A Java geek

Tomcat manages application security through the concept of realm. A realm is a coherent package of name password pairs that identify valid users for a web application.

Tomcat’s default realm is MemoryRealm. This realm reads the famous conf/tomcat-users.xml file and uses it check for name password pair validity. Tomcat also provides realms to check against pairs stored in a database, either through a direct connection, or through a configured datasource. The main disadvantage of these all these realms is that they force you to adopt Tomcat’ expected data structure. In most organizations, these constraints will be enough for the architect to rely upon custom or 3rd-party security components.

In order to use your enterprise database structure, you would code a custom realm. Tomcat provides the org.apache.catalina.Realm interface. The drawback of implementing your own realm is that if you change your application server afterwards, all of your code would have been for naught. Yet, if you check Tomcat documentation thoroughly, you will see Tomcat also provides a JAASRealm. JAAS is the Java security feature and enable you to write custom security modules in a portable way. Tomcat’s JAASRealm performs as a adapter between realms and login modules so you only have to write a LoginModule and Tomcat will know how and when to call it. Read more…