How to configure Log4Net for use with NHibernate

NHibernate's Answers — Wed, 02 Jul 2008 07:07:52 GMT

Recently there was a question in the NHUser group about how to configure Log4Net to log the queries generated by NHibernate. First of all: you can get Log4Net here. There you also find the documentation. If you are not sure about details of the configuration shown below please refer to this documentation.

Running without Log4Net

If you only want NHibernate to log the queries it sends to the data source when running unit tests you don't have to configure Log4Net at all. It suffices to add the show_sql key to the NHibernate configuration. If you are using a separate xml file to configure NHibernate (e.g. the hibernate.cfg.xml) then its content might look similar to the one below

<?xml version="1.0" encoding="utf-8" ?>

<hibernate-configuration xmlns="urn:nhibernate-configuration-2.2">

  <session-factory>

    <property name="connection.provider">NHibernate.Connection.DriverConnectionProvider</property>

    <property name="dialect">NHibernate.Dialect.MsSql2005Dialect</property>

    <property name="connection.driver_class">NHibernate.Driver.SqlClientDriver</property>

    <property name="connection.connection_string">Server=(local);Database=NHibernateFAQ;Integrated Security=SSPI;</property>

    <property name="show_sql">true</property>

  </session-factory>

</hibernate-configuration>

Now when running any unit test that involves NHibernate the queries generated by NHibernate will be logged in the output window (be it the unit test runner of Resharper or be it the Output Window of Visual Studio when you use TestDriven).

Logging with Log4Net

If you want to use Log4Net to collect logging information generated by NHibernate you have to add the necessary configuration to the config file of your application. If you want to log to two different targets (e.g. to the console and to a file) the relevant sections in your config file might look like follows

<configuration>

...

  <configSections>

    <section name="log4net" type="log4net.Config.Log4NetConfigurationSectionHandler,log4net" />

  </configSections>

  <log4net>

    <appender name="ConsoleAppender" type="log4net.Appender.ConsoleAppender, log4net">

      <layout type="log4net.Layout.PatternLayout, log4net">

        <param name="ConversionPattern" value="%d %p %m%n" />

      </layout>

    </appender>

    <appender name="RollingFile" type="log4net.Appender.RollingFileAppender,log4net" >

      <param name="File" value="log.txt" />

      <param name="AppendToFile" value="true" />

      <param name="DatePattern" value="yyyy.MM.dd" />

      <layout type="log4net.Layout.PatternLayout,log4net">

        <conversionPattern value="%d %p %m%n" />

      </layout>

    </appender>

    <root>

      <priority value="DEBUG" />

      <appender-ref ref="ConsoleAppender" />

    </root>

...

</configuration>

Here I define that all output with a priority of at least DEBUG goes to the console.

Now I have to tell my application that I want to use Log4Net. I can do that with an assembly level attribute. That is, you have to put the following code snippet somewhere in your application (e.g. the "Global. asax" if you are building a web application)

// Configure log4net using the .config file

[assembly: log4net.Config.XmlConfigurator(Watch = true)]

having done do we can now run a first unit test that accesses the database via NHibernate. The output generated by Log4Net in the unit test runner is similar to this

2008-07-02 08:40:07,249 INFO NHibernate 2.0.0.1001 (2.0.0.1001)

2008-07-02 08:40:07,251 INFO hibernate-configuration section not found in application configuration file

2008-07-02 08:40:07,254 INFO Bytecode provider name : lcg

2008-07-02 08:40:07,257 INFO Using reflection optimizer

2008-07-02 08:40:08,515 DEBUG connection.provider=NHibernate.Connection.DriverConnectionProvider

2008-07-02 08:40:08,516 DEBUG dialect=NHibernate.Dialect.MsSql2005Dialect

2008-07-02 08:40:08,517 DEBUG connection.driver_class=NHibernate.Driver.SqlClientDriver

2008-07-02 08:40:08,517 DEBUG connection.connection_string=Server=(local);Database=NHibernateFAQ;Integrated Security=SSPI;

2008-07-02 08:40:08,518 DEBUG show_sql=false

2008-07-02 08:40:08,522 DEBUG properties: System.Collections.Generic.Dictionary`2[System.String,System.String]

2008-07-02 08:40:08,526 INFO Mapping resource: LoggingSample.Person.hbm.xml

2008-07-02 08:40:08,872 INFO Using dialect: NHibernate.Dialect.MsSql2005Dialect

2008-07-02 08:40:11,425 INFO Mapping class: LoggingSample.Person -> Person

2008-07-02 08:40:11,537 DEBUG Mapped property: Id -> Id, type: Int32

2008-07-02 08:40:11,612 DEBUG Mapped property: LastName -> LastName, type: String

2008-07-02 08:40:11,614 DEBUG Mapped property: FirstName -> FirstName, type: String

2008-07-02 08:40:11,614 DEBUG Mapped property: Birthdate -> Birthdate, type: DateTime

2008-07-02 08:40:11,632 INFO checking mappings queue

2008-07-02 08:40:11,634 INFO processing one-to-many association mappings

2008-07-02 08:40:11,634 INFO processing one-to-one association property references

2008-07-02 08:40:11,634 INFO processing foreign key constraints

2008-07-02 08:40:11,712 INFO Using dialect: NHibernate.Dialect.MsSql2005Dialect

2008-07-02 08:40:11,716 INFO Using dialect defined converter

...

2008-07-02 08:40:12,410 DEBUG Static SQL for entity: LoggingSample.Person

2008-07-02 08:40:12,411 DEBUG  Version select: SELECT Id FROM Person WHERE Id = ?

2008-07-02 08:40:12,412 DEBUG  Snapshot select: SELECT person_.Id, person_.LastName as LastName0_, person_.FirstName as FirstName0_, person_.Birthdate as Birthdate0_ FROM Person person_ WHERE person_.Id=?

...

as you can see LOADS of information.

To tune the generated logging information a little bit we can filter the output generated by NHibernate by putting the following configuration section into our config file (put them just after the root section inside the log4net node)

<logger name="NHibernate" additivity="false">

  <level value="WARN"/>

  <appender-ref ref="RollingFile" />

  <appender-ref ref="ConsoleAppender" />

</logger>

<logger name="NHibernate.SQL" additivity="false">

  <level value="ALL"/>

  <appender-ref ref="RollingFile" />

  <appender-ref ref="ConsoleAppender" />

</logger>

Obviously NHibernate defines two different loggers NHibernate and NHibernate.SQL. The first one receives all logging output that NHibernate generates where as the second one only receives the sql statements generated by NHibernate.

With the above settings in place the output generated is reduced to

2008-07-02 08:48:58,636 DEBUG select person0_.Id as Id0_,

                        person0_.LastName as LastName0_,

                        person0_.FirstName as FirstName0_,

                        person0_.Birthdate as Birthdate0_

                        from Person person0_

That's what we want. Only if we have some weird problems we need to change the priority level of the NHibernate filter to say INFO or DEBUG.

As usual you can find a demo solution here.

Enjoy

The NHibernate FAQ

How to configure Log4Net for use with NHibernate

Running without Log4Net

Logging with Log4Net

Summer of NHibernate - Screen cast series