cvs commit: jakarta-commons-sandbox/mapper/src/share/org/apache/commons/mapper/jdbc QueryLoader.java

[dg...@apache.org]

dgraham     2003/09/01 21:42:09

  Added:       mapper/src/share/org/apache/commons/mapper/jdbc
                        QueryLoader.java
  Log:
  Added QueryLoader to simplify the initialization of query Maps.
  
  Revision  Changes    Path
  1.1                  jakarta-commons-sandbox/mapper/src/share/org/apache/commons/mapper/jdbc/QueryLoader.java
  
  Index: QueryLoader.java
  ===================================================================
  /*
   * $Header: /home/cvs/jakarta-commons-sandbox/mapper/src/share/org/apache/commons/mapper/jdbc/QueryLoader.java,v 1.1 2003/09/02 04:42:09 dgraham Exp $
   * $Revision: 1.1 $
   * $Date: 2003/09/02 04:42:09 $
   *
   * ====================================================================
   *
   * The Apache Software License, Version 1.1
   *
   * Copyright (c) 2003 The Apache Software Foundation.  All rights
   * reserved.
   *
   * Redistribution and use in source and binary forms, with or without
   * modification, are permitted provided that the following conditions
   * are met:
   *
   * 1. Redistributions of source code must retain the above copyright
   *    notice, this list of conditions and the following disclaimer.
   *
   * 2. Redistributions in binary form must reproduce the above copyright
   *    notice, this list of conditions and the following disclaimer in
   *    the documentation and/or other materials provided with the
   *    distribution.
   *
   * 3. The end-user documentation included with the redistribution, if
   *    any, must include the following acknowlegement:
   *       "This product includes software developed by the
   *        Apache Software Foundation (http://www.apache.org/)."
   *    Alternately, this acknowlegement may appear in the software itself,
   *    if and wherever such third-party acknowlegements normally appear.
   *
   * 4. The names "The Jakarta Project", "Struts", and "Apache Software
   *    Foundation" must not be used to endorse or promote products derived
   *    from this software without prior written permission. For written
   *    permission, please contact apache@apache.org.
   *
   * 5. Products derived from this software may not be called "Apache"
   *    nor may "Apache" appear in their names without prior written
   *    permission of the Apache Group.
   *
   * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
   * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
   * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
   * DISCLAIMED.  IN NO EVENT SHALL THE APACHE SOFTWARE FOUNDATION OR
   * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
   * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
   * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
   * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
   * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
   * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
   * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   * SUCH DAMAGE.
   * ====================================================================
   *
   * This software consists of voluntary contributions made by many
   * individuals on behalf of the Apache Software Foundation.  For more
   * information on the Apache Software Foundation, please see
   * <http://www.apache.org/>.
   *
   */
  
  package org.apache.commons.mapper.jdbc;
  
  import java.io.IOException;
  import java.io.InputStream;
  import java.util.HashMap;
  import java.util.Map;
  import java.util.Properties;
  
  /**
   * QueryLoader loads properties files filled with query name to SQL mappings.
   * It acts as a registry for sets of queries so that multiple copies of the 
   * same queries aren't loaded into memory.
   * 
   * @author David Graham
   */
  public class QueryLoader {
  
      /**
       * The Singleton instance of this class.
       */
      private static final QueryLoader instance = new QueryLoader();
  
      /**
       * @return The Singleton instance.
       */
      public static QueryLoader getInstance() {
          return instance;
      }
  
      /**
       * Maps query set names to Maps of their queries.
       */
      private Map queries = new HashMap();
  
      /**
       * QueryLoader constructor.
       */
      protected QueryLoader() {
          super();
      }
  
      /**
       * Loads a Map of query names to SQL values.  The Maps are cached so a 
       * subsequent request to load queries from the same path will return
       * the cached Map.
       * @param path The path that the ClassLoader will use to find the file.
       * @throws IOException
       * @throws IllegalArgumentException if the ClassLoader can't find a file at
       * the given path.
       */
      public synchronized Map load(String path) throws IOException {
  
          Map queryMap = (Map) this.queries.get(path);
  
          if (queryMap == null) {
              queryMap = this.loadQueries(path);
              this.queries.put(path, queryMap);
          }
  
          return queryMap;
      }
  
      /**
       * Loads a properties file into a Map object.
       * @param path The path that the ClassLoader will use to find the file.
       * @throws IOException
       */
      private Map loadQueries(String path) throws IOException {
          InputStream in = QueryLoader.class.getResourceAsStream(path);
  
          if (in == null) {
              throw new IllegalArgumentException(path + " not found.");
          }
  
          Properties props = new Properties();
          props.load(in);
  
          return new HashMap(props);
      }
  
  }