PathBasedTemplateAvailabilityProvider.java

/*
 * Copyright 2012-2017 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
 *
 *      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.springframework.boot.autoconfigure.template;

import java.util.List;

import org.springframework.boot.autoconfigure.template.PathBasedTemplateAvailabilityProvider.TemplateAvailabilityProperties;
import org.springframework.boot.context.properties.bind.Binder;
import org.springframework.core.env.Environment;
import org.springframework.core.io.ResourceLoader;
import org.springframework.util.ClassUtils;

/**
 * Abstract base class for {@link TemplateAvailabilityProvider} implementations that find
 * templates from paths.
 *
 * @author Andy Wilkinson
 * @author Phillip Webb
 * @author Madhura Bhave
 * @since 1.4.6
 */
public abstract class PathBasedTemplateAvailabilityProvider<T extends TemplateAvailabilityProperties>
		implements TemplateAvailabilityProvider {

	private final String className;

	private final Class<T> propertiesClass;

	private final String propertyPrefix;

	public PathBasedTemplateAvailabilityProvider(String className,
			Class<T> propertiesClass, String propertyPrefix) {
		this.className = className;
		this.propertiesClass = propertiesClass;
		this.propertyPrefix = propertyPrefix;
	}

	@Override
	public boolean isTemplateAvailable(String view, Environment environment,
			ClassLoader classLoader, ResourceLoader resourceLoader) {
		if (ClassUtils.isPresent(this.className, classLoader)) {
			Binder binder = Binder.get(environment);
			TemplateAvailabilityProperties properties = binder
					.bind(this.propertyPrefix, this.propertiesClass)
					.orElseCreate(this.propertiesClass);
			return isTemplateAvailable(view, resourceLoader, properties);
		}
		return false;
	}

	private boolean isTemplateAvailable(String view, ResourceLoader resourceLoader,
			TemplateAvailabilityProperties properties) {
		String location = properties.getPrefix() + view + properties.getSuffix();
		for (String path : properties.getLoaderPath()) {
			if (resourceLoader.getResource(path + location).exists()) {
				return true;
			}
		}
		return false;
	}

	protected static abstract class TemplateAvailabilityProperties {

		private String prefix;

		private String suffix;

		protected TemplateAvailabilityProperties(String prefix, String suffix) {
			this.prefix = prefix;
			this.suffix = suffix;
		}

		protected abstract List<String> getLoaderPath();

		public String getPrefix() {
			return this.prefix;
		}

		public void setPrefix(String prefix) {
			this.prefix = prefix;
		}

		public String getSuffix() {
			return this.suffix;
		}

		public void setSuffix(String suffix) {
			this.suffix = suffix;
		}

	}

}