引起：java.net.UnknownHostException：www.btechldap.com

Question

I am trying to access LDAP Server through Java code as I have founded a free hosted server on the internet and want to test the reading mechanism via LDAP. But when I access it I get the captioned exception.

I have surfed on the internet and found that the LDAP URL Format shall be as per the correct practice and standard. I fixed that too, but nothing worked.

I dont know where I have done a mistake.

The complete stack trace is provided below:

Exception

Rdentry example failed.
javax.naming.CommunicationException: www.btechldap.com:1389 [Root exception is java.net.UnknownHostException: www.btechldap.com]
    at com.sun.jndi.ldap.Connection.<init>(Unknown Source)
    at com.sun.jndi.ldap.LdapClient.<init>(Unknown Source)
    at com.sun.jndi.ldap.LdapClient.getInstance(Unknown Source)
    at com.sun.jndi.ldap.LdapCtx.connect(Unknown Source)
    at com.sun.jndi.ldap.LdapCtx.<init>(Unknown Source)
    at com.sun.jndi.ldap.LdapCtxFactory.getUsingURL(Unknown Source)
    at com.sun.jndi.ldap.LdapCtxFactory.getUsingURLs(Unknown Source)
    at com.sun.jndi.ldap.LdapCtxFactory.getLdapCtxInstance(Unknown Source)
    at com.sun.jndi.ldap.LdapCtxFactory.getInitialContext(Unknown Source)
    at javax.naming.spi.NamingManager.getInitialContext(Unknown Source)
    at javax.naming.InitialContext.getDefaultInitCtx(Unknown Source)
    at javax.naming.InitialContext.init(Unknown Source)
    at javax.naming.InitialContext.<init>(Unknown Source)
    at javax.naming.directory.InitialDirContext.<init>(Unknown Source)
    at LDAPAccess.main(LDAPAccess.java:33)
Caused by: java.net.UnknownHostException: www.btechldap.com
    at java.net.AbstractPlainSocketImpl.connect(Unknown Source)
    at java.net.PlainSocketImpl.connect(Unknown Source)
    at java.net.SocksSocketImpl.connect(Unknown Source)
    at java.net.Socket.connect(Unknown Source)
    at java.net.Socket.connect(Unknown Source)
    at java.net.Socket.<init>(Unknown Source)
    at java.net.Socket.<init>(Unknown Source)
    at com.sun.jndi.ldap.Connection.createSocket(Unknown Source)
    ... 15 more

CODE

import java.util.Hashtable;

import javax.naming.Context;
import javax.naming.NamingEnumeration;
import javax.naming.NamingException;
import javax.naming.directory.Attribute;
import javax.naming.directory.Attributes;
import javax.naming.directory.DirContext;
import javax.naming.directory.InitialDirContext;

public class LDAPAccess {

    public static void main(String[] args) {
        Hashtable env = new Hashtable(5, 0.75f);
        /*
         * Specify the initial context implementation to use.
         * This could also be set by using the -D option to the java program.
         * For example,
         *   java -Djava.naming.factory.initial=com.sun.jndi.ldap.LdapCtxFactory \
         *       Rdentry
         */
        env.put(Context.INITIAL_CONTEXT_FACTORY, "com.sun.jndi.ldap.LdapCtxFactory");
        /* Specify host and port to use for directory service */
        env.put(Context.PROVIDER_URL, "ldap://www.btechldap.com:1389/dc=btechsample,dc=com");
        env.put(Context.SECURITY_AUTHENTICATION, "simple");
        env.put(Context.SECURITY_CREDENTIALS, "btechpass");
        try {
            /* get a handle to an Initial DirContext */
            DirContext ctx = new InitialDirContext(env);
            /* Read Babs' entry */
            Attributes attrs = ctx.getAttributes("uid");
            if (attrs == null) {
                System.out.println("uid" + "has no attributes");
            } else {
                /* print each attribute */
                for (NamingEnumeration ae = attrs.getAll();
                     ae.hasMoreElements();) {
                    Attribute attr = (Attribute)ae.next();
                    String attrId = attr.getID();
                    /* print each value */
                    for (NamingEnumeration vals = attr.getAll();
                         vals.hasMoreElements();
                         System.out.println(attrId + ": " + vals.nextElement()))
                        ;
                }
            }
        } catch (NamingException e) {
            System.err.println("Rdentry example failed.");
            e.printStackTrace();
        }
    }
}

I am new to LDAP, Please help!

Answer 1

The code is specifying the credentials (password) but missing the principal (ie the user to authenticate as). Just add the following line:

env.put(Context.SECURITY_PRINCIPAL, "cn=readonlybind,ou=admins,dc=btechsample,dc=com");