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Spring MVC预填充复选框

问题内容：

第一点背景信息。获得了相当标准的用户角色关系，其中用户可以具有多个角色。我在用户类中将角色定义为一组。现在，我知道html表单将所有值都作为字符串，并且尝试获取值，因为我的自定义Role对象不起作用。我实现了一个initbinder来将id的内容转换回对象，以便可以从复选框中检索所选的值，该部分可以工作。

但是我似乎无法回头。我从已经具有角色的数据库中检索一个用户，并希望使用该用户具有的所有角色来预先填充角色复选框。根据此示例：

复选框示例

他们说：

形式：复选框items =“ $ {dynamic-list}” path =“要存储的商品”

对于多个复选框，只要“路径”或“属性”值等于任何“复选框值– $ {dynamic-list}”，匹配的复选框将被自动选中。

我对此的解释是，我应该能够为它提供所有角色的集合，并从User对象定义角色为角色的路径，并且该路径应与它们匹配，从而使该复选框预先填充。

那里的每个示例似乎都具有dynamic-list作为String
[]的值。很好，太花哨了，但是这对于我们定义为Set的自定义对象如何起作用？我是否仍可以将这一行定义用于复选框，还是还需要在视图中进行某种数据绑定？

这是我的用户dto，用户控制器，自定义表单活页夹和用户编辑页面。

用户DTO

@Entity
@Table
public class User extends BaseDto
{
   @Column(updatable = false) @NotBlank
   private String username;

   @Column(name = "encrypted_password") @Size(min = 6, message = "password must be at least 6 characters") @Pattern(regexp = "^\\S*$", message = "invalid character detected")
   private String password;

   @Column(name = "first_name")
   private String firstName;

   @Column(name = "last_name")
   private String lastName;

   @Column @NotNull
   private boolean enabled;

   @Column @Email @NotBlank
   private String email;

   @Transient
   private String confirmPassword;

   @ManyToMany(targetEntity = Role.class, fetch = FetchType.EAGER, cascade = CascadeType.REFRESH) @JoinTable(name = "user_role", joinColumns = @JoinColumn(name = "user_id"),
      inverseJoinColumns = @JoinColumn(name = "role_id"))
   private Set<Role> roles;

   public User()
   {
   }

   public User(final String usernameIn, final String passwordIn, final String firstNameIn, final String lastNameIn, final String emailIn, final boolean enabledIn)
   {
      username = usernameIn;
      password = passwordIn;
      firstName = firstNameIn;
      lastName = lastNameIn;
      email = emailIn;
      enabled = enabledIn;
   }

   public String getUsername()
   {
      return username;
   }

   public void setUsername(final String usernameIn)
   {
      username = usernameIn;
   }

   public String getPassword()
   {
      return password;
   }

   public void setPassword(final String passwordIn)
   {
      password = passwordIn;
   }

   public String getFirstName()
   {
      return firstName;
   }

   public void setFirstName(final String firstNameIn)
   {
      firstName = firstNameIn;
   }

   public String getLastName()
   {
      return lastName;
   }

   public void setLastName(final String lastNameIn)
   {
      lastName = lastNameIn;
   }

   public String getEmail()
   {
      return email;
   }

   public void setEmail(final String emailIn)
   {
      email = emailIn;
   }

   public String getConfirmPassword()
   {
      return confirmPassword;
   }

   public void setConfirmPassword(final String confirmPasswordIn)
   {
      confirmPassword = confirmPasswordIn;
   }

   public boolean isEnabled()
   {
      return enabled;
   }

   public void setEnabled(final boolean enabledIn)
   {
      enabled = enabledIn;
   }

   public Set<Role> getRoles()
   {
      return roles;
   }

   public void setRoles(final Set<Role> rolesIn)
   {
      roles = rolesIn;
   }
}

用户控制器

@Controller @RequestMapping("/user")
public class UserController
{
   @Autowired private UserService userService;
   @Autowired private UserDao userDao;
   @Autowired private RoleDao roleDao;

   @InitBinder
   public void bindForm(final WebDataBinder binder)
   {
      binder.registerCustomEditor(Set.class, "roles", new CustomFormBinder<RoleDao>(roleDao, Set.class));
   }

   @RequestMapping(method = RequestMethod.GET)
   public String index(final ModelMap modelMap)
   {
      return "/user/index";
   }

   @RequestMapping(value = "/create", method = RequestMethod.GET)
   public String create(final ModelMap modelMap)
   {
      modelMap.addAttribute("userInstance", new User());
      modelMap.addAttribute("validRoles",  new HashSet<Role>(roleDao.findAll()));

      return "/user/create";
   }

   @RequestMapping(value = "/save", method = RequestMethod.POST)
   public String save(final ModelMap modelMap, @Valid @ModelAttribute("userInstance") final User user, final BindingResult bindingResult)
   {
      // TODO move to service validation
      if (user.getPassword() == null || !user.getPassword().equals(user.getConfirmPassword()) )
      {
         bindingResult.addError(new FieldError("userInstance", "password", "password fields must match"));
         bindingResult.addError(new FieldError("userInstance", "confirmPassword", "password fields must match"));
      }
      if (user.getRoles() == null || user.getRoles().isEmpty())
      {
         bindingResult.addError(new FieldError("userInstance", "roles", "Must select at least one role for a User"));
      }
      if (bindingResult.hasErrors())
      {
         modelMap.addAttribute("validRoles",  new HashSet<Role>(roleDao.findAll()));
         return "/user/create";
      }

      userService.save(user);
      return "redirect:/user/list";
   }

   @RequestMapping(value = "/edit/{id}", method = RequestMethod.GET)
   public String edit(@PathVariable final Integer id, final ModelMap modelMap)
   {
      final User user = userDao.find(id);

      if (user != null)
      {
         modelMap.addAttribute("userInstance", user);
         modelMap.addAttribute("validRoles",  new HashSet<Role>(roleDao.findAll()));
         return "/user/edit";
      }
      return "redirect:/user/list";
   }

   @RequestMapping(value = "/edit", method = RequestMethod.GET)
   public String editCurrent(final ModelMap modelMap)
   {
      return edit(userService.getLoggedInUser().getId(), modelMap);
   }

   @RequestMapping(value = "/update", method = RequestMethod.POST)
   public String update(@Valid @ModelAttribute("userInstance") final User user, final BindingResult bindingResult)
   {
      if (bindingResult.hasErrors())
      {
         return "/user/edit";
      }

      userService.save(user);
      return "redirect:/user/list";
   }

   @ModelAttribute("userInstances")
   @RequestMapping(value = "/list", method = RequestMethod.GET)
   public List<User> list()
   {
      return userDao.findAll();
   }
}

自定义表格活页夹

public class CustomFormBinder<T extends GenericDao> extends CustomCollectionEditor
{
   private final T dao;

   private static final Logger LOG = LoggerFactory.getLogger(CustomFormBinder.class);

   public CustomFormBinder(final T daoIn, final Class collectionType)
   {
      super(collectionType, true);
      dao = daoIn;
   }

   @Override
   protected Object convertElement(final Object element)
   {
      try
      {
         // forms should return the id as the itemValue
         return dao.find(Integer.valueOf(element.toString()));
      }
      catch (NumberFormatException e)
      {
         LOG.warn("Unable to convert " + element + " to an integer");
         return null;
      }
   }

}

用户编辑视图

    <html>
    <head>
        <title>Create User</title>
    </head>
    <body>

    <c:url value="/user/update" var="actionUrl"/>
    <form:form method="post" commandName="userInstance" action="${actionUrl}">
        <h1>Edit User ${userInstance.username}</h1>

        <div>
            <form:label path="username">Username:</form:label>
            <form:input path="username" id="username" readonly="true"/>
        </div>

        <div>
            <form:label path="password">Password:</form:label>
            <form:input path="password" id="password" type="password" readonly="true"/>
            <tag:errorlist path="userInstance.password" cssClass="formError"/>
        </div>

        <div>
            <form:label path="firstName">First Name:</form:label>
            <form:input path="firstName" id="firstName"/>
            <tag:errorlist path="userInstance.firstName" cssClass="formError"/>
        </div>

        <div>
            <form:label path="lastName">Last Name:</form:label>
            <form:input path="lastName" id="lastName"/>
            <tag:errorlist path="userInstance.lastName" cssClass="formError"/>
        </div>

        <div>
            <form:label path="email">Email:</form:label>
            <form:input path="email" id="email" size="30"/>
            <tag:errorlist path="userInstance.email" cssClass="formError"/>
        </div>

        <div>
         **<%--Want to Pre Populate these checkboxed--%>   
<form:checkboxes title="Assigned Roles:" path="roles" id="roles" items="${validRoles}" itemLabel="displayName" itemValue="id" element="div"/>**
            <tag:errorlist path="userInstance.roles" cssClass="formError"/>
        </div>

        <form:hidden path="enabled"/>
        <form:hidden path="id"/>
        <form:hidden path="version"/>

        <div class="submit">
            <input type="submit" value="Update"/>
            <a href="<c:url value='/user/list'/>" class="cancel">Cancel</a>
        </div>
    </form:form>

    </body>
    </html>

问题答案：

您需要正确的实现等于方法Role！

如果这还不够，请上课oorg.springframework.web.servlet.tags.form.AbstractCheckedElementTag。该方法void renderFromValue(Object item, Object value, TagWriter tagWriter)是设置检查标志的地方。