abstractpreferences.java

gcc的JAVA模块的源代码

        child = (AbstractPreferences)childCache.get(childName);
        if (child == null) {

            if (childName.length() > MAX_NAME_LENGTH)
               throw new IllegalArgumentException(childName); 

            // Not in childCache yet so create a new sub node
            child = childSpi(childName);
            // XXX - check if node is new
            childCache.put(childName, child);
        }

        // Lock the child and go down
        synchronized(child.lock) {
            return child.getNode(childPath);
        }
    }

    /**
     * Returns true if the node that the path points to exists in memory or
     * in the backing store. Otherwise it returns false or an exception is
     * thrown. When this node is removed the only valid parameter is the
     * empty string (indicating this node), the return value in that case
     * will be false.
     *
     * @exception BackingStoreException when the backing store cannot be
     *            reached
     * @exception IllegalStateException if this node has been removed
     *            and the path is not the empty string (indicating this node)
     * @exception IllegalArgumentException if the path contains two or more
     * consecutive '/' characters, ends with a '/' charactor and is not the
     * string "/" (indicating the root node) or any name on the path is more
     * then 80 characters long
     */
    public boolean nodeExists(String path) throws BackingStoreException {
        synchronized(lock) {
            if (isRemoved() && path.length() != 0)
                throw new IllegalStateException("Node removed");

            // Is it a relative path?
            if (!path.startsWith("/")) {

                // Check if it is a valid path
                if (path.indexOf("//") != -1 || path.endsWith("/"))
                    throw new IllegalArgumentException(path);

                return existsNode(path);
            }
        }

        // path started with a '/' so it is absolute
        // we drop the lock and start from the root (omitting the first '/')
        Preferences root = isUserNode() ? userRoot() : systemRoot();
        return root.nodeExists(path.substring(1));

    }

    private boolean existsNode(String path) throws BackingStoreException {

        // Empty String "" indicates this node
        if (path.length() == 0)
            return(!isRemoved());

        // Calculate child name and rest of path
        String childName;
        String childPath;
        int nextSlash = path.indexOf('/');
        if (nextSlash == -1) {
            childName = path;
            childPath = "";
        } else {
            childName = path.substring(0, nextSlash);
            childPath = path.substring(nextSlash+1);
        }

        // Get the child node
        AbstractPreferences child;
        child = (AbstractPreferences)childCache.get(childName);
        if (child == null) {

            if (childName.length() > MAX_NAME_LENGTH)
               throw new IllegalArgumentException(childName);

            // Not in childCache yet so create a new sub node
            child = getChild(childName);

            if (child == null)
                return false;

            childCache.put(childName, child);
        }

        // Lock the child and go down
        synchronized(child.lock) {
            return child.existsNode(childPath);
        }
    }

    /**
     * Returns the child sub node if it exists in the backing store or null
     * if it does not exist. Called (indirectly) by <code>nodeExists()</code>
     * when a child node name can not be found in the cache.
     * <p>
     * Gets the lock on this node, calls <code>childrenNamesSpi()</code> to
     * get an array of all (possibly uncached) children and compares the
     * given name with the names in the array. If the name is found in the
     * array <code>childSpi()</code> is called to get an instance, otherwise
     * null is returned.
     *
     * @exception BackingStoreException when the backing store cannot be
     *            reached
     */
    protected AbstractPreferences getChild(String name)
                                    throws BackingStoreException
    {
        synchronized(lock) {
            // Get all the names (not yet in the cache)
            String[] names = childrenNamesSpi();
            for (int i=0; i < names.length; i++)
                if (name.equals(names[i]))
                    return childSpi(name);
           
            // No child with that name found
            return null;
        }
    }

    /**
     * Returns true if this node has been removed with the
     * <code>removeNode()</code> method, false otherwise.
     * <p>
     * Gets the lock on this node and then returns a boolean field set by
     * <code>removeNode</code> methods.
     */
    protected boolean isRemoved() {
        synchronized(lock) {
            return removed;
        }
    }

    /**
     * Returns the parent preferences node of this node or null if this is
     * the root of the preferences tree.
     * <p>
     * Gets the lock on this node, checks that the node has not been removed
     * and returns the parent given to the constructor.
     *
     * @exception IllegalStateException if this node has been removed
     */
    public Preferences parent() {
        synchronized(lock) {
            if (isRemoved())
                throw new IllegalStateException("Node removed");

            return parent;
        }
    }

    // export methods

    /**
     * XXX
     */
    public void exportNode(OutputStream os)
                                    throws BackingStoreException,
                                           IOException
    {
        NodeWriter nodeWriter = new NodeWriter(this, os);
        nodeWriter.writePrefs();
    }

    /**
     * XXX
     */
    public void exportSubtree(OutputStream os)
                                    throws BackingStoreException,
                                           IOException
    {
        NodeWriter nodeWriter = new NodeWriter(this, os);
        nodeWriter.writePrefsTree();
    }

    // preference entry manipulation methods

    /**
     * Returns an (possibly empty) array with all the keys of the preference
     * entries of this node.
     * <p>
     * This method locks this node and checks if the node has not been
     * removed, if it has been removed it throws an exception, then it returns
     * the result of calling <code>keysSpi()</code>.
     * 
     * @exception BackingStoreException when the backing store cannot be     
     *            reached
     * @exception IllegalStateException if this node has been removed
     */
    public String[] keys() throws BackingStoreException {
        synchronized(lock) {
            if (isRemoved())
                throw new IllegalStateException("Node removed");

            return keysSpi();
        }
    }


    /**
     * Returns the value associated with the key in this preferences node. If
     * the default value of the key cannot be found in the preferences node
     * entries or something goes wrong with the backing store the supplied
     * default value is returned.
     * <p>
     * Checks that key is not null and not larger then 80 characters,
     * locks this node, and checks that the node has not been removed.
     * Then it calls <code>keySpi()</code> and returns
     * the result of that method or the given default value if it returned
     * null or throwed an exception.
     *
     * @exception IllegalArgumentException if key is larger then 80 characters
     * @exception IllegalStateException if this node has been removed
     * @exception NullPointerException if key is null
     */
    public String get(String key, String defaultVal) {
        if (key.length() > MAX_KEY_LENGTH)
            throw new IllegalArgumentException(key);

        synchronized(lock) {
            if (isRemoved())
                throw new IllegalStateException("Node removed");

            String value;
            try {
                value = getSpi(key);
            } catch (Throwable t) {
                value = null;
            }

            if (value != null) {
                return value;
            } else {
                return defaultVal;
            }
        }
    }

    /**
     * Convenience method for getting the given entry as a boolean.
     * When the string representation of the requested entry is either
     * "true" or "false" (ignoring case) then that value is returned,
     * otherwise the given default boolean value is returned.
     *
     * @exception IllegalArgumentException if key is larger then 80 characters
     * @exception IllegalStateException if this node has been removed
     * @exception NullPointerException if key is null
     */
    public boolean getBoolean(String key, boolean defaultVal) {
        String value = get(key, null);

        if ("true".equalsIgnoreCase(value))
            return true;

        if ("false".equalsIgnoreCase(value))
            return false;
        
        return defaultVal;
    }

    /**
     * Convenience method for getting the given entry as a byte array.
     * When the string representation of the requested entry is a valid
     * Base64 encoded string (without any other characters, such as newlines)
     * then the decoded Base64 string is returned as byte array,
     * otherwise the given default byte array value is returned.
     *
     * @exception IllegalArgumentException if key is larger then 80 characters
     * @exception IllegalStateException if this node has been removed
     * @exception NullPointerException if key is null
     */
    public byte[] getByteArray(String key, byte[] defaultVal) {
        String value = get(key, null);

        byte[] b = null;
        if (value != null) {
            b = decode64(value);
        }

        if (b != null)
            return b;
        else
            return defaultVal;
    }
    
    /**
     * Helper method for decoding a Base64 string as an byte array.
     * Returns null on encoding error. This method does not allow any other
     * characters present in the string then the 65 special base64 chars.
     */
    private static byte[] decode64(String s) {
        ByteArrayOutputStream bs = new ByteArrayOutputStream((s.length()/4)*3);
        char[] c = new char[s.length()];
        s.getChars(0, s.length(), c, 0);

        // Convert from base64 chars
        int endchar = -1;
        for(int j = 0; j < c.length && endchar == -1; j++) {
            if (c[j] >= 'A' && c[j] <= 'Z') {
                c[j] -= 'A';
            } else if (c[j] >= 'a' && c[j] <= 'z') {
                c[j] = (char) (c[j] + 26 - 'a');
            } else if (c[j] >= '0' && c[j] <= '9') {
                c[j] = (char) (c[j] + 52 - '0');
            } else if (c[j] == '+') {
                c[j] = 62;
            } else if (c[j] == '/') {
                c[j] = 63;
            } else if (c[j] == '=') {
                endchar = j;
            } else {