CachedResource.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.catalina.webresources;
import java.io.ByteArrayInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.net.JarURLConnection;
import java.net.MalformedURLException;
import java.net.URI;
import java.net.URISyntaxException;
import java.net.URL;
import java.net.URLConnection;
import java.net.URLStreamHandler;
import java.nio.charset.Charset;
import java.security.Permission;
import java.security.cert.Certificate;
import java.text.Collator;
import java.util.Arrays;
import java.util.Locale;
import java.util.jar.JarFile;
import java.util.jar.Manifest;
import org.apache.catalina.WebResource;
import org.apache.catalina.WebResourceRoot;
import org.apache.juli.logging.Log;
import org.apache.juli.logging.LogFactory;
import org.apache.tomcat.util.res.StringManager;
/**
* This class is designed to wrap a 'raw' WebResource and providing caching for expensive operations. Inexpensive
* operations may be passed through to the underlying resource.
*/
public class CachedResource implements WebResource {
private static final Log log = LogFactory.getLog(CachedResource.class);
private static final StringManager sm = StringManager.getManager(CachedResource.class);
// Estimate (on high side to be safe) of average size excluding content
// based on profiler data.
private static final long CACHE_ENTRY_SIZE = 500;
private final Cache cache;
private final StandardRoot root;
private final String webAppPath;
private final long ttl;
private final int objectMaxSizeBytes;
private final boolean usesClassLoaderResources;
private volatile WebResource webResource;
private volatile WebResource[] webResources;
private volatile long nextCheck;
private volatile Long cachedLastModified = null;
private volatile String cachedLastModifiedHttp = null;
private volatile byte[] cachedContent = null;
private volatile Boolean cachedIsFile = null;
private volatile Boolean cachedIsDirectory = null;
private volatile Boolean cachedExists = null;
private volatile Boolean cachedIsVirtual = null;
private volatile Long cachedContentLength = null;
public CachedResource(Cache cache, StandardRoot root, String path, long ttl, int objectMaxSizeBytes,
boolean usesClassLoaderResources) {
this.cache = cache;
this.root = root;
this.webAppPath = path;
this.ttl = ttl;
this.objectMaxSizeBytes = objectMaxSizeBytes;
this.usesClassLoaderResources = usesClassLoaderResources;
}
protected boolean validateResource(boolean useClassLoaderResources) {
// It is possible that some resources will only be visible for a given
// value of useClassLoaderResources. Therefore, if the lookup is made
// with a different value of useClassLoaderResources than was used when
// creating the cache entry, invalidate the entry. This should have
// minimal performance impact as it would be unusual for a resource to
// be looked up both as a static resource and as a class loader
// resource.
if (usesClassLoaderResources != useClassLoaderResources) {
return false;
}
long now = System.currentTimeMillis();
if (webResource == null) {
synchronized (this) {
if (webResource == null) {
webResource = root.getResourceInternal(webAppPath, useClassLoaderResources);
getLastModified();
getContentLength();
nextCheck = ttl + now;
// exists() is a relatively expensive check for a file so
// use the fact that we know if it exists at this point
if (webResource instanceof EmptyResource) {
cachedExists = Boolean.FALSE;
} else {
cachedExists = Boolean.TRUE;
}
return true;
}
}
}
if (now < nextCheck) {
return true;
}
// Assume resources inside WARs will not change
if (!root.isPackedWarFile()) {
WebResource webResourceInternal = root.getResourceInternal(webAppPath, useClassLoaderResources);
if (!webResource.exists() && webResourceInternal.exists()) {
return false;
}
// If modified date or length change - resource has changed / been
// removed etc.
if (webResource.getLastModified() != getLastModified() ||
webResource.getContentLength() != getContentLength()) {
return false;
}
// Has a resource been inserted / removed in a different resource set
if (webResource.getLastModified() != webResourceInternal.getLastModified() ||
webResource.getContentLength() != webResourceInternal.getContentLength()) {
return false;
}
}
nextCheck = ttl + now;
return true;
}
protected boolean validateResources(boolean useClassLoaderResources) {
long now = System.currentTimeMillis();
if (webResources == null) {
synchronized (this) {
if (webResources == null) {
webResources = root.getResourcesInternal(webAppPath, useClassLoaderResources);
nextCheck = ttl + now;
return true;
}
}
}
if (now < nextCheck) {
return true;
}
// Assume resources inside WARs will not change
if (root.isPackedWarFile()) {
nextCheck = ttl + now;
return true;
} else {
// At this point, always expire the entry and re-populating it is
// likely to be as expensive as validating it.
return false;
}
}
protected long getNextCheck() {
return nextCheck;
}
@Override
public long getLastModified() {
if (cachedLastModified == null) {
cachedLastModified = Long.valueOf(webResource.getLastModified());
}
return cachedLastModified.longValue();
}
@Override
public String getLastModifiedHttp() {
if (cachedLastModifiedHttp == null) {
cachedLastModifiedHttp = webResource.getLastModifiedHttp();
}
return cachedLastModifiedHttp;
}
@Override
public boolean exists() {
if (cachedExists == null) {
cachedExists = Boolean.valueOf(webResource.exists());
}
return cachedExists.booleanValue();
}
@Override
public boolean isVirtual() {
if (cachedIsVirtual == null) {
cachedIsVirtual = Boolean.valueOf(webResource.isVirtual());
}
return cachedIsVirtual.booleanValue();
}
@Override
public boolean isDirectory() {
if (cachedIsDirectory == null) {
cachedIsDirectory = Boolean.valueOf(webResource.isDirectory());
}
return cachedIsDirectory.booleanValue();
}
@Override
public boolean isFile() {
if (cachedIsFile == null) {
cachedIsFile = Boolean.valueOf(webResource.isFile());
}
return cachedIsFile.booleanValue();
}
@Override
public boolean delete() {
boolean deleteResult = webResource.delete();
if (deleteResult) {
cache.removeCacheEntry(webAppPath);
}
return deleteResult;
}
@Override
public String getName() {
return webResource.getName();
}
@Override
public long getContentLength() {
if (cachedContentLength == null) {
long result = 0;
if (webResource != null) {
result = webResource.getContentLength();
cachedContentLength = Long.valueOf(result);
}
return result;
}
return cachedContentLength.longValue();
}
@Override
public String getCanonicalPath() {
return webResource.getCanonicalPath();
}
@Override
public boolean canRead() {
return webResource.canRead();
}
@Override
public String getWebappPath() {
return webAppPath;
}
@Override
public String getETag() {
return webResource.getETag();
}
@Override
public void setMimeType(String mimeType) {
webResource.setMimeType(mimeType);
}
@Override
public String getMimeType() {
return webResource.getMimeType();
}
@Override
public InputStream getInputStream() {
byte[] content = getContent();
if (content == null) {
// Can't cache InputStreams
return webResource.getInputStream();
}
return new ByteArrayInputStream(content);
}
@Override
public byte[] getContent() {
if (cachedContent == null) {
if (getContentLength() > objectMaxSizeBytes) {
return null;
}
cachedContent = webResource.getContent();
}
return cachedContent;
}
@Override
public long getCreation() {
return webResource.getCreation();
}
@Override
public URL getURL() {
/*
* We don't want applications using this URL to access the resource directly as that could lead to inconsistent
* results when the resource is updated on the file system but the cache entry has not yet expired. We saw this,
* for example, in JSP compilation.
*
* - last modified time was obtained via ServletContext.getResource("path").openConnection().getLastModified()
*
* - JSP content was obtained via ServletContext.getResourceAsStream("path")
*
* The result was that the JSP modification was detected but the JSP content was read from the cache so the
* non-updated JSP page was used to generate the .java and .class file
*
* One option to resolve this issue is to use a custom URL scheme for resource URLs. This would allow us, via
* registration of a URLStreamHandlerFactory, to control how the resources are accessed and ensure that all
* access go via the cache. We took this approach for war: URLs so we can use jar:war:file: URLs to reference
* resources in unpacked WAR files. However, because URL.setURLStreamHandlerFactory() may only be called once,
* this can cause problems when using other libraries that also want to use a custom URL scheme.
*
* The approach below allows us to insert a custom URLStreamHandler without registering a custom protocol. The
* only limitation (compared to registering a custom protocol) is that if the application constructs the same
* URL from a String, they will access the resource directly and not via the cache.
*/
URL resourceURL = webResource.getURL();
if (resourceURL == null) {
return null;
}
try {
CachedResourceURLStreamHandler handler = new CachedResourceURLStreamHandler(resourceURL, root, webAppPath,
usesClassLoaderResources);
URL result = new URL(null, resourceURL.toExternalForm(), handler);
handler.setCacheURL(result);
return result;
} catch (MalformedURLException e) {
log.error(sm.getString("cachedResource.invalidURL", resourceURL.toExternalForm()), e);
return null;
}
}
@Override
public URL getCodeBase() {
return webResource.getCodeBase();
}
@Override
public Certificate[] getCertificates() {
return webResource.getCertificates();
}
@Override
public Manifest getManifest() {
return webResource.getManifest();
}
@Override
public WebResourceRoot getWebResourceRoot() {
return webResource.getWebResourceRoot();
}
WebResource getWebResource() {
return webResource;
}
WebResource[] getWebResources() {
return webResources;
}
boolean usesClassLoaderResources() {
return usesClassLoaderResources;
}
// Assume that the cache entry will always include the content unless the
// resource content is larger than objectMaxSizeBytes. This isn't always the
// case but it makes tracking the current cache size easier.
long getSize() {
long result = CACHE_ENTRY_SIZE;
// Longer paths use a noticeable amount of memory so account for this in
// the cache size. The fixed component of a String instance's memory
// usage is accounted for in the 500 bytes above.
result += getWebappPath().length() * 2;
if (getContentLength() <= objectMaxSizeBytes) {
result += getContentLength();
}
return result;
}
/*
* Mimics the behaviour of FileURLConnection.getInputStream for a directory. Deliberately uses default locale.
*/
private static InputStream buildInputStream(String[] files) {
Arrays.sort(files, Collator.getInstance(Locale.getDefault()));
StringBuilder result = new StringBuilder();
for (String file : files) {
result.append(file);
// Every entry is followed by \n including the last
result.append('\n');
}
return new ByteArrayInputStream(result.toString().getBytes(Charset.defaultCharset()));
}
/**
* URLStreamHandler to handle a URL for a cached resource, delegating reads to the Cache.
* <ul>
* <li>delegates reads to the Cache, to ensure consistent invalidation behavior</li>
* <li>delegates hashCode()/ equals() behavior to the underlying Resource URL. (Equinox/ OSGi compatibility)</li>
* <li>detects the case where a new relative URL is created from the wrapped URL, inheriting its handler; in this
* case reverts to default behavior</li>
* </ul>
*/
private static class CachedResourceURLStreamHandler extends URLStreamHandler {
private final URL resourceURL;
private final StandardRoot root;
private final String webAppPath;
private final boolean usesClassLoaderResources;
private URL cacheURL = null;
CachedResourceURLStreamHandler(URL resourceURL, StandardRoot root, String webAppPath,
boolean usesClassLoaderResources) {
this.resourceURL = resourceURL;
this.root = root;
this.webAppPath = webAppPath;
this.usesClassLoaderResources = usesClassLoaderResources;
}
protected void setCacheURL(URL cacheURL) {
this.cacheURL = cacheURL;
}
@Override
protected URLConnection openConnection(URL u) throws IOException {
// This deliberately uses ==. If u isn't the URL object this
// URLStreamHandler was constructed for we do not want to use this
// URLStreamHandler to create a connection.
if (cacheURL != null && u == cacheURL) {
if ("jar".equals(cacheURL.getProtocol())) {
return new CachedResourceJarURLConnection(resourceURL, root, webAppPath, usesClassLoaderResources);
} else {
return new CachedResourceURLConnection(resourceURL, root, webAppPath, usesClassLoaderResources);
}
} else {
// This stream handler has been inherited by a URL that was constructed from a cache URL.
// We need to break that link.
URI constructedURI;
try {
constructedURI = new URI(u.toExternalForm());
} catch (URISyntaxException e) {
// Not ideal but consistent with API
throw new IOException(e);
}
URL constructedURL = constructedURI.toURL();
return constructedURL.openConnection();
}
}
/**
* {@inheritDoc}
* <p>
* We don't know what the requirements are for equals for the wrapped resourceURL so if u1 is the cacheURL,
* delegate to the resourceURL and it's handler. Otherwise, use the default implementation from
* URLStreamHandler.
*/
@Override
protected boolean equals(URL u1, URL u2) {
// Deliberate use of ==
if (cacheURL == u1) {
return resourceURL.equals(u2);
}
// Not the cacheURL. This stream handler has been inherited by a URL that was constructed from a cache URL.
// Use the default implementation from URLStreamHandler.
return super.equals(u1, u2);
}
/**
* {@inheritDoc}
* <p>
* We don't know what the requirements are for hashcode for the wrapped resourceURL so if u1 is the cacheURL,
* delegate to the resourceURL and it's handler. Otherwise, use the default implementation from
* URLStreamHandler.
*/
@Override
protected int hashCode(URL u) {
// Deliberate use of ==
if (cacheURL == u) {
return resourceURL.hashCode();
}
// Not the cacheURL. This stream handler has been inherited by a URL that was constructed from a cache URL.
// Use the default implementation from URLStreamHandler.
return super.hashCode(u);
}
}
/*
* Keep this in sync with CachedResourceJarURLConnection.
*/
private static class CachedResourceURLConnection extends URLConnection {
private final StandardRoot root;
private final String webAppPath;
private final boolean usesClassLoaderResources;
private final URL resourceURL;
protected CachedResourceURLConnection(URL resourceURL, StandardRoot root, String webAppPath,
boolean usesClassLoaderResources) {
super(resourceURL);
this.root = root;
this.webAppPath = webAppPath;
this.usesClassLoaderResources = usesClassLoaderResources;
this.resourceURL = resourceURL;
}
@Override
public void connect() throws IOException {
// NO-OP
}
@Override
public InputStream getInputStream() throws IOException {
WebResource resource = getResource();
if (resource.isDirectory()) {
return buildInputStream(resource.getWebResourceRoot().list(webAppPath));
} else {
return getResource().getInputStream();
}
}
@Override
public Permission getPermission() throws IOException {
// Doesn't trigger a call to connect for file:// URLs
return resourceURL.openConnection().getPermission();
}
@Override
public long getLastModified() {
return getResource().getLastModified();
}
@Override
public long getContentLengthLong() {
return getResource().getContentLength();
}
private WebResource getResource() {
return root.getResource(webAppPath, false, usesClassLoaderResources);
}
}
/*
* Keep this in sync with CachedResourceURLConnection.
*/
private static class CachedResourceJarURLConnection extends JarURLConnection {
private final StandardRoot root;
private final String webAppPath;
private final boolean usesClassLoaderResources;
private final URL resourceURL;
protected CachedResourceJarURLConnection(URL resourceURL, StandardRoot root, String webAppPath,
boolean usesClassLoaderResources) throws IOException {
super(resourceURL);
this.root = root;
this.webAppPath = webAppPath;
this.usesClassLoaderResources = usesClassLoaderResources;
this.resourceURL = resourceURL;
}
@Override
public void connect() throws IOException {
// NO-OP
}
@Override
public InputStream getInputStream() throws IOException {
WebResource resource = getResource();
if (resource.isDirectory()) {
return buildInputStream(resource.getWebResourceRoot().list(webAppPath));
} else {
return getResource().getInputStream();
}
}
@Override
public Permission getPermission() throws IOException {
// Doesn't trigger a call to connect for jar:// URLs
return resourceURL.openConnection().getPermission();
}
@Override
public long getLastModified() {
return getResource().getLastModified();
}
@Override
public long getContentLengthLong() {
return getResource().getContentLength();
}
private WebResource getResource() {
return root.getResource(webAppPath, false, usesClassLoaderResources);
}
@Override
public JarFile getJarFile() throws IOException {
return ((JarURLConnection) resourceURL.openConnection()).getJarFile();
}
}
}