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用标签实现循环功能－－－标签开发之三(Inber原作）

2004-08-26 09:30 411 查看

用标签实现循环功能－－－标签开发之三(Inber原作）

主要练习知识点：页面与脚本变量
关键字：页面与脚本变量，标签

第一步：标签处理程序：ForTag.java

package net.inber.jsptaglibs.iteration;

import javax.servlet.jsp.*;
import javax.servlet.jsp.tagext.*;

/**
* Given a range of values, this tag iterates over each value and makes it
* available to the page.
*
* @author Inber Gong
*/
public class ForTag extends TagSupport {

/** the starting index (defaults to zero) */
private int from = 0;

/** the finishing index */
private int to;

/** the current index */
private int index;

/**
* Called when the starting tag is encountered.
*/
public int doStartTag() throws JspException {
// setup the counter variable
index = from;

if (index < to) {
// put the first index into the page
pageContext.setAttribute("index", new Integer(index));

// and include the body
return EVAL_BODY_INCLUDE;
} else {
// there are no elements so skip the body
return SKIP_BODY;
}
}

/**
* Called after the body has been included.
*/
public int doAfterBody() throws JspException {
// increment the counter
index++;

if (index < to) {
// put the next index into the page
pageContext.setAttribute("index", new Integer(index));

// and instruct the JSP engine to re-evaluate the body of this tag
return EVAL_BODY_AGAIN;
} else {
// there are no more elements so skip the body
return SKIP_BODY;
}
}

/**
* Setter for the "from" attribute.
*
* @param i an integer value
*/
public void setFrom(int i) {
this.from = i;
}

/**
* Setter for the "to" attribute.
*
* @param i an integer value
*/
public void setTo(int i) {
this.to = i;
}

}
（2）配置标签库描述符(TLD)文件 configTLD.tld
<?xml version="1.0" encoding="ISO-8859-1" ?>
<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 web-jsptaglibrary_2_0.xsd"
version="2.0">
<description>A tag library exercising SimpleTag handlers.</description>
<tlib-version>1.0</tlib-version>
<short-name>examples</short-name>
<uri>/demotag</uri>
<description>
A simple tab library for the examples
</description>

<tag>
<description></description>
<name>bookView</name>
<tag-class>net.inber.jsptaglibs.iteration.ForTag</tag-class>
<body-content>jsp</body-content>

<variable>
<name-given>index</name-given>
<variable-class>java.lang.Integer</variable-class>
<declare>true</declare>
</variable>
<body-content>jsp</body-content>



<attribute>
<name>from</name>
<required>true</required>
<rtexprvalue>true</rtexprvalue>
</attribute>

<attribute>
<name>to</name>
<required>true</required>
<rtexprvalue>true</rtexprvalue>
</attribute>


</tag>

</taglib>
（3）创建JSP文件index.jsp
<html>
<%@ taglib uri="/tagURI" prefix="fromTo" %>
<body>
<h1>loops</h1>
<fromTo:bookView from="0" to="10">

<p>
<br>
<%=index.intValue()%>
</p>

</fromTo:bookView>

</body>

</html>

(4)布署tomcat web.xml
<?xml version="1.0" encoding="ISO-8859-1"?>


<web-app 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
-app_2_4.xsd"
version="2.4">

<display-name>Welcome to Tomcat</display-name>
<description>
Welcome to Tomcat
</description>


<taglib>
<taglib-uri>/tagURI</taglib-uri>
<taglib-location>/WEB-INF/tlds/configTLD.tld</taglib-location>
</taglib>



</web-app>

好了下面该你动手了，源文件下载地址：http://inber.51.net/csdn_blog/soft/fortag.rar
如有问题忙快和我联系。

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