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JAVA/JSP Learning Series VII (Orion's CUSTOM tag) _jsp programming

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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!

Attached: Mytags.jar and hello.jsp file download address:

Http://www.wodejia.net/softdownload/java/orion_tag01.zip

This article is an English version of an article which is originally in the Chinese language on aliyun.com and is provided for information purposes only. This website makes no representation or warranty of any kind, either expressed or implied, as to the accuracy, completeness ownership or reliability of the article or any translations thereof. If you have any concerns or complaints relating to the article, please send an email, providing a detailed description of the concern or complaint, to info-contact@alibabacloud.com. A staff member will contact you within 5 working days. Once verified, infringing content will be removed immediately.

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