Java中服务层返回类型转换与数据模型映射实践

// MainController.java
@RestController
@RequestMapping("/api")
public class MainController {
    private final Service acservice;

    public MainController(Service acservice) {
        this.acservice = acservice;
    }

    @GetMapping("/{id}")
    public ResponseEntity<Resresource> getId(@PathVariable("id") String id) {
        // 这里期望 Resresource 类型
        Resresource response = (Resresource) acservice.GtpResponse(id); // 运行时可能出现 ClassCastException
        return new ResponseEntity<>(response, HttpStatus.OK);
    }
}

// Service.java (原始结构)
public class Service {
    private final AccRepository accrepo;

    public Service(AccRepository accrepo) {
        this.accrepo = accrepo;
    }

    public Object GtpResponse(String id) {
        Optional<Acc> acc = accrepo.findById(id);
        if (acc.isPresent()) {
            // 假设这里返回 Resresource
            // return someResresourceObject;
        }

        Optional<Excel> response = Optional.ofNullable(getExcel(id));
        if (response.isPresent()) {
            // 这里返回 Excel 对象
            return response.get();
        }
        return null; // 或者抛出异常
    }

    private Excel getExcel(String id) {
        // 模拟获取 Excel 数据
        return new Excel("excelField_" + id, List.of(new AllDetailsExcel("excelDetail_" + id)));
    }
}

// Resresource.java
public class Resresource {
    private String id;
    private List<DetailRes> details;

    // 构造函数、Getter/Setter等
    public Resresource() {}
    public Resresource(String id, List<DetailRes> details) {
        this.id = id;
        this.details = details;
    }
    public String getId() { return id; }
    public void setId(String id) { this.id = id; }
    public List<DetailRes> getDetails() { return details; }
    public void setDetails(List<DetailRes> details) { this.details = details; }
}

// DetailRes.java
public class DetailRes {
    private String detailField;
    // 构造函数、Getter/Setter等
    public DetailRes() {}
    public DetailRes(String detailField) { this.detailField = detailField; }
    public String getDetailField() { return detailField; }
    public void setDetailField(String detailField) { this.detailField = detailField; }
}

// Excel.java
public class Excel {
    private String excelfield;
    private List<AllDetailsExcel> details;

    // 构造函数、Getter/Setter等
    public Excel() {}
    public Excel(String excelfield, List<AllDetailsExcel> details) {
        this.excelfield = excelfield;
        this.excelfield = excelfield;
        this.details = details;
    }
    public String getExcelfield() { return excelfield; }
    public void setExcelfield(String excelfield) { this.excelfield = excelfield; }
    public List<AllDetailsExcel> getDetails() { return details; }
    public void setDetails(List<AllDetailsExcel> details) { this.details = details; }
}

// AllDetailsExcel.java
public class AllDetailsExcel {
    private String excelDetailField;
    // 构造函数、Getter/Setter等
    public AllDetailsExcel() {}
    public AllDetailsExcel(String excelDetailField) { this.excelDetailField = excelDetailField; }
    public String getExcelDetailField() { return excelDetailField; }
    public void setExcelDetailField(String excelDetailField) { this.excelDetailField = excelDetailField; }
}

// AccRepository.java (示例接口)
interface AccRepository extends JpaRepository<Acc, String> {
    // ...
}

// Acc.java (示例实体)
class Acc {
    private String id;
    // ...
}

// ExcelToResresourceMapper.java
public class ExcelToResresourceMapper {

    /**
     * 将 Excel 对象转换为 Resresource 对象。
     * @param excel 待转换的 Excel 对象。
     * @return 转换后的 Resresource 对象。
     */
    public static Resresource map(Excel excel) {
        if (excel == null) {
            return null;
        }

        Resresource resresource = new Resresource();
        // 假设 Excel 的 excelfield 对应 Resresource 的 id
        resresource.setId(excel.getExcelfield());

        // 映射 details 列表，需要将 AllDetailsExcel 转换为 DetailRes
        if (excel.getDetails() != null) {
            List<DetailRes> detailResList = excel.getDetails().stream()
                .map(ExcelToResresourceMapper::mapDetail) // 映射子列表
                .collect(Collectors.toList());
            resresource.setDetails(detailResList);
        }

        return resresource;
    }

    /**
     * 将 AllDetailsExcel 对象转换为 DetailRes 对象。
     * @param allDetailsExcel 待转换的 AllDetailsExcel 对象。
     * @return 转换后的 DetailRes 对象。
     */
    private static DetailRes mapDetail(AllDetailsExcel allDetailsExcel) {
        if (allDetailsExcel == null) {
            return null;
        }
        DetailRes detailRes = new DetailRes();
        // 假设 AllDetailsExcel 的 excelDetailField 对应 DetailRes 的 detailField
        detailRes.setDetailField(allDetailsExcel.getExcelDetailField());
        return detailRes;
    }
}

// Service.java (重构后)
public class Service {
    private final AccRepository accrepo;

    public Service(AccRepository accrepo) {
        this.accrepo = accrepo;
    }

    /**
     * 根据ID获取响应数据，并确保返回类型为 Resresource。
     * @param id 唯一标识符。
     * @return 对应的 Resresource 对象。
     */
    public Resresource GtpResponse(String id) {
        Optional<Acc> acc = accrepo.findById(id);

        if (acc.isPresent()) {
            // 假设这里直接获取并返回 Resresource
            // return getResresourceFromAcc(acc.get()); // 示例：从 Acc 获取 Resresource
            // 为了与原问题保持一致，我们假设这里也可能触发 Excel 获取
        }

        // 如果上述逻辑没有返回 Resresource，则尝试获取 Excel 数据
        Optional<Excel> excelResponse = Optional.ofNullable(getExcel(id));
        if (excelResponse.isPresent()) {
            // 获取到 Excel 对象，使用映射器将其转换为 Resresource
            return ExcelToResresourceMapper.map(excelResponse.get());
        }

        // 如果两种情况都没有获取到数据，可以返回 null 或者抛出业务异常
        return null; // 或者 throw new ResourceNotFoundException("No data found for id: " + id);
    }

    private Excel getExcel(String id) {
        // 模拟获取 Excel 数据
        return new Excel("excelField_" + id, List.of(new AllDetailsExcel("excelDetail_" + id)));
    }

    // 示例：如果 Acc 也能直接生成 Resresource
    private Resresource getResresourceFromAcc(Acc acc) {
        // 实际业务逻辑：从 Acc 对象构建 Resresource
        return new Resresource(acc.getId(), Collections.emptyList()); // 简化示例
    }
}

// MainController.java (保持不变，但现在更安全)
@RestController
@RequestMapping("/api")
public class MainController {
    private final Service acservice;

    public MainController(Service acservice) {
        this.acservice = acservice;
    }

    @GetMapping("/{id}")
    public ResponseEntity<Resresource> getId(@PathVariable("id") String id) {
        // 现在 acservice.GtpResponse(id) 明确返回 Resresource，无需强制转换
        Resresource response = acservice.GtpResponse(id);
        if (response == null) {
            return new ResponseEntity<>(HttpStatus.NOT_FOUND); // 处理服务层返回null的情况
        }
        return new ResponseEntity<>(response, HttpStatus.OK);
    }
}