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‎caching/README.md

Lines changed: 66 additions & 57 deletions
Original file line numberDiff line numberDiff line change
@@ -43,39 +43,29 @@ Wikipedia says:
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**Programmatic Example**
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Let's first look at the data layer of our application. The interesting classes are `UserAccount`
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which is a simple Java object containing the user account details, and `DbManager` which handles
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reading and writing of these objects to/from MongoDB database.
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which is a simple Java object containing the user account details, and `DbManager` interface which handles
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reading and writing of these objects to/from database.
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```java
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@Setter
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@Getter
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@Data
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@AllArgsConstructor
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@ToString
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@EqualsAndHashCode
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public class UserAccount {
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private String userId;
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private String userName;
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private String additionalInfo;
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}
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@Slf4j
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public final class DbManager {
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private static MongoClient mongoClient;
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private static MongoDatabase db;
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private DbManager() { /*...*/ }
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public static void createVirtualDb() { /*...*/ }
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public static void connect() throws ParseException { /*...*/ }
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public static UserAccount readFromDb(String userId) { /*...*/ }
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public interface DbManager {
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public static void writeToDb(UserAccount userAccount) { /*...*/ }
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public static void updateDb(UserAccount userAccount) { /*...*/ }
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public static void upsertDb(UserAccount userAccount) { /*...*/ }
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void connect();
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void disconnect();
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UserAccount readFromDb(String userId);
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UserAccount writeToDb(UserAccount userAccount);
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UserAccount updateDb(UserAccount userAccount);
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UserAccount upsertDb(UserAccount userAccount);
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}
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```
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@@ -171,30 +161,43 @@ strategies.
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@Slf4j
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public class CacheStore {
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private static final int CAPACITY = 3;
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private static LruCache cache;
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private final DbManager dbManager;
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/* ... details omitted ... */
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public static UserAccount readThrough(String userId) {
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public UserAccount readThrough(final String userId) {
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if (cache.contains(userId)) {
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LOGGER.info("# Cache Hit!");
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LOGGER.info("# Found in Cache!");
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return cache.get(userId);
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}
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LOGGER.info("# Cache Miss!");
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UserAccount userAccount = DbManager.readFromDb(userId);
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LOGGER.info("# Not found in cache! Go to DB!!");
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UserAccount userAccount = dbManager.readFromDb(userId);
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cache.set(userId, userAccount);
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return userAccount;
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}
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public static void writeThrough(UserAccount userAccount) {
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public void writeThrough(final UserAccount userAccount) {
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if (cache.contains(userAccount.getUserId())) {
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DbManager.updateDb(userAccount);
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dbManager.updateDb(userAccount);
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} else {
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DbManager.writeToDb(userAccount);
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dbManager.writeToDb(userAccount);
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}
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cache.set(userAccount.getUserId(), userAccount);
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}
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public void writeAround(final UserAccount userAccount) {
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if (cache.contains(userAccount.getUserId())) {
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dbManager.updateDb(userAccount);
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// Cache data has been updated -- remove older
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cache.invalidate(userAccount.getUserId());
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// version from cache.
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} else {
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dbManager.writeToDb(userAccount);
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}
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}
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public static void clearCache() {
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if (cache != null) {
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cache.clear();
@@ -225,34 +228,39 @@ class.
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public final class AppManager {
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private static CachingPolicy cachingPolicy;
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private final DbManager dbManager;
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private final CacheStore cacheStore;
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private AppManager() {
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}
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public static void initDb(boolean useMongoDb) { /* ... */ }
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public void initDb() { /* ... */ }
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public static void initCachingPolicy(CachingPolicy policy) { /* ... */ }
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public static void initCacheCapacity(int capacity) { /* ... */ }
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public static UserAccount find(String userId) {
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if (cachingPolicy == CachingPolicy.THROUGH || cachingPolicy == CachingPolicy.AROUND) {
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return CacheStore.readThrough(userId);
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public UserAccount find(final String userId) {
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LOGGER.info("Trying to find {} in cache", userId);
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if (cachingPolicy == CachingPolicy.THROUGH
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|| cachingPolicy == CachingPolicy.AROUND) {
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return cacheStore.readThrough(userId);
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} else if (cachingPolicy == CachingPolicy.BEHIND) {
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return CacheStore.readThroughWithWriteBackPolicy(userId);
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return cacheStore.readThroughWithWriteBackPolicy(userId);
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} else if (cachingPolicy == CachingPolicy.ASIDE) {
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return findAside(userId);
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}
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return null;
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}
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public static void save(UserAccount userAccount) {
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public void save(final UserAccount userAccount) {
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LOGGER.info("Save record!");
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if (cachingPolicy == CachingPolicy.THROUGH) {
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CacheStore.writeThrough(userAccount);
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cacheStore.writeThrough(userAccount);
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} else if (cachingPolicy == CachingPolicy.AROUND) {
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CacheStore.writeAround(userAccount);
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cacheStore.writeAround(userAccount);
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} else if (cachingPolicy == CachingPolicy.BEHIND) {
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CacheStore.writeBehind(userAccount);
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cacheStore.writeBehind(userAccount);
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} else if (cachingPolicy == CachingPolicy.ASIDE) {
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saveAside(userAccount);
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}
@@ -272,24 +280,35 @@ Here is what we do in the main class of the application.
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@Slf4j
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public class App {
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public static void main(String[] args) {
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AppManager.initDb(false);
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AppManager.initCacheCapacity(3);
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var app = new App();
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public static void main(final String[] args) {
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boolean isDbMongo = isDbMongo(args);
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if(isDbMongo){
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LOGGER.info("Using the Mongo database engine to run the application.");
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} else {
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LOGGER.info("Using the 'in Memory' database to run the application.");
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}
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App app = new App(isDbMongo);
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app.useReadAndWriteThroughStrategy();
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String splitLine = "==============================================";
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LOGGER.info(splitLine);
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app.useReadThroughAndWriteAroundStrategy();
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LOGGER.info(splitLine);
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app.useReadThroughAndWriteBehindStrategy();
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LOGGER.info(splitLine);
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app.useCacheAsideStategy();
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LOGGER.info(splitLine);
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}
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public void useReadAndWriteThroughStrategy() {
286303
LOGGER.info("# CachingPolicy.THROUGH");
287-
AppManager.initCachingPolicy(CachingPolicy.THROUGH);
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appManager.initCachingPolicy(CachingPolicy.THROUGH);
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var userAccount1 = new UserAccount("001", "John", "He is a boy.");
289-
AppManager.save(userAccount1);
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LOGGER.info(AppManager.printCacheContent());
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AppManager.find("001");
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AppManager.find("001");
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appManager.save(userAccount1);
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LOGGER.info(appManager.printCacheContent());
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appManager.find("001");
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appManager.find("001");
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}
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public void useReadThroughAndWriteAroundStrategy() { /* ... */ }
@@ -300,16 +319,6 @@ public class App {
300319
}
301320
```
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Finally, here is some of the console output from the program.
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305-
```
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12:32:53.845 [main] INFO com.iluwatar.caching.App - # CachingPolicy.THROUGH
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12:32:53.900 [main] INFO com.iluwatar.caching.App -
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--CACHE CONTENT--
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UserAccount(userId=001, userName=John, additionalInfo=He is a boy.)
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----
311-
```
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## Class diagram
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![alt text](./etc/caching.png "Caching")

‎caching/docker-compose.yml

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Original file line numberDiff line numberDiff line change
@@ -0,0 +1,11 @@
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version: '3.7'
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services:
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mongodb_container:
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image: mongo:latest
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environment:
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MONGO_INITDB_ROOT_USERNAME: root
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MONGO_INITDB_ROOT_PASSWORD: rootpassword
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ports:
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- 27017:27017
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volumes:
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- ./mongo-data/:/data/db

‎caching/etc/caching.png

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‎caching/pom.xml

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Original file line numberDiff line numberDiff line change
@@ -39,19 +39,21 @@
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<scope>test</scope>
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</dependency>
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<dependency>
42-
<groupId>org.mongodb</groupId>
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<artifactId>mongodb-driver</artifactId>
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<version>3.12.1</version>
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<groupId>org.mockito</groupId>
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<artifactId>mockito-junit-jupiter</artifactId>
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<version>3.12.4</version>
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<scope>test</scope>
4546
</dependency>
4647
<dependency>
47-
<groupId>org.mongodb</groupId>
48-
<artifactId>mongodb-driver-core</artifactId>
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<version>3.0.4</version>
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<groupId>org.mockito</groupId>
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<artifactId>mockito-all</artifactId>
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<version>1.10.19</version>
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<scope>test</scope>
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</dependency>
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<dependency>
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<groupId>org.mongodb</groupId>
53-
<artifactId>bson</artifactId>
54-
<version>3.0.4</version>
55+
<artifactId>mongo-java-driver</artifactId>
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<version>3.4.1</version>
5557
</dependency>
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</dependencies>
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<!--

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