SpringMVC的项目架构思想

SpringMVC的项目架构思想

一、DO和Model的区别

DO是对数据库表的映射。Model是处理业务逻辑的模型（领域模型）。例如：用户信息表和用户密码表分别是两个DO，但是对于实体用户来说，密码表的字段也属于用户，所以需要在Service层使用Model来处理业务逻辑，Model包含了两张表的字段的并集。在Mapper层使用DO，在Service层使用Model。

public class UserDO {
    private Integer id;
    private String name;
    private Boolean gender;
    private Integer age;
    private String telphone;
    private String registerType;
    private String thirdPartyId;
    //getter、setter

public class UserPasswordDO {
    private Integer id;
    private String encrptPassword;
    private Integer userId;
    //getter、setter

二、VO和Model的区别

VO（View Object视图对象）,用于前端展示。Model中包含了用户的密码数据，不应该通过Controller层返回给前端，这是不安全的操作。在Controller层通过VO返回部分可以展示到前端的数据即可。

public class UserModel {
    private Integer id;
    private String name;
    private Boolean gender;
    private Integer age;
    private String telphone;
    private String registerMode;
    private String thirdPartyId;
    private String encrptPassword;
    //getter、setter

public class UserVO {
    private Integer id;
    private String name;
    private Boolean gender;
    private Integer age;
    private String telphone;
    //getter、setter

三、层次结构

1. dao层：定义XXXMapper接口、对应的XXXMapper.xml在resource目录下的mapper文件夹里，使用数据模型DO（Data Object）

2. service层：定义XXXService接口、实现类XXXServiceImpl、领域模型Model

   @Service
   public class UserServiceImpl implements UserService {
   ​
       @Autowired
       private UserDOMapper userDOMapper;
       @Autowired
       private UserPasswordDOMapper userPasswordDOMapper;
   ​
       @Override
       public UserModel getUserById(Integer id) {
           UserDO userDO = userDOMapper.selectByPrimaryKey(id);
           if (userDO == null) {
               return null;
           }
           UserPasswordDO userPasswordDO = userPasswordDOMapper.selectByUid(userDO.getId());
           return covertFromDataObject(userDO, userPasswordDO);
       }
   ​
       private UserModel covertFromDataObject(UserDO userDO, UserPasswordDO userPasswordDO) {
           if (userDO == null) {
               return null;
           }
           UserModel userModel = new UserModel();
           BeanUtils.copyProperties(userDO, userModel);
           if (userPasswordDO != null) {
               userModel.setEncrptPassword(userPasswordDO.getEncrptPassword());
           }
           return userModel;
       }
   }

3. controller层：定义XXXController类、视图模型VO（View Object）

   @RestController("user")
   @RequestMapping("/user")
   public class UserController {
       @Autowired
       private UserService userService;
   ​
       @RequestMapping("/get")
       public UserVO getUser(@RequestParam(name = "id") Integer id){
           UserModel userModel = userService.getUserById(id);
           //将核心的领域模型对象转化为可供UI使用的VO
           return convertFromModel(userModel);
       }
   ​
       private UserVO convertFromModel(UserModel userModel){
           if(userModel == null){
               return null;
           }
           UserVO userVO = new UserVO();
           BeanUtils.copyProperties(userModel, userVO);
           return userVO;
       }
   }

四、归一化Controller层的响应信息

1. 定义一个公共的返回值类型

   public class CommonReturnType {
       //处理结果 success/fail
       //fail 返回通用的错误码格式
       //success 返回数据
       private String status;
       private Object data;
   ​
       public static CommonReturnType create(Object result, String status) {
           CommonReturnType returnType = new CommonReturnType();
           returnType.setStatus(status);
           returnType.setData(result);
           return returnType;
       }
   ​
       public static CommonReturnType create(Object result) {
           return CommonReturnType.create(result, "success");
       }
   ​
       public String getStatus() {
           return status;
       }
   ​
       public void setStatus(String status) {
           this.status = status;
       }
   ​
       public Object getData() {
           return data;
       }
   ​
       public void setData(Object data) {
           this.data = data;
       }
   }

2. 在Controller层返回CommonResultType

   @RequestMapping("/get")
   public CommonReturnType getUser(@RequestParam(name = "id") Integer id){
       UserModel userModel = userService.getUserById(id);
       //将核心的领域模型对象转化为可供UI使用的VO
       UserVO userVO =  convertFromModel(userModel);
       //返回通用对象
       return CommonReturnType.create(userVO);
   }

3. 前端得到的返回正确的结果

   {
       "status":"success",
       "data":{
           "id":1,
           "name":"张三",
           "gender":false,
           "age":12,
           "telphone":"123456"
       }
   }

4. 异常结果的处理（见下一Part）

五、 包装器业务异常类的实现

1. 定义一个公共错误接口/error

   public interface CommonError {
       public int getErrCode();
       public String getErrMsg();
       public CommonError setErrMsg(String errMsg);
   }

2. 定义一个枚举错误类/error

   public enum EmBusinessError implements CommonError {
       //通用错误类型 00001
       PARAMETER_VALIDATION_ERROR(00001,"参数不合法"),
       //用户信息相关 1000X
       USER_NOT_EXIST(10001,"用户不存在")
       //
       ;
       private EmBusinessError(int errCode, String errMsg){
           this.errCode = errCode;
           this.errMsg = errMsg;
       }
       private int errCode;
       private String errMsg;
       @Override
       public int getErrCode() {
           return this.errCode;
       }
   ​
       @Override
       public String getErrMsg() {
           return this.errMsg;
       }
   ​
       @Override
       public CommonError setErrMsg(String errMsg) {
           this.errMsg = errMsg;
           return this;
       }
   }

3. 定义异常包装类/exception

   //包装器业务异常类的实现
   public class BusinessException extends Exception implements CommonError {
       private CommonError commonError;
   ​
       //直接接收EmBusinessError的传参用于构造业务异常
       public BusinessException(CommonError commonError){
           super();
           this.commonError = commonError;
       }
   ​
       //接收自定义errMsg的方式构造业务异常
       public BusinessException(CommonError commonError, String errMsg){
           super();
           this.commonError = commonError;
           this.commonError.setErrMsg(errMsg);
       }
       @Override
       public int getErrCode() {
           return this.commonError.getErrCode();
       }
   ​
       @Override
       public String getErrMsg() {
           return this.commonError.getErrMsg();
       }
   ​
       @Override
       public CommonError setErrMsg(String errMsg) {
           this.commonError.setErrMsg(errMsg);
           return this;
       }
   }

4. 在Controller层抛出异常

   @RequestMapping("/get")
   public CommonReturnType getUser(@RequestParam(name = "id") Integer id) throws BusinessException {
       UserModel userModel = userService.getUserById(id);
       if(userModel == null){
           throw new BusinessException(EmBusinessError.USER_NOT_EXIST);
       }
       //将核心的领域模型对象转化为可供UI使用的VO
       UserVO userVO =  convertFromModel(userModel);
       //返回通用对象
       return CommonReturnType.create(userVO);
   }

六、异常的处理

1. 定义exceptionHandler解决未被Controller层吸收的exception

   @ExceptionHandler(Exception.class)
   @ResponseStatus(HttpStatus.OK)
   public Object handlerException(HttpServletRequest request, Exception ex){
       BusinessException businessException = (BusinessException) ex;
       CommonReturnType commonReturnType = new CommonReturnType();
       commonReturnType.setStatus("fail");
       Map<String, Object> responseData = new HashMap<>();
       responseData.put("errCode",businessException.getErrCode());
       responseData.put("errMsg",businessException.getErrMsg());
       commonReturnType.setData(responseData);
       return commonReturnType;
   }

2. 前端得到的JSON数据

   {"status":"fail",
    "data":{
        "errCode":10001,
        "errMsg":"用户不存在"
    }
   }

3. 优化异常处理，定义BaseController，其余Controller继承基类。

   @RestController
   public class BaseController {
       @ExceptionHandler(Exception.class)
       @ResponseStatus(HttpStatus.OK)
       public Object handlerException(HttpServletRequest request, Exception ex){
           Map<String, Object> responseData = new HashMap<>();
           if(ex instanceof BusinessException){
               BusinessException businessException = (BusinessException) ex;
               CommonReturnType commonReturnType = new CommonReturnType();
               commonReturnType.setStatus("fail");
               responseData.put("errCode",businessException.getErrCode());
               responseData.put("errMsg",businessException.getErrMsg());
           }
           else{
               responseData.put("errCode", EmBusinessError.UNKNOWN_ERROR.getErrCode());
               responseData.put("errMsg",EmBusinessError.UNKNOWN_ERROR.getErrMsg());
           }
           return CommonReturnType.create(responseData,"fail");
       }
   }