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<TITLE>Creating a Custom Permission (Java Developers Almanac Example)
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    <A HREF="../java.security/pkg.html">java.security</A><font color="#666666" class="xsmall-font">
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        <B><A HREF="../java.security/pkg.html#Permissions">Permissions</A></B><font color="#666666" class="xsmall-font">
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  <h3>e215. Creating a Custom Permission</h3>

This example creates a permission that controls access to pages of a
book.  The permission name consists of a book id, a colon, and a set
of allowable pages. The set of allowable pages is specified as a
comma-separated list of page ranges. For example, <code>88:1,3-4</code> specifies
that pages 1, 3, and 4 are accessible in the book whose id is 88.


<pre>    import java.io.*;
    import java.security.*;
    import java.util.*;
    
    public class <font color="#0066ff"><i>Book</i></font>Permission extends BasicPermission implements Serializable {
        String bookid = null;
        BitSet pages = new BitSet();
    
        public <font color="#0066ff"><i>Book</i></font>Permission(String perm) {
            super(perm);
            String[] fields = perm.split(":");
    
            // Get book id
            bookid = fields[0];
    
            // Get page ranges and set pages
            String[] ranges = fields[1].split(",");
            for (int i=0; i&lt;ranges.length; i++) {
                // Get the start and end of the range
                String[] range = ranges[i].split("-");
                int start = Integer.parseInt(range[0]);
                int end = start;
                if (range.length &gt; 1) {
                    end = Integer.parseInt(range[1]);
                }
    
                // Set the pages in the bitset
                pages.set(start, end+1);
            }
        }
    
        public boolean implies(Permission permission) {
            <font color="#0066ff"><i>Book</i></font>Permission bp = (<font color="#0066ff"><i>Book</i></font>Permission)permission;
    
            // Check book id
            if (!bookid.equals(bp.bookid)) {
                return false;
            }
    
            // Clone other pages bitset
            BitSet pgs = (BitSet)bp.pages.clone();
    
            // OR both bitsets
            pgs.or(pages);
    
            // Return true if this bitset contains all the bits in the other bitset
            return pages.equals(pgs);
        }
    
        public String getActions() {
            return "";
        }
    
        public int hashCode() {
            return bookid.hashCode() ^ pages.hashCode();
        }
    
        public boolean equals(Object obj) {
            if (!(obj instanceof <font color="#0066ff"><i>Book</i></font>Permission)) {
                return false;
            }
            BookPermission bp = (BookPermission)obj;
            return pages.equals(bp.pages) &amp;&amp; bookid.equals(bp.bookid);
        }
    }
</pre>
Here's some examples that use <code>BookPermission</code>:

<pre>    Permission p1 = new <font color="#0066ff"><i>Book</i></font>Permission(<font color="#0066ff"><i>"123:1-3,5,7-10"</i></font>);
    
    Permission p2 = new <font color="#0066ff"><i>Book</i></font>Permission(<font color="#0066ff"><i>"123:2"</i></font>);
    boolean b = p1.implies(p2);      // false
    
    p2 = new <font color="#0066ff"><i>Book</i></font>Permission(<font color="#0066ff"><i>"123:3"</i></font>);
    b = p1.implies(p2);              // true
    
    p2 = new <font color="#0066ff"><i>Book</i></font>Permission(<font color="#0066ff"><i>"1234:3"</i></font>);
    b = p1.implies(p2);              // false
    
    p2 = new <font color="#0066ff"><i>Book</i></font>Permission(<font color="#0066ff"><i>"123:3,8-9"</i></font>);
    b = p1.implies(p2);              // true
    
    p2 = new <font color="#0066ff"><i>Book</i></font>Permission(<font color="#0066ff"><i>"123:3-5"</i></font>);
    b = p1.implies(p2);              // false
</pre>
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            &nbsp;<b>Related Examples</b></font></td>
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e212. <a class="eglink" href="CustSecurityMgr.html?l=rel">
    Enabling the Security Manager
</a>
<br>

e213. <a class="eglink" href="CheckPermission.html?l=rel">
    Checking Read/Write Permission for a Directory
</a>
<br>

e214. <a class="eglink" href="CheckImplies.html?l=rel">
    Determining If One Permission Implies Another
</a>
<br>

e216. <a class="eglink" href="GuardObj.html?l=rel">
    Controlling Access to an Object
</a>
<br>

e217. <a class="eglink" href="ListClassPerm.html?l=rel">
    Listing All Permissions Granted to a Loaded Class
</a>
<br>

e218. <a class="eglink" href="ListUrlPerm.html?l=rel">
    Listing All Permissions Granted to Classes Loaded from a URL or Directory
</a>
<br>


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<br>
        See also: 
<a class="eglink" href="/egs/java.security/pkg.html?l=rel#Key%20Store">
    Key Store
</a>&nbsp;&nbsp;

<a class="eglink" href="/egs/java.security/pkg.html?l=rel#Message%20Digests">
    Message Digests
</a>&nbsp;&nbsp;

<a class="eglink" href="/egs/java.security/pkg.html?l=rel#Policy%20Files">
    Policy Files
</a>&nbsp;&nbsp;

<a class="eglink" href="/egs/java.security/pkg.html?l=rel#Public%20and%20Private%20Keys">
    Public and Private Keys
</a>&nbsp;&nbsp;

<a class="eglink" href="/egs/java.security/pkg.html?l=rel#Signatures">
    Signatures
</a>&nbsp;&nbsp;

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