FileBasedConfigurationBuilder.java
/*
* 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.commons.configuration2.builder;
import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;
import org.apache.commons.configuration2.FileBasedConfiguration;
import org.apache.commons.configuration2.PropertiesConfiguration;
import org.apache.commons.configuration2.XMLPropertiesConfiguration;
import org.apache.commons.configuration2.event.ConfigurationEvent;
import org.apache.commons.configuration2.ex.ConfigurationException;
import org.apache.commons.configuration2.io.FileHandler;
import org.apache.commons.lang3.ClassUtils;
import org.apache.commons.lang3.StringUtils;
/**
* <p>
* A specialized {@code ConfigurationBuilder} implementation which can handle configurations read from a
* {@link FileHandler}.
* </p>
* <p>
* This class extends its base class by the support of a {@link FileBasedBuilderParametersImpl} object, and especially
* of the {@link FileHandler} contained in this object. When the builder creates a new object the resulting
* {@code Configuration} instance is associated with the {@code FileHandler}. If the {@code FileHandler} has a location
* set, the {@code Configuration} is directly loaded from this location.
* </p>
* <p>
* The {@code FileHandler} is kept by this builder and can be queried later on. It can be used for instance to save the
* current {@code Configuration} after it was modified. Some care has to be taken when changing the location of the
* {@code FileHandler}: The new location is recorded and also survives an invocation of the {@code resetResult()}
* method. However, when the builder's initialization parameters are reset by calling {@code resetParameters()} the
* location is reset, too.
* </p>
*
* @since 2.0
* @param <T> the concrete type of {@code Configuration} objects created by this builder
*/
public class FileBasedConfigurationBuilder<T extends FileBasedConfiguration> extends BasicConfigurationBuilder<T> {
/** A map for storing default encodings for specific configuration classes. */
private static final Map<Class<?>, String> DEFAULT_ENCODINGS = initializeDefaultEncodings();
/**
* Gets the default encoding for the specified configuration class. If an encoding has been set for the specified
* class (or one of its super classes), it is returned. Otherwise, result is <b>null</b>.
*
* @param configClass the configuration class in question
* @return the default encoding for this class (may be <b>null</b>)
*/
public static String getDefaultEncoding(final Class<?> configClass) {
String enc = DEFAULT_ENCODINGS.get(configClass);
if (enc != null || configClass == null) {
return enc;
}
for (final Class<?> cls : ClassUtils.getAllSuperclasses(configClass)) {
enc = DEFAULT_ENCODINGS.get(cls);
if (enc != null) {
return enc;
}
}
for (final Class<?> cls : ClassUtils.getAllInterfaces(configClass)) {
enc = DEFAULT_ENCODINGS.get(cls);
if (enc != null) {
return enc;
}
}
return null;
}
/**
* Creates a map with default encodings for configuration classes and populates it with default entries.
*
* @return the map with default encodings
*/
private static Map<Class<?>, String> initializeDefaultEncodings() {
final Map<Class<?>, String> enc = new ConcurrentHashMap<>();
enc.put(PropertiesConfiguration.class, PropertiesConfiguration.DEFAULT_ENCODING);
enc.put(XMLPropertiesConfiguration.class, XMLPropertiesConfiguration.DEFAULT_ENCODING);
return enc;
}
/**
* Sets a default encoding for a specific configuration class. This encoding is used if an instance of this
* configuration class is to be created and no encoding has been set in the parameters object for this builder. The
* encoding passed here not only applies to the specified class but also to its sub classes. If the encoding is
* <b>null</b>, it is removed.
*
* @param configClass the name of the configuration class (must not be <b>null</b>)
* @param encoding the default encoding for this class
* @throws IllegalArgumentException if the class is <b>null</b>
*/
public static void setDefaultEncoding(final Class<?> configClass, final String encoding) {
if (configClass == null) {
throw new IllegalArgumentException("Configuration class must not be null!");
}
if (encoding == null) {
DEFAULT_ENCODINGS.remove(configClass);
} else {
DEFAULT_ENCODINGS.put(configClass, encoding);
}
}
/** Stores the FileHandler associated with the current configuration. */
private FileHandler currentFileHandler;
/** A specialized listener for the auto save mechanism. */
private AutoSaveListener autoSaveListener;
/** A flag whether the builder's parameters were reset. */
private boolean resetParameters;
/**
* Creates a new instance of {@code FileBasedConfigurationBuilder} which produces result objects of the specified class.
*
* @param resCls the result class (must not be <b>null</b>
* @throws IllegalArgumentException if the result class is <b>null</b>
*/
public FileBasedConfigurationBuilder(final Class<? extends T> resCls) {
super(resCls);
}
/**
* Creates a new instance of {@code FileBasedConfigurationBuilder} which produces result objects of the specified class
* and sets initialization parameters.
*
* @param resCls the result class (must not be <b>null</b>
* @param params a map with initialization parameters
* @throws IllegalArgumentException if the result class is <b>null</b>
*/
public FileBasedConfigurationBuilder(final Class<? extends T> resCls, final Map<String, Object> params) {
super(resCls, params);
}
/**
* Creates a new instance of {@code FileBasedConfigurationBuilder} which produces result objects of the specified class
* and sets initialization parameters and the <em>allowFailOnInit</em> flag.
*
* @param resCls the result class (must not be <b>null</b>
* @param params a map with initialization parameters
* @param allowFailOnInit the <em>allowFailOnInit</em> flag
* @throws IllegalArgumentException if the result class is <b>null</b>
*/
public FileBasedConfigurationBuilder(final Class<? extends T> resCls, final Map<String, Object> params, final boolean allowFailOnInit) {
super(resCls, params, allowFailOnInit);
}
/**
* {@inheritDoc} This method is overridden here to change the result type.
*/
@Override
public FileBasedConfigurationBuilder<T> configure(final BuilderParameters... params) {
super.configure(params);
return this;
}
/**
* Obtains the {@code FileHandler} from this builder's parameters. If no {@code FileBasedBuilderParametersImpl} object
* is found in this builder's parameters, a new one is created now and stored. This makes it possible to change the
* location of the associated file even if no parameters object was provided.
*
* @return the {@code FileHandler} from initialization parameters
*/
private FileHandler fetchFileHandlerFromParameters() {
FileBasedBuilderParametersImpl fileParams = FileBasedBuilderParametersImpl.fromParameters(getParameters(), false);
if (fileParams == null) {
fileParams = new FileBasedBuilderParametersImpl();
addParameters(fileParams.getParameters());
}
return fileParams.getFileHandler();
}
/**
* Gets the {@code FileHandler} associated with this builder. If already a result object has been created, this
* {@code FileHandler} can be used to save it. Otherwise, the {@code FileHandler} from the initialization parameters is
* returned (which is not associated with a {@code FileBased} object). Result is never <b>null</b>.
*
* @return the {@code FileHandler} associated with this builder
*/
public synchronized FileHandler getFileHandler() {
return currentFileHandler != null ? currentFileHandler : fetchFileHandlerFromParameters();
}
/**
* Initializes the encoding of the specified file handler. If already an encoding is set, it is used. Otherwise, the
* default encoding for the result configuration class is obtained and set.
*
* @param handler the handler to be initialized
*/
private void initEncoding(final FileHandler handler) {
if (StringUtils.isEmpty(handler.getEncoding())) {
final String encoding = getDefaultEncoding(getResultClass());
if (encoding != null) {
handler.setEncoding(encoding);
}
}
}
/**
* Initializes the new current {@code FileHandler}. When a new result object is created, a new {@code FileHandler} is
* created, too, and associated with the result object. This new handler is passed to this method. If a location is
* defined, the result object is loaded from this location. Note: This method is called from a synchronized block.
*
* @param handler the new current {@code FileHandler}
* @throws ConfigurationException if an error occurs
*/
protected void initFileHandler(final FileHandler handler) throws ConfigurationException {
initEncoding(handler);
if (handler.isLocationDefined()) {
handler.locate();
handler.load();
}
}
/**
* {@inheritDoc} This implementation deals with the creation and initialization of a {@code FileHandler} associated with
* the new result object.
*/
@Override
protected void initResultInstance(final T obj) throws ConfigurationException {
super.initResultInstance(obj);
final FileHandler srcHandler = currentFileHandler != null && !resetParameters ? currentFileHandler : fetchFileHandlerFromParameters();
currentFileHandler = new FileHandler(obj, srcHandler);
if (autoSaveListener != null) {
autoSaveListener.updateFileHandler(currentFileHandler);
}
initFileHandler(currentFileHandler);
resetParameters = false;
}
/**
* Installs the listener for the auto save mechanism if it is not yet active.
*/
private void installAutoSaveListener() {
if (autoSaveListener == null) {
autoSaveListener = new AutoSaveListener(this);
addEventListener(ConfigurationEvent.ANY, autoSaveListener);
autoSaveListener.updateFileHandler(getFileHandler());
}
}
/**
* Gets a flag whether auto save mode is currently active.
*
* @return <b>true</b> if auto save is enabled, <b>false</b> otherwise
*/
public synchronized boolean isAutoSave() {
return autoSaveListener != null;
}
/**
* Removes the listener for the auto save mechanism if it is currently active.
*/
private void removeAutoSaveListener() {
if (autoSaveListener != null) {
removeEventListener(ConfigurationEvent.ANY, autoSaveListener);
autoSaveListener.updateFileHandler(null);
autoSaveListener = null;
}
}
/**
* Convenience method which saves the associated configuration. This method expects that the managed configuration has
* already been created and that a valid file location is available in the current {@code FileHandler}. The file handler
* is then used to store the configuration.
*
* @throws ConfigurationException if an error occurs
*/
public void save() throws ConfigurationException {
getFileHandler().save();
}
/**
* Enables or disables auto save mode. If auto save mode is enabled, every update of the managed configuration causes it
* to be saved automatically; so changes are directly written to disk.
*
* @param enabled <b>true</b> if auto save mode is to be enabled, <b>false</b> otherwise
*/
public synchronized void setAutoSave(final boolean enabled) {
if (enabled) {
installAutoSaveListener();
} else {
removeAutoSaveListener();
}
}
/**
* {@inheritDoc} This implementation just records the fact that new parameters have been set. This means that the next
* time a result object is created, the {@code FileHandler} has to be initialized from initialization parameters rather
* than reusing the existing one.
*/
@Override
public synchronized BasicConfigurationBuilder<T> setParameters(final Map<String, Object> params) {
super.setParameters(params);
resetParameters = true;
return this;
}
}