Source Code Cross Referenced for DbTreeWalker.java in  » Forum » yazd » com » Yasna » forum » database » Java Source Code / Java DocumentationJava Source Code and Java Documentation

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Java Source Code / Java Documentation » Forum » yazd » com.Yasna.forum.database 
Source Cross Referenced  Class Diagram Java Document (Java Doc) 


001:        /**
002:         * Copyright (C) 2001 Yasna.com. All rights reserved.
003:         *
004:         * ===================================================================
005:         * The Apache Software License, Version 1.1
006:         *
007:         * Redistribution and use in source and binary forms, with or without
008:         * modification, are permitted provided that the following conditions
009:         * are met:
010:         *
011:         * 1. Redistributions of source code must retain the above copyright
012:         *    notice, this list of conditions and the following disclaimer.
013:         *
014:         * 2. Redistributions in binary form must reproduce the above copyright
015:         *    notice, this list of conditions and the following disclaimer in
016:         *    the documentation and/or other materials provided with the
017:         *    distribution.
018:         *
019:         * 3. The end-user documentation included with the redistribution,
020:         *    if any, must include the following acknowledgment:
021:         *       "This product includes software developed by
022:         *        Yasna.com (http://www.yasna.com)."
023:         *    Alternately, this acknowledgment may appear in the software itself,
024:         *    if and wherever such third-party acknowledgments normally appear.
025:         *
026:         * 4. The names "Yazd" and "Yasna.com" must not be used to
027:         *    endorse or promote products derived from this software without
028:         *    prior written permission. For written permission, please
029:         *    contact yazd@yasna.com.
030:         *
031:         * 5. Products derived from this software may not be called "Yazd",
032:         *    nor may "Yazd" appear in their name, without prior written
033:         *    permission of Yasna.com.
034:         *
035:         * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
036:         * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
037:         * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
038:         * DISCLAIMED.  IN NO EVENT SHALL YASNA.COM OR
039:         * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
040:         * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
041:         * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
042:         * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
043:         * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
044:         * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
045:         * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
046:         * SUCH DAMAGE.
047:         * ====================================================================
048:         *
049:         * This software consists of voluntary contributions made by many
050:         * individuals on behalf of Yasna.com. For more information
051:         * on Yasna.com, please see <http://www.yasna.com>.
052:         */
053:
054:        /**
055:         * Copyright (C) 2000 CoolServlets.com. All rights reserved.
056:         *
057:         * ===================================================================
058:         * The Apache Software License, Version 1.1
059:         *
060:         * Redistribution and use in source and binary forms, with or without
061:         * modification, are permitted provided that the following conditions
062:         * are met:
063:         *
064:         * 1. Redistributions of source code must retain the above copyright
065:         *    notice, this list of conditions and the following disclaimer.
066:         *
067:         * 2. Redistributions in binary form must reproduce the above copyright
068:         *    notice, this list of conditions and the following disclaimer in
069:         *    the documentation and/or other materials provided with the
070:         *    distribution.
071:         *
072:         * 3. The end-user documentation included with the redistribution,
073:         *    if any, must include the following acknowledgment:
074:         *       "This product includes software developed by
075:         *        CoolServlets.com (http://www.coolservlets.com)."
076:         *    Alternately, this acknowledgment may appear in the software itself,
077:         *    if and wherever such third-party acknowledgments normally appear.
078:         *
079:         * 4. The names "Jive" and "CoolServlets.com" must not be used to
080:         *    endorse or promote products derived from this software without
081:         *    prior written permission. For written permission, please
082:         *    contact webmaster@coolservlets.com.
083:         *
084:         * 5. Products derived from this software may not be called "Jive",
085:         *    nor may "Jive" appear in their name, without prior written
086:         *    permission of CoolServlets.com.
087:         *
088:         * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
089:         * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
090:         * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
091:         * DISCLAIMED.  IN NO EVENT SHALL COOLSERVLETS.COM OR
092:         * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
093:         * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
094:         * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
095:         * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
096:         * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
097:         * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
098:         * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
099:         * SUCH DAMAGE.
100:         * ====================================================================
101:         *
102:         * This software consists of voluntary contributions made by many
103:         * individuals on behalf of CoolServlets.com. For more information
104:         * on CoolServlets.com, please see <http://www.coolservlets.com>.
105:         */package com.Yasna.forum.database;
106:
107:        import java.sql.*;
108:
109:        import com.Yasna.forum.*;
110:        import com.Yasna.util.*;
111:
112:        /**
113:         * Database implementation of the TreeWalker interface. This class is relatively
114:         * inefficient compared to how it will eventually be implemented. However,
115:         * a schema change is needed before that optimization is needed (represent
116:         * tree structure directly in schema).
117:         */
118:        public class DbTreeWalker implements  TreeWalker {
119:
120:            /** DATABASE QUERIES **/
121:            private static final String GET_CHILD = "SELECT yazdMessageTree.childID, yazdMessage.creationDate FROM "
122:                    + "yazdMessageTree, yazdMessage WHERE "
123:                    + "yazdMessageTree.childID=yazdMessage.messageID AND "
124:                    + "yazdMessageTree.parentID=? ORDER BY yazdMessage.creationDate";
125:            private static final String CHILD_COUNT = "SELECT count(*) FROM yazdMessageTree WHERE parentID=?";
126:            private static final String INDEX_OF_CHILD = "SELECT yazdMessageTree.childID, yazdMessage.creationDate "
127:                    + "FROM yazdMessageTree, yazdMessage WHERE yazdMessageTree.childID=yazdMessage.messageID "
128:                    + "AND yazdMessageTree.parentID=? ORDER BY yazdMessage.creationDate";
129:
130:            private DbForumThread thread;
131:            private DbForumFactory factory;
132:
133:            public DbTreeWalker(DbForumThread thread, DbForumFactory factory) {
134:                this .thread = thread;
135:                this .factory = factory;
136:            }
137:
138:            /**
139:             * Returns the root of the tree. Returns null only if the tree has no nodes.
140:             *
141:             * @returns the root of the tree
142:             */
143:            public ForumMessage getRoot() {
144:                return thread.getRootMessage();
145:            }
146:
147:            /**
148:             * Returns the child of parent at index index in the parent's child array.
149:             * This should not return null if index is a valid index for parent (that
150:             * is index >= 0 && index < getChildCount(parent)).
151:             *
152:             * @param parent the parent message.
153:             * @param index the index of the child.
154:             * @returns the child of parent at index.
155:             */
156:            public ForumMessage getChild(ForumMessage parent, int index) {
157:                ForumMessage message = null;
158:                Connection con = null;
159:                PreparedStatement pstmt = null;
160:                try {
161:                    con = DbConnectionManager.getConnection();
162:                    pstmt = con.prepareStatement(GET_CHILD);
163:                    pstmt.setInt(1, parent.getID());
164:                    ResultSet rs = pstmt.executeQuery();
165:                    while (rs.next() && index > 0) {
166:                        index--;
167:                    }
168:                    if (index == 0) {
169:                        int messageID = rs.getInt(1);
170:                        message = thread.getMessage(messageID);
171:                    }
172:                } catch (Exception e) {
173:                    System.err.println("Error in DbMessageTreeWalker:getChild("
174:                            + index + ")-" + e);
175:                    e.printStackTrace();
176:                } finally {
177:                    try {
178:                        pstmt.close();
179:                    } catch (Exception e) {
180:                        e.printStackTrace();
181:                    }
182:                    try {
183:                        con.close();
184:                    } catch (Exception e) {
185:                        e.printStackTrace();
186:                    }
187:                }
188:                return message;
189:            }
190:
191:            /**
192:             * Returns the number of children of parent. Returns 0 if the node is a
193:             * leaf or if it has no children.
194:             *
195:             * @param parent a node in the tree, obtained from this data source.
196:             * @returns the number of children of the node parent.
197:             */
198:            public int getChildCount(ForumMessage parent) {
199:                int childCount = 0;
200:                Connection con = null;
201:                PreparedStatement pstmt = null;
202:                try {
203:                    con = DbConnectionManager.getConnection();
204:                    pstmt = con.prepareStatement(CHILD_COUNT);
205:                    pstmt.setInt(1, parent.getID());
206:                    ResultSet rs = pstmt.executeQuery();
207:                    rs.next();
208:                    childCount = rs.getInt(1);
209:                } catch (Exception e) {
210:                    System.err.println("Error in DbTreeWalker:getChildCount()-"
211:                            + e);
212:                    e.printStackTrace();
213:                } finally {
214:                    try {
215:                        pstmt.close();
216:                    } catch (Exception e) {
217:                        e.printStackTrace();
218:                    }
219:                    try {
220:                        con.close();
221:                    } catch (Exception e) {
222:                        e.printStackTrace();
223:                    }
224:                }
225:                return childCount;
226:            }
227:
228:            /**
229:             * Returns the total number of recursive children of a parent. Returns 0
230:             * if there are no children. This method is not intended to aid in
231:             * navigation of a Thread but is included as an added utility.
232:             */
233:            public int getRecursiveChildCount(ForumMessage parent) {
234:                int numChildren = 0;
235:                int num = getChildCount(parent);
236:                numChildren += num;
237:                for (int i = 0; i < num; i++) {
238:                    ForumMessage child = getChild(parent, i);
239:                    if (child != null) {
240:                        numChildren += getRecursiveChildCount(child);
241:                    }
242:                }
243:                return numChildren;
244:            }
245:
246:            /**
247:             * Returns the index of child in parent.
248:             */
249:            public int getIndexOfChild(ForumMessage parent, ForumMessage child) {
250:                int index = 0;
251:                Connection con = null;
252:                PreparedStatement pstmt = null;
253:                ResultSet rs = null;
254:                try {
255:                    con = DbConnectionManager.getConnection();
256:                    pstmt = con.prepareStatement(INDEX_OF_CHILD);
257:                    pstmt.setInt(1, parent.getID());
258:                    rs = pstmt.executeQuery();
259:                    while (rs.next()) {
260:                        if (rs.getInt(1) == child.getID()) {
261:                            break;
262:                        }
263:                        index++;
264:                    }
265:                } catch (Exception e) {
266:                    System.err
267:                            .println("Error in DbTreeWalker:getIndexOfChild()-"
268:                                    + e);
269:                } finally {
270:                    try {
271:                        pstmt.close();
272:                    } catch (Exception e) {
273:                        e.printStackTrace();
274:                    }
275:                    try {
276:                        con.close();
277:                    } catch (Exception e) {
278:                        e.printStackTrace();
279:                    }
280:                }
281:                return index;
282:            }
283:
284:            /**
285:             * Returns true if node is a leaf. A node is a leaf when it has no children
286:             * messages.
287:             *
288:             * @param node a node in the tree, obtained from this data source
289:             * @returns true if node is a leaf
290:             */
291:            public boolean isLeaf(ForumMessage node) {
292:                return (getChildCount(node) == 0);
293:            }
294:        }
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