Spring MVC和重定向（P/R/G）

Question

我試圖在我的Spring MVC應用程序中實現P/R/G（POST/Redirect/GET）模式，以避免重複的表單提交，而不是顯示一些成功的觀點（GET），我重定向到另一個URL（redirect:/essays/main/student/{studentId}/activity/add/existing），我需要通過完整的模型。對於org.springframework.web.servlet.view.RedirectView春天文檔說：

「查看重定向到一個絕對的，上下文相關，或當前請求相對URL，暴露所有的模型屬性作爲HTTP查詢參數。」

，所以我可以從請求檢索序列化對象，它正常工作與字符串，但如果我想在我的情況下，通過更復雜的對象，就像它不工作，夫婦（activityListcourseList對象列表，中，teacherList ）。

這是它是如何想的工作： 首先我告訴我的searchActivity視圖，這工作得很好：

@RequestMapping(value="/{studentId}/activity/search", method = RequestMethod.GET) 
public String getSearchActivity(@PathVariable Integer studentId, Model model) { 

    StudentActivityDTO studentActivityDTO = new StudentActivityDTO(); 
    Student student = studentService.get(studentId); 
    studentActivityDTO.setStudent(student); 
    model.addAttribute("studentActivityDTO", studentActivityDTO); 

    return "searchActivity"; 
} 

這是我searchActivity觀的重要組成部分：

<c:url var="studentUrl" value="/essays/main/student/${studentActivityDTO.student.studentId}/activity/search" /> 
<form:form modelAttribute="studentActivityDTO" id="myForm" method="POST" action="${studentUrl}"> 
... 
<label for="activityDescription">Eneter search string:</label> 
<input type="text" id="activityDescription" name="activityDescription"> 
<input type="submit" value="Submit" id="submit"/> 
... 
</form:form> 

然後我輸入一個搜索字符串（activityDescription）並提交我的表單以進行實際搜索（POST），除了最後一行代碼（重定向部分）之外，其也可以正常工作：

@RequestMapping(value="/{studentId}/activity/search", method = RequestMethod.POST) 
public String postSearchActivity(@PathVariable Integer studentId, 
     @RequestParam(value="activityDescription") String activityDescription, 
     @ModelAttribute("studentActivityDTO") StudentActivityDTO studentActivityDTO, 
     Model model) { 

    List<Activity> activityList = activityService.search(activityDescription); 
    model.addAttribute("activityList", activityList); 

    Student student = studentService.get(studentId); 
    studentActivityDTO.setStudent(student); 
    model.addAttribute("studentActivityDTO", studentActivityDTO); 
    model.addAttribute("activityDescription", activityDescription); 
    model.addAttribute("courseList", courseService.getAll()); 
    model.addAttribute("teacherList", teacherService.getAll()); 

    return "redirect:/essays/main/student/{studentId}/activity/add/existing"; 
    // return "addExistingActivity"; <-- If I use this it works fine! 
} 

現在我需要通過模型的一些控制器GET方法：

@RequestMapping(value="/{studentId}/activity/add/existing", method = RequestMethod.GET) 
public String getAddExistingActivity(@PathVariable Integer studentId, Model model) { 
    // some stuff 
    return "addExistingActivity"; 
} 

addExistingActivity觀的重要組成部分：

<c:url var="studentUrl" value="/essays/main/student/${studentActivityDTO.student.studentId}/activity/add/existing" /> 
<form:form modelAttribute="studentActivityDTO" id="myForm" method="POST" action="${studentUrl}"> 
... 
<label for="activityId">Activity Id:</label> 
<input type="text" id="activityId" name="activityId"> 
<input type="submit" id="submit" value="Submit"/> 

<c:if test="${!empty activityList}"> 
... 
</c:if> 
<c:if test="${empty activityList}"> 
    <div style="color: #ff0000">No results!</div> 
</c:if> 
... 
</form:form> 

但我的列表（activityList，courseList，teacherList）是不存在，我總是收到「沒有結果！」的信息。我只在我的堆棧跟蹤得到這樣的：

[DEBUG] [http-bio-8080-exec-7 08:32:44] (AbstractView.java:exposeModelAsRequestAttributes:373) Added model object 'studentId' of type [java.lang.Integer] to request in view with name 'addExistingActivity' 
[DEBUG] [http-bio-8080-exec-7 08:32:44] (AbstractView.java:exposeModelAsRequestAttributes:373) Added model object 'studentActivityDTO' of type [rs.ac.uns.tfzr.zpupin.dto.StudentActivityDTO] to request in view with name 'addExistingActivity' 
[DEBUG] [http-bio-8080-exec-7 08:32:44] (AbstractView.java:exposeModelAsRequestAttributes:373) Added model object 'org.springframework.validation.BindingResult.studentActivityDTO' of type [org.springframework.validation.BeanPropertyBindingResult] to request in view with name 'addExistingActivity' 

但是，如果使用的return "addExistingActivity"代替redirect:...一切工作正常，我有這個在我的堆棧跟蹤：

[DEBUG] [http-bio-8080-exec-6 07:42:25] (AbstractView.java:exposeModelAsRequestAttributes:373) Added model object 'studentId' of type [java.lang.Integer] to request in view with name 'addExistingActivity' 
[DEBUG] [http-bio-8080-exec-6 07:42:25] (AbstractView.java:exposeModelAsRequestAttributes:373) Added model object 'studentActivityDTO' of type [rs.ac.uns.tfzr.zpupin.dto.StudentActivityDTO] to request in view with name 'addExistingActivity' 
[DEBUG] [http-bio-8080-exec-6 07:42:25] (AbstractView.java:exposeModelAsRequestAttributes:373) Added model object 'org.springframework.validation.BindingResult.studentActivityDTO' of type [org.springframework.validation.BeanPropertyBindingResult] to request in view with name 'addExistingActivity' 
[DEBUG] [http-bio-8080-exec-6 07:42:25] (AbstractView.java:exposeModelAsRequestAttributes:373) Added model object 'activityList' of type [java.util.Collections$CheckedRandomAccessList] to request in view with name 'addExistingActivity' 
[DEBUG] [http-bio-8080-exec-6 07:42:25] (AbstractView.java:exposeModelAsRequestAttributes:373) Added model object 'activityDescription' of type [java.lang.String] to request in view with name 'addExistingActivity' 
[DEBUG] [http-bio-8080-exec-6 07:42:25] (AbstractView.java:exposeModelAsRequestAttributes:373) Added model object 'courseList' of type [java.util.Collections$CheckedRandomAccessList] to request in view with name 'addExistingActivity' 
[DEBUG] [http-bio-8080-exec-6 07:42:25] (AbstractView.java:exposeModelAsRequestAttributes:373) Added model object 'teacherList' of type [java.util.Collections$CheckedRandomAccessList] to request in view with name 'addExistingActivity' 

全部列出目前，佔！

我需要什麼樣的自定義實現才能使其工作？任何幫助都感激不盡！

此外，我知道我可以使用Flash屬性爲此，但不會消失後擊中F5？

Answer 1

RedirectView默認情況下將所有包含基元的原始模型屬性或集合公開爲HTTP查詢參數。這就是爲什麼，當你添加一個字符串作爲模型屬性時，它會被暴露，並且當你添加一個對象時 - 它不會。事實上，這就是RedirectView文檔當前所說的（Spring 4.0.1）：

...默認情況下，所有原始模型屬性（或其集合）都作爲HTTP查詢參數公開（假設它們尚未用作URI模板變量）...

所以其實下面的方法：

@RequestMapping(value = "post", method = RequestMethod.POST) 
public String post(@ModelAttribute PrgForm form, Model model) { 
    model.addAttribute("testString", "Some string"); 
    model.addAttribute("testCollection", Lists.newArrayList("Element 1", "Element 2")); 
    model.addAttribute("testObject", form); 
    return "redirect:/demo/get"; 
} 

將導致重定向到：demo/get?testString=Some+string&testCollection=Element+1&testCollection=Element+2

正如你所看到的，testObject不在查詢參數。

如果仔細查看RedirectView源代碼，您會發現有一種方法isEligibleProperty(String, Object)可確定給定的模型元素是否應作爲查詢屬性公開。

此方法的行爲可能會改變。所以，事實上，你可以實現自己的RedirectView如下：

private class CustomRedirectView extends RedirectView { 

    public CustomRedirectView(String url) { 
     super(url); 
    } 

    @Override 
    protected boolean isEligibleProperty(String key, Object value) { 
     if ("testObject".equals(key)) { 
      return true; 
     } else { 
      return super.isEligibleProperty(key, value); 
     } 
    } 

    @Override 
    protected void appendQueryProperties(StringBuilder targetUrl, Map<String, Object> model, String encodingScheme) throws UnsupportedEncodingException { 
     // do some stuff 
    } 
} 

而且從@Controller's方法返回它：

@RequestMapping(value = "post", method = RequestMethod.POST) 
public View post(@ModelAttribute PrgForm form, Model model) { 
    model.addAttribute("testString", "Some string"); 
    model.addAttribute("testCollection", Lists.newArrayList("Element 1", "Element 2")); 
    model.addAttribute("testObject", form); 
    return new CustomRedirectView("/demo/get"); 
} 

我以前從未做過這種實現的，所以我不知道如何它可以完全實現你需要支持的場景。我認爲儘管利用Flash屬性會更好。

我希望它有幫助。