Spring Boot面试题

基础概念

Q1: Spring Boot的核心特性有哪些？

public class SpringBootBasicDemo {// 1. 自动配置@SpringBootApplicationpublic class DemoApplication {public static void main(String[] args) {SpringApplication.run(DemoApplication.class, args);}// 自定义配置@Configurationpublic class CustomConfig {@Bean@ConditionalOnMissingBeanpublic DataSource dataSource() {return DataSourceBuilder.create().url("jdbc:mysql://localhost:3306/demo").username("root").password("password").build();}}}// 2. 外部配置@Configuration@ConfigurationProperties(prefix = "app")public class AppProperties {private String name;private String description;private Map<String, String> additionalHeaders = new HashMap<>();// getters and setters}
}

Q2: Spring Boot的启动流程是怎样的？

public class SpringBootStartupDemo {// 1. 启动流程public class StartupExample {public void startupDemo() {@SpringBootApplicationpublic class Application {public static void main(String[] args) {SpringApplication app = new SpringApplication(Application.class);app.setBannerMode(Banner.Mode.OFF);app.setWebApplicationType(WebApplicationType.SERVLET);app.addListeners(new ApplicationListener<ApplicationEvent>() {@Overridepublic void onApplicationEvent(ApplicationEvent event) {if (event instanceof ApplicationStartedEvent) {// 应用启动后的处理}}});app.run(args);}}}}// 2. 自定义启动器public class CustomStarterExample {public void starterDemo() {// 自动配置类@Configuration@ConditionalOnClass(CustomService.class)@EnableConfigurationProperties(CustomProperties.class)public class CustomAutoConfiguration {@Autowiredprivate CustomProperties properties;@Bean@ConditionalOnMissingBeanpublic CustomService customService() {return new CustomService(properties);}}// 配置属性@ConfigurationProperties(prefix = "custom")public class CustomProperties {private String property;private boolean enabled = true;// getters and setters}}}
}

高级特性

Q3: Spring Boot的自动配置原理是怎样的？

public class AutoConfigurationDemo {// 1. 条件注解public class ConditionalExample {public void conditionalDemo() {@Configuration@ConditionalOnClass(DataSource.class)public class DatabaseConfiguration {@Bean@ConditionalOnMissingBeanpublic DataSource dataSource() {// 数据源配置}@Bean@ConditionalOnProperty(prefix = "spring.jpa",name = "enabled",havingValue = "true",matchIfMissing = true)public JpaTransactionManager transactionManager() {// 事务管理器配置}}}}// 2. 自动配置实现public class AutoConfigImplementationExample {public void autoConfigDemo() {@Configuration@EnableAutoConfiguration@ComponentScanpublic class AppConfig {@Beanpublic BeanFactoryPostProcessor beanFactoryPostProcessor() {return new BeanFactoryPostProcessor() {@Overridepublic void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) throws BeansException {// 处理bean工厂}};}}}}
}

Q4: Spring Boot的监控和运维是怎样的？

public class MonitoringDemo {// 1. Actuator配置public class ActuatorExample {public void actuatorDemo() {@Configurationpublic class ActuatorConfig {@Beanpublic HealthIndicator customHealthIndicator() {return new HealthIndicator() {@Overridepublic Health health() {return Health.up().withDetail("app", "Healthy").withDetail("error", "None").build();}};}@Beanpublic EndpointWebExtension metricsEndpointWebExtension(MetricsEndpoint metricsEndpoint) {return new EndpointWebExtension() {@ReadOperationpublic WebEndpointResponse<Map> getMetrics() {return new WebEndpointResponse<>(metricsEndpoint.metric("jvm.memory.used", null).getMeasurements().stream().collect(Collectors.toMap(Measurement::getStatistic,Measurement::getValue)),200);}};}}}}// 2. 自定义监控指标public class CustomMetricsExample {public void metricsDemo() {@Componentpublic class CustomMetricsExporter {private final MeterRegistry registry;public CustomMetricsExporter(MeterRegistry registry) {this.registry = registry;}public void recordCustomMetric(String name, double value) {registry.gauge(name, value);}public void incrementCounter(String name) {registry.counter(name).increment();}public void recordTimer(String name, long timeInMs) {registry.timer(name).record(Duration.ofMillis(timeInMs));}}}}
}

Q5: Spring Boot的性能优化有哪些？

public class PerformanceOptimizationDemo {// 1. JVM优化public class JVMOptimizationExample {public void jvmOptDemo() {// JVM参数配置public class JVMConfig {public void configureJVM() {// 设置JVM参数System.setProperty("spring.jmx.enabled", "false");System.setProperty("spring.config.location", "classpath:/application.yml");System.setProperty("server.tomcat.max-threads", "200");System.setProperty("server.tomcat.min-spare-threads", "10");}}}}// 2. 数据库优化public class DatabaseOptimizationExample {public void dbOptDemo() {@Configurationpublic class DatabaseConfig {@Beanpublic DataSource dataSource() {HikariConfig config = new HikariConfig();config.setMaximumPoolSize(10);config.setMinimumIdle(5);config.setIdleTimeout(300000);config.setConnectionTimeout(20000);config.setMaxLifetime(1200000);return new HikariDataSource(config);}@Beanpublic JdbcTemplate jdbcTemplate(DataSource dataSource) {JdbcTemplate template = new JdbcTemplate(dataSource);template.setFetchSize(100);template.setMaxRows(500);return template;}}}}// 3. 缓存优化public class CacheOptimizationExample {public void cacheOptDemo() {@Configuration@EnableCachingpublic class CacheConfig {@Beanpublic CacheManager cacheManager() {CaffeineCacheManager cacheManager = new CaffeineCacheManager("users");cacheManager.setCaffeine(Caffeine.newBuilder().expireAfterWrite(60, TimeUnit.MINUTES).maximumSize(100));return cacheManager;}}@Servicepublic class UserService {@Cacheable(value = "users", key = "#id")public User getUser(Long id) {// 从数据库获取用户return userRepository.findById(id).orElse(null);}@CacheEvict(value = "users", key = "#user.id")public void updateUser(User user) {// 更新用户userRepository.save(user);}}}}
}