com.github.jjYBdx4IL.utils.cache.SimpleDiskCacheEntry Maven / Gradle / Ivy
/*
* Copyright (C) 2016 jjYBdx4IL (https://github.com/jjYBdx4IL)
*
* 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 com.github.jjYBdx4IL.utils.cache;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.net.MalformedURLException;
import java.net.URL;
import java.nio.charset.Charset;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import org.apache.commons.codec.binary.Hex;
import org.apache.commons.io.FileUtils;
import org.apache.commons.io.IOUtils;
import org.apache.http.client.methods.CloseableHttpResponse;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.impl.client.CloseableHttpClient;
import org.apache.http.impl.client.HttpClients;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
/**
*
* @author jjYBdx4IL
*/
public class SimpleDiskCacheEntry {
public static final String APP_NAME = "SimpleDiskCache";
public static final String PROPNAME_CACHE_DIR = APP_NAME + ".dir";
private static final Logger log = LoggerFactory.getLogger(SimpleDiskCacheEntry.class);
public static final UpdateMode DEFAULT_UPDATE_MODE = UpdateMode.DAILY;
private final File localCacheFile;
private final URL url;
private final String urlMD5;
private final UpdateMode updateMode;
public SimpleDiskCacheEntry(URL url, File localCacheFile, UpdateMode updateMode)
throws MalformedURLException {
this.url = new URL(url.toString());
this.urlMD5 = md5();
this.localCacheFile = localCacheFile != null ? new File(localCacheFile.getPath()) : computeDiskCacheFile(url);
this.updateMode = updateMode;
}
public SimpleDiskCacheEntry(URL url, UpdateMode updateMode) throws MalformedURLException {
this(url, null, updateMode);
}
public SimpleDiskCacheEntry(URL url) throws MalformedURLException {
this(url, null, DEFAULT_UPDATE_MODE);
}
public SimpleDiskCacheEntry(String url, File localCacheFile, UpdateMode updateMode)
throws MalformedURLException {
this(new URL(url), localCacheFile, updateMode);
}
public SimpleDiskCacheEntry(String url, UpdateMode updateMode) throws MalformedURLException {
this(new URL(url), null, updateMode);
}
public SimpleDiskCacheEntry(String url) throws MalformedURLException {
this(new URL(url), null, DEFAULT_UPDATE_MODE);
}
private File getCacheDir() {
String propCacheDir = System.getProperty(PROPNAME_CACHE_DIR);
if (propCacheDir != null) {
return new File(propCacheDir);
}
String userHome = System.getProperty("user.home");
if (userHome == null || userHome.length() == 0) {
throw new IllegalArgumentException("environment variable user home is not set or empty");
}
return new File(new File(userHome, ".cache"), APP_NAME);
}
private File computeDiskCacheFile(URL url) {
return new File(getCacheDir(), urlMD5);
}
private String md5() {
try {
final MessageDigest messageDigest = MessageDigest.getInstance("MD5");
messageDigest.reset();
messageDigest.update(url.toExternalForm().getBytes(Charset.forName("UTF8")));
final byte[] resultByte = messageDigest.digest();
return Hex.encodeHexString(resultByte);
} catch (NoSuchAlgorithmException ex) {
throw new IllegalStateException(ex);
}
}
protected boolean isUpdateRequired() {
if (!localCacheFile.exists() || updateMode.equals(UpdateMode.ALWAYS)) {
log.debug("local copy not found");
return true;
}
SimpleDiskCacheEntryHeader header;
// hint: do NOT use try-with-resources directly on the ObjectInputStream
// -- it won't close the underlying FileInputStream reliably....
try (InputStream is = new FileInputStream(localCacheFile)) {
ObjectInputStream ois = new ObjectInputStream(is);
header = (SimpleDiskCacheEntryHeader) ois.readObject();
log.debug(header.toString());
} catch (IOException | ClassNotFoundException | ClassCastException ex) {
log.warn("cached file's header is corrupt, discarding cached file", ex);
return true;
}
if (log.isDebugEnabled()) {
log.debug("getUrl() = " + getUrl().toExternalForm());
}
if (!getUrl().toExternalForm().equals(header.getUrl())) {
log.debug("url changed, discarding cached file");
return true;
}
if (updateMode.equals(UpdateMode.NEVER)) {
log.debug("update mode NEVER, using cached file");
return false;
}
if (header.getAgeSeconds() > updateMode.getExpireSeconds()) {
log.debug("local copy too old, discarding cached file");
return true;
}
log.debug("using cached file");
return false;
}
/**
* @return the localCacheFile
*/
protected File getLocalCacheFile() {
return localCacheFile;
}
/**
* @return the url
*/
protected URL getUrl() {
return url;
}
public InputStream getInputStream() throws IOException {
return getInputStream(false);
}
public InputStream getInputStream(boolean allowFallback) throws IOException {
log.debug("getInputStream " + getLocalCacheFile().getPath());
if (isUpdateRequired()) {
try {
File localTempFile = new File(getLocalCacheFile().getPath() + ".tmp");
if (localTempFile.exists() && !localTempFile.delete()) {
throw new RuntimeException("failed to delete " + localTempFile.getAbsolutePath());
}
localTempFile.deleteOnExit();
File parentDir = localTempFile.getParentFile();
if (!parentDir.exists()) {
parentDir.mkdirs();
}
if (!parentDir.exists()) {
throw new IOException("failed to create parent directory " + parentDir.getAbsolutePath());
}
log.debug("downloading " + getUrl().toString() + " to " + localTempFile.getPath());
try (CloseableHttpClient httpclient = HttpClients.createDefault()) {
HttpGet httpGet = new HttpGet(getUrl().toExternalForm());
try (CloseableHttpResponse response = httpclient.execute(httpGet)) {
int sc = response.getStatusLine().getStatusCode();
if (sc != 200) {
throw new IOException(String.format("%s (%d)",
response.getStatusLine().getReasonPhrase(), sc));
}
try (FileOutputStream fos = new FileOutputStream(localTempFile)) {
try (ObjectOutputStream oos = new ObjectOutputStream(fos)) {
oos.writeObject(new SimpleDiskCacheEntryHeader(getUrl()));
IOUtils.copyLarge(response.getEntity().getContent(), fos);
}
}
}
}
if (getLocalCacheFile().exists() && !getLocalCacheFile().delete()) {
throw new RuntimeException("failed to delete " + getLocalCacheFile().getAbsolutePath());
}
FileUtils.moveFile(localTempFile, getLocalCacheFile());
} catch (IOException ex) {
if (!allowFallback || !getLocalCacheFile().exists()) {
throw new IOException(ex);
}
log.warn("download of " + url.toExternalForm() + " failed, returning expired cache entry instead");
}
}
log.debug("returning file input stream for " + getLocalCacheFile().getPath());
FileInputStream fis = null;
try {
fis = new FileInputStream(getLocalCacheFile());
ObjectInputStream ois = new ObjectInputStream(fis);
SimpleDiskCacheEntryHeader header = (SimpleDiskCacheEntryHeader) ois.readObject();
if (!getUrl().toExternalForm().equals(header.getUrl())) {
throw new IOException("race detected while accessing cache file");
}
return fis;
} catch (Exception ex) {
if (fis != null) {
try {
fis.close();
} catch (IOException ex2) {
}
}
throw new IOException(ex);
}
}
public enum UpdateMode {
// CHECKSTYLE IGNORE MagicNumber FOR NEXT 1 LINE
NEVER(-1), ALWAYS(0), HOURLY(3600), DAILY(3600 * 24), WEEKLY(3600 * 24 * 7);
private final long expireMillis;
UpdateMode(int expireSeconds) {
// CHECKSTYLE IGNORE MagicNumber FOR NEXT 1 LINE
this.expireMillis = expireSeconds * 1000L;
}
public long getExpireMillis() {
return this.expireMillis;
}
public long getExpireSeconds() {
return this.expireMillis / 1000L;
}
}
}
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