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1: /* Root.java -- The root of an object tree. 2: Copyright (C) 2005 Free Software Foundation, Inc. 3: 4: This file is part of GNU Classpath. 5: 6: GNU Classpath is free software; you can redistribute it and/or modify 7: it under the terms of the GNU General Public License as published by 8: the Free Software Foundation; either version 2, or (at your option) 9: any later version. 10: 11: GNU Classpath is distributed in the hope that it will be useful, but 12: WITHOUT ANY WARRANTY; without even the implied warranty of 13: MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 14: General Public License for more details. 15: 16: You should have received a copy of the GNU General Public License 17: along with GNU Classpath; see the file COPYING. If not, write to the 18: Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 19: 02110-1301 USA. 20: 21: Linking this library statically or dynamically with other modules is 22: making a combined work based on this library. Thus, the terms and 23: conditions of the GNU General Public License cover the whole 24: combination. 25: 26: As a special exception, the copyright holders of this library give you 27: permission to link this library with independent modules to produce an 28: executable, regardless of the license terms of these independent 29: modules, and to copy and distribute the resulting executable under 30: terms of your choice, provided that you also meet, for each linked 31: independent module, the terms and conditions of the license of that 32: module. An independent module is a module which is not derived from 33: or based on this library. If you modify this library, you may extend 34: this exception to your version of the library, but you are not 35: obligated to do so. If you do not wish to do so, delete this 36: exception statement from your version. */ 37: 38: 39: package gnu.java.beans.encoder; 40: 41: import java.beans.XMLEncoder; 42: import java.util.Iterator; 43: import java.util.Stack; 44: 45: import gnu.java.beans.encoder.elements.Element; 46: 47: /** <p><code>Root</code> provides a simple interface to a tree of 48: * objects.</p> 49: * 50: * <p>Using an instance of this class a logical representation of 51: * the real object tree that is serialized can be built. When the 52: * actual data should be written as XML <code>Root</code> and 53: * {@link gnu.java.beans.encoder.elements.Element} class can provide 54: * context information which is used to write the best fitting 55: * XML representation.</p> 56: * 57: * @author Robert Schuster (robertschuster@fsfe.org) 58: */ 59: public class Root 60: { 61: private Stack parents = new Stack(); 62: 63: private Element rootElement, current; 64: 65: private boolean started; 66: 67: public Root() 68: { 69: rootElement = current = new RootElement(); 70: } 71: 72: /** <p>Adds another child element to the tree.</p> 73: * 74: * <p>The new element automatically becomes the current 75: * element.</p> 76: * 77: * @param elem The new child element. 78: */ 79: public void addChild(Element elem) 80: { 81: current.addChild(elem); 82: 83: parents.push(current); 84: current = elem; 85: } 86: 87: /** 88: * <p>Marks that the end of the current element 89: * is reached and that no more childs are added to 90: * it.</p> 91: * 92: * <p>The behavior is to return to the nearest parent 93: * element.</p> 94: */ 95: public void end() 96: { 97: current = (Element) parents.pop(); 98: } 99: 100: /** 101: * <p>Goes back to the nearest parent element but 102: * deletes the just created child.</p> 103: * 104: * <p>This is used if something went wrong while 105: * processing the child element's {@link java.beans.Expression} 106: * or {@link java.beans.Statement}.</p> 107: * 108: */ 109: public void deleteLast() 110: { 111: current = (Element) parents.pop(); 112: 113: current.removeLast(); 114: } 115: 116: /** 117: * <p>Traverses the elements in the object tree 118: * and creates their XML representation in the output 119: * stream of the given {@link Writer}.</p> 120: * 121: * <p>Finally the <code>Writer</code> is flushed.</p> 122: * 123: * @param writer The Writer instance that generates the XML representation. 124: */ 125: public void traverse(Writer writer) 126: { 127: if (!started) 128: { 129: writer.writePreamble(); 130: rootElement.writeStart(writer); 131: } 132: started = true; 133: 134: traverse(writer, rootElement.iterator()); 135: 136: rootElement.clear(); 137: 138: writer.flush(); 139: } 140: 141: /** Writes the closing element and closes the {@link Writer} 142: * 143: * @param writer The Writer instance that generates the XML representation. 144: */ 145: public void close(Writer writer) 146: { 147: rootElement.writeEnd(writer); 148: writer.close(); 149: } 150: 151: /** Recursively traverses the object tree. 152: * 153: * @param writer The Writer instance that generates the XML representation. 154: * @param ite An Iterator returning Element instances. 155: */ 156: private void traverse(Writer writer, Iterator ite) 157: { 158: while (ite.hasNext()) 159: { 160: Element e = (Element) ite.next(); 161: e.writeStart(writer); 162: 163: traverse(writer, e.iterator()); 164: 165: e.writeEnd(writer); 166: 167: e.clear(); 168: } 169: } 170: 171: /** <p>A special Element implementation that represents the 172: * encoder's context.</p> 173: * 174: * <p>This element is written only once per Writer.</p> 175: * 176: * <p>It is assumed that this element is never empty to simplify 177: * the implementation.</p> 178: * 179: * @author Robert Schuster (robertschuster@fsfe.org); 180: * 181: */ 182: static class RootElement extends Element 183: { 184: public void writeStart(Writer writer) 185: { 186: writer.write("java", new String[] { "version", "class" }, 187: new String[] { System.getProperty("java.version"), 188: XMLEncoder.class.getName() }, false); 189: } 190: 191: public void writeEnd(Writer writer) 192: { 193: writer.writeEnd(false); 194: } 195: 196: } 197: 198: }