Spring Boot面试题
基础概念
Q1: Spring Boot的核心特性有哪些？
java
public class SpringBootBasicDemo {
// 1. 自动配置
@SpringBootApplication
public class DemoApplication {
public static void main(String[] args) {
SpringApplication.run(DemoApplication.class, args);
}
// 自定义配置
@Configuration
public class CustomConfig {
@Bean
@ConditionalOnMissingBean
public 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？
java
public class SpringBootStartupDemo {
// 1. 启动流程
public class StartupExample {
public void startupDemo() {
@SpringBootApplication
public 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>() {
@Override
public 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 {
@Autowired
private CustomProperties properties;
@Bean
@ConditionalOnMissingBean
public 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？
java
public class AutoConfigurationDemo {
// 1. 条件注解
public class ConditionalExample {
public void conditionalDemo() {
@Configuration
@ConditionalOnClass(DataSource.class)
public class DatabaseConfiguration {
@Bean
@ConditionalOnMissingBean
public 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
@ComponentScan
public class AppConfig {
@Bean
public BeanFactoryPostProcessor beanFactoryPostProcessor() {
return new BeanFactoryPostProcessor() {
@Override
public void postProcessBeanFactory(
ConfigurableListableBeanFactory beanFactory)
throws BeansException {
// 处理bean工厂
}
};
}
}
}
}
}Q4: Spring Boot的监控和运维是怎样的？
java
public class MonitoringDemo {
// 1. Actuator配置
public class ActuatorExample {
public void actuatorDemo() {
@Configuration
public class ActuatorConfig {
@Bean
public HealthIndicator customHealthIndicator() {
return new HealthIndicator() {
@Override
public Health health() {
return Health.up()
.withDetail("app", "Healthy")
.withDetail("error", "None")
.build();
}
};
}
@Bean
public EndpointWebExtension metricsEndpointWebExtension(
MetricsEndpoint metricsEndpoint) {
return new EndpointWebExtension() {
@ReadOperation
public 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() {
@Component
public 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？
java
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() {
@Configuration
public class DatabaseConfig {
@Bean
public 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);
}
@Bean
public 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
@EnableCaching
public class CacheConfig {
@Bean
public CacheManager cacheManager() {
CaffeineCacheManager cacheManager =
new CaffeineCacheManager("users");
cacheManager.setCaffeine(Caffeine.newBuilder()
.expireAfterWrite(60, TimeUnit.MINUTES)
.maximumSize(100));
return cacheManager;
}
}
@Service
public 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);
}
}
}
}
}面试关键点
- 理解Spring Boot的核心特性
- 掌握启动流程和原理
- 熟悉自动配置机制
- 了解监控和运维
- 掌握性能优化方法
- 理解配置管理
- 注意安全实践
- 关注最佳实践