基于Converter解决Struts1无法处理日期类型的问题

转自http://www.suneca.com

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;

    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;
    }
    
}