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业务层的抽取和业务层方法的实现详解

news 2025/10/4 10:11:27

业务层的抽取和业务层方法的实现详解

1. 业务层的作用和重要性

业务层的核心职责

  • 业务逻辑处理：实现具体的业务规则和流程
  • 事务管理：确保业务操作的原子性
  • 服务编排：协调多个DAO操作完成复杂业务
  • 异常处理：统一的业务异常处理机制
  • 权限控制：业务级别的权限验证

2. 业务层的分层架构

标准的三层架构

表现层 (Controller/View)↓
业务层 (Service)          ← 我们重点关注的层次↓
数据访问层 (DAO)↓
数据库 (Database)

3. 业务层的抽取策略

3.1 按业务领域划分

// 用户相关业务
UserService├── UserRegistrationService├── UserAuthenticationService└── UserProfileService// 账户相关业务  
AccountService├── AccountTransferService├── AccountQueryService└── AccountManagementService// 交易相关业务
TransactionService├── PaymentService├── WithdrawalService└── TransferService

3.2 按功能复杂度划分

// 简单业务：直接CRUD操作
BasicAccountService// 复杂业务：涉及多个领域
ComplexTransferService// 组合业务：多个简单业务的组合
CompositeBusinessService

4. 业务层接口设计

4.1 业务层接口定义

package com.bank.service;import com.bank.entity.Account;
import com.bank.entity.Transaction;
import com.bank.exception.BusinessException;import java.math.BigDecimal;
import java.util.List;/*** 账户业务服务接口* 定义所有账户相关的业务操作*/
public interface AccountService {// ==================== 账户管理业务 ====================/*** 开户业务* @param account 账户信息* @return 开户结果* @throws BusinessException 业务异常*/boolean openAccount(Account account) throws BusinessException;/*** 销户业务* @param accountId 账户ID* @return 销户结果* @throws BusinessException 业务异常*/boolean closeAccount(Long accountId) throws BusinessException;/*** 账户状态管理* @param accountId 账户ID* @param status 状态* @return 操作结果* @throws BusinessException 业务异常*/boolean manageAccountStatus(Long accountId, Integer status) throws BusinessException;// ==================== 账户查询业务 ====================/*** 查询账户详情* @param accountId 账户ID* @return 账户信息* @throws BusinessException 业务异常*/Account getAccountDetail(Long accountId) throws BusinessException;/*** 查询用户所有账户* @param userId 用户ID* @return 账户列表* @throws BusinessException 业务异常*/List<Account> getUserAccounts(Long userId) throws BusinessException;/*** 查询账户余额* @param accountId 账户ID* @return 账户余额* @throws BusinessException 业务异常*/BigDecimal getAccountBalance(Long accountId) throws BusinessException;// ==================== 资金业务 ====================/*** 存款业务* @param accountId 账户ID* @param amount 存款金额* @param remark 备注* @return 存款结果* @throws BusinessException 业务异常*/boolean deposit(Long accountId, BigDecimal amount, String remark) throws BusinessException;/*** 取款业务* @param accountId 账户ID* @param amount 取款金额* @param remark 备注* @return 取款结果* @throws BusinessException 业务异常*/boolean withdraw(Long accountId, BigDecimal amount, String remark) throws BusinessException;/*** 转账业务* @param fromAccountId 转出账户* @param toAccountId 转入账户* @param amount 转账金额* @param remark 备注* @return 转账结果* @throws BusinessException 业务异常*/boolean transfer(Long fromAccountId, Long toAccountId, BigDecimal amount, String remark) throws BusinessException;// ==================== 交易查询业务 ====================/*** 查询账户交易流水* @param accountId 账户ID* @param startDate 开始日期* @param endDate 结束日期* @return 交易列表* @throws BusinessException 业务异常*/List<Transaction> getAccountTransactions(Long accountId, String startDate, String endDate) throws BusinessException;/*** 查询交易详情* @param transactionId 交易ID* @return 交易详情* @throws BusinessException 业务异常*/Transaction getTransactionDetail(Long transactionId) throws BusinessException;
}

5. 业务层实现详解

5.1 基础业务服务实现

package com.bank.service.impl;import com.bank.dao.AccountDAO;
import com.bank.dao.TransactionDAO;
import com.bank.dao.UserDAO;
import com.bank.entity.Account;
import com.bank.entity.Transaction;
import com.bank.entity.User;
import com.bank.exception.BusinessException;
import com.bank.service.AccountService;
import com.bank.util.TransactionManager;import java.math.BigDecimal;
import java.util.Date;
import java.util.List;/*** 账户业务服务实现*/
public class AccountServiceImpl implements AccountService {// 依赖的DAO组件private final AccountDAO accountDAO;private final TransactionDAO transactionDAO;private final UserDAO userDAO;// 事务管理器private final TransactionManager transactionManager;/*** 构造方法注入依赖*/public AccountServiceImpl(AccountDAO accountDAO, TransactionDAO transactionDAO,UserDAO userDAO,TransactionManager transactionManager) {this.accountDAO = accountDAO;this.transactionDAO = transactionDAO;this.userDAO = userDAO;this.transactionManager = transactionManager;}// ==================== 账户管理业务实现 ====================@Overridepublic boolean openAccount(Account account) throws BusinessException {// 参数验证validateAccount(account);try {// 开启事务transactionManager.beginTransaction();// 1. 验证用户是否存在User user = userDAO.findById(account.getUserId());if (user == null) {throw new BusinessException("USER_NOT_EXIST", "用户不存在");}// 2. 验证账户是否已存在if (accountDAO.existsByAccountNumber(account.getAccountNumber())) {throw new BusinessException("ACCOUNT_EXISTS", "账户已存在");}// 3. 设置账户默认值account.setBalance(BigDecimal.ZERO);account.setStatus(1); // 正常状态account.setCreateTime(new Date());account.setUpdateTime(new Date());// 4. 创建账户boolean success = accountDAO.insert(account);if (!success) {throw new BusinessException("CREATE_ACCOUNT_FAILED", "创建账户失败");}// 5. 记录开户交易流水Transaction transaction = createTransaction(account.getId(), Transaction.TransactionType.OPEN_ACCOUNT, BigDecimal.ZERO, "开户");transactionDAO.insert(transaction);// 提交事务transactionManager.commit();return true;} catch (Exception e) {// 回滚事务transactionManager.rollback();if (e instanceof BusinessException) {throw (BusinessException) e;}throw new BusinessException("OPEN_ACCOUNT_ERROR", "开户业务异常", e);}}@Overridepublic boolean closeAccount(Long accountId) throws BusinessException {try {transactionManager.beginTransaction();// 1. 验证账户是否存在Account account = accountDAO.findById(accountId);if (account == null) {throw new BusinessException("ACCOUNT_NOT_EXIST", "账户不存在");}// 2. 验证账户状态if (account.getStatus() == 0) {throw new BusinessException("ACCOUNT_ALREADY_CLOSED", "账户已销户");}// 3. 验证账户余额if (account.getBalance().compareTo(BigDecimal.ZERO) != 0) {throw new BusinessException("ACCOUNT_BALANCE_NOT_ZERO", "账户余额不为零，无法销户");}// 4. 更新账户状态account.setStatus(0); // 销户状态account.setUpdateTime(new Date());boolean success = accountDAO.update(account);if (!success) {throw new BusinessException("CLOSE_ACCOUNT_FAILED", "销户失败");}// 5. 记录销户流水Transaction transaction = createTransaction(accountId, Transaction.TransactionType.CLOSE_ACCOUNT, BigDecimal.ZERO, "销户");transactionDAO.insert(transaction);transactionManager.commit();return true;} catch (Exception e) {transactionManager.rollback();if (e instanceof BusinessException) {throw (BusinessException) e;}throw new BusinessException("CLOSE_ACCOUNT_ERROR", "销户业务异常", e);}}// ==================== 资金业务实现 ====================@Overridepublic boolean deposit(Long accountId, BigDecimal amount, String remark) throws BusinessException {// 参数验证validateAmount(amount);try {transactionManager.beginTransaction();// 1. 验证账户Account account = validateAndGetAccount(accountId);// 2. 执行存款BigDecimal newBalance = account.getBalance().add(amount);boolean success = accountDAO.updateBalance(accountId, newBalance);if (!success) {throw new BusinessException("DEPOSIT_FAILED", "存款操作失败");}// 3. 记录交易流水Transaction transaction = createTransaction(accountId, Transaction.TransactionType.DEPOSIT, amount, remark);transactionDAO.insert(transaction);transactionManager.commit();return true;} catch (Exception e) {transactionManager.rollback();if (e instanceof BusinessException) {throw (BusinessException) e;}throw new BusinessException("DEPOSIT_ERROR", "存款业务异常", e);}}@Overridepublic boolean withdraw(Long accountId, BigDecimal amount, String remark) throws BusinessException {// 参数验证validateAmount(amount);try {transactionManager.beginTransaction();// 1. 验证账户Account account = validateAndGetAccount(accountId);// 2. 验证余额是否充足if (account.getBalance().compareTo(amount) < 0) {throw new BusinessException("INSUFFICIENT_BALANCE", "账户余额不足");}// 3. 执行取款BigDecimal newBalance = account.getBalance().subtract(amount);boolean success = accountDAO.updateBalance(accountId, newBalance);if (!success) {throw new BusinessException("WITHDRAW_FAILED", "取款操作失败");}// 4. 记录交易流水Transaction transaction = createTransaction(accountId, Transaction.TransactionType.WITHDRAW, amount.negate(), // 取款为负数remark);transactionDAO.insert(transaction);transactionManager.commit();return true;} catch (Exception e) {transactionManager.rollback();if (e instanceof BusinessException) {throw (BusinessException) e;}throw new BusinessException("WITHDRAW_ERROR", "取款业务异常", e);}}@Overridepublic boolean transfer(Long fromAccountId, Long toAccountId, BigDecimal amount, String remark) throws BusinessException {// 参数验证validateAmount(amount);if (fromAccountId.equals(toAccountId)) {throw new BusinessException("TRANSFER_TO_SELF", "不能向自己转账");}try {transactionManager.beginTransaction();// 1. 验证转出账户Account fromAccount = validateAndGetAccount(fromAccountId);// 2. 验证转入账户Account toAccount = validateAndGetAccount(toAccountId);// 3. 验证转出账户余额if (fromAccount.getBalance().compareTo(amount) < 0) {throw new BusinessException("INSUFFICIENT_BALANCE", "转出账户余额不足");}// 4. 执行转账操作BigDecimal fromNewBalance = fromAccount.getBalance().subtract(amount);BigDecimal toNewBalance = toAccount.getBalance().add(amount);boolean success1 = accountDAO.updateBalance(fromAccountId, fromNewBalance);boolean success2 = accountDAO.updateBalance(toAccountId, toNewBalance);if (!success1 || !success2) {throw new BusinessException("TRANSFER_FAILED", "转账操作失败");}// 5. 记录交易流水（两条）Transaction fromTransaction = createTransaction(fromAccountId, Transaction.TransactionType.TRANSFER_OUT, amount.negate(), "转账至账户：" + toAccount.getAccountNumber() + "，" + remark);Transaction toTransaction = createTransaction(toAccountId, Transaction.TransactionType.TRANSFER_IN, amount, "收到账户：" + fromAccount.getAccountNumber() + "转账，" + remark);transactionDAO.insert(fromTransaction);transactionDAO.insert(toTransaction);transactionManager.commit();return true;} catch (Exception e) {transactionManager.rollback();if (e instanceof BusinessException) {throw (BusinessException) e;}throw new BusinessException("TRANSFER_ERROR", "转账业务异常", e);}}// ==================== 查询业务实现 ====================@Overridepublic Account getAccountDetail(Long accountId) throws BusinessException {try {Account account = accountDAO.findById(accountId);if (account == null) {throw new BusinessException("ACCOUNT_NOT_EXIST", "账户不存在");}return account;} catch (Exception e) {throw new BusinessException("QUERY_ACCOUNT_ERROR", "查询账户详情异常", e);}}@Overridepublic List<Account> getUserAccounts(Long userId) throws BusinessException {try {return accountDAO.findByUserId(userId);} catch (Exception e) {throw new BusinessException("QUERY_USER_ACCOUNTS_ERROR", "查询用户账户列表异常", e);}}@Overridepublic List<Transaction> getAccountTransactions(Long accountId, String startDate, String endDate) throws BusinessException {try {// 验证账户存在validateAndGetAccount(accountId);// 查询交易流水return transactionDAO.findByAccountIdAndDateRange(accountId, startDate, endDate);} catch (Exception e) {throw new BusinessException("QUERY_TRANSACTIONS_ERROR", "查询交易流水异常", e);}}// ==================== 私有辅助方法 ====================/*** 验证账户参数*/private void validateAccount(Account account) throws BusinessException {if (account == null) {throw new BusinessException("ACCOUNT_NULL", "账户信息不能为空");}if (account.getUserId() == null) {throw new BusinessException("USER_ID_NULL", "用户ID不能为空");}if (account.getAccountNumber() == null || account.getAccountNumber().trim().isEmpty()) {throw new BusinessException("ACCOUNT_NUMBER_NULL", "账户号码不能为空");}}/*** 验证金额参数*/private void validateAmount(BigDecimal amount) throws BusinessException {if (amount == null) {throw new BusinessException("AMOUNT_NULL", "金额不能为空");}if (amount.compareTo(BigDecimal.ZERO) <= 0) {throw new BusinessException("AMOUNT_INVALID", "金额必须大于零");}}/*** 验证并获取账户*/private Account validateAndGetAccount(Long accountId) throws BusinessException {Account account = accountDAO.findById(accountId);if (account == null) {throw new BusinessException("ACCOUNT_NOT_EXIST", "账户不存在");}if (account.getStatus() != 1) {throw new BusinessException("ACCOUNT_STATUS_INVALID", "账户状态异常");}return account;}/*** 创建交易记录*/private Transaction createTransaction(Long accountId, Transaction.TransactionType type, BigDecimal amount, String remark) {Transaction transaction = new Transaction();transaction.setAccountId(accountId);transaction.setType(type.getValue());transaction.setAmount(amount);transaction.setRemark(remark);transaction.setTransactionTime(new Date());transaction.setCreateTime(new Date());return transaction;}
}

6. 业务异常处理

6.1 业务异常类

package com.bank.exception;/*** 业务异常类*/
public class BusinessException extends Exception {private final String errorCode;private final String errorMessage;public BusinessException(String errorCode, String errorMessage) {super(errorCode + ": " + errorMessage);this.errorCode = errorCode;this.errorMessage = errorMessage;}public BusinessException(String errorCode, String errorMessage, Throwable cause) {super(errorCode + ": " + errorMessage, cause);this.errorCode = errorCode;this.errorMessage = errorMessage;}// Getter方法public String getErrorCode() {return errorCode;}public String getErrorMessage() {return errorMessage;}
}

6.2 异常代码枚举

package com.bank.constant;/*** 业务异常代码枚举*/
public enum ErrorCode {// 账户相关异常ACCOUNT_NOT_EXIST("ACCOUNT_001", "账户不存在"),ACCOUNT_EXISTS("ACCOUNT_002", "账户已存在"),ACCOUNT_BALANCE_NOT_ZERO("ACCOUNT_003", "账户余额不为零"),ACCOUNT_STATUS_INVALID("ACCOUNT_004", "账户状态异常"),// 用户相关异常USER_NOT_EXIST("USER_001", "用户不存在"),// 交易相关异常INSUFFICIENT_BALANCE("TRANSACTION_001", "余额不足"),TRANSFER_TO_SELF("TRANSACTION_002", "不能向自己转账"),AMOUNT_INVALID("TRANSACTION_003", "金额无效"),// 系统异常SYSTEM_ERROR("SYSTEM_001", "系统异常");private final String code;private final String message;ErrorCode(String code, String message) {this.code = code;this.message = message;}public String getCode() {return code;}public String getMessage() {return message;}
}

7. 事务管理器

7.1 事务管理器接口

package com.bank.util;/*** 事务管理器接口*/
public interface TransactionManager {/*** 开启事务*/void beginTransaction() throws Exception;/*** 提交事务*/void commit() throws Exception;/*** 回滚事务*/void rollback() throws Exception;
}

7.2 JDBC事务管理器实现

package com.bank.util;import java.sql.Connection;
import java.sql.SQLException;/*** JDBC事务管理器实现*/
public class JDBCTransactionManager implements TransactionManager {private final ThreadLocal<Connection> connectionHolder = new ThreadLocal<>();@Overridepublic void beginTransaction() throws Exception {Connection conn = connectionHolder.get();if (conn != null) {throw new Exception("事务已开启");}conn = DataSourceUtil.getConnection();conn.setAutoCommit(false);connectionHolder.set(conn);}@Overridepublic void commit() throws Exception {Connection conn = connectionHolder.get();if (conn == null) {throw new Exception("没有开启事务");}try {conn.commit();} finally {conn.setAutoCommit(true);conn.close();connectionHolder.remove();}}@Overridepublic void rollback() throws Exception {Connection conn = connectionHolder.get();if (conn == null) {throw new Exception("没有开启事务");}try {conn.rollback();} finally {conn.setAutoCommit(true);conn.close();connectionHolder.remove();}}/*** 获取当前线程的事务连接*/public Connection getConnection() {return connectionHolder.get();}
}

8. 业务层工厂类

8.1 服务工厂

package com.bank.factory;import com.bank.dao.AccountDAO;
import com.bank.dao.TransactionDAO;
import com.bank.dao.UserDAO;
import com.bank.dao.impl.AccountDAOImpl;
import com.bank.dao.impl.TransactionDAOImpl;
import com.bank.dao.impl.UserDAOImpl;
import com.bank.service.AccountService;
import com.bank.service.impl.AccountServiceImpl;
import com.bank.util.JDBCTransactionManager;
import com.bank.util.TransactionManager;/*** 业务服务工厂类*/
public class ServiceFactory {private static final TransactionManager transactionManager = new JDBCTransactionManager();/*** 获取账户服务实例*/public static AccountService getAccountService() {AccountDAO accountDAO = new AccountDAOImpl();TransactionDAO transactionDAO = new TransactionDAOImpl();UserDAO userDAO = new UserDAOImpl();return new AccountServiceImpl(accountDAO, transactionDAO, userDAO, transactionManager);}// 可以添加其他服务的工厂方法// public static UserService getUserService() { ... }// public static TransactionService getTransactionService() { ... }
}

9. 业务层测试

9.1 业务服务测试

package com.bank.test;import com.bank.entity.Account;
import com.bank.exception.BusinessException;
import com.bank.factory.ServiceFactory;
import com.bank.service.AccountService;import java.math.BigDecimal;
import java.util.Date;/*** 业务服务测试类*/
public class AccountServiceTest {public static void main(String[] args) {AccountService accountService = ServiceFactory.getAccountService();try {// 测试开户Account account = new Account();account.setUserId(1L);account.setAccountNumber("62220200010001");account.setAccountType(1);account.setCreateTime(new Date());boolean openResult = accountService.openAccount(account);System.out.println("开户结果: " + openResult);// 测试存款boolean depositResult = accountService.deposit(account.getId(), new BigDecimal("1000.00"), "测试存款");System.out.println("存款结果: " + depositResult);// 测试查询余额BigDecimal balance = accountService.getAccountBalance(account.getId());System.out.println("账户余额: " + balance);// 测试转账（需要先创建另一个账户）// boolean transferResult = accountService.transfer(account.getId(), 2L, new BigDecimal("500.00"), "测试转账");// System.out.println("转账结果: " + transferResult);} catch (BusinessException e) {System.err.println("业务异常: " + e.getErrorCode() + " - " + e.getErrorMessage());e.printStackTrace();}}
}

10. 最佳实践总结

10.1 业务层设计原则

  1. 单一职责原则：每个服务类只负责一个业务领域
  2. 依赖倒置原则：依赖抽象接口，不依赖具体实现
  3. 开闭原则：对扩展开放，对修改关闭
  4. 事务一致性原则：一个业务方法对应一个事务

10.2 业务方法设计要点

  1. 参数验证：在方法开始处验证所有输入参数
  2. 业务规则验证：验证业务规则和约束条件
  3. 事务边界：合理划分事务边界
  4. 异常处理：统一异常处理，提供有意义的错误信息
  5. 日志记录：记录重要的业务操作日志

10.3 性能考虑

  1. 数据库连接：合理使用连接池
  2. 事务粒度：控制事务粒度，避免长事务
  3. 批量操作：对批量操作进行优化
  4. 缓存策略：合理使用缓存提升性能

通过这样的业务层设计和实现，可以构建出结构清晰、可维护性强、业务逻辑完整的应用程序。

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