/*
 * Copyright 2002-2018 the original author or authors.
 *
 * Licensed 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
 *
 *      https://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.springframework.core.env;

import org.springframework.lang.Nullable;

PropertyResolver implementation that resolves property values against an underlying set of PropertySources. 
Author:
Chris Beams, Juergen Hoeller
See Also:
PropertySource
PropertySources
AbstractEnvironment
Since:
3.1/**
 * {@link PropertyResolver} implementation that resolves property values against
 * an underlying set of {@link PropertySources}.
 *
 * @author Chris Beams
 * @author Juergen Hoeller
 * @since 3.1
 * @see PropertySource
 * @see PropertySources
 * @see AbstractEnvironment
 */
public class PropertySourcesPropertyResolver extends AbstractPropertyResolver {

	@Nullable
	private final PropertySources propertySources;


	
Create a new resolver against the given property sources.
Params:
propertySources – the set of PropertySource objects to use/**
	 * Create a new resolver against the given property sources.
	 * @param propertySources the set of {@link PropertySource} objects to use
	 */
	public PropertySourcesPropertyResolver(@Nullable PropertySources propertySources) {
		this.propertySources = propertySources;
	}


	@Override
	public boolean containsProperty(String key) {
		if (this.propertySources != null) {
			for (PropertySource<?> propertySource : this.propertySources) {
				if (propertySource.containsProperty(key)) {
					return true;
				}
			}
		}
		return false;
	}

	@Override
	@Nullable
	public String getProperty(String key) {
		return getProperty(key, String.class, true);
	}

	@Override
	@Nullable
	public <T> T getProperty(String key, Class<T> targetValueType) {
		return getProperty(key, targetValueType, true);
	}

	@Override
	@Nullable
	protected String getPropertyAsRawString(String key) {
		return getProperty(key, String.class, false);
	}

	@Nullable
	protected <T> T getProperty(String key, Class<T> targetValueType, boolean resolveNestedPlaceholders) {
		if (this.propertySources != null) {
			for (PropertySource<?> propertySource : this.propertySources) {
				if (logger.isTraceEnabled()) {
					logger.trace("Searching for key '" + key + "' in PropertySource '" +
							propertySource.getName() + "'");
				}
				Object value = propertySource.getProperty(key);
				if (value != null) {
					if (resolveNestedPlaceholders && value instanceof String) {
						value = resolveNestedPlaceholders((String) value);
					}
					logKeyFound(key, propertySource, value);
					return convertValueIfNecessary(value, targetValueType);
				}
			}
		}
		if (logger.isTraceEnabled()) {
			logger.trace("Could not find key '" + key + "' in any property source");
		}
		return null;
	}

	
Log the given key as found in the given PropertySource, resulting in the given value. 
The default implementation writes a debug log message with key and source.
As of 4.3.3, this does not log the value anymore in order to avoid accidental
logging of sensitive settings. Subclasses may override this method to change
the log level and/or log message, including the property's value if desired.
Params:
key – the key found
propertySource – the PropertySource that the key has been found in
value – the corresponding value
Since:
4.3.1/**
	 * Log the given key as found in the given {@link PropertySource}, resulting in
	 * the given value.
	 * <p>The default implementation writes a debug log message with key and source.
	 * As of 4.3.3, this does not log the value anymore in order to avoid accidental
	 * logging of sensitive settings. Subclasses may override this method to change
	 * the log level and/or log message, including the property's value if desired.
	 * @param key the key found
	 * @param propertySource the {@code PropertySource} that the key has been found in
	 * @param value the corresponding value
	 * @since 4.3.1
	 */
	protected void logKeyFound(String key, PropertySource<?> propertySource, Object value) {
		if (logger.isDebugEnabled()) {
			logger.debug("Found key '" + key + "' in PropertySource '" + propertySource.getName() +
					"' with value of type " + value.getClass().getSimpleName());
		}
	}

}