org.springframework.web.servlet.resource.GzipResourceResolver.java Source code

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Here is the source code for org.springframework.web.servlet.resource.GzipResourceResolver.java

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/*
 * 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.web.servlet.resource;

import java.io.File;
import java.io.IOException;
import java.io.InputStream;
import java.net.URI;
import java.net.URL;
import java.util.List;
import javax.servlet.http.HttpServletRequest;

import org.springframework.core.io.AbstractResource;
import org.springframework.core.io.Resource;
import org.springframework.http.HttpHeaders;
import org.springframework.lang.Nullable;

/**
 * A {@code ResourceResolver} that delegates to the chain to locate a resource
 * and then attempts to find a variation with the ".gz" extension.
 *
 * <p>The resolver gets involved only if the "Accept-Encoding" request header
 * contains the value "gzip" indicating the client accepts gzipped responses.
 *
 * @author Jeremy Grelle
 * @author Rossen Stoyanchev
 * @author Sam Brannen
 * @since 4.1
 * @deprecated as of 5.1, in favor of using {@link EncodedResourceResolver}
 */
@Deprecated
public class GzipResourceResolver extends AbstractResourceResolver {

    @Override
    protected Resource resolveResourceInternal(@Nullable HttpServletRequest request, String requestPath,
            List<? extends Resource> locations, ResourceResolverChain chain) {

        Resource resource = chain.resolveResource(request, requestPath, locations);
        if (resource == null || (request != null && !isGzipAccepted(request))) {
            return resource;
        }

        try {
            Resource gzipped = new GzippedResource(resource);
            if (gzipped.exists()) {
                return gzipped;
            }
        } catch (IOException ex) {
            logger.trace("No gzip resource for [" + resource.getFilename() + "]", ex);
        }

        return resource;
    }

    private boolean isGzipAccepted(HttpServletRequest request) {
        String value = request.getHeader("Accept-Encoding");
        return (value != null && value.toLowerCase().contains("gzip"));
    }

    @Override
    protected String resolveUrlPathInternal(String resourceUrlPath, List<? extends Resource> locations,
            ResourceResolverChain chain) {

        return chain.resolveUrlPath(resourceUrlPath, locations);
    }

    /**
     * A gzipped {@link HttpResource}.
     */
    static final class GzippedResource extends AbstractResource implements HttpResource {

        private final Resource original;

        private final Resource gzipped;

        public GzippedResource(Resource original) throws IOException {
            this.original = original;
            this.gzipped = original.createRelative(original.getFilename() + ".gz");
        }

        @Override
        public InputStream getInputStream() throws IOException {
            return this.gzipped.getInputStream();
        }

        @Override
        public boolean exists() {
            return this.gzipped.exists();
        }

        @Override
        public boolean isReadable() {
            return this.gzipped.isReadable();
        }

        @Override
        public boolean isOpen() {
            return this.gzipped.isOpen();
        }

        @Override
        public boolean isFile() {
            return this.gzipped.isFile();
        }

        @Override
        public URL getURL() throws IOException {
            return this.gzipped.getURL();
        }

        @Override
        public URI getURI() throws IOException {
            return this.gzipped.getURI();
        }

        @Override
        public File getFile() throws IOException {
            return this.gzipped.getFile();
        }

        @Override
        public long contentLength() throws IOException {
            return this.gzipped.contentLength();
        }

        @Override
        public long lastModified() throws IOException {
            return this.gzipped.lastModified();
        }

        @Override
        public Resource createRelative(String relativePath) throws IOException {
            return this.gzipped.createRelative(relativePath);
        }

        @Override
        @Nullable
        public String getFilename() {
            return this.original.getFilename();
        }

        @Override
        public String getDescription() {
            return this.gzipped.getDescription();
        }

        @Override
        public HttpHeaders getResponseHeaders() {
            HttpHeaders headers = (this.original instanceof HttpResource
                    ? ((HttpResource) this.original).getResponseHeaders()
                    : new HttpHeaders());
            headers.add(HttpHeaders.CONTENT_ENCODING, "gzip");
            headers.add(HttpHeaders.VARY, HttpHeaders.ACCEPT_ENCODING);
            return headers;
        }
    }

}