19.1.3 Custom Access Control

The JdmkAcl class that relies on an ACL file is the default access control mechanism in the SNMP adaptor. For greater adaptability, the SnmpAdaptorServer class has constructors that let you specify your own access control mechanism. For example, if your agent runs on a device with no file system, you could implement a mechanism that does not rely on the jdmk.acl file.

To instantiate an SNMP adaptor with your own access control, use one of the constructors that takes an acl parameter of the type InetAddressAcl. Note that if this parameter's value is null, or if you use a constructor that does not specify an acl parameter, the SNMP adaptor will use the JdmkAcl class by default. If you want to instantiate an SNMP adaptor without access control, call the constructor with the useAcl parameter set to false.

Your access control mechanism must be a class that implements the InetAddressAcl interface. This interface specifies the methods that the SNMP adaptor uses to check permissions when processing a request. If you instantiate the SNMP adaptor with your access control class, the adaptor will call your implementation of the access control methods. Again, for security reasons, the InetAddressAcl implementation in use cannot be changed once the SNMP adaptor has been instantiated.

The JdmkAcl class implements the default access mechanism that uses the jdmk.acl file. It is also an implementation of the InetAddressAcl interface, and it provides a few other methods, such as rereadTheFile, to control the InetAddressAcl mechanism.