public class User { int id; String username; String password; String realName; String email; String phone; Set<Role> roles;}

UserAction.java

<span style="white-space:pre"
 
> </span>@RequestMapping(value = "list") @ResponseBody public List list(@RequestParam Map map) {  List<User> list = userService.list(map);  return list; }

<span style="white-space:pre"> </span>@RequestMapping(value = "update")<span style="white-space:pre"
 
> </span>@ResponseBody<span style="white-space:pre"> </span>public User update(User user) {<span style="white-space:pre">  </span>userService.update(user);<span style="white-space:pre">  </span>return user;<span style="white-space:pre"
 
> </span>}

UserService.java

<span style="white-space:pre"> </span>public List<User> list(Map map) {  List<User> list = userDAO.list(map);  for (User user : list) {   user.setRoles(null);  }  return list; }

所以list方法的返回結果如下：

[{"id":1,"username":"admin","password":"admin","realName":"張三","email":"[email protected]","phone":"23423234","roles":null},{"id":2,"username":"erwt","password":"admin","realName":"張三","email":"[email protected]","phone":"3423432432","roles":null}]

前臺用easyui的datagrid控制元件顯示和編輯資料：

<table id="dg" title="使用者列表" class="easyui-datagrid" style="width:100%;height:auto;margin:0 auto;"   data-options=""  idField="id"  rownumbers="true" fitColumns="true" singleSelect="true">  <thead>   <tr >    <th field="id" width="60" data-options="align:'center', halign: 'center'">id</th>    <th field="username" width="100" editor="text" data-options="align:'left', halign: 'center'">使用者名稱</th> <!--    如果field 值easyui datagrid找不到的話，它會使用formatter的規則來繫結資料； -->    <th field="password"  width="100" editor="text" hidden="true">登入密碼</th>    <th field="realName"  width="100" editor="text" align="center">真實姓名</th>    <th field="email" width="160" align="center" editor="text">郵箱</th>    <th field="phone" data-options="align:'left', halign: 'center'"     width="100" editor="text" >聯絡電話</th>   </tr>  </thead> </table>

 WARN DefaultHandlerExceptionResolver:189 - Handler execution resulted in exception: org.springframework.validation.BeanPropertyBindingResult: 1 errorsField error in object 'user' on field 'roles': rejected value []; codes [typeMismatch.user.roles,typeMismatch.roles,typeMismatch.java.util.Set,typeMismatch]; arguments [org.springframework.context.support.DefaultMessageSourceResolvable: codes [user.roles,roles]; arguments []; default message [roles]]; default message [Failed to convert property value of type 'java.lang.String' to required type 'java.util.Set' for property 'roles'; nested exception is java.lang.IllegalStateException: Cannot convert value of type [java.lang.String] to required type [com.pelin.webapp.ms.entity.Role] for property 'roles[0]': no matching editors or conversion strategy found]

解決方案：

之前一直以為是springMVC的引數繫結功能和easyui的表格資料編輯功能不相容，於是就去看原始碼，希望找到根本原因，弄的頭都大了，還是找到原因。後來把roles置null改為roles.clear().居然能正常更新編輯了。

UserService.java

public List<User> list(Map map) {  List<User> list = userDAO.list(map);  for (User user : list) {   user.getRoles().clear();  }  return list; }

修改後list返回結果：

[{"id":1,"username":"admin","password":"admin","realName":"張三","email":"[email protected]","phone":"23423234","roles":[]},

{"id":2,"username":"erwt","password":"admin","realName":"張三","email":"[email protected]","phone":"3423432432","roles":[]}]

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