LDAP and JNDI

LDAP Server
JNDI Integration

LDAP (Lightweight Directory Access Protocol) is a directory service in which you can store data. The information stored in LDAP is structured in a tree hierarchy and each directory object is called an entry. An entry contains the following components:

DN (Distinguished Name): identifies an entry and consists of single entries names separated by a comma and ordered right-to-left.
Object classes: An object class is the schema of an entry that organizes and determines the content of the entry.
Attributes: contain the actual data.

Entry’s attributes are created like this:

<attributeName>=<attributeValue>

e.g.

cn=Sergio

LDAP Server

Download Apache Directory Studio

Apache Directory Studio association 2.0.0-M15 requires Java 8. Make sure you do not have any other Java version under /Library/Java/JavaVirtualMachines on MacOS.
Go to LDAP Servers tab in the bottom left corner and click on New LDAP Server.
Select latest version and click on Finish.
Create a connection by right clicking on the new LDAP server.
Start up the server.
Now we can go to the LDAP Browser tab.
Import some data

JNDI Integration

LDAP is one of the service providers that comes with JDK out-of-the-box, so you can use the JNDI API to perform operations on LDAP server.

Getting Started

You only need the javaee-api dependency to starting using LDAP with JNDI.

<dependency>
    <groupId>javax</groupId>
    <artifactId>javaee-api</artifactId>
    <version>8.0.1</version>
    <scope>provided</scope>
</dependency>

LDAP Context

The LDAP context can be created as follows:

Properties properties = new Properties();
properties.setProperty(INITIAL_CONTEXT_FACTORY, "com.sun.jndi.ldap.LdapCtxFactory");
properties.setProperty(PROVIDER_URL, "ldap://localhost:10389/dc=example,dc=com");
DirContext context = new InitialDirContext(properties);

The port of LDAP server can be found in Apache Directory Studio.

Organizational Units

You can see all the organizational units with:

Properties properties = new Properties();
properties.setProperty(INITIAL_CONTEXT_FACTORY, "com.sun.jndi.ldap.LdapCtxFactory");
properties.setProperty(PROVIDER_URL, "ldap://localhost:10389/dc=example,dc=com");
DirContext context = new InitialDirContext(properties);

NamingEnumeration<Binding> bindings = context.listBindings("");
while (bindings.hasMoreElements()) {
    System.out.println(bindings.next().getName());
}

Attributes

To access the entries in a organization unit:

Properties properties = new Properties();
properties.setProperty(INITIAL_CONTEXT_FACTORY, "com.sun.jndi.ldap.LdapCtxFactory");
properties.setProperty(PROVIDER_URL, "ldap://localhost:10389/dc=example,dc=com");
DirContext context = new InitialDirContext(properties);

DirContext peopleContext = (DirContext) context.lookup("ou=people");

NamingEnumeration<Binding> people = peopleContext.listBindings("");
while (people.hasMoreElements()) {
    String bindingName = people.next().getName();
    Attributes personAttributes = peopleContext.getAttributes(bindingName);
    Attribute description = personAttributes.get("description");
    Attribute mailsAttribute = personAttributes.get("mail");
    Attribute personName = personAttributes.get("cn");

    NamingEnumeration<?> personNames = personName.getAll();
    System.out.println("Person names:");
    while (personNames.hasMoreElements()) {
        System.out.println(personNames.next());
    }
    System.out.println();

    System.out.printf("Description: %s\n\n", description.get());

    NamingEnumeration<?> mails = mailsAttribute.getAll();
    System.out.println("Mails:");
    while (mails.hasMoreElements()) {
        System.out.println(mails.next());
    }
}

This will print out the following given the example ldif file:

Person names:
Robert Smith
Robert J Smith
bob  smith

Description: swell guy

Mails:
r.smith@example.com
rsmith@example.com
bob.smith@example.com

Examples

Image by Ro Ma from Pixabay

Sergio Martin Rubio