使用Spring Boot实现操作数据库的接口的过程

用户从页面前端，也就是我们所说的 view 层进行查询访问，进入到 controller 层找到对应的接口，接 着 controller 进行对 service 层进行业务功能的调用，service 要进入 dao 层查询数据，dao 层调用 mapper.xml 文件生成 sql 语句到数据库中进行查询

2.1、准备数据库user表插入四条数据

2.2、model下创建一个User类

与数据库的字段一一对应

@Getter @Setterpublic class User { private int id; private String username; private String password; private int age;}

2.3、dao下创建一个UserDao接口

@Repository注解修饰哪个类，则表明这个类具有对对象进行CRUD（增删改查）的功能

@Repositorypublic interface UserDao { public User getUserById(@Param('id') int id); public List<User> getUserByAge(@Param('age') int age); public List<User> getUserByName(@Param('username') String username); public int insertUser(@RequestBody User user);}

通过UserMapping.xml配置文件实现UserDao接口

<?xml version='1.0' encoding='UTF-8' ?><!DOCTYPE mapperPUBLIC '-//mybatis.org//DTD Mapper 3.0//EN''http://mybatis.org/dtd/mybatis-3-mapper.dtd'><mapper namespace='com.example.demo.dao.UserDao'> <select resultType='User'>select * from `user` where id=#{id} </select> <select resultType='User'>select * from `user` where age=#{age} </select> <select resultType='User'>select * from `user` where username like concat(’%’,#{username},’%’) </select> <insert parameterType='User'><selectKey keyProperty='id' order='AFTER' resultType='int'> SELECT LAST_INSERT_ID()</selectKey>insert into user (username, password, age)values (#{username,jdbcType=VARCHAR}, #{password,jdbcType=VARCHAR}, #{age,jdbcType=INTEGER}) </insert></mapper>

2.4、Service下创建一个UserService接口

public interface UserService { public User queryUserById(int id); public List<User> queryUserByAge(int age); public List<User> queryUserByName(String username); public int insertUser(User user);}

再创建一个UserServiceImpl实现UserService

@Servicepublic class UserSeviceImpl implements UserService { @Autowired private UserDao userDao; @Override public User queryUserById(int id) {return userDao.getUserById(id); } @Override public List<User> queryUserByAge(int age) {return userDao.getUserByAge(age); } @Override public List<User> queryUserByName(String username) {return userDao.getUserByName(username); } @Override public int insertUser(User user) {return userDao.insertUser(user); }}

2.5、controller下创建一个UserController

@GetMapping是代表该查询接口用的是get方式@RequestMapping(value='/insert',method = RequestMethod.POST)代表该插入接口用post方式

@RestControllerpublic class UserController { @Autowired private UserService userService; @GetMapping('/userid') public User getUserById(@RequestParam('id') int id){return userService.queryUserById(id); } @GetMapping('/username') public List<User> getUserByUsername(@RequestParam('username') String username){return userService.queryUserByName(username); } @RequestMapping(value='/insert',method = RequestMethod.POST) public User insertUser(@RequestBody User user){int x = userService.insertUser(user);return user; }}

2.6、application.yml文件连接数据库

server: port: 8080spring: datasource: driver-class-name: com.mysql.cj.jdbc.Driver url: jdbc:mysql://localhost:3306/testingdev9?useUnicode=true&characterEncoding=utf-8&serverTimezone=Asia/Shanghai username: root password: 123456mybatis: mapper-locations: - classpath:mapper/*.xml - classpath*:com/**/mapper/*.xml type-aliases-package: com.example.demo.model

2.7、启动DemoApplication文件

出现Started DemoApplication代表启动成功了

2.8、使用postman调用接口

如下图根据id查询

如下图插入数据

可以看到数据库多了一条数据

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