基于Spring MVC的Web应用开发(12) - Form

本节介绍SpringMVC中的表单，demo演示访问一个表单提交页面，填写表单的内容后使用jQuery的Ajax提交表单，将返回的文本信息显示出来。

记得在Struts1中有个FormBean的东西封装表单内容，在SpringMVC中也有，只不过SpringMVC更松耦合，只要写一个POJO就可以了，而不需要继承框架关联的类，看一下这个FormBean（只列出了主要属性）：

public class FormBean {
	
	@NotEmpty
	private String name;
	
	@Min(21)
	private int age;

	@DateTimeFormat(iso=ISO.DATE)
	@Past
	private Date birthDate;

	@MaskFormat("(###) ###-####")
	private String phone;

	@NumberFormat(pattern="$###,###.00")
	private BigDecimal currency;

	@NumberFormat(style=Style.PERCENT)
	private BigDecimal percent;
	
	private InquiryType inquiry;
	
	private String inquiryDetails;
	
	private boolean subscribeNewsletter;
	
	private Map<String, String> additionalInfo;
...
}

 需要一个Controller，FormController：

package org.springframework.samples.mvc.form;

import javax.validation.Valid;

import org.springframework.mvc.extensions.ajax.AjaxUtils;
import org.springframework.stereotype.Controller;
import org.springframework.ui.Model;
import org.springframework.validation.BindingResult;
import org.springframework.web.bind.annotation.ModelAttribute;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.SessionAttributes;
import org.springframework.web.context.request.WebRequest;
import org.springframework.web.servlet.mvc.support.RedirectAttributes;

@Controller
@RequestMapping("/form")
@SessionAttributes("formBean")
public class FormController {

	// Invoked on every request

	@ModelAttribute
	public void ajaxAttribute(WebRequest request, Model model) {
		model.addAttribute("ajaxRequest", AjaxUtils.isAjaxRequest(request));
	}

	// Invoked initially to create the "form" attribute
	// Once created the "form" attribute comes from the HTTP session (see @SessionAttributes)

	@ModelAttribute("formBean")
	public FormBean createFormBean() {
		return new FormBean();
	}
	
	@RequestMapping(method=RequestMethod.GET)
	public void form() {
	}

	@RequestMapping(method=RequestMethod.POST)
	public String processSubmit(@Valid FormBean formBean, BindingResult result, 
								@ModelAttribute("ajaxRequest") boolean ajaxRequest, 
								Model model, RedirectAttributes redirectAttrs) {
		if (result.hasErrors()) {
			return null;
		}
		// Typically you would save to a db and clear the "form" attribute from the session 
		// via SessionStatus.setCompleted(). For the demo we leave it in the session.
		String message = "Form submitted successfully.  Bound " + formBean;
		// Success response handling
		if (ajaxRequest) {
			// prepare model for rendering success message in this request
			model.addAttribute("message", message);
			return null;
		} else {
			// store a success message for rendering on the next request after redirect
			// redirect back to the form to render the success message along with newly bound values
			redirectAttrs.addFlashAttribute("message", message);
			return "redirect:/form";			
		}
	}
	
}

 FormController只有一个@RequestMapping，通过GET，POST来区分是访问表单页面（GET），还是提交表单（POST）。在这个类中有：

@ModelAttribute("formBean")
	public FormBean createFormBean() {
		return new FormBean();
	}

 它表示访问"http://localhost:8080/web/form/"时，就初始化一个叫formBean名字的属性放在Model中。在类的开头有：

@SessionAttributes("formBean")

 它表示Model中的这个formBean在session的范围内有效，想一下，session是跟浏览器窗口关联的，窗口关闭，session就失效，所以每次打开一个新的表单页面都会生成一个新的formBean，另外填写完表单内容以POST方式提交后，formBean会根据提交的参数自动设置FormBean的值。

@ModelAttribute
	public void ajaxAttribute(WebRequest request, Model model) {
		model.addAttribute("ajaxRequest", AjaxUtils.isAjaxRequest(request));
	}

 该配置会导致每次访问"http://localhost:8080/web/form/"，都会设置一个ajaxRequest值（因为没有象formBean一样设置ajaxRequest的范围，默认的范围为Request级，每次请求都执行）。之前说过填好表单后通过jQuery的Ajax提交表单，通过这个配置，就知道请求是否是Ajax请求。

@RequestMapping(method=RequestMethod.GET)
	public void form() {
	}

访问"http://localhost:8080/web/form/"，返回到"webapp/WEB-INF/views/form.jsp"。

@RequestMapping(method=RequestMethod.POST)
	public String processSubmit(@Valid FormBean formBean, BindingResult result, 
								@ModelAttribute("ajaxRequest") boolean ajaxRequest, 
								Model model, RedirectAttributes redirectAttrs) {
		if (result.hasErrors()) {
			return null;
		}
		// Typically you would save to a db and clear the "form" attribute from the session 
		// via SessionStatus.setCompleted(). For the demo we leave it in the session.
		String message = "Form submitted successfully.  Bound " + formBean;
		// Success response handling
		if (ajaxRequest) {
			// prepare model for rendering success message in this request
			model.addAttribute("message", message);
			return null;
		} else {
			// store a success message for rendering on the next request after redirect
			// redirect back to the form to render the success message along with newly bound values
			redirectAttrs.addFlashAttribute("message", message);
			return "redirect:/form";			
		}
	}

processSubmit第一个参数formBean封装了页面提交的表单参数，注意到它前面有一个@Valid，因此有第二个参数BindingResult result， 该参数可以知道表单是否验证通过。第三个参数获取Model中的属性值"ajaxRequest"，在方法体中，判断ajaxRequest，如果是，将返回"webapp/WEB-INF/views/form.jsp"，如果不是，将它重定向到一个jsp，当然，这个条件在本例子中没有使用到。

最后看看非常复杂的form.jsp，该jsp使用了大量的SpringMVC的标签：

<%@ 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" %>
<%@ page session="false" %>
<c:if test="${!ajaxRequest}">
<html>
<head>
	<title>forms | mvc-showcase</title>
	<link href="<c:url value="/resources/form.css" />" rel="stylesheet"  type="text/css" />		
	<script type="text/javascript" src="<c:url value="/resources/jquery/1.6/jquery.js" />"></script>
</head>
<body>
</c:if>
	<div id="formsContent">
		<h2>Forms</h2>
		<p>
			See the <code>org.springframework.samples.mvc.form</code> package for the @Controller code	
		</p>
		<form:form id="form" method="post" modelAttribute="formBean" cssClass="cleanform">
			<div class="header">
		  		<h2>Form</h2>
		  		<c:if test="${not empty message}">
					<div id="message" class="success">${message}</div>	
		  		</c:if>
		  		<s:bind path="*">
		  			<c:if test="${status.error}">
				  		<div id="message" class="error">Form has errors</div>
		  			</c:if>
		  		</s:bind>
			</div>
		  	<fieldset>
		  		<legend>Personal Info</legend>
		  		<form:label path="name">
		  			Name <form:errors path="name" cssClass="error" />
		 		</form:label>
		  		<form:input path="name" />
	
		  		<form:label path="age">
		  			Age <form:errors path="age" cssClass="error" />
		 		</form:label>
		  		<form:input path="age" />
		  		
		  		<form:label path="birthDate">
		  			Birth Date (in form yyyy-mm-dd) <form:errors path="birthDate" cssClass="error" />
		 		</form:label>
		  		<form:input path="birthDate" />
		  		 
		  		<form:label path="phone">
		  			Phone (in form (###) ###-####) <form:errors path="phone" cssClass="error" />
		  		</form:label>
		  		<form:input path="phone" />
	
		  		<form:label path="currency">
		  			Currency (in form $#.##) <form:errors path="currency" cssClass="error" />
		  		</form:label>
		  		<form:input path="currency" />
	
		  		<form:label path="percent">
		  			Percentage (in form ##%) <form:errors path="percent" cssClass="error" />
		  		</form:label>
		  		<form:input path="percent" />
	
		  	</fieldset>
	
			<fieldset>
				<legend>Inquiry</legend>
				<form:label path="inquiry">
					Type (select one)
				</form:label>
				<form:select path="inquiry">
					<form:option value="comment">Comment</form:option>
					<form:option value="feedback">Feedback</form:option>
					<form:option value="suggestion">Suggestion</form:option>
				</form:select>
				
		  		<form:label path="inquiryDetails">
		  			Details
		  		</form:label>
		  		<form:textarea path="inquiryDetails" />
		  	</fieldset>
	
			<fieldset class="checkbox">
				<legend>Request Additional Info</legend>
				<label><form:checkbox path="additionalInfo[mvc]" value="true" />on Spring MVC</label>
				<label><form:checkbox path="additionalInfo[java]" value="true" />on Java (4-ever)</label>				
			</fieldset>
		  		  	
			<fieldset class="radio">
				<legend>Subscribe to Newsletter?</legend>
				<label><form:radiobutton path="subscribeNewsletter" value="true" />Yes</label>
				<label><form:radiobutton path="subscribeNewsletter" value="false" /> No</label>
			</fieldset>
	
			<p><button type="submit">Submit</button></p>
		</form:form>
		<script type="text/javascript">
			$(document).ready(function() {
				$("#form").submit(function() {  
					$.post($(this).attr("action"), $(this).serialize(), function(html) {
						$("#formsContent").replaceWith(html);
						$('html, body').animate({ scrollTop: $("#message").offset().top }, 500);
					});
					return false;  
				});			
			});
		</script>
	</div>
<c:if test="${!ajaxRequest}">
</body>
</html>
</c:if>