Java (J2EE) applications-the entire process of simple custom tag development-one (inber)-Java sleepless nights

Last Update:2018-12-05 Source: Internet

Author: User

Tags tld

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Tag application:
Data Source
Myperformance2
User sa
Password (null)
Database pubs table: employee

Description: windows ODBC --- SQL database pubs table: employee

Function: retrieve the data record of job_lvl> = 100 and call it wherever you want to call it on the JSP page.

1: Tag handler: EmployeeTag. java

Package net. inber;

Import javax. servlet. jsp .*;
Import javax. servlet. jsp. tagext .*;

Import java. util. Hashtable;
Import java. io. Writer;
Import java. io. IOException;
Import java. util. Date;

Import java. SQL .*;
Import java. math .*;
Import java. util .*;

Public class EmployeeTag extends TagSupport
{

Connection con = null;
Statement state = null;
Resultset rs = NULL;

Public employeetag () throws classnotfoundexception
{
Class. forname ("Sun. JDBC. ODBC. jdbcodbcdriver ");
}

Public int dostarttag () throws jsptagexception {

Return eval_body_include;
}

Public int doendtag () throws jsptagexception
{
String datestring = new date (). tostring ();
Try
{
Pagecontext. getout (). Write ("");

Try {
JspWriter out = pageContext. getOut ();
Con = DriverManager. getConnection ("jdbc: odbc: myperformance2", "sa ","");
String strQuery = "select emp_id, fname, lname, job_lvl, hire_date from employee where

Job_lvl & gt; = 100 ";
State = con. createStatement ();
Rs = state.exe cuteQuery (strQuery );
String emp_id = null;
String fname = null;
String lname = null;
String job_lvl = null;
String hire_date = null;

Out. Write ("<Table width = '000000' Height = '22' border = '1'> ");
While (Rs. Next ())
{
Emp_id = Rs. getstring (1 );
Fname = Rs. getstring (2 );
Lname = Rs. getstring (3 );
Job_lvl = Rs. getstring (4 );
Hire_date = Rs. getstring (5 );
Out. Write ("<tr> ");
Out. Write ("<TD width = '000000'>" + emp_id + "</TD> ");
Out. Write ("<TD width = '000000'>" + fname + "</TD> ");
Out. Write ("<TD width = '000000'>" + lname + "</TD> ");
Out. Write ("<TD width = '9% '>" + job_lvl + "</TD> ");
Out. Write ("<TD width = '000000'>" + hire_date + "</TD> ");
Out. Write ("</tr> ");
}
Out. write ("</table> ");

}
Catch (Exception e)
{
// Throw new JspTagException ("Fatal error: connect error! ");
}

}
Catch (IOException ex)
{
Throw new JspTagException ("Fatal error: hello tag conld not write

JSP out ");
}
Return EVAL_PAGE;
// Return SKIP_PAGE;
}
}
2. TLD file EmployeeTag. tld
<? Xml version = "1.0" encoding = "ISO-8859-1"?>

<Description> A tag library exercising SimpleTag handlers. </description>
<Tlib-version> 1.0 </tlib-version>
<Description>
A simple tab library for the examples
</Description>

<Tag>
<Description> select db pubs tb employees </description>
<Name> EmployeeTag </name>
<Tag-class> net. inber. EmployeeTag </tag-class>
<Body-content> jsp </body-content>
</Tag>

</Taglib>
3. Call index. JSP on the jsp page
<% @ Taglib uri = "/EmployeeTag" prefix = "a" %>
<% @ Page import = "net. inber. *" %>
<% @ Page contentType = "text/html; charset = gb2312" language = "java" %>
<Html>
<Head>
<Title> first cumstomed tag </title>
<Meta http-equiv = "Content-Type" content = "text/html; charset = gb2312">
</Head>
<Body>
<P> the following content is displayed for records whose job_lvl is greater than or equal to 100 in the database pubs retrieval table employee: </p>

4. TOMCAT deployment web. xml

<? Xml version = "1.0" encoding = "ISO-8859-1"?>
<! --
Copyright 2004 The Apache Software Foundation

Licensed under the Apache License, Version 2.0 (the "License ");
You may not use this file before t in compliance with the License.
You may obtain a copy of the License

Http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
Distributed under the license is distributed on an "as is" basis,
Without warranties or conditions of any kind, either express or implied.
See the license for the specific language governing permissions and
Limitations under the license.
-->

<Web-app xmlns = "http://java.sun.com/xml/ns/j2ee"
Xmlns: xsi = "http://www.w3.org/2001/XMLSchema-instance"
Xsi: schemalocation = "http://java.sun.com/xml/ns/j2ee http://java.sun.com/xml/ns/j2ee/web

-App_2_4.xsd"
Version = "2.4">

<Display-Name> welcome to Tomcat </display-Name>
<Description>
Welcome to Tomcat
</Description>

<! -- JSPC servlet mappings start -->

<Taglib>
<Taglib-uri>/EmployeeTag </taglib-uri>
<Taglib-location>/WEB-INF/tlds/EmployeeTag. tld </taglib-location>
</Taglib>

<! -- JSPC servlet mappings end -->

</Web-app>

Well, you should try the next step. If you have any questions, contact me.

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