TagSupport

定义最简单的标签 
自定义标签采用Default Adapter模式（缺省适配模式） 
Java代码 
//最简单的标签   
public class LangHuaTag extends TagSupport {   
    private long startTime;   
    private long endTime;   
       
    public int doStartTag() throws JspException {   
        startTime = System.currentTimeMillis();   
        //表示定制标记里面有所包括的JSP页面   
        return TagSupport.EVAL_BODY_INCLUDE;   
    }   
    public int doEndTag() throws JspException {   
        endTime = System.currentTimeMillis();   
        long elapsed = endTime - startTime;        
        try {   
            JspWriter out = pageContext.getOut();   
            out.println("runtime is "+ elapsed);   
        } catch (IOException e) {   
            e.printStackTrace();   
        }   
        //表示JSP页面继续运行   
        return TagSupport.EVAL_PAGE;   
    }   
       
}   
//代属性的标签   
public class DateTag extends TagSupport {   
    private String pattern = "yyyy-MM-dd hh:mm:ss";   
    private Date date;   
    //必须要有Set方法，因为是属性可以设值   
    public void setPattern(String pattern) {   
        this.pattern = pattern;   
    }   
       
    public void setDate(Date date) {   
        this.date = date;   
    }   
  
    public int doEndTag() throws JspException {   
        SimpleDateFormat sdf = new SimpleDateFormat(pattern);   
        //如果没有就是当前时间   
        if(date==null){   
            date = new Date();   
        }          
        JspWriter out = pageContext.getOut();   
        try {   
            out.print(sdf.format(date));   
        } catch (IOException e) {   
            e.printStackTrace();   
        }   
        return TagSupport.EVAL_PAGE;   
    }   
}   
  
/**  
 * 循环输出  
 * @author Administrator  
 *  
 */  
public class LoopTag extends TagSupport {   
    private int times =0;   
    //Set方法设值   
    public void setTimes(int times) {   
        this.times = times;   
    }   
       
    public int doStartTag() throws JspException {   
        //表示定制标记里面有所包括的JSP页面   
        return TagSupport.EVAL_BODY_INCLUDE;   
    }   
       
    public int doAfterBody() throws JspException {   
        if(times>0){   
            times--;   
            //表示双从标签开始输入   
            return TagSupport.EVAL_BODY_AGAIN;   
        }      
        //表示结束，忽略标签内部的内容   
        return TagSupport.SKIP_BODY;   
    }   
       
}  

//最简单的标签
public class LangHuaTag extends TagSupport {
	private long startTime;
	private long endTime;
	
	public int doStartTag() throws JspException {
		startTime = System.currentTimeMillis();
		//表示定制标记里面有所包括的JSP页面
		return TagSupport.EVAL_BODY_INCLUDE;
	}
	public int doEndTag() throws JspException {
		endTime = System.currentTimeMillis();
		long elapsed = endTime - startTime;		
		try {
			JspWriter out = pageContext.getOut();
			out.println("runtime is "+ elapsed);
		} catch (IOException e) {
			e.printStackTrace();
		}
		//表示JSP页面继续运行
		return TagSupport.EVAL_PAGE;
	}
	
}
//代属性的标签
public class DateTag extends TagSupport {
	private String pattern = "yyyy-MM-dd hh:mm:ss";
	private Date date;
	//必须要有Set方法，因为是属性可以设值
	public void setPattern(String pattern) {
		this.pattern = pattern;
	}
	
	public void setDate(Date date) {
		this.date = date;
	}

	public int doEndTag() throws JspException {
		SimpleDateFormat sdf = new SimpleDateFormat(pattern);
		//如果没有就是当前时间
		if(date==null){
			date = new Date();
		}		
		JspWriter out = pageContext.getOut();
		try {
			out.print(sdf.format(date));
		} catch (IOException e) {
			e.printStackTrace();
		}
		return TagSupport.EVAL_PAGE;
	}
}

/**
 * 循环输出
 * @author Administrator
 *
 */
public class LoopTag extends TagSupport {
	private int times =0;
	//Set方法设值
	public void setTimes(int times) {
		this.times = times;
	}
	
	public int doStartTag() throws JspException {
		//表示定制标记里面有所包括的JSP页面
		return TagSupport.EVAL_BODY_INCLUDE;
	}
	
	public int doAfterBody() throws JspException {
		if(times>0){
			times--;
			//表示双从标签开始输入
			return TagSupport.EVAL_BODY_AGAIN;
		}	
		//表示结束，忽略标签内部的内容
		return TagSupport.SKIP_BODY;
	}
	
}




配置文件 
Xml代码 
<?xml version="1.0" encoding="UTF-8" ?>  
<taglib xmlns="http://java.sun.com/xml/ns/j2ee"  
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"  
    xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee http://java.sun.com/xml/ns/j2ee/web-jsptaglibrary_2_0.xsd"  
    version="2.0">  
    <tlib-version>1.0</tlib-version>  
    <short-name>util</short-name>  
    <uri>http://langhua.com/taglib/util</uri>  
    <tag>  
        <name>timer</name>  
        <tag-class>com.langhua.tagsupport.LangHuaTag</tag-class>  
        <body-content>JSP</body-content>  
        <!-- JSP,empty表示能能包函内容的,scriptless,tagdependent -->  
    </tag>  
       
    <tag>  
        <name>date</name>  
        <tag-class>com.langhua.tagsupport.DateTag</tag-class>  
        <body-content>empty</body-content>         
        <!-- JSP,empty表示不能包函内容的,scriptless,tagdependent -->  
        <attribute>  
            <!-- 标签名 -->  
            <name>time</name>  
            <!-- 是否为可选属性 -->  
            <required>false</required>  
            <!-- 是否接受JSP表达示计算结果 -->  
            <rtexprvalue>true</rtexprvalue>  
        </attribute>  
        <attribute>  
            <name>pattern</name>  
            <required>true</required>  
            <rtexprvalue>false</rtexprvalue>  
        </attribute>  
    </tag>  
       
    <tag>  
        <name>loop</name>  
        <tag-class>com.langhua.tagsupport.LoopTag</tag-class>  
        <body-content>JSP</body-content>           
        <!-- JSP,empty表示不能包函内容的,scriptless,tagdependent -->  
        <attribute>  
            <!-- 标签名 -->  
            <name>times</name>  
            <!-- 是否为可选属性 -->  
            <required>true</required>  
            <!-- 是否接受JSP表达示计算结果 -->  
            <rtexprvalue>true</rtexprvalue>  
        </attribute>         
    </tag>  
</taglib>  

<?xml version="1.0" encoding="UTF-8" ?>
<taglib xmlns="http://java.sun.com/xml/ns/j2ee"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee http://java.sun.com/xml/ns/j2ee/web-jsptaglibrary_2_0.xsd"
    version="2.0">
    <tlib-version>1.0</tlib-version>
    <short-name>util</short-name>
    <uri>http://langhua.com/taglib/util</uri>
    <tag>
        <name>timer</name>
		<tag-class>com.langhua.tagsupport.LangHuaTag</tag-class>
		<body-content>JSP</body-content>
		<!-- JSP,empty表示能能包函内容的,scriptless,tagdependent -->
    </tag>
    
    <tag>
        <name>date</name>
		<tag-class>com.langhua.tagsupport.DateTag</tag-class>
		<body-content>empty</body-content>		
		<!-- JSP,empty表示不能包函内容的,scriptless,tagdependent -->
		<attribute>
			<!-- 标签名 -->
			<name>time</name>
			<!-- 是否为可选属性 -->
			<required>false</required>
			<!-- 是否接受JSP表达示计算结果 -->
			<rtexprvalue>true</rtexprvalue>
		</attribute>
		<attribute>
			<name>pattern</name>
			<required>true</required>
			<rtexprvalue>false</rtexprvalue>
		</attribute>
    </tag>
    
    <tag>
        <name>loop</name>
		<tag-class>com.langhua.tagsupport.LoopTag</tag-class>
		<body-content>JSP</body-content>		
		<!-- JSP,empty表示不能包函内容的,scriptless,tagdependent -->
		<attribute>
			<!-- 标签名 -->
			<name>times</name>
			<!-- 是否为可选属性 -->
			<required>true</required>
			<!-- 是否接受JSP表达示计算结果 -->
			<rtexprvalue>true</rtexprvalue>
		</attribute>		
    </tag>
</taglib>


JSP页面 
Html代码 
<%@ taglib prefix="util" uri="http://langhua.com/taglib/util"%>  
  
<util:timer></util:timer>  
<util:loop times="3">  
    <util:date pattern="yyyy-MM-dd" /><br/>  
</util:loop>  

<%@ taglib prefix="util" uri="http://langhua.com/taglib/util"%>

<util:timer></util:timer>
<util:loop times="3">
  	<util:date pattern="yyyy-MM-dd" /><br/>
</util:loop>

TagSupport的流程图 
 
EVAL_BODY_INCLUDE 处理标记内容,并把这些内容写到输出流中doStartTag() 
SKIP_BODY 不处理标记内容doStartTag()，doAfterBody() 
EVAL_BODY_AGAIN 又重头处理doAfterBody() 
EVAL_PAGE 继续执行JSP里面的代码 doEndTag() 
SKIP_PAGE 不继续执行JSP里面的代码 doEndTag() 

[img]http://langhua9527.iteye.com/upload/attachment/77593/2ce5c561-a5ea-36d1-9082-25e62273dcb2.jpg[/img]