最近公司项目里需要使用到将所有执行的sql打出日志，放在一个文件下。公司一大神级人物给解决了，刚刚花了点时间给研究了一下。
他用的就是p6spy，其实也没做多少工作。主要的工作p6spy都已经做过了。
p6spy我的理解就是：p6spy将应用的数据源给劫持了，应用操作数据库其实在调用p6spy的数据源，p6spy劫持到需要执行的sql或者hql之类的语句之后，他自己去调用一个realDatasource，再去操作数据库，只要劫持到那些sql之后，能干的事情就很多了。
p6spy 可以输出日志到文件中、控制台、或者传递给 Log4j，而且还能配搭 SQL Profiler 或 IronTrackSQL 图形化监控 SQL 语句，监测到哪些语句的执行是耗时的，逐个优化。关于与 SQL Profiler 或 IronTrackSQL 的配合使用可参数文件的链接。
p6spy在sourceforge上下载：http://sourceforge.net/projects/p6spy/?source=dlp
p6spy的配置：
第一：p6spy.jar放入应用的classpath下
第二：修改连接池或者连接配置的jdbc的驱动为p6spy所提供的驱动，com.p6spy.engine.spy.P6SpyDriver
在单独的Hibernate的应用中，数据库驱动配置在hibernate.cfg.xml里面,所以我需要配置文件中的connection.driver_class属性从oracle.jdbc.driver.OracleDriver改为com.p6spy.engine.spy.P6SpyDriver其他的用户名密码等等配置信息全部不用修改.在web程序中，配置的连接池部分，也只需要修改jdbc-driver的配置即可。
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Hibernate.cfg.xml:
com.p6spy.engine.spy.P6SpyDriver jdbc:oracle:thin:@localhost:1521:orcl scott tiger 1 org.hibernate.dialect.Oracle9Dialect thread org.hibernate.cache.NoCacheProvider true false 0 第三： 修改 spy.properties 并将其放到classpath下：
（文件内容太多了，仅附上几处重要的）
#################################################################
# MODULES #
# #
# Modules provide the P6Spy functionality. If a module, such #
# as module_log is commented out, that functionality will not #
# be available. If it is not commented out (if it is active), #
# the functionality will be active. #
# #
# Values set in Modules cannot be reloaded using the #
# reloadproperties variable. Once they are loaded, they remain #
# in memory until the application is restarted. #
# #
#################################################################
#第一：module.log的属性必须配置，如果不配置，P6SPY将不起任何作用，典型配置：
module.log=com.p6spy.engine.logging.P6LogFactory
#module.outage=com.p6spy.engine.outage.P6OutageFactory
#################################################################
# REALDRIVER(s) #
# #
# In your application server configuration file you replace the #
# "real driver" name with com.p6spy.engine.P6SpyDriver. This is #
# where you put the name of your real driver P6Spy can find and #
# register your real driver to do the database work. #
# #
# If your application uses several drivers specify them in #
# realdriver2, realdriver3\. See the documentation for more #
# details. #
# #
# Values set in REALDRIVER(s) cannot be reloaded using the #
# reloadproperties variable. Once they are loaded, they remain #
# in memory until the application is restarted. #
# #
#################################################################
#第二：数据库驱动配置，你懂的，不多说了
# oracle driver
# realdriver=oracle.jdbc.driver.OracleDriver
# mysql Connector/J driver
# realdriver=com.mysql.jdbc.Driver
# informix driver
# realdriver=com.informix.jdbc.IfxDriver
# ibm db2 driver
# realdriver=COM.ibm.db2.jdbc.net.DB2Driver
# the mysql open source driver
realdriver=org.gjt.mm.mysql.Driver
#specifies another driver to use
realdriver2=
#specifies a third driver to use
realdriver3=
#第三：appender配置，一般分为三种
#specifies the appender to use for logging
#appender=com.p6spy.engine.logging.appender.Log4jLogger
#控制台
#appender=com.p6spy.engine.logging.appender.StdoutLogger
appender=com.p6spy.engine.logging.appender.FileLogger
# name of logfile to use, note Windows users should make sure to use forward slashes in their pathname (e:/test/spy.log) (used for file logger only)
#日志文件存放路径及文件名
logfile = spy.log
# append to the p6spy log file. if this is set to false the
# log file is truncated every time. (file logger only)
append=true
#The following are for log4j logging only
log4j.appender.STDOUT=org.apache.log4j.ConsoleAppender
log4j.appender.STDOUT.layout=org.apache.log4j.PatternLayout
log4j.appender.STDOUT.layout.ConversionPattern=p6spy - %m%n
log4j.logger.p6spy=INFO,STDOUT
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总结：配置很easy，使用很easy，功能很strong！