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JAVA/JSP Learning Series VII (custom tag under Orion)

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JS First, preface (this article is translated from the Orion official site)

This article takes a step-by-step introduction to defining your own label under the Orion application Server, then implements the tag's functionality, and finally tests it with a JSP example.

Second, the establishment of a label to achieve the function of the label.

1. Named Package: Com.acme.mytags (for the same as the original, I do not make changes)

Package com.acme.mytags;

2.import Related class

Import javax.servlet.jsp.*;

Import javax.servlet.jsp.tagext.*;

3. Implement JAVAX.SERVLET.JSP.TAGEXT.TAG Interface:

public class HelloWorld implements Tag

{

4. Define Local variables

Private PageContext PageContext;

Private Tag parent;

5. Calling the implementation of the tag Start method

public int doStartTag () throws Javax.servlet.jsp.JspException

{

return skip_body;

}

Note: This method returns Skip_body, that is, when the body of the label is empty, it returns this value, otherwise it will return: Eval_body_include

6. The implementation method of calling tag end

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;

}

This will output "Hello world!" at the end of the custom tag of the JSP file

7. Not enough, we have to write the following method:

public void Release () {}

For this simple example, the above method does not require any implementation.

8.JSP container to invoke the following method:

public void Setpagecontext (final javax.servlet.jsp.PageContext PageContext) {

This.pagecontext=pagecontext;

}

The JSP container invokes the label through the method above, and the method above is used to set the label's PageContext.

The 9.JSP container also calls the following method:

public void SetParent (final javax.servlet.jsp.tagext.Tag parent)

{

This.parent=parent;

}

The JSP container sets the label's Parent-tag by the above method, because each label's PageContext retains its parent tag.

10. Finally, the implementation method:

Public Javax.servlet.jsp.tagext.Tag GetParent ()

{

return to parent;

}

}

11. Compile tags.

Third, describe the label

Now you're going to write a description file describing the label.

1. Establishment of a TAGLIB.TLD document,

2.TAGLIB.TLD is an XML-formatted text file with the following XML headers:

<?xml version= "1.0" encoding= "Iso-8859-1"?>
<! DOCTYPE taglib Public "-//sun Microsystems, Inc.//dtd JSP Tag Library 1.1//en"
"Http://java.sun.com/j2ee/dtds/web-jsptaglibrary_1_1.dtd" >

3. Describe tag Library

<taglib>

<tlibversion>1.0</tlibversion>

<jspversion>1.1</jspversion>

<shortname>mt</shortname> <uri>http://www.orionserver.com/tutorials/tagtut/lesson1/mytags.jar </uri>

<info>my-A-Tag library</info>

4. Describe the label

<tag>

<name>helloWorld</name>

<tagclass>com.acme.mytags.HelloWorld</tagclass>

<bodycontent>empty</bodycontent>

<info>a Hello World tag</info>

</tag>

5. End

</taglib>

Four, packing

Name is: Mytags.jar

Its directory structure is:

Com/acme/mytags/helloworld.class

Meta-inf/taglib.tld

Use custom labels in your JSP files

The establishment of HELLO.JSP is as follows:

<%@ taglib uri= "Mytags.jar" prefix= "MT"%>

<HTML>

<HEAD>

<title>hello world!</title>

</HEAD> <body bgcolor= "#FFFFFF" >

<HR>

<mt:helloWorld/>

<HR>

</BODY>

</HTML>

VI. Test run

In the Orion directory, set up the following structure, where tag is built by itself, the previous directory is already there.

E:\orion\default-web-app\tag

Put the jar file and the JSP file all in this directory.

Then, visit:

http://localhost:[port]/tag/hello.jsp

will appear:
------------------------------------------------------------------
Hello world!
------------------------------------------------------------------

Congratulations, you have succeeded!


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