# 只用Servlet搞定登录与注册

# 基础项目环境的搭建

使用maven的web项目结构创建项目,并添加核心的java目录

引入插件

pom.xml

<dependencies>
        <!--apache io工具类        -->
        <dependency>
            <groupId>commons-io</groupId>
            <artifactId>commons-io</artifactId>
            <version>2.11.0</version>
        </dependency>

        <dependency>
            <groupId>javax.servlet</groupId>
            <artifactId>javax.servlet-api</artifactId>
            <version>4.0.1</version>
            <scope>provided</scope>
        </dependency>

        <dependency>
            <groupId>org.mybatis</groupId>
            <artifactId>mybatis</artifactId>
            <version>3.5.11</version>
        </dependency>

        <dependency>
            <groupId>org.mariadb.jdbc</groupId>
            <artifactId>mariadb-java-client</artifactId>
            <version>3.0.7</version>
        </dependency>

    </dependencies>
    <build>
        <finalName>servlet</finalName>
        <plugins>
            <plugin>
                <groupId>org.apache.tomcat.maven</groupId>
                <artifactId>tomcat7-maven-plugin</artifactId>
                <version>2.2</version>
            </plugin>
        </plugins>
</build>

# Mybaits配置

创建数据表

编写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>

    <typeAliases>
        <!-- 类型别名 -->
        <package name="top.brightzm.pojo"/>
    </typeAliases>

    <environments default="development">
        <environment id="development">
            <transactionManager type="JDBC"/>
            <dataSource type="POOLED">
                <!--数据库连接信息 -->
                <property name="driver" value="org.mariadb.jdbc.Driver"/>
                <property name="url" value="jdbc:mariadb://127.0.0.1:3306/mybatis"/>
                <property name="username" value="root"/>
                <property name="password" value="ROOT"/>
            </dataSource>
        </environment>
    </environments>
    <!--扫描mapper -->
    <mappers>
        <package name="top.brightzm.mapper"/>
    </mappers>

</configuration>

编写sql映射文件 UserMapper.xml

注意路径 top/brightzm/mapper

<?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="top.brightzm.mapper.UserMapper">

    <!--查询用户 -->
    <select id="select" resultType="top.brightzm.pojo.User">
        SELECT * FROM tb_user2
        WHERE username = #{username}
        AND password = #{password}
    </select>
    <select id="selectByName" resultType="User">
        SELECT *
        FROM tb_user2
        WHERE username = #{username};
    </select>

    <!-- 创建用户 -->
    <insert id="add">
        INSERT INTO tb_user2(username, password)
        VALUES (#{username}, #{password})
    </insert>

</mapper>

编写pojo类 User.java

public class User {
    private Integer id;
    private String username;
    private String password;

    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;
    }

    @Override
    public String toString() {
        return "User{" +
                "id=" + id +
                ", username='" + username + '\'' +
                ", password='" + password + '\'' +
                '}';
    }
}

编写mapper接口 UserMapper.java

注意路径

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

    User selectByName(@Param("username") String username);

    void add(User user);

}

# 编写servlet核心代码

静态文件编写

form表单 action指向servlet的url

编写SqlSessionFactory工具类

public class SqlSessionFactoryUtils {
    // SqlSessionFactory对象获取

    private static SqlSessionFactory sqlSessionFactory;

    static {
        try {
            String resources = "mybatis-config.xml";
            InputStream inputStream = Resources.getResourceAsStream(resources);
            sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
        } catch (IOException e){
            e.printStackTrace();
        }
    }


    public static SqlSessionFactory getSqlSessionFactory(){
        return sqlSessionFactory;
    }

}

@WebServlet("/login")
public class login extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // 获取用户名和密码
        String username = request.getParameter("username");
        String password = request.getParameter("password");

        // 调用Mybatis完成查询
        // 获取sqlSessionFactory对象 和sqlSession对象
        SqlSessionFactory sqlSessionFactory = SqlSessionFactoryUtils.getSqlSessionFactory();

        SqlSession sqlSession = sqlSessionFactory.openSession();

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

        User user = mapper.select(username, password);

        sqlSession.close();

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

    }

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

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

    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        // 注册的实现
        // 获取用户名和密码
        String newName = req.getParameter("username");
        String newPassword = req.getParameter("password");

        User newUser = new User();
        newUser.setUsername(newName);
        newUser.setPassword(newPassword);

        // 使用mybatis添加用户
        // 获取sqlsession
        SqlSessionFactory sqlSessionFactory = SqlSessionFactoryUtils.getSqlSessionFactory();
        
        SqlSession sqlSession = sqlSessionFactory.openSession();

        // 获取mapper
        UserMapper mapper = sqlSession.getMapper(UserMapper.class);
        // 判断用户名是否重复
        User user = mapper.selectByName(newName);
        boolean result = user == null;

        // 添加用户并返回信息
        resp.setContentType("text/html;charset=utf-8");
        PrintWriter writer = resp.getWriter();
        if (result){
            mapper.add(newUser);

            // 提交事务
            sqlSession.commit();
            sqlSession.close();
            
            writer.write("注册成功");
        }else {
            writer.write("用户名重复");
        }
        
    }

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

运行项目完成

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