WARNING: Exception thrown by removal listener
com.google.common.util.concurrent.UncheckedExecutionException: java.lang.NullPointerException
        at com.google.common.cache.LocalCache$Segment.get(LocalCache.java:2207)
        at com.google.common.cache.LocalCache.get(LocalCache.java:3953)
        at com.google.common.cache.LocalCache$LocalManualCache.get(LocalCache.java:4790)
        at main.DB.writeUserDownloadLater(DB.java:116)
        at main.cache.Session.close(Session.java:137)
        at main.DownloadMeter.lambda$main$0(DownloadMeter.java:67)
        at com.google.common.cache.LocalCache.processPendingNotifications(LocalCache.java:1960)
        at com.google.common.cache.LocalCache$Segment.runUnlockedCleanup(LocalCache.java:3475)
        at com.google.common.cache.LocalCache$Segment.postWriteCleanup(LocalCache.java:3451)
        at com.google.common.cache.LocalCache$Segment.lockedGetOrLoad(LocalCache.java:2277)
        at com.google.common.cache.LocalCache$Segment.get(LocalCache.java:2201)
        at com.google.common.cache.LocalCache.get(LocalCache.java:3953)
        at com.google.common.cache.LocalCache$LocalManualCache.get(LocalCache.java:4790)
        at main.DownloadMeter.main(DownloadMeter.java:137)
Caused by: java.lang.NullPointerException
        at com.mysql.jdbc.ResultSetImpl.getStringInternal(ResultSetImpl.java:5268)
        at com.mysql.jdbc.ResultSetImpl.getString(ResultSetImpl.java:5151)
        at com.mysql.jdbc.ResultSetImpl.getString(ResultSetImpl.java:5190)
        at main.DB.lambda$writeUserDownloadLater$0(DB.java:127)
        at com.google.common.cache.LocalCache$LocalManualCache$1.load(LocalCache.java:4793)
        at com.google.common.cache.LocalCache$LoadingValueReference.loadFuture(LocalCache.java:3542)
        at com.google.common.cache.LocalCache$Segment.loadSync(LocalCache.java:2323)
        at com.google.common.cache.LocalCache$Segment.lockedGetOrLoad(LocalCache.java:2286)
        at com.google.common.cache.LocalCache$Segment.get(LocalCache.java:2201)
        ... 13 more

sessions = CacheBuilder
        .newBuilder()
        .initialCapacity(30000)
        .maximumSize(5000000)
        .expireAfterAccess(session_ttl, TimeUnit.SECONDS)
        .removalListener((RemovalListener<String, Session>) notification -> {
            Session session = notification.getValue();
            if (session != null) {
                logger.debug("Close session: " + notification.getKey());
                // ------------- > line 67
                session.close();
            }
        })
        .build();

...
...

//  ------------- > line 137
Session session = sessions.get(jsonMessage.get("id").getAsString(), () -> new Session(

));

public class DB {
    ...
    private static Cache<String, String> downloadsWithUserFileRelations = CacheBuilder
            .newBuilder()
            .maximumSize(1000000)
            .expireAfterAccess(15, TimeUnit.MINUTES)
            .build();
    ...
    ...
    public void writeUserDownloadLater(Session session) {
        try {
            // ------------ > line 116
            String user_file_id = downloadsWithUserFileRelations.get(session.getId(), () -> {
                downloadToUserFileStmt.setString(1, session.getId());
                ResultSet resultSet = downloadToUserFileStmt.executeQuery();
                if (!resultSet.next()) {
                    return null;
                }
                return resultSet.getString("user_file_id");
            });

            ...
            ...
        } catch (ExecutionException e) {
            DownloadMeter.logger.error("Execution exception", e);
        }
    }
}

testCompileClasspath - Compile classpath for source set 'test'.
+--- org.apache.activemq:activemq-all:5.11.+ -> 5.11.4
+--- mysql:mysql-connector-java:5.1.+ -> 5.1.40
+--- com.google.code.gson:gson:2.+ -> 2.8.0
+--- com.google.guava:guava:19.+ -> 19.0
+--- org.mongodb:mongo-java-driver:2.13.+ -> 2.13.3
+--- commons-cli:commons-cli:1.3.+ -> 1.3.1
+--- org.apache.logging.log4j:log4j-api:2.+ -> 2.7
+--- org.apache.logging.log4j:log4j-core:2.+ -> 2.7
|    \--- org.apache.logging.log4j:log4j-api:2.7
+--- org.apache.commons:commons-lang3:3.+ -> 3.5
\--- junit:junit:4.+ -> 4.12
     \--- org.hamcrest:hamcrest-core:1.3

    private static final BasicDataSource dataSource = new BasicDataSource();

    static {
        Properties properties = Properties.getInstance();
        dataSource.setDriverClassName("com.mysql.jdbc.Driver");
        dataSource.setUrl(properties.getProperty("db_uri"));
        dataSource.setUsername(properties.getProperty("db_user"));
        dataSource.setPassword(properties.getProperty("db_password"));
    }

    public void touchDownload(String id) {
        try (
                PreparedStatement updateDownloadStmt = dataSource.getConnection().prepareStatement(
                        "UPDATE fh_download SET date_end = CURRENT_TIMESTAMP WHERE unique_key = ?"
                );
        ) {
            updateDownloadStmt.setString(1, id);
            updateDownloadStmt.executeUpdate();
        } catch (SQLException e) {
            DownloadMeter.logger.error("SQL error", e);
        }
    }