1.主程序
package com.example.demo;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

/**

• @Description:
• @author: YuanTong-ZXY
• @Date: 2019/2/19 15:15
  */
  @SpringBootApplication
  public class DemoApplication {
  public static void main(String[] args) {
  SpringApplication.run(DemoApplication.class,args);
  }
  }

2.controller层
package com.example.demo.controller;

import com.example.demo.service.UserServiceImpl;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

import javax.annotation.Resource;

/**

• @Description:

• @author: YuanTong-ZXY

• @Date: 2019/2/19 15:09
  */
  @RestController
  @RequestMapping("/testboot")
  public class TestBootController {
  @Resource
  private UserServiceImpl userService;

  @RequestMapping("getuser")
  public Integer getUser() {
  Integer userById = userService.getUserById();
  return userById;
  }
  }
  3、service层
  package com.example.demo.service;
  /**

• @Description:

• @author: YuanTong-ZXY

• @Date: 2019/2/19 15:59
  /
  import com.example.demo.mapper.UserDao;
  import org.springframework.stereotype.Service;
  import javax.annotation.Resource;
  @Service("userService")
  public class UserServiceImpl{
  @Resource
  private UserDao userDao;
  public Integer getUserById() {
  return userDao.selectCount();
  }
  }
  4.mapper
  package com.example.demo.mapper;
  /*

• @Description:

• @author: YuanTong-ZXY

• @Date: 2019/2/19 15:54
  /
  import org.apache.ibatis.annotations.Mapper;
  @Mapper
  public interface UserDao {
  Integer selectCount();
  }
  5.mapper.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.example.demo.mapper.UserDao" >
  <select id="selectCount" resultType="java.lang.Integer" >
  select count() from wx_user
  </select>
  </mapper>

6.application.yml
spring:
profiles:
active: dev
datasource:
url: jdbc:mysql://localhost:3306/saasboard
username: root
password: root
driver-class-name: com.mysql.jdbc.Driver
type: com.alibaba.druid.pool.DruidDataSource
7.pom.xml 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>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-parent</artifactId>
<version>2.1.3.RELEASE</version>
<relativePath/>
</parent>
<groupId>com.example</groupId>
<artifactId>demo</artifactId>
<version>0.0.1-SNAPSHOT</version>
<name>demo</name>
<description>Demo project for Spring Boot</description>
<properties>
<java.version>1.8</java.version>
</properties>
<dependencies>

<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-web</artifactId>
</dependency>
<dependency>
<groupId>org.mybatis.spring.boot</groupId>
<artifactId>mybatis-spring-boot-starter</artifactId>
<version>2.0.0</version>
</dependency>

    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-test</artifactId>
        <scope>test</scope>
    </dependency>
    <!-- https://mvnrepository.com/artifact/mysql/mysql-connector-java -->
    <dependency>
        <groupId>mysql</groupId>
        <artifactId>mysql-connector-java</artifactId>
        <version>5.1.47</version>
    </dependency>
    <dependency>
        <groupId>com.alibaba</groupId>
        <artifactId>druid</artifactId>
        <version>1.0.18</version>
    </dependency>
</dependencies>
<build>
    <plugins>
        <plugin>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-maven-plugin</artifactId>
        </plugin>
    </plugins>
</build>

</project>