1、如何在 Spring Boot 启动的时候运行一些特定的代码?
可以实现接口 ApplicationRunner 或者 CommandLineRunner,这两个接口实现方式一样,它们都只提供了一个 run 方法
@Component
@Order(1)
public class Mytest implements ApplicationRunner {
@Override
public void run(ApplicationArguments args) throws Exception {
System.out.println("启动测试");
}
}
@Component
@Order(1)
public class Mytest implements CommandLineRunner {
@Override
public void run(String... args) throws Exception {
System.out.println("启动测试");
}
}
2、Spring Boot 有哪几种读取配置的方式?
Spring Boot 可以通过 @PropertySource,@Value,@Environment, @ConfigurationProperties 来绑定变量
@PropertySource(value={"classpath:/user.properties"})
public class Configs {
@Value("${u.name}")
private String userName;
@Value("${u.age}")
private Integer age;
}
mail.host=localhost
mail.port=25
mail.smtp.auth=false
mail.smtp.starttls-enable=false
mail.from=me@localhost
mail.username=duan
mail.password=duan123456
import org.springframework.boot.context.properties.ConfigurationProperties;
@ConfigurationProperties(locations = "classpath:mail.properties", ignoreUnknownFields = false, prefix = "mail")
public class MailProperties {
private String host;
private int port;
private String from;
private String username;
private String password;
private Smtp smtp;
}
3、springBoot自动化配置的原理
启动类的@SpringBootApplication 是一个复合注解
@Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Inherited
@SpringBootConfiguration
@EnableAutoConfiguration
@ComponentScan(excludeFilters = {
@Filter(type = FilterType.CUSTOM, classes = TypeExcludeFilter.class),
@Filter(type = FilterType.CUSTOM,
classes = AutoConfigurationExcludeFilter.class) })
public @interface SpringBootApplication {
@SpringBootConfiguration继承自@Configuration,二者功能也一致,标注当前类是配置类,
并会将当前类内声明的一个或多个以@Bean注解标记的方法的实例纳入到spring容器中,并且实例名就是方法名。
@EnableAutoConfiguration里通过@Import导入了EnableAutoConfigurationImportSelector
会查询META-INF/spring.factories
文件中包含的JAR
文件。
RedisAutoConfiguration
@Configuration
@ConditionalOnClass(RedisOperations.class)
@EnableConfigurationProperties(RedisProperties.class)
@Import({ LettuceConnectionConfiguration.class, JedisConnectionConfiguration.class })
public class RedisAutoConfiguration {
@Bean
@ConditionalOnMissingBean(name = "redisTemplate")
public RedisTemplate<Object, Object> redisTemplate(
RedisConnectionFactory redisConnectionFactory) throws UnknownHostException {
RedisTemplate<Object, Object> template = new RedisTemplate<>();
template.setConnectionFactory(redisConnectionFactory);
return template;
}
@Bean
@ConditionalOnMissingBean
public StringRedisTemplate stringRedisTemplate(
RedisConnectionFactory redisConnectionFactory) throws UnknownHostException {
StringRedisTemplate template = new StringRedisTemplate();
template.setConnectionFactory(redisConnectionFactory);
return template;
}
}