leejeok

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Simple JNDI Accessing MySQL Datasource

Posted by leejeok on May 27, 2008

Base on the previous post, I have used the struts-config.xml to define the datasource to access to the MySQL database. The datasource class is code within the Action class (controller layer) and map to the struts-config.xml.

 

In order to improve the programming pratice, the datasource can be created via JNDI and the java code should be sit within the model layer. As a result, business logic will separate from the controller layer and making the Action class without knowing any relation with business class at all.

 

I am using Apache Tomcat 5.x and so, I will define the datasource resource via JNDI within the context.xml.

 

<Context path=”/bookstore”>

<ResourceLink global=”jdbc/bookstoreDB” name=”jdbc/bookstoreDB” type=”javax.sql.DataSource”/>

</Context>

 

The java code to make the database connection accessing the JNDI would be look like this:

 

    Connection cn(){

        DataSource ds = null;

       

        try {

            Context ctx = new InitialContext();

            if ( ctx == null ) {

                throw new RuntimeException(“JNDI Context could not be found.”);

            }

            ds = (DataSource)ctx.lookup(“java:comp/env/jdbc/bookstorDB”);

           

            if ( ds == null ) {

                throw new RuntimeException(“DataSource could not be found.”);

            }

            return ds.getConnection();

            // Handle any JNDI errors

        } catch (NamingException ne) {

            throw new RuntimeException(“A JNDI error occured. ” + ne.getMessage());

           

        }catch(Exception e){

            System.err.println(“Boom – No Context”);

        }

        return null;

}

 

Alternative, you can use JSP Standard Tag Library (JSTL) without embedding any Java code. I am using JSTL SQL tag here and may look like this:

 

<%@ taglib prefix=”sql” uri=”http://java.sun.com/jsp/jstl/sql&#8221; %>

<%@ taglib prefix=”c” uri=”http://java.sun.com/jsp/jstl/core&#8221; %>

 

<sql:setDataSource dataSource=”jdbc/bookstoreDB” />

 

<sql:query var=”qryBooks” >

    SELECT bookID, bookTitle, bookAuthor, bookPublisher FROM book

</sql:query>

 

<table>

    <c:forEach var=”row” items=”${qryBooks.rows}”>

        <tr>

            <td>${row.bookID}</td>

            <td>${row.bookTitle}</td>

            <td>${row.bookAuthor}</td>

            <td>${row.bookPublisher}</td>

        </tr>

    </c:forEach>

</table>

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One Response to “Simple JNDI Accessing MySQL Datasource”

  1. wilson said

    if there will be a problem, like you can’t run it. You may try to add the libraries:
    commons-dbcp-1.2.2.jar
    commons-pool-1.3.jar
    jdbcFramework_1_5.jar

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