Exception Handling

[liljester]

Greetings,

Im working on a small project to connect to an ldap server and fetch the attributes of a given dn. Now I have been able to make it work with no user input as its not that difficult and the entire bit of code was in a try/catch. But now i want to add in a basic menu and capture some user input.

Logically (to me) the program can be broken into a few pieces. The first bit i want to handle exceptions for is the initial construction of the DirContext object.. like so:

try {
	DirContext dirCtx = new InitialDirContext(environment);
	System.out.printf("Connected to: %s\n", connectionString);
} catch (NamingException e) {
	System.out.printf("Connection Error: %s\n", e.toString());
}

now if i do it this way, when i try to use dirCtx later in the program NetBeans tells me "variable dirCtx might not have been initialized", and there are compile errors

i have also tried something like this:

DirContext dirCtx;

try {
	dirCtx = new InitialDirContext(environment);
	System.out.printf("Connected to: %s\n", connectionString);
} catch (NamingException e) {
	System.out.printf("Connection Error: %s\n", e.toString());
}

NetBeans tells me the same error, and i get compile errors again.

I'm very new to java, but have extensive experience with php, and even a little c# experience. I know this is probably a very simple problem that im just not seeing the answer to, but i am unable to locate the answer in the java book i have, also ive read the java tutorial on sun's site and still not sure why the way im doing it is wrong.

i guess im looking for a quick explanation why the way im doing it is wrong, and what the proper way to do it is.

full code:

import java.util.*;
import javax.naming.*;
import javax.naming.directory.*;

/**
 *
 * @author Jerry
 */
public class Main {

    public static void main(String[] args) {
		Scanner input = new Scanner(System.in);
		String connectionString = "ldap://192.168.137.8:389/CN=Portal,O=Jenzabar,C=US";
		String userFQDN = "CN=173,OU=PortalUsers,CN=Portal,O=Jenzabar,C=US";
		String userPassword = "password";

		Hashtable environment = new Hashtable();
		//DirContext dirCtx;
		try {
			environment.put(Context.INITIAL_CONTEXT_FACTORY, "com.sun.jndi.ldap.LdapCtxFactory");
			environment.put(Context.PROVIDER_URL, connectionString);
			environment.put(Context.SECURITY_PRINCIPAL,userFQDN);
			environment.put(Context.SECURITY_CREDENTIALS,userPassword);
			DirContext dirCtx = new InitialDirContext(environment);
			System.out.printf("Connected to: %s\n", connectionString);
		} catch(NamingException e) {
			System.out.printf("Connection Error: %s\n", e.toString());
		}

		System.out.println("What would you like to do? (enter a number)");
		System.out.println("1 - Print Attributes of DN");
		String command = input.next();

		if(command.equals("1")) {
			System.out.print("Enter DN:");
			String dn = input.next();
			printAttributes(dirCtx, dn);
		}



    }

	public static void printAttributes(DirContext dirCtx, String dn) {
		try {
			Attributes userAttributes = dirCtx.getAttributes(dn);
			int i = 0;
			for(NamingEnumeration allAttribs = userAttributes.getAll(); allAttribs.hasMore();) {
				Attribute thisAttrib = (Attribute)allAttribs.next();
				System.out.printf("%s: ", thisAttrib.getID());

				for(NamingEnumeration value = thisAttrib.getAll(); value.hasMore();) {
					if(i == 0) {
						System.out.printf("%s", value.next());
					} else {
						System.out.printf(", %s", value.next());
					}

					i++;
				}
				System.out.println();
				i = 0;
			}
		} catch (NamingException e) {
			System.out.printf("Error Fetching Attributes for '%s': %s\n", dn, e.toString());
		}
	}

}

Thanks!

[Norm]

DirContext dirCtx;

This defines the variable but does NOT assign it any value. Because you need to define the variable outside the scope of the try{} block, you can do this to give it a value:
DirContext dirCtx = null;

[liljester]

norm,

i was hoping it was something easy like that!

Thank you so much!

[Tolls]

		DirContext dirCtx = null;  // I filled this in based on Norms post.
		try {
		    // Get the dirCtxt.
		} catch(NamingException e) {
			System.out.printf("Connection Error: %s\n", e.toString());
		}

		System.out.println("What would you like to do? (enter a number)");
		System.out.println("1 - Print Attributes of DN");
		String command = input.next();

		if(command.equals("1")) {
			System.out.print("Enter DN:");
			String dn = input.next();
			printAttributes(dirCtx, dn);
		}
    }

You've got yourself a bug here. If the lookup for the context fails you still merrily continue on, albeit with a small message on the screen. This will result in a null pointer exception (since dirCtx is null) in printAttributes.

Since you cannot do anything in this program without a valid dirCtx this is one of those situations you want to crash. That is throw the NamingException.

[liljester]

Tolls,

Thank you for pointing that out. I should be able to change the flow of the program to take into account a null context.

Thanks!