使用BindingResult 自定义错误信息

<mvc:annotation-driven />  

public class SystemUser {  
    @Length(min = 5, max = 20, message = "用户名长度必须位于5到20之间")  
    private String userName;   
    @Email(message = "比如输入正确的邮箱")  
    private String email;  
}  

@RequestMapping(value = "/create.html", method = RequestMethod.POST)  
public String doCreateUser(  
        @Valid @ModelAttribute("userDetail") SystemUser user,  
        BindingResult bindingResult,  
        HttpServletRequest request) {  
    // 如果有校验错误，返回添加用户的页面  
    if (bindingResult.hasErrors()) {  
        return "/user/create";  
    }        
    this.userService.createUser(user);  
    return "/user/list.html";  
}  

@RequestMapping(value = "/user/create.html", method = RequestMethod.POST)  
public String doCreateUser(  
        @Valid @ModelAttribute("userDetail") SystemUser user,  
        BindingResult bindingResult,  
        HttpServletRequest request) {  
    // 如果有数据校验错误，返回添加用户的页面  
    if (bindingResult.hasErrors()) {  
        return "/user/create";  
    }    
    boolean isUserNameExist = this.userService.checkUserByUserName(user.getUserName());  
    // 如果用户名已存在，返回添加用户的页面  
    if (isUserNameExist) {  
        // 向BindingResult添加用户已存在的校验错误  
        bindingResult.rejectValue("userName", "该用户名已存在", "该用户名已存在");  
        return "/user/create";  
    }        
    this.userService.createUser(user);  
    return "/user/list.html";  
}

<%@ taglib prefix="form" uri="http://www.springframework.org/tags/form" %>  

<form:form commandName="userDetail"> 
<form:errors path="*" cssStyle="color:red"></form:errors> 
</form:form> 

<input type="text" name="userName" value="${userDetail.userName}" > 
<form:errors path="userDetail.userName" cssStyle="color:red"></form:errors> 
<input type="text" name="email" value="${userDetail.email}"> 
<form:errors path="userDetail.email" cssStyle="color:red"></form:errors> 

@RequestMapping(value = "/save", method = RequestMethod.POST)
public Object test(HttpServletRequest request, Model model, @Validated User user, BindingResult bindingResult)
throws Exception {
if (bindingResult.hasErrors()) {
return "user/save";
}
user.setVersion(0);
return new ModelAndView("redirect:/user/list");
}