Home php教程 php手册 JAVA/JSP学习系列之七

JAVA/JSP学习系列之七

Jun 13, 2016 pm 12:46 PM
java jsp one step introduce Preface exist study Will series


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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