Java tutorial
/* * 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. */ import java.util.ArrayList; import java.util.Collections; import java.util.HashMap; import java.util.Iterator; /** * Simplified implementation of a Node from a Document Object Model (DOM) * parse of an XML document. This class is used to represent a DOM tree * so that the XML parser's implementation of <code>org.w3c.dom</code> need * not be visible to the remainder of Jasper. * <p> * <strong>WARNING</strong> - Construction of a new tree, or modifications * to an existing one, are not thread-safe and such accesses must be * synchronized. * * @author Craig R. McClanahan * @version $Revision: 515 $ $Date: 2008-03-17 22:02:23 +0100 (Mon, 17 Mar 2008) $ */ public class TreeNode { // ----------------------------------------------------------- Constructors /** * Construct a new node with no parent. * * @param name The name of this node */ public TreeNode(String name) { this(name, null); } /** * Construct a new node with the specified parent. * * @param name The name of this node * @param parent The node that is the parent of this node */ public TreeNode(String name, TreeNode parent) { super(); this.name = name; this.parent = parent; if (this.parent != null) this.parent.addChild(this); } // ----------------------------------------------------- Instance Variables /** * The attributes of this node, keyed by attribute name, * Instantiated only if required. */ protected HashMap attributes = null; /** * The body text associated with this node (if any). */ protected String body = null; /** * The children of this node, instantiated only if required. */ protected ArrayList children = null; /** * The name of this node. */ protected String name = null; /** * The parent node of this node. */ protected TreeNode parent = null; // --------------------------------------------------------- Public Methods /** * Add an attribute to this node, replacing any existing attribute * with the same name. * * @param name The attribute name to add * @param value The new attribute value */ public void addAttribute(String name, String value) { if (attributes == null) attributes = new HashMap(); attributes.put(name, value); } /** * Add a new child node to this node. * * @param node The new child node */ public void addChild(TreeNode node) { if (children == null) children = new ArrayList(); children.add(node); } /** * Return the value of the specified node attribute if it exists, or * <code>null</code> otherwise. * * @param name Name of the requested attribute */ public String findAttribute(String name) { if (attributes == null) return (null); else return ((String) attributes.get(name)); } /** * Return an Iterator of the attribute names of this node. If there are * no attributes, an empty Iterator is returned. */ public Iterator findAttributes() { if (attributes == null) return (Collections.EMPTY_LIST.iterator()); else return (attributes.keySet().iterator()); } /** * Return the first child node of this node with the specified name, * if there is one; otherwise, return <code>null</code>. * * @param name Name of the desired child element */ public TreeNode findChild(String name) { if (children == null) return (null); Iterator items = children.iterator(); while (items.hasNext()) { TreeNode item = (TreeNode) items.next(); if (name.equals(item.getName())) return (item); } return (null); } /** * Return an Iterator of all children of this node. If there are no * children, an empty Iterator is returned. */ public Iterator findChildren() { if (children == null) return (Collections.EMPTY_LIST.iterator()); else return (children.iterator()); } /** * Return an Iterator over all children of this node that have the * specified name. If there are no such children, an empty Iterator * is returned. * * @param name Name used to select children */ public Iterator findChildren(String name) { if (children == null) return (Collections.EMPTY_LIST.iterator()); ArrayList results = new ArrayList(); Iterator items = children.iterator(); while (items.hasNext()) { TreeNode item = (TreeNode) items.next(); if (name.equals(item.getName())) results.add(item); } return (results.iterator()); } /** * Return the body text associated with this node (if any). */ public String getBody() { return (this.body); } /** * Return the name of this node. */ public String getName() { return (this.name); } /** * Remove any existing value for the specified attribute name. * * @param name The attribute name to remove */ public void removeAttribute(String name) { if (attributes != null) attributes.remove(name); } /** * Remove a child node from this node, if it is one. * * @param node The child node to remove */ public void removeNode(TreeNode node) { if (children != null) children.remove(node); } /** * Set the body text associated with this node (if any). * * @param body The body text (if any) */ public void setBody(String body) { this.body = body; } /** * Return a String representation of this TreeNode. */ public String toString() { StringBuffer sb = new StringBuffer(); toString(sb, 0, this); return (sb.toString()); } // ------------------------------------------------------ Protected Methods /** * Append to the specified StringBuffer a character representation of * this node, with the specified amount of indentation. * * @param sb The StringBuffer to append to * @param indent Number of characters of indentation * @param node The TreeNode to be printed */ protected void toString(StringBuffer sb, int indent, TreeNode node) { int indent2 = indent + 2; // Reconstruct an opening node for (int i = 0; i < indent; i++) sb.append(' '); sb.append('<'); sb.append(node.getName()); Iterator names = node.findAttributes(); while (names.hasNext()) { sb.append(' '); String name = (String) names.next(); sb.append(name); sb.append("=\""); String value = node.findAttribute(name); sb.append(value); sb.append("\""); } sb.append(">\n"); // Reconstruct the body text of this node (if any) String body = node.getBody(); if ((body != null) && (body.length() > 0)) { for (int i = 0; i < indent2; i++) sb.append(' '); sb.append(body); sb.append("\n"); } // Reconstruct child nodes with extra indentation Iterator children = node.findChildren(); while (children.hasNext()) { TreeNode child = (TreeNode) children.next(); toString(sb, indent2, child); } // Reconstruct a closing node marker for (int i = 0; i < indent; i++) sb.append(' '); sb.append("</"); sb.append(node.getName()); sb.append(">\n"); } }