001// ***************************************************************************************************************************
002// * Licensed to the Apache Software Foundation (ASF) under one or more contributor license agreements.  See the NOTICE file *
003// * distributed with this work for additional information regarding copyright ownership.  The ASF licenses this file        *
004// * to you under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance            *
005// * with the License.  You may obtain a copy of the License at                                                              *
006// *                                                                                                                         *
007// *  http://www.apache.org/licenses/LICENSE-2.0                                                                             *
008// *                                                                                                                         *
009// * Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an  *
010// * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.  See the License for the        *
011// * specific language governing permissions and limitations under the License.                                              *
012// ***************************************************************************************************************************
013package org.apache.juneau.config.store;
014
015import static org.apache.juneau.internal.StringUtils.*;
016
017import java.io.*;
018import java.util.concurrent.*;
019
020import org.apache.juneau.*;
021import org.apache.juneau.internal.*;
022
023/**
024 * Classpath-based storage location for configuration files.
025 *
026 * <p>
027 * Looks inside the JVM classpath for configuration files.
028 *
029 * <p>
030 * Configuration files retrieved from the classpath can be modified but not persisted.
031 */
032public class ConfigClasspathStore extends ConfigStore {
033
034   //-------------------------------------------------------------------------------------------------------------------
035   // Predefined instances
036   //-------------------------------------------------------------------------------------------------------------------
037
038   /** Default memory store, all default values.*/
039   public static final ConfigClasspathStore DEFAULT = ConfigClasspathStore.create().build();
040
041
042   //-------------------------------------------------------------------------------------------------------------------
043   // Instance
044   //-------------------------------------------------------------------------------------------------------------------
045
046   /**
047    * Create a new builder for this object.
048    *
049    * @return A new builder for this object.
050    */
051   public static ConfigClasspathStoreBuilder create() {
052      return new ConfigClasspathStoreBuilder();
053   }
054
055   @Override /* Context */
056   public ConfigClasspathStoreBuilder builder() {
057      return new ConfigClasspathStoreBuilder(getPropertyStore());
058   }
059
060   private final ConcurrentHashMap<String,String> cache = new ConcurrentHashMap<>();
061
062   /**
063    * Constructor.
064    *
065    * @param ps The settings for this content store.
066    */
067   protected ConfigClasspathStore(PropertyStore ps) {
068      super(ps);
069   }
070
071   @Override /* ConfigStore */
072   public synchronized String read(String name) throws IOException {
073      String s = cache.get(name);
074      if (s != null)
075         return s;
076
077      ClassLoader cl = Thread.currentThread().getContextClassLoader();
078      try (InputStream in = cl.getResourceAsStream(name)) {
079         if (in != null)
080            cache.put(name, IOUtils.read(in, IOUtils.UTF8));
081      }
082      return emptyIfNull(cache.get(name));
083   }
084
085   @Override /* ConfigStore */
086   public synchronized String write(String name, String expectedContents, String newContents) throws IOException {
087
088      // This is a no-op.
089      if (isEquals(expectedContents, newContents))
090         return null;
091
092      String currentContents = read(name);
093
094      if (expectedContents != null && ! isEquals(currentContents, expectedContents))
095         return currentContents;
096
097      update(name, newContents);
098
099      return null;
100   }
101
102   @Override /* ConfigStore */
103   public synchronized boolean exists(String name) {
104      try {
105         return ! read(name).isEmpty();
106      } catch (IOException e) {
107         return false;
108      }
109   }
110
111   @Override /* ConfigStore */
112   public synchronized ConfigClasspathStore update(String name, String newContents) {
113      if (newContents == null)
114         cache.remove(name);
115      else
116         cache.put(name, newContents);
117      super.update(name, newContents);
118      return this;
119   }
120
121   /**
122    * No-op.
123    */
124   @Override /* Closeable */
125   public void close() throws IOException {
126      // No-op
127   }
128}