The Logger

A small Logger System with re-usability in mind. The Logger itself is a Thread.

This Module is build to be a Singleton. Typical Logger File Path : log/2016-12-31/[23-11-59 MESZ].txt

Variables

Name	Type	Standard Value	Description	Authors Note
instance	Logger (public)	null (defined in Constructor)	singleton instance	This Module is made, with the intention in mind to be used as a Singleton.
baseFile	String	null (defined in Constructor)	prefix for every Logger File
currentWritingDir	File	null (defined in Constructor)	Path to currentWritingFile
currentWritingFile	File	null (defined in Constructor)	current writing File
BUFFER_LIST	List	new	Buffer List for Logger Entries	The list contains all the Entries that need to be made, but are not yet inserted into the currentWritingFile
dirFormatter	SimpleDateFormat	new (pattern : "yyyy-MM-dd")	Date Formatter for the Logger Directory
fileFormatter	SimpleDateFormat	new (pattern : "HH-mm-ss z")	Date Formatter for the Logger File Name
logFormatter	SimpleDateFormat	new (pattern : "yyyy-MM-dd 'at' HH:mm:ss z")	Date Formatter for the Log Entries
logDefaultDir	String	null (defined in Constructor)	log Default Directory
maxLogFileSize	int	null (defined in Constructor)	max Size the the log file is allowed to have
logTerminalOutput	boolean	null (defined in Constructor)	boolean, that decides if the Logger should output to the System.out as well
stop	boolean	false	if stop == true -> the Thread is about to stop or is already stopped	If the boolean is stop but the Thread is still running longer than a couple of seconds, then the Logger is stuck and needs to be restarted manually by shutting down the whole system and restarting it again
isWaiting	boolean	false	true if the Logger is currently waiting on new inputs
isRunning	boolean	false	true if the Thread is currently running

---

Constructor

Parameter List	Type	used for...	Authors Note
logDefaultDir	String	logDefaultDir, currentWritingDir, currentWritingFile
maxLogFileSize	int	maxLogFileSize
logTerminalOutput	boolean	logTerminalOutput

Constructor Code :

public Logger(String logDefaultDir, int maxLogFileSize, boolean logTerminalOutput) {
    this.logDefaultDir = logDefaultDir;
    this.maxLogFileSize = maxLogFileSize;
    this.logTerminalOutput = logTerminalOutput;

    this.baseFile = "LOG";

    long date = System.currentTimeMillis();
    this.currentWritingDir = new File(logDefaultDir + dirFormatter.format(date));
    this.currentWritingFile = new File(currentWritingDir + "/" + baseFile.replace(".txt", "") + "["+ fileFormatter.format(date) +"].txt");


    if (!this.currentWritingDir.exists())
        this.currentWritingDir.mkdir();

    if (!this.currentWritingFile.exists()) {
        try {
            this.currentWritingFile.createNewFile();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    if (instance == null)
        instance = this;
}

---

The "run" Method

	// every time a new Logger Entry is made, this Thread always checks
    // if the File or the Directory needs to be changed
    @Override
    public synchronized void run() {
        isRunning = true;
        do {
            try {
                // Every Day a new Directory is created
                // if a new day has started since the last time a Log Entry was made
                // the Method will update the currentWritingFile and the CurrentWritingDir
                swapToNextDayDirIfNecessary();
            } catch (IOException e) {
                e.printStackTrace();
            }
            try {
                // The max size of a logger File is defined in the constructor
                // if this limit is met by the currentWritingFile, then a new will be created in the 					currentWritingDir
                swapToNextFileIfNecessary();
            } catch (IOException e) {
                e.printStackTrace();
            }

            // here, the Logger will wait for a new Logger entry, if there is no new entry to be made
            // this waiting can be interrupted, by adding a new Log Entry, or by calling the Method 				stopThread()
            if (BUFFER_LIST.isEmpty()) {
                isWaiting = true;
                try {
                    wait();
                } catch (InterruptedException e) {
                    // kindly ignore
                }
                isWaiting = false;
                // if a new Log Entry has to be written, then it will do just that
            } else {
                try {
                    writeEntry(BUFFER_LIST.get(0));
                } catch (IOException e) {
                    e.printStackTrace();
                }
                BUFFER_LIST.remove(0);
            }

            // this can only be entered, if the method stopThread was called
            if (stop) {
                isRunning = false;
                return;
            }
            // repeat this forever, till an exception is thrown, or the Method jumps out
        } while (true);
    }

---

Public Methods

Interface Methods :

Name	Parameter list	return Value	Description	Authors Note
addLogEntry	type(LogType), TAG(String), message(String)	void	Method to add a new Log Entry
stopThread	empty	void	will stop the currently running Thread	if the boolean is stop but the Thread is still running longer than a couple of seconds, then the Logger is stuck and needs to be restarted manually by shutting down the whole system and restarting it again

Getter and Setter

Name	Parameter List	return Value	Description	Authors Note
getBUFFER_LIST	empty	List	gets the current BUFFER_LIST
setBUFFER_LIST	BUFFER_LIST(List)	void	sets the BUFFER_LIST
getCurrentWritingFile	empty	File	gives back current writing File	used for the Controller and in the Spring Class
isRunning	empty	void	true if the Thread is currently running

---

Private Methods

Name	Parameter List	return Value	Description	Authors Note
swapToNextFileIfNecessary	empty	void	Every Day a new Directory is created if a new day has started since the last time a Log Entry was made the Method will update the currentWritingFile and the CurrentWritingDir
swapToNextDayDirIfNecessary	empty	void	The max size of a logger File is defined in the constructor if this limit is met by the currentWritingFile, then a new will be created in the currentWritingDir
writeEntry	entry(LogEntry)	void	Method to write a new Entry into the currentWritingFile

---

Custom Classes

LogType

public enum LogType {
    DEBUG("[DEBUG]"),
    ERROR("[ERROR]"),
    INFO("INFO"),
    MESSAGE("[MESSAGE]");

    LogType(String s) {

    }
}

LogEntry

public class LogEntry {

    public LogType type;
    public String TAG;
    public String message;

    public LogEntry(LogType type, String TAG, String message) {
        this.type = type;
        this.TAG = TAG;
        this.message = message;
    }
}