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Software Engineering

Software Engineering. Recitation 6 Suhit Gupta. Review. Classpath Stream vs. Reader. Today. LDAP. LDAP. Lightweight Directory Access Protocol. Snapshot of UT. LDAP – support is wide. What is LDAP.

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Software Engineering

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  1. Software Engineering Recitation 6 Suhit Gupta

  2. Review • Classpath • Stream vs. Reader

  3. Today • LDAP

  4. LDAP • Lightweight Directory Access Protocol

  5. Snapshot of UT

  6. LDAP – support is wide

  7. 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.

  8. 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

  9. 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.

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

  11. Some notation • cn • ou • dc • o • dn

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

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

  14. 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.

  15. Schema • Janak has explicitly created three for you • Service • Actor • ActorState

  16. 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

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

  18. 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

  19. 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

  20. 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

  21. 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

  22. 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

  23. 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

  24. 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

  25. The receive code • Update to new version, Suhit

  26. 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 <LDAP server>: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 + "-------"); }}}

  27. The send code • Update to new version, Suhit

  28. 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 <LDAP server:port> <ServerRef> <ServerIP> <ServerPort> <ServerType>"); 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!"); }}

  29. 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

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