javax.security.auth
Class Subject

java.lang.Object
  |
  +--javax.security.auth.Subject

All Implemented Interfaces:

java.io.Serializable

public final class Subject

extends java.lang.Object

implements java.io.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.

Version:

1.105, 01/14/00

See Also:

Principal, DomainCombiner, Serialized Form

Constructor Summary

Subject()
Create an instance of a Subject with an empty Set of Principals and empty Sets of public and private credentials.

java.util.Set, java.util.Set, java.util.Set)">Subject(boolean readOnly, java.util.Set principals, java.util.Set pubCredentials, java.util.Set privCredentials)
Create an instance of a Subject with the specified Sets of Principals and credentials.

Method Summary

static java.lang.Object	doAs(Subject subject, java.security.PrivilegedAction action) Perform work as a particular Subject.
static java.lang.Object	doAs(Subject subject, java.security.PrivilegedExceptionAction action) Perform work as a particular Subject.
static java.lang.Object	doAsPrivileged(Subject subject, java.security.PrivilegedAction action, java.security.AccessControlContext acc) Perform privileged work as a particular Subject.
static java.lang.Object	doAsPrivileged(Subject subject, java.security.PrivilegedExceptionAction action, java.security.AccessControlContext acc) Perform privileged work as a particular Subject.
boolean	java.lang.Object)">equals(java.lang.Object o) Compares the specified Object with this Subject for equality.
java.util.Set	getPrincipals() Return the Set of Principals associated with this Subject.
java.util.Set	java.lang.Class)">getPrincipals(java.lang.Class c) Return a Set of Principals associated with this Subject that are instances or subclasses of the specified Class.
java.util.Set	getPrivateCredentials() Return the Set of private credentials held by this Subject.
java.util.Set	java.lang.Class)">getPrivateCredentials(java.lang.Class c) Return a Set of private credentials associated with this Subject that are instances or subclasses of the specified Class.
java.util.Set	getPublicCredentials() Return the Set of public credentials held by this Subject.
java.util.Set	java.lang.Class)">getPublicCredentials(java.lang.Class c) Return a Set of public credentials associated with this Subject that are instances or subclasses of the specified Class.
static Subject	getSubject(java.security.AccessControlContext acc) Get the Subject associated with the provided AccessControlContext.
int	hashCode() Returns a hashcode for this Subject.
boolean	isReadOnly() Query whether this Subject is read-only.
void	setReadOnly() Set this Subject to be read-only.
java.lang.String	toString() Return the String representation of this Subject.

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait

Constructor Detail

Subject

public 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"), for example).

java.util.Set, java.util.Set, java.util.Set)">

Subject

public Subject(boolean readOnly,
               java.util.Set principals,
               java.util.Set pubCredentials,
               java.util.Set privCredentials)

Create an instance of a Subject with the specified Sets of Principals and credentials.

The specified Sets must check whether this Subject has been set read-only before permitting subsequent modifications. The specified Sets must also prevent illegal modifications by ensuring that callers have sufficient permissions.

Parameters:

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.

Throws:

NullPointerException - if the specified principals, pubCredentials, or privCredentials are null.

Method Detail

setReadOnly

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.

Throws:

java.lang.SecurityException - if the caller does not have permission to set this Subject to be read-only.

isReadOnly

public boolean isReadOnly()

Query whether this Subject is read-only.

Returns:

true if this Subject is read-only, false otherwise.

getSubject

public static Subject getSubject(java.security.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.

Parameters:

acc - the AccessControlContext from which to retrieve the Subject.

Returns:

the Subject associated with the provided AccessControlContext, or null if no Subject is associated with the provided AccessControlContext.

Throws:

java.lang.SecurityException - if the caller does not have permission to get the Subject.

NullPointerException - if the provided AccessControlContext is null.

doAs

public static java.lang.Object doAs(Subject subject,
                                    java.security.PrivilegedAction 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.

Parameters:

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.

Returns:

the Object returned by the PrivilegedAction's run method.

Throws:

NullPointerException - if the PrivilegedAction is null.

java.lang.SecurityException - if the caller does not have permission to invoke this method.

doAs

public static java.lang.Object doAs(Subject subject,
                                    java.security.PrivilegedExceptionAction action)
                             throws java.security.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.

Parameters:

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.

Returns:

the Object returned by the PrivilegedExceptionAction's run method.

Throws:

java.security.PrivilegedActionException - if the PrivilegedExceptionAction.run method throws a checked exception.

NullPointerException - if the specified PrivilegedExceptionAction is null.

java.lang.SecurityException - if the caller does not have permission to invoke this method.

doAsPrivileged

public static java.lang.Object doAsPrivileged(Subject subject,
                                              java.security.PrivilegedAction action,
                                              java.security.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.

Parameters:

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.

Returns:

the Object returned by the PrivilegedAction's run method.

Throws:

NullPointerException - if the PrivilegedAction is null.

java.lang.SecurityException - if the caller does not have permission to invoke this method.

doAsPrivileged

public static java.lang.Object doAsPrivileged(Subject subject,
                                              java.security.PrivilegedExceptionAction action,
                                              java.security.AccessControlContext acc)
                                       throws java.security.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.

Parameters:

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.

Returns:

the Object returned by the PrivilegedExceptionAction's run method.

Throws:

java.security.PrivilegedActionException - if the PrivilegedExceptionAction.run method throws a checked exception.

NullPointerException - if the specified PrivilegedExceptionAction is null.

java.lang.SecurityException - if the caller does not have permission to invoke this method.

getPrincipals

public java.util.Set 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.

Returns:

The Set of Principals associated with this Subject.

java.lang.Class)">

getPrincipals

public java.util.Set getPrincipals(java.lang.Class 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.

Parameters:

c - the returned Set of Principals will all be instances of this class.

Returns:

a Set of Principals that are instances of the specified Class.

Throws:

NullPointerException - if the specified Class is null.

getPublicCredentials

public java.util.Set 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.

Returns:

A Set of public credentials held by this Subject.

getPrivateCredentials

public java.util.Set 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.

Returns:

A Set of private credentials held by this Subject.

java.lang.Class)">

getPublicCredentials

public java.util.Set getPublicCredentials(java.lang.Class 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.

Parameters:

c - the returned Set of public credentials will all be instances of this class.

Returns:

a Set of public credentials that are instances of the specified Class.

Throws:

NullPointerException - if the specified Class is null.

java.lang.Class)">

getPrivateCredentials

public java.util.Set getPrivateCredentials(java.lang.Class c)

Return a Set of private 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 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.

Parameters:

c - the returned Set of private credentials will all be instances of this class.

Returns:

a Set of private credentials that are instances of the specified Class.

Throws:

NullPointerException - if the specified Class is null.

java.lang.Object)">

equals

public boolean equals(java.lang.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.

Overrides:

equals in class java.lang.Object

Parameters:

o - Object to be compared for equality with this Subject.

Returns:

true if the specified Object is equal to this Subject.

Throws:

java.lang.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.

toString

public java.lang.String toString()

Return the String representation of this Subject.

Overrides:

toString in class java.lang.Object

Returns:

the String representation of this Subject.

hashCode

public int hashCode()

Returns a hashcode for this Subject.

The hashcode is derived exclusive or-ing the hashcodes of this Subject's Principals and credentials.

If a particular credential was destroyed (credential.hashCode() throws an IllegalStateException), the hashcode for that credential is derived via: credential.getClass().toString().hashCode().

Overrides:

hashCode in class java.lang.Object

Returns:

a hashcode for this Subject.

Throws:

java.lang.SecurityException - if the caller does not have permission to access this Subject's private credentials.