智能代码生成与优化助手

代码实现

# 文件: pom.xml
<!-- Spring Boot 后端示例：用户与订单 REST 服务 -->
<project xmlns="http://maven.apache.org/POM/4.0.0" 
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 
                             http://maven.apache.org/xsd/maven-4.0.0.xsd">
  <modelVersion>4.0.0</modelVersion>
  <groupId>com.example</groupId>
  <artifactId>shop-service</artifactId>
  <version>1.0.0</version>
  <name>shop-service</name>
  <properties>
    <java.version>17</java.version>
    <spring-boot.version>3.3.3</spring-boot.version>
  </properties>

  <dependencyManagement>
    <dependencies>
      <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-dependencies</artifactId>
        <version>${spring-boot.version}</version>
        <type>pom</type>
        <scope>import</scope>
      </dependency>
    </dependencies>
  </dependencyManagement>

  <dependencies>
    <!-- Web & Validation -->
    <dependency>
      <groupId>org.springframework.boot</groupId>
      <artifactId>spring-boot-starter-web</artifactId>
    </dependency>
    <dependency>
      <groupId>org.springframework.boot</groupId>
      <artifactId>spring-boot-starter-validation</artifactId>
    </dependency>
    <!-- JPA & DB -->
    <dependency>
      <groupId>org.springframework.boot</groupId>
      <artifactId>spring-boot-starter-data-jpa</artifactId>
    </dependency>
    <!-- H2 内存数据库，便于快速运行 -->
    <dependency>
      <groupId>com.h2database</groupId>
      <artifactId>h2</artifactId>
      <scope>runtime</scope>
    </dependency>
    <!-- 仅使用密码加密（不引入完整 security） -->
    <dependency>
      <groupId>org.springframework.security</groupId>
      <artifactId>spring-security-crypto</artifactId>
    </dependency>
    <!-- 测试（可选） -->
    <dependency>
      <groupId>org.springframework.boot</groupId>
      <artifactId>spring-boot-starter-test</artifactId>
      <scope>test</scope>
    </dependency>
  </dependencies>

  <build>
    <plugins>
      <plugin>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-maven-plugin</artifactId>
        <configuration>
          <mainClass>com.example.shop.Application</mainClass>
        </configuration>
      </plugin>
    </plugins>
  </build>
</project>

# 文件: src/main/resources/application.yml
server:
  port: 8080

spring:
  datasource:
    url: jdbc:h2:mem:shopdb;DB_CLOSE_DELAY=-1;MODE=MySQL
    username: sa
    password: ""
    driver-class-name: org.h2.Driver
    hikari:
      pool-name: ShopHikariPool
      minimum-idle: 5
      maximum-pool-size: 20
      idle-timeout: 60000
      max-lifetime: 1800000
      connection-timeout: 30000
      validation-timeout: 5000
      leak-detection-threshold: 20000
  jpa:
    hibernate:
      ddl-auto: update
    properties:
      hibernate:
        format_sql: true
        show_sql: false
        jdbc:
          batch_size: 50
        order_inserts: true
        order_updates: true
  jackson:
    serialization:
      WRITE_DATES_AS_TIMESTAMPS: false

logging:
  level:
    root: INFO
    com.example.shop: DEBUG

# 文件: src/main/java/com/example/shop/Application.java
package com.example.shop;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

@SpringBootApplication
public class Application {
  public static void main(String[] args) {
    SpringApplication.run(Application.class, args);
  }
}

# 文件: src/main/java/com/example/shop/domain/User.java
package com.example.shop.domain;

import jakarta.persistence.*;
import java.time.LocalDateTime;

@Entity
@Table(name = "users", 
       uniqueConstraints = @UniqueConstraint(name = "uk_users_username", columnNames = "username"))
public class User {
  @Id
  @GeneratedValue(strategy = GenerationType.IDENTITY)
  private Long id;

  @Column(nullable = false, length = 64)
  private String username;

  @Column(nullable = false, length = 100)
  private String passwordHash;

  @Column(nullable = false)
  private LocalDateTime createdAt;

  public User() {}

  public User(String username, String passwordHash) {
    this.username = username;
    this.passwordHash = passwordHash;
    this.createdAt = LocalDateTime.now();
  }

  public Long getId() { return id; }
  public void setId(Long id) { this.id = id; }
  public String getUsername() { return username; }
  public void setUsername(String username) { this.username = username; }
  public String getPasswordHash() { return passwordHash; }
  public void setPasswordHash(String passwordHash) { this.passwordHash = passwordHash; }
  public LocalDateTime getCreatedAt() { return createdAt; }
  public void setCreatedAt(LocalDateTime createdAt) { this.createdAt = createdAt; }
}

# 文件: src/main/java/com/example/shop/domain/OrderStatus.java
package com.example.shop.domain;

public enum OrderStatus {
  PENDING, PAID, CANCELLED
}

# 文件: src/main/java/com/example/shop/domain/Order.java
package com.example.shop.domain;

import jakarta.persistence.*;
import java.math.BigDecimal;
import java.time.LocalDateTime;

@Entity
@Table(name = "orders", indexes = {
    @Index(name = "idx_orders_user_id", columnList = "user_id"),
    @Index(name = "idx_orders_created_at", columnList = "createdAt")
})
public class Order {
  @Id
  @GeneratedValue(strategy = GenerationType.IDENTITY)
  private Long id;

  @ManyToOne(fetch = FetchType.LAZY, optional = false)
  @JoinColumn(name = "user_id", nullable = false,
              foreignKey = @ForeignKey(name = "fk_orders_user"))
  private User user;

  @Column(nullable = false, length = 128)
  private String itemName;

  @Column(nullable = false, precision = 12, scale = 2)
  private BigDecimal amount;

  @Enumerated(EnumType.STRING)
  @Column(nullable = false, length = 16)
  private OrderStatus status = OrderStatus.PENDING;

  @Column(nullable = false)
  private LocalDateTime createdAt = LocalDateTime.now();

  public Order() {}

  public Order(User user, String itemName, BigDecimal amount) {
    this.user = user;
    this.itemName = itemName;
    this.amount = amount;
    this.status = OrderStatus.PENDING;
    this.createdAt = LocalDateTime.now();
  }

  public Long getId() { return id; }
  public void setId(Long id) { this.id = id; }
  public User getUser() { return user; }
  public void setUser(User user) { this.user = user; }
  public String getItemName() { return itemName; }
  public void setItemName(String itemName) { this.itemName = itemName; }
  public BigDecimal getAmount() { return amount; }
  public void setAmount(BigDecimal amount) { this.amount = amount; }
  public OrderStatus getStatus() { return status; }
  public void setStatus(OrderStatus status) { this.status = status; }
  public LocalDateTime getCreatedAt() { return createdAt; }
  public void setCreatedAt(LocalDateTime createdAt) { this.createdAt = createdAt; }
}

# 文件: src/main/java/com/example/shop/repository/UserRepository.java
package com.example.shop.repository;

import com.example.shop.domain.User;
import org.springframework.data.jpa.repository.JpaRepository;
import java.util.Optional;

public interface UserRepository extends JpaRepository<User, Long> {
  Optional<User> findByUsername(String username);
  boolean existsByUsername(String username);
}

# 文件: src/main/java/com/example/shop/repository/OrderRepository.java
package com.example.shop.repository;

import com.example.shop.domain.Order;
import com.example.shop.domain.User;
import org.springframework.data.domain.Page;
import org.springframework.data.domain.Pageable;
import org.springframework.data.jpa.repository.JpaRepository;

public interface OrderRepository extends JpaRepository<Order, Long> {
  Page<Order> findByUser(User user, Pageable pageable);
}

# 文件: src/main/java/com/example/shop/dto/RegisterRequest.java
package com.example.shop.dto;

import jakarta.validation.constraints.NotBlank;
import jakarta.validation.constraints.Size;

public class RegisterRequest {
  @NotBlank
  @Size(min = 3, max = 32)
  private String username;

  @NotBlank
  @Size(min = 6, max = 64)
  private String password;

  public String getUsername() { return username; }
  public void setUsername(String username) { this.username = username; }
  public String getPassword() { return password; }
  public void setPassword(String password) { this.password = password; }
}

# 文件: src/main/java/com/example/shop/dto/LoginRequest.java
package com.example.shop.dto;

import jakarta.validation.constraints.NotBlank;

public class LoginRequest {
  @NotBlank
  private String username;
  @NotBlank
  private String password;

  public String getUsername() { return username; }
  public void setUsername(String username) { this.username = username; }
  public String getPassword() { return password; }
  public void setPassword(String password) { this.password = password; }
}

# 文件: src/main/java/com/example/shop/dto/LoginResponse.java
package com.example.shop.dto;

public class LoginResponse {
  private String token;

  public LoginResponse() {}
  public LoginResponse(String token) { this.token = token; }

  public String getToken() { return token; }
  public void setToken(String token) { this.token = token; }
}

# 文件: src/main/java/com/example/shop/dto/OrderCreateRequest.java
package com.example.shop.dto;

import jakarta.validation.constraints.DecimalMin;
import jakarta.validation.constraints.NotBlank;
import jakarta.validation.constraints.NotNull;
import java.math.BigDecimal;

public class OrderCreateRequest {
  @NotBlank
  private String itemName;

  @NotNull
  @DecimalMin(value = "0.01")
  private BigDecimal amount;

  public String getItemName() { return itemName; }
  public void setItemName(String itemName) { this.itemName = itemName; }
  public BigDecimal getAmount() { return amount; }
  public void setAmount(BigDecimal amount) { this.amount = amount; }
}

# 文件: src/main/java/com/example/shop/dto/OrderResponse.java
package com.example.shop.dto;

import com.example.shop.domain.OrderStatus;
import java.math.BigDecimal;
import java.time.LocalDateTime;

public class OrderResponse {
  private Long id;
  private String itemName;
  private BigDecimal amount;
  private OrderStatus status;
  private LocalDateTime createdAt;

  public OrderResponse() {}

  public OrderResponse(Long id, String itemName, BigDecimal amount, OrderStatus status, LocalDateTime createdAt) {
    this.id = id;
    this.itemName = itemName;
    this.amount = amount;
    this.status = status;
    this.createdAt = createdAt;
  }

  public Long getId() { return id; }
  public void setId(Long id) { this.id = id; }
  public String getItemName() { return itemName; }
  public void setItemName(String itemName) { this.itemName = itemName; }
  public BigDecimal getAmount() { return amount; }
  public void setAmount(BigDecimal amount) { this.amount = amount; }
  public OrderStatus getStatus() { return status; }
  public void setStatus(OrderStatus status) { this.status = status; }
  public LocalDateTime getCreatedAt() { return createdAt; }
  public void setCreatedAt(LocalDateTime createdAt) { this.createdAt = createdAt; }
}

# 文件: src/main/java/com/example/shop/auth/TokenService.java
package com.example.shop.auth;

import org.springframework.stereotype.Service;
import java.time.Instant;
import java.time.Duration;
import java.util.Map;
import java.util.UUID;
import java.util.concurrent.ConcurrentHashMap;

@Service
public class TokenService {
  private static class TokenInfo {
    final Long userId;
    final Instant expireAt;
    TokenInfo(Long userId, Instant expireAt) {
      this.userId = userId; this.expireAt = expireAt;
    }
  }

  private final Map<String, TokenInfo> store = new ConcurrentHashMap<>();
  private static final Duration TTL = Duration.ofHours(24);

  public String issue(Long userId) {
    String token = UUID.randomUUID().toString();
    store.put(token, new TokenInfo(userId, Instant.now().plus(TTL)));
    return token;
  }

  public Long verify(String token) {
    TokenInfo info = store.get(token);
    if (info == null) return null;
    if (Instant.now().isAfter(info.expireAt)) {
      store.remove(token);
      return null;
    }
    return info.userId;
  }

  public void revoke(String token) {
    store.remove(token);
  }
}

# 文件: src/main/java/com/example/shop/auth/TokenAuthFilter.java
package com.example.shop.auth;

import jakarta.servlet.FilterChain;
import jakarta.servlet.ServletException;
import jakarta.servlet.http.HttpServletRequest;
import jakarta.servlet.http.HttpServletResponse;
import org.springframework.stereotype.Component;
import org.springframework.web.filter.OncePerRequestFilter;

import java.io.IOException;

@Component
public class TokenAuthFilter extends OncePerRequestFilter {

  private final TokenService tokenService;

  public TokenAuthFilter(TokenService tokenService) {
    this.tokenService = tokenService;
  }

  @Override
  protected boolean shouldNotFilter(HttpServletRequest request) {
    String path = request.getRequestURI();
    // 公共接口无需鉴权
    return path.startsWith("/api/auth/");
  }

  @Override
  protected void doFilterInternal(HttpServletRequest request, HttpServletResponse response, FilterChain filterChain)
      throws ServletException, IOException {
    String header = request.getHeader("Authorization");
    if (header == null || !header.startsWith("Bearer ")) {
      response.setStatus(HttpServletResponse.SC_UNAUTHORIZED);
      response.setContentType("application/json");
      response.getWriter().write("{\"message\":\"Unauthorized: missing Bearer token\"}");
      return;
    }
    String token = header.substring("Bearer ".length());
    Long userId = tokenService.verify(token);
    if (userId == null) {
      response.setStatus(HttpServletResponse.SC_UNAUTHORIZED);
      response.setContentType("application/json");
      response.getWriter().write("{\"message\":\"Unauthorized: invalid/expired token\"}");
      return;
    }
    request.setAttribute("userId", userId);
    filterChain.doFilter(request, response);
  }
}

# 文件: src/main/java/com/example/shop/service/UserService.java
package com.example.shop.service;

import com.example.shop.domain.User;
import com.example.shop.repository.UserRepository;
import org.springframework.dao.DataIntegrityViolationException;
import org.springframework.security.crypto.bcrypt.BCrypt;
import org.springframework.stereotype.Service;
import org.springframework.transaction.annotation.Transactional;
import java.util.Optional;

@Service
public class UserService {
  private final UserRepository userRepository;

  public UserService(UserRepository userRepository) {
    this.userRepository = userRepository;
  }

  @Transactional
  public User register(String username, String rawPassword) {
    if (userRepository.existsByUsername(username)) {
      throw new IllegalArgumentException("Username already exists");
    }
    String salt = BCrypt.gensalt(12);
    String hash = BCrypt.hashpw(rawPassword, salt);
    User user = new User(username, hash);
    try {
      return userRepository.save(user);
    } catch (DataIntegrityViolationException ex) {
      // 并发注册时兜底
      throw new IllegalArgumentException("Username already exists");
    }
  }

  @Transactional(readOnly = true)
  public Optional<User> authenticate(String username, String rawPassword) {
    return userRepository.findByUsername(username)
        .filter(u -> BCrypt.checkpw(rawPassword, u.getPasswordHash()));
  }

  @Transactional(readOnly = true)
  public User requireById(Long id) {
    return userRepository.findById(id)
        .orElseThrow(() -> new IllegalArgumentException("User not found"));
  }
}

# 文件: src/main/java/com/example/shop/service/OrderService.java
package com.example.shop.service;

import com.example.shop.domain.Order;
import com.example.shop.domain.User;
import com.example.shop.repository.OrderRepository;
import org.springframework.data.domain.Page;
import org.springframework.data.domain.Pageable;
import org.springframework.stereotype.Service;
import org.springframework.transaction.annotation.Transactional;
import java.math.BigDecimal;

@Service
public class OrderService {
  private final OrderRepository orderRepository;
  private final UserService userService;

  public OrderService(OrderRepository orderRepository, UserService userService) {
    this.orderRepository = orderRepository;
    this.userService = userService;
  }

  @Transactional
  public Order placeOrder(Long userId, String itemName, BigDecimal amount) {
    if (amount == null || amount.signum() <= 0) {
      throw new IllegalArgumentException("Amount must be positive");
    }
    User user = userService.requireById(userId);
    Order order = new Order(user, itemName, amount);
    return orderRepository.save(order);
  }

  @Transactional(readOnly = true)
  public Page<Order> listOrders(Long userId, Pageable pageable) {
    User user = userService.requireById(userId);
    return orderRepository.findByUser(user, pageable);
  }
}

# 文件: src/main/java/com/example/shop/web/AuthController.java
package com.example.shop.web;

import com.example.shop.auth.TokenService;
import com.example.shop.domain.User;
import com.example.shop.dto.LoginRequest;
import com.example.shop.dto.LoginResponse;
import com.example.shop.dto.RegisterRequest;
import com.example.shop.service.UserService;
import jakarta.validation.Valid;
import org.springframework.http.ResponseEntity;
import org.springframework.web.bind.annotation.*;

@RestController
@RequestMapping("/api/auth")
public class AuthController {

  private final UserService userService;
  private final TokenService tokenService;

  public AuthController(UserService userService, TokenService tokenService) {
    this.userService = userService;
    this.tokenService = tokenService;
  }

  @PostMapping("/register")
  public ResponseEntity<?> register(@Valid @RequestBody RegisterRequest req) {
    User user = userService.register(req.getUsername(), req.getPassword());
    return ResponseEntity.ok().body(
        java.util.Map.of("id", user.getId(), "username", user.getUsername(), "createdAt", user.getCreatedAt())
    );
  }

  @PostMapping("/login")
  public ResponseEntity<?> login(@Valid @RequestBody LoginRequest req) {
    return userService.authenticate(req.getUsername(), req.getPassword())
        .map(u -> ResponseEntity.ok(new LoginResponse(tokenService.issue(u.getId()))))
        .orElseGet(() -> ResponseEntity.status(401).body(java.util.Map.of("message", "Invalid credentials")));
  }
}

# 文件: src/main/java/com/example/shop/web/OrderController.java
package com.example.shop.web;

import com.example.shop.domain.Order;
import com.example.shop.dto.OrderCreateRequest;
import com.example.shop.dto.OrderResponse;
import com.example.shop.service.OrderService;
import jakarta.servlet.http.HttpServletRequest;
import jakarta.validation.Valid;
import org.springframework.data.domain.Page;
import org.springframework.data.domain.PageRequest;
import org.springframework.http.ResponseEntity;
import org.springframework.web.bind.annotation.*;

@RestController
@RequestMapping("/api/orders")
public class OrderController {

  private final OrderService orderService;

  public OrderController(OrderService orderService) {
    this.orderService = orderService;
  }

  @PostMapping
  public ResponseEntity<?> create(@Valid @RequestBody OrderCreateRequest req, HttpServletRequest request) {
    Long userId = (Long) request.getAttribute("userId");
    Order saved = orderService.placeOrder(userId, req.getItemName(), req.getAmount());
    return ResponseEntity.ok(toDto(saved));
  }

  @GetMapping
  public ResponseEntity<?> list(@RequestParam(defaultValue = "0") int page,
                                @RequestParam(defaultValue = "10") int size,
                                HttpServletRequest request) {
    Long userId = (Long) request.getAttribute("userId");
    Page<Order> result = orderService.listOrders(userId, PageRequest.of(page, size));
    return ResponseEntity.ok(result.map(this::toDto));
  }

  private OrderResponse toDto(Order o) {
    return new OrderResponse(o.getId(), o.getItemName(), o.getAmount(), o.getStatus(), o.getCreatedAt());
  }
}

# 文件: src/main/java/com/example/shop/exception/GlobalExceptionHandler.java
package com.example.shop.exception;

import org.springframework.http.HttpStatus;
import org.springframework.http.ResponseEntity;
import org.springframework.web.bind.MethodArgumentNotValidException;
import org.springframework.web.bind.annotation.ExceptionHandler;
import org.springframework.web.bind.annotation.RestControllerAdvice;
import java.util.Map;
import java.util.stream.Collectors;

@RestControllerAdvice
public class GlobalExceptionHandler {

  @ExceptionHandler(MethodArgumentNotValidException.class)
  public ResponseEntity<?> handleValidation(MethodArgumentNotValidException ex) {
    Map<String, String> errors = ex.getBindingResult().getFieldErrors().stream()
        .collect(Collectors.toMap(
            fe -> fe.getField(),
            fe -> fe.getDefaultMessage(),
            (a, b) -> a
        ));
    return ResponseEntity.badRequest().body(Map.of("message", "Validation failed", "errors", errors));
  }

  @ExceptionHandler(IllegalArgumentException.class)
  public ResponseEntity<?> handleIllegalArgument(IllegalArgumentException ex) {
    return ResponseEntity.badRequest().body(Map.of("message", ex.getMessage()));
  }

  @ExceptionHandler(Exception.class)
  public ResponseEntity<?> handleOther(Exception ex) {
    return ResponseEntity.status(HttpStatus.INTERNAL_SERVER_ERROR)
        .body(Map.of("message", "Internal error", "detail", ex.getMessage()));
  }
}

# 文件: scripts/run.sh
#!/usr/bin/env bash
set -e
cd "$(dirname "$0")/.."
if [ -x "./mvnw" ]; then
  ./mvnw spring-boot:run
else
  mvn spring-boot:run
fi

# 文件: scripts/run.ps1
Param()
$ErrorActionPreference = "Stop"
Set-Location (Split-Path $MyInvocation.MyCommand.Path) | Out-Null
Set-Location .. | Out-Null
if (Test-Path ".\mvnw.cmd") {
  .\mvnw.cmd spring-boot:run
} else {
  mvn spring-boot:run
}

代码说明

• 功能描述：

  • 提供用户注册与登录接口：/api/auth/register、/api/auth/login。
  • 使用简单的 Bearer Token 风格的鉴权（TokenService 发行/验证），保护订单相关接口。
  • 提供下单与查单 REST 接口：POST /api/orders 创建订单，GET /api/orders 分页查询当前用户订单。
  • 使用 Spring Data JPA 进行数据访问，内置 H2 内存数据库可直接运行。
  • 通过 @Transactional 管理事务，读写分离（readOnly），并通过 HikariCP 管理连接池。

• 参数说明：

  • RegisterRequest
    • username：字符串，3-32 字符
    • password：字符串，6-64 字符
  • LoginRequest
    • username：字符串，必填
    • password：字符串，必填
  • OrderCreateRequest
    • itemName：商品名称，必填
    • amount：订单金额，>= 0.01

• 返回值：

  • /api/auth/register：返回新用户的 id、username、createdAt。
  • /api/auth/login：返回 { token }。
  • /api/orders POST：返回新创建订单的 OrderResponse。
  • /api/orders GET：返回分页的订单列表（每条为 OrderResponse）。

使用示例

# 启动服务
bash scripts/run.sh
# 或 Windows PowerShell
# ./scripts/run.ps1

# 1) 注册用户
curl -sS -X POST "http://localhost:8080/api/auth/register" \
  -H "Content-Type: application/json" \
  -d '{"username":"alice","password":"p@ssw0rd"}'

# 2) 登录获取 token
TOKEN=$(curl -sS -X POST "http://localhost:8080/api/auth/login" \
  -H "Content-Type: application/json" \
  -d '{"username":"alice","password":"p@ssw0rd"}' | jq -r '.token')

echo "TOKEN=$TOKEN"

# 3) 创建订单
curl -sS -X POST "http://localhost:8080/api/orders" \
  -H "Authorization: Bearer $TOKEN" \
  -H "Content-Type: application/json" \
  -d '{"itemName":"Book","amount":39.99}'

# 4) 分页查询订单
curl -sS "http://localhost:8080/api/orders?page=0&size=10" \
  -H "Authorization: Bearer $TOKEN"

优化建议

• 性能考虑：

  • 连接池：
    • 使用 HikariCP（已在 application.yml 配置），根据环境调整 maximum-pool-size（典型为 CPU×2 到 ×4），并设置 leak-detection-threshold 便于检测连接泄漏。
    • 将 connection-timeout 控制在 30s 左右，避免请求长时间卡顿。
  • JPA 优化：
    • 已启用批量写入（hibernate.jdbc.batch_size=50），在批量插入/更新场景提升性能。
    • 为 orders(user_id, createdAt) 建立索引（已在实体上声明），加速查单。
    • 读操作标记 @Transactional(readOnly = true) 降低事务开销并允许底层优化。
  • 资源使用：
    • 控制 page size（如 10-50），避免一次性返回大量数据。
    • 关闭 show_sql 以减少 IO；生产环境将日志级别控制在 INFO。

• 扩展性：

  • 身份认证：
    • 将简单内存 Token 替换为 JWT（如加入 jjwt）或接入 Spring Security，支持角色和权限控制。
    • 将 Token 存储迁移至 Redis 以支持水平扩展与统一过期管理。
  • 业务扩展：
    • 订单状态流转：新增支付、取消等端点；引入事件驱动（如 Spring 事件或消息队列）进行异步处理。
    • 增加订单搜索与统计接口，支持时间范围、金额区间过滤。
  • 数据层：
    • 拆分读写数据源（Read/Write Split），读库使用只读事务与更大的连接池。
    • 引入审计字段（updatedAt、version）并开启乐观锁，保证并发安全。

• 注意事项：

  • 密码安全：使用 BCrypt 哈希（已实现），禁止明文存储。生产环境中增加密码复杂度校验与登录限制。
  • Token 安全：目前为内存存储且 24h 过期，重启后失效。生产环境应使用持久化或分布式缓存存储，并考虑刷新令牌。
  • 事务边界：仅在服务层使用 @Transactional，控制好方法粒度；避免在控制器层开启事务。
  • 数据迁移：H2 仅用于开发演示，上线需替换为 MySQL/PostgreSQL，并使用 Flyway/Liquibase 管理 schema。

• DAO层重构建议：

  • 现状常见问题（旧 DAO 层可能存在）：
    • 手写 JDBC，拼接 SQL 存在注入风险；连接未正确关闭导致泄漏；事务由调用方手工管理，边界不清晰。
    • 缺乏分页与统一的异常处理；模型映射分散、重复代码多。
  • 重构方案：
    • 采用 Repository 模式：迁移到 Spring Data JPA 或 MyBatis。
      • JPA：将表结构映射为 @Entity，定义 JpaRepository 接口，使用方法名派生或 @Query 实现查询。
      • MyBatis：提取 Mapper 接口与 XML/注解 SQL，保留对复杂 SQL 的精细控制。
    • 统一事务管理：在 Service 层使用 @Transactional 控制读写事务和传播行为；DAO 层不直接处理事务。
    • 安全与性能：
      • 参数化查询，彻底消除 SQL 注入风险。
      • 加入分页（Pageable 或 LIMIT/OFFSET），避免全表扫描。
      • 为高频查询字段加索引（如 users.username，orders.user_id, createdAt）。
      • 避免 N+1：JPA 中合理使用 fetch 策略与关联查询；MyBatis 中通过合适的 resultMap 与 join。
    • 连接管理：通过 DataSource（HikariCP）统一管理连接，禁止手工获取与释放。
    • 领域建模：提取 DTO/VO 与实体分离，控制序列化边界；在 Service 中完成组装与转换。
    • 代码规范：抽取公共异常与错误码；日志标准化；单元测试覆盖关键 DAO 方法。

• 事务与连接池优化建议（总结）：

  • 事务：
    • 写操作使用默认传播 REQUIRED；读操作使用 readOnly=true。
    • 根据业务考虑隔离级别：查询为 READ_COMMITTED，涉及库存扣减等可能考虑 REPEATABLE_READ 或使用悲观/乐观锁机制。
    • 缩小事务范围，避免将网络调用置于事务中。
  • 连接池：
    • 监控连接使用情况（Hikari 指标暴露到 Prometheus/Micrometer），按负载调整 maximum-pool-size。
    • 合理设置 maxLifetime 小于数据库端连接超时，避免池中存活连接被数据库端回收。
    • 使用连接健康检查（validationTimeout），并确保 SQL 或 ping（Hikari 默认配置即可）。