从视图获取值到控制器，然后到另一个视图
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【中文标题】从视图获取值到控制器，然后到另一个视图【英文标题】：Getting values from a view to a controller, then to another view 【发布时间】：2020-10-10 19:33:35 【问题描述】：我的 index.html 列出了一些评论，当按下某个评论的标题时，我的控制器应该获取该评论的 id 并使用模板视图仅显示该评论的信息；它应该适用于任何 id/review。我现在在互联网上搜索了 2 个小时，但仍然找不到实现此目的所需的语法。
这是我当前的控制器：
@GetMapping("/id")
public String showSpecificItem(@PathVariable(name="id") Integer id, Model model)
Optional<Review> rev = rev_repo.findById(id);
model.addAttribute("reviews", rev);
return "index-specific";
这是带有标题的索引部分：
<div class="container py-5" th:switch="$reviews"
th:each="review : $reviews">
<div class="row">
<div class="col-lg-8 mx-auto">
<ul class="list-group shadow">
<li class="list-group-item">
<div class="media align-items-lg-center flex-column flex-lg-row p-3"
style="overflow: hidden; white-space: nowrap; text-overflow: ellipsis;">
<div class="media-body order-2 order-lg-1">
<form th:action="@|/$review.id|" method="get">
<button type="submit" th:text="$review.title"
style="color: #100029; text-decoration: none; font-size: 25px; background:none; border: none; margin: 0; padding: 0; cursor: pointer;"></button>
</form>
这是模板的一部分：
<div class="profile-card">
<div class="text-center profile-back"
style="background-color: rgba(255, 199, 0, 0); width: 70%; margin-top: 10%; margin-left: 15%; height: 100px;"></div>
<h2 class="border rounded profile-name"
style="background-color: #ffc700; color: #100029; width: 432px;" th:text="$reviews.title"></h2>
<p class="border rounded profile-bio"
style="background-color: #ffffff; color: #100029; margin-left: 15%; width: 70%;" th:text="$reviews.content"></p>
<div></div>
</div>
Review 实体的一部分（其余只是 constr、getter 和 setter）：
@Id
@GeneratedValue(strategy = GenerationType.AUTO)
private Integer id;
@NotEmpty(message="All fields must be completed!")
@Column(name = "title")
private String title;
@NotEmpty(message="All fields must be completed!")
@Column(name = "content")
private String content;
@NotNull(message="All fields must be completed!")
@Column(name = "score")
private Integer score;
@NotEmpty(message="All fields must be completed!")
@Column(name = "restaurant")
private String restaurant;
这里是仓库，不知道好不好用：
@Repository
public interface ReviewRepository extends CrudRepository <Review, Integer>
Optional<Review> findById(Integer id);
这是我遇到的错误：
There was an unexpected error (type=Internal Server Error, status=500).
An error happened during template parsing (template: "class path resource [templates/index-specific.html]")
org.thymeleaf.exceptions.TemplateInputException: An error happened during template parsing (template: "class path resource [templates/index-specific.html]")
at org.thymeleaf.templateparser.markup.AbstractMarkupTemplateParser.parse(AbstractMarkupTemplateParser.java:241)
at org.thymeleaf.templateparser.markup.AbstractMarkupTemplateParser.parseStandalone(AbstractMarkupTemplateParser.java:100)
at org.thymeleaf.engine.TemplateManager.parseAndProcess(TemplateManager.java:666)
at org.thymeleaf.TemplateEngine.process(TemplateEngine.java:1098)
at org.thymeleaf.TemplateEngine.process(TemplateEngine.java:1072)
at org.thymeleaf.spring5.view.ThymeleafView.renderFragment(ThymeleafView.java:362)
at org.thymeleaf.spring5.view.ThymeleafView.render(ThymeleafView.java:189)
at org.springframework.web.servlet.DispatcherServlet.render(DispatcherServlet.java:1373)
at org.springframework.web.servlet.DispatcherServlet.processDispatchResult(DispatcherServlet.java:1118)
at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:1057)
at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:943)
at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:1006)
at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:898)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:634)
at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:883)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:741)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:231)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:53)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
at org.springframework.web.filter.RequestContextFilter.doFilterInternal(RequestContextFilter.java:100)
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
at org.springframework.web.filter.FormContentFilter.doFilterInternal(FormContentFilter.java:93)
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:201)
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:202)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:96)
at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:541)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:139)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:92)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:74)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:343)
at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:373)
at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:65)
at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:868)
at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1590)
at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49)
at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
at java.lang.Thread.run(Unknown Source)
Caused by: org.attoparser.ParseException: Exception evaluating SpringEL expression: "reviews.title" (template: "index-specific" - line 23, col 69)
at org.attoparser.MarkupParser.parseDocument(MarkupParser.java:393)
at org.attoparser.MarkupParser.parse(MarkupParser.java:257)
at org.thymeleaf.templateparser.markup.AbstractMarkupTemplateParser.parse(AbstractMarkupTemplateParser.java:230)
... 48 more
Caused by: org.thymeleaf.exceptions.TemplateProcessingException: Exception evaluating SpringEL expression: "reviews.title" (template: "index-specific" - line 23, col 69)
at org.thymeleaf.spring5.expression.SPELVariableExpressionEvaluator.evaluate(SPELVariableExpressionEvaluator.java:290)
at org.thymeleaf.standard.expression.VariableExpression.executeVariableExpression(VariableExpression.java:166)
at org.thymeleaf.standard.expression.SimpleExpression.executeSimple(SimpleExpression.java:66)
at org.thymeleaf.standard.expression.Expression.execute(Expression.java:109)
at org.thymeleaf.standard.expression.Expression.execute(Expression.java:138)
at org.thymeleaf.standard.processor.AbstractStandardExpressionAttributeTagProcessor.doProcess(AbstractStandardExpressionAttributeTagProcessor.java:144)
at org.thymeleaf.processor.element.AbstractAttributeTagProcessor.doProcess(AbstractAttributeTagProcessor.java:74)
at org.thymeleaf.processor.element.AbstractElementTagProcessor.process(AbstractElementTagProcessor.java:95)
at org.thymeleaf.util.ProcessorConfigurationUtils$ElementTagProcessorWrapper.process(ProcessorConfigurationUtils.java:633)
at org.thymeleaf.engine.ProcessorTemplateHandler.handleOpenElement(ProcessorTemplateHandler.java:1314)
at org.thymeleaf.engine.OpenElementTag.beHandled(OpenElementTag.java:205)
at org.thymeleaf.engine.Model.process(Model.java:282)
at org.thymeleaf.engine.Model.process(Model.java:290)
at org.thymeleaf.engine.IteratedGatheringModelProcessable.processIterationModel(IteratedGatheringModelProcessable.java:367)
at org.thymeleaf.engine.IteratedGatheringModelProcessable.process(IteratedGatheringModelProcessable.java:221)
at org.thymeleaf.engine.ProcessorTemplateHandler.handleCloseElement(ProcessorTemplateHandler.java:1640)
at org.thymeleaf.engine.TemplateHandlerAdapterMarkupHandler.handleCloseElementEnd(TemplateHandlerAdapterMarkupHandler.java:388)
at org.thymeleaf.templateparser.markup.InlinedOutputExpressionMarkupHandler$InlineMarkupAdapterPreProcessorHandler.handleCloseElementEnd(InlinedOutputExpressionMarkupHandler.java:322)
at org.thymeleaf.standard.inline.OutputExpressionInlinePreProcessorHandler.handleCloseElementEnd(OutputExpressionInlinePreProcessorHandler.java:220)
at org.thymeleaf.templateparser.markup.InlinedOutputExpressionMarkupHandler.handleCloseElementEnd(InlinedOutputExpressionMarkupHandler.java:164)
at org.attoparser.HtmlElement.handleCloseElementEnd(HtmlElement.java:169)
at org.attoparser.HtmlMarkupHandler.handleCloseElementEnd(HtmlMarkupHandler.java:412)
at org.attoparser.MarkupEventProcessorHandler.handleCloseElementEnd(MarkupEventProcessorHandler.java:473)
at org.attoparser.ParsingElementMarkupUtil.parseCloseElement(ParsingElementMarkupUtil.java:201)
at org.attoparser.MarkupParser.parseBuffer(MarkupParser.java:725)
at org.attoparser.MarkupParser.parseDocument(MarkupParser.java:301)
... 50 more
Caused by: org.springframework.expression.spel.SpelEvaluationException: EL1008E: Property or field 'title' cannot be found on object of type 'java.util.Optional' - maybe not public or not valid?
at org.springframework.expression.spel.ast.PropertyOrFieldReference.readProperty(PropertyOrFieldReference.java:217)
at org.springframework.expression.spel.ast.PropertyOrFieldReference.getValueInternal(PropertyOrFieldReference.java:104)
at org.springframework.expression.spel.ast.PropertyOrFieldReference.access$000(PropertyOrFieldReference.java:51)
at org.springframework.expression.spel.ast.PropertyOrFieldReference$AccessorLValue.getValue(PropertyOrFieldReference.java:406)
at org.springframework.expression.spel.ast.CompoundExpression.getValueInternal(CompoundExpression.java:92)
at org.springframework.expression.spel.ast.SpelNodeImpl.getValue(SpelNodeImpl.java:112)
at org.springframework.expression.spel.standard.SpelExpression.getValue(SpelExpression.java:337)
at org.thymeleaf.spring5.expression.SPELVariableExpressionEvaluator.evaluate(SPELVariableExpressionEvaluator.java:263)
... 75 more
有人可以帮帮我吗？我对此很陌生，我不知道我在这里做什么。 至少它向我展示了那里的好身份......
the url when pressed on a title
【问题讨论】：
【参考方案1】：您将Optional 对象传递给模型，但我需要传递确切的值对象。
试试这个：
rev.ifPresent(reviewsValue -> model.addAttribute("reviews", reviewsValue))
另外，您需要记住rev 为空时的回退操作。
例如if (rev.isEmpty()) return "empty-index"
【讨论】：
非常感谢，我开始失去希望我能完成这个！ @RaluckxY 没问题 :)以上是关于从视图获取值到控制器，然后到另一个视图的主要内容，如果未能解决你的问题，请参考以下文章