001: package org.tigris.scarab.da;
002:
003: /* ================================================================
004: * Copyright (c) 2000 CollabNet. All rights reserved.
005: *
006: * Redistribution and use in source and binary forms, with or without
007: * modification, are permitted provided that the following conditions are
008: * met:
009: *
010: * 1. Redistributions of source code must retain the above copyright
011: * notice, this list of conditions and the following disclaimer.
012: *
013: * 2. Redistributions in binary form must reproduce the above copyright
014: * notice, this list of conditions and the following disclaimer in the
015: * documentation and/or other materials provided with the distribution.
016: *
017: * 3. The end-user documentation included with the redistribution, if
018: * any, must include the following acknowlegement: "This product includes
019: * software developed by CollabNet (http://www.collab.net/)."
020: * Alternately, this acknowlegement may appear in the software itself, if
021: * and wherever such third-party acknowlegements normally appear.
022: *
023: * 4. The hosted project names must not be used to endorse or promote
024: * products derived from this software without prior written
025: * permission. For written permission, please contact info@collab.net.
026: *
027: * 5. Products derived from this software may not use the "Tigris" name
028: * nor may "Tigris" appear in their names without prior written
029: * permission of CollabNet.
030: *
031: * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
032: * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
033: * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
034: * IN NO EVENT SHALL COLLAB.NET OR ITS CONTRIBUTORS BE LIABLE FOR ANY
035: * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
036: * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE
037: * GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
038: * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER
039: * IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
040: * OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
041: * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
042: *
043: * ====================================================================
044: *
045: * This software consists of voluntary contributions made by many
046: * individuals on behalf of CollabNet.
047: */
048:
049: import java.util.HashMap;
050: import java.util.Map;
051:
052: import org.apache.commons.lang.exception.NestableError;
053:
054: import org.apache.turbine.Turbine;
055:
056: /**
057: * A lookup interface for the data access layer classes. Use instead
058: * of Fulcrum for simplicity. Migration to an Avalon-based or other
059: * "standard" API is a longer term possibility.
060: */
061: public class DAFactory {
062: private static Map instances = new HashMap();
063:
064: public static AttributeAccess getAttributeAccess() {
065: return (AttributeAccess) lookup("AttributeAccess");
066: }
067:
068: /**
069: * Gets a handle to one of our data access classes, in our
070: * configuration prefixed with <code>dataaccess</code> and
071: * sufffixed with <code>classname</code>
072: * (e.g. dataaccess.AttributeAccess.classname =
073: * org.tigris.scarab.da.ScarabAttributeAccess).
074: *
075: * @param identifier Which data access API to get a handle for.
076: * @throws LookupError If a ClassNotFoundException would normally
077: * be thrown.
078: * @throws LinkageError
079: */
080: private static Object lookup(String identifier) {
081: Object da = instances.get(identifier);
082: if (da == null) {
083: // There is an implicit race condition here. Worst case
084: // we create extra instances of our DA impl, and/or more
085: // than one HashMap. In either case, the cost of the
086: // waste is minimal.
087: Map map = new HashMap(instances);
088: String className = Turbine.getConfiguration().getString(
089: "dataaccess." + identifier + ".classname");
090: try {
091: da = Class.forName(className).newInstance();
092: map.put(identifier, da);
093: instances = map;
094: } catch (Exception e) {
095: throw new LookupError(
096: "Unable to create instantance of class '"
097: + className + '\'', e); //EXCEPTION
098: }
099: }
100: return da;
101: }
102:
103: private static class LookupError extends NestableError {
104: public LookupError(String msg, Throwable t) {
105: super(msg, t);
106: }
107: }
108: }
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