Spring WebMVC的标记库：form：checkboxes按预期工作，而迭代覆盖form：checkbox则不然

Question

简介

为具有相关列表的@Entity创建表单时，我遇到了一个奇怪的行为。 <form:checkboxes/>和生成多个<form:checkbox/>的列表上的迭代行为不同，但不应该从我的角度出发。

代码

我删除了对我来说似乎没有必要的所有内容，但随时可以询问是否缺少任何代码。

模型

我的角色和权利模型更简单（或者有些人可能会说是贫血）。

角色的实体：

@Entity
public class Role implements Serializable{

/* Setters and Getters and some annotations omitted for readability
 * Some annotations too. Unittests for the relations have no error so far.
 */

  @Id
  @GeneratedValue(strategy=GenerationType.AUTO)
  private Long id;

  @Version
  private Date lastModified;

  @ManyToMany(cascade={CascadeType.PERSIST,CascadeType.MERGE},fetch=FetchType.EAGER)
  private List<Right> rights = new ArrayList<Right>();
}

对于右：

@Entity
public class Right implements GrantedAuthority,Serializable{

  @Id
  @GeneratedValue(strategy=GenerationType.AUTO)
  private Long id;

  @Version
  @Temporal(TemporalType.TIMESTAMP)
  private Date lastModified;

  @ManyToMany(mappedBy="rights")
  private List<Role> roles;

}

表格

现在显然我想为我的角色添加权限。这是我的应用程序中的动态过程，因此有一个表单。有关详细信息，请参阅代码中的注释。

<form:form commandName="role">
    <p>
        <form:label path="name">Role Name</form:label><br/>
        <form:input path="name" cssClass="form-control"/>
    </p>
    <p>
        <form:label path="description">Description of role</form:label><br/>
        <form:textarea path="description" rows="3" class="form-control"></form:textarea>
    </p>
    <p>
        <%-- Now for whatever reason this (form:checkboxes) works as expected: --%>
        <%-- * Transfers correct values to the controller --%>
        <%-- * Is correctly checked and unchecked when the controller returns the page --%> 
        <form:checkboxes items="${allRights}" path="rights" itemLabel="name" itemValue="id" delimiter=" - "/>

        <%-- This does not work: --%>
        <%-- * The values are sent to the controller --%>
        <%-- * My CustomCollectionsEditor resolves the to the according rights --%>
        <%-- * Once the method returns, the values simply dissapear --%>
        <%--    <c:forEach items="${allRights}" var="right"> --%>
        <%--        <form:checkbox path="rights"  value="${right.id}" />${right.name} --%>
        <%--    </c:forEach> --%>
    </p>
    <p><button type="submit">Create new role</button></p>

</form:form>

控制器

我的@Controller只是创建表单并将其发送回来：

/* Makes allRights available in every page */
/* rightService.getRights() WAS an eternally cached method (memory only) 
 * but I deactivated caching when I ran into these problems
 */ 
@ModelAttribute("allRights")
public List<Right> populateRights() {
  _logger.debug("allRights:{}",rightService.getRights());
  return rightService.getRights();
}

@RequestMapping(value = "/add", method = RequestMethod.GET)
public ModelAndView addRoleView(ModelMap model) {
  model.addAttribute("role", new Role());
  return new ModelAndView("admin/roles/add", model);
}

@RequestMapping(value = "/add", method = RequestMethod.POST)
public ModelAndView addRole(@ModelAttribute("role") Role role,
            BindingResult result , ModelMap model) {

  /* Logs the selected rights and does so for both methods */
  _logger.debug("Role's Rights:{}",role.getRights());

  return new ModelAndView("admin/roles/add",model);
}
/* @InitBinder omitted for readability, as it is obviously working since both
 * ways actually send the data to the Controller method.
 */

问题

1. 表单的行为与我的代码一起可以预期吗？
2. 如果是的话：为什么我在这里失踪了什么？
3. 如果不是：除了完全手工处理表格外，您是否看到了其他工作？

谢谢...

...花时间阅读这个问题和答案！

Answer 1

实际上，这是我的错（正如所料）。

为了能够以这种方式使用相关字段，需要实现相应的@InitBinder或Formatter。

请参阅the according thread in Thymeleaf's user forum for details.