xref:servlet/authentication/architecture.adoc#servlet-authentication-authentication[`Authentication`] discusses how all `Authentication` implementations store a list of `GrantedAuthority` objects.
The `GrantedAuthority` objects are inserted into the `Authentication` object by the `AuthenticationManager` and are later read by `AccessDecisionManager` instances when making authorization decisions.
`AuthorizationManager` instance to obtain a precise `String` representation of the `GrantedAuthority`.
By returning a representation as a `String`, a `GrantedAuthority` can be easily "read" by most `AuthorizationManager` implementations.
If a `GrantedAuthority` cannot be precisely represented as a `String`, the `GrantedAuthority` is considered "complex" and `getAuthority()` must return `null`.
An example of a complex `GrantedAuthority` would be an implementation that stores a list of operations and authority thresholds that apply to different customer account numbers.
By default, role-based authorization rules include `ROLE_` as a prefix.
This means that if there is an authorization rule that requires a security context to have a role of "USER", Spring Security will by default look for a `GrantedAuthority#getAuthority` that returns "ROLE_USER".
You can customize this with `GrantedAuthorityDefaults`.
`GrantedAuthorityDefaults` exists to allow customizing the prefix to use for role-based authorization rules.
You can configure the authorization rules to use a different prefix by exposing a `GrantedAuthorityDefaults` bean, like so:
You expose `GrantedAuthorityDefaults` using a `static` method to ensure that Spring publishes it before it initializes Spring Security's method security `@Configuration` classes
`AuthorizationManager` supersedes both <<authz-legacy-note,`AccessDecisionManager` and `AccessDecisionVoter`>>.
Applications that customize an `AccessDecisionManager` or `AccessDecisionVoter` are encouraged to <<authz-voter-adaptation,change to using `AuthorizationManager`>>.
``AuthorizationManager``s are called by Spring Security's xref:servlet/authorization/authorize-http-requests.adoc[request-based], xref:servlet/authorization/method-security.adoc[method-based], and xref:servlet/integrations/websocket.adoc[message-based] authorization components and are responsible for making final access control decisions.
The ``AuthorizationManager``'s `check` method is passed all the relevant information it needs in order to make an authorization decision.
In particular, passing the secure `Object` enables those arguments contained in the actual secure object invocation to be inspected.
For example, let's assume the secure object was a `MethodInvocation`.
It would be easy to query the `MethodInvocation` for any `Customer` argument, and then implement some sort of security logic in the `AuthorizationManager` to ensure the principal is permitted to operate on that customer.
Implementations are expected to return a positive `AuthorizationDecision` if access is granted, negative `AuthorizationDecision` if access is denied, and a null `AuthorizationDecision` when abstaining from making a decision.
`verify` calls `check` and subsequently throws an `AccessDeniedException` in the case of a negative `AuthorizationDecision`.
Whilst users can implement their own `AuthorizationManager` to control all aspects of authorization, Spring Security ships with a delegating `AuthorizationManager` that can collaborate with individual ``AuthorizationManager``s.
`RequestMatcherDelegatingAuthorizationManager` will match the request with the most appropriate delegate `AuthorizationManager`.
For method security, you can use `AuthorizationManagerBeforeMethodInterceptor` and `AuthorizationManagerAfterMethodInterceptor`.
<<authz-authorization-manager-implementations>> illustrates the relevant classes.
[[authz-authorization-manager-implementations]]
.Authorization Manager Implementations
image::{figures}/authorizationhierarchy.png[]
Using this approach, a composition of `AuthorizationManager` implementations can be polled on an authorization decision.
[[authz-authority-authorization-manager]]
==== AuthorityAuthorizationManager
The most common `AuthorizationManager` provided with Spring Security is `AuthorityAuthorizationManager`.
It is configured with a given set of authorities to look for on the current `Authentication`.
It will return positive `AuthorizationDecision` should the `Authentication` contain any of the configured authorities.
It will return a negative `AuthorizationDecision` otherwise.
[[authz-authenticated-authorization-manager]]
==== AuthenticatedAuthorizationManager
Another manager is the `AuthenticatedAuthorizationManager`.
It can be used to differentiate between anonymous, fully-authenticated and remember-me authenticated users.
Many sites allow certain limited access under remember-me authentication, but require a user to confirm their identity by logging in for full access.
There are also helpful static factories in {security-api-url}org/springframework/security/authorization/AuthorizationManagers.html[`AuthorizationManagers`] for composing individual ``AuthorizationManager``s into more sophisticated expressions.
Obviously, you can also implement a custom `AuthorizationManager` and you can put just about any access-control logic you want in it.
It might be specific to your application (business-logic related) or it might implement some security administration logic.
For example, you can create an implementation that can query Open Policy Agent or your own authorization database.
[TIP]
You'll find a https://spring.io/blog/2009/01/03/spring-security-customization-part-2-adjusting-secured-session-in-real-time[blog article] on the Spring web site which describes how to use the legacy `AccessDecisionVoter` to deny access in real-time to users whose accounts have been suspended.
You can achieve the same outcome by implementing `AuthorizationManager` instead.
[[authz-voter-adaptation]]
== Adapting AccessDecisionManager and AccessDecisionVoters
Previous to `AuthorizationManager`, Spring Security published <<authz-legacy-note,`AccessDecisionManager` and `AccessDecisionVoter`>>.
In some cases, like migrating an older application, it may be desirable to introduce an `AuthorizationManager` that invokes an `AccessDecisionManager` or `AccessDecisionVoter`.
To call an existing `AccessDecisionManager`, you can do:
It is a common requirement that a particular role in an application should automatically "include" other roles.
For example, in an application which has the concept of an "admin" and a "user" role, you may want an admin to be able to do everything a normal user can.
To achieve this, you can either make sure that all admin users are also assigned the "user" role.
Alternatively, you can modify every access constraint which requires the "user" role to also include the "admin" role.
This can get quite complicated if you have a lot of different roles in your application.
The use of a role-hierarchy allows you to configure which roles (or authorities) should include others.
This is supported for filter-based authorization in `HttpSecurity#authorizeHttpRequests` and for method-based authorization through `DefaultMethodSecurityExpressionHandler` for pre-post annotations, `SecuredAuthorizationManager` for `@Secured`, and `Jsr250AuthorizationManager` for JSR-250 annotations.
You can configure the behavior for all of them at once in the following way:
A user who is authenticated with `ROLE_ADMIN`, will behave as if they have all four roles when security constraints are evaluated against any filter- or method-based rules.
The `>` symbol can be thought of as meaning "includes".
Role hierarchies offer a convenient means of simplifying the access-control configuration data for your application and/or reducing the number of authorities which you need to assign to a user.
For more complex requirements you may wish to define a logical mapping between the specific access-rights your application requires and the roles that are assigned to users, translating between the two when loading the user information.
[[authz-legacy-note]]
== Legacy Authorization Components
[NOTE]
Spring Security contains some legacy components.
Since they are not yet removed, documentation is included for historical purposes.
The `decide` method of the `AccessDecisionManager` is passed all the relevant information it needs to make an authorization decision.
In particular, passing the secure `Object` lets those arguments contained in the actual secure object invocation be inspected.
For example, assume the secure object is a `MethodInvocation`.
You can query the `MethodInvocation` for any `Customer` argument and then implement some sort of security logic in the `AccessDecisionManager` to ensure the principal is permitted to operate on that customer.
Implementations are expected to throw an `AccessDeniedException` if access is denied.
The `supports(ConfigAttribute)` method is called by the `AbstractSecurityInterceptor` at startup time to determine if the `AccessDecisionManager` can process the passed `ConfigAttribute`.
The `supports(Class)` method is called by a security interceptor implementation to ensure the configured `AccessDecisionManager` supports the type of secure object that the security interceptor presents.
While users can implement their own `AccessDecisionManager` to control all aspects of authorization, Spring Security includes several `AccessDecisionManager` implementations that are based on voting.
<<authz-access-voting>> describes the relevant classes.
The following image shows the `AccessDecisionManager` interface:
Concrete implementations return an `int`, with possible values being reflected in the `AccessDecisionVoter` static fields named `ACCESS_ABSTAIN`, `ACCESS_DENIED` and `ACCESS_GRANTED`.
A voting implementation returns `ACCESS_ABSTAIN` if it has no opinion on an authorization decision.
The `AffirmativeBased` implementation grants access if one or more `ACCESS_GRANTED` votes were received (in other words, a deny vote will be ignored, provided there was at least one grant vote).
You can implement a custom `AccessDecisionManager` that tallies votes differently.
For example, votes from a particular `AccessDecisionVoter` might receive additional weighting, while a deny vote from a particular voter may have a veto effect.
The most commonly used `AccessDecisionVoter` provided with Spring Security is the `RoleVoter`, which treats configuration attributes as role names and votes to grant access if the user has been assigned that role.
It votes if any `ConfigAttribute` begins with the `ROLE_` prefix.
It votes to grant access if there is a `GrantedAuthority` that returns a `String` representation (from the `getAuthority()` method) exactly equal to one or more `ConfigAttributes` that start with the `ROLE_` prefix.
If there is no exact match of any `ConfigAttribute` starting with `ROLE_`, `RoleVoter` votes to deny access.
If no `ConfigAttribute` begins with `ROLE_`, the voter abstains.
Another voter which we have implicitly seen is the `AuthenticatedVoter`, which can be used to differentiate between anonymous, fully-authenticated, and remember-me authenticated users.
Many sites allow certain limited access under remember-me authentication but require a user to confirm their identity by logging in for full access.
When we have used the `IS_AUTHENTICATED_ANONYMOUSLY` attribute to grant anonymous access, this attribute was being processed by the `AuthenticatedVoter`.
For example, on the Spring web site, you can find a https://spring.io/blog/2009/01/03/spring-security-customization-part-2-adjusting-secured-session-in-real-time[blog article] that describes how to use a voter to deny access in real-time to users whose accounts have been suspended.
Like many other parts of Spring Security, `AfterInvocationManager` has a single concrete implementation, `AfterInvocationProviderManager`, which polls a list of ``AfterInvocationProvider``s.
Each `AfterInvocationProvider` is allowed to modify the return object or throw an `AccessDeniedException`.
Indeed multiple providers can modify the object, as the result of the previous provider is passed to the next in the list.
Please be aware that if you're using `AfterInvocationManager`, you will still need configuration attributes that allow the ``MethodSecurityInterceptor``'s `AccessDecisionManager` to allow an operation.
If you're using the typical Spring Security included `AccessDecisionManager` implementations, having no configuration attributes defined for a particular secure method invocation will cause each `AccessDecisionVoter` to abstain from voting.
In turn, if the `AccessDecisionManager` property "`allowIfAllAbstainDecisions`" is `false`, an `AccessDeniedException` will be thrown.
You may avoid this potential issue by either (i) setting "`allowIfAllAbstainDecisions`" to `true` (although this is generally not recommended) or (ii) simply ensure that there is at least one configuration attribute that an `AccessDecisionVoter` will vote to grant access for.
This latter (recommended) approach is usually achieved through a `ROLE_USER` or `ROLE_AUTHENTICATED` configuration attribute.
