1 package org.lcsim.util.cache;
2
3 import java.io.File;
4 import java.io.FileOutputStream;
5 import java.io.IOException;
6 import java.io.InputStream;
7 import java.io.OutputStream;
8 import java.io.PrintStream;
9 import java.net.URL;
10 import java.net.URLConnection;
11 import java.net.URLEncoder;
12
13 /**
14 * A utility for downloading and caching files
15 * @author tonyj
16 */
17 public class FileCache {
18 private static final File home = new File(getCacheRoot(), ".cache");
19 private static final ByteFormat format = new ByteFormat();
20 private File cache;
21 private PrintStream print = System.out;
22
23 public static File getCacheRoot() {
24 String cacheDir = System.getProperty("org.lcsim.cacheDir");
25 if (cacheDir == null)
26 cacheDir = System.getProperty("user.home");
27 return new File(cacheDir);
28 }
29
30 /**
31 * Create a FileCache using the default cache location
32 * @throws java.io.IOException If the cache directory cannot be created
33 */
34 public FileCache() throws IOException {
35 this(home);
36 }
37
38 /**
39 * Create a file cache using an explicit cache location
40 * @param cacheDirectory The directory to use for storing cached files
41 * @throws java.io.IOException If the cache directory cannot be created
42 */
43 public FileCache(File cacheDirectory) throws IOException {
44 setCacheDirectory(cacheDirectory);
45 }
46
47 /**
48 * Get a file from the cache. If the file is already in the cache and
49 * up-to-date the existing file will be returned. Otherwise the file will be
50 * downloaded first, and then moved to the cache.
51 * @param url The URL of the file to download
52 * @throws java.io.IOException If the file cannot be downloaded, or if an
53 * error occurs writing to the cache.
54 * @return The location of the cached file
55 */
56 public File getCachedFile(URL url) throws IOException {
57 return getCachedFile(url, null);
58 }
59
60 /**
61 * Get a file from the cache. If the file is already in the cache and
62 * up-to-date the existing file will be returned. Otherwise the file will be
63 * downloaded first, validated, and then moved to the cache.
64 * @param url Teh URL of the file to download
65 * @param validator A Validator that will be used to check the integrity of
66 * the downloaded file before it is placed in the cache
67 * @throws java.io.IOException If the file cannot be downloaded, or if an
68 * error occurs writing to the cache, or if the file fails
69 * validation.
70 * @return The location of the cached file
71 */
72 public File getCachedFile(URL url, Validator validator) throws IOException {
73 File cacheFile = new File(cache, URLEncoder.encode(url.toExternalForm(), "UTF-8"));
74 boolean downloadRequired = !cacheFile.exists();
75 if (cacheFile.exists() && !Boolean.getBoolean("org.lcsim.offline")) {
76 // If we can access the URL, check if the cachefile is up-to-date
77 try {
78 URLConnection connection = url.openConnection();
79 connection.setConnectTimeout(5000);
80 connection.setReadTimeout(5000);
81 long updated = connection.getLastModified();
82 long cached = cacheFile.lastModified();
83 if (updated > cached)
84 downloadRequired = true;
85 } catch (IOException x) {
86 // if (print != null)
87 // print.println("Warning: file cache could not access "+url+", "+x.getMessage());
88 }
89 }
90 if (downloadRequired) {
91 URLConnection connection = url.openConnection();
92 connection.setConnectTimeout(10000);
93 connection.setReadTimeout(10000);
94 long size = connection.getContentLength();
95 InputStream in = connection.getInputStream();
96 if (in != null) {
97 if (print != null)
98 print.println("Downloading..." + url);
99 File temp = File.createTempFile("det", null, cache);
100 temp.deleteOnExit();
101 OutputStream out = new FileOutputStream(temp);
102 byte[] buffer = new byte[8096];
103 try {
104 long got = 0;
105 for (;;) {
106 int l = in.read(buffer);
107 if (l < 0)
108 break;
109 out.write(buffer, 0, l);
110 if (out != null) {
111 got += l;
112 if (print != null) {
113 print.print("Got ");
114 print.print(format.format(got));
115 print.print('/');
116 print.print(format.format(size));
117 print.print('\r');
118 print.flush();
119 }
120 }
121 }
122 } finally {
123 in.close();
124 out.close();
125 }
126 if (validator != null)
127 validator.checkValidity(url, temp);
128 // File looks ok, move it into the cache
129 if (cacheFile.exists()) {
130 boolean ok = cacheFile.delete();
131 if (!ok)
132 throw new IOException("Error while deleting old cache file");
133 }
134 boolean ok = temp.renameTo(cacheFile);
135 if (!ok)
136 throw new IOException("Error while moving file to cache");
137 } else
138 throw new IOException("Could not open " + url);
139 }
140 return cacheFile;
141 }
142
143 /**
144 * Get the directory used for caching
145 * @return The cache directory
146 */
147 public File getCacheDirectory() {
148 return this.cache;
149 }
150
151 /**
152 * Set a new cache directory location
153 * @param cacheDirectory The directory to use.
154 * @throws java.io.IOException If the specified directory cannot be created,
155 * or already exists and is not a directory.
156 */
157 public void setCacheDirectory(File cacheDirectory) throws IOException {
158 if (!cacheDirectory.exists()) {
159 boolean ok = cacheDirectory.mkdirs();
160 if (!ok)
161 throw new IOException("Unable to create: " + cacheDirectory.getAbsoluteFile());
162 } else if (!cacheDirectory.isDirectory()) {
163 throw new IOException("Not a directory");
164 }
165 this.cache = cacheDirectory;
166 }
167
168 /**
169 * Gets the print stream used for diagnostic messages if a file is
170 * downloaded.
171 * @return The current diagnostic print stream, or <CODE>null</CODE> if none
172 * exists.
173 */
174 public PrintStream getPrintStream() {
175
176 return this.print;
177 }
178
179 /**
180 * Set the print stream to be used for diagnostic messages
181 * @param printStream The print stream to use, or <CODE>null</CODE> to
182 * disable diagnostic messages
183 */
184 public void setPrintStream(PrintStream printStream) {
185 this.print = printStream;
186 }
187
188 /**
189 * An interface to be implemented by cache validators
190 * @see #getCachedFile(URL,Validator)
191 */
192 public static interface Validator {
193 /**
194 * Called after a file has been downloaded but before it is placed in
195 * the cache, This method should throw an IOException if the file fails
196 * to validate.
197 * @param url The URL being downloaded
198 * @param file The file that needs to be validated
199 * @throws java.io.IOException If validation fails
200 */
201 void checkValidity(URL url, File file) throws IOException;
202 }
203 }