java(j2ee)应用－简单自定义标签开发全过程----之一（Inber）

标签应用：

数据源

MyDataSource2

用户sa

密码（空）

数据库pubs 表：employee

说明：windows ODBC ---SQL 数据库pubs 表：employee

功能：检索job_lvl>=100的数据记录，在JSP页面中任意想调用的地方调用它。

１：标签处理程序：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:MyDataSource2","sa","");

String strQuery = "select emp_id,fname,lname,job_lvl,hire_date from employee where

job_lvl>=100";

state = con.createStatement();

rs = state.executeQuery(strQuery);

String emp_id=null;

String fname=null;

String lname=null;

String job_lvl=null;

String hire_date=null;

out.write("<table width='677' 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='25%'>"+emp_id+"</td>");

out.write("<td width='17%'>"+fname+"</td>");

out.write("<td width='13%'>"+lname+"</td>");

out.write("<td width='9%'>"+job_lvl+"</td>");

out.write("<td width='36%'>"+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 to

JSP out");

}

return EVAL_PAGE;

// return SKIP_PAGE;

}

２.TLD文件EmployeeTag.tld

<?xml version="1.0" encoding="ISO-8859-1" ?>

<taglib 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 web-jsptaglibrary_2_0.xsd"

version="2.0">

<description>A tag library exercising SimpleTag handlers.</description>

<tlib-version>1.0</tlib-version>

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. JSP页面调用index.jsp

<%@ taglib uri="/EmployeeTag" prefix="a" %>

<%@ page import="net.inber.*"%>

<%@ page contentType="text/html; charset=gb2312" language="java" %>

<html>

<head>

<title>first cumstomed tag</title>

</head>

<body>

<p>以下的内容从库pubs检索表employee中job_lvl大于等于100的记录显示：</p>

<tr>

</tr>

</table>

<a:EmployeeTag/>

aaa

</body>

</html>

４。TOMCAT部署web.xml

<?xml version="1.0" encoding="ISO-8859-1"?>

<!--

Licensed under the Apache License, Version 2.0 (the "License");

you may not use this file except in compliance with the License.

You may obtain a copy of the License at

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>

Welcome to Tomcat

</description>

<taglib-uri>/EmployeeTag</taglib-uri>

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

</taglib>

</web-app>

好了，下面的最后一步你应该自已动手试试了，如有问题可以和我联系。