spring-mvc - Spring/Thymeleaf 在处理@PostMapping 时抛出 "Cannot create a session after the response has been committed"

Question

我使用 thymeleaf View 构建了一个 Spring MVC 应用程序并遇到了以下问题。我有一个页面，它应该处理一个表单并创建一个新的实体来保存在数据库中。在我的 Controller 类中，我有两种方法。首先，@GetMapping 来渲染页面:

@GetMapping("/dispo/orderCreate")
private String showCreateOrder(Model model) {
    List<MdUser> userList = service.getUsers();
    model.addAttribute("userList", userList);

    return "/dispo/orderCreate";
}

至于我只想显示页面而不向表单添加一些操作，一切正常。模型属性“userList”正确填充了数据库中的用户。

现在我更改了 View 以向表单添加一个操作和一个对象。 View 的代码现在看起来像这样:

<form action="#" class="form" id="newOrderForm" th:action="@{/dispo/addOrder}" th:object="${loadOrder}" method="post">
<table class="cont-table" cellpadding="2" cellspacing="2" width="100%">
    <tbody>
        <tr align="left">
            <th align="left" valign="top" width="110">Protokollführer:</th>
                <td>
                    <table border="0" cellpadding="0" cellspacing="1" width="100%">
                        <tbody>
                            <tr>
                                <td height="30">
                                    <select class="selectOneMenue" id="newOrderPersoDropDown" th:field="*{supervisor}">
                                        <option>Bitte auswählen</option>
                                        <option th:each="user : ${userList}"
                                                th:value="user.userId"
                                                th:text="${user.firstName}+' '+${user.lastName}"></option>
                                    </select>
                                </td>
                                    . . .
            </tr>
        </tbody>
    </table>
    <br />
    <input style="width:200px" type="submit" value="Speichern" class="commandExButton" id="newOrderSubmit" />
    <input style="width:120px" type="reset" value="Zurücksetzen" class="commandExButton" id="newOrderReset" />
</form>

对应的@PostMapping 如下所示:

@PostMapping("/dispo/addOrder")
public String submit(@ModelAttribute("loadOrder") LoadOrderModel loadOrder, BindingResult result, Model model) {
    if (result.hasErrors()) {
        return "error";
    }

    service.createAndSaveLoadOrder(loadOrder);
    return "/dispo/success";
}

现在，当使用以下堆栈跟踪到达表单时， View 的呈现会崩溃:

Caused by: org.thymeleaf.exceptions.TemplateProcessingException: Error during execution of processor 'org.thymeleaf.spring5.processor.SpringActionTagProcessor' (template: "/dispo/orderCreate" - line 41, col 58)
at org.thymeleaf.processor.element.AbstractAttributeTagProcessor.doProcess(AbstractAttributeTagProcessor.java:117) ~[thymeleaf-3.0.9.RELEASE.jar:3.0.9.RELEASE]
at org.thymeleaf.processor.element.AbstractElementTagProcessor.process(AbstractElementTagProcessor.java:95) ~[thymeleaf-3.0.9.RELEASE.jar:3.0.9.RELEASE]
at org.thymeleaf.util.ProcessorConfigurationUtils$ElementTagProcessorWrapper.process(ProcessorConfigurationUtils.java:633) ~[thymeleaf-3.0.9.RELEASE.jar:3.0.9.RELEASE]
at org.thymeleaf.engine.ProcessorTemplateHandler.handleOpenElement(ProcessorTemplateHandler.java:1314) ~[thymeleaf-3.0.9.RELEASE.jar:3.0.9.RELEASE]
at org.thymeleaf.engine.TemplateHandlerAdapterMarkupHandler.handleOpenElementEnd(TemplateHandlerAdapterMarkupHandler.java:304) ~[thymeleaf-3.0.9.RELEASE.jar:3.0.9.RELEASE]
at org.thymeleaf.templateparser.markup.InlinedOutputExpressionMarkupHandler$InlineMarkupAdapterPreProcessorHandler.handleOpenElementEnd(InlinedOutputExpressionMarkupHandler.java:278) ~[thymeleaf-3.0.9.RELEASE.jar:3.0.9.RELEASE]
at org.thymeleaf.standard.inline.OutputExpressionInlinePreProcessorHandler.handleOpenElementEnd(OutputExpressionInlinePreProcessorHandler.java:186) ~[thymeleaf-3.0.9.RELEASE.jar:3.0.9.RELEASE]
at org.thymeleaf.templateparser.markup.InlinedOutputExpressionMarkupHandler.handleOpenElementEnd(InlinedOutputExpressionMarkupHandler.java:124) ~[thymeleaf-3.0.9.RELEASE.jar:3.0.9.RELEASE]
at org.attoparser.HtmlElement.handleOpenElementEnd(HtmlElement.java:109) ~[attoparser-2.0.4.RELEASE.jar:2.0.4.RELEASE]
at org.attoparser.HtmlMarkupHandler.handleOpenElementEnd(HtmlMarkupHandler.java:297) ~[attoparser-2.0.4.RELEASE.jar:2.0.4.RELEASE]
at org.attoparser.MarkupEventProcessorHandler.handleOpenElementEnd(MarkupEventProcessorHandler.java:402) ~[attoparser-2.0.4.RELEASE.jar:2.0.4.RELEASE]
at org.attoparser.ParsingElementMarkupUtil.parseOpenElement(ParsingElementMarkupUtil.java:159) ~[attoparser-2.0.4.RELEASE.jar:2.0.4.RELEASE]
at org.attoparser.MarkupParser.parseBuffer(MarkupParser.java:710) ~[attoparser-2.0.4.RELEASE.jar:2.0.4.RELEASE]
at org.attoparser.MarkupParser.parseDocument(MarkupParser.java:301) ~[attoparser-2.0.4.RELEASE.jar:2.0.4.RELEASE]
... 87 common frames omitted
Caused by: java.lang.IllegalStateException: Cannot create a session after the response has been committed
at org.apache.catalina.connector.Request.doGetSession(Request.java:3030) ~[tomcat-embed-core-8.5.34.jar:8.5.34]
at org.apache.catalina.connector.Request.getSession(Request.java:2468) ~[tomcat-embed-core-8.5.34.jar:8.5.34]
at org.apache.catalina.connector.RequestFacade.getSession(RequestFacade.java:896) ~[tomcat-embed-core-8.5.34.jar:8.5.34]
at org.apache.catalina.connector.RequestFacade.getSession(RequestFacade.java:908) ~[tomcat-embed-core-8.5.34.jar:8.5.34]
at javax.servlet.http.HttpServletRequestWrapper.getSession(HttpServletRequestWrapper.java:240) ~[tomcat-embed-core-8.5.34.jar:8.5.34]
at javax.servlet.http.HttpServletRequestWrapper.getSession(HttpServletRequestWrapper.java:240) ~[tomcat-embed-core-8.5.34.jar:8.5.34]
at org.springframework.security.web.csrf.HttpSessionCsrfTokenRepository.saveToken(HttpSessionCsrfTokenRepository.java:63) ~[spring-security-web-5.0.8.RELEASE.jar:5.0.8.RELEASE]
at org.springframework.security.web.csrf.LazyCsrfTokenRepository$SaveOnAccessCsrfToken.saveTokenIfNecessary(LazyCsrfTokenRepository.java:175) ~[spring-security-web-5.0.8.RELEASE.jar:5.0.8.RELEASE]
at org.springframework.security.web.csrf.LazyCsrfTokenRepository$SaveOnAccessCsrfToken.getToken(LazyCsrfTokenRepository.java:127) ~[spring-security-web-5.0.8.RELEASE.jar:5.0.8.RELEASE]
at org.springframework.security.web.servlet.support.csrf.CsrfRequestDataValueProcessor.getExtraHiddenFields(CsrfRequestDataValueProcessor.java:71) ~[spring-security-web-5.0.8.RELEASE.jar:5.0.8.RELEASE]
at org.thymeleaf.spring5.context.webmvc.SpringWebMvcThymeleafRequestDataValueProcessor.getExtraHiddenFields(SpringWebMvcThymeleafRequestDataValueProcessor.java:80) ~[thymeleaf-spring5-3.0.9.RELEASE.jar:3.0.9.RELEASE]
at org.thymeleaf.spring5.requestdata.RequestDataValueProcessorUtils.getExtraHiddenFields(RequestDataValueProcessorUtils.java:79) ~[thymeleaf-spring5-3.0.9.RELEASE.jar:3.0.9.RELEASE]
at org.thymeleaf.spring5.processor.SpringActionTagProcessor.doProcess(SpringActionTagProcessor.java:118) ~[thymeleaf-spring5-3.0.9.RELEASE.jar:3.0.9.RELEASE]
at org.thymeleaf.standard.processor.AbstractStandardExpressionAttributeTagProcessor.doProcess(AbstractStandardExpressionAttributeTagProcessor.java:142) ~[thymeleaf-3.0.9.RELEASE.jar:3.0.9.RELEASE]
at org.thymeleaf.processor.element.AbstractAttributeTagProcessor.doProcess(AbstractAttributeTagProcessor.java:74) ~[thymeleaf-3.0.9.RELEASE.jar:3.0.9.RELEASE]
... 100 common frames omitted

TemplateProcessingException 指示的第 41 行是带有表单标记的行。
我几乎没有前端开发经验，所以请耐心等待。我想我必须在这里做一些 http session 管理，但不知道该怎么做以及如何做。谁能帮我？

Answer 1

我终于做到了。问题确实出在 http session 中，或者更准确地说，出在 HttpSecurity 中。所以我在我的 SecurityConfig 类的配置方法中添加了以下内容:

http.sessionManagement()
        .sessionCreationPolicy(SessionCreationPolicy.ALWAYS)

我仍然需要找出 SessionCreationPolicy.ALWAYS 对我的应用程序的其余部分意味着什么，但现在它有效:D。