【发布时间】：2017-12-18 01:39:27
【问题描述】：
我可以看到 List 在 Thymeleaf 表单中成功使用 http://www.thymeleaf.org/doc/tutorials/2.1/thymeleafspring.html#dynamic-fields
<tr th:each="row,rowStat : *{rows}">
<td th:text="${rowStat.count}">1</td>
<td>
<select th:field="*{rows[__${rowStat.index}__].variety}"><!-- how to do this with Set? -->
<option th:each="var : ${allVarieties}"
th:value="${var.id}"
th:text="${var.name}">Thymus Thymi</option>
</select>
</td>
..
</tr>
我可以用 Set 而不是 List 做同样的事情吗？特别是代码中带有注释的行。 如何将 Set 元素分配给 th:field？
更新 1
我在我的项目中使用了它并继续使用 Set 并在提交/添加新行时，它给出了以下错误。它甚至没有达到相应的控制器方法。
org.springframework.beans.InvalidPropertyException：bean 类 [ae.tbits.atn.aiwacore.common.model.CatDescr] 的无效属性“catDescrDts [0]”：非法尝试获取属性“catDescrDts”引发异常；嵌套异常是 org.springframework.beans.InvalidPropertyException：bean 类 [ae.tbits.atn.aiwacore.common.model.CatDescr] 的无效属性“catDescrDts [0]”：无法从大小为 0 的集合中获取索引为 0 的元素，使用属性路径'catDescrDts[0]'访问
CatDescrDts 对应示例中的行，它与 CatDescr 实体具有多对一的关系。
堆栈跟踪
Caused by: org.springframework.beans.InvalidPropertyException: Invalid property 'catDescrDts[0]' of bean class [ae.tbits.atn.aiwacore.common.model.CatDescr]: Cannot get element with index 0 from Set of size 0, accessed using property path 'catDescrDts[0]'
at org.springframework.beans.AbstractNestablePropertyAccessor.getPropertyValue(AbstractNestablePropertyAccessor.java:661)
... 51 more
2017-07-13 16:23:57 ERROR ErrorController:19 - Exception during execution of SpringSecurity application
org.springframework.beans.InvalidPropertyException: Invalid property 'catDescrDts[0]' of bean class [ae.tbits.atn.aiwacore.common.model.CatDescr]: Illegal attempt to get property 'catDescrDts' threw exception; nested exception is org.springframework.beans.InvalidPropertyException: Invalid property 'catDescrDts[0]' of bean class [ae.tbits.atn.aiwacore.common.model.CatDescr]: Cannot get element with index 0 from Set of size 0, accessed using property path 'catDescrDts[0]'
at org.springframework.beans.AbstractNestablePropertyAccessor.getPropertyValue(AbstractNestablePropertyAccessor.java:708)
at org.springframework.beans.AbstractNestablePropertyAccessor.getNestedPropertyAccessor(AbstractNestablePropertyAccessor.java:836)
at org.springframework.beans.AbstractNestablePropertyAccessor.getPropertyAccessorForPropertyPath(AbstractNestablePropertyAccessor.java:813)
at org.springframework.beans.AbstractNestablePropertyAccessor.setPropertyValue(AbstractNestablePropertyAccessor.java:270)
at org.springframework.beans.AbstractPropertyAccessor.setPropertyValues(AbstractPropertyAccessor.java:95)
at org.springframework.validation.DataBinder.applyPropertyValues(DataBinder.java:834)
at org.springframework.validation.DataBinder.doBind(DataBinder.java:730)
at org.springframework.web.bind.WebDataBinder.doBind(WebDataBinder.java:192)
at org.springframework.web.bind.ServletRequestDataBinder.bind(ServletRequestDataBinder.java:106)
at org.springframework.web.servlet.mvc.method.annotation.ServletModelAttributeMethodProcessor.bindRequestParameters(ServletModelAttributeMethodProcessor.java:150)
at org.springframework.web.method.annotation.ModelAttributeMethodProcessor.resolveArgument(ModelAttributeMethodProcessor.java:114)
at org.springframework.web.method.support.HandlerMethodArgumentResolverComposite.resolveArgument(HandlerMethodArgumentResolverComposite.java:121)
at org.springframework.web.method.support.InvocableHandlerMethod.getMethodArgumentValues(InvocableHandlerMethod.java:161)
at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:128)
at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:114)
at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:827)
at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:738)
at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:85)
at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:963)
at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:897)
at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:970)
at org.springframework.web.servlet.FrameworkServlet.doPost(FrameworkServlet.java:872)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:707)
at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:846)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:790)
at io.undertow.servlet.handlers.ServletHandler.handleRequest(ServletHandler.java:85)
at io.undertow.servlet.handlers.security.ServletSecurityRoleHandler.handleRequest(ServletSecurityRoleHandler.java:62)
at io.undertow.servlet.handlers.ServletDispatchingHandler.handleRequest(ServletDispatchingHandler.java:36)
at org.wildfly.extension.undertow.security.SecurityContextAssociationHandler.handleRequest(SecurityContextAssociationHandler.java:78)
at io.undertow.server.handlers.PredicateHandler.handleRequest(PredicateHandler.java:43)
at io.undertow.servlet.handlers.security.SSLInformationAssociationHandler.handleRequest(SSLInformationAssociationHandler.java:131)
at io.undertow.servlet.handlers.security.ServletAuthenticationCallHandler.handleRequest(ServletAuthenticationCallHandler.java:57)
at io.undertow.server.handlers.PredicateHandler.handleRequest(PredicateHandler.java:43)
at io.undertow.security.handlers.AbstractConfidentialityHandler.handleRequest(AbstractConfidentialityHandler.java:46)
at io.undertow.servlet.handlers.security.ServletConfidentialityConstraintHandler.handleRequest(ServletConfidentialityConstraintHandler.java:64)
at io.undertow.security.handlers.AuthenticationMechanismsHandler.handleRequest(AuthenticationMechanismsHandler.java:60)
at io.undertow.servlet.handlers.security.CachedAuthenticatedSessionHandler.handleRequest(CachedAuthenticatedSessionHandler.java:77)
at io.undertow.security.handlers.NotificationReceiverHandler.handleRequest(NotificationReceiverHandler.java:50)
at io.undertow.security.handlers.AbstractSecurityContextAssociationHandler.handleRequest(AbstractSecurityContextAssociationHandler.java:43)
at io.undertow.server.handlers.PredicateHandler.handleRequest(PredicateHandler.java:43)
at org.wildfly.extension.undertow.security.jacc.JACCContextIdHandler.handleRequest(JACCContextIdHandler.java:61)
at io.undertow.server.handlers.PredicateHandler.handleRequest(PredicateHandler.java:43)
at io.undertow.server.handlers.PredicateHandler.handleRequest(PredicateHandler.java:43)
at io.undertow.servlet.handlers.ServletInitialHandler.handleFirstRequest(ServletInitialHandler.java:284)
at io.undertow.servlet.handlers.ServletInitialHandler.dispatchRequest(ServletInitialHandler.java:263)
at io.undertow.servlet.handlers.ServletInitialHandler.access$000(ServletInitialHandler.java:81)
at io.undertow.servlet.handlers.ServletInitialHandler$1.handleRequest(ServletInitialHandler.java:174)
at io.undertow.server.Connectors.executeRootHandler(Connectors.java:202)
at io.undertow.server.HttpServerExchange$1.run(HttpServerExchange.java:793)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
at java.lang.Thread.run(Thread.java:745)
Caused by: org.springframework.beans.InvalidPropertyException: Invalid property 'catDescrDts[0]' of bean class [ae.tbits.atn.aiwacore.common.model.CatDescr]: Cannot get element with index 0 from Set of size 0, accessed using property path 'catDescrDts[0]'
at org.springframework.beans.AbstractNestablePropertyAccessor.getPropertyValue(AbstractNestablePropertyAccessor.java:661)
... 51 more
更新 2
放一些代码..
- 首次调用 create 时，表单显示正常，但行为空。
- 当我单击保存或添加新行时，在调用控制器 save() 之前会出现该错误。
- 如果我注释掉 th:field 行，错误就消失了。
控制器
@GetMapping({"/create"})
public String create(ModelMap model){
CatDescr catDescr = new CatDescr();
//add 1 empty row for catDescrDt
int noOfCatDescrDts = 1;
catDescr.setCatDescrDts(getNewCatDescrDts(noOfCatDescrDts, catDescr));
model.addAttribute("catDescr", catDescr);
return "catDescr/create";
}
@PostMapping(value="/create", params={"save"})
public String save(final CatDescr catDescr
, final BindingResult bindingResult, final ModelMap model){
...
CatDescr updatedCatDescr = catDescrService.save(catDescr);
model.clear();
return "redirect:/catDescr/create";
}
@RequestMapping(value="/create", params={"addCatDescrDtRow"})
public String addCatDescrDtRow(ModelMap model, final CatDescr catDescr, final BindingResult bindingResult) {
catDescr.getCatDescrDts().add(new CatDescrDt());
...
return "catDescr/create";
}
查看
<ul th:each="item, stat: *{catDescrDts}">
<li>
<input type="text" th:field="*{catDescrDts[__${stat.index}__].name}" th:id="${'catDescrDts'+stat.index+'.name'}">
</li>
【问题讨论】：
-
是的，它应该与 Set 一起正常工作，事实上任何 Iterable 或 Array 都应该没问题。虽然您可能无法保证 Set 元素的顺序。
-
试过了，不行。错误似乎出现在 set 像数组一样被访问的行。发布堆栈跟踪.. 谢谢。
-
异常似乎是说您正在尝试访问集合中的第一个元素，但集合是空的。
-
@Janar 是的，你是对的。除了在我的代码中没有任何地方，我尝试直接访问 Set 的元素，例如 [0]。检查我的控制器，设置不为空。并且视图最初显示表单，当我发布（保存或添加新行）时，我收到此错误。堆栈跟踪似乎表明发布错误，未到达控制器。将代码 sn-ps 放入更新 2。
-
对不起，我想我误解了你的问题。也许我应该澄清一下，您可以在 Thymeleaf 中使用 Set 的计数器和索引，但您不能将控制器中的 Set 直接绑定到对象。 Spring 使用 getter 和 setter 来绑定它无法通过使用带有 Set 的索引的对象。尝试自定义 Getter/Setter，例如 this
标签： spring-mvc thymeleaf