一.簡介
log4cplus是一個日志記錄的庫，目的很簡單，就是把合適的信息送到正確的位置上去。在服務器程序上使用非常方便。
開發庫下載地址可以去baidu搜一下，是開源的哦！
二.組成
Log4cplus 由4部分組成：
(1) Logger 日志模塊,程序中唯一一個必須得使用的模塊，解決了在哪里使用日志的問題
(2) Appenders 接收日志的各個設備,如控制臺、文件、網絡等。解決了輸出到哪里去的問題
(3)Layout 格式化輸出信息,解決了如何輸出的問題。
(4)Filter 過濾器，解決哪些信息需要輸出的問題，比如DEBUG，WARR,INFO等的輸出控制.
Log4cplus的主要部件關系圖如下：
三.一些簡單示例
(1) 各對象可以看下上圖理解一下，以下為 嚴格實現步驟1-6
#include <log4cplus/logger.h>
#include <log4cplus/configurator.h>
#include <iostream>
#include <log4cplus/consoleappender.h>
#include <log4cplus/layout.h>
#include <conio.h>
#include <log4cplus/helpers/sleep.h>
using namespace log4cplus;
using namespace log4cplus::helpers;
int _tmain(int argc, _TCHAR* argv[])
{
/**//* step 1: Instantiate an appender object */
SharedObjectPtr<Appender> _append (new ConsoleAppender());
_append->setName(LOG4CPLUS_TEXT("append for test"));
/**//* step 2: Instantiate a layout object */
//std::string pattern = ;
std::auto_ptr<Layout> _layout(new PatternLayout(LOG4CPLUS_TEXT("%d{%m/%d/%y %H:%M:%S} - %m [%l]%n")));
/**//* step 3: Attach the layout object to the appender */
_append->setLayout( _layout );
/**//* step 4: Instantiate a logger object */
Logger _logger = Logger::getInstance(LOG4CPLUS_TEXT("test"));
/**//* step 5: Attach the appender object to the logger */
_logger.addAppender(_append);
/**//* step 6: Set a priority for the logger */
_logger.setLogLevel(ALL_LOG_LEVEL);
/**//* log activity */
LOG4CPLUS_DEBUG(_logger, "This is the FIRST log message");
sleep(1);
LOG4CPLUS_WARN(_logger, "This is the SECOND log message");
_getch();
return 0;
}(2) 簡潔使用模式，appender輸出到屏幕
#include "stdafx.h"
#pragma comment(lib,"../bin/log4cplusD.lib")
#include <log4cplus/logger.h>
#include <log4cplus/configurator.h>
#include <iostream>
#include <log4cplus/consoleappender.h>
#include <log4cplus/layout.h>
#include <conio.h>
#include <log4cplus/helpers/sleep.h>
using namespace log4cplus;
using namespace log4cplus::helpers;
int _tmain(int argc, _TCHAR* argv[]){
/**//* step 1: Instantiate an appender object */
SharedAppenderPtr _append(new ConsoleAppender());
_append->setName(LOG4CPLUS_TEXT("append test"));
/**//* step 4: Instantiate a logger object */
Logger _logger = Logger::getInstance(LOG4CPLUS_TEXT("test"));
/**//* step 5: Attach the appender object to the logger */
_logger.addAppender(_append);
/**//* log activity */
LOG4CPLUS_DEBUG(_logger, "This is the FIRST log message");
sleep(1);
LOG4CPLUS_WARN(_logger, "This is the SECOND log message");
_getch();
return 0;
}
（3）簡潔使用模式，appender輸出到屏幕
#include "stdafx.h"
#pragma comment(lib,"../bin/log4cplusD.lib")
#include <log4cplus/logger.h>
#include <log4cplus/configurator.h>
#include <iostream>
#include <log4cplus/consoleappender.h>
#include <log4cplus/layout.h>
#include <conio.h>
#include <log4cplus/helpers/sleep.h>
using namespace log4cplus;
using namespace log4cplus::helpers;
using namespace std;
int _tmain(int argc, _TCHAR* argv[]){
/**//* step 1: Instantiate an appender object */
SharedAppenderPtr _append(new ConsoleAppender());
_append->setName(LOG4CPLUS_TEXT("append test"));
/**//* step 4: Instantiate a logger object */
Logger _logger = Logger::getInstance(LOG4CPLUS_TEXT("test"));
/**//* step 5: Attach the appender object to the logger */
_logger.addAppender(_append);
/**//* log activity */
LOG4CPLUS_TRACE(_logger, "This is" << " just a t" << "est." << std::endl) ; //不會被打印
LOG4CPLUS_DEBUG(_logger, "This is a bool: " << true);
LOG4CPLUS_INFO(_logger, "This is a char: " << 'x') ;
LOG4CPLUS_WARN(_logger, "This is a int: " << 1000) ;
LOG4CPLUS_ERROR(_logger, "This is a long(hex): " << std::hex << 100000000) ;
LOG4CPLUS_FATAL(_logger, "This is a double: " << 1.2345234234);
_getch();
return 0;
}
（4）通過loglog來控制輸出調試、警告或錯誤信息，appender輸出到屏幕。
#include "stdafx.h"
#pragma comment(lib,"../bin/log4cplusD.lib")
#include <log4cplus/logger.h>
#include <log4cplus/configurator.h>
#include <iostream>
#include <log4cplus/consoleappender.h>
#include <log4cplus/layout.h>
#include <conio.h>
#include <log4cplus/helpers/sleep.h>
#include <log4cplus/helpers/loglog.h>
using namespace log4cplus;
using namespace log4cplus::helpers;
using namespace std;
void printMsgs(void){
std::cout << "Entering printMsgs()" << std::endl;
LogLog::getLogLog()->debug(LOG4CPLUS_TEXT("This is a Debug statement"));
LogLog::getLogLog()->warn(LOG4CPLUS_TEXT("This is a Warning"));
LogLog::getLogLog()->error(LOG4CPLUS_TEXT("This is a Error"));
std::cout << "Exiting printMsgs()" << std::endl << std::endl;
}
int _tmain(int argc, _TCHAR* argv[]){
/**//*
LogLog類實現了debug, warn, error 函數用于輸出調試、警告或錯誤信息，
同時提供了兩個方法來進一步控制所輸出的信息，其中:
setInternalDebugging方法用來控制是否屏蔽輸出信息中的調試信息，當輸
入參數為false則屏蔽，缺省設置為 false。
setQuietMode方法用來控制是否屏蔽所有輸出信息，當輸入參數為true則屏蔽，
缺省設置為false。
LogLog::getLogLog()->setInternalDebugging(false);
*/
//默認級別是不打印debug信息
printMsgs();
std::cout << "Turning on debug" << std::endl;
LogLog::getLogLog()->setInternalDebugging(true);
//打開debug方式
//全部打印
printMsgs();
std::cout << "Turning on quiet mode" << std::endl;
LogLog::getLogLog()->setQuietMode(true);
//屏蔽所有輸出信息，所以不全打印各種級別信息
printMsgs();
_getch();
return 0;
}
/**//*輸入結果如下：
Entering printMsgs()
log4cplus:WARN This is a Warning
log4cplus:ERROR This is a Error
Exiting printMsgs()
Turning on debug
Entering printMsgs()
log4cplus: This is a Debug statement
log4cplus:WARN This is a Warning
log4cplus:ERROR This is a Error
Exiting printMsgs()
Turning on quiet mode
Entering printMsgs()
Exiting printMsgs()
都有個log4cplus:打頭，可以自定義修改以下部分代碼
LogLog::LogLog() : mutex(LOG4CPLUS_MUTEX_CREATE), debugEnabled(false),
quietMode(false), PREFIX( LOG4CPLUS_TEXT("log4cplus: ") ),
WARN_PREFIX( LOG4CPLUS_TEXT("log4cplus:WARN ") ),
ERR_PREFIX( LOG4CPLUS_TEXT("log4cplus:ERROR ") ){}
*/
（5）文件模式，appender輸出到文件
#include "stdafx.h"
#pragma comment(lib,"../bin/log4cplusD.lib")
#include <log4cplus/logger.h>
#include <log4cplus/fileappender.h>
#include <conio.h>
using namespace log4cplus;
int _tmain(int argc, _TCHAR* argv[]){
/**//* step 1: Instantiate an appender object */
SharedAppenderPtr _append(new FileAppender(LOG4CPLUS_TEXT("Test.log")));
_append->setName(LOG4CPLUS_TEXT("file log test"));
/**//* step 4: Instantiate a logger object */
Logger _logger = Logger::getInstance(LOG4CPLUS_TEXT("test.subtestof_filelog"));
/**//* step 5: Attach the appender object to the logger */
_logger.addAppender(_append);
/**//* log activity */
int i;
for( i = 0; i < 5; ++i )
{
LOG4CPLUS_DEBUG(_logger, "Entering loop #" << i << "End line #");
}
_getch();
}