qt 添加日志（Log4Qt）

1、下载Log4Qt 源码：https://sourceforge.net/projects/log4qt/

2、添加到工程：

3、创建一个继承QObject的单列，关键步骤是在一个名字为 LOG4QT_DECLARE_QCLASS_LOGGER的宏，这样才可以使用log4qt 否则不可使用 ，在构造函数里面加载log4qt的配置文件log4qt.conf 

*******************************qlog.h*****************************************

#ifndef QLOG_H
#define QLOG_H

#include <QObject>
#include <QMutex>
#include <QMutexLocker>
#include "log4qt/logger.h"
#include "log4qt/log4qt.h"

class QLog : public QObject
{
    Q_OBJECT
    LOG4QT_DECLARE_QCLASS_LOGGER

public:
    explicit QLog(QObject *parent = 0);
    static QLog * instance();

    virtual void debug(const QString& log){logger()->debug(log);}
    virtual void info (const QString& log){logger()->info(log);}
    virtual void warn (const QString& log){logger()->warn(log);}
    virtual void error(const QString& log){logger()->error(log);}
    virtual void fatal(const QString& log){logger()->fatal(log);}
private:
    static QAtomicPointer<QLog> _instance;
    static QMutex _mutex;
};

#endif // QLOG_H
**************************************qlog.cpp*****************************************

#include "qlog.h"
#include <QApplication>
#include "log4qt/propertyconfigurator.h"

QAtomicPointer<QLog> QLog::_instance = 0;
QMutex QLog::_mutex;

QLog::QLog(QObject *parent) : QObject(parent)
{
    QString configpath = QApplication::applicationDirPath()+"/log4qt.conf";
    Log4Qt::PropertyConfigurator::configure(configpath);
    logger()->info("start used log!!!");
}

QLog *QLog::instance()
{
#ifndef Q_ATOMIC_POINTER_TEST_AND_SET_IS_ALWAYS_NATIVE
    if(!QAtomicPointer::isTestAndSetNative())//运行时检测
        qDebug() << "Error: TestAndSetNative not supported!";
#endif
    //使用双重检测。
    /*! testAndSetOrders操作保证在原子操作前和后的的内存访问
     * 不会被重新排序。
     */
    if(_instance.testAndSetOrdered(0, 0))//第一次检测
    {
        QMutexLocker locker(&_mutex);//加互斥锁。

        _instance.testAndSetOrdered(0, new QLog);//第二次检测。
    }
    return _instance;
}
4、配置文件如下 log4qt.conf

log4j.rootLogger=info,error
log4j.additivity.org.apache=true
log4j.appender.error=Log4Qt::RollingFileAppender
log4j.appender.error.ImmediateFlush=true
log4j.appender.error.AppendFile=true
log4j.appender.error.File=log/TD.trace
log4j.appender.error.MaxFileSize=4096KB
log4j.appender.error.MaxBackupIndex=50
log4j.appender.error.layout=Log4Qt::PatternLayout
log4j.appender.error.layout.ConversionPattern=[%p] %d(%r) --> %m %n

5最简单使用如下：

    QLog::instance()->debug("debug");
    QLog::instance()->info("debug");
    QLog::instance()->warn("debug");
    QLog::instance()->error("debug");
    QLog::instance()->fatal("debug");

6.扩展使用

#ifndef DEBUG_H_
#define DEBUG_H_
#include "qlog.h"

#if 1   // 写入日志系统
// 以文件行列记录信息，非以类名对象形式
#define LOG_DEBUG(msg) QLog::instance()->debug(QString("[%1] Message:%2").arg(QString("###FILE:%1  ###LINE:%2  ###FUNC:%3").arg(__FILE__).arg(__LINE__).arg(__FUNCTION__)).arg(msg));

#define LOG_INFO(msg) QLog::instance()->info(QString("[%1] Message:%2").arg(QString("###FILE:%1  ###LINE:%2  ###FUNC:%3").arg(__FILE__).arg(__LINE__).arg(__FUNCTION__)).arg(msg));

#define LOG_WARN(msg) QLog::instance()->warn(QString("[%1] Message:%2").arg(QString("###FILE:%1  ###LINE:%2  ###FUNC:%3").arg(__FILE__).arg(__LINE__).arg(__FUNCTION__)).arg(msg));

#define LOG_ERROR(msg) QLog::instance()->error(QString("[%1] Message:%2").arg(QString("###FILE:%1  ###LINE:%2  ###FUNC:%3").arg(__FILE__).arg(__LINE__).arg(__FUNCTION__)).arg(msg));

// 以类名对象形式记录信息
#define LOG_OBJECT_DEBUG(msg) QLog::instance()->debug(QString("[%1]%2").arg(QString("%1::%2:%3").arg(this->metaObject()->className()).arg(__FUNCTION__).arg(__LINE__)).arg(msg));

#define LOG_OBJECT_INFO(msg) QLog::instance()->info(msg);

#define LOG_OBJECT_WARN(msg) QLog::instance()->warn(msg);

#define LOG_OBJECT_ERROR(msg) QLog::instance()->error(msg);

#endif

#endif

7.使用

LOG_INFO("加油中国"):