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HttpResponseCache.java
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HttpResponseCache.java
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/*
* Copyright (C) 2010 The Android Open Source Project
*
* 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.squareup.okhttp;
import com.squareup.okhttp.internal.DiskLruCache;
import com.squareup.okhttp.internal.Util;
import com.squareup.okhttp.internal.http.HttpMethod;
import java.io.BufferedWriter;
import java.io.ByteArrayInputStream;
import java.io.File;
import java.io.FilterInputStream;
import java.io.FilterOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.io.OutputStreamWriter;
import java.io.Writer;
import java.net.CacheRequest;
import java.net.CacheResponse;
import java.net.ResponseCache;
import java.net.URI;
import java.net.URLConnection;
import java.security.cert.Certificate;
import java.security.cert.CertificateEncodingException;
import java.security.cert.CertificateException;
import java.security.cert.CertificateFactory;
import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import java.util.Map;
import okio.BufferedSource;
import okio.ByteString;
import okio.Okio;
import static com.squareup.okhttp.internal.Util.UTF_8;
/**
* Caches HTTP and HTTPS responses to the filesystem so they may be reused,
* saving time and bandwidth.
*
* <h3>Cache Optimization</h3>
* To measure cache effectiveness, this class tracks three statistics:
* <ul>
* <li><strong>{@link #getRequestCount() Request Count:}</strong> the number
* of HTTP requests issued since this cache was created.
* <li><strong>{@link #getNetworkCount() Network Count:}</strong> the
* number of those requests that required network use.
* <li><strong>{@link #getHitCount() Hit Count:}</strong> the number of
* those requests whose responses were served by the cache.
* </ul>
* Sometimes a request will result in a conditional cache hit. If the cache
* contains a stale copy of the response, the client will issue a conditional
* {@code GET}. The server will then send either the updated response if it has
* changed, or a short 'not modified' response if the client's copy is still
* valid. Such responses increment both the network count and hit count.
*
* <p>The best way to improve the cache hit rate is by configuring the web
* server to return cacheable responses. Although this client honors all <a
* href="http://www.ietf.org/rfc/rfc2616.txt">HTTP/1.1 (RFC 2068)</a> cache
* headers, it doesn't cache partial responses.
*
* <h3>Force a Network Response</h3>
* In some situations, such as after a user clicks a 'refresh' button, it may be
* necessary to skip the cache, and fetch data directly from the server. To force
* a full refresh, add the {@code no-cache} directive: <pre> {@code
* connection.addRequestProperty("Cache-Control", "no-cache");
* }</pre>
* If it is only necessary to force a cached response to be validated by the
* server, use the more efficient {@code max-age=0} instead: <pre> {@code
* connection.addRequestProperty("Cache-Control", "max-age=0");
* }</pre>
*
* <h3>Force a Cache Response</h3>
* Sometimes you'll want to show resources if they are available immediately,
* but not otherwise. This can be used so your application can show
* <i>something</i> while waiting for the latest data to be downloaded. To
* restrict a request to locally-cached resources, add the {@code
* only-if-cached} directive: <pre> {@code
* try {
* connection.addRequestProperty("Cache-Control", "only-if-cached");
* InputStream cached = connection.getInputStream();
* // the resource was cached! show it
* } catch (FileNotFoundException e) {
* // the resource was not cached
* }
* }</pre>
* This technique works even better in situations where a stale response is
* better than no response. To permit stale cached responses, use the {@code
* max-stale} directive with the maximum staleness in seconds: <pre> {@code
* int maxStale = 60 * 60 * 24 * 28; // tolerate 4-weeks stale
* connection.addRequestProperty("Cache-Control", "max-stale=" + maxStale);
* }</pre>
*/
public final class HttpResponseCache extends ResponseCache implements OkResponseCache {
// TODO: add APIs to iterate the cache?
private static final int VERSION = 201105;
private static final int ENTRY_METADATA = 0;
private static final int ENTRY_BODY = 1;
private static final int ENTRY_COUNT = 2;
private final DiskLruCache cache;
/* read and write statistics, all guarded by 'this' */
private int writeSuccessCount;
private int writeAbortCount;
private int networkCount;
private int hitCount;
private int requestCount;
public HttpResponseCache(File directory, long maxSize) throws IOException {
cache = DiskLruCache.open(directory, VERSION, ENTRY_COUNT, maxSize);
}
@Override public CacheResponse get(URI uri, String s, Map<String, List<String>> stringListMap)
throws IOException {
throw new UnsupportedOperationException("This is not a general purpose response cache.");
}
@Override public CacheRequest put(URI uri, URLConnection urlConnection) throws IOException {
throw new UnsupportedOperationException("This is not a general purpose response cache.");
}
private static String urlToKey(Request requst) {
return Util.hash(requst.urlString());
}
@Override public Response get(Request request) {
String key = urlToKey(request);
DiskLruCache.Snapshot snapshot;
Entry entry;
try {
snapshot = cache.get(key);
if (snapshot == null) {
return null;
}
entry = new Entry(snapshot.getInputStream(ENTRY_METADATA));
} catch (IOException e) {
// Give up because the cache cannot be read.
return null;
}
Response response = entry.response(request, snapshot);
if (!entry.matches(request, response)) {
Util.closeQuietly(response.body());
return null;
}
return response;
}
@Override public CacheRequest put(Response response) throws IOException {
String requestMethod = response.request().method();
if (maybeRemove(response.request())) {
return null;
}
if (!requestMethod.equals("GET")) {
// Don't cache non-GET responses. We're technically allowed to cache
// HEAD requests and some POST requests, but the complexity of doing
// so is high and the benefit is low.
return null;
}
if (response.hasVaryAll()) {
return null;
}
Entry entry = new Entry(response);
DiskLruCache.Editor editor = null;
try {
editor = cache.edit(urlToKey(response.request()));
if (editor == null) {
return null;
}
entry.writeTo(editor);
return new CacheRequestImpl(editor);
} catch (IOException e) {
abortQuietly(editor);
return null;
}
}
@Override public boolean maybeRemove(Request request) {
if (HttpMethod.invalidatesCache(request.method())) {
try {
cache.remove(urlToKey(request));
} catch (IOException ignored) {
// The cache cannot be written.
}
return true;
}
return false;
}
@Override public void update(Response cached, Response network) {
Entry entry = new Entry(network);
DiskLruCache.Snapshot snapshot = ((CacheResponseBody) cached.body()).snapshot;
DiskLruCache.Editor editor = null;
try {
editor = snapshot.edit(); // Returns null if snapshot is not current.
if (editor != null) {
entry.writeTo(editor);
editor.commit();
}
} catch (IOException e) {
abortQuietly(editor);
}
}
private void abortQuietly(DiskLruCache.Editor editor) {
// Give up because the cache cannot be written.
try {
if (editor != null) {
editor.abort();
}
} catch (IOException ignored) {
}
}
/**
* Closes the cache and deletes all of its stored values. This will delete
* all files in the cache directory including files that weren't created by
* the cache.
*/
public void delete() throws IOException {
cache.delete();
}
public synchronized int getWriteAbortCount() {
return writeAbortCount;
}
public synchronized int getWriteSuccessCount() {
return writeSuccessCount;
}
public long getSize() {
return cache.size();
}
public long getMaxSize() {
return cache.getMaxSize();
}
public void flush() throws IOException {
cache.flush();
}
public void close() throws IOException {
cache.close();
}
public File getDirectory() {
return cache.getDirectory();
}
public boolean isClosed() {
return cache.isClosed();
}
@Override public synchronized void trackResponse(ResponseSource source) {
requestCount++;
switch (source) {
case CACHE:
hitCount++;
break;
case CONDITIONAL_CACHE:
case NETWORK:
networkCount++;
break;
}
}
@Override public synchronized void trackConditionalCacheHit() {
hitCount++;
}
public synchronized int getNetworkCount() {
return networkCount;
}
public synchronized int getHitCount() {
return hitCount;
}
public synchronized int getRequestCount() {
return requestCount;
}
private final class CacheRequestImpl extends CacheRequest {
private final DiskLruCache.Editor editor;
private OutputStream cacheOut;
private boolean done;
private OutputStream body;
public CacheRequestImpl(final DiskLruCache.Editor editor) throws IOException {
this.editor = editor;
this.cacheOut = editor.newOutputStream(ENTRY_BODY);
this.body = new FilterOutputStream(cacheOut) {
@Override public void close() throws IOException {
synchronized (HttpResponseCache.this) {
if (done) {
return;
}
done = true;
writeSuccessCount++;
}
super.close();
editor.commit();
}
@Override public void write(byte[] buffer, int offset, int length) throws IOException {
// Since we don't override "write(int oneByte)", we can write directly to "out"
// and avoid the inefficient implementation from the FilterOutputStream.
out.write(buffer, offset, length);
}
};
}
@Override public void abort() {
synchronized (HttpResponseCache.this) {
if (done) {
return;
}
done = true;
writeAbortCount++;
}
Util.closeQuietly(cacheOut);
try {
editor.abort();
} catch (IOException ignored) {
}
}
@Override public OutputStream getBody() throws IOException {
return body;
}
}
private static final class Entry {
private final String url;
private final Headers varyHeaders;
private final String requestMethod;
private final String statusLine;
private final Headers responseHeaders;
private final Handshake handshake;
/**
* Reads an entry from an input stream. A typical entry looks like this:
* <pre>{@code
* http://google.com/foo
* GET
* 2
* Accept-Language: fr-CA
* Accept-Charset: UTF-8
* HTTP/1.1 200 OK
* 3
* Content-Type: image/png
* Content-Length: 100
* Cache-Control: max-age=600
* }</pre>
*
* <p>A typical HTTPS file looks like this:
* <pre>{@code
* https://google.com/foo
* GET
* 2
* Accept-Language: fr-CA
* Accept-Charset: UTF-8
* HTTP/1.1 200 OK
* 3
* Content-Type: image/png
* Content-Length: 100
* Cache-Control: max-age=600
*
* AES_256_WITH_MD5
* 2
* base64-encoded peerCertificate[0]
* base64-encoded peerCertificate[1]
* -1
* }</pre>
* The file is newline separated. The first two lines are the URL and
* the request method. Next is the number of HTTP Vary request header
* lines, followed by those lines.
*
* <p>Next is the response status line, followed by the number of HTTP
* response header lines, followed by those lines.
*
* <p>HTTPS responses also contain SSL session information. This begins
* with a blank line, and then a line containing the cipher suite. Next
* is the length of the peer certificate chain. These certificates are
* base64-encoded and appear each on their own line. The next line
* contains the length of the local certificate chain. These
* certificates are also base64-encoded and appear each on their own
* line. A length of -1 is used to encode a null array.
*/
public Entry(InputStream in) throws IOException {
try {
BufferedSource source = Okio.buffer(Okio.source(in));
url = source.readUtf8LineStrict();
requestMethod = source.readUtf8LineStrict();
Headers.Builder varyHeadersBuilder = new Headers.Builder();
int varyRequestHeaderLineCount = readInt(source);
for (int i = 0; i < varyRequestHeaderLineCount; i++) {
varyHeadersBuilder.addLine(source.readUtf8LineStrict());
}
varyHeaders = varyHeadersBuilder.build();
statusLine = source.readUtf8LineStrict();
Headers.Builder responseHeadersBuilder = new Headers.Builder();
int responseHeaderLineCount = readInt(source);
for (int i = 0; i < responseHeaderLineCount; i++) {
responseHeadersBuilder.addLine(source.readUtf8LineStrict());
}
responseHeaders = responseHeadersBuilder.build();
if (isHttps()) {
String blank = source.readUtf8LineStrict();
if (blank.length() > 0) {
throw new IOException("expected \"\" but was \"" + blank + "\"");
}
String cipherSuite = source.readUtf8LineStrict();
List<Certificate> peerCertificates = readCertificateList(source);
List<Certificate> localCertificates = readCertificateList(source);
handshake = Handshake.get(cipherSuite, peerCertificates, localCertificates);
} else {
handshake = null;
}
} finally {
in.close();
}
}
public Entry(Response response) {
this.url = response.request().urlString();
this.varyHeaders = response.request().headers().getAll(response.getVaryFields());
this.requestMethod = response.request().method();
this.statusLine = response.statusLine();
this.responseHeaders = response.headers();
this.handshake = response.handshake();
}
public void writeTo(DiskLruCache.Editor editor) throws IOException {
OutputStream out = editor.newOutputStream(ENTRY_METADATA);
Writer writer = new BufferedWriter(new OutputStreamWriter(out, UTF_8));
writer.write(url + '\n');
writer.write(requestMethod + '\n');
writer.write(Integer.toString(varyHeaders.size()) + '\n');
for (int i = 0; i < varyHeaders.size(); i++) {
writer.write(varyHeaders.name(i) + ": " + varyHeaders.value(i) + '\n');
}
writer.write(statusLine + '\n');
writer.write(Integer.toString(responseHeaders.size()) + '\n');
for (int i = 0; i < responseHeaders.size(); i++) {
writer.write(responseHeaders.name(i) + ": " + responseHeaders.value(i) + '\n');
}
if (isHttps()) {
writer.write('\n');
writer.write(handshake.cipherSuite() + '\n');
writeCertArray(writer, handshake.peerCertificates());
writeCertArray(writer, handshake.localCertificates());
}
writer.close();
}
private boolean isHttps() {
return url.startsWith("https://");
}
private List<Certificate> readCertificateList(BufferedSource source) throws IOException {
int length = readInt(source);
if (length == -1) return Collections.emptyList(); // OkHttp v1.2 used -1 to indicate null.
try {
CertificateFactory certificateFactory = CertificateFactory.getInstance("X.509");
List<Certificate> result = new ArrayList<Certificate>(length);
for (int i = 0; i < length; i++) {
String line = source.readUtf8LineStrict();
byte[] bytes = ByteString.decodeBase64(line).toByteArray();
result.add(certificateFactory.generateCertificate(new ByteArrayInputStream(bytes)));
}
return result;
} catch (CertificateException e) {
throw new IOException(e.getMessage());
}
}
private void writeCertArray(Writer writer, List<Certificate> certificates) throws IOException {
try {
writer.write(Integer.toString(certificates.size()) + '\n');
for (int i = 0, size = certificates.size(); i < size; i++) {
byte[] bytes = certificates.get(i).getEncoded();
String line = ByteString.of(bytes).base64();
writer.write(line + '\n');
}
} catch (CertificateEncodingException e) {
throw new IOException(e.getMessage());
}
}
public boolean matches(Request request, Response response) {
return url.equals(request.urlString())
&& requestMethod.equals(request.method())
&& response.varyMatches(varyHeaders, request);
}
public Response response(Request request, DiskLruCache.Snapshot snapshot) {
String contentType = responseHeaders.get("Content-Type");
String contentLength = responseHeaders.get("Content-Length");
return new Response.Builder()
.request(request)
.statusLine(statusLine)
.headers(responseHeaders)
.body(new CacheResponseBody(snapshot, contentType, contentLength))
.handshake(handshake)
.build();
}
}
private static int readInt(BufferedSource source) throws IOException {
String line = source.readUtf8LineStrict();
try {
return Integer.parseInt(line);
} catch (NumberFormatException e) {
throw new IOException("Expected an integer but was \"" + line + "\"");
}
}
private static class CacheResponseBody extends Response.Body {
private final DiskLruCache.Snapshot snapshot;
private final InputStream bodyIn;
private final String contentType;
private final String contentLength;
public CacheResponseBody(final DiskLruCache.Snapshot snapshot,
String contentType, String contentLength) {
this.snapshot = snapshot;
this.contentType = contentType;
this.contentLength = contentLength;
// This input stream closes the snapshot when the stream is closed.
this.bodyIn = new FilterInputStream(snapshot.getInputStream(ENTRY_BODY)) {
@Override public void close() throws IOException {
snapshot.close();
super.close();
}
};
}
@Override public boolean ready() throws IOException {
return true;
}
@Override public MediaType contentType() {
return contentType != null ? MediaType.parse(contentType) : null;
}
@Override public long contentLength() {
try {
return contentLength != null ? Long.parseLong(contentLength) : -1;
} catch (NumberFormatException e) {
return -1;
}
}
@Override public InputStream byteStream() {
return bodyIn;
}
}
}