qtwebapp::Logger Class Reference

#include <logger.h>

Inheritance diagram for qtwebapp::Logger:

Collaboration diagram for qtwebapp::Logger:

Public Member Functions
	Logger (QObject *parent)
	Logger (const QString msgFormat="{timestamp} {type} {msg}", const QString timestampFormat="yyyy-MM-dd HH:mm:ss.zzz", const QtMsgType minLevel=QtDebugMsg, const int bufferSize=0, QObject *parent=0)
virtual	~Logger ()
virtual void	log (const QtMsgType type, const QString &message, const QString &file="", const QString &function="", const int line=0)
void	installMsgHandler ()
void	setMinMessageLevel (const QtMsgType &minMsgLevel)
QtMsgType	getMinMessageLevel () const
virtual void	clear (const bool buffer=true, const bool variables=true)

Static Public Member Functions
static void	set (const QString &name, const QString &value)

Protected Member Functions
virtual void	write (const LogMessage *logMessage)

Protected Attributes
QString	msgFormat
QString	timestampFormat
QtMsgType	minLevel
int	bufferSize

Static Protected Attributes
static QMutex	mutex

Static Private Member Functions
static void	msgHandler (const QtMsgType type, const QString &message, const QString &file="", const QString &function="", const int line=0)
static void	msgHandler4 (const QtMsgType type, const char *message)

Private Attributes
QThreadStorage< QList< LogMessage * > * >	buffers

Static Private Attributes
static Logger *	defaultLogger =0
static QThreadStorage< QHash< QString, QString > * >	logVars

Detailed Description

Decorates and writes log messages to the console, stderr.

The decorator uses a predefined msgFormat string to enrich log messages with additional information (e.g. timestamp).

The msgFormat string and also the message text may contain additional variable names in the form {name} that are filled by values taken from a static thread local dictionary.

The logger keeps a configurable number of messages in a ring-buffer. A log message with a severity >= minLevel flushes the buffer, so the stored messages get written out. If the buffer is disabled, then only messages with severity >= minLevel are written out.

If you enable the buffer and use minLevel=2, then the application logs only errors together with some buffered debug messages. But as long no error occurs, nothing gets written out.

Each thread has it's own buffer.

The logger can be registered to handle messages from the static global functions qDebug(), qWarning(), qCritical() and qFatal().

See also

set() describes how to set logger variables

LogMessage for a description of the message decoration.

Warning

You should prefer a derived class, for example FileLogger, because logging to the console is less useful.

Definition at line 52 of file logger.h.

Constructor & Destructor Documentation

Logger() [1/2]

Logger::Logger

(

QObject *

parent

)

Constructor. Uses the same defaults as the other constructor.

Parameters

parent

Parent object

Definition at line 25 of file logger.cpp.

Referenced by qtwebapp::LoggerWithFile::LoggerWithFile().

    : QObject(parent),
    msgFormat("{timestamp} {type} {msg}"),
    timestampFormat("yyyy-MM-dd HH:mm:ss.zzz"),
    minLevel(QtDebugMsg),
    bufferSize(0)
    {}

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Logger() [2/2]

Logger::Logger	(	const QString	msgFormat = "{timestamp} {type} {msg}",
		const QString	timestampFormat = "yyyy-MM-dd HH:mm:ss.zzz",
		const QtMsgType	minLevel = QtDebugMsg,
		const int	bufferSize = 0,
		QObject *	parent = 0
	)

Constructor.

Parameters

msgFormat	Format of the decoration, e.g. "{timestamp} {type} thread={thread}: {msg}"
timestampFormat	Format of timestamp, e.g. "yyyy-MM-dd HH:mm:ss.zzz"
minLevel	Minimum severity that genertes an output (0=debug, 1=warning, 2=critical, 3=fatal).
bufferSize	Size of the backtrace buffer, number of messages per thread. 0=disabled.
parent	Parent object

See also

LogMessage for a description of the message decoration.

Definition at line 34 of file logger.cpp.

References bufferSize, minLevel, msgFormat, and timestampFormat.

    :QObject(parent)
{
    this->msgFormat=msgFormat;
    this->timestampFormat=timestampFormat;
    this->minLevel=minLevel;
    this->bufferSize=bufferSize;
}

~Logger()

Logger::~Logger ( )

virtual

Destructor

Definition at line 90 of file logger.cpp.

References defaultLogger.

{
    if (defaultLogger==this)
    {
#if QT_VERSION >= 0x050000
        qInstallMessageHandler(0);
#else
        qInstallMsgHandler(0);
#endif
        defaultLogger=0;
    }
}

Member Function Documentation

clear()

void Logger::clear ( const bool  buffer = true, const bool  variables = true  )

virtual

Clear the thread-local data of the current thread. This method is thread safe.

Parameters

buffer	Whether to clear the backtrace buffer
variables	Whether to clear the log variables

Reimplemented in qtwebapp::DualFileLogger, and qtwebapp::LoggerWithFile.

Definition at line 134 of file logger.cpp.

References buffers, logVars, and mutex.

Referenced by qtwebapp::LoggerWithFile::clear(), and qtwebapp::DualFileLogger::clear().

{
    mutex.lock();
    if (buffer && buffers.hasLocalData())
    {
        QList<LogMessage*>* buffer=buffers.localData();
        while (buffer && !buffer->isEmpty()) {
            LogMessage* logMessage=buffer->takeLast();
            delete logMessage;
        }
    }
    if (variables && logVars.hasLocalData())
    {
        logVars.localData()->clear();
    }
    mutex.unlock();
}

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getMinMessageLevel()

QtMsgType qtwebapp::Logger::getMinMessageLevel ( ) const

inline

Get the current message level

Definition at line 107 of file logger.h.

Referenced by qtwebapp::LoggerWithFile::getConsoleMinMessageLevelStr(), and qtwebapp::LoggerWithFile::getFileMinMessageLevelStr().

                                         {
        return minLevel;
    }

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installMsgHandler()

void Logger::installMsgHandler

(

)

Installs this logger as the default message handler, so it can be used through the global static logging functions (e.g. qDebug()).

Definition at line 111 of file logger.cpp.

References defaultLogger, and msgHandler4().

Referenced by main().

{
    defaultLogger=this;
#if QT_VERSION >= 0x050000
    qInstallMessageHandler(msgHandler5);
#else
    qInstallMsgHandler(msgHandler4);
#endif
}

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log()

void Logger::log ( const QtMsgType  type, const QString &  message, const QString &  file = "", const QString &  function = "", const int  line = 0  )

virtual

Decorate and log the message, if type>=minLevel. This method is thread safe.

Parameters

type	Message type (level)
message	Message text
file	Name of the source file where the message was generated (usually filled with the macro FILE)
function	Name of the function where the message was generated (usually filled with the macro LINE)
line	Line Number of the source file, where the message was generated (usually filles with the macro func or FUNCTION)

See also

LogMessage for a description of the message decoration.

Reimplemented in qtwebapp::DualFileLogger, and qtwebapp::LoggerWithFile.

Definition at line 153 of file logger.cpp.

References buffers, bufferSize, logVars, minLevel, mutex, and write().

Referenced by qtwebapp::LoggerWithFile::log(), qtwebapp::DualFileLogger::log(), qtwebapp::LoggerWithFile::logToFile(), and msgHandler().

{
    mutex.lock();

    // If the buffer is enabled, write the message into it
    if (bufferSize>0) {
        // Create new thread local buffer, if necessary
        if (!buffers.hasLocalData()) {
            buffers.setLocalData(new QList<LogMessage*>());
        }
        QList<LogMessage*>* buffer=buffers.localData();
        // Append the decorated log message
        LogMessage* logMessage=new LogMessage(type,message,logVars.localData(),file,function,line);
        buffer->append(logMessage);
        // Delete oldest message if the buffer became too large
        if (buffer->size()>bufferSize)
        {
            delete buffer->takeFirst();
        }
        // If the type of the message is high enough, print the whole buffer
        if (type>=minLevel) {
            while (!buffer->isEmpty())
            {
                LogMessage* logMessage=buffer->takeFirst();
                write(logMessage);
                delete logMessage;
            }
        }
    }

    // Buffer is disabled, print the message if the type is high enough
    else {
        if (type>=minLevel)
        {
            LogMessage logMessage(type,message,logVars.localData(),file,function,line);
            write(&logMessage);
        }
    }
    mutex.unlock();
}

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msgHandler()

void Logger::msgHandler ( const QtMsgType  type, const QString &  message, const QString &  file = "", const QString &  function = "", const int  line = 0  )

staticprivate

Message Handler for the global static logging functions (e.g. qDebug()). Forward calls to the default logger.

In case of a fatal message, the program will abort. Variables in the in the message are replaced by their values. This method is thread safe.

Parameters

type	Message type (level)
message	Message text
file	Name of the source file where the message was generated (usually filled with the macro FILE)
function	Name of the function where the message was generated (usually filled with the macro LINE)
line	Line Number of the source file, where the message was generated (usually filles with the macro func or FUNCTION)

Definition at line 44 of file logger.cpp.

References defaultLogger, and log().

Referenced by msgHandler4().

{
    static QMutex recursiveMutex(QMutex::Recursive);
    static QMutex nonRecursiveMutex(QMutex::NonRecursive);

    // Prevent multiple threads from calling this method simultaneoulsy.
    // But allow recursive calls, which is required to prevent a deadlock
    // if the logger itself produces an error message.
    recursiveMutex.lock();

    // Fall back to stderr when this method has been called recursively.
    if (defaultLogger && nonRecursiveMutex.tryLock())
    {
        defaultLogger->log(type, message, file, function, line);
        nonRecursiveMutex.unlock();
    }
    else
    {
        fputs(qPrintable(message),stderr);
        fflush(stderr);
    }

    // Abort the program after logging a fatal message
    if (type==QtFatalMsg)
    {
        abort();
    }

    recursiveMutex.unlock();
}

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msgHandler4()

void Logger::msgHandler4 ( const QtMsgType  type, const char *  message  )

staticprivate

Wrapper for QT version 4.

Parameters

type	Message type (level)
message	Message text

See also

msgHandler()

Definition at line 83 of file logger.cpp.

References msgHandler().

Referenced by installMsgHandler().

    {
        msgHandler(type,message);
    }

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set()

void Logger::set ( const QString &  name, const QString &  value  )

static

Sets a thread-local variable that may be used to decorate log messages. This method is thread safe.

Parameters

name	Name of the variable
value	Value of the variable

Definition at line 122 of file logger.cpp.

References logVars, and mutex.

{
    mutex.lock();
    if (!logVars.hasLocalData())
    {
        logVars.setLocalData(new QHash<QString,QString>);
    }
    logVars.localData()->insert(name,value);
    mutex.unlock();
}

setMinMessageLevel()

void qtwebapp::Logger::setMinMessageLevel ( const QtMsgType &  minMsgLevel )

inline

Sets the minimum message level on the fly

Definition at line 100 of file logger.h.

Referenced by qtwebapp::LoggerWithFile::setConsoleMinMessageLevel(), and qtwebapp::LoggerWithFile::setFileMinMessageLevel().

                                                          {
        minLevel = minMsgLevel;
    }

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write()

void Logger::write ( const LogMessage *  logMessage )

protectedvirtual

Decorate and write a log message to stderr. Override this method to provide a different output medium.

Reimplemented in qtwebapp::FileLogger.

Definition at line 104 of file logger.cpp.

References msgFormat, timestampFormat, and qtwebapp::LogMessage::toString().

Referenced by log(), and qtwebapp::FileLogger::write().

{
    fputs(qPrintable(logMessage->toString(msgFormat,timestampFormat)),stderr);
    fflush(stderr);
}

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Member Data Documentation

buffers

QThreadStorage<QList<LogMessage*>*> qtwebapp::Logger::buffers

private

Thread local backtrace buffers

Definition at line 198 of file logger.h.

Referenced by clear(), and log().

bufferSize

int qtwebapp::Logger::bufferSize

protected

Size of backtrace buffer, number of messages per thread. 0=disabled

Definition at line 139 of file logger.h.

Referenced by log(), Logger(), qtwebapp::FileLogger::refreshFileLogSettings(), and qtwebapp::FileLogger::refreshQtSettings().

defaultLogger

Logger * Logger::defaultLogger =0

staticprivate

Pointer to the default logger, used by msgHandler()

Definition at line 153 of file logger.h.

Referenced by installMsgHandler(), msgHandler(), and ~Logger().

logVars

QThreadStorage< QHash< QString, QString > * > Logger::logVars

staticprivate

Thread local variables to be used in log messages

Definition at line 195 of file logger.h.

Referenced by clear(), log(), and set().

minLevel

QtMsgType qtwebapp::Logger::minLevel

protected

Minimum level of message types that are written out

Definition at line 136 of file logger.h.

Referenced by log(), Logger(), qtwebapp::FileLogger::refreshFileLogSettings(), and qtwebapp::FileLogger::refreshQtSettings().

msgFormat

QString qtwebapp::Logger::msgFormat

protected

Format string for message decoration

Definition at line 130 of file logger.h.

Referenced by Logger(), qtwebapp::FileLogger::refreshFileLogSettings(), qtwebapp::FileLogger::refreshQtSettings(), qtwebapp::FileLogger::write(), and write().

mutex

QMutex Logger::mutex

staticprotected

Used to synchronize access of concurrent threads

Definition at line 142 of file logger.h.

Referenced by clear(), log(), qtwebapp::FileLogger::refreshSettings(), set(), and qtwebapp::FileLogger::timerEvent().

timestampFormat

QString qtwebapp::Logger::timestampFormat

protected

Format string of timestamps

Definition at line 133 of file logger.h.

Referenced by Logger(), qtwebapp::FileLogger::refreshFileLogSettings(), qtwebapp::FileLogger::refreshQtSettings(), qtwebapp::FileLogger::write(), and write().

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The documentation for this class was generated from the following files:

• logging/logger.h
• logging/logger.cpp