How to extract value from javax.naming.directory.Attribute

The solution is:

Attribute groupCn = attributes.get("cn");
String value = groupCn.get();

Invoke the getValue() method or the getValue(int) method.

General

Let's say that we have:

Attributes attributes;
Attribute a = attributes.get("something");

• if(a.size() == 1)
  • then you can use a.get() or a.get(0) to get the unique value

• if(a.size() > 1)

  • iterate through all the values:

    for ( int i = 0 ; i < a.size() ; i++ ) {
        Object currentVal = a.get(i);
        // do something with currentVal
    }
    

    If you use a.get() here, it will return only the first value, because its internal implementation (in BasicAttribute) looks like this:

    public Object get() throws NamingException {
        if (values.size() == 0) {
            throw new NoSuchElementException("Attribute " + getID() + " has no value");
        } else {
            return values.elementAt(0);
        }
    }
    

Both methods (get(int) and get()) throws a NamingException.

Practical example
(when the Attribute instance has multiple values)

LdapContext ctx = new InitialLdapContext(env, null);

Attributes attributes = ctx.getAttributes("", new String[] { "supportedSASLMechanisms" });
System.out.println(attributes); // {supportedsaslmechanisms=supportedSASLMechanisms: GSSAPI, EXTERNAL, DIGEST-MD5}

Attribute a = atts.get("supportedsaslmechanisms");
System.out.println(a); // supportedSASLMechanisms: GSSAPI, EXTERNAL, DIGEST-MD5

System.out.println(a.get()); // GSSAPI

for (int i = 0; i < a.size(); i++) {
    System.out.print(a.get(i) + " "); // GSSAPI EXTERNAL DIGEST-MD5
}