spring boot使用自动化配置的方式，使得可以很方便、快捷得构建一个spring web应用。作为学习spring boot 的第一课，还是先基于spring boot构建一个简单的包含控制层、服务层以及数据层的hello world应用。
首先确保本机上安装了mysql,本应用会直接访问mysql自带的数据库world。
mysql下载地址：www.mysql.com/downloads/
world数据库:

系统要求：

（1）Intellij Idea 2016.03
注册码传送门：idea.lanyus.com/
（2）Mysql 5.7
（3）Java 1.7以上

构建指南：

（1）在Intellij Idea里面新建HelloWorld project，并在pom.xml文件中添加mysql-connector以及mybatis依赖。

<dependency>
    <groupId>mysql</groupId>
    <artifactId>mysql-connector-java</artifactId>
    <version>6.0.6</version>
</dependency>
<dependency>
    <groupId>org.mybatis.spring.boot</groupId>
    <artifactId>mybatis-spring-boot-starter</artifactId>
    <version>1.3.0</version>
</dependency>
<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-web</artifactId>
</dependency>

（2）配置/resources/application.properties数据库参数

spring.datasource.url = jdbc:mysql://localhost:3306/world?useUnicode=true&characterEncoding=UTF-8&autocommit=false&autoReconnect=true&useSSL=false&serverTimezone=UTC
spring.datasource.username = root
spring.datasource.password = root
spring.datasource.driverClassName = com.mysql.jdbc.Driver

（3）根据表city的结构创建city对象

public class City {
    private int id;
    private String name;
    private String countryCode;
    private String district;
    private int population;

    public City(int id ,String name, String countryCode,String district,int population) {
        this.id = id;
        this.name = name;
        this.countryCode=countryCode;
        this.district = district;
        this.population = population;
    }
    
    //setter & getter
}

（4）创建控制层CityController

@RestController
public class CityController {
    @Autowired
    private CityService cityService;

    @RequestMapping(value="/city/{cityName}",method= RequestMethod.GET)
    public City gitCity(@PathVariable("cityName") String cityName) {
        return cityService.getCityByCityName(cityName);
    }
}

（5）创建服务层接口CityService 以及实现类CityServiceImpl
CityService:

public interface CityService {
    /**
     * get City by its name
     * @param cityName
     * @return
     */
    City getCityByCityName(String cityName);
}

CityServiceImpl:

@Service
public class CityServiceImpl implements CityService{

    @Autowired
    private CityMapper cityMapper;

    @Override
    public City getCityByCityName(String cityName) {
        return cityMapper.findCityByCityName(cityName);
    }
}

（6）创建CityMapper,用于读写数据库表City

@Mapper
public interface CityMapper {
    @Select("Select * from city where name=#{cityName}")
    City findCityByCityName(String cityName);
}

运行结果

运行主application，在浏览器里面输入http://localhost:8080/city/shanghai，
结果显示如下：

结果显示.png

代码地址：https://github.com/yhguodu/helloworld