SpringBoot-Day1

1.Springboot入门

创建Maven工程
导入spring-boot-stater-web起步依赖
编写Controller
提供启动类

2.yml配置信息书写与获取

书写

# 发件人信息
email:user: 172349823457@qq.comcode: sajdajlwhjfgfkllwhost: smtp.qq.comauth: true

# 学生爱好
hobbies:- 打篮球- 踢足球- 打游戏

获取

@Value("${mail.user}")

更便利的方法：

# 要求实体类的成员变量名与配置文件中的键名保持一致
@ConfigurationProperties(prefix = "email")

3.bean扫描

// 启动类
@SpringBootApplication
public class SpringBootQuickstartApplication{public static void main(String[] args){SpringApplication.run(SpringbootQuickstartApplication.class,args);}
}


//其中@SpringBootApplication包含了以下内容
@SpringBiitConfiguration
@EnableAutoConfiguration
@ComponentScan
public @interface SpringBootApplication{
}

//也可以通过@ComponentScan(basePackages="com.example")来扫描包

4.bean注册

如果要注册的bean对象来自第三方，是无法用@Component及其衍生注解声明bean 的

//通过@Bean

//直接在启动类中，编写
//注入Country对象
@Bean //将方法返回值交给IOC容器管理，成为IOC容器的bean对象
public Country country(){return new Country();
}





//通过@Import

//1.导入配置类
@Import(CommonConfig.class)
@SpringBootApplication
public class SpringBootApplication{
}

//2.导入ImportSelector接口实现类
public class CommonImportSelector Implements ImportSelector{@Overridepublic String[] selectImports(AnnotationMetadata importingClassMetadata){return new String[]("com.example.config.CommonConfig");}
}


public class CommonImportSelector implements ImportSelector {@Ovrridepublic String[] selectImports(AnnotationMetadata importingClassMetadata){// 读取配置文件的内容List<String> imports = new ArrayList<>();InputStream is = CommonImportSelector.class.getClassLoader().getResourceAsStream("common.imports");BufferedReader br = new BufferedReader(new InputStreamReader(is));String line = null;try {while((line = br.readLine())!=null){imports.add(line);}} catch (IOException e) {throw new RuntimeException(e);} finally {if (br!=null){try {br.close();}catch (IOException e) {throw new RuntimeException(e);}}}return imports.toArray(new String[0]);}
}

5.注册条件

SpringBoot提供了设置注册生效条件的注解@Conditional

//若配置文件中配置了指定的信息，则注入，否则不注入
@ConditionalOnProperty(prefix = "country",name = {"name","system"})
@Bean
public Country country(@Value("${country.name}") String name,@Value("${country.system}") String system){Country country = new Country();country.setName(name);country.setSystem(system);return country;
}

//若IOC容器中不存在Country，则注入Province，否则不注入
@Bean
@ConditionalOnMissingBean(Country.class)
public Province province(){return new Province();
}

//若当前环境中存在DispatcherServlet类，则注入Province，否则不注入
//若当前引入了web起步依赖，则环境中有DispatcherServlet，否则没有
@Bean
@ConditionalOnClass(name = "org.springframework.web.servlet.DispatcherServlet")
public Province province(){return new Province();
}

6.自动配置原理

遵循约定大于配置的原则，在boot程序启动后，起步依赖中的一些bean对象会自动注入到ioc容器中

7.自定义starter

@AutoConfiguration //表示当前类是一个自动配置类
public class MyBatisAutoConfig {//SqlSessionFactoryBean@Beanpublic SqlSessionFactoryBean sqlSessionFactoryBean(DataSource dataSource){SqlSessionFactoryBean sqlSessionFactoryBean();sqlSessionFactoryBean.setDataSource(dataSource);return sqlSessionFactoryBean;}//MapperScannerConfigure@Beanpublic MapperScannerConfigurer mapperScannerConfigurer(BeanFactory beanFactory){MapperScannerConfigurer mapperScannerConfigurer = new MapperScannerConfigurer();//扫描的包：启动类所在的包及其子包List<String> packages = AutoConfigurationPackages.get(beanFactory);String p = packages.get(0);mapperScannerConfigurer.setBasePackage(p);//扫描的注解mapperScannerConfigurer.setAnnotationClass(Mapper.class);return mapperScannerConfigurer;}
}

步骤