在提交表单之前，Spring MVC 3.x 中是否有一种简单的方法来显示表单错误消息（通过 JSR303 验证获得）？
考虑本文末尾的示例代码。
最终用户应该编辑初始数据已经无效的表单。
提交表单时会正确显示错误（POST 方法），但不会在初始表单显示时（GET 方法）。
是否有一种简单的方法可以在初始表单显示（GET 方法）上显示错误？（有没有办法为此目的重新使用 form:errors 标签？）
JSP查看form1.jsp：
<%@ page session="true" %>
<%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c" %>
<%@ taglib uri="http://www.springframework.org/tags" prefix="s" %>
<%@ taglib uri="http://www.springframework.org/tags/form" prefix="form" %>
<html><body>
<form:form commandName="form1" method="post">
<s:bind path="*">
<c:if test="${status.error}">
<div style="color: red;">There are errors:</div>
<form:errors /><br />
</c:if>
</s:bind>
<form:label path="field1" >Field1:</form:label>
<form:input path="field1" />
<form:errors path="field1" cssStyle="color: red;"/>
<br />
<form:label path="field2" >Field2:</form:label>
<form:input path="field2" />
<form:errors path="field2" cssStyle="color: red;"/>
<br />
<form:button name="submit">Ok</form:button>
</form:form>
</body></html>
控制器：
@Controller @SessionAttributes("form1")
public class Form1Controller {
@ModelAttribute("form1") public Form1Bean createForm1() { return new Form1Bean(); }
@RequestMapping(value = "/form1/edit", method = RequestMethod.GET)
public String getEdit(Model model) {
// here we pretend to get form1 from database, and store it in session.
// form1 in database may have invalid field values.
// Perform a JSR-303 validation here ?
// MAIN QUESTION: What's the easy way to add errors to model and display them ?
return "/form1";
}
@RequestMapping(value = "/form1/edit", method = RequestMethod.POST)
public String postEdit(@Valid @ModelAttribute("form1") Form1Bean form1, BindingResult result, Model model) {
if (result.hasErrors()) {
return "/form1";
} else {
return "redirect:/done";
}
}
}
支持豆：
public class Form1Bean {
@Size(min=4,max=10) private String field1; // getters and setters ommited for brevity
@Size(min=4,max=10) private String field2;
public Form1Bean() {
this.field1 = "bad"; this.field2="good"; // start with an invalid field1
}
//...
}
编辑：从@jb-nizet 解释答案后，这里是完整的控制器源代码：
@Controller @SessionAttributes("form1")
public class Form1Controller {
@Autowired org.springframework.validation.Validator validator;
@ModelAttribute("form1") public Form1Bean createForm1() { return new Form1Bean(); }
@RequestMapping(value = "/form1/edit", method = RequestMethod.GET)
public String getEdit(@ModelAttribute("form1") Form1Bean form1, Errors errors, Model model) {
// here we pretend to get form1 from database, and store it in session.
// form1 in database may have invalid field values.
validator.validate(form1, errors);
return "/form1";
}
@RequestMapping(value = "/form1/edit", method = RequestMethod.POST)
public String postEdit(@Valid @ModelAttribute("form1") Form1Bean form1, BindingResult result, Model model) {
if (result.hasErrors()) {
return "/form1";
} else {
return "redirect:/done";
}
}
}
做了一些测试，它似乎工作！比你@jb-nizet