Exception Handling

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:

Code:

---

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:

Code:

---

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:

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!

Quote:

---

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;

norm,

i was hoping it was something easy like that!

Thank you so much!

Code:

---

                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.

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!