Java(TM) 2 Platform, Standard Edition, v1.2.2 API Specification: Class SocketPermission - JDK 5 Documentation v1.2.2, Java 2 SDK 英文文档

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java.net
Class SocketPermission

java.lang.Object
  |
  +--java.security.Permission
        |
        +--java.net.SocketPermission

public final class SocketPermission
extends Permission
implements Serializable

This class represents access to a network via sockets. A SocketPermission consists of a host specification and a set of "actions" specifying ways to connect to that host. The host is specified as

    host = (hostname | IPaddress)[:portrange]
    portrange = portnumber | -portnumber | portnumber-[portnumber]

The host is expressed as a DNS name, as a numerical IP address, or as "localhost" (for the local machine). The wildcard "*" may be included once in a DNS name host specification. If it is included, it must be in the leftmost position, as in "*.sun.com".

The port or portrange is optional. A port specification of the form "N-", where N is a port number, signifies all ports numbered N and above, while a specification of the form "-N" indicates all ports numbered N and below.

The possible ways to connect to the host are

 accept
 connect
 listen
 resolve

The "listen" action is only meaningful when used with "localhost". The "resolve" (resolve host/ip name service lookups) action is implied when any of the other actions are present.

As an example of the creation and meaning of SocketPermissions, note that if the following permission:

   p1 = new SocketPermission("puffin.eng.sun.com:7777", "connect,accept");

is granted to some code, it allows that code to connect to port 7777 on puffin.eng.sun.com, and to accept connections on that port.

Similarly, if the following permission:

   p1 = new SocketPermission("puffin.eng.sun.com:7777", "connect,accept");
   p2 = new SocketPermission("localhost:1024-", "accept,connect,listen");

is granted to some code, it allows that code to accept connections on, connect to, or listen on any port between 1024 and 65535 on the local host.

Note: Granting code permission to accept or make connections to remote hosts may be dangerous because malevolent code can then more easily transfer and share confidential data among parties who may not otherwise have access to the data.

See Also:: Permissions, SocketPermissions, Serialized Form

Constructor Summary

SocketPermission(String host, String action)
          Creates a new SocketPermission object with the specified actions.

Method Summary

boolean equals(Object obj)
          Checks two SocketPermission objects for equality.

String getActions()
          Returns the canonical string representation of the actions.

int hashCode()
          Returns the hash code value for this object.

boolean implies(Permission p)
          Checks if this socket permission object "implies" the specified permission.

PermissionCollection newPermissionCollection()
          Returns a new PermissionCollection object for storing SocketPermission objects.

Methods inherited from class java.security.Permission

checkGuard, getName, toString

Methods inherited from class java.lang.Object

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

Constructor Detail

SocketPermission

public SocketPermission(String host,
                        String action)

Creates a new SocketPermission object with the specified actions. The host is expressed as a DNS name, or as a numerical IP address. Optionally, a port or a portrange may be supplied (separated from the DNS name or IP address by a colon).

To specify the local machine, use "localhost" as the host. Also note: An empty host String ("") is equivalent to "localhost".

The actions parameter contains a comma-separated list of the actions granted for the specified host (and port(s)). Possible actions are "connect", "listen", "accept", "resolve", or any combination of those. "resolve" is automatically added when any of the other three are specified.

Examples of SocketPermission instantiation are the following:

    nr = new SocketPermission("www.catalog.com", "connect");
    nr = new SocketPermission("www.sun.com:80", "connect");
    nr = new SocketPermission("*.sun.com", "connect");
    nr = new SocketPermission("*.edu", "resolve");
    nr = new SocketPermission("204.160.241.0", "connect");
    nr = new SocketPermission("localhost:1024-65535", "listen");
    nr = new SocketPermission("204.160.241.0:1024-65535", "connect");

Parameters:: host - the hostname or IPaddress of the computer, optionally including a colon followed by a port or port range.; action - the action string.

Method Detail

implies

public boolean implies(Permission p)

Checks if this socket permission object "implies" the specified permission.

More specifically, this method first ensures that all of the following are true (and returns false if any of them are not):

p is an instanceof SocketPermission,
p's actions are a proper subset of this object's actions, and
p's port range is included in this port range.

Then implies checks each of the following, in order, and for each returns true if the stated condition is true:

If this object was initialized with a single IP address and one of p's IP addresses is equal to this object's IP address.
If this object is a wildcard domain (such as *.sun.com), and p's canonical name (the name without any preceding *) ends with this object's canonical host name. For example, *.sun.com implies *.eng.sun.com..
If this object was not initialized with a single IP address, and one of this object's IP addresses equals one of p's IP addresses.
If this canonical name equals p's canonical name.

If none of the above are true, implies returns false.

Overrides:: implies in class Permission

Parameters:: p - the permission to check against.
Returns:: true if the specified permission is implied by this object, false if not.

equals

public boolean equals(Object obj)

Checks two SocketPermission objects for equality.

Overrides:: equals in class Permission

Parameters:: obj - the object to test for equality with this object.
Returns:: true if obj is a SocketPermission, and has the same hostname, port range, and actions as this SocketPermission object.

hashCode

public int hashCode()

Returns the hash code value for this object.

Overrides:: hashCode in class Permission

Returns:: a hash code value for this object.

getActions

public String getActions()

Returns the canonical string representation of the actions. Always returns present actions in the following order: connect, listen, accept, resolve.

Overrides:: getActions in class Permission

Returns:: the canonical string representation of the actions.

newPermissionCollection

public PermissionCollection newPermissionCollection()

Returns a new PermissionCollection object for storing SocketPermission objects.

SocketPermission objects must be stored in a manner that allows them to be inserted into the collection in any order, but that also enables the PermissionCollection implies method to be implemented in an efficient (and consistent) manner.

Overrides:: newPermissionCollection in class Permission

Returns:: a new PermissionCollection object suitable for storing SocketPermissions.