用户登录

流程步骤

项目文件结构 

环境准备 

数据库建表语句如下 

-- 创建用户表
CREATE TABLE tb_user(id int primary key auto_increment,username varchar(20) unique,password varchar(32)
);-- 添加数据
INSERT INTO tb_user(username,password) values('zhangsan','123'),('lisi','234');SELECT * FROM tb_user;

 在pojo包下创建数据库属性的实体类如下

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

坐标导入

这里有mybatis驱动和mysql驱动程序的依赖，mysql驱动的版本根据自己电脑上mysql版本决定

 org.mybatismybatis3.5.5mysqlmysql-connector-java8.0.31

 创建mybatis核心配置文件

mysql8.0以上版本要加cj

xml里面&是特殊字符要转义使用&

创建mapper包下的接口映射以及resources文件下的对应目录XML文件

mapper映射接口实现

在mybatis接口方法里面有多个参数的话要加上@Param注解做映射将sql语句里面的#{}参数占位符内的名称和@Param()内的参数相对应

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

html页面设置

定义如下的表单，action里面的路径要加上虚拟目录

    
LOGIN IN
Username:
Password:
   没有账号？点击注册

LoginServlet配置

第一步

接收登录界面传来的数据，这里使用Parameter通过键来获取值

String username = request.getParameter("username");String password = request.getParameter("password");

第二步

调用mybatis

获取sqlsessionFactory对象

(通过mybatis配置文件的输入流构建一个sqlsessionFactory对象)

有点像对着施工图纸完成一座工厂，一座专门用于产出sqlsession的工厂

String resource = "mybatis-config.xml";InputStream inputStream = Resources.getResourceAsStream(resource);SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);

获取sqlsession对象

像是从工厂里面获取一个产品

SqlSession sqlSession = sqlSessionFactory.openSession();

获取Mapper对象

UserMapper userMapper = sqlSession.getMapper(UserMapper.class);

调用方法

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

释放资源

sqlSession.close();

汇总代码： 

@Overrideprotected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {//1. 接收用户名和密码String username = request.getParameter("username");String password = request.getParameter("password");//2. 调用MyBatis完成查询//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MapperUserMapper 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();//获取字符输出流，并设置content typeresponse.setContentType("text/html;charset=utf-8");PrintWriter writer = response.getWriter();//3. 判断user释放为nullif(user != null){// 登陆成功writer.write("登陆成功");}else {// 登陆失败writer.write("登陆失败");}}

第三步

判断user是否为null

根据查询的不同结果使用response返回不同的响应数据，这里返回的始终所以需要设置字符集为utf-8

 //获取字符输出流，并设置content typeresponse.setContentType("text/html;charset=utf-8");PrintWriter writer = response.getWriter();//3. 判断user释放为nullif(user != null){// 登陆成功writer.write("登陆成功");}else {// 登陆失败writer.write("登陆失败");}

这里成功使用数据库里面的账号登陆成功输出如下

失败登陆也有如下

以上就是用户登录的实现 

用户注册

注册流程

 定义mapper映射sql语句

在上面mapper接口实现类里面有了

创建一个新的RegisterServlet

和上面的流程机器相似，这里放全代码，以后有机会在来看两眼

@Overrideprotected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {//1. 接收用户数据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);*/SqlSessionFactory sqlSessionFactory = SqlSessionFactoryUtils.getSqlSessionFactory();//2.2 获取SqlSession对象SqlSession sqlSession = sqlSessionFactory.openSession();//2.3 获取MapperUserMapper userMapper = sqlSession.getMapper(UserMapper.class);//2.4 调用方法User u = userMapper.selectByUsername(username);//3. 判断用户对象释放为nullif( u == null){// 用户名不存在，添加用户userMapper.add(user);// 提交事务sqlSession.commit();// 释放资源sqlSession.close();}else {// 用户名存在，给出提示信息response.setContentType("text/html;charset=utf-8");response.getWriter().write("用户名已存在");}}

 成功输出如下 

 sqlsessionfactory工具类使用

在LoginServlet和RegisterServlet创建了两次sqlsessionfactory对象，代码重复量极大。

sqlsessionfactory对象都绑定了一个连接池，多个工厂有多个连接池，资源消耗极大。

所以要优化sqlsessionfactory的创建代码

创建工具类

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;}
}

这里不把sqlsession对象的创建也放进去是因为

 最后Servlet里面创建工厂时直接调用方法返回值就可以了

 //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();