SpringBoot入门（一）

<!--  父工程  -->
<parent>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-parent</artifactId>
    <version>2.1.5.RELEASE</version>
</parent>

<!--  设置JDK版本  -->
<properties>
    <java.version>1.8</java.version>
</properties>

<!--  添加依赖  -->
<dependencies>
    <!--  场景启动器  -->
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-web</artifactId>
    </dependency>
</dependencies>

@SpringBootApplication
public class Application {

    public static void main(String[] args) {

        //SpringBoot启动
        SpringApplication.run(Application.class,args);
    }
}

@RestController
public class HelloController {

    //请求映射
    @RequestMapping(value = "hello",method = RequestMethod.GET)
    public String hello(){
        return "Hello Worlddddd";
    }
}

jdbc:
  driverclassName: com.mysql.jdbc.Driver
  url: jdbc:mysql://localhost:3306/test?serverTimezone=UTC
  username: root
  password: howl

<!--  注解解析器  -->
<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-configuration-processor</artifactId>
    <optional>true</optional>
</dependency>

/*
 * @ConfigurationProperties把配置文件的属性注入该类中
 */
@Component
@ConfigurationProperties(prefix = "jdbc")
public class JDBC {
    private String driverclassName;
    private String url;
    private String username;
    private String password;

    //各种Getters和Setters
}

//将配置文件的属性注入到该对象中，只有这个注解是生效的，需要配合@EnableConfigurationProperties注解，或加入@Component注解
@ConfigurationProperties(prefix = "jdbc")

//属性注入
@value("${name}")

//使对应的配置文件生效加入到Bean容器
@EnableConfigurationProperties(JDBCProperties.class)

//声明一个类为配置类，代替xml文件，一般配合@Bean注解
@Configuration
//声明在方法上，将返回值加入Bean容器，代替<bean>标签
@Bean

//------------推荐使用上面来指定配置文件,在主目录下创一个config包-------------

//指定外部属性文件,这时还没生效,需要配合下面的注解
@PropertySource(value = {"classpath:other.properties"})
//加载多个配置文件,放在主程序类上
@ImportResourcec(locations = {"classpath:other.yml"})

# 在application.yml主配置文件中添加下面配置
spring:
  profiles:
    active: dev

//请求映射
@RequestMapping(value = "hello",method = RequestMethod.GET)
public String hello(){
    return jdbc.getUsername();
}