added xml read/write example file: kelondroXMLTables

git-svn-id: https://svn.berlios.de/svnroot/repos/yacy/trunk@1591 6c8d7289-2bf4-0310-a012-ef5d649a1542

source/de/anomic/kelondro/kelondroXMLTables.java

@@ -0,0 +1,190 @@
+// kelondroXMLTables.java
+// -------------------------
+// part of The Kelondro Database
+// (C) by Michael Peter Christen; mc@anomic.de
+// first published on http://www.anomic.de
+// Frankfurt, Germany, 2006
+// created 09.02.2006
+//
+// $LastChangedDate: 2005-09-22 22:01:26 +0200 (Thu, 22 Sep 2005) $
+// $LastChangedRevision: 774 $
+// $LastChangedBy: orbiter $
+//
+// This program is free software; you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation; either version 2 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with this program; if not, write to the Free Software
+// Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+//
+// Using this software in any meaning (reading, learning, copying, compiling,
+// running) means that you agree that the Author(s) is (are) not responsible
+// for cost, loss of data or any harm that may be caused directly or indirectly
+// by usage of this softare or this documentation. The usage of this software
+// is on your own risk. The installation and usage (starting/running) of this
+// software may allow other people or application to access your computer and
+// any attached devices and is highly dependent on the configuration of the
+// software which must be done by the user of the software; the author(s) is
+// (are) also not responsible for proper configuration and usage of the
+// software, even if provoked by documentation provided together with
+// the software.
+//
+// Any changes to this file according to the GPL as documented in the file
+// gpl.txt aside this file in the shipment you received can be done to the
+// lines that follows this copyright notice here, but changes must not be
+// done inside the copyright notive above. A re-distribution must contain
+// the intact and unchanged copyright notice.
+// Contributions and changes to the program code must be marked as such.
+
+package de.anomic.kelondro;
+
+import java.beans.*;
+import java.io.*;
+import java.util.*;
+
+public class kelondroXMLTables {
+
+    private Hashtable tables;
+
+    // tables is a hashtable that contains hashtables as values in the table
+    private File propFile;
+    private long timestamp;
+
+    public kelondroXMLTables() {
+        this.propFile = null;
+        this.timestamp = System.currentTimeMillis();
+        this.tables = new Hashtable();
+    }
+
+    public kelondroXMLTables(File file) throws IOException {
+        this.propFile = file;
+        this.timestamp = System.currentTimeMillis();
+        if (propFile.exists()) {
+            XMLDecoder xmldec = new XMLDecoder(new FileInputStream(propFile));
+            tables = (Hashtable) xmldec.readObject();
+            xmldec.close();
+        } else {
+            tables = new Hashtable();
+        }
+    }
+
+    public void commit(File target) throws IOException {
+        // this method is used if the Mircrotable was created without assigning
+        // a file to it as an empty table the table then becomes file-based,
+        // and write operation will be committed to the file
+        this.propFile = target;
+        commit(true);
+    }
+
+    private void commit(boolean force) throws IOException {
+        // this function commits the data to a file
+        // it does not save the data until a specific waiting-time has been lasted
+        if ((force) || (System.currentTimeMillis() - timestamp > 10000)) {
+            // check error case: can only occur if logical programmic error
+            // exists
+            if (this.propFile == null)
+                throw new RuntimeException("Microtables.commit: no file specified");
+
+            // write first to a temporary file
+            File tmpFile = new File(this.propFile.toString() + ".tmp");
+
+            // write file
+            XMLEncoder xmlenc = new XMLEncoder(new FileOutputStream(tmpFile));
+            xmlenc.writeObject(tables);
+            xmlenc.close();
+
+            // delete old file and rename tmp-file to old file's name
+            this.propFile.delete();
+            tmpFile.renameTo(this.propFile);
+
+            // set the new time stamp
+            timestamp = System.currentTimeMillis();
+        }
+    }
+
+    public boolean hasTable(String table) {
+        return (tables.get(table) != null);
+    }
+
+    public int sizeTable(String table) {
+        // returns number of entries in table; if table does not exist -1
+        Hashtable l = (Hashtable) tables.get(table);
+        if (l == null)
+            return -1;
+        return l.size();
+    }
+
+    public void createTable(String table) throws IOException {
+        // creates a new table
+        Hashtable l = (Hashtable) tables.get(table);
+        if (l != null)
+            return; // we do not overwite
+        tables.put(table, new Hashtable());
+        if (this.propFile != null)
+            commit(false);
+    }
+
+    public void set(String table, String key, String value) throws IOException {
+        if (table != null) {
+            Hashtable l = (Hashtable) tables.get(table);
+            if (l == null)
+                throw new RuntimeException("Microtables.set: table does not exist");
+            if (value == null)
+                value = "";
+            l.put(key, value);
+        }
+        if (this.propFile != null)
+            commit(false);
+    }
+
+    public String get(String table, String key, String deflt) {
+        if (table != null) {
+            Hashtable l = (Hashtable) tables.get(table);
+            if (l == null)
+                throw new RuntimeException("Microtables.get: table does not exist");
+            if (l.containsKey(key))
+                return (String) l.get(key);
+            else
+                return deflt;
+        }
+        return null;
+    }
+
+    public boolean has(String table, String key) {
+        if (table != null) {
+            Hashtable l = (Hashtable) tables.get(table);
+            if (l == null)
+                throw new RuntimeException("Microtables.has: table does not exist");
+            return (l.containsKey(key));
+        }
+        return false;
+    }
+
+    public Enumeration keys(String table) {
+        if (table != null) {
+            Hashtable l = (Hashtable) tables.get(table);
+            if (l == null)
+                throw new RuntimeException("Microtables.keys: table does not exist");
+            return l.keys();
+        }
+        return null;
+    }
+
+    public void close() throws IOException {
+        finalize();
+    }
+
+    // we finalize the operation by saving everything throug the scheduler
+    // this method is called by the java GC bevore it destroys the object
+    protected void finalize() throws IOException {
+        commit(true);
+    }
+
+}