java 如何使用@ModelAttribute 将列表绑定到 JSP 表单中的控制器
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How to bind a List using @ModelAttribute to controller from a JSP form
提问by saran
I am trying to get a list of selected candidates to my controller using @modelAttribute with their respective id and blurb. I am able to bring one Candidate correctly but i don't know how to bring a list of candidates thru... I tried to add List<> as i have shown below, but i get
我正在尝试使用 @modelAttribute 及其各自的 id 和 blurb 将选定候选者的列表添加到我的控制器中。我能够正确地带一名候选人，但我不知道如何通过...带上候选人名单...我尝试添加 List<>，如下所示，但我得到了
ERROR - SEVERE: Servlet.service() for servlet [dispatcher] in context with path [/panel-requests] threw exception [Request processing failed; nested exception is org.springframework.beans.BeanInstantiationException: Could not instantiate bean class [java.util.List]: Specified class is an interface] with root cause org.springframework.beans.BeanInstantiationException: Could not instantiate bean class [java.util.List]: Specified class is an interface
错误 - 严重：servlet [dispatcher] 的 Servlet.service() 在路径 [/panel-requests] 的上下文中抛出异常 [请求处理失败；嵌套异常是 org.springframework.beans.BeanInstantiationException：无法实例化 bean 类 [java.util.List]：指定的类是一个接口]，其根本原因是 org.springframework.beans.BeanInstantiationException：无法实例化 bean 类 [java.util .List]：指定的类是一个接口
JSP -
JSP -
<form:form modelAttribute="candidateAddAttribute"
action="/panel-requests/requests/${panelRequestForId.id}/empl" method="post">
<c:forEach items="${candidates}" var="candidates">
<select name="employee" id="employee" disabled="disabled">
<option value="default" selected="selected">${candidates.candidateName}</option>
</select>
<textarea rows="3" cols="40" id="candidateBlurb" name="candidateBlurb"
disabled="disabled">${candidates.candidateBlurb}</textarea>
<textarea rows="2" cols="20" id="candidateCV" name="candidateCV"
disabled="disabled">${candidates.candidateCV}</textarea>
</c:forEach>
<div id="candidateDiv" id="candidateDiv">
<select name="employee" id="employee">
<option value="default" selected="selected">Select Employee</option>
<c:forEach items="${employees}" var="employee">
<option value="${employee.id}" id="${employee.id}">
${employee.employeeName}- ${employee.employeeCV}<
/option>
</c:forEach>
</select>
<textarea rows="3" cols="40" id="candidateBlurb"
name="candidateBlurb">BLURB</textarea>
<div id="employeeCv"></div>
<input type="submit" value="Add Candidate" />
</div>
</form:form>
The above form at first displays list of employee and when user selects employee, enters blurb and hits add candidate button, i take data to controller.
上面的表单首先显示员工列表，当用户选择员工，输入简介并点击添加候选按钮时，我将数据带到控制器。
Controller:
控制器：
@RequestMapping(value = "{id}/empl", method = RequestMethod.POST)
public String getEmployeeDetails(
@ModelAttribute("candidateAddAttribute") @Valid List<Candidate> candidates,
BindingResult result, @PathVariable("id") int requestId, Model model) {
//implementation goes here
}
How do I implement List in this case? Thanks in advance.
在这种情况下如何实现 List ？提前致谢。
EDITED PARTI tried sending 2 candidate's details, firebug sends it correctly like - Parameters candidateBlurb BLURB sar candidateBlurb BLURB dann employee 1 employee 2
编辑部分我尝试发送 2 个候选人的详细信息，firebug 正确发送它，如 - 参数CandidateBlurb BLURB sarCandidateBlurb BLURB dann员工1员工2
so it can be a problem in initBinder that i ma using, binder.registerCustomEditor(Employee.class, new PropertyEditorSupport() { public String getAsText() { return Long.toString(((Employee) getValue()).getId()); }
所以它可能是我使用的 initBinder 中的一个问题， binder.registerCustomEditor(Employee.class, new PropertyEditorSupport() { public String getAsText() { return Long.toString(((Employee) getValue()).getId()) ; }
public void setAsText(final String text) {
Employee employee = Employee.findById(Integer
.parseInt(text));
setValue(employee);
}
});
which only takes 1 employee detail at a time. Is that a problem here???
一次只需要 1 个员工详细信息。这里有问题吗？？？
回答by matt b
Create a POJO class which contains the List as a property, such as
创建一个包含 List 作为属性的 POJO 类，例如
public class EmployeeForm {
private List<Candidate> candidates;
public List<Candidate> getCandidates() { ... }
public void setCandidates(List<Candidates>) { ... }
}
and use this in your @RequestMapping method's signature rather than a List<Candidate>directly.
并在您的 @RequestMapping 方法的签名中使用它而不是List<Candidate>直接使用它。
The error message you get is Spring complaining that it doesn't know how to instantiate a List interface, in order for Spring to bind the request parameters in the form to it. You want to provide a simple form/command class to data-bind the form parameters to, Spring knows how to handle a list from there.
您得到的错误消息是 Spring 抱怨它不知道如何实例化 List 接口，以便 Spring 将表单中的请求参数绑定到它。您想提供一个简单的表单/命令类来将表单参数数据绑定到，Spring 知道如何从那里处理列表。
回答by wangjin
you can try this :
你可以试试这个：
List<Candidate> candidates = ListUtils.lazyList(new ArrayList<Candidate>(),FactoryUtils.instantiateFactory(Candidate.class));
回答by Trevor
I've run into this same issue, half of the fields are binding correctly and half aren't. I noticed that the half that are not binding correctly (thus giving me NULL in the controller) were wrapped in a DIV.
我遇到了同样的问题，一半的字段绑定正确，另一半没有。我注意到没有正确绑定的一半（因此在控制器中给我 NULL）被包裹在一个 DIV 中。
When I moved these fields outside the DIV, bingo, they were bound properly in the controller.
当我将这些字段移到 DIV 之外时，宾果游戏，它们在控制器中正确绑定。
I see that you have some fields wrapped in a DIV too, I'd recommend moving them out and seeing if they become visible to your controller.
我看到您也有一些字段包含在 DIV 中，我建议将它们移出并查看它们是否对您的控制器可见。
