Software Engineering Recitation 6 Suhit Gupta

Review Classpath Stream vs. Reader

Today LDAP

Lightweight Directory Access Protocol

Snapshot of UT

LDAP – support is wide

What is LDAP Lightweight Directory Access Protocol – A cross platform protocol for communicating with a directory server It has descended from the X.500 OSI Directory Access protocol – which was too cumbersome for microcomputers It is a data representation model optimized for arbitrary queries.

What is a directory? A centralized structured hierarchical repository of configuration, authentication and other network and systems related information. Eg - /etc/passwd, /etc/shadow It is a system optimized for a predominantly “lookup” application. It is not a database –No transactions –Not relations –Poor Update/Insert/Delete Operations

So why are we using it? A centralized cross-platform data repository greatly simplifies administration Replication support increases availability Distribution of information can reduce network load on critical segments Front-ends such as www to LDAP in conjunction with well designed access controls can place some administration tasks in the hands of the users themselves.

Why LDAP? Both NDS and MSFT-AD are LDAP servers LDAP is open, and will inter-operate with other directories It is simple

Some notation cn ou dc o dn

What the structure looks like… O=softe Ou=services Ou=actors Ou=states

However… It’s really a flat db There really isn’t this tree like structure But we don’t care

What is a schema? The schema describes the structure of the directory contents. Schemas are optional but you usually want them. The schema describes the datatype of each attribute. The schema specifies the attribute found in each object class.

Schema Janak has explicitly created three for you –Service –Actor –ActorState

Service Service reference ID: CN tag in DN: use your group ID Required: –ServerIP (string) –ServerPort (int) –ServerType (string): A or S Optional –WorldName –Extensions

Actor Actor “name”/login id: CN tag in DN Required: –HP: int –XP: int –Gold: int –Password: String Optional: –ImageURL

ActorState CN in DN: unique identifier –We’ll use combination of actor, world, and service –“ac=actorname+wn=worldname+sv=servicename” Required –LocationX: int –LocationY: int –Status: int –WorldInstance: int

JNDI Relatively simple Java API, built into 1.3 and higher Actually more than LDAP: DNS, etc. For LDAP, uses concept of directory context in which the operation will be done –ldap://softe.cs.columbia.edu:389/o=softe Once set, go ahead and do operation

JNDI Lookups getAttributes() method searches by (unique) DN –similar to lookup() but more powerful Returns Attributes object: collection of attribute-value pairs; you can “get” and “put”, like a Hashtable

JNDI Searches search() searches within a DN for all entries that match the Attributes set you provide –list() finds all in the DN context Returns NamingEnumeration (subinterface of Enumeration) –Each entry in the Enumeration is a SearchResult, which you can convert toString() and then do a lookup –For list(), returns a NameClassPair Example

JNDI Writes Just like we can getAttributes(), we can… (re)bind() –Ok, so the parallel isn’t ideal –Name: DN –Object: null (Java can serialize to LDAP!) –Attributes: our good friend Example

JNDI Deletes unbind(); Must supply whole DN to it –Use search() if you don’t know what the full DN of the relevant object is

JNDI Miscellany Name class –You don’t have to use this: it’s a bit more “civilized” way of dealing with DN’s, though –For the scope of this class, it’s acceptable just to use Strings for DN’s

The receive code Update to new version, Suhit

import javax.naming.*; import javax.naming.directory.*; import java.util.*; public class SearchForServices { public static void main(String[] args) { if(args.length != 1) { System.out.println("usage: java SearchForServices :port"); System.exit(-1); } // Create the environment in which we will do lookups Hashtable env = new Hashtable(); env.put(Context.INITIAL_CONTEXT_FACTORY, "com.sun.jndi.ldap.LdapCtxFactory"); env.put(Context.PROVIDER_URL, "ldap://" + args[0] + "/dc=softe,dc=cs,dc=columbia,dc=edu"); // Now connect and perform the list request DirContext ctx = null; NamingEnumeration ne = null; try { ctx = new InitialDirContext(env); ne = ctx.list("ou=services"); } catch(NamingException e) { e.printStackTrace(); } // Now list all services while(ne.hasMoreElements()) { NameClassPair ncp = (NameClassPair)ne.nextElement(); System.out.println("Found " + ncp + "; attributes are:"); // Lookup this element Attributes a = null; try { a = ctx.getAttributes(ncp.getName() + ",ou=services"); } catch(NamingException e) { e.printStackTrace(); } // Print out the set of attributes System.out.println(a + " "); }}}

The send code Update to new version, Suhit

import javax.naming.*; import javax.naming.directory.*; import java.util.*; public class AddService { public static void main(String[] args) { if(args.length != 5) { System.out.println("usage: java AddService "); System.exit(-1); } // Create the environment in which we will do binds Hashtable env = new Hashtable(); env.put(Context.INITIAL_CONTEXT_FACTORY, "com.sun.jndi.ldap.LdapCtxFactory"); env.put(Context.PROVIDER_URL, "ldap://" + args[0] + "/o=softe"); env.put(Context.SECURITY_PRINCIPAL, "cn=Manager,o=softe"); env.put(Context.SECURITY_CREDENTIALS, "cs3156"); // Now connect and perform the list request DirContext ctx = null; NamingEnumeration ne = null; try { ctx = new InitialDirContext(env); // Create the attributes Attributes a = new BasicAttributes(); a.put("objectClass", "Service"); a.put("ServerIP", args[2]); a.put("ServerPort", args[3]); a.put("ServerType", args[4]); ctx.bind("cn=" + args[1] + ",ou=services",null,a); } catch(NamingException e) { e.printStackTrace(); } System.out.println("Done!"); }}

Where does our LDAP server exist?? liberty.psl.cs.columbia.edu (but we call it softe.cs.columbia.edu) We shall give you the username/password etc. on the webpage in the next few days We will also update the requirement field names