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Subject: svn commit: r645121 -
 /commons/proper/configuration/branches/configuration2_experimental/src/main/java/org/apache/commons/configuration2/flat/FlatNodeHandler.java
Date: Sat, 05 Apr 2008 15:27:43 -0000
To: commits@commons.apache.org
From: oheger@apache.org
Message-Id: <20080405152743.5EC731A9832@eris.apache.org>

Author: oheger
Date: Sat Apr  5 08:27:42 2008
New Revision: 645121

URL: http://svn.apache.org/viewvc?rev=645121&view=rev
Log:
New node handler implementation for flat nodes

Added:
    commons/proper/configuration/branches/configuration2_experimental/src/main/java/org/apache/commons/configuration2/flat/FlatNodeHandler.java   (with props)

Added: commons/proper/configuration/branches/configuration2_experimental/src/main/java/org/apache/commons/configuration2/flat/FlatNodeHandler.java
URL: http://svn.apache.org/viewvc/commons/proper/configuration/branches/configuration2_experimental/src/main/java/org/apache/commons/configuration2/flat/FlatNodeHandler.java?rev=645121&view=auto
==============================================================================
--- commons/proper/configuration/branches/configuration2_experimental/src/main/java/org/apache/commons/configuration2/flat/FlatNodeHandler.java (added)
+++ commons/proper/configuration/branches/configuration2_experimental/src/main/java/org/apache/commons/configuration2/flat/FlatNodeHandler.java Sat Apr  5 08:27:42 2008
@@ -0,0 +1,309 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.commons.configuration2.flat;
+
+import java.util.Collections;
+import java.util.List;
+
+import org.apache.commons.configuration2.ConfigurationRuntimeException;
+import org.apache.commons.configuration2.expr.AbstractNodeHandler;
+import org.apache.commons.configuration2.expr.NodeHandler;
+
+/**
+ * <p>
+ * A <code>NodeHandler</code> implementation for dealing with the nodes of a
+ * <code>{@link AbstractFlatConfiguration}</code>.
+ * </p>
+ * <p>
+ * This class is used internally by a <code>AbstractFlatConfiguration</code>
+ * to deal with its nodes. Note that a node structure is only constructed if the
+ * configuration is treated as a hierarchical configuration, for instance if it
+ * is added to a <code>CombinedConfiguration</code>.
+ * </p>
+ * <p>
+ * The implementation of the methods required by the
+ * <code>{@link NodeHandler}</code> interface is straight forward. In most
+ * cases, it is possible to simply delegate to the corresponding
+ * <code>FlatNode</code> method. Attributes are not supported by flat nodes,
+ * so in this area there are only dummy implementations.
+ * </p>
+ * <p>
+ * Actions caused by this node handler may modify the associated configuration
+ * and thus trigger change events. Per default the configuration will invalidate
+ * its node structure if a change event is received. Because of that the node
+ * handler has to keep track of the updated caused by itself to avoid
+ * unnecessary invalidation of nodes. (The configuration asks the node handler
+ * for each change event whether the node structure should be invalidated.) Note
+ * that modifications of a configuration are not thread-safe. So no additional
+ * synchronization is done in this class.
+ * </p>
+ *
+ * @author <a href="http://commons.apache.org/configuration/team-list.html">Commons
+ *         Configuration team</a>
+ * @version $Id$
+ * @since 2.0
+ * @see FlatNode
+ */
+class FlatNodeHandler extends AbstractNodeHandler<FlatNode>
+{
+    /** Stores the associated flat configuration. */
+    private AbstractFlatConfiguration configuration;
+
+    /**
+     * A flag whether an update of the configuration was caused by an operation
+     * on its node structure.
+     */
+    private boolean internalUpdate;
+
+    /**
+     * Creates a new instance of <code>FlatNodeHandler</code> and initializes
+     * it with the associated configuration.
+     *
+     * @param config the configuration
+     */
+    public FlatNodeHandler(AbstractFlatConfiguration config)
+    {
+        configuration = config;
+    }
+
+    /**
+     * Returns the configuration associated with this node handler.
+     *
+     * @return the associated configuration
+     */
+    public AbstractFlatConfiguration getConfiguration()
+    {
+        return configuration;
+    }
+
+    /**
+     * Returns a flag whether an update of the associated configuration was
+     * caused by this node handler. Whenever the configuration receives a change
+     * event, it asks the node hander whether it is responsible for this event.
+     * The result of this method determines whether the configuration's node
+     * structure has to be invalidated: if the event was caused by the node
+     * handler, the structure has already been updated and there is no need to
+     * invalidate it. Otherwise the configuration was directly manipulated, and
+     * the node structure is now out of sync.
+     *
+     * @return a flag whether an internal update was caused by this node handler
+     */
+    public boolean isInternalUpdate()
+    {
+        return internalUpdate;
+    }
+
+    /**
+     * Adds an attribute to the specified node. Flat nodes do not support
+     * attributes, so this implementation just throws an exception.
+     *
+     * @param node the node
+     * @param name the name of the attribute
+     * @param value the new value
+     * @throws ConfigurationRuntimeException if the attribute value cannot be
+     *         added
+     */
+    public void addAttributeValue(FlatNode node, String name, Object value)
+    {
+        throw new ConfigurationRuntimeException(
+                "Cannot add an attribute to a flat node!");
+    }
+
+    /**
+     * Adds a new child to the given node.
+     *
+     * @param node the node
+     * @param name the name of the new child
+     * @return the newly created child node
+     */
+    public FlatNode addChild(FlatNode node, String name)
+    {
+        return node.addChild(name);
+    }
+
+    /**
+     * Returns the value of an attribute of the specified node. Flat nodes do
+     * not support attributes, so this implementation always returns <b>null</b>.
+     *
+     * @param node the node
+     * @param name the name of the attribute
+     * @return the value of this attribute
+     */
+    public Object getAttributeValue(FlatNode node, String name)
+    {
+        return null;
+    }
+
+    /**
+     * Returns a list with the names of the attributes of the specified node.
+     * Flat nodes do not support attributes, so this implementation always
+     * returns an empty list.
+     *
+     * @param node the node
+     * @return a list with the names of the existing attributes
+     */
+    public List<String> getAttributes(FlatNode node)
+    {
+        return Collections.emptyList();
+    }
+
+    /**
+     * Returns the child of the specified node with the given index.
+     *
+     * @param node the node
+     * @param index the index
+     * @return the child node with this index
+     */
+    public FlatNode getChild(FlatNode node, int index)
+    {
+        return node.getChild(index);
+    }
+
+    /**
+     * Returns a list with all children of the specified node.
+     *
+     * @param node the node
+     * @return a list with all child nodes of this node
+     */
+    public List<FlatNode> getChildren(FlatNode node)
+    {
+        return node.getChildren();
+    }
+
+    /**
+     * Returns a list with all children of the specified node with the given
+     * name.
+     *
+     * @param node the node
+     * @param name the desired name
+     * @return a list with the child nodes with this name
+     */
+    public List<FlatNode> getChildren(FlatNode node, String name)
+    {
+        return node.getChildren(name);
+    }
+
+    /**
+     * Returns the number of children with the given name of the specified node.
+     *
+     * @param node the node
+     * @param name the name of the desired child nodes
+     * @return the number of the child nodes with this name
+     */
+    public int getChildrenCount(FlatNode node, String name)
+    {
+        return node.getChildrenCount(name);
+    }
+
+    /**
+     * Returns the parent of the specified node.
+     *
+     * @param node the node
+     * @return the parent node
+     */
+    public FlatNode getParent(FlatNode node)
+    {
+        return node.getParent();
+    }
+
+    /**
+     * Returns the value of the specified node.
+     *
+     * @param node the node
+     * @return the value of this node
+     */
+    public Object getValue(FlatNode node)
+    {
+        return node.getValue(getConfiguration());
+    }
+
+    /**
+     * Returns the name of the specified node.
+     *
+     * @param node the node
+     * @return the name of this node
+     */
+    public String nodeName(FlatNode node)
+    {
+        return node.getName();
+    }
+
+    /**
+     * Removes an attribute of the specified node. Flat nodes do not have
+     * attributes, so this implementation is just an empty dummy.
+     *
+     * @param node the node
+     * @param name the name of the attribute
+     */
+    public void removeAttribute(FlatNode node, String name)
+    {
+    }
+
+    /**
+     * Removes a child of the given parent node.
+     *
+     * @param node the parent node
+     * @param child the child node to be removed
+     */
+    public void removeChild(FlatNode node, FlatNode child)
+    {
+        internalUpdate = true;
+        try
+        {
+            node.removeChild(getConfiguration(), child);
+        }
+        finally
+        {
+            internalUpdate = false;
+        }
+    }
+
+    /**
+     * Sets an attribute of the specified node. Flat nodes do not support
+     * attributes, so this implementation just throws an exception.
+     *
+     * @param node the node
+     * @param name the name of the attribute
+     * @param value the new value
+     * @throws ConfigurationRuntimeException if the attribute value cannot be
+     *         set
+     */
+    public void setAttributeValue(FlatNode node, String name, Object value)
+    {
+        throw new ConfigurationRuntimeException(
+                "Cannot set an attribute of a flat node!");
+    }
+
+    /**
+     * Sets the value of the specified node.
+     *
+     * @param node the node
+     * @param value the new value
+     */
+    public void setValue(FlatNode node, Object value)
+    {
+        internalUpdate = true;
+        try
+        {
+            node.setValue(getConfiguration(), value);
+        }
+        finally
+        {
+            internalUpdate = false;
+        }
+    }
+}

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