e215. creating a custom permission.txt

这里面包含了一百多个JAVA源文件

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, 88:1,3-4 specifies that pages 1, 3, and 4 are accessible in the book whose id is 88. 
    import java.io.*;
    import java.security.*;
    import java.util.*;
    
    public class BookPermission extends BasicPermission implements Serializable {
        String bookid = null;
        BitSet pages = new BitSet();
    
        public BookPermission(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<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 > 1) {
                    end = Integer.parseInt(range[1]);
                }
    
                // Set the pages in the bitset
                pages.set(start, end+1);
            }
        }
    
        public boolean implies(Permission permission) {
            BookPermission bp = (BookPermission)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 BookPermission)) {
                return false;
            }
            BookPermission bp = (BookPermission)obj;
            return pages.equals(bp.pages) && bookid.equals(bp.bookid);
        }
    }

Here's some examples that use BookPermission: 
    Permission p1 = new BookPermission("123:1-3,5,7-10");
    
    Permission p2 = new BookPermission("123:2");
    boolean b = p1.implies(p2);      // false
    
    p2 = new BookPermission("123:3");
    b = p1.implies(p2);              // true
    
    p2 = new BookPermission("1234:3");
    b = p1.implies(p2);              // false
    
    p2 = new BookPermission("123:3,8-9");
    b = p1.implies(p2);              // true
    
    p2 = new BookPermission("123:3-5");
    b = p1.implies(p2);              // false

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