无法将类型“java.lang.String”的属性值转换为所需类型“java.util.Date”

Question

我正在尝试使用 Spring MVC、Java 和 MySql 在我的 web 应用程序中实现完整的日历插件。当我尝试在我的 jsp 中使用“输入类型 = 日期”添加日期时出现此错误：

Field error in object 'event' on field 'endDate': rejected value [2018-03-13]; 
codes [typeMismatch.event.endDate,typeMismatch.endDate,typeMismatch.java.util.Date,typeMismatch];
arguments [org.springframework.context.support.DefaultMessageSourceResolvable: codes [event.endDate,endDate]; arguments [];
default message [endDate]]; default message [Failed to convert property value of type 'java.lang.String' 
to required type 'java.util.Date' for property 'endDate'; nested exception is org.springframework.core.convert.ConversionFailedException: 
Failed to convert from type java.lang.String to type @org.springframework.format.annotation.DateTimeFormat
java.util.Date for value '2018-03-13'; 
nested exception is java.lang.IllegalArgumentException: Unable to parse '2018-03-13']

在我的控制器类中，我使用 SimpleDateFormat 来格式化我的日期：

@RequestMapping(value = "add", method = RequestMethod.POST)
    public String add(@ModelAttribute("event") Event event,
            HttpServletRequest request,ServletRequestDataBinder binder,
            ModelMap modelMap){
        try{
            SimpleDateFormat simpleDateFormat = new SimpleDateFormat ("dd/MM/yyyy");
            event.setStartDate(simpleDateFormat.parse(request.getParameter("startDate")));
            event.setEndDate(simpleDateFormat.parse(request.getParameter("endDate")));

            eventService.create(event);
            return "redirect:../event.html";
        }catch (Exception e){
            modelMap.put("event", event);
            return "event/index";
        }   
    }

最后在我的 Jsp 中：

<fieldset>
        <legend>Event Information</legend>
    <s:form method ="post" commandName = "event"
        action="${pageContext.request.contextPath }/event/add.html">
        <table>
            <tr>
                <td>Name</td>
                <td><s:input path = "name"/></td>
            </tr>
            <tr>
                <td valign = "top">Description</td>
                <td><s:textarea path = "description" cols = "20" rows = "5" /></td>
            </tr>
            <tr>
                <td>Start Date</td>
                <td><input type = "date" name = "startDate" /></td>
            </tr>
            <tr>
                <td>End Date</td>
                <td><input type = "date" name = "endDate" /></td>
            </tr>
            <tr>
                <td>&nbsp;</td>
                <td><input type = "submit" value = "Save" /></td>
            </tr>
        </table>
    </s:form>
    </fieldset>

这是 DAO 实现：

@Repository("eventDAO")
public class EventDAOImpl implements EventDAO{

    @Autowired
    private SessionFactory sessionFactory;

    @SuppressWarnings("unchecked")
    @Override
    public List<EventEntity> findAll() {
        List <EventEntity> list = null;
        Session session = null;
        Transaction transaction = null;
        try{
            session = sessionFactory.openSession();
            transaction = session .beginTransaction();
            list = session.createQuery("select e.id as id, "
                    + "e.name as title, "
                    + "DATE_FORMAT(e.startDate, '%Y-%m-%d') as start, "
                    + "DATE_FORMAT(e.endDate, '%Y-%m-%d') as end "
                    + "from Event e")
                    .setResultTransformer(
                            Transformers.aliasToBean(EventEntity.class))
                    .list();
            transaction.commit();
        }catch(Exception e){
            list = null;
            if(transaction != null){
                transaction.rollback();
            }
        }finally{
            session.close();
        }
        return list;
    }

在我的实体类中，我将变量保存为日期，所以它是

private Date endDate;

我认为问题在于解析日期，但我不确定！对此问题的任何解释将不胜感激。

Answer 1

@ModelAttribute("event") Event event 将使 Spring 尝试将请求值 2018-03-13 绑定到 Event 类型内的 private Date endDate 字段。不会调用您的转换代码，因为错误发生在调用 add 方法之前。

您需要使用PropertyEditor 或Converter 定义全局转换逻辑，如here 所述，或使用org.springframework.format.annotation.DateTimeFormat 指定每个日期字段的格式：

@DateTimeFormat(pattern = "yyyy-MM-dd")
// or use @DateTimeFormat(pattern = DateTimeFormat.ISO.DATE)
private Date endDate;

Answer 2

request.getParameter("endDate") 返回字符串 "2018-03-13"。您需要在SimpleDateFormat中提供匹配格式

simpleDateFormat = new SimpleDateFormat("yyyy-MM-dd");
event.setEndDate(simpleDateFormat.parse(request.getParameter("endDate")));