CODEWITHSUNDEEP
java
Karen Goh
Karen Goh

Reputation: 184

How do I call the Config.java in my servlet?

I've been trying really hard to figure out how to bring in this database connection into my servlet, but failed, and hence this posting here.

Basically, I am using this code which I found my this site - one that is taught by BalusC.

public class Config implements ServletContextListener {
    private static final String ATTRIBUTE_NAME = "config";
    private DataSource dataSource;

    @Override
    public void contextInitialized(ServletContextEvent event) {
        ServletContext servletContext = event.getServletContext();
        String databaseName = servletContext.getInitParameter("pract1");
        try {
            dataSource = (DataSource) new InitialContext().lookup("java:/comp/env/jdbc/TestDB");  
        } catch (NamingException e) {
            throw new RuntimeException("Config failed: datasource not found", e);
        }
    }

    @Override
    public void contextDestroyed(ServletContextEvent event) {
        System.out.println("contextDestroyed....");
    }

    public DataSource getDataSource() {
        return dataSource;
    }

    public static Config getInstance(ServletContext servletContext) {
        return (Config) servletContext.getAttribute(ATTRIBUTE_NAME);
    }
}

He explained that you have this class and the connection will start once for all the servlets, so I thought it's a good practice to do it.

Now, my problem is that I do not know how to bring the database connection which is set up in the Config, the context.xml file, etc. to work in the servlet.

Here's what I have attempted but it is not working out:

Connection con = null;
Config a = new Config();
con = (Connection) a.getDataSource();
DBConnect dbConnect = new DBConnect();
con = dbConnect.getConnection();                        

stmt = con.createStatement();                   
rs = stmt.executeQuery("SELECT * FROM members");

I hope someone can tell me how to bring the connection into my doPost Servlet.

Upvotes: 0

Views: 136

Answers (3)

stepanian
stepanian

Reputation: 11433

Use this: 

 Connection con = ((DataSource) a.getDataSource()).getConnection();

Instead of this: 

 Connection con = null;
 con = (Connection) a.getDataSource();
 DBConnect dbConnect = new DBConnect();
 con = dbConnect.getConnection();

Assuming that you have set: 

Config a = Config.getInstance(request.getServletContext());

Upvotes: 0

Vimal Bera
Vimal Bera

Reputation: 10497

Better way to use the connection created in ServletContextListner is by setting it as a attribute in ServletContext like this :

event.getServletContext().setAttribute("connection_name", connection_object);

After this, you can use this connection_object in any servlet like this :

connection_object = config.getServletContext().getAttribute("connection_name");

Upvotes: 1

Prabhakaran Ramaswamy
Prabhakaran Ramaswamy

Reputation: 26094

Your casting datasource to Connection 

     Connection con = null;
     con = (Connection) a.getDataSource();

Please change to 

     DataSource dataSource= null;
     dataSource = (DataSource) a.getDataSource(); // Your casting datasource to Connection 

     //get the connection from datasource

     if (dataSource!= null) {
        con = dataSource.getConnection();
     }
     if (con!= null) {
       stmt = con.createStatement();                   
       rs = stmt.executeQuery("SELECT * FROM members"); 
     }

Upvotes: 0

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