Struts2.0自定义标签

1.编写自定义标签类。
2. 创建taglib文件(.tld)，编写标签声明。

第一步：
首先编写时间格式转换的方法： 

 

public static String getDisplayTime(Date date){    
         Date nowDate=new Date();    
         Calendar oldCalendar=Calendar.getInstance();    
         Calendar nowCalendar=Calendar.getInstance();    
         oldCalendar.setTime(date);    
         nowCalendar.setTime(nowDate);    
        int day=getDaysBetween(oldCalendar,nowCalendar);    
         Long nowTime=nowDate.getTime();    
         Long oldTime=date.getTime();    
         Long time=nowTime-oldTime;    
        if(time>60*60*1000){    
            if(day==0){    
                return new SimpleDateFormat("HH:mm:ss").format(date);    
             }else if(day==1){    
                return "昨天"+new SimpleDateFormat("HH:mm:ss").format(date);    
             }else if(day==2){    
                return "前天"+new SimpleDateFormat("HH:mm:ss").format(date);    
             }else{    
                return new SimpleDateFormat("yyyy-MM-dd").format(date);    
             }    
         }else if(time<60*1000){    
            return "刚刚";    
         }else{    
            return (long)time/(60*1000)+"分钟前";    
         }    
     }   

 

这段代码很简单，相信大家一看便懂了。
下面是距离当前时间天数的方法：

public class Times extends Component{    
    private String name;    
        
    public String getName() {    
        return name;    
     }    
   
    public void setName(String name) {    
        this.name = name;    
     }    
    public Times(ValueStack arg0) {       
        super(arg0);       
     }       
    @Override      
        public boolean start(Writer writer) {    
            boolean result = super.start(writer);    
            try {    
                 java.util.Date date = (java.util.Date) findValue(name);    
                 String str=DataTime.getDisplayTime(date);    
                 writer.write(str);    
             } catch (IOException ex) {    
                 Logger.getLogger(Pages.class.getName()).log(Level.SEVERE, null, ex);    
             }    
            return result;    
         }       
}   

 

这里是写一个方法调用这个算法返回一个值

public class TimeTag extends ComponentTagSupport{    
    private String name;    
   
    public void setName(String name) {    
        this.name = name;    
     }    
   
    @Override      
    public Component getBean(ValueStack arg0, HttpServletRequest arg1, HttpServletResponse arg2) {       
        return new Times(arg0);       
     }       
      
    //获得参数       
    protected void populateParams() {       
        super.populateParams();       
         Times pages = (Times)component;       
         pages.setName(name);    
             
     }       
}   

 

这里继承ComponentTagSupport类是为了获得标签中的属性值，并包装成Component对象。继承Component类是为了从Struts2中的ValueStack中获得相对应的值。
第二步：建立smallfish.tld

<?xml version="1.0" encoding="UTF-8"?>      
<!DOCTYPE taglib PUBLIC "-//Sun Microsystems, Inc.//DTD JSP Tag Library 1.2//EN" "http://java.sun.com/dtd/web-jsptaglibrary_1_2.dtd">      
<taglib>    
     <tlib-version>2.2.3</tlib-version>    
     <jsp-version>1.2</jsp-version>    
     <short-name>smallfish</short-name>    
     <uri>/jzy</uri>    
     <display-name>"smallfish Tags"</display-name>         
            <tag>    
             <name>times</name>    
             <tag-class>com.common.tag.TimeTag</tag-class>    
             <body-content>empty</body-content>    
             <attribute>    
                 <name>name</name>    
                 <required>true</required>    
                 <rtexprvalue>true</rtexprvalue>    
             </attribute>    
         </tag>    
</taglib>