public final class Subject extends Object implements Serializable
A Subject
represents a grouping of related information for a single entity, such as a person. Such information includes the Subject's identities as well as its security-related attributes (passwords and cryptographic keys, for example).
Subjects may potentially have multiple identities. Each identity is represented as a Principal
within the Subject
. Principals simply bind names to a Subject
. For example, a Subject
that happens to be a person, Alice, might have two Principals: one which binds "Alice Bar", the name on her driver license, to the Subject
, and another which binds, "999-99-9999", the number on her student identification card, to the Subject
. Both Principals refer to the same Subject
even though each has a different name.
A Subject
may also own security-related attributes, which are referred to as credentials. Sensitive credentials that require special protection, such as private cryptographic keys, are stored within a private credential Set
. Credentials intended to be shared, such as public key certificates or Kerberos server tickets are stored within a public credential Set
. Different permissions are required to access and modify the different credential Sets.
To retrieve all the Principals associated with a Subject
, invoke the getPrincipals
method. To retrieve all the public or private credentials belonging to a Subject
, invoke the getPublicCredentials
method or getPrivateCredentials
method, respectively. To modify the returned Set
of Principals and credentials, use the methods defined in the Set
class. For example:
Subject subject; Principal principal; Object credential; // add a Principal and credential to the Subject subject.getPrincipals().add(principal); subject.getPublicCredentials().add(credential);
This Subject
class implements Serializable
. While the Principals associated with the Subject
are serialized, the credentials associated with the Subject
are not. Note that the java.security.Principal
class does not implement Serializable
. Therefore all concrete Principal
implementations associated with Subjects must implement Serializable
.
Principal
, DomainCombiner
, Serialized Formpublic Subject()
Create an instance of a Subject
with an empty Set
of Principals and empty Sets of public and private credentials.
The newly constructed Sets check whether this Subject
has been set read-only before permitting subsequent modifications. The newly created Sets also prevent illegal modifications by ensuring that callers have sufficient permissions.
To modify the Principals Set, the caller must have AuthPermission("modifyPrincipals")
. To modify the public credential Set, the caller must have AuthPermission("modifyPublicCredentials")
. To modify the private credential Set, the caller must have AuthPermission("modifyPrivateCredentials")
.
public Subject(boolean readOnly, Set<? extends Principal> principals, Set<?> pubCredentials, Set<?> privCredentials)
Create an instance of a Subject
with Principals and credentials.
The Principals and credentials from the specified Sets are copied into newly constructed Sets. These newly created Sets check whether this Subject
has been set read-only before permitting subsequent modifications. The newly created Sets also prevent illegal modifications by ensuring that callers have sufficient permissions.
To modify the Principals Set, the caller must have AuthPermission("modifyPrincipals")
. To modify the public credential Set, the caller must have AuthPermission("modifyPublicCredentials")
. To modify the private credential Set, the caller must have AuthPermission("modifyPrivateCredentials")
.
readOnly
- true if the Subject
is to be read-only, and false otherwise.
principals
- the Set
of Principals to be associated with this Subject
.
pubCredentials
- the Set
of public credentials to be associated with this Subject
.
privCredentials
- the Set
of private credentials to be associated with this Subject
.NullPointerException
- if the specified principals
, pubCredentials
, or privCredentials
are null
.public void setReadOnly()
Set this Subject
to be read-only.
Modifications (additions and removals) to this Subject's Principal
Set
and credential Sets will be disallowed. The destroy
operation on this Subject's credentials will still be permitted.
Subsequent attempts to modify the Subject's Principal
and credential Sets will result in an IllegalStateException
being thrown. Also, once a Subject
is read-only, it can not be reset to being writable again.
SecurityException
- if the caller does not have permission to set this Subject
to be read-only.public boolean isReadOnly()
Query whether this Subject
is read-only.
Subject
is read-only, false otherwise.public static Subject getSubject(AccessControlContext acc)
Get the Subject
associated with the provided AccessControlContext
.
The AccessControlContext
may contain many Subjects (from nested doAs
calls). In this situation, the most recent Subject
associated with the AccessControlContext
is returned.
acc
- the AccessControlContext
from which to retrieve the Subject
.Subject
associated with the provided AccessControlContext
, or null
if no Subject
is associated with the provided AccessControlContext
.SecurityException
- if the caller does not have permission to get the Subject
.
NullPointerException
- if the provided AccessControlContext
is null
.public static <T> T doAs(Subject subject, PrivilegedAction<T> action)
Perform work as a particular Subject
.
This method first retrieves the current Thread's AccessControlContext
via AccessController.getContext
, and then instantiates a new AccessControlContext
using the retrieved context along with a new SubjectDomainCombiner
(constructed using the provided Subject
). Finally, this method invokes AccessController.doPrivileged
, passing it the provided PrivilegedAction
, as well as the newly constructed AccessControlContext
.
T
- the type of the value returned by the PrivilegedAction's run
method.subject
- the Subject
that the specified action
will run as. This parameter may be null
.
action
- the code to be run as the specified Subject
.
run
method.NullPointerException
- if the PrivilegedAction
is null
.
SecurityException
- if the caller does not have permission to invoke this method.public static <T> T doAs(Subject subject, PrivilegedExceptionAction<T> action) throws PrivilegedActionException
Perform work as a particular Subject
.
This method first retrieves the current Thread's AccessControlContext
via AccessController.getContext
, and then instantiates a new AccessControlContext
using the retrieved context along with a new SubjectDomainCombiner
(constructed using the provided Subject
). Finally, this method invokes AccessController.doPrivileged
, passing it the provided PrivilegedExceptionAction
, as well as the newly constructed AccessControlContext
.
T
- the type of the value returned by the PrivilegedExceptionAction's run
method.subject
- the Subject
that the specified action
will run as. This parameter may be null
.
action
- the code to be run as the specified Subject
.
run
method.PrivilegedActionException
- if the PrivilegedExceptionAction.run
method throws a checked exception.
NullPointerException
- if the specified PrivilegedExceptionAction
is null
.
SecurityException
- if the caller does not have permission to invoke this method.public static <T> T doAsPrivileged(Subject subject, PrivilegedAction<T> action, AccessControlContext acc)
Perform privileged work as a particular Subject
.
This method behaves exactly as Subject.doAs
, except that instead of retrieving the current Thread's AccessControlContext
, it uses the provided AccessControlContext
. If the provided AccessControlContext
is null
, this method instantiates a new AccessControlContext
with an empty collection of ProtectionDomains.
T
- the type of the value returned by the PrivilegedAction's run
method.subject
- the Subject
that the specified action
will run as. This parameter may be null
.
action
- the code to be run as the specified Subject
.
acc
- the AccessControlContext
to be tied to the specified subject and action.
run
method.NullPointerException
- if the PrivilegedAction
is null
.
SecurityException
- if the caller does not have permission to invoke this method.public static <T> T doAsPrivileged(Subject subject, PrivilegedExceptionAction<T> action, AccessControlContext acc) throws PrivilegedActionException
Perform privileged work as a particular Subject
.
This method behaves exactly as Subject.doAs
, except that instead of retrieving the current Thread's AccessControlContext
, it uses the provided AccessControlContext
. If the provided AccessControlContext
is null
, this method instantiates a new AccessControlContext
with an empty collection of ProtectionDomains.
T
- the type of the value returned by the PrivilegedExceptionAction's run
method.subject
- the Subject
that the specified action
will run as. This parameter may be null
.
action
- the code to be run as the specified Subject
.
acc
- the AccessControlContext
to be tied to the specified subject and action.
run
method.PrivilegedActionException
- if the PrivilegedExceptionAction.run
method throws a checked exception.
NullPointerException
- if the specified PrivilegedExceptionAction
is null
.
SecurityException
- if the caller does not have permission to invoke this method.public Set<Principal> getPrincipals()
Return the Set
of Principals associated with this Subject
. Each Principal
represents an identity for this Subject
.
The returned Set
is backed by this Subject's internal Principal
Set
. Any modification to the returned Set
affects the internal Principal
Set
as well.
Set
of Principals associated with this Subject
.public <T extends Principal> Set<T> getPrincipals(Class<T> c)
Return a Set
of Principals associated with this Subject
that are instances or subclasses of the specified Class
.
The returned Set
is not backed by this Subject's internal Principal
Set
. A new Set
is created and returned for each method invocation. Modifications to the returned Set
will not affect the internal Principal
Set
.
T
- the type of the class modeled by c
c
- the returned Set
of Principals will all be instances of this class.Set
of Principals that are instances of the specified Class
.NullPointerException
- if the specified Class
is null
.public Set<Object> getPublicCredentials()
Return the Set
of public credentials held by this Subject
.
The returned Set
is backed by this Subject's internal public Credential Set
. Any modification to the returned Set
affects the internal public Credential Set
as well.
Set
of public credentials held by this Subject
.public Set<Object> getPrivateCredentials()
Return the Set
of private credentials held by this Subject
.
The returned Set
is backed by this Subject's internal private Credential Set
. Any modification to the returned Set
affects the internal private Credential Set
as well.
A caller requires permissions to access the Credentials in the returned Set
, or to modify the Set
itself. A SecurityException
is thrown if the caller does not have the proper permissions.
While iterating through the Set
, a SecurityException
is thrown if the caller does not have permission to access a particular Credential. The Iterator
is nevertheless advanced to next element in the Set
.
Set
of private credentials held by this Subject
.public <T> Set<T> getPublicCredentials(Class<T> c)
Return a Set
of public credentials associated with this Subject
that are instances or subclasses of the specified Class
.
The returned Set
is not backed by this Subject's internal public Credential Set
. A new Set
is created and returned for each method invocation. Modifications to the returned Set
will not affect the internal public Credential Set
.
T
- the type of the class modeled by c
c
- the returned Set
of public credentials will all be instances of this class.Set
of public credentials that are instances of the specified Class
.NullPointerException
- if the specified Class
is null
.public <T> Set<T> getPrivateCredentials(Class<T> c)
Return a Set
of private credentials associated with this Subject
that are instances or subclasses of the specified Class
.
The caller must have permission to access all of the requested Credentials, or a SecurityException
will be thrown.
The returned Set
is not backed by this Subject's internal private Credential Set
. A new Set
is created and returned for each method invocation. Modifications to the returned Set
will not affect the internal private Credential Set
.
T
- the type of the class modeled by c
c
- the returned Set
of private credentials will all be instances of this class.Set
of private credentials that are instances of the specified Class
.NullPointerException
- if the specified Class
is null
.public boolean equals(Object o)
Compares the specified Object with this Subject
for equality. Returns true if the given object is also a Subject and the two Subject
instances are equivalent. More formally, two Subject
instances are equal if their Principal
and Credential
Sets are equal.
equals
in class Object
o
- Object to be compared for equality with this Subject
.Subject
.SecurityException
- if the caller does not have permission to access the private credentials for this Subject
, or if the caller does not have permission to access the private credentials for the provided Subject
.Object.hashCode()
, HashMap
public String toString()
Return the String representation of this Subject
.
public int hashCode()
Returns a hashcode for this Subject
.
hashCode
in class Object
Subject
.SecurityException
- if the caller does not have permission to access this Subject's private credentials.Object.equals(java.lang.Object)
, System.identityHashCode(java.lang.Object)
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