Spring 核心知识点

@Service
public class UserService {
    private final UserRepository userRepository;

    // Spring 4.3+ 单构造器可省略 @Autowired
    public UserService(UserRepository userRepository) {
        this.userRepository = userRepository;
    }
}

@Service
public class UserService {
    private UserRepository userRepository;

    @Autowired
    public void setUserRepository(UserRepository userRepository) {
        this.userRepository = userRepository;
    }
}

@Service
public class UserService {
    @Autowired
    private UserRepository userRepository;
}

// 服务层
@Service
public class UserService {
    @Autowired
    private UserRepository userRepository;
}

// 数据访问层
@Repository
public class UserRepository {
}

// 通用组件
@Component
public class EmailSender {
}

@Configuration
@ComponentScan("com.example")
@PropertySource("classpath:application.properties")
public class AppConfig {

    @Bean
    public DataSource dataSource() {
        HikariConfig config = new HikariConfig();
        config.setJdbcUrl("jdbc:mysql://localhost:3306/test");
        config.setUsername("root");
        config.setPassword("secret");
        return new HikariDataSource(config);
    }

    @Bean
    public JdbcTemplate jdbcTemplate(DataSource dataSource) {
        return new JdbcTemplate(dataSource);
    }

    @Bean
    @Primary
    public UserRepository userRepository(JdbcTemplate jdbcTemplate) {
        return new UserRepository(jdbcTemplate);
    }
}

@Service
public class OrderService {
    private final PaymentGateway paymentGateway;

    @Autowired
    public OrderService(@Qualifier("alipayGateway") PaymentGateway paymentGateway) {
        this.paymentGateway = paymentGateway;
    }
}

@Service
public class EmailService {
    @Value("${smtp.host:smtp.example.com}")
    private String smtpHost;

    @Value("${smtp.port:587}")
    private int smtpPort;

    @Value("#{systemProperties['user.home']}/logs")
    private String logPath;  // SpEL 表达式
}

@Aspect
@Component
public class LoggingAspect {

    // 定义切点：Service 层所有方法
    @Pointcut("execution(* com.example.service.*.*(..))")
    public void serviceLayer() {}

    // 环绕通知：记录方法耗时
    @Around("serviceLayer()")
    public Object logAround(ProceedingJoinPoint joinPoint) throws Throwable {
        long start = System.currentTimeMillis();
        String methodName = joinPoint.getSignature().getName();

        try {
            Object result = joinPoint.proceed();
            long duration = System.currentTimeMillis() - start;
            System.out.printf("[LOG] %s executed in %dms%n", methodName, duration);
            return result;
        } catch (Exception e) {
            long duration = System.currentTimeMillis() - start;
            System.err.printf("[LOG] %s failed after %dms: %s%n", methodName, duration, e.getMessage());
            throw e;
        }
    }
}

@Aspect
@Component
public class SecurityAspect {

    @Pointcut("@annotation(com.example.annotation.RequireAdmin)")
    public void adminOperation() {}

    @Before("adminOperation()")
    public void checkAdmin(JoinPoint joinPoint) {
        Authentication auth = SecurityContextHolder.getContext().getAuthentication();
        if (auth == null || !auth.hasRole("ADMIN")) {
            throw new AccessDeniedException("需要管理员权限");
        }
    }
}

@Repository
public class UserDao {
    private final JdbcTemplate jdbcTemplate;

    @Autowired
    public UserDao(JdbcTemplate jdbcTemplate) {
        this.jdbcTemplate = jdbcTemplate;
    }

    public User findById(Long id) {
        return jdbcTemplate.queryForObject(
            "SELECT id, name, email FROM users WHERE id = ?",
            new BeanPropertyRowMapper<>(User.class),
            id
        );
    }

    public List<User> findAll() {
        return jdbcTemplate.query(
            "SELECT id, name, email FROM users",
            new BeanPropertyRowMapper<>(User.class)
        );
    }

    public int updateEmail(Long id, String email) {
        return jdbcTemplate.update(
            "UPDATE users SET email = ? WHERE id = ?",
            email, id
        );
    }
}

@Service
public class OrderService {
    @Transactional
    public void createOrder(Order order) {
        // 1. 扣减库存
        inventoryService.deduct(order.getItemId(), order.getQuantity());
        // 2. 创建订单
        orderRepository.save(order);
        // 3. 扣减余额
        accountService.debit(order.getUserId(), order.getAmount());
        // 任意步骤异常，全部回滚
    }
}

@Transactional(
    propagation = Propagation.REQUIRED,
    isolation = Isolation.READ_COMMITTED,
    timeout = 30,
    readOnly = false,
    rollbackFor = {SQLException.class, BusinessException.class},
    noRollbackFor = {IllegalArgumentException.class}
)
public void transferMoney(Long from, Long to, BigDecimal amount) {
    // 转账逻辑
}

@Configuration
@EnableTransactionManagement
public class JpaConfig {

    @Bean
    public LocalContainerEntityManagerFactoryBean entityManagerFactory(DataSource dataSource) {
        HibernateJpaVendorAdapter vendorAdapter = new HibernateJpaVendorAdapter();
        vendorAdapter.setGenerateDdl(true);

        LocalContainerEntityManagerFactoryBean factory = new LocalContainerEntityManagerFactoryBean();
        factory.setJpaVendorAdapter(vendorAdapter);
        factory.setPackagesToScan("com.example.entity");
        factory.setDataSource(dataSource);
        return factory;
    }

    @Bean
    public PlatformTransactionManager transactionManager(EntityManagerFactory emf) {
        return new JpaTransactionManager(emf);
    }
}

public interface UserRepository extends JpaRepository<User, Long> {
    // 方法名解析自动生成查询
    List<User> findByNameContainingAndStatus(String name, UserStatus status);

    // 自定义 JPQL
    @Query("SELECT u FROM User u WHERE u.email LIKE %:domain")
    List<User> findByEmailDomain(@Param("domain") String domain);

    // 原生 SQL
    @Query(value = "SELECT * FROM users WHERE created_at > ?1", nativeQuery = true)
    List<User> findRecentUsers(LocalDateTime since);
}