de.codecentric.boot.admin.web.servlet.resource.PreferMinifiedFilteringResourceResolver.java Source code

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Here is the source code for de.codecentric.boot.admin.web.servlet.resource.PreferMinifiedFilteringResourceResolver.java

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/*
 * Copyright 2014 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 de.codecentric.boot.admin.web.servlet.resource;

import java.io.IOException;
import java.util.ArrayList;
import java.util.List;

import javax.servlet.http.HttpServletRequest;

import org.springframework.core.io.Resource;
import org.springframework.util.StringUtils;
import org.springframework.web.servlet.resource.AbstractResourceResolver;
import org.springframework.web.servlet.resource.ResourceResolver;
import org.springframework.web.servlet.resource.ResourceResolverChain;

/**
 * {@link ResourceResolver} which is looking for minified version of resources.
 *
 * @author Johannes Edmeier
 */
public class PreferMinifiedFilteringResourceResolver extends AbstractResourceResolver {

    private final String extensionPrefix;

    public PreferMinifiedFilteringResourceResolver(String extensionPrefix) {
        this.extensionPrefix = extensionPrefix;
    }

    @Override
    protected Resource resolveResourceInternal(HttpServletRequest request, String requestPath,
            List<? extends Resource> locations, ResourceResolverChain chain) {
        List<Resource> newLocations = new ArrayList<Resource>(locations.size());

        for (Resource location : locations) {
            Resource minified = findMinified(location);
            newLocations.add(minified != null ? minified : location);
        }

        return chain.resolveResource(request, requestPath, newLocations);
    }

    private Resource findMinified(Resource resource) {
        try {
            String basename = StringUtils.stripFilenameExtension(resource.getFilename());
            String extension = StringUtils.getFilenameExtension(resource.getFilename());
            Resource minified = resource.createRelative(basename + extensionPrefix + '.' + extension);
            if (minified.exists()) {
                return minified;
            }
        } catch (IOException ex) {
            logger.trace("No minified resource for [" + resource.getFilename() + "]", ex);
        }
        return null;
    }

    @Override
    protected String resolveUrlPathInternal(String resourceUrlPath, List<? extends Resource> locations,
            ResourceResolverChain chain) {
        return chain.resolveUrlPath(resourceUrlPath, locations);
    }

}