JAVA/JSP学习系列之七
一、前言 (本文译自Orion官方站点)
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。
二、建立标签,实现该标签的功能。
1.命名package为:com.acme.mytags(为了和原文相同,我不做改动)
package com.acme.mytags;
2.import相关class
import javax.servlet.jsp.*;
import javax.servlet.jsp.tagext.*;
3.实现javax.servlet.jsp.tagext.Tag接口:
public class HelloWorld implements Tag
{
4.定义局部变量
private PageContext pageContext;
private Tag parent;
5.调用标签开始的实现方法
public int doStartTag() throws javax.servlet.jsp.JspException
{
return SKIP_BODY;
}
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
6.调用标签结束的实现方法
public int doEndTag() throws javax.servlet.jsp.JspException
{
try
{
pageContext.getOut().write('Hello World!');
}
catch(java.io.IOException e)
{
throw new JspException('IO Error: ' + e.getMessage());
}
return EVAL_PAGE;
}
这样将在jsp文件的自定义标签结束地方输出“Hello World!”
7.还不够,我们还要写下面的方法:
public void release() {}
对于本简单的例子,上面的方法不需要任何实现。
8.JSP的容器要调用下面的方法:
public void setPageContext(final javax.servlet.jsp.PageContext pageContext) {
this.pageContext=pageContext;
}
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.
9.JSP的容器还要调用下面的方法:
public void setParent(final javax.servlet.jsp.tagext.Tag parent)
{
this.parent=parent;
}
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。
10.最后,实现方法:
public javax.servlet.jsp.tagext.Tag getParent()
{
return parent;
}
}
11. 编译标签。
三、描叙标签
现在将要写一个描叙文件,描叙该标签。
1.建立一个taglib.tld文件,
2.taglib.tld是一个XML格式的文本文件,XML的头如下:
'http://java.sun.com/j2ee/dtds/web-jsptaglibrary_1_1.dtd'>
3.描叙标签库
1.0
1.1
mt http://www.orionserver.com/tutorials/tagtut/lesson1/mytags.jar
My first Tag library
4.描叙标签
helloWorld
com.acme.mytags.HelloWorld
empty
A Hello world Tag
5.结束
四、打包
名称为:mytags.jar
其目录结构为:
com/acme/mytags/HelloWorld.class
META-INF/taglib.tld
五、在jsp文件中使用自定义标签
建立hello.jsp如下:
六、测试运行
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。
E:oriondefault-web-app ag
将jar文件和jsp文件全部放到这个目录下。
然后,访问:
http://localhost:[port]/tag/hello.jsp
将出现:
------------------------------------------------------------------
Hello World!
------------------------------------------------------------------
七、恭喜,你已经成功了!
附:mytags.jar和hello.jsp 文件本站下载地址:
http://www.wodejia.net/softdownload/java/orion_tag01.zip(出处:viphot.com)

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