        <dependency>
            <groupId>jstl</groupId>
            <artifactId>jstl</artifactId>
            <version>1.2</version>
        </dependency>
    </dependencies>
    <build>
        <!-- 如果不添加此节点src/main/java目录下的所有配置文件都会被漏掉。 -->
        <resources>
            <resource>
                <directory>src/main/java</directory>
                <includes>
                    <include>**/*.xml</include>
                </includes>
            </resource>
            <!--让idea识别resources目录-->
            <resource>
                <directory>src/main/resources</directory>
            </resource>
        </resources>
    </build>

</project>

二 使用三层架构和配置文件以及Tomcat服务器

创建三层架构的包(表现层)servlet,(业务逻辑层)service serviceimpl,(数据访问层)mapper

加载配置文件(数据库配置文件,日志文件,MyBatis配置文件)

数据库配置文件db.properties

jdbc.driver=com.mysql.jdbc.Driver
jdbc.url=jdbc:mysql://localhost:3305/servlet?characterEncoding=UTF-8
jdbc.username=root
jdbc.password=

日志文件log4j.properties

# Global logging configuration
log4j.rootLogger=DEBUG, stdout
# Console output...
log4j.appender.stdout=org.apache.log4j.ConsoleAppender
log4j.appender.stdout.layout=org.apache.log4j.PatternLayout
log4j.appender.stdout.layout.ConversionPattern=%5p [%t] - %m%n

MyBatis配置文件mybatis-config.xml

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE configuration PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
        "http://mybatis.org/dtd/mybatis-3-config.dtd">
<configuration>
    <properties resource="db.properties"></properties>
    <typeAliases>
        <package name="com.by.pojo"/>
    </typeAliases>
    <!-- 数据库连接信息 -->
    <environments default="development">
        <environment id="development">
            <transactionManager type="JDBC"/>
            <dataSource type="POOLED">
                <property name="driver" value="${jdbc.driver}"/>
                <property name="url" value="${jdbc.url}"/>
                <property name="username" value="${jdbc.username}"/>
                <property name="password" value="${jdbc.password}"/>
            </dataSource>
        </environment>
    </environments>
    <!-- 扫描映射文件 -->
    <mappers>
<!--        <mapper resource="com/by/dao/UserDao.xml"/>-->
        <package name="com.by.mapper"/>
    </mappers>
</configuration>

项目结构

Tomcat服务器

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三 监听和过滤

监听器

SqlSession回话实例从始至终都使用,所以在将SqlSession装在ServletContext里边

新建com->by->listener->MyServletContxtListenerlei

public class MyServletContxtListener implements ServletContextListener {

    @Override
    public void contextInitialized(ServletContextEvent servletContextEvent) {
        try {
            //加载配置文件
            String resource = "mybatis-config.xml";
            InputStream inputStream = Resources.getResourceAsStream(resource);

            //创建SessionFactory
            SqlSessionFactory sessionFactory = new SqlSessionFactoryBuilder().build(inputStream);

            //使用数据的会话实例
            SqlSession sqlSession = sessionFactory.openSession();
            //把sqlSession对象撞到servletContext中
            ServletContext servletContext = servletContextEvent.getServletContext();
            servletContext.setAttribute("sqlSession", sqlSession);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    @Override
    public void contextDestroyed(ServletContextEvent servletContextEvent) {

    }
}

web.xml

<!--配置监听器-->
    <listener>
        <listener-class>com.by.listener.MyServletContxtListener</listener-class>
    </listener>

过滤器

因为文件请求和响应需要防止字符编码格式不一样而导致乱码,所以我们采用过滤器技术过滤每一个servlet文件

新建com->by->filter->CharacterEncodingFilter

public class CharacterEncodingFilter implements Filter {

    @Override
    public void init(FilterConfig filterConfig) throws ServletException {

    }
    @Override
    public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
        //请求中文乱码
        servletRequest.setCharacterEncoding("utf-8");
        //响应中文乱码
        servletResponse.setContentType("text/html;charset=utf-8");
        //放行filter
        filterChain.doFilter(servletRequest, servletResponse);
    }

    @Override
    public void destroy() {

    }
}

pojo包下新建User类

package com.by.pojo;

public class User {
    private Integer id;
    private String username;
    private String password;
    private String sex;
    private String address;
    private Integer age;

    public User(Integer id, String username, String password, String sex, Integer age, String address) {
        this.id = id;
        this.username = username;
        this.password = password;
        this.sex = sex;
        this.address = address;
        this.age = age;
    }

    public User(String username, String password, String sex, Integer age, String address) {
        this.username = username;
        this.password = password;
        this.sex = sex;
        this.address = address;
        this.age = age;
    }

    public User() {
    }

    public Integer getAge() {
        return age;
    }

    public void setAge(Integer age) {
        this.age = age;
    }

    public Integer getId() {
        return id;
    }

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

    public String getUsername() {
        return username;
    }

    public void setUsername(String username) {
        this.username = username;
    }

    public String getPassword() {
        return password;
    }

    public void setPassword(String password) {
        this.password = password;
    }

    public String getSex() {
        return sex;
    }

    public void setSex(String sex) {
        this.sex = sex;
    }

    public String getAddress() {
        return address;
    }

    public void setAddress(String address) {
        this.address = address;
    }
}

web.xml

<!--    过滤器-->
    <filter>
        <filter-name>characterEncodingFilter</filter-name>
        <filter-class>com.by.filter.CharacterEncodingFilter</filter-class>
    </filter>
    <filter-mapping>
        <filter-name>characterEncodingFilter</filter-name>
        <!--*代表任意请求-->
        <url-pattern>/*</url-pattern>
    </filter-mapping>

三 登录验证并查询数据表内容

login.jsp

<%--
  Created by IntelliJ IDEA.
  User: 21309
  Date: 2023-12-27
  Time: 16:05
  To 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>用户管理系统</h1>
  <form action="login" method="post">
    账号：<input type="text" name="username"><br>
    密码：<input type="text" name="password"><br>
    <input type="submit" value="登录">
  </form>
  </body>
</html>

web.xml

<!--设置欢迎页为Login.jsp-->
    <welcome-file-list>
        <welcome-file>login.jsp</welcome-file>
    </welcome-file-list>

在servlet包下新建LoginServlet

//表现层
public class LoginServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        doPost(req, resp);
    }
    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        //根据input标签的name属性获取前端提交的参数
        String username = req.getParameter("username");
        String password = req.getParameter("password");
        //调用service
        UserService userService = new UserServiceImpl(this);
        //将获得的username，password传递给User
        User user=userService.login(username,password);
        //登录判断
        if (user!=null){
        //如果登录成功，则跳转到select_user.jsp
        resp.sendRedirect("selectUserServlet");
        }else {
        //如果登录失败，则跳转到login.jsp
        req.getRequestDispatcher("login.jsp").forward(req,resp);
        }
    }
}

web.xml

<!--login页-->
    <servlet>
        <servlet-name>login</servlet-name>
        <servlet-class>com.by.servlet.LoginServlet</servlet-class>
    </servlet>
    <servlet-mapping>
        <servlet-name>login</servlet-name>
        <url-pattern>/login</url-pattern>
    </servlet-mapping>

以下内容可在servlet类中Alt+Enter快捷键出来(先把Servlet类写完整)

在service包下的UserService接口

public interface UserService {
    User login(String username, String password);
}

UserServiceImpl类

public class UserServiceImpl implements UserService {
    private SqlSession sqlSession;
    private UserMapper userMapper;
    //加载UserMapper类
    public UserServiceImpl(HttpServlet httpServlet) {
        ServletContext servletContext = httpServlet.getServletContext();
        sqlSession = (SqlSession) servletContext.getAttribute("sqlSession");
        userMapper = sqlSession.getMapper(UserMapper.class);
    }
@Override
    public User login(String username, String password) {
        //调用dao
        return userMapper.login(username,password);
    }
}

mapper包下的UserMapper接口

public interface UserMapper {
     User login(@Param("username") String username, @Param("password") String password);
}

mapper包下的UserMapper.xml接口

<?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.by.mapper.UserMapper">
    <select id="login" resultType="com.by.pojo.User">
        SELECT * FROM user WHERE username=#{username} AND password=#{password}
    </select>
    <select id="selectUser" resultType="com.by.pojo.User">
        SELECT * FROM user
    </select>
</mapper>

登陆页面要要跳到select_user.jsp页面

在servlet包下新建SelectUserServlet

public class SelectUserServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        doPost(req, resp);
    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        //调用UserService查询List<User>
        UserService userService = new UserServiceImpl(this);
        List<User> userList = userService.selectUser();

        //把List<User>送到select_user.jsp
        req.setAttribute("userList", userList);
        req.getRequestDispatcher("select_user.jsp").forward(req, resp);
    }
}

web.xml

<!--    selectUserServlet-->
    <servlet>
        <servlet-name>selectUserServlet</servlet-name>
        <servlet-class>com.by.servlet.SelectUserServlet</servlet-class>
    </servlet>
    <servlet-mapping>
        <servlet-name>selectUserServlet</servlet-name>
        <url-pattern>/selectUserServlet</url-pattern>
    </servlet-mapping>

以下内容可在servlet类中Alt+Enter快捷键出来(先把Servlet类写完整)

在service包下的UserService接口

public interface UserService {

    User login(String username, String password);

    List<User> selectUser();
}

UserServiceImpl类

public class UserServiceImpl implements UserService {
    private SqlSession sqlSession;
    private UserMapper userMapper;
    //加载UserMapper类
    public UserServiceImpl(HttpServlet httpServlet) {
        ServletContext servletContext = httpServlet.getServletContext();
        sqlSession = (SqlSession) servletContext.getAttribute("sqlSession");
        userMapper = sqlSession.getMapper(UserMapper.class);
    }

    @Override
    public User login(String username, String password) {
        //调用dao
        return userMapper.login(username,password);
    }

    @Override
    public List<User> selectUser() {
        return userMapper.selectUser();
    }
}

mapper包下的UserMapper接口

public interface UserMapper {
    User login(@Param("username") String username, @Param("password") String password);

    List<User> selectUser();
}

mapper包下的UserMapper.xml接口

<?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.by.mapper.UserMapper">
    <select id="login" resultType="com.by.pojo.User">
        SELECT * FROM user WHERE username=#{username} AND password=#{password}
    </select>
    <select id="selectUser" resultType="com.by.pojo.User">
        SELECT * FROM user
    </select>
</mapper>

测试结果

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四 新增数据

在select_user.jsp添加新增链接

新建add_user.jsp

<%--
  Created by IntelliJ IDEA.
  User: Hero
  Date: 2023/12/29
  Time: 11:01
  To 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>新增</h1>
<form action="addUser" method="post">
    账号：<input type="text" name="username"><br>
    密码：<input type="text" name="password"><br>
    性别：<input type="text" name="sex"><br>
    年龄：<input type="text" name="age"><br>
    地址：<input type="text" name="address"><br>
    <input type="submit" value=" 新  增 ">
</form>
</body>
</html>

在servlet包下新建addUser

public class addUser extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        doPost(req, resp);
    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        //1、接收参数
        String username = req.getParameter("username");
        String password = req.getParameter("password");
        String sex = req.getParameter("sex");
        Integer age = Integer.valueOf(req.getParameter("age"));
        String address = req.getParameter("address");
        User user = new User(username, password, sex, age, address);

        //2、调用service，把user保存到数据库
        UserService userService = new UserServiceImpl(this);
        userService.addUser(user);

        //3、重定向到SelectUserServlet
        resp.sendRedirect("selectUserServlet");
    }
}

web.xml

<!--    addUser-->
    <servlet>
        <servlet-name>addUser</servlet-name>
        <servlet-class>com.by.servlet.addUser</servlet-class>
    </servlet>
    <servlet-mapping>
        <servlet-name>addUser</servlet-name>
        <url-pattern>/addUser</url-pattern>
    </servlet-mapping>

以下内容可在servlet类中Alt+Enter快捷键出来(先把Servlet类写完整)

在service包下的UserService接口

public interface UserService {

    User login(String username, String password);

    List<User> selectUser();

    void addUser(User user);
}

UserServiceImpl类

public class UserServiceImpl implements UserService {
    private SqlSession sqlSession;
    private UserMapper userMapper;
    //加载UserMapper类
    public UserServiceImpl(HttpServlet httpServlet) {
        ServletContext servletContext = httpServlet.getServletContext();
        sqlSession = (SqlSession) servletContext.getAttribute("sqlSession");
        userMapper = sqlSession.getMapper(UserMapper.class);
    }

    @Override
    public User login(String username, String password) {
        //调用dao
        return userMapper.login(username,password);
    }

    @Override
    public List<User> selectUser() {
        return userMapper.selectUser();
    }

    @Override
    public void addUser(User user) {
        userMapper.addUser(user);
        sqlSession.commit();
    }
}

mapper包下的UserMapper接口

public interface UserMapper {
    User login(@Param("username") String username, @Param("password") String password);

    List<User> selectUser();

    void addUser(User user);
}

mapper包下的UserMapper.xml接口

<?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.by.mapper.UserMapper">
    <select id="login" resultType="com.by.pojo.User">
        SELECT * FROM user WHERE username=#{username} AND password=#{password}
    </select>
    <select id="selectUser" resultType="com.by.pojo.User">
        SELECT * FROM user
    </select>
<!--   insert-->
    <insert id="addUser" parameterType="com.by.pojo.User">
        INSERT INTO user
        <trim prefix="(" suffix=")" suffixOverrides=",">
            <if test="username!=null and username!=''">
                username,
            </if>
            <if test="password!=null and password!=''">
                password,
            </if>
            <if test="sex!=null and sex!=''">
                sex,
            </if>
            <if test="age!=null">
                age,
            </if>
            <if test="address!=null and address!=''">
                address,
            </if>
        </trim>
        VALUES
        <trim prefix="(" suffix=")" suffixOverrides=",">
            <if test="username!=null and username!=''">
                #{username},
            </if>
            <if test="password!=null and password!=''">
                #{password},
            </if>
            <if test="sex!=null and sex!=''">
                #{sex},
            </if>
            <if test="age!=null">
                #{age},
            </if>
            <if test="address!=null and address!=''">
                #{address},
            </if>
        </trim>
    </insert>
</mapper>

测试结果

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五 删除数据

在select_user.jsp添加删除链接

在servlet包下新建DeleteUserServlet

public class UpdateUserServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        doPost(req, resp);
    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        //1、接收参数
        Integer id = Integer.valueOf(req.getParameter("id"));
        String username = req.getParameter("username");
        String password = req.getParameter("password");
        String sex = req.getParameter("sex");
        Integer age = Integer.valueOf(req.getParameter("age"));
        String address = req.getParameter("address");
        User user = new User(id, username, password, sex, age, address);

        //2、调用service，修改user
        UserService userService = new UserServiceImpl(this);
        userService.updateUserById(user);

        //3、重定向到SelectUserServlet
        resp.sendRedirect("selectUserServlet");
    }
}

web.xml

 <!--    delete-->
    <servlet>
        <servlet-name>deleteUser</servlet-name>
        <servlet-class>com.by.servlet.DeleteUserServlet</servlet-class>
    </servlet>
    <servlet-mapping>
        <servlet-name>deleteUser</servlet-name>
        <url-pattern>/deleteUser</url-pattern>
    </servlet-mapping>

以下内容可在servlet类中Alt+Enter快捷键出来(先把Servlet类写完整)

在service包下的UserService接口

public interface UserService {

    User login(String username, String password);

    List<User> selectUser();

    void addUser(User user);

    void deleteUser(Integer id);
}

UserServiceImpl类

public class UserServiceImpl implements UserService {
    private SqlSession sqlSession;
    private UserMapper userMapper;
    //加载UserMapper类
    public UserServiceImpl(HttpServlet httpServlet) {
        ServletContext servletContext = httpServlet.getServletContext();
        sqlSession = (SqlSession) servletContext.getAttribute("sqlSession");
        userMapper = sqlSession.getMapper(UserMapper.class);
    }

    @Override
    public User login(String username, String password) {
        //调用dao
        return userMapper.login(username,password);
    }

    @Override
    public List<User> selectUser() {
        return userMapper.selectUser();
    }

    @Override
    public void addUser(User user) {
        userMapper.addUser(user);
        sqlSession.commit();
    }

    @Override
    public void deleteUser(Integer id) {
        userMapper.deleteUser(id);
        sqlSession.commit();
    }
}

mapper包下的UserMapper接口

public interface UserMapper {
    User login(@Param("username") String username, @Param("password") String password);

    List<User> selectUser();

    void addUser(User user);

    void deleteUser(Integer id);
}

mapper包下的UserMapper.xml接口

<?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.by.mapper.UserMapper">
    <select id="login" resultType="com.by.pojo.User">
        SELECT * FROM user WHERE username=#{username} AND password=#{password}
    </select>
    <select id="selectUser" resultType="com.by.pojo.User">
        SELECT * FROM user
    </select>
<!--   insert-->
    <insert id="addUser" parameterType="com.by.pojo.User">
        INSERT INTO user
        <trim prefix="(" suffix=")" suffixOverrides=",">
            <if test="username!=null and username!=''">
                username,
            </if>
            <if test="password!=null and password!=''">
                password,
            </if>
            <if test="sex!=null and sex!=''">
                sex,
            </if>
            <if test="age!=null">
                age,
            </if>
            <if test="address!=null and address!=''">
                address,
            </if>
        </trim>
        VALUES
        <trim prefix="(" suffix=")" suffixOverrides=",">
            <if test="username!=null and username!=''">
                #{username},
            </if>
            <if test="password!=null and password!=''">
                #{password},
            </if>
            <if test="sex!=null and sex!=''">
                #{sex},
            </if>
            <if test="age!=null">
                #{age},
            </if>
            <if test="address!=null and address!=''">
                #{address},
            </if>
        </trim>
    </insert>
<!--    delete-->
    <delete id="deleteUser" parameterType="int">
        DELETE FROM user WHERE id=#{id}
    </delete>
</mapper>

测试结果

六 更新数据

在select_user.jsp增加修改链接

修改数据首先要获取被修改的数据

获取被修改的数据

在servlet包下新建GetUserServlet

public class GetUserServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        doPost(req, resp);
    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        //1、接收参数
        Integer id = Integer.valueOf(req.getParameter("id"));
        //2、调用service，根据id查询user
        UserService userService = new UserServiceImpl(this);
        User user = userService.getUserById(id);

        //3、user送到update_user.jsp
        req.setAttribute("user", user);
        req.getRequestDispatcher("update_user.jsp").forward(req, resp);
    }
}

web.xml

 <!--    GetUserServlet-->
    <servlet>
        <servlet-name>getUserServlet</servlet-name>
        <servlet-class>com.by.servlet.GetUserServlet</servlet-class>
    </servlet>
    <servlet-mapping>
        <servlet-name>getUserServlet</servlet-name>
        <url-pattern>/getUserById</url-pattern>
    </servlet-mapping>

以下内容可在servlet类中Alt+Enter快捷键出来(先把Servlet类写完整)

在service包下的UserService接口

public interface UserService {

    User login(String username, String password);

    List<User> selectUser();

    void addUser(User user);

    void deleteUser(Integer id);

    User getUserById(Integer id);
}

UserServiceImpl类

public class UserServiceImpl implements UserService {
    private SqlSession sqlSession;
    private UserMapper userMapper;
    //加载UserMapper类
    public UserServiceImpl(HttpServlet httpServlet) {
        ServletContext servletContext = httpServlet.getServletContext();
        sqlSession = (SqlSession) servletContext.getAttribute("sqlSession");
        userMapper = sqlSession.getMapper(UserMapper.class);
    }

    @Override
    public User login(String username, String password) {
        //调用dao
        return userMapper.login(username,password);
    }

    @Override
    public List<User> selectUser() {
        return userMapper.selectUser();
    }

    @Override
    public void addUser(User user) {
        userMapper.addUser(user);
        sqlSession.commit();
    }

    @Override
    public void deleteUser(Integer id) {
        userMapper.deleteUser(id);
        sqlSession.commit();
    }

    @Override
    public User getUserById(Integer id) {
        return userMapper.getUserById(id);
    }
}

mapper包下的UserMapper接口

public interface UserMapper {
    User login(@Param("username") String username, @Param("password") String password);

    List<User> selectUser();

    void addUser(User user);

    void deleteUser(Integer id);

    User getUserById(Integer id);
}

mapper包下的UserMapper.xml接口

<?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.by.mapper.UserMapper">
    <select id="login" resultType="com.by.pojo.User">
        SELECT * FROM user WHERE username=#{username} AND password=#{password}
    </select>
    <select id="selectUser" resultType="com.by.pojo.User">
        SELECT * FROM user
    </select>
<!--   insert-->
    <insert id="addUser" parameterType="com.by.pojo.User">
        INSERT INTO user
        <trim prefix="(" suffix=")" suffixOverrides=",">
            <if test="username!=null and username!=''">
                username,
            </if>
            <if test="password!=null and password!=''">
                password,
            </if>
            <if test="sex!=null and sex!=''">
                sex,
            </if>
            <if test="age!=null">
                age,
            </if>
            <if test="address!=null and address!=''">
                address,
            </if>
        </trim>
        VALUES
        <trim prefix="(" suffix=")" suffixOverrides=",">
            <if test="username!=null and username!=''">
                #{username},
            </if>
            <if test="password!=null and password!=''">
                #{password},
            </if>
            <if test="sex!=null and sex!=''">
                #{sex},
            </if>
            <if test="age!=null">
                #{age},
            </if>
            <if test="address!=null and address!=''">
                #{address},
            </if>
        </trim>
    </insert>
<!--    delete-->
    <delete id="deleteUser" parameterType="int">
        DELETE FROM user WHERE id=#{id}
    </delete>
<!--getdata-->
    <select id="getUserById" parameterType="int" resultType="com.by.pojo.User">
        SELECT * FROM user WHERE id=#{id}
    </select>
</mapper>

测试结果

修改数据

在servlet包下新建UpdateUserServlet

public class UpdateUserServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        doPost(req, resp);
    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        //1、接收参数
        Integer id = Integer.valueOf(req.getParameter("id"));
        String username = req.getParameter("username");
        String password = req.getParameter("password");
        String sex = req.getParameter("sex");
        Integer age = Integer.valueOf(req.getParameter("age"));
        String address = req.getParameter("address");
        User user = new User(id, username, password, sex, age, address);

        //2、调用service，修改user
        UserService userService = new UserServiceImpl(this);
        userService.updateUserById(user);

        //3、重定向到SelectUserServlet
        resp.sendRedirect("selectUserServlet");
    }
}

web.xml

<!--    UpdateUserServlet-->
    <servlet>
        <servlet-name>updateUserById</servlet-name>
        <servlet-class>com.by.servlet.UpdateUserServlet</servlet-class>
    </servlet>
    <servlet-mapping>
        <servlet-name>updateUserById</servlet-name>
        <url-pattern>/updateUserById</url-pattern>
    </servlet-mapping>

以下内容可在servlet类中Alt+Enter快捷键出来(先把Servlet类写完整)

在service包下的UserService接口

public interface UserService {

    User login(String username, String password);

    List<User> selectUser();

    void addUser(User user);

    void deleteUser(Integer id);

    User getUserById(Integer id);

    void updateUserById(User user);
}

UserServiceImpl类

public class UserServiceImpl implements UserService {
    private SqlSession sqlSession;
    private UserMapper userMapper;
    //加载UserMapper类
    public UserServiceImpl(HttpServlet httpServlet) {
        ServletContext servletContext = httpServlet.getServletContext();
        sqlSession = (SqlSession) servletContext.getAttribute("sqlSession");
        userMapper = sqlSession.getMapper(UserMapper.class);
    }

    @Override
    public User login(String username, String password) {
        //调用dao
        return userMapper.login(username,password);
    }

    @Override
    public List<User> selectUser() {
        return userMapper.selectUser();
    }

    @Override
    public void addUser(User user) {
        userMapper.addUser(user);
        sqlSession.commit();
    }

    @Override
    public void deleteUser(Integer id) {
        userMapper.deleteUser(id);
        sqlSession.commit();
    }

    @Override
    public User getUserById(Integer id) {
        return userMapper.getUserById(id);
    }

    @Override
    public void updateUserById(User user) {
        userMapper.updateUserById(user);
        sqlSession.commit();
    }
}

mapper包下的UserMapper接口

public interface UserMapper {
    User login(@Param("username") String username, @Param("password") String password);

    List<User> selectUser();

    void addUser(User user);

    void deleteUser(Integer id);

    User getUserById(Integer id);

    void updateUserById(User user);
}

mapper包下的UserMapper.xml接口

<?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.by.mapper.UserMapper">
    <select id="login" resultType="com.by.pojo.User">
        SELECT * FROM user WHERE username=#{username} AND password=#{password}
    </select>
    <select id="selectUser" resultType="com.by.pojo.User">
        SELECT * FROM user
    </select>
<!--   insert-->
    <insert id="addUser" parameterType="com.by.pojo.User">
        INSERT INTO user
        <trim prefix="(" suffix=")" suffixOverrides=",">
            <if test="username!=null and username!=''">
                username,
            </if>
            <if test="password!=null and password!=''">
                password,
            </if>
            <if test="sex!=null and sex!=''">
                sex,
            </if>
            <if test="age!=null">
                age,
            </if>
            <if test="address!=null and address!=''">
                address,
            </if>
        </trim>
        VALUES
        <trim prefix="(" suffix=")" suffixOverrides=",">
            <if test="username!=null and username!=''">
                #{username},
            </if>
            <if test="password!=null and password!=''">
                #{password},
            </if>
            <if test="sex!=null and sex!=''">
                #{sex},
            </if>
            <if test="age!=null">
                #{age},
            </if>
            <if test="address!=null and address!=''">
                #{address},
            </if>
        </trim>
    </insert>
<!--    delete-->
    <delete id="deleteUser" parameterType="int">
        DELETE FROM user WHERE id=#{id}
    </delete>
<!--getdata-->
    <select id="getUserById" parameterType="int" resultType="com.by.pojo.User">
        SELECT * FROM user WHERE id=#{id}
    </select>
<!--    updata-->
    <update id="updateUserById" parameterType="com.by.pojo.User">
        UPDATE user
        <set>
            <if test="username!=null and username!=''">
                username=#{username},
            </if>
            <if test="password!=null and password!=''">
                password=#{password},
            </if>
            <if test="sex!=null and sex!=''">
                sex=#{sex},
            </if>
            <if test="age!=null">
                age=#{age},
            </if>
            <if test="address!=null and address!=''">
                address=#{address},
            </if>
        </set>
        WHERE id=#{id}
    </update>
</mapper>

测试结果

1

2

七 最终项目结构

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