jndi - Initialcontext in a standalone Java program

Question

I'm using a JNDI for creating connection pool. It works great in a web application. I believe the InitialContext is provided by the tomcat server.

Context initContext  = new InitialContext();
Context envContext  = (Context)initContext.lookup("java:/comp/env");
dataSource = (DataSource)envContext.lookup("jdbc/testdb");

But when I try to call the same utility from a standalone Java program, the initContext object is null. How can I explicitly provide all the necessary properties that Context object is expecting.

Error : javax.naming.NoInitialContextException: Need to specify class name in environment or system property, or as an applet parameter, or in an application resource file: java.naming.factory.initial

Answer 1

Here is an example adapted from the accepted answer but doing everything inline to avoid creating extra classes.

public static void main(String[] args) {
    setupInitialContext();
    //do something that looks up a datasource
}

private static void setupInitialContext() {
    try {
        NamingManager.setInitialContextFactoryBuilder(new InitialContextFactoryBuilder() {

            @Override
            public InitialContextFactory createInitialContextFactory(Hashtable<?, ?> environment) throws NamingException {
                return new InitialContextFactory() {

                    @Override
                    public Context getInitialContext(Hashtable<?, ?> environment) throws NamingException {
                        return new InitialContext(){

                            private Hashtable<String, DataSource> dataSources = new Hashtable<>();

                            @Override
                            public Object lookup(String name) throws NamingException {

                                if (dataSources.isEmpty()) { //init datasources
                                    MysqlConnectionPoolDataSource ds = new MysqlConnectionPoolDataSource();
                                    ds.setURL("jdbc:mysql://localhost:3306/mydb");
                                    ds.setUser("mydbuser");
                                    ds.setPassword("mydbpass");
                                    dataSources.put("jdbc/mydbname", ds);

                                    //add more datasources to the list as necessary
                                }

                                if (dataSources.containsKey(name)) {
                                    return dataSources.get(name);
                                }

                                throw new NamingException("Unable to find datasource: "+name);
                            }
                        };
                    }

                };
            }

        });
    }
    catch (NamingException ne) {
        ne.printStackTrace();
    }
}