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<title>csdn_Orion下自定义Tag</title>
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<td WIDTH="50%" bordercolor="#FFFFFF" CLASS="t1" bgcolor="#F0F0F0" align="center" nowrap>Orion下自定义Tag</td>
<p> <td WIDTH="50%" bordercolor="#FFFFFF" CLASS="t1" bgcolor="#F0F0F0" align="center" nowrap>作者：东方一蛇
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一、前言 (本文译自Orion官方站点)<br>
<br>
本文将一步一步介绍在Orion Application Server下定义自己的标签，然后，实现该标签的功能，最后用一个jsp例子测试。 <br>
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二、建立标签，实现该标签的功能。<br>
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1.命名package为：com.acme.mytags(为了和原文相同，我不做改动)<br>
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package com.acme.mytags;<br>
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2.import相关class<br>
<br>
import javax.servlet.jsp.*;<br>
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import javax.servlet.jsp.tagext.*;<br>
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3.实现javax.servlet.jsp.tagext.Tag接口：<br>
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public class HelloWorld implements Tag <br>
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{<br>
<br>
4.定义局部变量<br>
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private PageContext pageContext; <br>
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private Tag parent; <br>
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5.调用标签开始的实现方法<br>
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public int doStartTag() throws javax.servlet.jsp.JspException <br>
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{<br>
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return SKIP_BODY; <br>
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} <br>
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注意：这个方法返回 SKIP_BODY，就是标签的body为空的时候，将返回这个值，否则将返回：EVAL_BODY_INCLUDE<br>
<br>
6.调用标签结束的实现方法<br>
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public int doEndTag() throws javax.servlet.jsp.JspException <br>
<br>
{ <br>
<br>
try <br>
<br>
{ <br>
<br>
pageContext.getOut().write("Hello World!"); <br>
<br>
} <br>
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catch(java.io.IOException e) <br>
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{ <br>
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throw new JspException("IO Error: " + e.getMessage()); <br>
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} <br>
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return EVAL_PAGE; <br>
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} <br>
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这样将在jsp文件的自定义标签结束地方输出“Hello World!”<br>
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7.还不够，我们还要写下面的方法：<br>
<br>
public void release() {} <br>
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对于本简单的例子，上面的方法不需要任何实现。<br>
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8.JSP的容器要调用下面的方法：<br>
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public void setPageContext(final javax.servlet.jsp.PageContext pageContext) { <br>
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this.pageContext=pageContext; <br>
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} <br>
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JSP容器通过上面的方法调用标签，而且上面的方法用来设置标签的PageContext.<br>
<br>
9.JSP的容器还要调用下面的方法：<br>
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public void setParent(final javax.servlet.jsp.tagext.Tag parent) <br>
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{ <br>
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this.parent=parent; <br>
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}<br>
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JSP容器通过上面的方法设置标签的parent-Tag，因为每个标签的PageContext都要保留它的parent标签。 <br>
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10.最后，实现方法：<br>
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public javax.servlet.jsp.tagext.Tag getParent() <br>
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{ <br>
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return parent;<br>
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}<br>
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} <br>
<br>
11. 编译标签。<br>
<br>
三、描叙标签<br>
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现在将要写一个描叙文件，描叙该标签。<br>
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1.建立一个taglib.tld文件，<br>
<br>
2.taglib.tld是一个XML格式的文本文件，XML的头如下：<br>
<br>
<?xml version="1.0" encoding="ISO-8859-1" ?> <br>
<!DOCTYPE taglib PUBLIC "-//Sun Microsystems, Inc.//DTD JSP Tag Library 1.1//EN" <br>
"http://java.sun.com/j2ee/dtds/web-jsptaglibrary_1_1.dtd"> <br>
<br>
3.描叙标签库<br>
<br>
<taglib> <br>
<br>
<tlibversion>1.0</tlibversion> <br>
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<jspversion>1.1</jspversion><br>
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<shortname>mt</shortname> <uri>http://www.orionserver.com/tutorials/tagtut/lesson1/mytags.jar</uri><br>
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<info>My first Tag library</info> <br>
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4.描叙标签<br>
<br>
<tag><br>
<br>
<name>helloWorld</name><br>
<br>
<tagclass>com.acme.mytags.HelloWorld</tagclass> <br>
<br>
<bodycontent>empty</bodycontent> <br>
<br>
<info>A Hello world Tag</info><br>
<br>
</tag><br>
<br>
5.结束<br>
<br>
</taglib><br>
<br>
四、打包<br>
<br>
名称为：mytags.jar<br>
<br>
其目录结构为：<br>
<br>
com/acme/mytags/HelloWorld.class<br>
<br>
META-INF/taglib.tld<br>
<br>
五、在jsp文件中使用自定义标签<br>
<br>
建立hello.jsp如下：<br>
<br>
<%@ taglib uri="mytags.jar" prefix="mt" %> <br>
<br>
<HTML> <br>
<br>
<HEAD> <br>
<br>
<TITLE>Hello World!</TITLE><br>
<br>
</HEAD> <BODY BGCOLOR="#FFFFFF"> <br>
<br>
<HR> <br>
<br>
<mt:helloWorld/><br>
<br>
<HR> <br>
<br>
</BODY> <br>
<br>
</HTML> <br>
<br>
六、测试运行<br>
<br>
在orion目录下，建立如下结构，其中，tag是自己建立的，前面的目录是本来就有的。<br>
<br>
E:\orion\default-web-app\tag<br>
<br>
将jar文件和jsp文件全部放到这个目录下。<br>
<br>
然后，访问：<br>
<br>
http://localhost:[port]/tag/hello.jsp<br>
<br>
将出现：<br>
<br>
<br>
--------------------------------------------------------------------------------<br>
<br>
<br>
Hello World! <br>
<br>
<br>
--------------------------------------------------------------------------------<br>
<br>
七、恭喜，你已经成功了！<br>
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