Re: Servlet init

From:

Andy Flowers <no.way@hose.com>

Newsgroups:

comp.lang.java.programmer,comp.lang.java.help

Date:

Thu, 15 Jun 2006 19:18:10 GMT

Message-ID:

<Snikg.19546$n13.15102@newsfe2-win.ntli.net>

Sameer wrote:

The init method for a servlet is as follows:

public void init(){
        try {
            Class.forName("sun.jdbc.odbc.JdbcOdbcDriver");
            connection =
DriverManager.getConnection("jdbc:odbc:library");
        } catch(ClassNotFoundException cnfe) {
            System.err.println("Error loading driver: " + cnfe);
        } catch (SQLException ex) {
            ex.printStackTrace();
        }
    }

The Stack Trace does not print in the browser and we also do not have
access to HttpServletResponse object.
Then how it is possible to display an error message in the client's
browser if database connection fails?

Once you have found an error you can set a class level variable, or an
application level attribute, with details of the failure.

For example you might have a boolean flag to indicate success/failure of the
database connection, and a string for the message. These could be used at the
start of requests.

Alternatively you could look into using the DataSource interface, and connection
pools, supported by J2EE.

See http://java.sun.com/j2ee/1.4/docs/tutorial/doc/Resources3.html#wp80235 for
some details.

Here's a snippet to point you to areas to search for

Context initContext = new InitialContext();
Context envContext = (Context)initContext.lookup("java:/comp/env");
DataSource ds = (DataSource)envContext.lookup("jdbc/myoracle");
Connection conn = ds.getConnection();
.....

These are then used on a per call basis and make it easier to get shared
connections from a pool, and make it easier to detect problems.