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<!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 23:36:02 PDT 2000 --><TITLE>Java 2 Platform SE v1.3: Class Policy</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/Policy.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/security/Permissions.html"><B>PREV CLASS</B></A> <A HREF="../../java/security/ProtectionDomain.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="Policy.html" TARGET="_top"><B>NO FRAMES</B></A></FONT></TD></TR><TR><TD VALIGN="top" CLASS="NavBarCell3"><FONT SIZE="-2"> SUMMARY: INNER | FIELD | <A HREF="#constructor_summary">CONSTR</A> | <A HREF="#method_summary">METHOD</A></FONT></TD><TD VALIGN="top" CLASS="NavBarCell3"><FONT SIZE="-2">DETAIL: FIELD | <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.security</FONT><BR>Class Policy</H2><PRE><A HREF="../../java/lang/Object.html">java.lang.Object</A> | +--<B>java.security.Policy</B></PRE><HR><DL><DT>public abstract class <B>Policy</B><DT>extends <A HREF="../../java/lang/Object.html">Object</A></DL><P>This is an abstract class for representing the system security policy for a Java application environment (specifying which permissions are available for code from various sources). That is, the security policy is represented by a Policy subclass providing an implementation of the abstract methods in this Policy class. <p>There is only one Policy object in effect at any given time. <p>The Policy object is typically consulted by objects such as the <A HREF="../../java/security/SecureClassLoader.html#defineClass(java.lang.String, byte[], int, int, java.security.CodeSource)"><CODE>SecureClassLoader</CODE></A> when a loader needs to determine the permissions to assign to a particular protection domain. The SecureClassLoader executes code such as the following to ask the currently installed Policy object to populate a PermissionCollection object: <pre> policy = Policy.getPolicy(); PermissionCollection perms = policy.getPermissions(MyCodeSource) </pre> <p>The SecureClassLoader object passes in a CodeSource object, which encapsulates the codebase (URL) and public key certificates of the classes being loaded. The Policy object consults its policy specification and returns an appropriate Permissions object enumerating the permissions allowed for code from the specified code source. <p>The source location for the policy information utilized by the Policy object is up to the Policy implementation. The policy configuration may be stored, for example, as a flat ASCII file, as a serialized binary file of the Policy class, or as a database. <p>The currently-installed Policy object can be obtained by calling the <code>getPolicy</code> method, and it can be changed by a call to the <code>setPolicy</code> method (by code with permission to reset the Policy). <p>The <code>refresh</code> method causes the policy object to refresh/reload its current configuration. This is implementation-dependent. For example, if the policy object stores its policy in configuration files, calling <code>refresh</code> will cause it to re-read the configuration policy files. The refreshed policy may not have an effect on classes loaded from a given CodeSource. This is dependent on the ProtectionDomain caching strategy of the ClassLoader. For example, the <A HREF="../../java/security/SecureClassLoader.html#getPermissions(java.security.CodeSource)"><CODE>SecureClassLoader</CODE></A> caches protection domains. <p>The default Policy implementation can be changed by setting the value of the "policy.provider" security property (in the Java security properties file) to the fully qualified name of the desired Policy implementation class. The Java security properties file is located in the file named <JAVA_HOME>/lib/security/java.security, where <JAVA_HOME> refers to the directory where the SDK was installed.<P><DL><DT><B>See Also: </B><DD><A HREF="../../java/security/CodeSource.html"><CODE>CodeSource</CODE></A>, <A HREF="../../java/security/PermissionCollection.html"><CODE>PermissionCollection</CODE></A>, <A HREF="../../java/security/SecureClassLoader.html"><CODE>SecureClassLoader</CODE></A></DL><HR><P><!-- ======== INNER CLASS SUMMARY ======== --><!-- =========== FIELD SUMMARY =========== --><!-- ======== CONSTRUCTOR SUMMARY ======== --><A NAME="constructor_summary"><!-- --></A><TABLE BORDER="1" CELLPADDING="3" CELLSPACING="0" WIDTH="100%"><TR BGCOLOR="#CCCCFF" CLASS="TableHeadingColor"><TD COLSPAN=2><FONT SIZE="+2"><B>Constructor Summary</B></FONT></TD></TR><TR BGCOLOR="white" CLASS="TableRowColor"><TD><CODE><B><A HREF="../../java/security/Policy.html#Policy()">Policy</A></B>()</CODE><BR> </TD></TR></TABLE> <!-- ========== METHOD SUMMARY =========== --><A NAME="method_summary"><!-- --></A><TABLE BORDER="1" CELLPADDING="3" CELLSPACING="0" WIDTH="100%"><TR BGCOLOR="#CCCCFF" CLASS="TableHeadingColor"><TD COLSPAN=2><FONT SIZE="+2"><B>Method Summary</B></FONT></TD></TR><TR BGCOLOR="white" CLASS="TableRowColor"><TD ALIGN="right" VALIGN="top" WIDTH="1%"><FONT SIZE="-1"><CODE>abstract <A HREF="../../java/security/PermissionCollection.html">PermissionCollection</A></CODE></FONT></TD><TD><CODE><B><A HREF="../../java/security/Policy.html#getPermissions(java.security.CodeSource)">getPermissions</A></B>(<A HREF="../../java/security/CodeSource.html">CodeSource</A> codesource)</CODE><BR> Evaluates the global policy and returns a PermissionCollection object specifying the set of permissions allowed for code from the specified code source.</TD></TR><TR BGCOLOR="white" CLASS="TableRowColor"><TD ALIGN="right" VALIGN="top" WIDTH="1%"><FONT SIZE="-1"><CODE>static <A HREF="../../java/security/Policy.html">Policy</A></CODE></FONT></TD><TD><CODE><B><A HREF="../../java/security/Policy.html#getPolicy()">getPolicy</A></B>()</CODE>⌨️ 快捷键说明
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