log4j and XML content

Question

I am using log4j to log request/response XMLs sent by my application.

The problem is that the xml contents are getting logged with newlines. Any suggestions as to how to format so as to preserve the xml structure as it is received??

Following is my appender:

<appender name="xmlFileAppender" class="org.apache.log4j.RollingFileAppender">
   <param name="File" value="d:/LOG/log4j/appName_${weblogic.Name}_XMLS.log" />
   <param name="Append" value="true" />
   <rollingPolicy class="org.apache.log4j.rolling.TimeBasedRollingPolicy">
       <param name="ActiveFileName" value="d:/LOG/log4j/appName_${weblogic.Name}_XMLS.log" />
       <param name="FileNamePattern" value="d:/LOG/log4j/appName_${weblogic.Name}_XMLS.%d.log.gz" />
   </rollingPolicy>
   <layout class="org.apache.log4j.PatternLayout">
   <param name="ConversionPattern" value="[%d{DATE}][%-p][%c{3}%x][%m]%n"/>
   </layout>
</appender>

Answer 1

Your conversion pattern appends a newlines. Try changing this:

 <param name="ConversionPattern" value="[%d{DATE}][%-p][%c{3}%x][%m]%n"/>

To this:

<param name="ConversionPattern" value="[%d{DATE}][%-p][%c{3}%x][%m]"/>

because it sounds like removing the %n will do what you need. Of course, note that any log statement requiring a newline AND using this appender, would need to add it explicitly, as in: log.debug(msg + "\n"); which can be made generic, if necessary:

final String newLine = System.getProperty("line.separator");
...
log.debug(msg + newLine);

I hope that helps,

-gMale

Answer 2

gmale is right by saying that the code of omitting the newline character must exists somewhere.

However, you have to be careful; you only want to remove newlines from certain logged objects, not from all of them (collectively filtering out newlines from all log calls in the system is a bit of an overkill and I'd consider it a handicap).

To achieve this, you have two options:

1. Manually invoke a method to clear newlines from the XML string before passing it to log4j, using gmale's example (however I'd replace \n with System.getProperty("line.separator") or, if you're using Commons Lang, SystemUtils.LINE_SEPARATOR).
2. Wrap your XML string with a custom object, and configure Log4J to add an ObjectRenderer that will render your custom object into a String.

Any of these two ways will result in newlines being removed from exactly the type(s) of content you want, rather than collectively for all logging on the planet.