springMVC绑定参数时报错DefaultHandlerExceptionResolver解决办法

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")@ResponseBodypublic 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;}

因为User类中包含Set成员，由于Hibernate的延迟加载，所以在业务层吧roles置为null了。

所以list方法的返回结果如下：

[{"id":1,"username":"admin","password":"admin","realName":"张三","email":"[e-mail]","phone":"23423234","roles":null},{"id":2,"username":"erwt","password":"admin","realName":"张三","email":"[e-mail]","phone":"3423432432","roles":null}]

前台用easyui的datagrid控件显示和编辑数据：

<table id="dg" title="用户列表" 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'">用户名</th><!-- 如果field 值easyui datagrid找不到的话，它会使用formatter的规则来绑定数据； --><th field="password"  width="100" editor="text" hidden="true">登录密码</th><th field="realName"  width="100" editor="text" align="center">真实姓名</th><th field="email" width="160" align="center" editor="text">邮箱</th><th field="phone" data-options="align:'left', halign: 'center'"width="100" editor="text" >联系电话</th></tr></thead></table>

这样编辑easyui的表格数据后保存，报异常

 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]

解决方案：

之前一直以为是springMVC的参数绑定功能和easyui的表格数据编辑功能不兼容，于是就去看源码，希望找到根本原因，弄的头都大了，还是找到原因。后来把roles置null改为roles.clear().居然能正常更新编辑了。

UserService.java

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

修改后list返回结果：

[{"id":1,"username":"admin","password":"admin","realName":"张三","email":"[e-mail]","phone":"23423234","roles":[]},

{"id":2,"username":"erwt","password":"admin","realName":"张三","email":"[e-mail]","phone":"3423432432","roles":[]}]