相关截图：

freemarker.core.InvalidReferenceException: The following has evaluated to null or missing:

==> evluation.member  [in template "detail.ftl" at line 135, column 53]

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Tip: It's the step after the last dot that caused this error, not those before it.

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Tip: If the failing expression is known to legally refer to something that's sometimes null or missing, either specify a default value like myOptionalVar!myDefault, or use <#if myOptionalVar??>when-present<#else>when-missing</#if>. (These only cover the last step of the expression; to cover the whole expression, use parenthesis: (myOptionalVar.foo)!myDefault, (myOptionalVar.foo)??

----

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FTL stack trace ("~" means nesting-related):

- Failed at: ${evluation.member.nickname}  [in template "detail.ftl" at line 135, column 51]

----

相关代码：

@Service
@Transactional(propagation = Propagation.NOT_SUPPORTED, readOnly = true)
public class EvaluationServiceImpl implements EvaluationService {

    @Resource
    private EvaluationMapper evaluationMapper;

    @Resource
    private BookMapper bookMapper;

    @Resource
    private MemberMapper memberMapper;
    /**
     * 查图书的短评
     * @param bookId
     * @return
     */

    public List<Evaluation> getEvaluationList(Long bookId) {
        Book book = bookMapper.selectById(bookId);//得到对应的book，注入到评价实体类

        QueryWrapper<Evaluation> queryWrapper  = new QueryWrapper<Evaluation>();
        //查询符合id，可用评价的评价并按照事件降序查询
        queryWrapper.eq("book_id", bookId);
        queryWrapper.eq("state", "enable");
        queryWrapper.orderByDesc("create_time");
        List<Evaluation> list = evaluationMapper.selectList(queryWrapper);
        //把查询出来的评价得到会员id这个属性，来查询对应的会员信息，并注入到短评类
        for (Evaluation evaluation : list) {
            Member member = memberMapper.selectById(evaluation.getMemberId());
            evaluation.setMember(member);
            evaluation.setBook(book);
        }
        return list;
    }
}


/**
 * 图书详情页
 * @param bookId
 * @return
 */
@GetMapping("/book/{bookId}")
@ResponseBody
public ModelAndView showDetail(@PathVariable("bookId") Long bookId) {
    ModelAndView modelAndView = new ModelAndView("/detail");
    Book book = bookService.getBook(bookId);
    modelAndView.addObject("book", book);
    List<Evaluation> evaluationList = evaluationService.getEvaluationList(bookId);
    modelAndView.addObject("evaluationList", evaluationList);
    return modelAndView;
}
​
​
​
​<div class="reply pl-2 pr-2">
    <#list evaluationList as evluation>
        <div>
            <div>
                <span class="pt-1 small text-black-50 mr-2">${evluation.createTime?string('MM-dd')}</span>
                <span class="mr-2 small pt-1">${evluation.member.nickname}</span>
                <span class="stars mr-2" data-score="${evluation.score}"></span>
                <#--${evluation.evaluationId?c}是因为数组大于等于1000会写成1，000
                的形式，所以var获得并传递给后台的是String，转化不成Long，
                这样写能转化成Long
                -->
                <button type="button" data-evaluation-id="${evluation.evaluationId?c}"
                        class="btn btn-success btn-sm text-white float-right" style="margin-top: -3px;">
                    <img style="width: 24px;margin-top: -5px;" class="mr-1"
                         src="https://img3.doubanio.com/f/talion/7a0756b3b6e67b59ea88653bc0cfa14f61ff219d/pics/card/ic_like_gray.svg"/>
                    <span>${evluation.enjoy}</span>
                </button>
            </div>

            <div class="row mt-2 small mb-3">
                ${evluation.content}
            </div>
            <hr/>
        </div>
    </#list>


</div>