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這是情景。我必須在定時間隔內輪詢一個ftp服務器並獲取csv文件。然後，這些CSV文件必須被解析並作爲輸入發送給某些業務邏輯。我已經這樣做了。生產者消費者模型如情景不起作用
FTPClientPolling（監製）
public class FTPClientPolling {
private static FTPClientPolling instance = null;
private FTPClientPolling() {
}
public synchronized static FTPClientPolling getInstance() {
if (instance == null) {
logger.info("Object created for Client Polling");
instance = new FTPClientPolling();
initializeFTPClient();
}
return instance;
}
public static void initializeFTPClient() {
// initialize the values from properties file
}
public void startPolling() {
FTPClient ftpClient = null;
try {
//connecting to ftp server
//iterating the files in it
FTPFile[] filesList = ftpClient.listFiles();
for (FTPFile tmpFile : filesList) {
//..
File tempFile = File.createTempFile(tmpFile.getName(), null);
FileOutputStream fileOut = new FileOutputStream(tempFile);
ftpClient.retrieveFile(tmpFile.getName(), fileOut);
//adding the file to the Queue of the file processor
FileProcessor.getInstance().getFilesToBeProcessedQueue().add(tempFile);
}
if (ftpClient.isConnected())
ftpClient.disconnect();
} catch (Exception e) {
//logging
} finally {
//closing ftpclient
}
}
}
FTPClientPollingTasker（監製塔斯克）
public class FTPClientTasker extends TimerTask {
private static Long timeInterval = 10000l;
@Override
public void run() {
FTPClientPolling.getInstance().startPolling();
}
public static void start() {
TimerTask timerTask = new FTPClientTasker();
Timer timer = new Timer();
timer.scheduleAtFixedRate(timerTask, timeInterval, timeInterval);
}
public static void main(String[] args) {
start();
}
}
FileProcessor（消費者）
public final class FileProcessor {
private static FileProcessor instance = null;
private Queue<File> filesToBeProcessedQueue = new ArrayBlockingQueue<File>(10);
private FileProcessor() {
}
public synchronized static FileProcessor getInstance() {
if (instance == null) {
instance = new FileProcessor();
}
return instance;
}
public void run() {
while (!filesToBeProcessedQueue.isEmpty()) {
processSyncFiles(filesToBeProcessedQueue.poll());
}
}
private void processSyncFiles(File inputFile) {
try {
HashMap<String, Boolean> outputConsolidation = new HashMap<String, Boolean>();
FileReader fileReader = new FileReader(inputFile);
List<InputBean> csvContentsList = CSVParser.readContentsFromCSV(fileReader, new InputBean());
for (InputBean inputBean : csvContentsList) {
boolean output = false;
// some business logic
outputConsolidation.put(inputBean.toString(), output);
}
} catch (Exception e) {
//logging
}
}
public synchronized Queue<File> getFilesToBeProcessedQueue() {
return filesToBeProcessedQueue;
}
}
FileProcessor Tasker（Consumer Scheduler） 此類創建一個Tasker for FileProcessor，並按計劃的時間間隔運行它。
public final class FileProcessorTasker extends TimerTask {
private static Long timeInterval = 5000l;
@Override
public void run() {
FileProcessor.getInstance().run();
}
public static void start() {
TimerTask timerTask = new FileProcessorTasker();
Timer timer = new Timer();
timer.schedule(timerTask, timeInterval, timeInterval);
}
public static void main(String[] args) {
FileProcessorTasker.start();
}
}
這兩個程序都單獨運行良好。但是當通過filesToBeProcessedQueue連接在一起時，它似乎並不奏效。 問題是FTPClientPolling創建了一個對象FileProcessor並將該文件添加到隊列中。 但FileProcessorTasker創建隊列大小爲零的另一個對象FileProcessor。這兩個不同的對象是問題。它是如何創建兩個對象，當這個類是singleton。我在單例實現中丟失了什麼？