Struts2.0自定义标签

最近项目中有这样的需求，需要将普通的时间格式转行成时间间隔模式，如：将2009-07-01 10:16:14这种格式变成：昨天21:45:26 格式，我思前想后，为了显示的需要还是自定义个标签较合理。现将方法跟大家分享，算法不重要，重要的是自定义标签的流程。
我们分二步走
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";
         }
     }

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;
         }
}

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);

     }
}

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>

<?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>

经过这些操作后，一个自己的标签就弄好了，tld文件可以扩充，在用的时候就像Struts2自带的标签一样，导入，页面显示时就用<smallfish:times name="time" />这样就可以了。是不是很简单呢。

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