ActionForm的Date处理问题
参考：http://jgj228.blog.163.com/blog/static/4520113220084279454245/
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基于Struts做应用程序开发的时候，对日期数据的处理，这个是最常见的，由于Struts默认是不支持自动将网页POST的数据自动转化成Date型数据，所以，很多程序员就直接在ActionForm当中直接使用String，然后在Action当中再进行字符串跟日期数据的处理。
那假如在ActionForm当中是使用Date类型呢？会出现什么问题？能用什么样的解决办法？我们先看一下在ActionForm当中会出现的问题先。
首先，我们先创建一个新的Struts工程，创建一个新的ActionForm，取名叫UserForm，UserForm的实现代码如下：
?程序代码package zizz.struts;import java.util.Date;
import org.apache.struts.action.ActionForm;
/**
* UserForm对应着提交页面的网页表单信息
* @author chen yuzhe
*
*/
public?class?UserForm extends ActionForm{
????/**
???? * serialVersionUID
???? */
????private?static?final?long?serialVersionUID?=?-742922986494711669L;
????private?int?id;
????
????private?String name;
????
????private?int?age;
????
????private?String loginId;
????
????private?Date birthday;
????public?int?getAge()?{
????????return?age;
????}
????public?void?setAge(int?age)?{
????????this.age?=?age;
????}
????public?Date getBirthday()?{
????????return?birthday;
????}
????public?void?setBirthday(Date birthday)?{
????????this.birthday?=?birthday;
????}
????public?int?getId()?{
????????return?id;
????}
????public?void?setId(int?id)?{
????????this.id?=?id;
????}
????public?String getLoginId()?{
????????return?loginId;
????}
????public?void?setLoginId(String loginId)?{
????????this.loginId?=?loginId;
????}
????public?String getName()?{
????????return?name;
????}
????public?void?setName(String name)?{
????????this.name?=?name;
????}
????
}
第二，编写user_form.jsp的表单页面，user_form.jsp的代码如下：
?程序代码<%@ page contentType="text/html; charset=GBK"%><%@ taglib uri="http://struts.apache.org/tags-html"?prefix="html"?%>
<!DOCTYPE html PUBLIC?"-//W3C//DTD HTML 4.01 Transitional//EN"?"http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type"?content="text/html; charset=GBK">
<title>用户信息表单</title>
</head>
<body>
????<div><strong>创建新用户</strong></div>
????<html:form action="/userSave">
????????<table width="50%"?border="1">
????????????<tr>
????????????????<td>编号</td>
????????????????<td><html:text property="id"/></td>
????????????</tr>????????????
????????????<tr>
????????????????<td>姓名</td>
????????????????<td><html:text property="name"?/></td>
????????????</tr>????????????
????????????<tr>
????????????????<td>登录号</td>
????????????????<td><html:text property="loginId"?/></td>
????????????</tr>????
????????????<tr>
????????????????<td>年龄</td>
????????????????<td><html:text property="age"?/></td>
????????????</tr>????????????????????
????????????<tr>
????????????????<td>生日</td>
????????????????<td><html:text property="birthday"?/></td>
????????????</tr>????????????
????????</table>
????????<hr>
????????<html:submit></html:submit>
????????<html:reset></html:reset>
????</html:form>
</body>
</html>
第三，配置struts-config.xml文件，struts-config.xml文件配置如下：
?程序代码<?xml version="1.0"?encoding="UTF-8"?><!DOCTYPE struts-config PUBLIC?"-//Apache Software Foundation//DTD Struts Configuration 1.2//EN""http://struts.apache.org/dtds/struts-config_1_2.dtd">
<struts-config>
??<data-sources?/>
??<form-beans>
??????<form-bean name="userForm"?type="zizz.struts.UserForm"></form-bean>
??</form-beans>
??<global-exceptions?/>
??<global-forwards?/>
??<action-mappings>
??????<action path="/userSave"?name="userForm"?validate="false"?scope="request"?type="zizz.struts.UserSaveAction"></action>
??</action-mappings>
??<message-resources parameter="zizz.struts.ApplicationResources"?/>
</struts-config>
第四步，发布该应用程序，浏览，并提交页面，如下图所示：
提交将会报以下的错误信息：
?程序代码exception?javax.servlet.ServletException: BeanUtils.populate
????org.apache.struts.util.RequestUtils.populate(RequestUtils.java:495)
????org.apache.struts.action.RequestProcessor.processPopulate(RequestProcessor.java:805)
????org.apache.struts.action.RequestProcessor.process(RequestProcessor.java:203)
????org.apache.struts.action.ActionServlet.process(ActionServlet.java:1194)
????org.apache.struts.action.ActionServlet.doPost(ActionServlet.java:432)
????javax.servlet.http.HttpServlet.service(HttpServlet.java:710)
????javax.servlet.http.HttpServlet.service(HttpServlet.java:803)
root cause?
java.lang.IllegalArgumentException: Cannot invoke zizz.struts.UserForm.setBirthday - argument type mismatch
????org.apache.commons.beanutils.PropertyUtilsBean.invokeMethod(PropertyUtilsBean.java:1778)
????org.apache.commons.beanutils.PropertyUtilsBean.setSimpleProperty(PropertyUtilsBean.java:1759)
????org.apache.commons.beanutils.PropertyUtilsBean.setNestedProperty(PropertyUtilsBean.java:1648)
????org.apache.commons.beanutils.PropertyUtilsBean.setProperty(PropertyUtilsBean.java:1677)
????org.apache.commons.beanutils.BeanUtilsBean.setProperty(BeanUtilsBean.java:1022)
????org.apache.commons.beanutils.BeanUtilsBean.populate(BeanUtilsBean.java:811)
????org.apache.commons.beanutils.BeanUtils.populate(BeanUtils.java:298)
????org.apache.struts.util.RequestUtils.populate(RequestUtils.java:493)
????org.apache.struts.action.RequestProcessor.processPopulate(RequestProcessor.java:805)
????org.apache.struts.action.RequestProcessor.process(RequestProcessor.java:203)
????org.apache.struts.action.ActionServlet.process(ActionServlet.java:1194)
????org.apache.struts.action.ActionServlet.doPost(ActionServlet.java:432)
????javax.servlet.http.HttpServlet.service(HttpServlet.java:710)
????javax.servlet.http.HttpServlet.service(HttpServlet.java:803)
note The full stack trace of the root cause is available in the Apache Tomcat/6.0.13 logs.
会报这个问题其实就是Struts没有提供相应的转换工具，我们都知道，网页POST过来的所有数据都是String类型，那为什么在ActionForm当中定义int型没有问题呢，原因就是Struts内部有一个类型转换器，能够自动地将String类型转换成为int,float,double,Integer,Float,Double等类型。那继承Struts内部有这些转换器，那我们是否可以对其进行扩展？答案是可以的，Struts的Converter框架很好地支持了这一点。
第五步，创建一个日期转换器类DateConverter.java，该类代码如下：
?程序代码package zizz.struts;import java.text.SimpleDateFormat;
import org.apache.commons.beanutils.Converter;
import java.util.Set;
import java.util.HashSet;
import java.util.Iterator;
import java.text.ParseException;
/**
*?
* 日期转换对象，使用该转换器，在BaseForm当中做一下注册，系统自动地帮助字符的日期表示转换为java.util.Date对象.
* @author zizz.
* Create Time：2006-9-11 19:11:47.
*/
public?class?DateConverter implements Converter?{
????/**
???? * 日期格式化对象.
???? */
????private?static?SimpleDateFormat df?=?new?SimpleDateFormat();
????
????/**
???? * 模式集合.
???? */
????private?static?Set<String>?patterns?=?new?HashSet<String>();
????//注册一下日期的转换格式
????static{
????????DateConverter.patterns.add("yyyy-MM-dd");
????????DateConverter.patterns.add("yyyy-MM-dd HH:mm");
????????DateConverter.patterns.add("yyyy-MM-dd HH:mm:ss");
????????DateConverter.patterns.add("yyyy/MM/dd HH:mm:ss");
????}
????
????/**
???? * 日期转换器.
???? * @param type Class
???? * @param value Object
???? * return Date Object.
???? */
????public?Object convert(Class type,Object value){
????????if(value?==?null){
????????????return?null;
????????}else?if(value instanceof String){
????????????Object dateObj?=?null;
????????????Iterator it?=?patterns.iterator();
????????????while(it.hasNext()){
????????????????try{
????????????????????String pattern?=?(String)it.next();
????????????????????df.applyPattern(pattern);
????????????????????dateObj?=?df.parse((String)value);
????????????????????break;
????????????????}catch(ParseException ex){
????????????????????//do iterator continue
????????????????}
????????????}
????????????return?dateObj;
????????}else{
????????????return?null;
????????}
????}
}
第六步，注册日期转换器
自定义的日期转换工作必须先做注册才能使用，注册我们可以将其放在ActionForm当中。
使用以下代码进行注册：
ConvertUtils.register(new DateConverter(), Date.class);
进行注册
修改完的UserForm.java如下：
?程序代码package zizz.struts;import java.util.Date;
import org.apache.struts.action.ActionForm;
import org.apache.commons.beanutils.ConvertUtils;
/**
* UserForm对应着提交页面的网页表单信息
* @author chen yuzhe
*
*/
public?class?UserForm extends ActionForm{
????
????static{
????????ConvertUtils.register(new?DateConverter(),?Date.class);
????}
????/**
???? * serialVersionUID
???? */
????private?static?final?long?serialVersionUID?=?-742922986494711669L