Java Path Create Canonical canonicalPath(String orig)

Description

Canonicalize a request path, making sure it starts with a slash, and getting rid of double slashes and components with the values "." or "..".

License

Open Source License

Parameter

Parameter	Description
orig	non-null; the original path

Return

null-ok; the canonicalized form, or null if the original is bogus in some way

Declaration

static public String canonicalPath(String orig)

Method Source Code

//package com.java2s;
// the rights to use, copy, modify, merge, publish, distribute, sublicense,

public class Main {
    /**//from   w  w w.  j a v  a  2s .c o  m
     * Canonicalize a request path, making sure it starts with a slash, and
     * getting rid of double slashes and components with the values
     * <code>"."</code> or <code>".."</code>. This will return
     * <code>null</code> if the given path is somehow perniciously
     * erroneous (such as referring to <code>".."</code> at the beginning
     * of the path).
     *
     * @param orig non-null; the original path
     * @return null-ok; the canonicalized form, or <code>null</code> if
     * the original is bogus in some way 
     */
    static public String canonicalPath(String orig) {
        if (orig.length() == 0) {
            return "/";
        }

        if (orig.charAt(0) != '/') {
            orig = '/' + orig;
        }

        for (;;) {
            int foundAt = orig.indexOf("//");
            if (foundAt == -1) {
                break;
            }
            orig = orig.substring(0, foundAt) + orig.substring(foundAt + 1);
        }

        for (;;) {
            int foundAt = orig.indexOf("/./");
            if (foundAt == -1) {
                break;
            }
            orig = orig.substring(0, foundAt) + orig.substring(foundAt + 2);
        }

        while (orig.endsWith("/.")) {
            orig = orig.substring(0, orig.length() - 2);
        }

        for (;;) {
            int foundAt = orig.indexOf("/../");
            if (foundAt == -1) {
                break;
            }

            int prevSlash = orig.lastIndexOf('/', foundAt - 1);
            if (prevSlash == -1) {
                // can't take .. at the beginning of the document
                return null;
            }

            orig = orig.substring(0, prevSlash) + orig.substring(foundAt + 3);
        }

        while (orig.endsWith("/..")) {
            int prevSlash = orig.lastIndexOf('/', orig.length() - 3);
            if (prevSlash <= 0) {
                // can't take .. at the beginning of the document
                return null;
            }

            orig = orig.substring(0, prevSlash);
        }

        return orig;
    }
}