How to use

DiskBasedCache

in

com.android.volley.toolbox

 public static RequestQueue newRequestQueueForTest(final Context context, final OkHttpClient okHttpClient) {
  final File cacheDir = new File(context.getCacheDir(), "volley");

  final Network network = new BasicNetwork(new OkHttpStack(okHttpClient));

  final ResponseDelivery responseDelivery = new ExecutorDelivery(Executors.newSingleThreadExecutor());

  final RequestQueue queue =
      new RequestQueue(
          new DiskBasedCache(cacheDir),
          network,
          4,
          responseDelivery);

  queue.start();

  return queue;
}

/**
 * Reads the header off of an InputStream and returns a CacheHeader object.
 * @param is The InputStream to read from.
 * @throws java.io.IOException
 */
public static CacheHeader readHeader(InputStream is) throws IOException {
  CacheHeader entry = new CacheHeader();
  int magic = readInt(is);
  if (magic != CACHE_MAGIC) {
    // don't bother deleting, it'll get pruned eventually
    throw new IOException();
  }
  entry.key = readString(is);
  entry.etag = readString(is);
  if (entry.etag.equals("")) {
    entry.etag = null;
  }
  entry.serverDate = readLong(is);
  entry.lastModified = readLong(is);
  entry.ttl = readLong(is);
  entry.softTtl = readLong(is);
  entry.responseHeaders = readStringStringMap(is);
  return entry;
}

/**
 * Writes the contents of this CacheHeader to the specified OutputStream.
 */
public boolean writeHeader(OutputStream os) {
  try {
    writeInt(os, CACHE_MAGIC);
    writeString(os, key);
    writeString(os, etag == null ? "" : etag);
    writeLong(os, serverDate);
    writeLong(os, lastModified);
    writeLong(os, ttl);
    writeLong(os, softTtl);
    writeStringStringMap(responseHeaders, os);
    os.flush();
    return true;
  } catch (IOException e) {
    VolleyLog.d("%s", e.toString());
    return false;
  }
}

/**
 * Invalidates an entry in the cache.
 * @param key Cache key
 * @param fullExpire True to fully expire the entry, false to soft expire
 */
@Override
public synchronized void invalidate(String key, boolean fullExpire) {
  Entry entry = get(key);
  if (entry != null) {
    entry.softTtl = 0;
    if (fullExpire) {
      entry.ttl = 0;
    }
    put(key, entry);
  }
}

static String readString(InputStream is) throws IOException {
  int n = (int) readLong(is);
  byte[] b = streamToBytes(is, n);
  return new String(b, "UTF-8");
}

static void writeStringStringMap(Map<String, String> map, OutputStream os) throws IOException {
  if (map != null) {
    writeInt(os, map.size());
    for (Map.Entry<String, String> entry : map.entrySet()) {
      writeString(os, entry.getKey());
      writeString(os, entry.getValue());
    }
  } else {
    writeInt(os, 0);
  }
}

static Map<String, String> readStringStringMap(InputStream is) throws IOException {
  int size = readInt(is);
  Map<String, String> result = (size == 0)
      ? Collections.<String, String>emptyMap()
      : new HashMap<String, String>(size);
  for (int i = 0; i < size; i++) {
    String key = readString(is).intern();
    String value = readString(is).intern();
    result.put(key, value);
  }
  return result;
}

@Test public void serializeMap() throws Exception {
  ByteArrayOutputStream baos = new ByteArrayOutputStream();
  Map<String, String> empty = new HashMap<String, String>();
  DiskBasedCache.writeStringStringMap(empty, baos);
  DiskBasedCache.writeStringStringMap(null, baos);
  Map<String, String> twoThings = new HashMap<String, String>();
  twoThings.put("first", "thing");
  twoThings.put("second", "item");
  DiskBasedCache.writeStringStringMap(twoThings, baos);
  Map<String, String> emptyKey = new HashMap<String, String>();
  emptyKey.put("", "value");
  DiskBasedCache.writeStringStringMap(emptyKey, baos);
  Map<String, String> emptyValue = new HashMap<String, String>();
  emptyValue.put("key", "");
  DiskBasedCache.writeStringStringMap(emptyValue, baos);
  ByteArrayInputStream bais = new ByteArrayInputStream(baos.toByteArray());
  assertEquals(DiskBasedCache.readStringStringMap(bais), empty);
  assertEquals(DiskBasedCache.readStringStringMap(bais), empty); // null reads back empty
  assertEquals(DiskBasedCache.readStringStringMap(bais), twoThings);
  assertEquals(DiskBasedCache.readStringStringMap(bais), emptyKey);
  assertEquals(DiskBasedCache.readStringStringMap(bais), emptyValue);
}

@Test public void serializeString() throws Exception {
  ByteArrayOutputStream baos = new ByteArrayOutputStream();
  DiskBasedCache.writeString(baos, "");
  DiskBasedCache.writeString(baos, "This is a string.");
  DiskBasedCache.writeString(baos, "ファイカス");
  ByteArrayInputStream bais = new ByteArrayInputStream(baos.toByteArray());
  assertEquals(DiskBasedCache.readString(bais), "");
  assertEquals(DiskBasedCache.readString(bais), "This is a string.");
  assertEquals(DiskBasedCache.readString(bais), "ファイカス");
}

static void writeString(OutputStream os, String s) throws IOException {
  byte[] b = s.getBytes("UTF-8");
  writeLong(os, b.length);
  os.write(b, 0, b.length);
}

@Test public void serializeInt() throws Exception {
  ByteArrayOutputStream baos = new ByteArrayOutputStream();
  DiskBasedCache.writeInt(baos, 0);
  DiskBasedCache.writeInt(baos, 19791214);
  DiskBasedCache.writeInt(baos, -20050711);
  DiskBasedCache.writeInt(baos, Integer.MIN_VALUE);
  DiskBasedCache.writeInt(baos, Integer.MAX_VALUE);
  ByteArrayInputStream bais = new ByteArrayInputStream(baos.toByteArray());
  assertEquals(DiskBasedCache.readInt(bais), 0);
  assertEquals(DiskBasedCache.readInt(bais), 19791214);
  assertEquals(DiskBasedCache.readInt(bais), -20050711);
  assertEquals(DiskBasedCache.readInt(bais), Integer.MIN_VALUE);
  assertEquals(DiskBasedCache.readInt(bais), Integer.MAX_VALUE);
}

@Test public void serializeLong() throws Exception {
  ByteArrayOutputStream baos = new ByteArrayOutputStream();
  DiskBasedCache.writeLong(baos, 0);
  DiskBasedCache.writeLong(baos, 31337);
  DiskBasedCache.writeLong(baos, -4160);
  DiskBasedCache.writeLong(baos, 4295032832L);
  DiskBasedCache.writeLong(baos, -4314824046L);
  DiskBasedCache.writeLong(baos, Long.MIN_VALUE);
  DiskBasedCache.writeLong(baos, Long.MAX_VALUE);
  ByteArrayInputStream bais = new ByteArrayInputStream(baos.toByteArray());
  assertEquals(DiskBasedCache.readLong(bais), 0);
  assertEquals(DiskBasedCache.readLong(bais), 31337);
  assertEquals(DiskBasedCache.readLong(bais), -4160);
  assertEquals(DiskBasedCache.readLong(bais), 4295032832L);
  assertEquals(DiskBasedCache.readLong(bais), -4314824046L);
  assertEquals(DiskBasedCache.readLong(bais), Long.MIN_VALUE);
  assertEquals(DiskBasedCache.readLong(bais), Long.MAX_VALUE);
}

static Map<String, String> readStringStringMap(InputStream is) throws IOException {
  int size = readInt(is);
  Map<String, String> result = (size == 0)
      ? Collections.<String, String>emptyMap()
      : new HashMap<String, String>(size);
  for (int i = 0; i < size; i++) {
    String key = readString(is).intern();
    String value = readString(is).intern();
    result.put(key, value);
  }
  return result;
}

static void writeStringStringMap(Map<String, String> map, OutputStream os) throws IOException {
  if (map != null) {
    writeInt(os, map.size());
    for (Map.Entry<String, String> entry : map.entrySet()) {
      writeString(os, entry.getKey());
      writeString(os, entry.getValue());
    }
  } else {
    writeInt(os, 0);
  }
}

/**
 * Invalidates an entry in the cache.
 * @param key Cache key
 * @param fullExpire True to fully expire the entry, false to soft expire
 */
@Override
public synchronized void invalidate(String key, boolean fullExpire) {
  Entry entry = get(key);
  if (entry != null) {
    entry.softTtl = 0;
    if (fullExpire) {
      entry.ttl = 0;
    }
    put(key, entry);
  }
}

static String readString(InputStream is) throws IOException {
  int n = (int) readLong(is);
  byte[] b = streamToBytes(is, n);
  return new String(b, "UTF-8");
}

@Test public void serializeMap() throws Exception {
  ByteArrayOutputStream baos = new ByteArrayOutputStream();
  Map<String, String> empty = new HashMap<String, String>();
  DiskBasedCache.writeStringStringMap(empty, baos);
  DiskBasedCache.writeStringStringMap(null, baos);
  Map<String, String> twoThings = new HashMap<String, String>();
  twoThings.put("first", "thing");
  twoThings.put("second", "item");
  DiskBasedCache.writeStringStringMap(twoThings, baos);
  Map<String, String> emptyKey = new HashMap<String, String>();
  emptyKey.put("", "value");
  DiskBasedCache.writeStringStringMap(emptyKey, baos);
  Map<String, String> emptyValue = new HashMap<String, String>();
  emptyValue.put("key", "");
  DiskBasedCache.writeStringStringMap(emptyValue, baos);
  ByteArrayInputStream bais = new ByteArrayInputStream(baos.toByteArray());
  assertEquals(DiskBasedCache.readStringStringMap(bais), empty);
  assertEquals(DiskBasedCache.readStringStringMap(bais), empty); // null reads back empty
  assertEquals(DiskBasedCache.readStringStringMap(bais), twoThings);
  assertEquals(DiskBasedCache.readStringStringMap(bais), emptyKey);
  assertEquals(DiskBasedCache.readStringStringMap(bais), emptyValue);
}

@Test public void serializeString() throws Exception {
  ByteArrayOutputStream baos = new ByteArrayOutputStream();
  DiskBasedCache.writeString(baos, "");
  DiskBasedCache.writeString(baos, "This is a string.");
  DiskBasedCache.writeString(baos, "ファイカス");
  ByteArrayInputStream bais = new ByteArrayInputStream(baos.toByteArray());
  assertEquals(DiskBasedCache.readString(bais), "");
  assertEquals(DiskBasedCache.readString(bais), "This is a string.");
  assertEquals(DiskBasedCache.readString(bais), "ファイカス");
}

static void writeString(OutputStream os, String s) throws IOException {
  byte[] b = s.getBytes("UTF-8");
  writeLong(os, b.length);
  os.write(b, 0, b.length);
}

@Test public void serializeInt() throws Exception {
  ByteArrayOutputStream baos = new ByteArrayOutputStream();
  DiskBasedCache.writeInt(baos, 0);
  DiskBasedCache.writeInt(baos, 19791214);
  DiskBasedCache.writeInt(baos, -20050711);
  DiskBasedCache.writeInt(baos, Integer.MIN_VALUE);
  DiskBasedCache.writeInt(baos, Integer.MAX_VALUE);
  ByteArrayInputStream bais = new ByteArrayInputStream(baos.toByteArray());
  assertEquals(DiskBasedCache.readInt(bais), 0);
  assertEquals(DiskBasedCache.readInt(bais), 19791214);
  assertEquals(DiskBasedCache.readInt(bais), -20050711);
  assertEquals(DiskBasedCache.readInt(bais), Integer.MIN_VALUE);
  assertEquals(DiskBasedCache.readInt(bais), Integer.MAX_VALUE);
}