struts2类型转换器日期转换小例详解

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数据类型转换器都需要实现ognl.TypeConverter接口，有一些教材的例子是通过继承TypeConverter接口的实现类DefaultTypeConverter从而自定义转换器，此时自定义转换器类需实现convertValue()方法，而比较新的都会通过继承DefaultTypeConvert的子类StrutsTypeConverter自定义转换器，此时需实现convertFromString()方法与convertToString()方法，这篇文章主要讲的是SturtsTypeConverter的一个案例。

先讲一下继承StrutsTypeConverter要实现的两个方法的作用及详解:

1.convertFromString(Map context, String[] values, Class toType)：将前台发送过来的数据以字符串形式接收，将字符串转换为自定义类型，然后返回自定义类型

参数详解:

context:为ActionContext(键为页面范围(如request、session)，值为存放的数据，或字符串，或列表....);

values:装有前台发送过来的数据的字符串数组

toClass:要转换的类型

2.convertToString(Map context,Object o):将converFromString()返回的自定义类型转换为字符串在前台显示,通过ognl表达式将会使用该方式进行转换

context --- actionContext o:要转换的对象(可以是converFromString返回的对象)

例:

User.java:

package com;public class User {private String date;public String getDate() {return date;}public void setDate(String date) {this.date = date;}@Overridepublic String toString(){return "日期" + this.date;}}</span>

UserAction.java:

package com;import com.opensymphony.xwork2.ActionSupport;public class UserAction extends ActionSupport{private static final long serialVersionUID = 1L;private User user;public String execute(){return SUCCESS;}public String input(){return INPUT;}public User getUser() {return user;}public void setUser(User user) {this.user = user;}}

index.jsp:

<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%><%@ taglib uri = "/struts-tags" prefix = "s" %><html>  <head>    <title>转换数据提交页</title>  </head>  <body>  <s:form action = "convert.action">  <s:textfield label = "日期" name = "user"></s:textfield>日期格式:xxxx-(x)x-(x)x  <s:submit></s:submit>  </s:form>  </body></html>

UserConvertor.java:

package com;import java.text.ParseException;import java.text.SimpleDateFormat;import java.util.Date;import java.util.Map;import org.apache.struts2.util.StrutsTypeConverter;public class UserConvertor extends StrutsTypeConverter{@SuppressWarnings("rawtypes")@Overridepublic Object convertFromString(Map context, String[] values, Class toType) {SimpleDateFormat fromFormat = new SimpleDateFormat("yyyy-MM-dd");SimpleDateFormat toFormat = new SimpleDateFormat("yyyy/MM/dd");User user = new User();System.out.println("转换器已调用");try {Date date = fromFormat.parse(values[0]);user.setDate(toFormat.format(date));System.out.println(user.getDate());} catch (ParseException e) {e.printStackTrace();}return user;}@Overridepublic String convertToString(@SuppressWarnings("rawtypes") Map context, Object object) {User user = (User) object;String out = "ognl通过转换器convertToString获取值:" + user.getDate();System.out.println("-----" + out + "------");return "ognl通过转换器convertToString获取值:" + user.getDate();}}

xwork-conversion.properties(置于项目src下):

com.User =com.UserConvertor

success.jsp:

<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%><%@ taglib uri = "/struts-tags" prefix = "s" %><html>  <head>    <title>转换数据接收页</title>  </head>  <body>  ognl表达式:<s:property value = "user"/><br>  el表达式:${user }<br>  request:${requestScope.user }<br>  session:${sessionScope.user }<br>  application:${applicationScope.user }<br>  pageContext:${pageContextScope.user }<br>  </body></html>

由结果可得:context的键默认为request，ognl表达式获取的值来自于convertToString()的返回值，EL表达式获取的值为对象中toString()的返回值

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