使用多个logger时，所有logger的配置写在一个配置文件里面

两个例子：

1 一个继承的例子（http://logging.apache.org/log4cxx/）

//  file com/foo/bar.h
#include "log4cxx/logger.h"namespace com {namespace foo {class Bar {static log4cxx::LoggerPtr logger;public:void doIt();}}
}

// file bar.cpp
#include "com/foo/bar.h"using namespace com::foo;
using namespace log4cxx;LoggerPtr Bar::logger(Logger::getLogger("com.foo.bar"));void Bar::doIt() {LOG4CXX_DEBUG(logger, "Did it again!")
}

log4j.rootLogger=DEBUG, A1
log4j.appender.A1=org.apache.log4j.ConsoleAppender
log4j.appender.A1.layout=org.apache.log4j.PatternLayout# Print the date in ISO 8601 format
log4j.appender.A1.layout.ConversionPattern=%d [%t] %-5p %c - %m%n# Print only messages of level WARN or above in the package com.foo.
log4j.logger.com.foo=WARN

// file MyApp2.cpp#include "com/foo/bar.h"
using namespace com::foo;// include log4cxx header files.
#include "log4cxx/logger.h"
#include "log4cxx/basicconfigurator.h"
#include "log4cxx/propertyconfigurator.h"
#include "log4cxx/helpers/exception.h"using namespace log4cxx;
using namespace log4cxx::helpers;
// Define a static logger variable so that it references the
// Logger instance named "MyApp".
LoggerPtr logger(Logger::getLogger("MyApp"));int main(int argc, char **argv)
{int result = EXIT_SUCCESS;try{if (argc > 1){// BasicConfigurator replaced with PropertyConfigurator.PropertyConfigurator::configure(argv[1]);}else{BasicConfigurator::configure();}LOG4CXX_INFO(logger, "Entering application.")Bar barbar.doIt();LOG4CXX_INFO(logger, "Exiting application.")}catch(Exception&){result = EXIT_FAILURE;}return result;
}

The output of MyApp configured with this file is shown below.

2000-09-07 14:07:41,508 [12345] INFO  MyApp - Entering application.
2000-09-07 14:07:41,529 [12345] INFO  MyApp - Exiting application.

2 使用多个logger

前置知识

• log4cxx可以使用配置文件进行设置，并且其设置方式与log4j兼容；
• log4cxx库对日志流设置，只需更改配置文件中的appender属性；
• log4cxx支持Logger继承机制，默认会继承父Logger的appender，由于要将日志流输出到多个文件中，因此需要将子Logger的继承属性设置为false.

配置子Logger

为了最大程度的灵活性，log4cxx引入了子Logger这个概念，即拥有与父Logger不同的行为，和编程语言中的OOP概念一致。

下面是在配置文件中定义一个子Logger的代码，其中ap0是logger0使用的appender：

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1. log4j.logger.logger0 = TRACE, ap0

设置子Logger不继承父Logger的appender：

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1. log4j.additivity.logger0=false

设置子Logger所使用的日志文件，下述代码将logger0的日志文件设定为当前程序目录下的0.log：

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1. log4j.appender.ap0.File=./0.log

在程序中获取子Logger实例

首先是加载配置文件：

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1. log4cxx::PropertyConfigurator::configure(配置文件名称);

获取子Logger实例：

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1. log4cxx::LoggerPtr logger = log4cxx::Logger::getLogger(子Logger名[例如上文中的"logger0"]);

FreeJudger项目中使用的完整配置文件

下述代码配置了8个子Logger，用于FreeJudger项目中判题线程的日志：

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1. log4j.additivity.gather = false
2. log4j.rootLogger=TRACE
3. log4j.logger.logger0 = TRACE, ap0
4. log4j.logger.logger1 = TRACE, ap1
5. log4j.logger.logger2 = TRACE, ap2
6. log4j.logger.logger3 = TRACE, ap3
7. log4j.logger.logger4 = TRACE, ap4
8. log4j.logger.logger5 = TRACE, ap5
9. log4j.logger.logger6 = TRACE, ap6
10. log4j.logger.logger7 = TRACE, ap7
11. log4j.logger.logger8 = TRACE, ap8
12. log4j.additivity.logger0=false
13. log4j.additivity.logger1=false
14. log4j.additivity.logger2=false
15. log4j.additivity.logger3=false
16. log4j.additivity.logger4=false
17. log4j.additivity.logger5=false
18. log4j.additivity.logger6=false
19. log4j.additivity.logger7=false
20. log4j.additivity.logger8=false
21. log4j.appender.logfile.encoding=UTF-8
22. log4j.appender.stdout=org.apache.log4j.ConsoleAppender
23. log4j.appender.stdout.layout=org.apache.log4j.PatternLayout
24. log4j.appender.stdout.layout.ConversionPattern=%5p [%t] (%F:%L) - %m%n
25. log4j.appender.R.MaxFileSize=100KB
26. log4j.appender.ap0=org.apache.log4j.RollingFileAppender
27. log4j.appender.ap0.ImmediateFlush=true
28. log4j.appender.ap0.File=./0.log
29. log4j.appender.ap0.MaxBackupIndex=10
30. log4j.appender.ap0.layout=org.apache.log4j.PatternLayout
31. log4j.appender.ap0.layout.ConversionPattern=%5p %d{HH:mm:ss} -- %m%n
32. log4j.appender.ap1=org.apache.log4j.RollingFileAppender
33. log4j.appender.ap1.ImmediateFlush=true
34. log4j.appender.ap1.File=./1.log
35. log4j.appender.ap1.MaxBackupIndex=10
36. log4j.appender.ap1.layout=org.apache.log4j.PatternLayout
37. log4j.appender.ap1.layout.ConversionPattern=%5p %d{HH:mm:ss} -- %m%n
38. log4j.appender.ap2=org.apache.log4j.RollingFileAppender
39. log4j.appender.ap2.ImmediateFlush=true
40. log4j.appender.ap2.File=./2.log
41. log4j.appender.ap2.MaxBackupIndex=10
42. log4j.appender.ap2.layout=org.apache.log4j.PatternLayout
43. log4j.appender.ap2.layout.ConversionPattern=%5p %d{HH:mm:ss} -- %m%n
44. log4j.appender.ap3=org.apache.log4j.RollingFileAppender
45. log4j.appender.ap3.ImmediateFlush=true
46. log4j.appender.ap3.File=./3.log
47. log4j.appender.ap3.MaxBackupIndex=10
48. log4j.appender.ap3.layout=org.apache.log4j.PatternLayout
49. log4j.appender.ap3.layout.ConversionPattern=%5p %d{HH:mm:ss} -- %m%n
50. log4j.appender.ap4=org.apache.log4j.RollingFileAppender
51. log4j.appender.ap4.ImmediateFlush=true
52. log4j.appender.ap4.File=./4.log
53. log4j.appender.ap4.MaxBackupIndex=10
54. log4j.appender.ap4.layout=org.apache.log4j.PatternLayout
55. log4j.appender.ap4.layout.ConversionPattern=%5p %d{HH:mm:ss} -- %m%n
56. log4j.appender.ap5=org.apache.log4j.RollingFileAppender
57. log4j.appender.ap5.ImmediateFlush=true
58. log4j.appender.ap5.File=./5.log
59. log4j.appender.ap5.MaxBackupIndex=10
60. log4j.appender.ap5.layout=org.apache.log4j.PatternLayout
61. log4j.appender.ap5.layout.ConversionPattern=%5p %d{HH:mm:ss} -- %m%n
62. log4j.appender.ap6=org.apache.log4j.RollingFileAppender
63. log4j.appender.ap6.ImmediateFlush=true
64. log4j.appender.ap6.File=./6.log
65. log4j.appender.ap6.MaxBackupIndex=10
66. log4j.appender.ap6.layout=org.apache.log4j.PatternLayout
67. log4j.appender.ap6.layout.ConversionPattern=%5p %d{HH:mm:ss} -- %m%n
68. log4j.appender.ap7=org.apache.log4j.RollingFileAppender
69. log4j.appender.ap7.ImmediateFlush=true
70. log4j.appender.ap7.File=./7.log
71. log4j.appender.ap7.MaxBackupIndex=10
72. log4j.appender.ap7.layout=org.apache.log4j.PatternLayout
73. log4j.appender.ap7.layout.ConversionPattern=%5p %d{HH:mm:ss} -- %m%n
74. log4j.appender.ap8=org.apache.log4j.RollingFileAppender
75. log4j.appender.ap8.ImmediateFlush=true
76. log4j.appender.ap8.File=./8.log
77. log4j.appender.ap8.MaxBackupIndex=10
78. log4j.appender.ap8.layout=org.apache.log4j.PatternLayout
79. log4j.appender.ap8.layout.ConversionPattern=%5p %d{HH:mm:ss} -- %m%n