如何在Service中传参选择使用MyBatis或JPA执行持久化操作

完全可以通过参数传递控制Service层调用不同持久化实现，下面是具体的修改方式：

基础实现（适配当前代码结构，改动最小） #

第一步：修正Controller层代码 #

你当前Controller里接收query参数的注解错误，Spring MVC中接收查询参数需要用@RequestParam，同时直接将persistenceType作为参数传入Service的save方法即可，无需你伪代码中写的manufacturerService(persistenceType)调用形式。
修改后Controller代码：

@RestController
@RequestMapping("/manufacturers")
public class ManufacturesController {

    public static final Logger LOG = LogManager.getLogger(ManufacturesController.class);

    @Autowired
    private ManufacturerService manufacturerService;

    @PostMapping
    public ResponseEntity<Manufacturer> createManufacturer(@RequestBody ManufacturerDTO manufacturer, 
                                                           @RequestParam String persistenceType) {
        LOG.info("START - createManufacturer");
        try {
            Manufacturer _manufacturer = ManufacturerMapper.toEntity(manufacturer);
            // 直接将persistenceType传入save方法
            manufacturerService.save(_manufacturer, persistenceType);
            LOG.info("STOP - createManufacturer");
            return new ResponseEntity<>(_manufacturer, HttpStatus.CREATED);
        } catch (Exception e) {
            LOG.error("Error description: ", e);
            LOG.info("STOP - createManufacturer");
            return new ResponseEntity<>(HttpStatus.INTERNAL_SERVER_ERROR);
        }
    }
}

第二步：调整Service层方法 #

先定义枚举约束持久化类型，避免字符串拼写错误，再修改save方法增加参数和判断逻辑：
首先定义持久化类型枚举：

public enum PersistenceTypeEnum {
    MYBATIS, JPA
}

修改后的Service代码：

@Service
public class ManufacturerService implements IManufacturerService {

    @Autowired
    private ManufacturerRepository manufacturerRepository;

    @Autowired
    private ManufacturerMapper manufacturerMapper;

    @Override
    @Transactional
    public Manufacturer save(Manufacturer manufacturer, String persistenceType) {
        // 先做参数合法性校验
        PersistenceTypeEnum type;
        try {
            type = PersistenceTypeEnum.valueOf(persistenceType.toUpperCase());
        } catch (IllegalArgumentException e) {
            throw new RuntimeException("不支持的持久化类型：" + persistenceType);
        }
        // 根据类型选择实现
        if (type == PersistenceTypeEnum.MYBATIS) {
            manufacturerMapper.insert(manufacturer);
            return manufacturer;
        } else {
            return manufacturerRepository.save(manufacturer);
        }
    }
}

记得同步修改你Service接口IManufacturerService中save方法的签名，增加persistenceType参数。 #

优化实现（策略模式，适合后续扩展） #

如果后续可能新增更多持久化实现，为了避免if/else逻辑臃肿，符合开闭原则，可以用策略模式重构：

1. 定义持久化操作抽象接口

public interface ManufacturerPersistenceHandler {
    Manufacturer save(Manufacturer manufacturer);
    PersistenceTypeEnum getType();
}

2. 分别实现MyBatis和JPA的处理器

@Component
public class MyBatisManufacturerHandler implements ManufacturerPersistenceHandler {
    @Autowired
    private ManufacturerMapper manufacturerMapper;
    
    @Override
    public Manufacturer save(Manufacturer manufacturer) {
        manufacturerMapper.insert(manufacturer);
        return manufacturer;
    }

    @Override
    public PersistenceTypeEnum getType() {
        return PersistenceTypeEnum.MYBATIS;
    }
}

@Component
public class JpaManufacturerHandler implements ManufacturerPersistenceHandler {
    @Autowired
    private ManufacturerRepository manufacturerRepository;
    
    @Override
    public Manufacturer save(Manufacturer manufacturer) {
        return manufacturerRepository.save(manufacturer);
    }

    @Override
    public PersistenceTypeEnum getType() {
        return PersistenceTypeEnum.JPA;
    }
}

3. Service中注入所有处理器，根据参数选择对应实现

@Service
public class ManufacturerService implements IManufacturerService {
    // Spring会自动注入所有实现了ManufacturerPersistenceHandler的Bean
    @Autowired
    private List<ManufacturerPersistenceHandler> handlerList;
    private Map<PersistenceTypeEnum, ManufacturerPersistenceHandler> handlerMap;

    // 初始化后将处理器转成Map方便查找
    @PostConstruct
    public void initHandlerMap() {
        handlerMap = handlerList.stream()
                .collect(Collectors.toMap(ManufacturerPersistenceHandler::getType, Function.identity()));
    }

    @Override
    @Transactional
    public Manufacturer save(Manufacturer manufacturer, String persistenceType) {
        PersistenceTypeEnum type = PersistenceTypeEnum.valueOf(persistenceType.toUpperCase());
        ManufacturerPersistenceHandler handler = handlerMap.get(type);
        if (handler == null) {
            throw new RuntimeException("不支持的持久化类型：" + persistenceType);
        }
        return handler.save(manufacturer);
    }
}

后续新增持久化实现只需要新增对应处理器类即可，无需修改原有Service逻辑。

内容的提问来源于stack exchange，提问作者KG_stackoverflow