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Shun Fanlesv
Shun Fan
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lesv
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Update memcache sample with code from docs pages (GoogleCloudPlatform#176)
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‎appengine/memcache/src/main/java/com/example/appengine/memcache/MemcacheAsyncCacheServlet.java

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/**
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* Copyright 2016 Google Inc. All Rights Reserved.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package com.example.appengine.memcache;
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import com.google.appengine.api.memcache.AsyncMemcacheService;
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import com.google.appengine.api.memcache.ErrorHandlers;
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import com.google.appengine.api.memcache.MemcacheServiceFactory;
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import java.io.IOException;
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import java.math.BigInteger;
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import java.util.concurrent.ExecutionException;
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import java.util.concurrent.Future;
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import java.util.logging.Level;
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import javax.servlet.ServletException;
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import javax.servlet.http.HttpServlet;
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import javax.servlet.http.HttpServletRequest;
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import javax.servlet.http.HttpServletResponse;
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@SuppressWarnings("serial")
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public class MemcacheAsyncCacheServlet extends HttpServlet {
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@Override
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public void doGet(HttpServletRequest req, HttpServletResponse resp) throws IOException,
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ServletException {
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String path = req.getRequestURI();
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if (path.startsWith("/favicon.ico")) {
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return; // ignore the request for favicon.ico
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}
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// [START example]
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AsyncMemcacheService asyncCache = MemcacheServiceFactory.getAsyncMemcacheService();
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asyncCache.setErrorHandler(ErrorHandlers.getConsistentLogAndContinue(Level.INFO));
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String key = "count-async";
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byte[] value;
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long count = 1;
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Future<Object> futureValue = asyncCache.get(key); // Read from cache.
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// ... Do other work in parallel to cache retrieval.
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try {
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value = (byte[]) futureValue.get();
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if (value == null) {
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value = BigInteger.valueOf(count).toByteArray();
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asyncCache.put(key, value);
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} else {
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// Increment value
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count = new BigInteger(value).longValue();
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count++;
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value = BigInteger.valueOf(count).toByteArray();
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// Put back in cache
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asyncCache.put(key, value);
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}
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} catch (InterruptedException | ExecutionException e) {
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throw new ServletException("Error when waiting for future value", e);
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}
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// [END example]
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// Output content
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resp.setContentType("text/plain");
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resp.getWriter().print("Value is " + count + "\n");
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}
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}

‎appengine/memcache/src/main/java/com/example/appengine/memcache/MemcacheServlet.java renamed to ‎appengine/memcache/src/main/java/com/example/appengine/memcache/MemcacheBestPracticeServlet.java

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// [START example]
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@SuppressWarnings("serial")
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public class MemcacheServlet extends HttpServlet {
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public class MemcacheBestPracticeServlet extends HttpServlet {
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@Override
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public void doGet(HttpServletRequest req, HttpServletResponse resp) throws IOException,

‎appengine/memcache/src/main/java/com/example/appengine/memcache/MemcacheConcurrentServlet.java

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/**
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* Copyright 2016 Google Inc. All Rights Reserved.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package com.example.appengine.memcache;
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import com.google.appengine.api.memcache.MemcacheService;
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import com.google.appengine.api.memcache.MemcacheService.IdentifiableValue;
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import com.google.appengine.api.memcache.MemcacheServiceFactory;
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import java.io.IOException;
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import java.math.BigInteger;
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import javax.servlet.ServletException;
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import javax.servlet.http.HttpServlet;
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import javax.servlet.http.HttpServletRequest;
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import javax.servlet.http.HttpServletResponse;
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// [START example]
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@SuppressWarnings("serial")
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public class MemcacheConcurrentServlet extends HttpServlet {
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@Override
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public void doGet(HttpServletRequest req, HttpServletResponse resp) throws IOException,
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ServletException {
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String path = req.getRequestURI();
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if (path.startsWith("/favicon.ico")) {
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return; // ignore the request for favicon.ico
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}
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String key = "count-concurrent";
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// Using the synchronous cache.
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MemcacheService syncCache = MemcacheServiceFactory.getMemcacheService();
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// Write this value to cache using getIdentifiable and putIfUntouched.
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for (long delayMs = 1; delayMs < 1000; delayMs *= 2) {
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IdentifiableValue oldValue = syncCache.getIdentifiable(key);
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byte[] newValue = oldValue == null
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? BigInteger.valueOf(0).toByteArray()
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: increment((byte[]) oldValue.getValue()); // newValue depends on old value
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resp.setContentType("text/plain");
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resp.getWriter().print("Value is " + new BigInteger(newValue).intValue() + "\n");
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if (oldValue == null) {
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// Key doesn't exist. We can safely put it in cache.
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syncCache.put(key, newValue);
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break;
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} else if (syncCache.putIfUntouched(key, oldValue, newValue)) {
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// newValue has been successfully put into cache.
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break;
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} else {
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// Some other client changed the value since oldValue was retrieved.
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// Wait a while before trying again, waiting longer on successive loops.
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try {
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Thread.sleep(delayMs);
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} catch (InterruptedException e) {
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throw new ServletException("Error when sleeping", e);
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}
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}
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}
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}
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/**
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* Increments an integer stored as a byte array by one.
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* @param oldValue a byte array with the old value
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* @return a byte array as the old value increased by one
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*/
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private byte[] increment(byte[] oldValue) {
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long val = new BigInteger(oldValue).intValue();
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val++;
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return BigInteger.valueOf(val).toByteArray();
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}
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}
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// [END example]

‎appengine/memcache/src/main/java/com/example/appengine/memcache/MemcacheSyncCacheServlet.java

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/**
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* Copyright 2016 Google Inc. All Rights Reserved.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package com.example.appengine.memcache;
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import com.google.appengine.api.memcache.ErrorHandlers;
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import com.google.appengine.api.memcache.MemcacheService;
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import com.google.appengine.api.memcache.MemcacheServiceFactory;
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import java.io.IOException;
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import java.math.BigInteger;
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import java.util.logging.Level;
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import javax.servlet.ServletException;
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import javax.servlet.http.HttpServlet;
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import javax.servlet.http.HttpServletRequest;
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import javax.servlet.http.HttpServletResponse;
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// [START example]
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@SuppressWarnings("serial")
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public class MemcacheSyncCacheServlet extends HttpServlet {
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@Override
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public void doGet(HttpServletRequest req, HttpServletResponse resp) throws IOException,
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ServletException {
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String path = req.getRequestURI();
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if (path.startsWith("/favicon.ico")) {
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return; // ignore the request for favicon.ico
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}
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MemcacheService syncCache = MemcacheServiceFactory.getMemcacheService();
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syncCache.setErrorHandler(ErrorHandlers.getConsistentLogAndContinue(Level.INFO));
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String key = "count-sync";
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byte[] value;
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long count = 1;
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value = (byte[]) syncCache.get(key);
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if (value == null) {
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value = BigInteger.valueOf(count).toByteArray();
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syncCache.put(key, value);
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} else {
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// Increment value
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count = new BigInteger(value).longValue();
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count++;
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value = BigInteger.valueOf(count).toByteArray();
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// Put back in cache
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syncCache.put(key, value);
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}
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// Output content
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resp.setContentType("text/plain");
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resp.getWriter().print("Value is " + count + "\n");
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}
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}
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// [END example]

‎appengine/memcache/src/main/webapp/WEB-INF/appengine-web.xml

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<?xml version="1.0" encoding="utf-8"?>
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<!-- [START_EXCLUDE] -->
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<!--
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Copyright 2015 Google Inc. All Rights Reserved.
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Copyright 2016 Google Inc. All Rights Reserved.
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Licensed under the Apache License, Version 2.0 (the "License");
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you may not use this file except in compliance with the License.
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You may obtain a copy of the License at

‎appengine/memcache/src/main/webapp/WEB-INF/web.xml

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<?xml version="1.0" encoding="utf-8"?>
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<!-- [START_EXCLUDE] -->
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<!--
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Copyright 2015 Google Inc. All Rights Reserved.
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Copyright 2016 Google Inc. All Rights Reserved.
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Licensed under the Apache License, Version 2.0 (the "License");
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you may not use this file except in compliance with the License.
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You may obtain a copy of the License at
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xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd"
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version="2.5">
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<servlet>
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<servlet-name>memcache</servlet-name>
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<servlet-class>com.example.appengine.memcache.MemcacheServlet</servlet-class>
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<servlet-name>memcache-best-practice</servlet-name>
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<servlet-class>com.example.appengine.memcache.MemcacheBestPracticeServlet</servlet-class>
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</servlet>
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<servlet-mapping>
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<servlet-name>memcache</servlet-name>
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<servlet-name>memcache-best-practice</servlet-name>
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<url-pattern>/</url-pattern>
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</servlet-mapping>
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<servlet>
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<servlet-name>memcache-async</servlet-name>
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<servlet-class>com.example.appengine.memcache.MemcacheAsyncCacheServlet</servlet-class>
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</servlet>
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<servlet-mapping>
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<servlet-name>memcache-async</servlet-name>
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<url-pattern>/async</url-pattern>
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</servlet-mapping>
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<servlet>
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<servlet-name>memcache-sync</servlet-name>
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<servlet-class>com.example.appengine.memcache.MemcacheSyncCacheServlet</servlet-class>
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</servlet>
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<servlet-mapping>
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<servlet-name>memcache-sync</servlet-name>
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<url-pattern>/sync</url-pattern>
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</servlet-mapping>
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<servlet>
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<servlet-name>memcache-concurrent</servlet-name>
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<servlet-class>com.example.appengine.memcache.MemcacheConcurrentServlet</servlet-class>
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</servlet>
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<servlet-mapping>
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<servlet-name>memcache-concurrent</servlet-name>
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<url-pattern>/concurrent</url-pattern>
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</servlet-mapping>
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</web-app>
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