In today's e-business environment, effective and efficient data management is crucial. As such, two technologies prove vital to proper data management: directory services and XML. Directory services allow you to store and manage data, and are thus a necessary prerequisite for conducting online business. XML provides an effective way to present and transfer data. With that in mind, there's a clear need to bridge the two technologies. The solution may be the new Directory Service Markup Language (DSML) standard, designed to make directory services more dynamic by employing XML.
DSML, in conjunction with technologies like XSL and EJB, provides a unique way to solve many business problems, such as supply chain management and customer support. The technology was developed out of work done by Bowstreet and completed by the DSML Working Group; the latter submitted the technology to the W3C and OASIS standards groups in December 1999.
Numerous products now support DSML, including Sun's recently released DSML Service Provider 1.2 technology, released for use with J2EE 1.2, and Exolab's Castor API, which provides services to extract information from LDAP as DSML, as well as . With the DSML Service Provider, which implements the
javax.naming.directory.DirContext interface, you can access a DSML document, manipulate and update its contents by using the JNDI APIs, and then re-export the contents in DSML format.
In this article, we will discuss how to create dynamic content and manipulate a directory server with DSML. We will do this using Exolab's Castor, servlets, and XSL. We will not cover information on how to use XSL or servlets, but for more information you can refer to Michael Ball's earlier article, "XSL Gives Your XML Some Style" (JavaWorld, June 30, 2000).
Download the source code associated with this article.
The DSML specification
The DSML specification provides both a DTD and a schema for reference (see Resources for download information).
The DSML namespace is:
http://www.dsml.org/DSML; it should be referenced in all your DSML documents, as in:
A DSML document can describe directory entries, a directory structure, or both. The root node in a DSML document is always
dsml. Children can be
<dsml:dsml xmlns:dsml=http://www.dsml.org/DSML> <dsml:directory-schema> ... </dsml:directory-schema> <dsml:directory-entries> ... </dsml:directory-entries> </dsml>
directory-entries node has one or more
directory-entry nodes as its children. Each of these
directory-entry nodes contains the object class information as well as attributes for the information, as seen below:
<dsml:directory-entries> <dsml:directory-entry dn="uid=mball, ou=consultant, o=sark.com,c=us"> <dsml:objectclass> <dsml:oc-value>top</dsml:oc-value> <dsml:oc-value>person</dsml:oc-value> <dsml:oc-value>organizationalPerson</dsml:oc-value> <dsml:oc-value>inetOrgPerson</dsml:oc-value> </dsml:objectclass> <dsml:attr name="sn"><dsml:value>Ball</dsml:value></dsml:attr> <dsml:attr name="uid"><dsml:value>mball</dsml:value></dsml:attr> <dsml:attr name="mail"><dsml:value>email@example.com</dsml:value></dsml:attr> <dsml:attr name="givenname"><dsml:value>Michael</dsml:value></dsml:attr> <dsml:attr name="cn"><dsml:value>Michael Ball</dsml:value></dsml:attr> </dsml:entry> </dsml:directory-entries>
If an attribute is multivalued, there would be many
<dsml:value> nodes under the
directory-schema node contains information about the object classes and the attributes. As an example, take a look at this sample XML pulled from the DSML specification:
<dsml: class id="person" superior="#top" type="structural"> <dsml:name>person</dsml:name> <dsml:description>...</dsml:description> <dsml:object-identifier>126.96.36.199</object-identifier> <dsml:attribute ref="#sn" required="true"/> <dsml:attribute ref="#cn" required="true"/> <dsml:attribute ref="#userPassword" required="false"/> <dsml:attribute ref="#telephoneNumber" required="false"/> <dsml:attribute ref="#seeAlso" required="false"/> <dsml:attribute ref="#description" required="false"/> </dsml:class>
Using DSML with Exolab's Castor API
Exolab, according to its homepage, works on the development of open source enterprise software projects, of which the Castor API is one. DSML is a subset of Castor. Be aware that the documentation for the DSML portion of Castor is scarce. With that in mind, we'll try to highlight the basic functionality of the API.
Note: In this article, we used Castor version 0.8.5.
Castor's DSML API
Castor can import and export directory information. Meanwhile, the DSML specification describes producers (used for exporting) and consumers (used for importing). Both of these services are divided into types 1 and 2 based on the document levels that they can handle. The four document levels are:
- Level 1: A document containing no schema information, just directory entries
- Level 2: A document containing directory entry information and a link to an external schema
- Level 3: A document containing only a directory schema
- Level 4: A document containing a directory schema and directory entries
A type 1 producer can handle the level 1 documents, while a type 2 producer can handle document levels 2, 3, and 4.
Meanwhile, a type 1 consumer must handle all four document levels. A type 2 consumer must handle all four document levels and make use of schema information.
Castor supports type 1 producers and consumers.
Castor can provide level 1 and level 4 documents. The class
org.exolab.castor.dsml.Exporter retrieves directory information from a directory server.
Exporter class uses a
org.exolab.castor.dsml.SearchDescriptor to define search parameters. The
SearchDescriptor can be configured by calling setters on it. Table 1 defines some of the important methods available in the