This page provides code examples in Java for using the low-level Memcache API. Memcache is a high-performance, distributed memory object caching system that provides fast access to cached data. To learn more about memcache, read the Memcache Overview.
Synchronous usage
Low-level API example using the synchronous MemcacheService:
Java 7
@SuppressWarnings("serial")
public class MemcacheSyncCacheServlet extends HttpServlet {
@Override
public void doGet(HttpServletRequest req, HttpServletResponse resp) throws IOException,
ServletException {
String path = req.getRequestURI();
if (path.startsWith("/favicon.ico")) {
return; // ignore the request for favicon.ico
}
MemcacheService syncCache = MemcacheServiceFactory.getMemcacheService();
syncCache.setErrorHandler(ErrorHandlers.getConsistentLogAndContinue(Level.INFO));
String key = "count-sync";
byte[] value;
long count = 1;
value = (byte[]) syncCache.get(key);
if (value == null) {
value = BigInteger.valueOf(count).toByteArray();
syncCache.put(key, value);
} else {
// Increment value
count = new BigInteger(value).longValue();
count++;
value = BigInteger.valueOf(count).toByteArray();
// Put back in cache
syncCache.put(key, value);
}
// Output content
resp.setContentType("text/plain");
resp.getWriter().print("Value is " + count + "\n");
}
}Java 8
@SuppressWarnings("serial")
// With @WebServlet annotation the webapp/WEB-INF/web.xml is no longer required.
@WebServlet(name = "MemcacheSync", description = "Memcache: Synchronous",
urlPatterns = "/memcache/sync")
public class MemcacheSyncCacheServlet extends HttpServlet {
@Override
public void doGet(HttpServletRequest req, HttpServletResponse resp) throws IOException,
ServletException {
String path = req.getRequestURI();
if (path.startsWith("/favicon.ico")) {
return; // ignore the request for favicon.ico
}
MemcacheService syncCache = MemcacheServiceFactory.getMemcacheService();
syncCache.setErrorHandler(ErrorHandlers.getConsistentLogAndContinue(Level.INFO));
String key = "count-sync";
byte[] value;
long count = 1;
value = (byte[]) syncCache.get(key);
if (value == null) {
value = BigInteger.valueOf(count).toByteArray();
syncCache.put(key, value);
} else {
// Increment value
count = new BigInteger(value).longValue();
count++;
value = BigInteger.valueOf(count).toByteArray();
// Put back in cache
syncCache.put(key, value);
}
// Output content
resp.setContentType("text/plain");
resp.getWriter().print("Value is " + count + "\n");
}
}Asynchronous usage
Low-level API example using AsyncMemcacheService:
AsyncMemcacheService asyncCache = MemcacheServiceFactory.getAsyncMemcacheService();
asyncCache.setErrorHandler(ErrorHandlers.getConsistentLogAndContinue(Level.INFO));
String key = "count-async";
byte[] value;
long count = 1;
Future<Object> futureValue = asyncCache.get(key); // Read from cache.
// ... Do other work in parallel to cache retrieval.
try {
value = (byte[]) futureValue.get();
if (value == null) {
value = BigInteger.valueOf(count).toByteArray();
asyncCache.put(key, value);
} else {
// Increment value
count = new BigInteger(value).longValue();
count++;
value = BigInteger.valueOf(count).toByteArray();
// Put back in cache
asyncCache.put(key, value);
}
} catch (InterruptedException | ExecutionException e) {
throw new ServletException("Error when waiting for future value", e);
}For more information on the low-level API, see the Memcache Javadoc.
