Best way to store Database configuration parameters? - gwt

Question

I'm developing a web application at the moment. The web application needs to access a Patients database, which for now is a simple MySQL database but may likely be replaced by some other DB (or data source) in the future. At the moment, everything is hardcoded but I would like to have some way to configure the DB connection (that is, the database URL, user, password etc.).
What would be a simple and straightforward solution? It would be good if I could change the configuration by simple editing of a file.
I've seen there's the Properties API as well as Preferences. Or is there some idiom concerning servlets/web apps?

Answer 1

A servlet is part of a web app, and this web app is deployed in a Java EE container (Tomcat, WebLogic, etc.).
The standard way to get a database connection is to use JNDI to get a DataSource instance, and to ask a connection to this DataSource. The DataSource, most of the time, will pool database connections to avoid creating and closing too many connections and thus be much faster :
Context initCtx = new InitialContext();
DataSource dataSource = (DataSource) initCtx.lookup("java:comp/env/jdbc/MyDataSource");
Connection c = dataSource.getConnection();
try {
// ...
}
finally {
c.close(); // makes the connection available for a new thread
}
The DataSource will have to be declared in the web.xml file:
<resource-ref>
<description>Datasource example</description>
<res-ref-name>jdbc/MyDataSource</res-ref-name>
<res-type>javax.sql.DataSource</res-type>
<res-auth>Container</res-auth>
</resource-ref>
It will have to be defined (with its URL, number of connections, user, password, settings, etc.) inside your Java EE container. This is where it depends on your container.
Read the following explanations for Tomcat : http://tomcat.apache.org/tomcat-7.0-doc/jndi-datasource-examples-howto.html

Answer 2

I think a configuration XML along with your web application is a good idea. Each time the application is initiated by a new request the configuration is loaded and the database connection information available from any internal context that you make.
On IIS this is a standard way through the Web.config file.
regards