1.搭建简单的springBoot项目

1.创建maven项目

 

 

2.引入依赖(父工程坐标+web启动器+...)

<?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>cn.itcast.springboot</groupId>
    <artifactId>hello-springboot</artifactId>
    <version>1.0-SNAPSHOT</version>
    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.3.8.RELEASE</version>
    </parent>
    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
        <!--mybatis -->
        <dependency>
            <groupId>org.mybatis.spring.boot</groupId>
            <artifactId>mybatis-spring-boot-starter</artifactId>
            <version>1.3.2</version>
        </dependency>
        <!-- mysql 数据库驱动-->
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
        </dependency>
    </dependencies>
</project>

　　

3.配置application.yaml

spring:
  datasource:
    driver-class-name: com.mysql.jdbc.Driver
    url: jdbc:mysql://localhost:3306/test?serverTimezone=UTC
    username: root
    password: 1234

logging:
  level:
    cn.itcast: debug
    org.springframework: debug

server:
  port: 80
mybatis:
  configuration:
    log-impl: org.apache.ibatis.logging.stdout.StdOutImpl
  # mybatis
  type-aliases-package: com.it.springBoot.pojo
  # mapper.xml文件位置,如果没有映射文件，请注释掉
  mapper-locations: classpath:mappers/*.xml

　4.创建启动类SpringBootStartApplication

 

 

5.resource

package com.it.springBoot.resource;


import com.it.springBoot.pojo.UserDto;
import com.it.springBoot.service.impl.UserService;
import org.apache.catalina.User;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RestController;

import java.util.List;


@RestController
public class UserResource {

    @Autowired
    private UserService userService;
//    http://localhost//getUserName/7654
    @GetMapping("/getUserName/{empno}")
    public String queryEnameByEmpno(@PathVariable String  empno) {
        String user = userService.queryEnameByEmpno(empno);
        return user;
    }

//    http://localhost//getUserInfo
    @GetMapping("/getUserInfo")
    public List<UserDto> getUserInfo() {
        List<UserDto> users = userService.getUserInfo();
        return users;
    }
}

　　6.service接口

package com.it.springBoot.service.impl;

import com.it.springBoot.pojo.UserDto;

import java.util.List;

public interface UserService {
    String queryEnameByEmpno(String empno);

    List<UserDto> getUserInfo();
}

　　7.service接口实现类

package com.it.springBoot.service.impl;

import com.it.springBoot.mapper.UserMapper;
import com.it.springBoot.pojo.UserDto;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;

import java.util.List;

@Service
public class UserServiceImpl  implements UserService {

    @Autowired
    private UserMapper userMapper;

    @Override
    public String queryEnameByEmpno(String empno) {
        userMapper.queryEnameByEmpno(empno);
        return  userMapper.queryEnameByEmpno(empno);
    }

    @Override
    public List<UserDto> getUserInfo() {
        List<UserDto> users= userMapper.getUserInfo();
        return users;
    }
}

　　8.mapper类

package com.it.springBoot.mapper;

import com.it.springBoot.pojo.UserDto;
import org.apache.ibatis.annotations.Param;

import java.util.List;

public interface UserMapper {

    String queryEnameByEmpno(@Param("empno")String empno);

    List<UserDto>  getUserInfo();
}

　　

9.xxMapper.xml

<?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.it.springBoot.mapper.UserMapper">
    <select id="queryEnameByEmpno" parameterType="java.lang.String" resultType="java.lang.String">
       select  ename from emp where empno=#{empno}
    </select>

    <select id="getUserInfo" parameterType="java.lang.String" resultType="com.it.springBoot.pojo.UserDto">
       select  * from  emp limit 2;
    </select>
</mapper>

　　10：注意

a,service实现类上加上注解,注入到Spring容器中

@Service
public class UserServiceImpl  implements UserService {

  xxx
}

　　b,启动类加上mapper包扫描注解

@MapperScan("com.it.springBoot.mapper")//mapper包扫描

　　c.yml文件中加上mapper文件映射

mapper-locations: classpath:mappers/*.xml