Permission

java.lang.Object
- java.security.Permission

所有已实现的接口:

Serializable, Guard

直接已知子类:

AllPermission, BasicPermission, FilePermission, PrivateCredentialPermission, SocketPermission, UnresolvedPermission
```
public abstract class Permission
extends Object
implements Guard, Serializable
```
Abstract class for representing access to a system resource. All permissions have a name (whose interpretation depends on the subclass), as well as abstract functions for defining the semantics of the particular Permission subclass.
Most Permission objects also include an "actions" list that tells the actions that are permitted for the object. For example, for a java.io.FilePermission object, the permission name is the pathname of a file (or directory), and the actions list (such as "read, write") specifies which actions are granted for the specified file (or for files in the specified directory). The actions list is optional for Permission objects, such as java.lang.RuntimePermission, that don't need such a list; you either have the named permission (such as "system.exit") or you don't.
An important method that must be implemented by each subclass is the implies method to compare Permissions. Basically, "permission p1 implies permission p2" means that if one is granted permission p1, one is naturally granted permission p2. Thus, this is not an equality test, but rather more of a subset test.
Permission objects are similar to String objects in that they are immutable once they have been created. Subclasses should not provide methods that can change the state of a permission once it has been created.

另请参阅:

Permissions, PermissionCollection, 序列化表格

构造器概要

构造器
构造器说明

Permission(String name)
Constructs a permission with the specified name.

构造器
构造器	说明
`Permission(String name)`	Constructs a permission with the specified name.

方法概要

所有方法实例方法抽象方法具体方法
限定符和类型	方法	说明
`void`	`checkGuard(Object object)`	Implements the guard interface for a permission.
`abstract String`	`getActions()`	Returns the actions as a String.
`String`	`getName()`	Returns the name of this Permission.
`abstract boolean`	`implies(Permission permission)`	Checks if the specified permission's actions are "implied by" this object's actions.
`PermissionCollection`	`newPermissionCollection()`	Returns an empty PermissionCollection for a given Permission object, or null if one is not defined.

从类继承的方法 java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

- 构造器详细资料
  - Permission
```
public Permission(String name)
```
    Constructs a permission with the specified name.
    
    参数:
    
    name - name of the Permission object being created.
- 方法详细资料
  - checkGuard
```
public void checkGuard(Object object)
                throws SecurityException
```
    Implements the guard interface for a permission. The SecurityManager.checkPermission method is called, passing this permission object as the permission to check. Returns silently if access is granted. Otherwise, throws a SecurityException.
    
    指定者:
    
    checkGuard 在接口中 Guard
    
    参数:
    
    object - the object being guarded (currently ignored).
    
    抛出:
    
    SecurityException - if a security manager exists and its checkPermission method doesn't allow access.
    
    另请参阅:
    
    Guard, GuardedObject, SecurityManager.checkPermission(java.security.Permission)
  - implies
```
public abstract boolean implies(Permission permission)
```
    Checks if the specified permission's actions are "implied by" this object's actions.
    This must be implemented by subclasses of Permission, as they are the only ones that can impose semantics on a Permission object.
    The implies method is used by the AccessController to determine whether or not a requested permission is implied by another permission that is known to be valid in the current execution context.
    
    参数:
    
    permission - the permission to check against.
    
    返回:
    
    true if the specified permission is implied by this object, false if not.
  - getName
```
public final String getName()
```
    Returns the name of this Permission. For example, in the case of a java.io.FilePermission, the name will be a pathname.
    
    返回:
    
    the name of this Permission.
  - getActions
```
public abstract String getActions()
```
    Returns the actions as a String. This is abstract so subclasses can defer creating a String representation until one is needed. Subclasses should always return actions in what they consider to be their canonical form. For example, two FilePermission objects created via the following:
```
   perm1 = new FilePermission(p1,"read,write");
   perm2 = new FilePermission(p2,"write,read");
 
```
    both return "read,write" when the getActions method is invoked.
    返回:
    
    the actions of this Permission.
  - newPermissionCollection
```
public PermissionCollection newPermissionCollection()
```
    Returns an empty PermissionCollection for a given Permission object, or null if one is not defined. Subclasses of class Permission should override this if they need to store their permissions in a particular PermissionCollection object in order to provide the correct semantics when the PermissionCollection.implies method is called. If null is returned, then the caller of this method is free to store permissions of this type in any PermissionCollection they choose (one that uses a Hashtable, one that uses a Vector, etc).
    
    返回:
    
    a new PermissionCollection object for this type of Permission, or null if one is not defined.

类 Permission

构造器概要

方法概要

从类继承的方法 java.lang.Object

构造器详细资料

Permission

方法详细资料

checkGuard

implies

getName

getActions

newPermissionCollection