还是上次数据不能为空的问题，写到了C层测试。

先写一行测试代码，先期待一个200，但是我们是知道的，因为没有学科类别，这肯定会抛出异常，我们就是想看看Spring捕获这个异常之后给出的反馈是什么状态码。

@Test
public void saveTest() throws Exception {
    logger.debug("基础测试数据准备");
    MeasurementUnitCategory measurementUnitCategory = new MeasurementUnitCategory();
    String json = JSON.toJSONString(measurementUnitCategory);

    this.mockMvc.perform(post(baseUrl)
                        .header(xAuthKey, xAuthToken)
                        .contentType(MediaType.APPLICATION_JSON_UTF8)
                        .content(json))
                .andExpect(status().isOk());
}

测试一下，果然，控制台报错。

但是看一下报错信息，发现并不是我们期待的一个错误的状态码，而是200。同时下面还有异常抛出。

这说明Spring为我们抛出了这个DataIntegrityViolationException异常，但是却没有帮我们处理，这就需要我们手动处理然后返回给前台状态码。

MockHttpServletResponse:
           Status = 200
    Error message = null
          Headers = {X-Content-Type-Options=[nosniff], X-XSS-Protection=[1; mode=block], Cache-Control=[no-cache, no-store, max-age=0, must-revalidate], Pragma=[no-cache], Expires=[0], X-Application-Context=[application:-1], Content-Type=[application/json;charset=UTF-8], x-auth-token=[1b2b8d9f-3457-4277-879e-2ada48e3599e]}
     Content type = application/json;charset=UTF-8
             Body = {"id":8,"name":"","username":"usersdfdfwef23dfvdfwewef","mobile":"","pinyin":null,"createTime":1528338758059,"updateTime":1528338758059,"status":0,"department":{"id":1,"name":"内蒙古自治区管理部门","code":"","postalCode":"","address":"","legalName":"","legalPhone":"","registrantName":"","registrantPhone":"","registrantTel":null,"registrantMail":"","phone":"","pinyin":"neimengguzishiquguanglibumeng","registerDate":null,"createTime":1528338752423,"updateTime":1528338752423,"status":null,"createUser":null,"departmentType":{"id":1,"name":"管理部门","pinyin":"guanlibumen","createTime":1528338751963,"updateTime":1528338751963,"createUser":null},"district":{"id":1,"districtType":{"id":1,"name":"省","pinyin":"sheng"},"name":"内蒙古自治区","createUser":null,"pinyin":"neimengguzizhiqu","createTime":null,"updateTime":null},"checkAbility":false,"outOfRange":null,"standard":false},"roles":[],"createUser":null,"updateUser":null}
    Forwarded URL = null
   Redirected URL = null
          Cookies = []

org.springframework.web.util.NestedServletException: Request processing failed; nested exception is org.springframework.dao.DataIntegrityViolationException: could not execute statement; SQL [n/a]; constraint [null]; nested exception is org.hibernate.exception.ConstraintViolationException: could not execute statement
Caused by: org.springframework.dao.DataIntegrityViolationException: could not execute statement; SQL [n/a]; constraint [null]; nested exception is org.hibernate.exception.ConstraintViolationException: could not execute statement
Caused by: org.hibernate.exception.ConstraintViolationException: could not execute statement
Caused by: org.h2.jdbc.JdbcSQLException: NULL not allowed for column "DISCIPLINE_ID"; SQL statement:
insert into measurement_unit_category (id, discipline_id, is_asc) values (null, ?, ?) [23502-194]

理论上我们所有的异常都是由M层抛出，直接捕获或全局异常处理，是不会将异常抛给控制器的。

所以，我们需要全局异常处理，M层抛出异常，直接处理，返回xx状态码，而不将异常抛给控制器。

/**
 * 手动捕获数据冲突异常，经测试，该异常系由Spring抛出，但未捕获
 * @return HttpStatus.CONFLICT
 * 冲突错误，409
 * 参考：
 * https://*.com/questions/37248719/couldnt-catch-dataintegrityviolationexception-with-spring-data-rest
 */
@ExceptionHandler(value = DataIntegrityViolationException.class)
public ResponseEntity<JsonErrorResult> dataIntegrityViolationException(HttpServletRequest httpServletRequest, Exception exception) {
    logger.error("---数据不合法：---Host {} invokes url {} ERROR: {}", httpServletRequest.getRemoteHost(), httpServletRequest.getRequestURL(), exception.getMessage());
    return new ResponseEntity<>(new JsonErrorResult(httpServletRequest, exception), HttpStatus.CONFLICT);
}

我这里对状态码也不是很熟悉，去*上看到一个老哥是和我遇到了一样的问题，他解决的方案是捕获异常返回409(冲突)，参考原文。

异常捕获后，修改测试，期待状态码为409，Conflict。

@Test
public void saveTest() throws Exception {
    logger.debug("基础测试数据准备");
    MeasurementUnitCategory measurementUnitCategory = new MeasurementUnitCategory();
    String json = JSON.toJSONString(measurementUnitCategory);

    logger.debug("无学科的计量单位类别保存，期待409，冲突状态码");
    this.mockMvc.perform(post(baseUrl)
                        .header(xAuthKey, xAuthToken)
                        .contentType(MediaType.APPLICATION_JSON_UTF8)
                        .content(json))
                .andExpect(status().isConflict());
}

重新运行单元测试，通过。