Getting Started

To get starting using Spring Security's ACL capability, you will need to store your ACL information somewhere. This necessitates the instantiation of a DataSource using Spring. The DataSource is then injected into a JdbcMutableAclService and BasicLookupStrategy instance. The latter provides high-performance ACL retrieval capabilities, and the former provides mutator capabilities. Refer to one of the samples that ship with Spring Security for an example configuration. You'll also need to populate the database with the four ACL-specific tables listed in the last section (refer to the ACL samples for the appropriate SQL statements).

Once you've created the required schema and instantiated JdbcMutableAclService, you'll next need to ensure your domain model supports interoperability with the Spring Security ACL package. Hopefully ObjectIdentityImpl will prove sufficient, as it provides a large number of ways in which it can be used. Most people will have domain objects that contain a public Serializable getId() method. If the return type is long, or compatible with long (eg an int), you will find you need not give further consideration to ObjectIdentity issues. Many parts of the ACL module rely on long identifiers. If you're not using long (or an int, byte etc), there is a very good chance you'll need to reimplement a number of classes. We do not intend to support non-long identifiers in Spring Security's ACL module, as longs are already compatible with all database sequences, the most common identifier data type, and are of sufficient length to accommodate all common usage scenarios.

The following fragment of code shows how to create an Acl, or modify an existing Acl:

// Prepare the information we'd like in our access control entry (ACE)
ObjectIdentity oi = new ObjectIdentityImpl(Foo.class, new Long(44));
Sid sid = new PrincipalSid("Samantha");
Permission p = BasePermission.ADMINISTRATION;

// Create or update the relevant ACL
MutableAcl acl = null;
try {
  acl = (MutableAcl) aclService.readAclById(oi);
} catch (NotFoundException nfe) {
  acl = aclService.createAcl(oi);
}

// Now grant some permissions via an access control entry (ACE)
acl.insertAce(acl.getEntries().length, p, sid, true);
aclService.updateAcl(acl);

In the example above, we're retrieving the ACL associated with the "Foo" domain object with identifier number 44. We're then adding an ACE so that a principal named "Samantha" can "administer" the object. The code fragment is relatively self-explanatory, except the insertAce method. The first argument to the insertAce method is determining at what position in the Acl the new entry will be inserted. In the example above, we're just putting the new ACE at the end of the existing ACEs. The final argument is a boolean indicating whether the ACE is granting or denying. Most of the time it will be granting (true), but if it is denying (false), the permissions are effectively being blocked.

Spring Security does not provide any special integration to automatically create, update or delete ACLs as part of your DAO or repository operations. Instead, you will need to write code like shown above for your individual domain objects. It's worth considering using AOP on your services layer to automatically integrate the ACL information with your services layer operations. We've found this quite an effective approach in the past.

Once you've used the above techniques to store some ACL information in the database, the next step is to actually use the ACL information as part of authorization decision logic. You have a number of choices here. You could write your own AccessDecisionVoter or AfterInvocationProvider that respectively fires before or after a method invocation. Such classes would use AclService to retrieve the relevant ACL and then call Acl.isGranted(Permission[] permission, Sid[] sids, boolean administrativeMode) to decide whether permission is granted or denied. Alternately, you could use our AclEntryVoter, AclEntryAfterInvocationProvider or AclEntryAfterInvocationCollectionFilteringProvider classes. All of these classes provide a declarative-based approach to evaluating ACL information at runtime, freeing you from needing to write any code. Please refer to the sample applications to learn how to use these classes.