/**************************************************************** * Licensed to the Apache Software Foundation (ASF) under one * * or more contributor license agreements. See the NOTICE file * * distributed with this work for additional information * * regarding copyright ownership. The ASF licenses this file * * to you under the Apache License, Version 2.0 (the * * "License"); you may not use this file except in compliance * * with the License. You may obtain a copy of the License at * * * * http://www.apache.org/licenses/LICENSE-2.0 * * * * Unless required by applicable law or agreed to in writing, * * software distributed under the License is distributed on an * * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY * * KIND, either express or implied. See the License for the * * specific language governing permissions and limitations * * under the License. * ****************************************************************/ package org.apache.james.mime4j.storage; /** * Allows for a default {@link StorageProvider} instance to be configured on an * application level. *
* The default instance can be set by either calling
* {@link #setInstance(StorageProvider)} when the application starts up or by
* setting the system property
* org.apache.james.mime4j.defaultStorageProvider
to the class
* name of a StorageProvider
implementation.
*
* If neither option is used or if the class instantiation fails this class
* provides a pre-configured default instance.
*/
public class DefaultStorageProvider {
/** Value is org.apache.james.mime4j.defaultStorageProvider
*/
public static final String DEFAULT_STORAGE_PROVIDER_PROPERTY =
"org.apache.james.mime4j.defaultStorageProvider";
private static volatile StorageProvider instance = null;
static {
initialize();
}
private DefaultStorageProvider() {
}
/**
* Returns the default {@link StorageProvider} instance.
*
* @return the default {@link StorageProvider} instance.
*/
public static StorageProvider getInstance() {
return instance;
}
/**
* Sets the default {@link StorageProvider} instance.
*
* @param instance
* the default {@link StorageProvider} instance.
*/
public static void setInstance(StorageProvider instance) {
if (instance == null) {
throw new IllegalArgumentException();
}
DefaultStorageProvider.instance = instance;
}
private static void initialize() {
String clazz = System.getProperty(DEFAULT_STORAGE_PROVIDER_PROPERTY);
try {
if (clazz != null) {
instance = (StorageProvider) Class.forName(clazz).newInstance();
}
} catch (Exception e) {
}
if (instance == null) {
StorageProvider backend = new TempFileStorageProvider();
instance = new ThresholdStorageProvider(backend, 1024);
}
}
// for unit tests only
static void reset() {
instance = null;
initialize();
}
}