22.3.14.1. A Simple JSP Application with Glassfish, Connector/J and MySQL

This section shows how to deploy a simple JSP application on Glassfish, that connects to a MySQL database.

This example assumes you have already set up a suitable Connection Pool and JDBC Resource, as explained in the preceding sections. It is also assumed you have a sample database installed, such as world.

The main application code, index.jsp is presented here:

<%@ page import="java.sql.*, javax.sql.*, java.io.*, javax.naming.*" %><html><head><title>Hello world from JSP</title></head><body><%  InitialContext ctx;  DataSource ds;  Connection conn;  Statement stmt;  ResultSet rs;  try {    ctx = new InitialContext();    ds = (DataSource) ctx.lookup("java:comp/env/jdbc/MySQLDataSource");    //ds = (DataSource) ctx.lookup("jdbc/MySQLDataSource");    conn = ds.getConnection();    stmt = conn.createStatement();    rs = stmt.executeQuery("SELECT * FROM Country");    while(rs.next()) {%>    <h3>Name: <%= rs.getString("Name") %></h3>    <h3>Population: <%= rs.getString("Population") %></h3><%        }  }  catch (SQLException se) {%>    <%= se.getMessage() %><%        }  catch (NamingException ne) {%>      <%= ne.getMessage() %><%  }%></body></html>

In addition two XML files are required: web.xml, and sun-web.xml. There may be other files present, such as classes and images. These files are organized into the directory structure as follows:

index.jspWEB-INF   |   - web.xml   - sun-web.xml

The code for web.xml is:

<?xml version="1.0" encoding="UTF-8"?><web-app version="2.4" 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">  <display-name>HelloWebApp</display-name>    <distributable/>  <resource-ref>    <res-ref-name>jdbc/MySQLDataSource</res-ref-name>    <res-type>javax.sql.DataSource</res-type>    <res-auth>Container</res-auth>    <res-sharing-scope>Shareable</res-sharing-scope>                  </resource-ref></web-app>

The code for sun-web.xml is:

<?xml version="1.0" encoding="UTF-8"?><!DOCTYPE sun-web-app PUBLIC "-//Sun Microsystems, Inc.//DTD Application Server 8.1 Servlet 2.4//EN" "http://www.sun.com/software/appserver/dtds/sun-web-app_2_4-1.dtd"><sun-web-app>  <context-root>HelloWebApp</context-root>  <resource-ref>    <res-ref-name>jdbc/MySQLDataSource</res-ref-name>    <jndi-name>jdbc/MySQLDataSource</jndi-name>    </resource-ref> </sun-web-app>

These XML files illustrate a very important aspect of running JDBC applications on Glassfish. On Glassfish it is important to map the string specified for a JDBC resource to its JNDI name, as set up in the Glassfish administration console. In this example, the JNDI name for the JDBC resource, as specified in the Glassfish Administration console when creating the JDBC Resource, was jdbc/MySQLDataSource. This must be mapped to the name given in the application. In this example the name specified in the application, jdbc/MySQLDataSource, and the JNDI name, happen to be the same, but this does not necessarily have to be the case. Note that the XML element <res-ref-name> is used to specify the name as used in the application source code, and this is mapped to the JNDI name specified using the <jndi-name> element, in the file sun-web.xml. The resource also has to be created in the web.xml file, although the mapping of the resource to a JNDI name takes place in the sun-web.xml file.

If you do not have this mapping set up correctly in the XML files you will not be able to lookup the data source using a JNDI lookup string such as:

ds = (DataSource) ctx.lookup("java:comp/env/jdbc/MySQLDataSource");

You will still be able to access the data source directly using:

ds = (DataSource) ctx.lookup("jdbc/MySQLDataSource");

With the source files in place, in the correct directory structure, you are ready to deploy the application:

In the navigation tree, navigate to Applications - the Applications frame will be displayed. Click Deploy.
You can now deploy an application packaged into a single WAR file from a remote client, or you can choose a packaged file or directory that is locally accessible to the server. If you are simply testing an application locally you can simply point Glassfish at the directory that contains your application, without needing to package the application into a WAR file.
Now select the application type from the Type drop-down listbox, which in this example is Web application.
Click OK.

Now, when you navigate to the Applications frame, you will have the option to Launch, Redeploy, or Restart your application. You can test your application by clicking Launch. The application will connection to the MySQL database and display the Name and Population of countries in the Country table.