📄 securitymanager.html
字号:
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Frameset//EN""http://www.w3.org/TR/REC-html40/frameset.dtd"><!--NewPage--><HTML><HEAD><!-- Generated by javadoc on Thu Apr 27 23:35:07 PDT 2000 --><TITLE>Java 2 Platform SE v1.3: Class SecurityManager</TITLE><LINK REL ="stylesheet" TYPE="text/css" HREF="../../stylesheet.css" TITLE="Style"></HEAD><BODY BGCOLOR="white"><!-- ========== START OF NAVBAR ========== --><A NAME="navbar_top"><!-- --></A><TABLE BORDER="0" WIDTH="100%" CELLPADDING="1" CELLSPACING="0"><TR><TD COLSPAN=2 BGCOLOR="#EEEEFF" CLASS="NavBarCell1"><A NAME="navbar_top_firstrow"><!-- --></A><TABLE BORDER="0" CELLPADDING="0" CELLSPACING="3"> <TR ALIGN="center" VALIGN="top"> <TD BGCOLOR="#EEEEFF" CLASS="NavBarCell1"> <A HREF="../../overview-summary.html"><FONT CLASS="NavBarFont1"><B>Overview</B></FONT></A> </TD> <TD BGCOLOR="#EEEEFF" CLASS="NavBarCell1"> <A HREF="package-summary.html"><FONT CLASS="NavBarFont1"><B>Package</B></FONT></A> </TD> <TD BGCOLOR="#FFFFFF" CLASS="NavBarCell1Rev"> <FONT CLASS="NavBarFont1Rev"><B>Class</B></FONT> </TD> <TD BGCOLOR="#EEEEFF" CLASS="NavBarCell1"> <A HREF="class-use/SecurityManager.html"><FONT CLASS="NavBarFont1"><B>Use</B></FONT></A> </TD> <TD BGCOLOR="#EEEEFF" CLASS="NavBarCell1"> <A HREF="package-tree.html"><FONT CLASS="NavBarFont1"><B>Tree</B></FONT></A> </TD> <TD BGCOLOR="#EEEEFF" CLASS="NavBarCell1"> <A HREF="../../deprecated-list.html"><FONT CLASS="NavBarFont1"><B>Deprecated</B></FONT></A> </TD> <TD BGCOLOR="#EEEEFF" CLASS="NavBarCell1"> <A HREF="../../index-files/index-1.html"><FONT CLASS="NavBarFont1"><B>Index</B></FONT></A> </TD> <TD BGCOLOR="#EEEEFF" CLASS="NavBarCell1"> <A HREF="../../help-doc.html"><FONT CLASS="NavBarFont1"><B>Help</B></FONT></A> </TD> </TR></TABLE></TD><TD ALIGN="right" VALIGN="top" ROWSPAN=3><EM><b>Java<sup><font size=-2>TM</font></sup> 2 Platform<br>Std. Ed. v1.3</b></EM></TD></TR><TR><TD BGCOLOR="white" CLASS="NavBarCell2"><FONT SIZE="-2"> <A HREF="../../java/lang/RuntimePermission.html"><B>PREV CLASS</B></A> <A HREF="../../java/lang/Short.html"><B>NEXT CLASS</B></A></FONT></TD><TD BGCOLOR="white" CLASS="NavBarCell2"><FONT SIZE="-2"> <A HREF="../../index.html" TARGET="_top"><B>FRAMES</B></A> <A HREF="SecurityManager.html" TARGET="_top"><B>NO FRAMES</B></A></FONT></TD></TR><TR><TD VALIGN="top" CLASS="NavBarCell3"><FONT SIZE="-2"> SUMMARY: INNER | <A HREF="#field_summary">FIELD</A> | <A HREF="#constructor_summary">CONSTR</A> | <A HREF="#method_summary">METHOD</A></FONT></TD><TD VALIGN="top" CLASS="NavBarCell3"><FONT SIZE="-2">DETAIL: <A HREF="#field_detail">FIELD</A> | <A HREF="#constructor_detail">CONSTR</A> | <A HREF="#method_detail">METHOD</A></FONT></TD></TR></TABLE><!-- =========== END OF NAVBAR =========== --><HR><!-- ======== START OF CLASS DATA ======== --><H2><FONT SIZE="-1">java.lang</FONT><BR>Class SecurityManager</H2><PRE><A HREF="../../java/lang/Object.html">java.lang.Object</A> | +--<B>java.lang.SecurityManager</B></PRE><DL><DT><B>Direct Known Subclasses:</B> <DD><A HREF="../../java/rmi/RMISecurityManager.html">RMISecurityManager</A></DD></DL><HR><DL><DT>public class <B>SecurityManager</B><DT>extends <A HREF="../../java/lang/Object.html">Object</A></DL><P>The security manager is a class that allows applications to implement a security policy. It allows an application to determine, before performing a possibly unsafe or sensitive operation, what the operation is and whether it is being attempted in a security context that allows the operation to be performed. The application can allow or disallow the operation. <p> The <code>SecurityManager</code> class contains many methods with names that begin with the word <code>check</code>. These methods are called by various methods in the Java libraries before those methods perform certain potentially sensitive operations. The invocation of such a <code>check</code> method typically looks like this: <p><blockquote><pre> SecurityManager security = System.getSecurityManager(); if (security != null) { security.check<i>XXX</i>(argument, . . . ); } </pre></blockquote> <p> The security manager is thereby given an opportunity to prevent completion of the operation by throwing an exception. A security manager routine simply returns if the operation is permitted, but throws a <code>SecurityException</code> if the operation is not permitted. The only exception to this convention is <code>checkTopLevelWindow</code>, which returns a <code>boolean</code> value. <p> The current security manager is set by the <code>setSecurityManager</code> method in class <code>System</code>. The current security manager is obtained by the <code>getSecurityManager</code> method. <p> The special method <A HREF="../../java/lang/SecurityManager.html#checkPermission(java.security.Permission)"><CODE>checkPermission(java.security.Permission)</CODE></A> determines whether an access request indicated by a specified permission should be granted or denied. The default implementation calls <pre> AccessController.checkPermission(perm); </pre> <p> If a requested access is allowed, <code>checkPermission</code> returns quietly. If denied, a <code>SecurityException</code> is thrown. <p> As of Java 2 SDK v1.2, the default implementation of each of the other <code>check</code> methods in <code>SecurityManager</code> is to call the <code>SecurityManager checkPermission</code> method to determine if the calling thread has permission to perform the requested operation. <p> Note that the <code>checkPermission</code> method with just a single permission argument always performs security checks within the context of the currently executing thread. Sometimes a security check that should be made within a given context will actually need to be done from within a <i>different</i> context (for example, from within a worker thread). The <A HREF="../../java/lang/SecurityManager.html#getSecurityContext()"><CODE>getSecurityContext</CODE></A> method and the <A HREF="../../java/lang/SecurityManager.html#checkPermission(java.security.Permission, java.lang.Object)"><CODE>checkPermission</CODE></A> method that includes a context argument are provided for this situation. The <code>getSecurityContext</code> method returns a "snapshot" of the current calling context. (The default implementation returns an AccessControlContext object.) A sample call is the following: <pre> Object context = null; SecurityManager sm = System.getSecurityManager(); if (sm != null) context = sm.getSecurityContext(); </pre> <p> The <code>checkPermission</code> method that takes a context object in addition to a permission makes access decisions based on that context, rather than on that of the current execution thread. Code within a different context can thus call that method, passing the permission and the previously-saved context object. A sample call, using the SecurityManager <code>sm</code> obtained as in the previous example, is the following: <pre> if (sm != null) sm.checkPermission(permission, context); </pre> <p>Permissions fall into these categories: File, Socket, Net, Security, Runtime, Property, AWT, Reflect, and Serializable. The classes managing these various permission categories are <code>java.io.FilePermission</code>, <code>java.net.SocketPermission</code>, <code>java.net.NetPermission</code>, <code>java.security.SecurityPermission</code>, <code>java.lang.RuntimePermission</code>, <code>java.util.PropertyPermission</code>, <code>java.awt.AWTPermission</code>, <code>java.lang.reflect.ReflectPermission</code>, and <code>java.io.SerializablePermission</code>. <p>All but the first two (FilePermission and SocketPermission) are subclasses of <code>java.security.BasicPermission</code>, which itself is an abstract subclass of the top-level class for permissions, which is <code>java.security.Permission</code>. BasicPermission defines the functionality needed for all permissions that contain a name that follows the hierarchical property naming convention (for example, "exitVM", "setFactory", "queuePrintJob", etc). An asterisk may appear at the end of the name, following a ".", or by itself, to signify a wildcard match. For example: "a.*" or "*" is valid, "*a" or "a*b" is not valid. <p>FilePermission and SocketPermission are subclasses of the top-level class for permissions (<code>java.security.Permission</code>). Classes like these that have a more complicated name syntax than that used by BasicPermission subclass directly from Permission rather than from BasicPermission. For example, for a <code>java.io.FilePermission</code> object, the permission name is the pathname of a file (or directory). <p>Some of the permission classes have an "actions" list that tells the actions that are permitted for the object. For example, for a <code>java.io.FilePermission</code> object, the actions list (such as "read, write") specifies which actions are granted for the specified file (or for files in the specified directory). <p>Other permission classes are for "named" permissions - ones that contain a name but no actions list; you either have the named permission or you don't. <p>Note: There is also a <code>java.security.AllPermission</code> permission that implies all permissions. It exists to simplify the work of system administrators who might need to perform multiple tasks that require all (or numerous) permissions. <p> See <a href ="../../../guide/security/permissions.html"> Permissions in the Java 2 SDK</a> for permission-related information. This document includes, for example, a table listing the various SecurityManager <code>check</code> methods and the permission(s) the default implementation of each such method requires. It also contains a table of all the version 1.2 methods that require permissions, and for each such method tells which permission it requires. <p> For more information about <code>SecurityManager</code> changes made in the Java 2 SDK and advice regarding porting of 1.1-style security managers, see the <a href="../../../guide/security/index.html">security documentation</a>.<P><DL><DT><B>Since: </B><DD>JDK1.0</DD><DT><B>See Also: </B><DD><A HREF="../../java/lang/ClassLoader.html"><CODE>ClassLoader</CODE></A>, <A HREF="../../java/lang/SecurityException.html"><CODE>SecurityException</CODE></A>, <A HREF="../../java/lang/SecurityManager.html#checkTopLevelWindow(java.lang.Object)"><CODE>checkTopLevelWindow</CODE></A>, <A HREF="../../java/lang/System.html#getSecurityManager()"><CODE>getSecurityManager</CODE></A>, <A HREF="../../java/lang/System.html#setSecurityManager(java.lang.SecurityManager)"><CODE>setSecurityManager</CODE></A>, <A HREF="../../java/security/AccessController.html"><CODE>AccessController</CODE></A>, <A HREF="../../java/security/AccessControlContext.html"><CODE>AccessControlContext</CODE></A>, <A HREF="../../java/security/AccessControlException.html"><CODE>AccessControlException</CODE></A>, <A HREF="../../java/security/Permission.html"><CODE>Permission</CODE></A>, <A HREF="../../java/security/BasicPermission.html"><CODE>BasicPermission</CODE></A>, <A HREF="../../java/io/FilePermission.html"><CODE>FilePermission</CODE></A>, <A HREF="../../java/net/SocketPermission.html"><CODE>SocketPermission</CODE></A>, <A HREF="../../java/util/PropertyPermission.html"><CODE>PropertyPermission</CODE></A>, <A HREF="../../java/lang/RuntimePermission.html"><CODE>RuntimePermission</CODE></A>, <A HREF="../../java/awt/AWTPermission.html"><CODE>AWTPermission</CODE></A>, <A HREF="../../java/security/Policy.html"><CODE>Policy</CODE></A>, <A HREF="../../java/security/SecurityPermission.html"><CODE>SecurityPermission</CODE></A>, <A HREF="../../java/security/ProtectionDomain.html"><CODE>ProtectionDomain</CODE></A></DL><HR><P><!-- ======== INNER CLASS SUMMARY ======== --><!-- =========== FIELD SUMMARY =========== --><A NAME="field_summary"><!-- --></A><TABLE BORDER="1" CELLPADDING="3" CELLSPACING="0" WIDTH="100%"><TR BGCOLOR="#CCCCFF" CLASS="TableHeadingColor"><TD COLSPAN=2><FONT SIZE="+2"><B>Field Summary</B></FONT></TD></TR><TR BGCOLOR="white" CLASS="TableRowColor">⌨️ 快捷键说明
复制代码
Ctrl + C
搜索代码
Ctrl + F
全屏模式
F11
切换主题
Ctrl + Shift + D
显示快捷键
?
增大字号
Ctrl + =
减小字号
Ctrl + -