struts2类型转换器日期转换小例详解

谁借莪１个温暖的怀抱￠ 2022-08-23 08:17 206阅读 0赞

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;
 	}
 	@Override
 	public String toString(){
 		return "日期" + this.date;	
 	}
 }

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")
    	@Override
    	public 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;
    	}
    	@Override
    	public 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"/> 
 el表达式:${user } 
 request:${requestScope.user } 
 session:${sessionScope.user } 
 application:${applicationScope.user } 
 pageContext:${pageContextScope.user } 
 </body>
 </html>

![Center][]![Center 1][]  
                  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

[Center]: https://img-blog.csdn.net/20160612131910959?watermark/2/text/aHR0cDovL2Jsb2cuY3Nkbi5uZXQv/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70/gravity/Center
[Center 1]: /images/20220721/5111ebab896543169f037ec39d2da94a.png