📄 taglib原理和实现之循环的tag - fanqiang_com.htm
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EVAL_BODY_INCLUDE;<BR> }<BR> public int doEndTag()throws
JspException<BR> { <BR> return EVAL_PAGE;<BR> }<BR>}
</TD></TR></TBODY></TABLE><BR> 编写WithCollectionTag，该Tag负责取得Collection，并遍历执行子Tag<BR><BR>
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<TD>package diegoyun;<BR><BR>import
java.util.Collection;<BR>import
java.util.Iterator;<BR><BR>import
javax.servlet.jsp.JspException;<BR>import
javax.servlet.jsp.tagext.BodyTagSupport;<BR><BR>import
org.apache.commons.beanutils.PropertyUtils;<BR><BR>public
class WithCollectionTag extends BodyTagSupport {<BR> private
Object element = null;<BR><BR> private Collection list =
null;<BR><BR> private Iterator iterator = null;<BR><BR> public
Object getElement() {<BR> return
element;<BR> }<BR><BR> public void setProperty(String
property) throws JspException
{<BR> //取得父Tag对象,并且得到Collection<BR> WithObjectTag parent =
(WithObjectTag) getParent();<BR> if (parent ==
null)<BR> throw new JspException("parent tag is
null");<BR> try {<BR> Object propertyValue =
PropertyUtils.getProperty(parent.getValue(),property);<BR> this.list
= (Collection) propertyValue;<BR> if (list ==
null)<BR> throw new JspException("Collection is
null");<BR> } catch (Exception e) {<BR> throw new
JspException(e);<BR> }<BR> }<BR><BR> public int doStartTag()
throws JspException {<BR> //设置第一个元素,然后执行子Tag<BR> iterator =
list.iterator();<BR> if (iterator.hasNext())<BR> element =
iterator.next();<BR> return
EVAL_BODY_INCLUDE;<BR> }<BR><BR> public int doAfterBody()
{<BR> if (iterator.hasNext())
{<BR> //如果还存在子元素,设置子元素,并且再次执行子Tag<BR> //循环由此而来<BR> //否则不再执行子Tag<BR> element
= iterator.next();<BR> return
EVAL_BODY_AGAIN;<BR> }<BR> else<BR> return
EVAL_PAGE;<BR> }<BR>}</TD></TR></TBODY></TABLE><BR> 编写
ElementOutputTag<BR><BR>
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<TD>package diegoyun;<BR>import
java.io.IOException;<BR><BR>import
javax.servlet.jsp.JspException;<BR>import
javax.servlet.jsp.tagext.TagSupport;<BR><BR>import
org.apache.commons.beanutils.PropertyUtils;<BR><BR>public
class ElementOutputTag extends TagSupport<BR>{<BR> private
Object propertyValue = null;<BR> public void
setProperty(String property)throws
JspException<BR> {<BR> WithCollectionTag parent =
(WithCollectionTag)getParent();<BR> if(parent ==
null)<BR> throw new JspException("parent tag is
null");<BR> try<BR> {<BR> //判断上层tag中是否存在该属性名称,如果存在,取得属性值,否则报错<BR> propertyValue
= PropertyUtils.getProperty(parent.getElement(),
property);<BR> }<BR> catch (Exception e)<BR> {<BR> throw
new JspException(e);<BR> }<BR> }<BR> public int
doEndTag()throws
JspException<BR> {<BR> try<BR> {<BR> //简单的把值打印到jsp页面<BR> pageContext.getOut().print(propertyValue);<BR> }<BR> catch
(IOException e)<BR> {<BR> throw new
JspException(e);<BR> }<BR> return
EVAL_PAGE;<BR> }<BR>}</TD></TR></TBODY></TABLE><BR> 编写tld<BR><BR>
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<TD>＜!--WithObjectTag--＞<BR>＜tag＞<BR> ＜name＞withObject＜/name＞<BR> ＜tag-class＞diegoyun.WithObjectTag＜/tag-class＞<BR> ＜body-content＞JSP＜/body-content＞<BR> ＜attribute＞<BR> ＜name＞value＜/name＞<BR> ＜required＞false＜/required＞<BR> ＜rtexprvalue＞true＜/rtexprvalue＞<BR> ＜/attribute＞<BR>＜/tag＞<BR>＜!--WithCollectionTag--＞<BR>＜tag＞<BR> ＜name＞withCollection＜/name＞<BR> ＜tag-class＞diegoyun.WithCollectionTag＜/tag-class＞<BR> ＜body-content＞JSP＜/body-content＞<BR> ＜attribute＞<BR> ＜name＞property＜/name＞<BR> ＜required＞false＜/required＞<BR> ＜rtexprvalue＞true＜/rtexprvalue＞<BR> ＜/attribute＞<BR>＜/tag＞<BR>＜!--ElementOutputTag--＞<BR>＜tag＞<BR> ＜name＞elementout＜/name＞<BR> ＜tag-class＞diegoyun.ElementOutputTag＜/tag-class＞<BR> ＜body-content＞empty＜/body-content＞<BR> ＜attribute＞<BR> ＜name＞property＜/name＞<BR> ＜required＞false＜/required＞<BR> ＜rtexprvalue＞true＜/rtexprvalue＞<BR> ＜/attribute＞<BR>＜/tag＞</TD></TR></TBODY></TABLE><BR> 编写jsp<BR><BR>
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<TD>＜%@ page language="java" %＞<BR>＜%@ page
import="diegoyun.vo.*"%＞<BR>＜%@ page
import="java.util.*"%＞<BR>＜%@ taglib
uri="/WEB-INF/tlds/diego.tld"
prefix="diego"%＞<BR><BR>＜html＞<BR>＜body
bgcolor="#FFFFFF"＞<BR>＜%<BR> Collection c = new
ArrayList();<BR><BR> Man man1 = new
Man();<BR> man1.setName("diego");<BR> c.add(man1);<BR><BR> Man
man2 = new
Man();<BR> man2.setName("Zidane");<BR> c.add(man2);<BR><BR> Man
man3 = new
Man();<BR> man3.setName("Rui");<BR> c.add(man3);<BR><BR> People
p =new
People();<BR> p.setMen(c);<BR> request.setAttribute("people",p);<BR>%＞<BR>Test
loop tag:<BR>＜br＞<BR>＜diego:withObject
value="${people}"＞<BR>＜diego:withCollection
property="men"＞<BR>＜diego:elementout
property="name"/＞<BR>＜br＞<BR>＜/diego:withCollection＞<BR>＜/diego:withObject＞<BR>＜/body＞<BR>＜/html＞</TD></TR></TBODY></TABLE><BR> 运行,则可以看到: <BR><BR>
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<TD>Test loop tag: <BR>diego <BR>Zidane
<BR>Rui</TD></TR></TBODY></TABLE></SPAN><!-- 正文end --><BR>(http://www.fanqiang.com)<BR></FONT><BR><FONT
color=#999999><SMALL>原文链接：<A
href="http://news.chinabyte.com/SoftChannel/72342371945283584/20041229/1894523.shtml"
target=_blank>http://news.chinabyte.com/SoftChannel/72342371945283584/20041229/1894523.shtml</A></SMALL></FONT>
<BR></FONT></TD></TR></TBODY></TABLE><BR></TD></TR></TBODY></TABLE>
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<TD align=middle width=620>
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<TD width=562>
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<TD width="100%" bgColor=#d09f0d colSpan=5 height=2><IMG height=1
src="Taglib原理和实现之循环的Tag - fanqiang_com.files/c.gif" width=1></TD></TR>
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<P align=center><FONT
color=#ffffff>★ 感谢所有的作者为我们学习技术知识提供了一条捷径 ★
<BR>www.fanqiang.com</FONT></P></TD></TR></TBODY></TABLE>
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